Ceramic Composite Materials Research Articles

The crack-healing and strength recovery mechanisms for the new developed Ti(C,N)-TiSi2-WC composite ceramic tool materials with crack-healing ability

Because the ceramic tool life will be reduced due to the crack growth, it is necessary to develop the new ceramic tools with crack-healing ability for improving the ceramic tool life. Ti(C,N)-TiSi2-WC composite ceramic tools were fabricated by vacuum hot pressing sintering technology. The Vickers hardness tester was used to prefabricate cracks with different lengths. The crack-healing abilities of materials were researched by air and vacuum heat treatments. The effects of different healing conditions on crack-healing behaviors were investigated based on the strength recovery and microstructure of crack morphology. The healing conditions included healing temperature, healing time, crack length and healing atmosphere. It could be found that the surface cracks were entirely healed after air heat treatment, but locally healed after vacuum heat treatment. After air heating at 800 °C for 90 min, the restoration ratio of flexural strength of the crack-healed samples returned to 109.02% compared to that of the smooth specimen. The strength of the crack-healed specimen would be fully recovered when the crack length was less than 400 μm. After vacuum heating at 1000 °C for 60 min, the recovery of the flexural strength of the crack-healed samples returned to 49.73%. X-ray diffraction and scanning electron microscope technology were used to analyze compositions and microstructure of crack-healed specimens. In the air atmosphere, the liquid filling of SiO2 and TiO2 and crack closure caused by WSi2 and MoSi2 were confirmed as the crack-healing mechanisms. SiO2 and TiO2 were produced by high temperature oxidation reaction of TiSi2 and WSi2. WiS2 and MoSi2 were new phases formed during sintering and heat treatment, and their formation could be explained by thermodynamically feasible reactions. In the vacuum atmosphere, local filling of the crack with silicide solid solutions such as WSi2, MoSi2 and NiSi was the main crack-healing mechanism.

Research Progress of Laminated Composite Ceramic Cutting Tools

The design of the lamination structure based on bionic shell pearl layer is a successful method for toughening ceramics. Lamination with strong bonding interfaces is used to improve the mechanical property and low fracture toughness of ceramic cutting tools. Based on the idea of demand–design–preparation–analysis–failure, the development and research progress of laminated ceramic tools are reviewed herein. The research status of design, interlayer diffusion reaction, residual stress, toughening mechanism, and crack propagation path of the biomimetic laminated ceramic composite tool materials is mainly introduced. The major topics of current research include the creation of material systems, the evolution of microstructure, and the assessment of macroscopic mechanical properties. The entire mechanical properties of laminated ceramic tools are significantly influenced by the multicomposition design of the ceramic material system and the optimization design of structural parameters of layer number and layer thickness ratio. However, the research on the practical cutting application of laminated ceramic tools is limited. Cutting tool wear characteristics vary between laminated and homogeneous ceramic tools. The development of useful laminated ceramic cutting tools can greatly benefit from the study on failure mechanisms of laminated ceramic tools.

Oxidation and Ablation Behavior of Particle-Filled SiCN Precursor Coatings for Thin-Film Sensors.

Polymer-derived ceramic (PDC) thin-film sensors have a very high potential for extreme environments. However, the erosion caused by high-temperature airflow at the hot-end poses a significant challenge to the stability of PDC thin-film sensors. Here, we fabricate a thin-film coating by PDC/TiB2/B composite ceramic material, which can be used to enhance the oxidation resistance and ablation resistance of the sensors. Due to the formation of a dense oxide layer on the surface of the thin-film coating in a high-temperature air environment, it effectively prevents the ingress of oxygen as a pivotal barrier. The coating exhibits an exceptionally thin oxide layer thickness of merely 8 μm, while its oxidation resistance was rigorously assessed under air exposure at 800 °C, proving its enduring protection for a minimum duration of 10 h. Additionally, during ablation testing using a flame gun that can generate temperatures of up to 1000 °C, the linear ablation rate of thin-film coating is merely 1.04 μm/min. Our analysis reveals that the volatilization of B2O3 occurs while new SiO2 is formed on the thin-film coating surface. This phenomenon leads to the absorption of heat, thereby enhancing the ablative resistance performance of the thin-film sensor. The results indicate that the thin-film sensor exhibits exceptional resistance to oxidation and ablation when protected by the coating, which has great potential for aerospace applications.

