Internal erosion refers to the long-term and progressive process wherein seepage flow carries fine particles through the interstices between coarse particles, leaving empty voids within soil structure. This talk will introduce an experimental investigation into the progressive internal erosion behavior of two kinds of gap-graded granular soil, namely,  glass beads or Leighton Buzzard sand, during triaxial shearing using X-ray micro computed tomography (μCT). The experimental results reveal a wide range of particle- and pore-scale processes, behaviors and mechanisms that are responsible for the progressive internal erosion of the granular soils. The combination of experimental measurements and mCT image analysis reveal the evident impact of particle shape on internal erosion at both sample and pore scales. In contrast to spherical GB particles, the sample formed by irregular LBS particles exhibits higher shear strength, lower rate of fines erosion and different formation mechanisms of seepage channel. The above effects are found to be more attributed to the fine fraction rather than the coarse fraction of the gap-graded granular samples.

In recent years, there has been a growing interest in the use of solid oxide cells (SOCs) for the high-temperature co-electrolysis of CO2 and H2O, particularly when powered by excess electricity from renewable energy sources. This technology is regarded as one of the most promising for sustainable energy systems, offering high efficiency and the ability to generate syngas, a versatile intermediate for synthetic fuels and chemicals. Moreover, it enables efficient energy storage and the use of CO2 as a feedstock, aligning with circular economy principles and supporting deep decarbonization. High-temperature co-electrolysis in SOCs stands out compared to low-temperature electrolyzers by also enabling CO2 conversion, although it requires advanced catalysts and optimized operating conditions to avoid issues such as carbon deposition [1-3]. 
This paper presents the current state of research on catalytic materials and system configurations for the high-temperature co-electrolysis of H2O and CO2 in reversible SOCs. Key scientific challenges discussed include understanding the physicochemical nature of the co-electrolysis process on the fuel electrode and identifying the limiting factors of performance and stability. Development of advanced nanostructured catalysts, particularly those based on fluorite- and perovskite-type oxides, as well as composite systems that offer enhanced reactivity and chemical compatibility with Ni-YSZ cermets and YSZ electrolytes is presented. In addition to the material design, process optimization strategies such as catalyst infiltration into cells and electrode surface engineering are explored to improve the electrochemical performance and long-term durability. The work highlights the emerging methodologies and engineering pathways that form the foundation for next-generation high-efficiency co-electrolysis systems, while outlining the prospects for scalable implementation and integration with renewable energy technologies.

The first step to design highly active nanomaterials for renewable energy applications under electrochemical media is clear understanding of structure—property-performance correlation. For example, solid-stat electrolytes play key role for safer operation of lithium-ion batteries, however, its undesirably low ionic conductivities have delayed commercial applications. Nanoscale electrocatalysts are key components for renewable energy conversion reactions, but till now none satisfy the three criteria of activity, selectivity and stability in active liquid media. 

This presentation demonstrates a self-driving computational strategy to empower efficient and precise screening exploration of unknown candidates and exploitation of known materials, which are highly functional for energy storage and conversion reactions in electrochemical systems. Combined with first-principles DFT calculations and machine learning techniques with advanced algorithms we show that rigorous working principles for experimentally discovered nanomaterials can be elucidated. Moreover, design principles for even empowering higher performance are proposed. Most interestingly, several candidates are suggested, which can get over long-standing challenges to the nanomaterials applied to energy storage and conversion. As example, we show single atom catalysts, which are bi-functionally very active (oxygen reduction and oxygen evolution reactions) very active and allow the performance tunability according to target purpose. 

Green chemistry started for the search of benign methods for the development of nanoparticles from nature and their use in the field of antibacterial, antioxidant, and antitumor applications. Bio wastes are eco-friendly starting materials to produce typical nanoparticles with well-defined chemical composition, size, and morphology. Cellulose, starch, chitin and chitosan are the most abundant biopolymers around the world.   Cellulose nanoparticles (fibers, crystals and whiskers) can be extracted from agrowaste resources. Chitin is the second most abundant biopolymer after cellulose, it is a characteristic component of the cell walls of fungi, the exoskeletons of arthropods and nanoparticles of chitin (fibers, whiskers) can be extracted from shrimp and crab shells.  Starch nano particles can be extracted from tapioca and potato wastes. These nanoparticles can be converted into smart and functional biomaterials by functionalization through chemical modifications due to presence of large amount of hydroxyl group on the surface. The preparation of these nanoparticles includes both series of chemical as well as mechanical treatments; crushing, grinding, alkali, bleaching and acid treatments. Since large quantities of bio wastes are produced annually, further utilization of cellulose, starch  and chitins as functionalized materials is very much desired. The cellulose, starch  and chitin nano particles are currently obtained as aqueous suspensions which are used as reinforcing additives for high performance environment-friendly biodegradable polymer materials. These nanocomposites are being used as  biomedical composites for drug/gene delivery, nano scaffolds in tissue engineering and cosmetic orthodontics. The reinforcing effect of these nanoparticles results from the formation of a percolating network based on hydrogen bonding forces. The incorporation of these nano particles in several bio-based polymers have been discussed. The role of nano particle dispersion, distribution, interfacial adhesion and orientation on the properties of the ecofriendly bio nanocomposites have been carefully evaluated.

