INTL. SYMP. ON NEW AND ADVANCED MATERIALS AND TECHNOLOGIES FOR ENERGY, ENVIRONMENT AND SUSTAINABLE DEVELOPMENT

Nanosized mixed-metal-oxide catalysts are used in various industrially relevant processes like Fischer-Tropsch synthesis or NOx removal from gases. Transition metal ions, coordinated by reducible ligands (NH₃, pyridine or urea) that make salts with oxometalate anions (MnO₄^-, CrO₄^2-, Cr₂O₇^2-), are used to prepare nano-sized mixed spinel-type metal-oxides with pre-selected composition, properties, and structure. The applicability of a mixed oxide catalyst is determined by the distribution of the two metals among valence states, and crystallographic positions (in spinels T-4 and OC-6). The methods currently used for the synthesis of mixed metal-oxides do not allow the control of these properties. This is because the methods used for synthesis of mixed metal-oxides include processes that take place at high temperatures, where the mobility of atoms leads to the formation of a thermodynamically stable structure. This stable structure is characterized by its unique distribution of metal atoms among positions and valence states. The unique feature of the catalyst synthesis method developed by us [1-4] is based on the thermal decomposition of tetraoxometalates of transition metal ions, coordinated by reducible ligands at relatively low temperatures (100-200 ^oC). The thermal decomposition of tetraoxometalates then releases gas-phase products formed from the ligands. This is a solid-phase reaction which forms mixed oxides with metastable structures because at low temperatures, the metal ions remain in the crystallographic positions of the precursor salt. For example, hexaaquairon(III) permanganate results in (Fe,Mn)O type and (Fe,Mn)₃O₄ type mixed oxides, depending on the atmosphere and temperature of decomposition. Furthermore, the original spinel structure can be oxidized into defect-spinel structures and finally to (Fe,Mn)₂O₃ type oxides.

[Fe(urea)₆(MnO₄)₃] --> (Fe,Mn)₃O₄ --> (Fe,Mn)₃O_4.5 --> (Fe,Mn)₂O₃
--> (Fe,Mn)O

Due to a large number of crystal defects, nanocrystallites are formed which is favorable for catalysis. Our method enables one to set the ratio of the metal ions arbitrarily by starting from an isomorphous solid solution in which we partially replaced the metal ion by another one, and/or the anion by another tetraoxometalate or by an "innocent" anion (which forms gaseous products due to the lack of metal atoms, e.g., MnO₄^- by ClO₄^-).
[Fe(urea)₆](MnO₄)₃ -- (Fe,Mn)-oxides with Fe:Mn=1:3 overall ratio
[Fe(urea)₆(MnO₄)₂(ClO₄)₂ -- (Fe,Mn)-oxides with Fe:Mn=1:2 overall ratio
[Fe(Urea)₆](MnO₄)(ClO₄)₂ -- (Fe,Mn)-oxides with Fe:Mn=1:1 overall ratio
[(Fe_0.5Cr_0.5)(urea)₆](MnO₄)_0.5(ClO₄)_2.5 -- (Fe,Cr,Mn) oxides with Fe:Cr:Mn=1:1:1 overall ratio

References:
[1] Sajó I.E., Bakos P. Szilágyi I.M., Lendvay Gy., Magyari J., Mohai M., Szegedi A., Farkas A., Jánosity A., Klébert Sz., Kótai L., Inorg. Chem., 2018, 57(21), 13679-13692.
[2] Kotai, L., Banerji, K. K., Sajo, I., Kristof, J., Sreedhar, B., Holly, S., Keresztury, G., Rockenbauer, A.
Helv. Chim. Acta, 2002, 85(8) 2316-2327
[3] Kotai L., Fodor J., Jakab E., Sajo I., Szabo P., Lonyi F., Valyon J., Gacs, I., Argay G., Banerji K., Trans. Metal Chem., 2006, 31(1) 30-34
[4] Sajó I. E., Kotai L., Keresztury G., Gacs I., Pokol Gy., Kristóf J., Soptrayanov B., Petrusevski V. M., Timpu D., Sharma P. K., Helv. Chim. Acta 2008, 91, 1646

As modern society's demands for energy storage technologies increases, it becomes necessary to develop new approaches to meeting the challenges of the future. One of the most promising areas of current research and development is that of sodium ion batteries (SIB) which potentially offer, in comparison to existing technologies, low cost, environmentally friendly technologies from earth abundant resources. While (SIBs) have many potential applications, they are particularly well suited to stationary storage.[1] In this work, we will offer an overview of SIB technology before exploring key advances and highlighting important factors affecting their properties. In order to do this, we will discuss SIBs in terms of their three most significant components: anodes, electrolytes, and cathodes.
SIB anodes are mainly based on hard carbon materials, due to their attractive combination of low cost and high energy density, though there has also been interest in other systems (e.g. intermetallic alloying materials and metal oxides), as well as interest in exploiting specific electrolyte co-solvation effects so as to enable the use of graphite.[2,4] The SIB research community typically uses organic electrolytes analogous to those developed for lithium ion batteries (LIBs) to exploit their analogous natures. Recently, however, there has also been increasing interest in developing new electrolytes specifically tailored to SIBs, such as optimized liquid and solid electrolytes.[5,6] At the present time, cathodes are one of the most explored (SIB) components - with a plethora of options to choose from, including prussian blue and organic materials. The most promising, however, are polyanionic and layered materials because of their good combinations of electrochemical performance, low cost, stability and available constituents.[1,7,8]
Although interest in SIB technology is only relatively new, when compared to LIBs it has been already developed at the prototyping and demonstrators' levels. A general overview of the most interesting electrode and electrolyte materials for Na-ion batteries - with a strong focus on those related to the current prototypes - will be presented. By examining this topic in detail, we will demonstrate the considerable potential of this new technology, and highlight some of the most promising opportunities for developing new and improved SIB technologies.

Landfill sites are on the rise and are competing for a spot on Earth whose population is rapidly growing. The dangerous gasses released from the landfills, in addition to other pollutants in the air and water, are “responsible” for the scary statistics reporting that 3 % of the deaths worldwide are due to drinking polluted water, while 7 million deaths each year are due to the air pollution (WHO, 2013).
The PoSH™ (Porous Shells and Husks) project offers a great potential to give a “second chance” to the waste by utilizing it for a good cause and contributing towards a cleaner world. Various types of waste materials disposed from households, restaurants, farms and industries were tested for their efficiency to adsorb environmental pollutants, viz. heavy metals – lead, nickel, zinc, copper and others. These waste materials are collectively referred to as PoSH™ materials here and include such materials as egg shells, peanut husks, rice husks, corn cobs and husks, nut shells, peels and many others.
The findings showed that, without any prior treatment, most of the tested waste efficiently adsorbs heavy metals from contaminated water. Most of the agricultural waste adsorbed more than 70% of the present pollutants within an hour of contact with the contaminated water. The effects of contact time, surface area of the adsorbent and concentration of the sorption efficacy of the waste material toward heavy metals were investigated, as well.
The project is in progress and it is expected to have a huge impact on increasing public awareness for re-using waste before it is thrown and decomposed in landfills.
The project is supported by the Virginia Tech (VT) National Center for Earth and Environmental Nanotechnology Infrastructure (NanoEarth), a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is in turn supported by NSF (ECCS 1542100). The support by CSI: Create. Solve. Innovate. LLC is also appreciated.

Every year in the world, millions of tons of harvest residues are generated, such as, corn stalks and corn cob blanks, wheat, soy and rice straw, sunflowers, and rice husk. Those harvest residues can be used as a replacement for fossil fuels and represents a renewable energy source. Ash, which is generated by combustion of harvest residues, is usually deposited in landfills, causing environmental pollution and potential human health risks. These risks are caused by non-existent bio-ash management and the absence of pollution control [1]. In order to promote biomass as an energy source, the available quantities of agricultural biomass in Croatia and Serbia are presented. Its heating power is determined and compared to the heating power of standard energy sources. The possibilities of using biomass ash as a waste material in the building industry are outlined. As presented in [2-4], different kind of biomass ashes can be successfully used to replace cement in mortars and concrete and have positive influence on geotechnical properties of the soil. Preliminary results of ash suggest that these ashes exhibit the potential for use in the building industry, but because of the differences in their characteristics, each of them needs to be investigated in more detail.

Nontoxic flexible solar cells are by far the best candidates for meeting the ever-growing energy consumption demand of wearable devices, portable electronics, and the Internet of Things, while the output of solar cells is intrinsically restricted by the fluctuation of sunlight from ambient factors such as weather and day-night cycle. Self-powered integrated energy devices consisting of photovoltaic cells and energy storage units can serve as sustainable and portable distributed power sources that simultaneously generate and store electric energy without the need for external charging circuits and wires.
Previously, we have developed ultra-flexible organic photovoltaics (OPVs) with a total thickness of a few micrometers that could realize superior mechanical stretchability and environmental stability (water, heat, light et al.) while maintaining high power conversion efficiency (over 10%). With this ultra-thin OPVs as direct power sources that can be well attached onto objects, we have successfully developed self-powered ultra-flexible electronic devices that can precisely measure biometric signals on skin or other tissues. To further extent the application of such kind of solar cells in wearable electronics, a compatible energy storage units is needed to ensure a stable power supply.
However, the complexity of power management, device compatibility design and materials engineering optimization in the flexible integrated device results in low total conversion and storage efficiency (~2%), large device thickness (~mm) and poor operation stability. In this talk, we will report an efficient, ultra-thin, and flexible self-powered system integrating OPVs with supercapacitors that addresses the above issues. Introducing carbon nanotubes content into conducting polymers along with a chemical treatment yields dramatically increased electrode surface area, decreased charge-transfer resistances, and enhanced mechanical robustness, thus improving the specific capacities of supercapacitors, reducing the device thickness into a few tens of micrometers while maintaining excellent stability. Through the optimization of carbon nanotube-polymer composite electrodes, high total energy conversion and storage efficiency has been achieved in the long-term stable ultra-flexible integrated devices.