3D printed crack-free SiOC(Fe) structures with pyrolysis-induced carbon nanowires for enhanced wave absorption performance

High-performance SiOC(Fe) wave-absorbing ceramics, containing a large number of carbon nanowires, were successfully prepared using a combination of photopolymerization 3D printing technology and the polymer-derived ceramic pyrolysis method. By employing an optimized segmented slow heating scheme with extended holding time, the pyrolysis of SiOC(Fe) ceramics at 1000 °C facilitated the growth of carbon nanowires, Fe3C and SiO2 grains. These carbon nanowires were interlaced and interconnected within the samples, forming abundant conductive networks. This highly conducive network efficiently converted electromagnetic energy into thermal energy, effectively dissipating electromagnetic waves, and consequently enhancing the microwave absorption performance of ceramics. Moreover, this approach not only reduced ceramic cracks but also improved the dielectric loss performance of the materials, achieving a minimum reflectivity value of −35.72 dB. The SiOC(Fe) ceramics added with 5 wt% VcFe effectively enhanced the magnetic loss of the material, reduced the difference between the relative complex permeability (μr) and the relative complex dielectric constant (εr), and improved the impedance matching between the material surface and air, thereby further improving its microwave absorption performance. This resulted in an increase in the maximum effective absorption bandwidth of the material to 12.7 GHz at 5 mm. This study offers a promising solution for the preparation of ceramic matrix composite materials incorporating carbon nanowires, magnetic particles and ceramic precursors, which would be potentially valuable for radar detection and sensor applications.

Photoluminescence properties of Ba0.7Sr0.3TiO3:Sm3+ modified K0.5Na0.5NbO3 perovskite oxide ceramics

Ba0.7Sr0.3TiO3:Sm3+ modified KxNa(1-x)NbO3 ceramics with perovskite-type structure were synthesized via solid state sintering method. Sm3+ ions doping was designed for substituting both A and B sites in the ABO3 structure, Sm3+ doped Ba0.7Sr0.3TiO3 (Ba0.7Sr0.3TiO3:Sm3+) oxide precursor powders with the chemical formula of Ba0.7Sr0.3-xSmx(Ti1-xSmx)O3 (x=0.005 ， 0.015 ， 0.025) were synthesized. Combined Ba0.7Sr0.3TiO3:Sm3+ with K0.5Na0.5NbO3, the perovskite-type solid solution composite ceramics were fabricated via solid phase sintering method. X-Ray diffraction was used for investigating the phase structure of the precursor powders and luminescent composite ceramics. The photoluminescence properties of the Sm3+ ions in the Ba0.7Sr0.3TiO3-K0.5Na0.5NbO3 composite ceramic materials were systematically investigated by exploring the effects of composition of the composites, excitation wavelength and temperature on photoluminescence.

Experimental investigation and prediction of ECDM parameters on fiber reinforced SiC composite using hybrid ERNN-based Sparrow Search Optimization

The Silicon Carbide (SiC) fiber-reinforced SiC ceramic matrix composites have proved their outstanding performance on high thermal applications such as gas turbine engine parts, turbo-pumps, nozzles, and various other aerospace/aero-propulsion system parts. Regardless of their enhanced strength properties, the SiC fiber-reinforced SiC ceramic composite materials are difficult to process using conventional machining methods. Also, SiC fiber-reinforced SiC ceramic promotes a higher tool wear rate while doing conventional drilling operations. Therefore, this study investigates the Electrochemical Discharge Machining (ECDM) parameters on such SiC fiber-reinforced SiC ceramic composite. Besides, the levels of most influencing ECDM input parameters Voltage, Electrolytic Concentration and Duty Cycle are optimized using a novel hybrid machine learning optimizer called Elman Recurrent Neural Network-based Sparrow Search Optimization (ERNN-SSO). The experiment is planned using Response Surface Methodology based on Box Behnken Design (RSM-BBD) and verified using ANOVA. The Material Removal Rate (MRR), Tool Wear Rate (TWR) and Overcut (OC) are considered output performances during this study. The proposed ERNN-SSO has optimized ECDM input parameters at a maximum of 0.03 root mean square error (RMSE), approximately 33 % and 95 % lower than the conventional ERNN and RSM optimization techniques. This study’s suggested ECDM input parameters for drilling SiC fiber-reinforced SiC ceramic composite are 95 V voltage supply, 10 %Wt. of electrolytic concentration, and 50 % duty cycle. Because, such optimum ECDM parameters produced a maximum MRR of 370 μg/min with minimum TWR and OC of 283 μg/min and 161 µm during this study.