Radiotherapy remains a cornerstone in cancer treatment, yet its efficiency is often limited by radiation resistance and collateral damage to healthy tissues. Recent advances in nanotechnology offer promising solutions to enhance therapeutic efficacy while minimizing side effects. This study explores the application of gamma-irradiation-enhanced nanocomposites for colorectal cancer therapy. The synthesized nanocomposites, comprising silver-manganese (Ag-Mn) nanoparticles, were structurally characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and dynamic light scattering (DLS). Their biocompatibility and radiosensitization potential were evaluated through in vitro assays on colorectal cancer cells (HT-29). Our findings demonstrate that gamma-irradiated Ag-Mn nanocomposites significantly enhance radiation-induced apoptosis by increasing reactive oxygen species (ROS) production and inducing DNA damage in cancer cells. The results suggest that these nanocomposites lower the required radiation dose for effective tumor suppression, potentially reducing radiation-induced toxicity to surrounding healthy tissues. This research aligns with the symposium’s focus on advanced materials for healthcare applications and sustainable technologies in medicine, offering a novel approach to improving cancer treatment outcomes through nanotechnology-enhanced radiotherapy.

The global transition to low-carbon energy systems necessitates sustainable alternatives to conventional fossil fuel-based technologies. Hydrogen is a promising clean energy carrier; however, its current production methods, such as steam methane reforming, are associated with high greenhouse gas emissions [1]. Methane pyrolysis offers a low-emission alternative by thermally decomposing methane into hydrogen and solid carbon, without CO₂ as a by-product [2]. The use of catalysts in this process significantly lowers the required temperature for methane cracking, thereby improving the overall energy efficiency of the process. Liquid catalysts offer advantages over solid ones, as they avoid deactivation caused by carbon deposition [3]. The solid carbon formed during the reaction floats on top of the molten bath and can be easily removed. To date, research on liquid metal reactors has primarily focused on liquid non-ferrous alloys, such as nickel, copper, bismuth, and tin [4–6].

This study investigates the catalytic performance of iron–silicon–manganese alloys as liquid metal catalysts for the methane pyrolysis. The experiments were conducted in a lab-scale reactor and the main performance indicators evaluated were methane conversion and hydrogen yield under varying alloy compositions.

Results demonstrate that increasing the silicon content in the alloy significantly enhances methane conversion and hydrogen output. In contrast, the role of manganese remains inconclusive based on the available data. Post-reaction SEM analysis of the carbon product revealed contamination due to metal discharge from the catalyst, resulting in impurities that may limit direct carbon utilisation.

These findings highlight both the potential and challenges of using molten iron alloys in catalytic methane pyrolysis. Further research is required to optimise catalyst composition, minimise carbon contamination, and assess the scalability of this approach for industrial hydrogen production with integrated carbon management.

The use of metals as activators for sintering cubic boron nitride has certain advantages because it lowers the activation barriers between the components or makes the process partially liquid-phase, thereby creating a porous material [1]. Also, very importantly, chemical interaction occurs that promotes the consolidation of cBN grains both with each other and with reaction products. Among the classical metals used to create cBN polycrystals, Al and Co, Ni & Al combinations in amounts of 1-5 % by weight should be noted [2]. The addition of refractory Co also contributes to the crack resistance of cBN ceramics.