Non-thermal plasma (NTP), also referred to as a cold plasma, is a unique tool with different applications where the temperature of electrons typically ranges from 10000 K to 250000 K while the hot gas exists at room temperature. These highly energetic electrons produce free radicals from parent molecules in multi-step physical and chemical processes, leading to high destructive ability. NTP is currently applied in different applications such as health sectors, environmental remediation, removal of volatile organic pollutants, simultaneous removal of NOx and soot in diesel exhaust and sterilization of air and water. Plasma jets, a category of NTP which can deliver plasma up to a few meters distance, are unique in producing reactive chemistry at room temperature. Therefore, it has attracted much attention in different applications due to their versatility and low-cost operation. Jet plasma has a privilege of lower shock risk, compared with DBD and corona discharge, which can penetrate and propagate inside small holes and flexible dielectric tubes. This is quite useful in different applications. In this sense, we developed a flying jet plasma torch (FJPT) and used it as an impetus in wide spectrum research. Those were dedicated to investigate FJPT as a sole and assisting catalyzing agent for: (1) Biodiesel production from fresh and wasted vegetable oil; (2) Treatment of domestic wastewater; (3) Treatment of raw polymers (polypropylene, polystyrene, and polyethylene) before end use process; (4) Activation of carbon derived from peat soil towards simple way of carbon nano tubes production; (5) Application of jet plasma in health sector (inactivation of wide range pathogens). Recent researches were devoted to utilizing our developed FJPT on: regeneration of reforming spent catalysts, treatment and conversion of land fill leachate towards biofuel production, and production of methanol from wasted steam plasmolysis. So far, a bunch of results of the aforementioned researches were published in refereed journals, while others will be in the near future.

Significant enhancement of properties may be achieved through hybrid materials produced by newly emerging techniques of shear mixing [1]. It was shown that properties obtained by severe plastic co-deformation of dissimilar metallic materials are far outside of the expected properties of composite materials due to several physical phenomena observed, such as extension of solid solubility in immiscible metals, formation of non-equilibrium phases and reduction of grain size to a range of 10-20 nm near the interface. This level of nanostructuring that is accessible in hybrid materials is shown to be unreachable in single constituent materials.
The idea of manufacturing material hybrids with simultaneous nanostructuring by SPD to reach new levels of properties is quite appealing. The architecture of hybrid materials is based not only on the design of the constituents and their volume fraction, but also on optimisation of the width and composition of the interface zone. Moreover, the understanding of physical mechanisms involved in interface formation and triggered by severe shear deformation under hydrostatic pressure is crucial for the architecture of hybrid materials with enhanced properties.
One of the important factors for lightweight application examples is focused on shear-assisted interface formation in composite sheets of Interstitial-Free steel with Al or Cu interlayers [2, 3].
Al-IF steel and Cu-IF steel, multilayered composite sheets with different volume fractions of aluminium or copper, were produced by accumulative roll bonding (ARB) and Asymmetric Accumulative Roll Bonding (AARB), the latter introducing additional shear strain. The IF steel and Al/Cu alloy sheets were stacked in a sandwich-like structure and roll-bonded by two passes with varying roll diameter ratios (dr) equal to 1 and 2 for ARB and AARB processes, respectively. This work shows the effect of shear strain on the formation of the interface zone. The interface zone thickness, formed by intermixing and diffusion, was characterised by several different techniques, such as STEM EDX line scan, HRTEM and Atom Probe. Furthermore, finite element simulations of both processes were conducted to determine the level of interfacial shear strain.
Conclusions:
- Severe Plastic Deformation (SPD) processes were shown to be a useful tool to produce hybrid materials with concurrent nano-structuring of the constituents.
- Shear strain, hydrostatic pressure and temperature of SPD processing play an important role in enhancement of the formation and properties of measurable interfaces.
- The width of the interfacial zone correlates directly with the magnitude of the shear strain and architecture of the hybrid material.
- The volume fraction and the nature of the interfaces play a decisive role in the improvement of mechanical and physical properties of a hybrid material.

Biological surfaces in nature (e.g., spider silk, cactus spine, beetle back, butterfly wing, lotus leaf, etc.) have inspired us to design functional materials and surfaces [1-5]. Inspired by the structures of spider silk for directional water collecting ability, a series of bioinspired gradient fibers has been designed by integrating fabrication methods and technologies, e.g., dip-coating, Rayleigh instability break-droplets, electrospinning, and wet-assembly, etc.. Thus, this allows roughness and curvature, gradient spindle-knots, a star-shape wettable pattern, etc. for droplet transport and harvesting. Inspired by cactus spines, the conical spines with periodic roughness or micro- and nanostructures can achieve high-efficiency condensed-droplet transport. Some dynamic gradient surfaces are also designed, e.g., photo-thermal organogel surfaces for control of droplet transport in various routes via light radiation, and magnetic-induced dynamic tilt-angle pillar array for driving of the droplet shedding-off in directions. The bioinspired gradient surfaces can be further designed to exhibit robust transport and control of droplets. These bioinspired gradient surfaces would be promising applications into anti-icing, liquid transport, anti-fogging/self-cleaning, water harvesting, etc.

Phosphorus (P) is a main element to all life forms with no synthesizable chemical or technological substitute. The already reported depletion of phosphate rock [1], together with the eutrophication problem caused by excessive loads of phosphate in water bodies [2], encourage the development of technologies that promote the recovery of this nutrient from alternative sources, such as municipal wastewater (MW). One of the most studied techniques to recover phosphate from MW is precipitation/crystallization, but it is limited by the initial nutrient concentration and the presence of coexisting ions [3]. Electrodialysis (ED), a membrane-based process that uses an electric field as the driven force, may be viable to overcome these limitations [4,5]. In this regard, the aim of the present study is to compare an ED system operating on galvanostatic and potentiostatic operational modes to remove/separate coexisting ions, such as sulfate and sodium, from phosphate ions of an already concentrated P-containing solution. Thus, we expect to obtain a solution in the concentrated compartment containing sodium and sulfate ions, and a solution retaining the phosphate ions in the diluted compartment. The experiments were carried out in a 5-compartment ED cell with Chinese heterogeneous ion-exchange membranes alternately arranged. In the potentiostatic operational mode, with an imposed potential value of 34.0 V, it was reported an average percent extraction for sodium, sulfate and phosphate ions of 99.5 %, 93.6 % and 33.8 %, respectively. For the galvanostatic operational mode, with an applied current density of 25.0 mA cm-2 (125 % of the limiting current density), the respectively average percent extraction observed for sodium, sulfate and phosphate ions was 97.7 %, 94.2 % and 18.7 %. It can be noted that both methods of operation presented a similar removal of sodium and sulfate ions, but more phosphate ions are transferred to the concentrated compartment in the potentiostatic mode compared to the galvanostatic one, which is an unwanted behavior. In this bias, it can be concluded that operating the ED system in a constant current density is a more suitable condition to achieve the objective of the study.

The method of stage vacant place and subsequent filling has been used in an iron mine in Anhui province, but the effect of underground filling with local cement is not good. Therefore, the cementitious material was developed which suitable for the actual situation of the mine. In this paper, the basic properties, fluidity of filling slurry and strength of filling body between local cement and cementitious materials are compared and studied. The experimental results show that the diffusion of filling slurry with new cementitious material is higher 37.93% than the filling slurry with local cement, and the compressive strength of filling body is higher 75.82% than the filling body with local cement. The testing indexes of the new cementitious material are better than the local cement. Therefore, the new cementitious material for mining can be well adapted to the cemented filling of tailings in this mine. Through the comparative experimental study in this paper, the data support and theoretical basis of performance evaluation and industrial application are provided for mine filling cementitious materials.

The durability of building materials is an important factor in extending their lifetime, which is one of the fundamental objectives for sustainable development in the construction industry. Although cement materials are considered to be relatively resistant, there are still a number of chemical, physical or biological agents that can disrupt their structure and even their functionality. In recent times, it has been a trend to use waste materials or by-products from other industries to manufacture composites. The use of such admixtures or cement replacement fulfills two objectives of sustainable development: reduction of huge amounts of waste which would most likely end up in the landfill, and secondly, it improves the parameters of the final cementitious composites, due to e.g. pozzolanic reactions.
This work deals with the study of resistance of cementitious composites with different proportions of selected waste like blast furnace slag in the range from 65 to 95% against sulphate bacterial corrosion. Long-term bacterial corrosion was simulated using the sulphur oxidising bacteria Acidithiobacilus. The resistance of samples exposed to bacteria has been studied by monitoring changes in compressive strength, porosity, absorbability, as well as leachability of the most important components of composites. SEM analysis was used to investigate surface changes and DSC / TG to study the content of hydrated products.
Findings revealed that the composite with the blast furnace slag provided a better performance in aggressive bacterial environment. It was confirmed, however, that no linear correlation exists between the amount of the slag and the lower degradation changes. The sample with the 75 % of slag admixture proved the best performance regarding the resistivity against sulphate bio-corrosion.