In English

Nowadays, people are constantly under the influence of electromagnetic radiation, which can cause health deterioration. The creation of ceramic materials that protect biological and technical objects from the negative effects of electromagnetic radiation is relevant for Ukraine and the world. The purpose of the study is to create composite ceramics with the addition of graphite and conduct experimental studies of the electrophysical properties of such material samples in the frequency range of 26–37.5 GHz. The results of experimental studies of the developed ceramics based on facing tiles with an electrically conductive additive of 10, 20, and 30 % wt. of graphite. To determine the parameters of the interaction of electromagnetic radiation with the samples, the modernized standard equipment – P2-65 microwave standing wave coefficient and attenuation meter, was used. The phase composition of the material was determined using the method of X-ray phase analysis using a DRON-3M diffractometer with CuKα radiation with a nickel filter. The developed composite ceramic materials meet the basic requirements for the operation of similar materials and can be used to weaken the high-frequency electromagnetic field inside premises located in the areas of radio radiation action, and for environmental purposes to reduce the intensity of the electromagnetic field outside the premises where sources of radio radiation are present. Thus, the developed composite ceramics have characteristics that allow them to be used in construction and in electronic devices for the purpose of effective shielding of harmful radio radiation, and the developed ceramics, according to the classification, can be classified as radio-absorbing.

Effect of CaF2@SiO2 on Si3N4/TiC Composite Ceramic Materials: Molecular Dynamics Analysis and Material Preparation

Molecular dynamics simulations allow to investigate the microscopic evolution of a structure, and can also point the way to tool material design. In this paper, the effect of adding CaF2 and CaF2@SiO2 on the Si3N4/TiC system is studied using molecular dynamics simulations. The results show that the system with the addition of CaF2@SiO2 to the model has a higher hardness than the system with the addition of CaF2. In order to obtain the optimum parameters for self-lubricating ceramic tools, the effect of adding different amounts of CaF2@SiO2 on the Si3N4/TiC system was investigated. The Si3N4/TiC/CaF2@SiO2 system achieved optimum mechanical properties when four CaF2@SiO2 were included in the model. By analyzing the effect of the sintering temperature on the system, it was deduced that the hardness achieved a maximum value of 15.89 GPa and the modulus of elasticity reached 132.53 GPa when the sintering temperature was at 2073 K. Based on this sintering parameter, the Si3N4/TiC/CaF2@SiO2 composite ceramic tool material was experimentally prepared with the mechanical properties of 15.66 GPa hardness and 128.08 GPa modulus of elasticity. The experimental results were consistent with the simulation results.

Strengthening and toughening of CNTs‐reinforced B4C‐SiC ceramic composite material via spark plasma sintering

AbstractFor addressing the issue of low relative density, poor fracture toughness of boron carbide ceramics, carbon nanotubes (CNTs)‐reinforced B4C‐SiC ceramic composite material was prepared via spark plasma sintering (SPS), and the impact of CNTs on the strengthening and toughening of the composite was studied. The evidence revealed that an appropriate amount of CNTs can enhance the discharge effect and improve the compactness. As the CNTs content increased, the flexural strength and fracture toughness took on a tendency to first rise and then drop. After mixing .5 wt.% CNTs, the flexural strength and fracture toughness were 499 MPa and 5.38 MPa·m1/2, which increased by 59.4% and 28.4%, respectively. The transformation of fracture mode, grain refinement, bridging and pulling‐out of CNTs efficiently enhance the mechanical properties.

Synthesis and electrical characterizations of (Sn0.8Ti0.2)O2 electronic material

ABSTRACT The ceramic composite electronic material of (Sn0.8Ti0.2)O2 has been synthesized through a cost-effective solid-state ceramic approach. The crystallographic tetragonal structure from the XRD spectrum, hydrophilic porous structure from SEM micrograph, dielectric, conductivity, and electrical modulus in addition to impedance spectroscopy over an extensive range of temperature and frequency have been elucidated. Hydrophilicity, superior dielectric response with significantly low dielectric loss, and enhanced capacitive behaviour draw the major attraction of this ceramic-based material system. The temperature-dependent conductivity spectrum evinces Arrhenius’s behaviour. The grain and grain boundary effects in the synthesized sample has been displayed through the Nyquist spectrum. The non-Debye type of relaxation mechanism has been established through an electric modulus study. The extensive study sketched out this composite as a potential capacitive electronic component for humidity sensor device applications. The investigated electrical parameters associated with the ceramic composite may enlighten the development of functional electronic devices.