In this work, which was carried out under Contract No. 5.9/25-П(2) with the National Academy of Sciences of Ukraine, we made the first attempt to use heat-resistant Hf as an additive to cBN ceramics of the BL- group in order to observe the behavior of refractory metals for this type of tool ceramics. As a base system, we used a cBN-HfC composition that corresponds to the composition of the BL- group, in which we have already produced high-quality cutting inserts with a diameter of 9.52 mm. The starting mixture for sintering was a homogeneous charge of cBN-HfC-Hf composition (60:37:3 % by volume) with an average grain size in the range of 1-3 μm. The HPHT sintering of the charge, which was previously subjected to vacuum degassing, was carried out in a toroidal high-pressure apparatus at a temperature of 2250-2300 °C and a pressure of 8 GPa, the sintering time was 60 seconds. As a result of high pressure and temperature, superhard ceramics of the BL group were formed with a homogeneous microstructure, which included cBN grains, HfC in a practically unchanged morphological form, and newly formed fine-grained HfB₂ in amounts up to 8 % by volume, which is evenly distributed in the cBN-HfC matrix (three-phase ceramics). No residues of metallic hafnium could be detected by XRD. The hafnium boride with lattice parameters a = 0.3130 nm, c = 0.3458 nm has a dual origin due to the interaction of cBN with hafnium carbide and direct contact interaction with the metal itself. Since the formation of HfCN was not observed, we assume the displacement of N₂ from the reaction zone as a consequence of chemical transformations to balance the system. Given the fact that the T_mp. of hafnium is 2233 ^oC at atmospheric pressure, and high pressure only increases it, chemical reactions occur in the system at temperatures close to melting or by solid-phase transformations. The newly created ceramics are highly modular and superhard (HV = 33 GPa), which can be used to make cutting inserts with a diameter of 6.35 to 12.7 mm with a sharp cutting edge, suitable for metalworking hardened steels. Using the developed methodology with metal-containing components, the authors plan to use refractory high-entropy alloys as an effective additive for the sintering of cBN ceramics of the BL group for tooling purposes.

Closed-cell aluminum foams are increasingly gaining attention as lightweight structural materials due to their excellent energy absorption capabilities, low density, and favorable strength-to-weight ratio. However, their endurance under cyclic loading conditions (fatigue behavior) is yet to be fully understood [1], which is a critical limitation to make them relevant to aerospace, automotive, and structural applications. To address this challenge, our research explores the mechanical enhancement of closed-cell aluminum foams through carbon nanotube (CNT) reinforcement, focusing particularly on their fatigue life and failure mechanisms. 

The primary objective of this study is to evaluate how CNT integration affects the fatigue performance of aluminum foams under varying stress amplitudes and cyclic loading conditions. The potential of reinforcements to improve the mechanical properties of closed cell Aluminum foam under high strain rate loading conditions has been documented in our previous studies [2, 3], this motivated us to investigate local stiffness, crack propagation, and redistribution of stress at the cell wallsunder fatigue loading in the presence of CNT reinforcement. This work aims not only to extend the operational life of foams but also to understand the underlying reinforcement mechanisms at both the macroscopic and microscopic levels.

Fatigue testing are being conducted on both unreinforced and CNT-reinforced foam specimens using a servo-hydraulic MTS testing system under load-controlled conditions. Foam specimens with a relative density of ~0.30 +/- 5% are fabricated via liquid metallurgy route, with 0.5wt% CNTs uniformly dispersed into the aluminum matrix through mechanical stirring. The specimens are subjected to high-cycle fatigue (HCF) regimes, with stress ratio of R = 0.1 as is commonly used in other studies and at a frequency of 1 Hz, mimicking service-level loads. In addition, microscopic evaluations are being carried out using micro-CT to investigate the internal pore structure, deformation patterns and crack initiation and propagation patterns. Results of fatigue life curve of CNT reinforced aluminum foam will be presented along with deformation and failure mechanisms. 

The AlN-based dielectric composite materials with high resistivity values ​​are promising for use in electronics. However, ensuring a sufficient level of their mechanical characteristics is no less important condition for the practical use of products from these composites. For composites of the AlN-C-ZrB2 and AlN-C-TiN systems with resistivity >10⁹ Ohm, which were manufactured under hot pressing conditions at a temperature of 1900 °C and a pressure of 12 MPa, mechanical characteristics, in particular hardness and fracture toughness, were studied. 

Using a FALCON 500 microhardness tester with an optical camera, the Vickers microhardness was determined at a load of 98 N, and the fracture toughness of composite materials was also calculated taking into account the sizes of cracks emanating from the corners of the pyramid imprint. 