In the present study, enhanced microwave (EMW) synthesis, where microwave radiation is coupled with reflux conditions, was used to prepare CeO₂, CeO₂-La₂O₃, and CeO₂-La₂O₃-10% Cu catalysts. Ceria has become a promising material that features high redox properties, high population of oxygen vacancies [Ovac], that are crucial for hydrocarbon catalytic reactions such as CO₂ reformation of methane (dry reforming of biogas) [1-3]. This is crucial in the sense that they contribute to coke reduction. Post synthetically, the catalyst CeO₂-La₂O₃-10% Cu was ball milled under both, wet and dry conditions. The ball milling technique is expected to further improve the oxygen vacancies and give higher efficiency for uniform multi-component mixed oxides in consideration of time and energy usage. The prepared catalysts were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Remarkably, the EMW synthesis conditions affect the crystallinity of the catalysts (XRD) and the crystal growth, generating particles with crystallite size in the ranges of ~11-19 nm. The ball-milled catalysts exhibited a smaller crystallite size ~9.5 nm (XRD), which corresponds to larger surface area (m²/g). This, in fact, enhances oxygen mobility in the ceria support lattice and yields to the formation of more O vacancies.

The increase in carbon dioxide (CO₂) emissions from burning fossil fuels is the largest contributor to global warming of anthropic origin. Nevertheless, CO₂ is a nontoxic, nonflammable, and renewable feedstock. CO₂ utilization for the production of cyclic carbonates has gained great notoriety in the last decades because it is an environmentally benign alternative to reduce CO₂ emissions. Cyclic carbonates can be used as intermediates in the synthesis of fine chemicals, as monomers in polymerization reactions and as aprotic polar solvents. Cyclic carbonate is produced by cycloaddition of CO₂ with epoxides in the presence of catalysts due to CO₂ thermodynamical stability. Currently, the exploration of efficient catalysts for CO₂ coupling reactions is still necessary to promote an efficient reaction [1]. Ionic liquids (ILs) are salts composed of organic cations and organic or inorganic anions with melting point lower than 100°C [2]. These compounds have been proposed as homogeneous catalysts. The high price of ILs, however, and the difficulty to separate ILs from reaction media represent a barrier to implement them in the industry [3]. One solution for overcoming this disadvantage is silica xerogel functionalization with ILs [4]. In this study, a series of silica xerogels functionalized with imidazolium-based ILs ([BMIM][Cl], [BMIM][NTf2], [MBMIM][NTf2], [EMIM][NTf2], [EMIM][MSO₃] and [EMIM] [CF₃SO₃]) were synthesized by sol gel method and characterized by BET, RAMAN, TGA, FESEM and TEM. The catalytic performance of these compounds for CO₂ chemical transformation into cyclic carbonates by cycloaddition of CO₂ with epoxides was investigated. All cycloaddition reactions were performed at 40 bars and 110°C during six hours in a 120 cm³ titanium reactor equipped with magnetic stirring and temperature controller. The highest yield was obtained with [BMIM][Cl] (82.6%) and [EMIM][MSO3] (91.6%), both showing 99% selectivity. These results highlight the potential of these compounds as new catalysts.

To evaluate the influence of production and distribution of food on the environment we can use the so-called a carbon footprint (CF), which is also known as a footprint. However, an ecological evaluation of particular phases and food production processes through the CF indicator, are extremely difficult due to a variety of assortments, technological processes, and complexity of environmental impact. The most important aspect in shaping a carbon footprint for an agriculture and food sector is energy consumption for production needs, transportation of raw materials, semi-finished products and finished products, as well as the type of packaging used [1, 2].
The production of 1 kWh of electricity is associated with the release of about 1000 grams of carbon dioxide into the atmosphere. About 50% of the overall greenhouse gas emission in the food sector comes from agricultural activities. Many developed countries label products to inform about the amount of carbon dioxide emission, which is emitted into the atmosphere. They use a sustainable development policy tool called CFP – Carbon Footprint of Product to draw the consumers’ attention to the issue concerning environmental protection [1].
The best method to preserve fruits and vegetables is freeze-drying. One of the ways of limiting the costs during freeze-drying is the use of production waste. The purpose of the work was to develop manufacturing technology of freeze-dried vegetable bars based on gels with hydrocolloids [3]. The scope of research included development of technology for the production barswith properly composed vegetable mixtures, assessment of the finished product properties (water activity, dry matter content, porosity, shrinkage, density, texture, colour, and organoleptic assessment), estimation energy consumption at the time of manufacturing the finished product in the aspect of sustainable development (CFP – Carbon Footprint of Products) [2, 3].
Presented research are the stage of the project BIOSTRATEG 3/343817/17/NCBR/2018 “Development of healthy food production technologies taking into consideration nutritious food waste management and carbon footprint calculation methodology”. The results of conducted research shown that production of freeze-dried vegetable bars to per unit of product, consummate of electric energy to 0.07 to 0.08 kWh per hour depending on the type of structuring substance used in the recipes of vegetable bars. It was also observed that the difference at the level of 24% in energy consumption is mainly related to the power consumption of the heating plate used for heating during the formation of hydrocolloid gels. There weren’t noticed any other differences in energy consumption during freeze-drying or blending of vegetable products based on gels. At the same time, the costs of freeze-drying account for 50% of electricity costs.
The aim, of thorough energy consumption data analysis in the field of food production and freeze-dried products, is to observe the Carbon Footprint of Products of each unit process, which is a full production cycle. This analysis is a basis for defining the theoretical framework to calculate the carbon footprint, which will be the starting point for the method of calculating the carbon footprint in the developed technology.

Exciplex-forming systems based on solid-state mixtures of electron donating and electron accepting compounds have a bright prospect to maximize the thermally activated delayed fluorescence (TADF) contribution. These systems can also achieve 100 % of theoretical internal quantum efficiency (IQE) of organic light-emitting devices (OLEDs) [1, 2]. Recently, a unique application of donor-acceptor (D-A) compounds as versatile exciplex-forming materials for simplified non-doped white organic light-emitting devices was proposed [3]. Maximum external quantum efficiency of these devices, however, did not exceed 3.15 %.
The aim of this study was to design versatile exciplex-forming materials with improved triplet energies, charge transport, and HOMO and LUMO energy levels. This is to allow for hole and electron injection required for highly efficient white electroluminescent devices, for phenoxathiine and xanthene as donors, and for six new D-A compounds based on diphenylsulfone and ditolylsulfone as acceptors and phenothiazines. To study the potential of these compounds as versatile exciplex-forming materials, their absorption, emission spectra, excited state lifetimes and singlet-triplet energy gaps were measured for characterization of photophysical propertie. Meanwhile, cyclic voltammetry, thermogravimetric analysis, as well as differential scanning calorimetry measurements were performed for probing of electrochemical and thermal properties. Photoelectron emission spectrometry was used for characterization of charge-injection properties of the studied compounds in their solid state. Time-of-flight measurements were used for estimation of charge-transporting properties. The results obtained are discussed with the support of theoretical calculations. Two compounds showed ability to form blue and orange exciplexes in solid-state mixtures with tris(4-carbazolyl-9-ylphenyl)amine or 4”-tris[phenyl(m-tolyl)amino]triphenylamine, respectively. For blue and orange monochromatic OLEDs prepared using the best TADF exciplex-forming materials, maximum external quantum efficiencies of 10% and 12% were achieved, respectively. An approach exploiting the structure of blue exciplex/spacer/orange exciplex was developed for white all-exciplex based electroluminescence, reaching maximum external quantum efficiency of 10 %. This research was funded by the European Regional Development Fund according to the supported activity "Research Projects Implemented by World-class Researcher Groups’ under Measure No. 01.2.2-LMT-K-718.

Molecular materials containing donor and acceptor moieties recently synthesized at the laboratories of the presenting author, and applied in organic light emitting diodes (OLEDs) as emitters and hosts will be reported.
The derivative of 3-(trifluoromethyl)benzonitrile and 3,3' -bicarbazole was found to exhibit both delayed fluorescence and exciplex-forming properties [1]. Warm-white OLED based on this material showed external quantum efficiency (EQE) of ca. 20 %.
The derivative of acridan and dicyanobenzene was found to be an efficient emitter, exhibiting both thermally activated delayed fluorescence (TADF) and aggregation induced emission enhancement. Green OLED fabricated using this emitter exhibited maximum current, power efficiency and EQE of 68 cd/m², 62 lm/W and 22.5 %, respectively [2].
A series of carbazole-quinoxaline-carbazole derivatives exhibiting TADF and mechanochromic luminescence properties were synthesized and studied. Green-blue to green-yellow TADF OLEDs fabricated by solution processing demonstrated EQE up to 10.9% and luminance of 16760 cd m^-2 [3].
Deep-blue OLED based on triplet-triplet annihilation with EQE of 14.1% was fabricated [4]. This was done by utilization of the derivatives cyanophenyl and ditertbutylcarbazolyl which were substituted with triphenylbenzene and different substitution patterns as hosts and guests of the emissive layer.
This research was funded by the European Social Fund according to the activity "Improvement of researchers" qualification by implementing world-class R&D projects of Measure No. 09.3.3-LMT-K-712.

The presentation will address recent developments related to elemental 2-D materials beyond graphene, with a focus on silicene, germanene, and arsenene. Several examples will be discussed in order to illustrate how computational theory based on first-principles calculations can contribute to the understanding of basic physical and chemical phenomena in 2-D condensed matter. Silicene is of particular interest due to its compatibility with established Si technology. Regrettably, strong interaction with common substrates eliminates the Dirac states. Alternative substrates will be analyzed and the effects on silicene will be evaluated with respect to technological requirements. Germanene attracts more and more attention because the effects of spin-orbit coupling are accessible in contrast to lighter 2-D materials. While the same is true for arsenene, the material's strongly buckled structure is not compatible with Dirac physics. Recovering the sp² bonding, on the other hand, makes it possible to realize unusual properties.