An experimental and numerical study on the ballistic performance of a lightweight ceramic composite armor

In this paper, the ballistic limit velocity of 12.7mm armor-piercing incendiary projectile impacting a typical lightweight ceramic composite armor made of boron carbide ceramic and multi-layered composite materials (carbon fiber/aramid fiber/ultra-high molecular weight polyethylene fiber) was obtained experimentally. The process of impact was numerically simulated by the FEM-SPH method, and the results pointed out the characteristics of the penetration and the energy dissipation rule of each component of the ceramic composite armor. On this basis, the influence of thickness changing of the carbon fiber core layer on the ballistic performance of ceramic composite armor was studied with a typical “sandwich” structure, and the results showed that: when the thickness ratio of ceramic tile to the backing panel is about 1.5, the thickness changing of the carbon fiber core layer has the greatest effect on the ballistic performance. Under this thickness ratio, when the ratio of ceramic tile thickness to bullet diameter is greater than 1, the increase of carbon fiber core layer thickness will cause the ballistic performance index (BPI) of the target to decrease while the ratio is less than 1, the BPI increases or holds at first, and then decreases.

Structure and Properties of Ti3AlC2-SiC and Ti3AlC2-TiC Materials Obtained by Powder Injection Molding Technology

Powder injection melting (PIM) and material extrusion additive manufacturing (MEAM) are promising production technologies that allow us to obtain products from modern composite materials. These technologies make it possible to obtain products of complex shape from ceramic composite materials, which is a non-trivial task. A highly filled polymer feedstock is used as a source material in such technologies. In this work, a study of the structures and properties of samples obtained from SiC-Ti3AlC2 and TiC-Ti3AlC2 feedstocks by the PIM method was performed. The main purpose of this work was to study the influence of the powder compositions in feedstocks on the rheological properties and the structures of the obtained samples, as well as to determine the sintering parameters of samples of these compositions. In the future, it is planned to use the received and studied feedstocks in material extrusion additive manufacturing (MEAM). It was found that the investigated compositions had different MFI values depending on the composition. The effect of the sintering parameters on the structure and properties was shown. During the sintering of SiC-Ti3AlC2 ceramics in the temperature range of 1200–1400 °C in a vacuum, the main components of the mixture interacted with the formation of Ti3SiC2 and TiC. For materials of the TiC-Ti3AlC2 composition, partial oxidation of the material and the formation of titanium and aluminum oxides was observed.

How is it possible to get optimal infiltration fronts during chemical vapor infiltration with thermal gradients ?

Introducing thermal gradients to improve the Chemical Vapor Infiltration (CVI) process is a key strategy to overcome its principal drawback, namely, the presence of residual porosity in the central part of ceramic composite material preforms.The aim is to create an infiltration front starting from the least accessible part of the porous preform and progressing towards its surface. However, in practice, it may be quite difficult to evaluate the magnitude of the thermal gradient necessary for the achievement of this desired infiltration front. Modeling may bring solutions for the design of a successful processing situation. This paper reviews four distinct application examples, for which multi-physics numerical modeling studies have been developed and validated. These cases are also examined using analytical computations of a front infiltration criterion in order to discuss the influence of processing parameters on the quality of the process and of the resulting material.

Ultra‐broadband electromagnetic wave absorption of ceramic composite coating by atmospheric plasma spraying