The obtained results of the measurements of the mechanical characteristics indicate a slight decrease in the hardness of the AlN-C-ZrB₂ and AlN-C-TiN composites in contrast to the aluminum nitride composite without additional components. The hardness value of AlN-C-ZrB₂ ceramics is 7.99±0.14 GPa, and AlN-C-TiN ceramics is 8.77±0.48 GPa, while for AlN ceramics the HV value is at the level of 11.34 ± 0.7 GPa. It is noted that for the material with a higher hardness value, the level of fracture toughness is also higher and is 5.01±0.34 MPa•m^1/2, while K_1C for the other composite, like the hardness value, is expectedly lower - 4.68±0.3 MPa•m^1/2. The adding components to aluminum nitride to improve electrodynamic characteristics results in a slight decrease in mechanical characteristics, but their level is high enough to withstand loads during material processing or when operating in vibration conditions.

Cellulose is the most abundant natural polymer and, as a result of its renewability, abundance, low cost and fascinating structure and properties, is being investigated to produce materials for water remediation [1]. Although cellulose is mostly used in the form of fibers and nanofibers, it can also be utilized in the form of particles at the micro and nanoscales [2], exhibiting large surface area and abundant surface hydroxyl groups that enable a variety of physical and chemical modifications [3]. In the present study, cellulose-based beads incorporating magnetic and catalytic nanoparticles (NPs) were developed for enhanced water treatment applications. The cellulose beads from wood pulp fibers were produced using a dual-fluid system, with one hemisphere functionalized with magnetite (Fe₃O₄) NPs and the other with platinum (Pt) NPs. Scanning electron microscopy (SEM) confirmed their spherical shape and the two distinct surface topographies. Additionally, the resulting beads exhibited magnetic properties, auto-propulsion, and the potential to reduce the levels of organic pollutants, such as Rhodamine B. This dual-functional material presents a promising approach for advanced water treatment by combining magnetic and catalytic properties to enhance pollutant removal.

Parts produced by additive manufacturing (AM) processes used metal powders are characterized by the high surface roughness. The potential applications of AM parts depend on suitable finishing technologies that ensure the surface quality needed to achieve the desired functionality and performance. Several post-processing methods have been evaluated, such as mechanical, electrochemical, chemical, laser, or their combinations. While these methods have reduced roughness, many of them could not to treat the entire surface of complex-shaped AM objects effectively and evenly [1, 2]. The paper focuses on the plasma-electrolyte process to treat the AM parts surface. In this process, the function of tool for reducing roughness is performed by electrical discharges between the machined surface and the electrolyte, and the internal movement of the vapour-plasma layer created by these discharges and evenly surrounds the entire treated object [3, 4]. 

The suitability of plasma-electrolytic process for surface post-processing and reducing roughness of objects produced by selective laser melting was verified on samples of AISI 316L steel printed on a Renishaw AM400 3D printer. Experimental work carried out on a 6 kW device with 4% electrolyte showed that the plasma-electrolytic process in anode mode can effectively reduce protrusions in the form of adhered particles and macroroughness of the complex-shaped objects’ surface from an initial average roughness of Ra 5–7 μm to 2–3 μm in 180 seconds, when the treated surfaces are characterized by high integrity and are free of oxide layers.

Hydrogen is increasingly recognized as a critical vector in decarbonizing industrial energy systems. Its utilization as a fuel and reducing agent in sectors such as metallurgy and chemical processing has the potential to reduce greenhouse gas emissions and enhance energy system resilience significantly [1]. However, conventional hydrogen production, e.g., via steam methane reforming, is associated with substantial CO₂ emissions, necessitating the development of more ecological alternatives [1]–[4].

Methane pyrolysis in metallic melts has emerged as a promising route for CO₂-free hydrogen generation [3], [5]. In this process, methane is decomposed in an oxygen-free atmosphere in the presence of a liquid-metal catalyst to form solid carbon and gaseous hydrogen [3], [5]. The process operates at a comparable specific energy demand to steam methane reforming but circumvents direct carbon dioxide formation [3], [4]. The pyrolytic carbon produced constitutes a potentially valuable co-product whose physicochemical properties strongly influence its marketability and the overall economic viability of the process [4].

This study systematically investigates the influence of varying process parameters on the quality and quantity of generated hydrogen and carbon. Particular emphasis is on the modulation of product properties relevant to downstream applications. The correlation between catalyst composition and yield is analyzed to identify optimal process conditions that balance product quality and conversion efficiency. The findings provide critical insights for designing integrated methane pyrolysis systems aimed at sustainable hydrogen and carbon co-production.