The objectives of this work are: to study the evolution of the microstructure of four face-centered cubic metals (Ag, Cu, Ni and Al) after friction in lubricated conditions, to evaluate the effect of stacking fault energy (SFE) on grain size and wear loss [1, 2].
Methods: The deformed microstructures after friction were carefully examined with a field emission scanning electron microscope. Cross sectional transmission electron microscopy. (TEM) lamellae were prepared using a focused ion beam (FIB).
Results: Deformation twinning followed by a limited recovery within the surface of Ag led to the formation of relatively thick top layer of ultrafine equiaxial grains. Thermally activated processes for the rearrangement and annihilation of dislocations are accelerated during friction of Cu and Ni due to middle and high SFE and relatively high contact temperature. Steady state values of grain size, ds, and hardness, Hs, during friction are explained by the balance between hardening and dynamic recovery in surface layers, and they strongly depend on the SFE and temperature.
Conclusions: The best wear properties of fcc studied metals are determined by high strength and ductility of surface layers during friction.

High Entropy Alloys are characterized with specific properties, including high hardness, wear-resistance, high strength, structural stability, corrosion and oxidation-resistance [1-5]. The complex of desired properties defines the increasing interest for the application in different fields of engineering. In spite of the interest towards High Entropy Alloys/materials, most of the traditional methods do not allow the fabrication the desired varieties of composites due to the technological limitation. On the other hand, investigations towards high entropy materials are increasing as there are some properties that have to be studied and validated in multi-component systems.
The goal of the current investigations is to carry out experiments and define synthesis regimes for Ti-Ni-Fe-W-Cu system powders by mechanical alloying and establish the technological parameters for the formation of High Entropy Alloys. The other goal of the work is to make experimental investigations for the synthesis of bulk materials by an explosive consolidation technique.
The paper describes the preliminary theoretical investigations and initial experimental results of mechanical alloying and explosive compaction of the Ti-Ni-Fe-W-Cu multi-component system.
As a result, the preliminary investigations establish the technological parameters for mechanical alloying. The blend with different percentages of content of powders was prepared. The high energetic planetary ball mill was used for blend processing, mechanical alloying, and amorphization ultrafine/nanopowder production. The time of processing varied in the range of 1-28 h. Selected Ball milled blends were compacted by explosive consolidation technology. For shock wave generation, the industrial explosives and new explosives obtained from decommissioned weapons were used in the experiments. The technological parameters of the explosive consolidation have been studied and are discussed in this paper.

The use of heavy oils as fuel is becoming less favorable due to the environmental concerns associated with them, and thus, it is highly recommended to convert them into lighter high-value products. An important process in the conversion of such fuels is hydro-cracking, a process by which heavy chemicals are converted into lighter and added value products [1]. The development of zeolites as catalysts in hydrocracking has caused a major breakthrough due to their superior activity, stability, and gasoline selectivity as compared to amorphous silica-alumina catalysts [2]. Y-type zeolites with uniform crystal pore sizes and strong Brønsted acidity arising from the bridging OH groups are widely used as catalysts in industrial processes such as, hydrocracking, isomerization, and alkylation [3]. Nonetheless, carbon-zeolite composites seem to be interesting catalysts for hydrocracking in which the zeolite serves as a support for metal nanoparticles and provides an acidic cracking function. Meanwhile, the CNTs and graphene provide high thermal stability and conductivity, as well as a large specific surface area.
To further increase the performance of existing hydrocracking catalysts, we demonstrate a novel approach for the synthesis of hybrid catalysts composed of Y-type zeolite, nickel nanoparticles and nano-carbon material (CNTs, Graphene). The zeolites, having a SiO₂/Al₂O₃ ratio of 30, were loaded with Ni, in 5 wt. %, using the wet impregnation method, and were hyberdized with CNTs. Despite their unique properties of high surface area and thermal conductivity, CNTs shall also add mesoporosity to the microporous zeolites, forming a hierarchical porous material. The synthesized catalyst was later tested for heptane hydrocracking at two different temperatures, 350°C and 400°C for 20 hours of time-on-stream.

MAX phases of Ti-Al-C system are the most examined and perspective for high temperature applications; they are light, electro conductive, having high damping and low friction abilities, etc. But despite the combination of unique properties they did not find yet wide spread application (it is difficult to synthesize single phased material, they should combine a set of properties and even the singlephased materials can have very different characteristics because of synthesis parameters) [1].
The bulk Ti₂AlC, Ti₃AlC₂ and (Ti,Nb)₃AlC₂ developed by us are promising for the manufacture of interconnects of solid hydrogen fuel cells, pantograph, as damping substrates under the incisors, and others. The films with an approximate stoichiometry of Ti^3.3-3.9AlC_1.4-1.6 (5 I�m thick) deposited on Ti substrate using a vacuum-arc method from the hota�� pressed target (Ti₂AlC (57 wt.%) +Ti₃AlC₂ (43 wt.%)) were extremely promising for high-temperature applications, in particular for interconnects fuel cells and as cavitation resistant coatings on turbines. After 1000 h heating at 600 ^oC the surface electrical conductivity of the films only slightly decreased from 0.01 to 0,01-3 Ohm while the surface of pure Ti after 250 h in the same conditions totally oxidized and lost conductivity.
Investigation of the influence of H₂ for 3 - 40 h and oxidation up to 1000 h at 600 ^oC, as well as thermocycling in air up to 600 ^oC on the bending strength and mass change of Ti₃AlC₂, (Ti,Nb)₃AlC₂, Ti₂AlC showed that the highest absolute value demonstrated Ti₂AlC and it was the most stable in the oxide medium (seems due to presence of some oxygen in the structure - Ti_2.2AlC_0.9O_0.17). The bending strength of the Ti₃AlC₂ and (Ti,Nb)₃AlC₂ even increased after heating in H₂. The addition of Nb allowed increasing the stability of the MAX phase in H₂, and in air (the oxide film was twice thinner than that on the samples without Nb after 1000 h heating at 600 ^oC). The high temperature X-rays showed that Ti₂AlC was oxidized more intensive than Ti₃AlC₂ at higher temperatures (Ti₂AlC was stable up to 700- 750 ^oC and Ti₃AlC₂ - up to 1050-1100 ^oC). The most stable at thermal cycling to 1200 ^oC was a high-density material based on the MAX phase Ti₃AlC₂, obtained by two-stage technology (synthesis in vacuum with subsequent compression by hot pressing at 30 MPa). The oxidized layer of specimens contained ~100% of Ti₃AlC₂ but synthesized by one-stage hot pressing at 15-30 MPa for 10-30 min was twice thicker.
The wear of Ti₃AlC₂ materials obtained at 30 MPa according to the one- and two-stage technologies was very low (as compare to silumin), but the wear of the copper in contact with them was rather high. Significant reduction of wear of copper was achieved when the manufacturing pressure was reduced to 15 MPa: during friction in pair with copper its wear resistance in comparison with traditionally used silumin was 40 times higher, and the wear of copper was 14 times smaller (after 6 km of the way); Besides, Ti₃AlC₂ demonstrated much higher arc resistance.

In the frame of the reduction of greenhouse gases, hydrotalcite nano-catalysts become a key component in the process of the dry reforming of methane (DRM). This process is now intensely investigated, both academically and industrially. The DRM reaction leads to the production of syngas with a lower H₂/CO ratio (= 1) which is appropriate for the Fischer-Tropsch and methanol syntheses. The use of hydrotalcite at the industrial level, however, faces key issues such as the sintering of the active phase and the deactivation of catalysts by carbon deposits.
This presentation provides an understanding of the overview of the key issues of the use of hydrotalcite in the DRM process. This will be illustrated by some examples including selection of materials, catalyst synthesis, alternative materials and synthesis routes, their characterisation, performance in term of conversion efficiency, and ageing ability regarding the DRM process.
Finally, a comprehensive review of the developed materials so far and current trends in the development of material combination will be provided.

The increased concern for global warming, climate changes and rising energy prices has led to a high level of political and social motivation for energy-efficient, eco-friendly and sustainable energy production. Solar energy has the potential to play a leading role in renewable energy solutions. It addresses the energy problem from human health and environmental perspectives to economic perspectives. Moreover, solar energy is capable of satisfying both the electrical and thermal needs of industries and households by means of photovoltaic (PV) and solar thermal (ST) technologies respectively or by using hybrid photovoltaic-thermal (PVT) collectors.
Actually, PVT collectors incorporate both thermal and electrical energy generations that can be used as a cooling system for the PV system in order to enhance the electrical energy efficiency and, at the same time, produce thermal energy that can be used in other applications (e.g. for water heating, space heating, etc.). This integration of PV and thermal collectors does not only enhance PV effectiveness; it also produces more energy for a certain area than a singular PV cell or solar collector alone.
The combination of these systems offers few benefits such as:
(i) An increase of photovoltaic cell effectiveness (cooling through the solar thermal system),
(ii) A reduction in space utilisation (attractive in the case when the available roof surface is limited),
(iii) Replacement of the roofing material with the PVT system that can reduce the payback period,
(iv) Reduction of greenhouse gas emissions by utilisation of renewable energies.
PVT collectors have become an important research topic in the last four decades and have attracted many interests. Research on PVT collectors started with the main focus on increasing the PV efficiency. In this work, the authors present a few innovative steps that increase PVT efficiency as well. Namely, low soiling coating on the top cover glass of PVT assembly enables the system to have a clean surface for a longer period of time. It extends the time efficiency of this system because the top glass transmittance is not decreased over a certain time period and consequently, produces more energy compared to PVT systems that do not have such a coating. This protective coating could offer a combination of antireflective, antistatic, anti-corrosion and, in some cases, photocatalytic effects. The second innovation is related to usage of thermal conductive adhesives that bond together the PV module to the ST’s absorber. Namely, the PV backsheet is directly adhered to the Al absorber surface and the heat taken from the PV module is transferred towards the ST absorber. To enhance the heat conductivity in this system, thermally conductive dopants were used. A variety of adhesive systems were investigated and the best one was selected. Finally, ST absorbers’ pipes are protected with inner anti-corrosive coating, so the PVT system could be considered for usage in salty (corrosive) regions or in direct water-circulation systems (e.g. for pool heating).
This project is supported by the Fund of innovation and technology development of R. North Macedonia, 2018-2020.