AbstractDy doped ceramic material of Ba4Fe2.6Dy1.4Nb8O30 with the tetragonal black bronze structure was synthesized by solid‐state reaction at 1300°C. The composite powders of Ba4Fe2.6Dy1.4Nb8O30/FeSiAl with good flowing were prepared by spray drying using the powders slurry. The obtained composite powders were then plasma sprayed to fabricate coating. The microstructure and absorption characteristics of electromagnetic wave (EMW) of the coating materials are investigated. Results show that the composite powders significantly remain the phase stability during atmospheric plasma spraying and adsorbing heredity of EMW for the coating. The coating powders have excellent EMW absorption with the minimum reflection loss of −48.20 dB at the thickness of 3.5 mm. Also, the coating powders display the maximum effective absorption bandwidth of 6.24 GHz at the thickness of 1.5 mm, which covers the X‐band. Moreover, the coating was found to have a certain EMW absorption performance at high temperature of 700°C. The Ba4Fe2.6Dy1.4Nb8O30 ceramic material with low thermal conductivity ensured the electromagnetic absorption capacity of the coating at high temperature. The Ba4Fe2.6Dy1.4Nb8O30/FeSiAl ceramic composite materials could have the potential applications as the high temperature EMW absorber.

Strong Structure Formation of Ceramic Composites Based on Coal Mining Overburden Rocks

Currently, the amount of man-made waste worldwide is steadily increasing. It is, therefore, necessary to constantly look for effective ways of utilization and recycling. It is also necessary to reduce the use of non-renewable resources and reduce the impact on the environment. The use of coal industry waste is currently quite insignificant, amounting to some 10% of the total volume. The work aimed to study the properties of raw materials and study the processes of structure formation during the forming, drying, and firing of composite ceramic produced using overburden rock and additives. The work’s relevance lies in the need to solve environmental, economic, and technological problems related to the utilization of coal mining waste. Experiments of the past prove the possibility of using the waste coal industry as additives in the production of building materials. The article presents the results of studies of the chemical, mineralogical, and granulometric composition of overburden rock in coal mining. Peculiarities of structure formation during the forming, drying, and firing of ceramic composites based on optimal fractional compositions from coal-mine overburden were revealed. Organic and chemical additives were used for the correction of technological properties and improvement of the quality of finished composite products. The physical and mechanical indices of the obtained composite ceramic samples were determined, the analysis of which revealed that the use of highly mineralized carbonaceous rocks as solid additives provided a 2–2.5-fold increase in the strength of the product, 5.6% reduction in water absorption, and an increase in the product frost resistance by 20–25 cycles. The aluminum oxychloride influence on the physical and mechanical indices of the obtained composite articles was reflected in a reduction in their water absorption from 8.2 to 7.0%, a 10–12% increase in strength in compression, and an increase in freeze–thaw resistance by 30–35 cycles. Research results proved that the composition and properties of coal-mine overburden rock are close to those of conventional clays. With special technological preparation, they can be used for the production of composite ceramic products. This will significantly reduce the cost of bricks, to make up for the shortage of high-grade clay raw materials and improve the environmental situation. Nevertheless, further research into the use of coal-mine overburdens in the composite ceramic material technology is warranted.

Multi‐Objective Optimization During Magnetic Field Assisted ECDM of Alumina‐Zirconium Dioxide Ceramic Composite using Battle Royale Optimization

Alumina‐Zirconium dioxide (Al2O3‐ZrO2) Ceramic Composite Material (CCM) is specifically known for its enhanced mechanical and corrosion resistance properties and is widely used as raw material for mechanical parts like, pump components, die inserts, bearings, etc. As a result, industrialists are searching for an efficient method for machining this Al2O3‐ZrO2 material. In this regard, a hybrid unconventional machining process called Electrochemical Discharge Machining (ECDM) is adapted to analyze the machinability of Al2O3‐ZrO2 CCM. Besides, to ensure the efficiency of the ECDM process, a magnetic field is also given to the tool electrode during this study to improve the Material Removal Rate (MRR) of the ECDM machine. The experiment is designed using Response Surface Methodology (RSM) by changing the magnitudes of input controls, namely Electrolytic Concentration (EC), Inter‐electrode Gap (IEG) and Applied Voltage (AV). Moreover, a novel hybrid machine learning optimization strategy called Deep Belief Network based Battle Royal Optimization (DBN‐BRO) algorithm is developed to predict and optimize the ECDM process. Finally, the optimum results are perceived from 55 V AV, 22.727% EC and 40.909 mm IEG input levels. The proposed method shows less than 0.6207 Root Mean Square Error (RMSE) and tools nearly 80 iterations for optimizing the results.