Organic long-persistent luminescence (OLPL) materials are emerging as promising candidates for advanced applications in biomedical imaging, optoelectronics, and photonic devices. Despite their potential, achieving prolonged afterglow durations comparable to inorganic systems has remained a significant scientific challenge. Our research breakthrough addresses this limitation through innovative trace doping strategies, successfully extending OLPL afterglow durations to an unprecedented 7 hours.^[1] A key discovery is the "Sergeant and Soldier" effect, where strategic trace dopants fundamentally modify crystal packing, dramatically enhancing OLPL efficiency.^[2] Through comprehensive spectroscopic investigations, we uncovered that the performance enhancement originates from triplet-triplet energy transfer (TTET) mechanisms. Specifically, abundant triplet excitons within the host material drive sustained luminescence, a mechanism distinct from traditional intersystem crossing between guest and host molecules.^[3-4] Our insights provide a foundational understanding of energy transfer dynamics in room-temperature phosphorescence (RTP) and near-infrared (NIR) phosphors. By elucidating the intricate TTET mechanism, we offer a robust framework for rationally designing and tuning luminescent materials. These findings not only advance fundamental scientific knowledge but also unlock exciting possibilities for next-generation optoelectronic devices, innovative lighting technologies, and sophisticated biomedical imaging platforms.

In the context of growing concerns about power disruptions, grid reliability and the need for decarbonization, this study evaluates a broad range of clean technologies to replace traditional emergency diesel generators. A scenario-based stochastic optimization framework using actual load profiles and outage probabilities is proposed to assess the most promising options from a pool of 27 technologies. This framework allows a comparison of costeffectiveness and environmental impact of individual technologies and combined backup power systems (BPS) across various scenarios. The results highlight the trade-off between total annual system cost and emissions. Significant emission reductions can be achieved at moderate cost increases but deep decarbonization levels incur higher costs. Primary and secondary batteries are included in optimal clean fuel-based systems across all decarbonization levels, combining cost-effective power delivery and long-term storage benefits. The findings highlight the often-overlooked importance of fuel replacement on both emissions and costs. Among the assessed technologies, ammonia generators and hydrogen fuel cells combined with secondary iron-air batteries emerge as cost-effective solutions for achieving decarbonization goals. To ensure a broad range of applicability, the study outlines the impact of emergency fuel purchases, varying demand patterns and demand response options on the optimal BPS. The research findings are valuable for optimizing decisions on clean BPS to economically address diverse applications and decarbonization targets.

In this work, a new kind of fullerene solid is constructed using carbon cluster C50 with D5h symmetry. It is found that this solid is softer than the diamond through the comparision of bulk modulus. This new type of semiconductor has the indirect band gap of 0.338 eV. The stability of this solid is further confirmed by the phonon spectra calculation, which indicates that it is a new metastable configuration of carbon. After doping nitrogen atoms into this stable solid, we find that the N-doped system still remains to be the semiconductor, the band gap of which increases to 0.469 eV. The formation energy of the N-doped system is -1.090 eV/cage. Moreover, the lattice parameters of this N-doped system differ little from those of the undoped C50 system, which means that the doped system and the undoped C50 system can connect along some crystal orientations, forming the semiconductor heterojunction.

Printing defects produced during additive manufacturing (AM) processes can have a significant detrimental effect on functional properties. This mainly relates to their influence on mechanical properties and corrosion performance. The present study aims to evaluate the effect of printing defects created during AM using direct energy deposition (DED) process. The raw material selected for this examination was 316L stainless steel in the form of welding wires. The printing defects were examined by micro-tomography (CT) analysis while the microstructure assessment was carried out using optical and scanning electron microscopy along with X-ray diffraction analysis. The mechanical properties were examined in terms of tensile strength, hardness measurements and fatigue endurance. The corrosion performance was tested by potentiodynamic polarization analysis, while stress corrosion resistance was examined by means of slow strain rate testing (SSRT). The results obtained emphasize the relatively reduced mechanical properties, fatigue endurance, corrosion resistance and stress corrosion performance of the AM alloy compared to its counterpart wrought alloy AISI 316L produced by conventional processes. This was mainly attributed to typical AM printing defects such as porosity and lack of fusion as well as dissimilarities in terms of phase compositions. The pure austenitic structure of the conventional wrought alloy was converted to duplex microstructure that encountered an austenitic matrix and a secondary delta-ferrite phase in the AM alloy which have a detrimental effect on the inherent passivity.      