New low cost masking coatings have been developed. These coatings are based on corrosion resistant polyurethane and acrylic-urethane priming varnishes and paints of Ukrainian manufacture (InterGasSinthez). In addition, the coatings are also based on nanopowders of polyvalent iron oxides obtained by electroerosion dispersion [1], carbon, omega spheres (based on silica and alumina), and basalt fibers demonstrating high absorption abilities (90-99%) of microwaves in a wide range of frequencies (10-70 GHz, wavelength 0,03-0,0043 m) with their reflection close to zero (-10 Db - - 23 Db or 10% -0.5%). Polymeric bases of the developed coatings are used to protect against corrosion of metal structures in all macroclimatic areas, in sea and fresh water, in saline solutions, and in oil and oil products that are resistant to ultraviolet radiation, aggressive media. They demonstrate high mechanical performance (adhesion, strength, elasticity) and long service life. The coatings can be used for painting of ships, deck structures, containers, building constructions and buildings, auto and railway transports, parts and mechanisms, etc.

In Europe, heating is responsible for the most part of the residential energy demand [1]. To reduce energy consumption, thermochemical materials (TCMs) coupled with renewable heat production (e.g. solar thermal) seem a very promising option for seasonal heat storage. Among the TCMs, salt hydrates provide the highest energy density [2], but has poor mass and heat transport properties. On the contrary, highly porous materials like zeolites present good mass and energy transfer, but have high cost and rather low energy density [3]. The coupling of a porous material and a salt hydrate would be an optimal solution to guarantee both transfer properties and energy density, provided that the cost issue is addressed.
In this work, we developed a composite TCM, based on hydrated cement for the porous matrix and on calcium chloride or magnesium sulfate as salt hydrates, that allows a significant reduction of the cost per unit energy stored.
Usually, the conditions of cement hydration are chosen to obtain a low porosity material, to provide high mechanical properties. By increasing the water-to-cement (w/c) ratio in the cement paste, however, the hydrated cement becomes highly porous. Thus, the first part of the work was to characterize cement at very high w/c ratios by density measurements, N₂ physisorption analyses, microscopy and mechanical testing.
Once the best preparation conditions for porous cement were selected, two techniques were used to prepare the composite materials: the standard impregnation method from aqueous solutions and a novel one-step technique where cement was hydrated with a concentrated solution of the chosen salt instead of distilled water.
The energy density of the composites was estimated by DSC analysis and a preliminary calorimetric characterization was performed by monitoring the temperature of the samples during hydration with liquid water. The observed temperature lift was a measure of the heat generated during the hydration step. The most interesting materials were finally characterized by equilibrium water vapor adsorption isobars.
A preliminary economic analysis, based on thermal energy cycles at a maximum temperature of 80°C and 140°C (common flat-plate or evacuated-tube solar collectors, respectively), was also performed. The price per stored kWh was calculated for literature-based materials and for the cement-based composites. The results showed a three-fold reduction of price per stored kWh with respect to zeolite-based systems [4].

Magnesium-based hydride, which is a representative metal hydride, has been studied widely as the promising solid state hydrogen storage material due to its merits of light weight, high gravimetric (7.6 wt.%) and volumetric hydrogen storage capacity (110 g/L), low cost, abundant resource and environmental friendliness. However, the high working temperature and sluggish hydrogen sorption kinetics still restrict its practical application. To solve this problem, we have improved the hydrogen storage properties of magnesium-based hydride by the process of hydriding combustion synthesis plus mechanical milling and the methods of alloying, nano-sizing, catalyzing and compositing. In this report, we will introduce our recent progress of the enhancement in hydrogen storage properties of magnesium-based hydride. In particular, the magnesium-based hydride doped by various catalysts exhibits superior hydriding/dehydriding kinetics at lowered temperatures. Hybrid catalysts, such as bimetallic catalyst, carbon supported nano metal or metal oxide shows obvious effect on the hydrogen sorption kinetics of magnesium hydride. Synergistic catalytic effect between the catalyst components has been clarified. By adding carbon supported nano-nickel catalyst, the onset desorption temperature of MgH2 can be reduced to 187 °C, which is 113 °C lower than the as-milled MgH2. Our results also demonstrate the influence of shape and size of metal-based catalysts on the MgH2 system, which is helpful for designing nanostructured catalysts with ultra-fine particle size, well-formed distribution and high activity. Moreover, the novel Mg-Ni-hydride nanoparticles with ultrahigh structural stability and hydrogen storage activity derived from microencapsulated nanoconfinement have been presented.

Research in the field of material science and engineering has had a long history and tradition in Serbia. The seminal steps were made in the early 1950s, first at the University of Belgrade and the Institute of Nuclear Sciences in Vinča, after which important contributions were made by the associates of the Institute of Technical Sciences of the Serbian Academy of Sciences and Arts. The International Institute for the Science of Sintering (IISS) is certainly one of the most beautiful examples of how a very successful international scientific organization can be formed in a small country and how it can encourage the development of this discipline. The IISS was founded in 1968 in Belgrade, and the founding conference was held in Herceg-Novi, Montenegro in 1969. It was organized by 15 scientists from around the world who all agreed to develop this area with joint forces. The IISS had the important role of bringing together scientists in this field from a variety of international institutions, taking advantage of the fact that Yugoslavia, at the time, was a rare meeting place for the scientists from the East and from the West. Today, the IISS counts 12 honorable members, 45 full members, 16 correspondent members and 33 inactive members from 20 countries from all over the globe. The IISS has organized 10 international conferences on sintering (World Round Table Conferences on Sintering, WRTCS), all at the territory of former Yugoslavia. The IISS has also organized 7 international topical symposia on sintering, only the first of which was held in Herceg-Novi in former Yugoslavia and all others were held around the world: Warsaw in 1979, New Delhi in 1983, Tokyo in 1987, Vancouver in 1991, Haiko in 1995, and New Delhi in 2000. The IISS has been also publishing its Science of Sintering Journal for 50 years now.
The Materials Research Society of Serbia (MRS-Serbia) was established in 1997 to promote multidisciplinary, goal-oriented research in material science and engineering, similarly to other MRS societies in the world. The main task and objective of MRS-Serbia is to encourage creativity in researching materials and model the evolution of this field in Serbia according to the analogous activities elsewhere in the world. MRS-Serbia has held twenty conferences so far and all of them, starting from the first one in 1995, were organized in Herceg-Novi in Montenegro. On average, 200 scientific presentations are given per conference, with more than 4 000 works being presented so far in total. This includes 500 plenary lectures by world-renowned researchers from some of the world’s most famous universities.
The research program on "Molecular Designing of Nanoparticles and Functional Materials" [1] has been conducted throughout the last ten years within this environment. Since the methods for producing nanoparticles are at the basis of advanced materials science and engineering, a particular emphasis in this program is placed on soft, eco-friendly, bottom-up and easily technologically transferable fabrication methods. The materials that are the topics of our investigation can be potentially applicable in numerous technological fields: electronics, energy-storage, sensors, optics, catalysis, and biomedicine. Research activities such as those deployed in our labs may prove to be relevant for ensuring a sustainable development of humanity in energy, health, environment, water and other global sectors [2-5].

Discovery of graphene as important materials carried out the coup in nanotechnology. Great interest to graphene testifies lots of articles, which are published monthly in the scientific literature. It seems that less attention is paid to chemical properties of carbon nanostructures. Carbon nanostructures have different functional groups that have the ability to react with various organic and inorganic compounds [1]. That is why it is possible to modify the carbon nanostructures by different compounds and then obtain organic and inorganic composites based on the above mentioned modified nanoparticles [2].
For the purpose of obtaining hard ceramic materials, graphene oxide was functionalized by organic compounds (polyvinyl alcohol (PVA), polyethylene glycol (PEG).Then, functionalized graphene oxide was added in alumina and the homogenization process was carried out in nanomill during 24 hours. Organic compounds are allocated from graphene oxide at high temperatures during sintering, leading to reduction of graphene oxide. This kind reduced graphene oxide has mostly similar properties as graphene, which have influence over the physical-mechanical properties of ceramics.
Concentration of modified graphene oxide is 1.5%w in composite. The obtained mixture is dried and then consolidated in a high temperature vacuum furnace at 1600°C under pressure at 478 kg/sm₂.
The microhardness is 15.41 GPa (loading - 200 g) of the obtained ceramic materials in Fig 1. The microhardness is 12.025 GPa of the ceramic materials obtained from pure alumina under the same conditions. Testing was carried out using the Oliver-Pharr method according to the ISO-14577 standard. We are continuing works to determine optimal concentration of modified graphene oxide and we are researching other physical-mechanical properties [3].

Roads and other trafficked areas' infrastructure start to deteriorate as far as it is opened to traffic. Thus, it has to be timely repaired and reconstructed. Any interruption to traffic by implementing repair and rehabilitation works, however, leads to users' discomfort and traffic congestion. Modular pavements, also known as precast concrete pavements, can be constructed at night; consequently, they eliminate or reduce traffic flow issues related to repairs. They consist of prefabricated concrete slabs that are transported to the construction site only after the curing period, when the desirable concrete strength is achieved and installed on a prepared foundation. The prefabrication of slabs in a plant results in better concrete quality, controlled concrete curing conditions, and wider periods for pavement construction. It also reduces time before opening to traffic, and eliminates early-age failures and material segregation which may occur during concrete or asphalt mixture transportation to the project site and laying. Despite these advantages, modular pavements are barely used in Europe. In order to enhance the usage of modular pavements in Europe, this paper focuses on the identification of the most promising modular pavement application areas and their types of selection. The most promising application areas, such as motorways and arterial streets, were identified on the basis of the conducted survey among high-qualified researchers. Low volume roads, private roads, and bicycle and pedestrian paths could be included as special application areas to modular pavements using a slightly different approach.