Focused Nanosecond Pulsed Laser‐Induced Homogeneous Nucleation in Undercooled Oxide Melts

Induced homogeneous nucleation of undercooling melt is a fundamental challenge with exciting implications for composite ceramic and metal alloy materials. Nucleation can be induced externally, but physical mechanical properties reduce due to the introduction of impurities. Herein, a novel focused nanosecond pulsed laser‐induced nucleation approach is demonstrated for oxide ceramic melts at undercooled state. Using a self‐made aerodynamic levitation setup, the pulsed laser‐induced nucleation is controlled by optimizing the pulse energy density at different undercooled temperatures. Exploiting this approach, nucleation and growth are observed from surface of undercooled alumina (Al2O3) and neodymium yttrium aluminum garnet (Nd:YAG) melts with high‐speed camera. The undercooling sample experiences a nucleate–solidify–recalescence–remelting–recalescence–solidify process. The correlation between nucleation time and undercooling temperature confirms that the undercooled melt is nucleated homogeneously by the pulsed laser. The special microstructural of samples agrees well with the prediction of two‐step nucleation theory. Therefore, an assumption for the nucleation mechanism with the high‐speed images and the microstructure analysis is proposed. This proposed method may provide a different perspective for the classical nucleation theory of homogeneous nucleation.

Online prediction of grinding wheel condition and surface roughness for the fused silica ceramic composite material based on the monitored power signal

The fused silica ceramic matrix composite (SiO2f/SiO2) is characterized as one of the most promising materials in radar radomes and wave-transparent antenna windows. However, the ceramic matrix surface is rather rough, which reduces their service life in severe environments. Although precision grinding is used to improve surface quality, it gets difficult to precisely achieve the desired surface requirement due to the SiO2f/SiO2 material hardness, brittleness, and complicated fiber structure, as well as the uncertain wheel conditions. Especially the wheel condition and its influence on surface quality are unable to quantify directly. With the fast development of IoT monitoring and cyber-physical system, online prediction using process physics signals gains more interest. Power monitoring is a convenient way to obtain valuable grinding information at a relatively lower cost, making it more popular in the industry. However, the links between grinding parameters, power signal, and wheel conditions, surface quality is unclear. A series of grinding experiments of the SiO2f/SiO2 workpiece has been designed to demonstrate how the wheel conditions are indicated using the warm-cold density chart of specific grinding energy. A novel exponential polynomial model of surface roughness associated with wheel conditions indicated by the cutting power signal has been built. Compared with the conventional prediction model, REs center, MSE, and Pearson correlation coefficient are improved significantly from −0.0213, 0.029669, and 0.8695 to 0.0022, 0.022478, and 0.8710, respectively.

Digital Characteristics of Microstructure of Diamond—Silicon Carbide Composites

As an example of the implementation of digital materials science approaches based on statistical processing of electron micrographs with the analysis of fractal parameters, the digital characteristics of microstructure of diamond–silicon carbide ceramic composite material are calculated. The lacunarity parameter characterizing the non-uniform distribution of filler particles in the matrix is found. Based on lacunarity values calculated at different scales, scale invariance parameter characterizing the dependence of lacunarity on the scale is evaluated. Voronoi entropy characterizing the structure based on the quantity of information is also calculated and used to determine the average number of neighboring particles and average distance between them. For the composites with high mechanical properties, the number of nearest neighbors approaches six, indicating an almost closest packing.

Metallothermic SHS of Al2O3–Cr2O3 + TiC ceramic composite material

Ceramic composite material Al2O3–Cr2O3 + TiC was prepared by metallothermic self-propagating high-temperature synthesis (SHS) under 5 MPa of Ar pressure from green mixtures containing TiO2, Al, and C powders, and additive of CrO3 + Al blend. An increase in the mass fraction α of CrO3 + Al in the general charge was found to raise the synthesis temperature. For α < 0.2, sintered multiphase products were formed. In case of high additive content (α > 0.2), the combustion products were separated into two layers: carbide and oxide phases. Optimum synthesis conditions for forming the cast product consisting of Al2O3–Cr2O3 solid solution (“ruby”) and uniformly distributed TiC particles were found. In order to evaluate the possibility of using this material as a cutting tool, physical and mechanical properties were determined. SHS-prepared Al2O3–Cr2O3 + TiC composite after 24-h milling in a planetary mill, pressing under a pressure of 200 MPa, and sintering at 1460°С was found to possess density of 4.55 g/cm3, hardness of 20 GPa, flexural strength of 680 MPa, and crack resistance of 4.2 MPa m1/2.