The structural, electronic and mechanical properties of RuB_x(x=1,2,3) are investigated by performing first principles calculations using density functional theory (DFT). The calculated lattice constants agree well with the available results. The chemical bonding is interpreted by calculating the electron localization function (ELF). The covalent Ru-B bond and B-B bond become stronger with the increase of boron’s concentrations, which can help improve the hardness of RuB_x system. Moreover, RuB has the highest bulk modulus, which means more prominent volume-compression resistance. RuB₂ has a certain elastic anisotropy and RuB3 has the best toughness.

Ultrahigh- Amorphous highly conductive coatings Ti-Al-C, (Ti,Mo)-Al-C and (Ti,Cr)-Al-C were deposited on titanium alloy substrates by hybrid magnetron using T₂AlC and Ti₃AlC₂ MAX-phases-based targets and in parallel cathode-arc evaporation of Mo or Cr targets. The (Ti,Cr)-Al-C coating demonstrated the highest long-term oxidation resistance, and after heating in air at 600 °C for 1000 h, its surface electrical conductivity became even slightly higher after long-term heating: increased from s= 9.84×10⁶ S/m to s= 4.35×10⁵ S/m, which is explained by the crystallization of the amorphous coating during heating process. The nanohardness and Young's modulus of the coating after deposition were within 15 GPa and 240 GPa, respectively. The (Ti,Cr)-Al-C coating showed the highest electrochemical corrosion resistance among all deposited coatings in 3.5 wt.% NaCl aqueous solution at 25 °C: corrosion potential E_corr = 0.044 V vs. saturated calomel electrode, corrosion current density i_corr = 2.48×10^-9 A/cm². The hybrid magnetron deposited (Ti,Cr)-Al-C coatings can be used to protect interconnects in lightweight molten carbonate fuel cells elements.

Ultrahigh-temperature, corrosion-resistant materials based on HfB₂ (melting point of HfB₂ - 3380 ^oC) have high thermal conductivity, high level of mechanical characteristics, high corrosion resistance in oxidizing atmosphere due to the ability to form protective, oxidation-resistant scales at elevated temperatures. They are promising for many ultrahigh-temperature applications, for example, for the manufacture of nozzles for aircraft and rocket engines that are in contact with aggressive gases at high temperatures, as well as for the manufacture of wing edges and fairings for supersonic aircraft, etc. It is known that the addition of SiC to HfB₂ can increase the mechanical properties of composite. The results of present investigations (obtained in the framework of III-5-23 (0786) grant from the National Academy of Sciences of Ukraine) showed that on the densification, mechanical characteristics and resistance toward ablation important role play sizes and quality of SiC initial powder used as addition. Such effect we observed both for the composites prepared under hot pressing conditions (30 MPa pressure) and conditions of high pressure (2 GPa) – high temperature. Our previous studies have shown that the use of high pressures and temperatures and hot pressing, and the addition of SiC to HfB₂ allowed us to achieve a level of mechanical properties of the resulting ceramic materials that, in terms of hardness and crack resistance, surpass the best world analogues. It was also shown that the addition of SiC significantly reduces the melting point and accelerates the oxidation kinetics upon heating. The microhardness, H_V, and fracture toughness, K_1C, (at an indentation load of 9.8 N) of the HfB₂-30 wt.% SiC(5-10 µm) composite material which was hot pressed (under 30 MPa) were H_V =38.6 ±2.5 GPa and K_1C =7.7 ±0.9 MPa m^0.5 when specific density 6.54 g/cm³ (and near zero porosity) was attained. For HfB₂-30 wt.% SiC(30-50 µm) porosity was about 17 % and H_V = 28.1 ±11.3 GPa and K_1C = 6.1 ±2.2 MPa m^0.5. Hot-pressed HfB₂ without additives exhibits H_V = 18.9 ±0.1 GPa and K_1C = 7.65 ±0.6 MPa·m^0.5, porosity 2.4% and specific density 10.79 g/cm³. Ablation tests in air of the samples of ultrahigh-temperature hot-pressed ceramics based on HfB₂ and HfB₂-SiC when heated with a gas burner (into which an O₂/C₂H₂ mixture was fed, and the distance to the sample surface was 13 mm) showed that HfB₂ ceramics with an additive of 30% by weight of SiC with a grain size of 30-50 μm and 5-10 μm turned out to be significantly more stable (up to 2066-2080 °C, respectively, at an internal mass of 0.25 mg/s) than ceramics with HfB₂ without the additive (cracked at 1870 °C).