In recent years, the contamination of drinking water with nitrogen compounds is increasing due to the poor disposal of animal waste and excessive consumption of fertilizer. Nitrates and nitrites present in water produce serious problems for human health. Acceptable limits for nitrate, nitrite, and ammonium in drinking water were set by the World Health Organization at 50 ppm, 3 ppm and 0.5 ppm respectively [1]. The past few years have seen diverse technologies for nitrate and nitrite elimination, such as reverse osmosis, electrodialysis, ion exchange, catalytic abatement and biodenitrification. Among them, for the nitrite case, the catalytic reduction results in attraction due to easy accessibility, low investment costs, no need of additional treatment, and so on. In catalytic technology, a noble metal catalyst is used, like Pd, supported on a different massive oxide (i.e. alumina, silica Si:Al30). H₂ (g) is used as reducing agent for promoting the nitrite reduction to gaseous nitrogen. In this sense, formic acid (FA) has been considered as a way to store H₂ (g) and it could be used as a reducing agent for nitrite reduction [2]. To the best of our knowledge, there are no studies of catalytic removal of nitrite using formic acid as a reducing agent. Since this agent is suitable for the removal of nitrate, the study of this agent in nitrite removal deserves attention. The objective of this study was to investigate the behavior of formic acid as a hydrogen source in the catalytic reduction of nitrite (100 N-ppm) present in drinking or waste water.
Pd catalysts, supported on alumina, silica, and a mixture of Si:Al30, were synthesized by wet impregnation and evaluated for nitrite removal in a batch reactor. Palladium chloride (PdCl₂) was used as a precursor.
The results obtained show that in the presence of FA and without a catalyst, nitrite was 80% oxidized to nitrate. This reaction follows a chemical equilibrium between these two compounds [3]. In all tests, nitrate formation occurred. On the other side, it was found that using catalysts, the formation of nitrate is lower, in comparison with its formation without a catalyst. The catalyst which shows the best selectivity to N₂ in the same conversion rate (95%) was the one supported in alumina (55%). The nitrate selectivities obtained in the same conversion (95%) are 80%, 55%, 45% and 65% for formic acid, PdSi:Al30, alpha-Al₂O₃, PdSiO₂ respectively. Also, in the same order, the ammonium selectivities obtained in the same conversion (95%) are: 0%, 0.9%, 0% and 0%, respectively. Therefore, alpha-Al₂O₃ promotes a better selectivity to gaseous compounds, making it the most promising support among those evaluated for this reaction. The use of FA shows a promising result, which must be optimized for its future use in catalytic nitrogen removal processes.

Oxidative dehydrogenation (ODH) of light alkanes may offer a promising alternative for the production of the corresponding alkenes compared to the simple dehydrogenation. This is because ODH has the advantage of an exothermic reaction without thermodynamic limitations and with a low risk of catalyst deactivation through coking since the reaction is run in an oxidative environment. Nevertheless, the main difficulty in obtaining high alkene yields by ODH of light alkanes arises from the fact that the alkene is more reactive than the corresponding alkane, thus being prone to further oxidation to produce carbon oxides. Indeed, ODH of light alkanes proceeds through sequential (Alkane --> Alkene --> Carbon oxides) and parallel (Alkane --> Carbon oxides) oxidation steps, the secondary reactions, i.e. the deep oxidation of both alkane and alkene, being more thermodynamically favorable than the oxidative dehydrogenation. Consequently, the catalyst should significantly accelerate only the chosen sequence of elementary steps and suppress all other possible elementary steps, parallel or consecutive. Several approaches should be considered to meet this selectivity challenge: (i) using carbon dioxide as soft co-oxidant; (ii) isolation of the active-site; (iii) the decrease of the lattice oxygen reactivity and (iv) increasing the catalyst basicity. All these approaches will be illustrated with relevant examples from our own research work on this subject published in the last decade [1-10].

At present a number of modern semiconductor devices based on SiGe alloys have been created in which the latest achievements of high technologies are used. These devices might cause significant changes to networking, computing, and space technology. In the nearest future new materials based on SiGe will be able to restrict the A³B⁵ and Si technologies and firmly establish themselves in medium frequency electronics. Effective realization of these prospects requires the solution of prediction and controlling of structural state and dynamical physical –mechanical properties of new SiGe materials.
Based on these circumstances, a complex investigation of structural defects and structural-sensitive dynamic mechanical characteristics of SiGe alloys under different external impacts (deformation, radiation, thermal cycling) acquires great importance.
The investigation of defects in SiGe alloys’ bulk crystals might be successfully carried out by the IF method, which is distinguished by high sensitivity to the mechanical stress field formed in the vicinity of crystalline lattice defects. It makes possible to effectively identify defects of SiGe alloys bulk crystals, to establish mechanisms of their influence on the structural sensitive physical-mechanical and electrophysical properties. Such research will help to solve the problem of creating highly efficient semiconductor structures and devices with controllable parameters based on SiGe alloys.
The contribution of a dislocation structure in relaxation and hysteretic processes of torsion oscillations damping in SiGe alloys’ bulk crystals has been studied [1-3]. Decrease of the activation characteristics of relaxation processes of dislocation origin is shown by influence of a relatively small content of Ge (1-3 at%). Reduction by ~15 % in the microplastic deformation characteristics has been revealed at 600-650 ⁰C temperatures in Si_1-xGe_x (x≤0.02) alloys containing dislocations of 10⁴-10⁵cm^-2 densities [1]. An additional reduction of IF activation characteristics has been revealed in Si_1-xGe_x(x≤0.01) alloys doped with As or B of 10^18-10²⁰ cm³ concentration [4]. SiGe alloys are characterized by different types of dislocations with distinctly different energetic and dynamic parameters [5]-[7]. This conditions the formation of complex IF spectra related to the moving dislocations.
Relaxation maximum with activation energy ~1.4 eV was revealed at 280 °C temperature at ~1 Hz frequency in IF spectrum of p-type monocrystalline Si_0.98Ge_0.02 irradiated by gamma rays. Its relation to the radiation-induced vacancy-oxygen complexes is supposed [3].
In the present work internal friction and shear modulus temperature and amplitude dependences of the monocrystalline boron-doped Si_1-xGe_x(x≤0.05) alloys grown by Czochralski technique is studied in initial and 60Co gamma-irradiated states. In the initial samples a set of dislocation origin relaxation processes and accompanying modulus defects are revealed in a temperature interval of 400-800⁰C. It is shown that after gamma-irradiation intensity of relaxation internal friction in the vicinity of 280 ⁰C increases and simultaneously activation parameters of high temperature relaxation processes reveal clear rising. It is proposed that these changes of dynamical mechanical characteristics might be caused by a decrease of the dislocation mobility in the Cottrell atmosphere enriched by the radiation defects.

Sustainable development is a comprehensive and complex system of systems requiring multidisciplinary and interdisciplinary science and technology inputs with economic, environment and social objectives. The trade space is very wide, and the multitude of trade-offs generate considerable challenges and make it often difficult to achieve an effective balance. During the last sixty years the planet’s population has grown exponentially, from 2.5 to 7.5 billion people, and the technological progress achieved has been tremendous, especially in the industrialized countries. These trends are expected to continue, even at faster rates. All these associated technological activities in the pursuit of better living standards have created a considerable depletion of resources and pollution of land, water and air. Thus, and because most of our resources are limited, it is imperative that we achieve more with less. In broad terms, sustainable development is achieved when the present needs and challenges are met without placing in jeopardy the ability of future generations to meet their own needs and challenges. The global energy demand is expected to increase exponentially, associated with the increase in the global population. The three main reserves of fossil fuels: oil, natural gas and coal are decreasing very rapidly and will not always be available to meet the global demands soon. The continuation of fossil fuel emissions will be environmentally deleterious, and there is already a need to remediate some of the deleterious effects already sustained by the environment. Energy security has become a major and critical issue as fossil fuels are confined to a few areas in the world and their availability is controlled by political, economic and ecological factors. This means that in a short term, considerable energy efficiencies and savings must be achieved, and alternative and renewable sources of energy must be developed. To enable all these technologies considerable advances in energy storage and conversion materials and technologies such as batteries, super capacitors and fuel cells must be achieved. The transportation industry has by far the largest share of global oil consumption and is now the major producer of global greenhouse gas emissions in most industrialized countries. Mobility projections show that it is expected to triple by 2050 with associated energy use and environmental impact. Considerable achievements have recently been obtained in the development of new and advanced materials such as light weight metallic alloys, metal matrix composites, intermetallic and carbon fiber composites and hybrid materials. Nano, nano-structured and nano-hybrid materials systems and nanotechnologies have also been deployed with significant impact. In addition, component redesign using a materials and functional systems integration approach is being used resulting in considerable system improvements and energy efficiency. This resulted in their introduction in the energy, transportation and manufacturing industries in a wide variety of devices and components with considerable technological, economic, environment and social impacts.
Keywords: Transformative materials and technologies, nano,

Natural phosphors like MeWO₄, possessing high light emissions at small volumes, are considered to be a promising material for X rays and γ-scintillators. Nanostructured MeWO₄ materials are promising candidates for photoluminescence. During the past decade, unique properties of these materials such as photocatalytic activity, photochromism and electrochromism have attracted the attention of researchers.
Photoluminescence in ZnWO₄ crystals, WO₃ crystalline micropowders, as well as in LiF crystals and MgF₂ ceramics doped with tungsten trioxide, was researched at 300 K. Prepared As phosphors were not transparent in the range ≥4 eV (WO₃, ZnWO₄), or they became opaque in this range after doping with tungsten trioxide (LiF crystals, MgF₂ ceramics). Emission was excited by photons with 6>E_ph ≥ 4 eV.
The focus of these studies is on the emissions of phosphors with different types of matrices. What they have in common is that the lattices contain W-O polyhedrons.
The following was revealed:
- Spectral-kinetic characteristics of the phosphors' photoluminescence in the visible range (band at 2.6-2.7 eV) are independent of the width of the band gap (from 13 till 3.8 eV), of the lattice structure of phosphorus matrices and of the method of preparing the materials (grown in air, sintering, laser ablation).
- The emission characteristics of phosphors: spectral position of emission band, the value of long-lived time decay, the emission band FWHW and the value of the Stokes shift are similar to those in the WO₃ crystalline micropowder. It looks as if emission centers were created under UV irradiation in specific areas of phosphors with the same properties in all materials under research.
- The work deals with a hypothesis according to which the presence of the WO₃ phase in phosphor matrices defines the structure of emission centers (oxygen-depleted polyhedron W⁶⁺nO^2-) and high sensitivity to UV irradiation. The latter is due to the small width of the band gap of the WO₃ lattice (3.8 eV) compared with those in the researched phosphorus matrix lattices.
- The emission in the WO₃ material is of a recombination nature. It means that wide-gap dielectric phosphors doped with WO₃ (LiF and MgF₂), free electrons, and holes are created when E_phg in the matrices. Perhaps, in this case, photocatalytic activity, photochromic, and electrochromic properties are inherent properties of many oxides of transition metals revealed in WO₃-containing materials [1, 2].

Polyoxometalates (POMs) have received considerable attention in recent years due to their rich redox properties and potential applications in energy storage.[1] Due to their discrete nature, the use of POMs as components in energy storage devices relies on their stable combination with conductive supports.[2] Carbon nanotubes (CNTs) are stable, hollow cylinders made entirely of carbon. These nanostructured carbons are highly conductive, mechanically strong and can be functionalized.[3] By encapsulating molecular materials within CNTs, their properties can be enhanced.
This work describes the first report of the encapsulation of the Keggin [PW₁₂O₄₀]^3- and Wells-Dawson [P₂W₁₈O₆₂]^6- heteropolyanions within carbon nanotubes (CNTs), along with detailed structural, chemical and electronic characterizations. Transmission electron microscopy (TEM) confirms the presence of encapsulated POMs, as well as provides the necessary energy to perform observable chemical transformations within the CNTs. Access to POM redox properties from within the CNT upon encapsulation is described. The POM electrochemistry is shown to be stabilized across a greater range of conditions and cycles than typically possible. Using Raman spectroscopy, investigations probe the electronic coupling between the host and guest, showing electron transfer between the two.

Polypropylene based nanocomposite membrane with a self-assembled coating for seawater treatment via membrane distillation
Rajesha Kumar1, Mansour Ahmed1, Garudachari Bhadrachari1, Jibu Thomas1
1Water Research Center, Kuwait Institute for Scientific Research, P.O. Box, 24885, 13109 Safat, Kuwait, Tel: +965 97920482
* e-mail: rajeshakumar15@yahoo.com
Abstract. A novel approach of self-assembly techniques has been used for the coating of superhydrophobic layer over the microporous polypropylene (PP) support. The hydrophobic fluorinated silica nanoparticles were synthesized and isolated by reacting tetraethyl orthosilicate (TEOS) with excess heptadeca- fluoro-1,1,2,2-tetrahydrodecyl) triethoxysilane. The hydrophobic silica particles (HSP) were dispersed in the coating solution consisted of trimesoyl chloride, trimethylamine and hexane compositions. The coating layer thickness was limited to 100-150 I�m by selecting the proper compositions of the TEA and TMC. The coating layer with HSP was effectively formed over the PP support via self-assembly of the hydrolyzed TMC molecules (trimesic acid (TMA) molecules). The high dispersion of HSP particles was achieved in the coating solution consisted of TMA leading to smooth and superhydrophic membrane surfaces with a contact angle of >150A�. The porosity of the surface was well in control with an average pore size of ~0.2 I�m. The application of membranes was tested for membrane distillation application in direct contact membrane distillation (DCMD) configuration. The hot feed of 35 g/L aqueous sodium chloride solution, and cold deionized water as permeate. The maximum transmembrane permeate flux of 46.7 kg/m2h with >99% salt rejection was obtained at 80 A�C demonstrating the future potential application towards seawater desalination.
Keywords: seawater treatment, nanocomposite membrane, membrane distillation, self-assembly

Supercapacitors are the major energy providers in the varieties of biomedical and communication subsystems [1]. Polypyrrole, a well-known hole conducting polymer, has been proposed and used as bendable electrodes for different electrode applications [2]. Particularly, the material has been successfully utilized as electrodes in the flexible supercapacitors. With all the favorable features such as easy deposition, low cost, bendability, and versatility, the material has shortcomings, among which mediocre conductivity and chemical sensitivity [3] are major deterrents. The aim of the present research work is to simultaneously enhance conductivity and reduce the chemical sensitivity of the material via its alloying with other organic substances.
Thin layers of polypyrrole with different compositions are formed via chemical polymerization method [4] on glass substrates with pre-deposited interdigitated gold electrodes. During polymerization surface-sensitized substrates are immersed in a 0.01 M solution of pyrrole monomer for a few minutes at 5 ℃. A 0.05 M solution of ammonium peroxodisulfate in deionized water is added as the oxidizing agent while continuously stirring. The process time is calibrated for achieving a polypyrrole thickness of 120 nm on the substrate. The alloying components, anthraquinone-2-sulfonic acid sodium salt monohydrate-5-sulfosalicylic acid dehydrate and α-naphthalene sulfonic acid, are introduced as 0.5 M solution of the respective component to the polymerization reactor.
The morphology of the produced layers are examined with plan view and cross-sectional FESEM. The surface quality of the samples is also examined with AFM. Conductivity measurements are carried out by forming diffusion bonded metallic contacts [5] to the double electrodes underneath the layer. These measurements are repeated in clean and ammonia-contaminated air atmospheres. The results indicate that alloying with α-NSA simultaneously increases the conductivity and decreases the pollution sensitivities of the polypyrrole layers.
The electrical conductivity changes in polypyrrole layers due to the addition of AQSANa-SSCA and α-NSA are reported for the first time. These additives decrease the sensitivity to the pollutants examined.

Fused, ladder-type organic materials have inherent advantages, such as extended Pi-frameworks, favorable stacking behavior in the solid state, conductivity, and high field-effect mobility. We have reported a wide range of quinoxalinophenanthrophenazine (TQPP) compounds. The introduction of nitrogen atoms in the TQPP core decreases the HOMO-LUMO gap, making the compounds of more interest in electronic applications. Besides, the planarity of the core in the TQPP compounds facilitates the efficient cofacial stacking of the materials in the solid state and increases the intermolecular Pi-orbital overlap. Combining the electronic properties of the electron-deficient TQPP chromophore with the predisposition of the TQPP compounds to self-organize into efficient self-assembled Pi-Pi columnar stacks in a single molecule offers an interesting combination of physical properties and, perhaps, a route to new materials for electronic applications. In this talk, we will discuss the different properties and features of the TQPP compounds.

The active center of cytochrome c oxidases is a binuclear center containing a heme and a copper atom. Both metal centers (heme Fe and CuB) may be involved in NO₂ coordination and reduction since bona fide reductases are either heme-containing or copper- containing enzymes.^1,2,3
We will present Raman experiments of the reaction of Cytochrome c oxidase with NO₂ to determine the metal where NO₂ coordinates the redox active center that provides the required electron for NO₂- reduction. The structural properties of the intermediates that are formed upon NO₂- reduction by CcO are described.
Raman data was collected by a confocal LabRAM (HORIBA JobinYvon, Kyoto, Japan) equipped with a CCD detector and a grating of 1800 grooves/mm. The 514.1 nm excitation beam was provided by a Coherent Sapphire laser.

In this article, we are reporting conclusive experimental evidence from UV-Visible data for the existence of self-assembly structures in intermediate phase region which lays between 2.4 ≤ < r > < 2.54 across the Ge_xSe_1-x glass series. Various experimental studies were performed on chalcogenide glasses since 1996 until 2019 by many groups on modulated differential scanning calorimetry (MDSC). These studies have shown the presence of the intermediate phase, the so-called self-organized phase. Investigations on the compositional dependencies of the optical bandgap have revealed a non-monotonical trend in increase of bandgap due to nanocluster formation of different sizes. This gives rise to the intermediate phase region of the fluctuation driven bandgap and existence of the rigidity percolation threshold at < r > = 2.4. Glasses in the intermediate phase region are supposed to be stress free and homogenous. The results in the intermediate phase region are discussed and correlated with X-ray structural coherence data (D=2π/Δk from FSDP) which shows deviation from the mean field, from fluctuation-driven behavior in terms of network topologies and from percolative arguments. Irregular disorder in the compositional range plays a vigorous role for the manifestation of intermediate phase regions at room temperature. Our results extricate between triphase structural seclusion of the system across the Ge_xSe_1-x glass series.

Silver nanoparticles (NPs) exhibit significant antimicrobial activity against a broad range of bacteria and fungi at concentrations ranging from a few ppm to tens of ppm that are not cytotoxic to human cells [1,2]. Silver NPs also strongly enhance antibacterial activity against multiresistant, beta-lactamase and carbapenemase-producing Enterobacteriaceae when combined with antibiotics such as cefotaxime, ceftazidime, meropenem, ciprofloxacin and gentamicin [3]. All the antibiotics, when combined with silver NPs, showed enhanced antibacterial activity at concentrations far below the minimum inhibitory concentrations (tenths to hundredths of one ppm) of individual antibiotics and silver NPs. As a result, silver NPs have already been successfully applied in various biomedical and antimicrobial technologies and products used in every-day life as an alternative to conventional antimicrobials. While bacterial resistance to antibiotics has been discussed extensively in the literature, the possible development of resistance to silver NPs after repeated long-term exposure has not been fully explored. We report that the Gram-negative bacteria can develop resistance to silver NPs after prolonged exposure. The observed resistance stems from the production of the adhesive flagellum protein flagellin, which triggers the aggregation of silver NPs and eliminates their antibacterial effects. The resistance mechanism cannot be overcome by stabilization of silver NPs, by polymers or by surfactants. It is possible, however, to suppress it by inhibiting flagellin production with pomegranate rind extract [4].

The design of transition metal complexes with high emission quantum yields and other photophysical and chemical properties, optimized for particular applications, is a challenge. For organic light emitting devices (OLEDs), among other requirements, a short emission decay time is advantageous for reduction of saturation effects. On the contrary, for up-conversion, highly sensitive oxygen sensing and long-lived excited states of photocatalysis are preferred.
Structurally related silver complexes (1) Ag(dbp)(P₂-nCB) [1,2] and (2) Ag(dmp)(dpep)PF₆ [3], with dbp = 2,9-di-n-butyl-1,10-phenanthroline, P₂-nCB = nido-carboranebis(diphenylphosphine), dmp = 2,9-dimethyl-1,10-phenanthroline, and dpep = bis[(2-diphenylphosphino)phenyl] ether, respectively, are strongly luminescent with the emission quantum yields (PLQY) at ambient temperatures, approaching 100 % for 1 and 50 % for 2. The excited state (radiative) lifetimes differ drastically. For complex 1, an unprecedentedly short time is measured for this kind of luminescent materials' emission decay time of 1.4 microseconds (at PLQY = 100 %). For complex 2, the decay time (at PLQY = 50 %) is as long as 0.11 s. The short-lived emission of complex 1 originates from the efficient thermally activated delayed fluorescence (TADF) process, whereas the long-lived emission of complex 2 represents phosphorescence.
The distinctly different photophysical properties of these structurally similar compounds demonstrate the high variability of the molecular electronic structures and emission mechanisms. Using these compounds as extreme case examples, general trends and "recipes" for engineering of luminescent materials for defined applications can be elucidated.

Surface-modified silica nanoparticles that are copolymerized with one or more types of small organic molecules can be synthesized using a wide range of organic molecules, fluorescent or non-fluorescent, including near-infrared dyes due to the wide availability of modified reactive TEOS analogues. These silica nanoparticles that are copolymerized with dye molecules can be utilized as bright fluorescence labels or sensors. In addition, covalently surface bonded moieties can be added to silica nanoparticles to custom tailor the surface behavior of the silica nanoparticles. These surface modifiers can serve many purposes, such as molecular recognition. For example, introducing hydrophobic molecules to the surface of silica nanoparticles facilitates binding of the particle to hydrophobic molecules and surfaces. Fluorescence intensity of a single molecular label can be relatively weak requiring larger amounts of chemicals. One way to achieve sustainability during manufacturing or any chemical applications is to significantly reduce the amount of chemicals used. Another way to reduce the environmental impact of chemicals is to incorporate the molecules in a more environmentally friendly shield that effectively prevents the less desirable molecules from leaching out in the environment. All these can be achieved by encapsulating fluorophores in silica nanoparticles. The outside of surface tailored silica nanoparticles can be designed for any chemistry to make them more environmentally friendly. The encapsulated dye can serve as a simple reporting label, as a sophisticated molecular probe or as a tracer. Due to the large number of molecules that can be encapsulated in a single silica nanoparticle, the number of labels is very small, requiring minimal amount of chemicals. This presentation discusses the facile synthesis of silica nanoparticles using modified TEOS. Using the re-growth technique for surface modification, copolymerized fluorophores and surface bound moieties are introduced. Practical applications of these particles including environmental, forensic and analytical applications will be discussed. Surface modification examples will be given to achieve any desired behavior of the silica nanoparticle.

The principles of sustainable development in the food industry include general access to food that is safe, affordable and nutrient-rich, and aims to minimize energy consumption, avoid waste and loss of food ingredients throughout the supply chain, and reuse them if possible [1]. Waste of the fruit and vegetable industry is a significant environmental problem. Particularly noteworthy are vegetables, which were rejected in the production process due to unacceptable color, shape or mechanical damage. Most of this type of waste is characterized by high nutritional value, which is worth using when designing new products. An unconventional solution is to obtain vegetable gels that after freeze-drying may become one of the meals or supplement the meal taking the form of a bar [2, 3].
The aim of this work was to develop a three-layer freeze-dried vegetable snacks in the form of bar based on unused during proper production of frozen vegetables. Presented research are the stage of the project BIOSTRATEG 3/343817/17/NCBR/2018 “Development of healthy food production technologies taking into consideration nutritious food waste management and carbon footprint calculation methodology”.
Sodium alginate, and a mixture of xanthan gum and locust bean gum were used for the formulation of vegetable gels with carrot, potato, cauliflower, corn, broccoli, green and yellow bean, pepper, chives, dill. Vegetable gels were frozen (–40 °C/2) and freeze-dried (30 °C/63 Pa/72 h). The physical properties of freeze–dried bars included determination of: dry matter content, porosity, shrinkage and compression force.
The studies showed that obtaining freeze-dried vegetable snacks based on frozen vegetables not used during the proper production of frozen foods is possible and seems to be very promising considering the growing public awareness of healthy eating. It was shown that more important for physical properties of freeze-dried vegetable gels was hydrocolloid type than vegetables type. Snacks with a mixture of hydrocolloids contained more dry matter content, regardless of the proportion of individual vegetables compared to their counterparts with sodium alginate. The shrinkage of snacks with alginate was significantly larger. The porosity of the lyophilized gels was on the level of 89.06 to 91.82%. Snacks with sodium alginate had a larger number of fine pores, which resulted in a higher porosity and higher compression force when compared to samples with a hydrocolloid mixture.

Metal dendrite powders have received much attention owing to their unique physical and chemical properties. These particles have attractive nanostructures with large surface areas similar to nano-sized materials, despite being in the form of micro-sized particles that are easy to handle. In particular, Cu particles have been widely studied and used in many applications because of their conductive, catalytic, and optical properties. Moreover, Ag-coated Cu particles can be considered as an alternative for Ag particles because they provide equivalent conductivity at a lower cost [1a��4].
Bristle-glass-shaped Cu particles were fabricated via a fast galvanic displacement reaction for 3a��5 min under ambient conditions by adding metal particles into an aqueous electrolyte without chloride ions. The obtained Cu particles have a small average size of 4.44 I�m and short, multiple branches were aggregates of nanoparticles formed on stem-like backbones. The synthesized Cu dendrites could be protected against oxidation during drying via post-treatment using chelating or complexing agents. This novel technique to prepare the modified dendrites is extremely simple and suitable for mass production.
To obtain Ag-coated Cu particles, the synthesized Cu particles were successively coated with Ag via another galvanic displacement reaction by adding Ag plating solution into the Cu particle solution. The Ag coating was homogeneously performed with the selection of optimal Ag complex solution. The Ag-coated Cu particles induced the delay of oxidation initiation temperature from 150 to 178 ^oC during the dynamic heating to 500 ^oC in air. The metallic particles can be used as an anti-oxidation filler for conductive, electro-magnetic interference shielding, and metallic bonding materials.

Innovative building solutions for conserving non-renewable resources are connected to the development of sustainable building materials based on the use of easily renewable natural raw material resources, as well as the recycling of biomass wastes coming from textile, agricultural and paper industry. There is a renewed tradition that has been developed in Europe in light of environmentally sustainable policies to utilize the natural lignocelluloses' materials (usually derived from plants) and recycled cellulosic fibres as organic fillers and/or reinforcement into lightweight composite materials for sustainable constructions [1]. These provide healthy living solutions, thanks to the natural fibres' ability to regulate humidity inside buildings by absorbing and/or releasing water molecules, depending on the air conditions [2].
In connection with our research program on the properties and characterizations of different cellulosic fibre types and their incorporation into the cementitious matrix [3-5], the objective of this paper was to evaluate the application potential of low quality cellulosic fibres originating from waste paper in comparison to the bleached wood pulp with high cellulose content in making cement-plastering mortars. The influence of the quality of such fibres and their addition (0.1-0.5 wt. % from the binder and filler weight) on resulting properties of fresh cement mortars (consistency of fresh mixture) and mortar specimens (density, thermal conductivity, and compressive and flexural strength) after curing (28, 90 and 180 days) was investigated. The results revealed that the flow values of fresh fibre cement mixtures as well as the thermal conductivity and mechanical properties (compressive and flexural strength) of hardened mortars are affected by the cellulosic fibres (content and quality). Despite the worse workability of fresh mixtures and significantly reduced values of compressive and flexural strength of hardened fibre-cement specimens, with the addition of both fibre kinds compared to reference cement mixture and mortar due to inhibition of the cement hydration process, increasing addition of cellulosic fibres in the mixture led to favourable values of thermal conductivity which are beneficial for cement mortars with insulating properties. The obtained compressive strengths of 28 days of cured fibre-cement mortars are in the accepted range for plastering mortars. The results of comparative testing of fibre-cement mortar properties confirmed the suitability of the use of recycled fibres in building materials.