SiC Phase Research Articles

Synthesis of N-doped SiC nano-powders with effective microwave absorption and enhanced photoluminescence

Although their preparation remains challenging, N-doped SiC nanostructures have received much attention due to their high performance characteristics compared to pure Si3N4 and SiC phases. In this study, N-doped SiC nano-powders were synthesized in one step through hexamethyldisilane pyrolysis in Ar/N2 plasma atmosphere. The results show that the undoped products included β-SiC nanoparticles sized in the range of 5–20 nm and carbon layers with 1–10 layers, while N-doped SiC nano-powders were mainly amorphous Si3N4/SiCN aggregates sized in the range of 30–200 nm with some β-SiC nanoparticles attached. The increased N2 flow rate and arc currents favored nitrogen doping and carbon removal. In addition, according to the X-ray photoelectron spectroscopy, the highest N-doping level approached 20% (atomic ratio). Nitrogen doping can effectively adjust the dielectric properties and affect the microwave absorption ability. The optimal reflection loss reached −56.2 dB at 8.9 GHz under an absorber thickness of 3.1 mm when the N-doping level was 12.1%. Moreover, due to the defect states, the N-doped SiC nano-powders exhibited good photoluminescence performance in the blue-green emission region. Therefore, the synthesized N-doped SiC nano-powders developed herein present potential applicability as microwave absorbers and light-emitting sources.

The effect of SiC whiskers addition on the microstructure and mechanical properties of a (Hf-Ta-Zr-Nb-Ti)C–SiC composite

High-energy ball milling of carbide powders, mixing with SiC whiskers, and following spark plasma sintering was used for the processing of a (Hf-Ta-Zr-Nb-Ti)C–SiC composite. A high relative density composite (99.4%) was achieved consisting of a single-phase high–entropy carbide (HEC) matrix and homogenously distributed SiC phase with evident degradation of the whiskers to particles. The grain size of the HEC matrix was in the range of 1.0–5.0 μm and the diameter of the SiC phase was about 0.5–6.0 μm with a low aspect ratio. The nano-hardness of the HEC matrix and SiC phase was about 38 GPa and 42 GPa, respectively. The microhardness increased with SiC addition from 24.4 to 28.7 GPa together with the indentation fracture resistance from 2.68 to 3.16 MPa m1/2 in comparison with the monolithic HEC of similar relative density and grain size. The toughening mechanisms were revealed to be crack deflection, crack branching, and crack bridging.

Isolating strengthening contributions in multiphase high entropy (Zr-Ta-W-Ti)C-SiC based carbide ceramics

Fully dense (ZrC-TaC-WC-TiC)-SiC (named as ZTaWT-S) based high entropy carbide (HEC) composites were fabricated using spark plasma sintering (SPS) at 1750 °C. Herein, effect of carbonaceous reinforcements (multi-walled carbon nanotube (CNT), graphite (G) and graphene (GNP) on microstructure and mechanical properties of the composites is assessed. The formation of a cubic rock salt high entropy carbide (HEC) phase is indicated via phase and microstructural characterization. Further, local elemental distribution using energy dispersive spectroscopy, and interplanar spacing calculation using transmission electron microscopy (TEM) confirmed the HEC phase formation in the sintered samples. Refined grains (∼3.9 μm), and high densification (>99%), has elicited an increasing hardness from 23.1 GPa to 30.2 GPa (by 30.7%) and elastic modulus from 372 GPa to 419 GPa (by 12.6%), which is attributed to an effective load transfer between matrix/reinforcement in ZTaWT-SGNP composite. An attempt is made to delineate the strengthening contributions from the porosity, high entropy phase, and other complex oxy-carbide and/or unreacted phases in multiphasic (ZTaWT-S) based HEC. Instrumented indentations (micro-indentation and nanoindentation) have facilitated delineation of contribution from various phases (i.e. HEC, TaC, SiC, and oxide phases). A remarkable enhancement is observed in the flexural strength from 390 MPa for ZTaWT-S composite to 487 MPa (by 24.9%), 519 MPa (by 33.1%) and 576 MPa (by 47.7%) for CNT, graphite, and graphene reinforced ZTaWT-S composites, respectively. The graphene reinforced composite exhibited highest flexural strength due to wrapping of GNP along grain boundaries, enhanced matrix/reinforcement adhesion, grain shearing and crack deflection. In summary, ZTaWT-SGNP composite exhibit superior mechanical properties and, thus, have potential structural applications in extreme environments.

Effects of density and heat treatment of C/C preforms on microstructure and mechanical properties of C/C–SiC composites

AbstractTwill multidirectional carbon‐fiber‐reinforced carbon and silicon carbide composites (i.e., C/C–SiC) were prepared via chemical vapor infiltration combined with reactive melt infiltration process. The effect of heat treatment (HT) on the microstructure and mechanical properties of C/C–SiC composites obtained by C/C preforms with different densities was thoroughly investigated. The results show that as the bulk density of C/C preforms increases, the thickness of the pyrolytic carbon (PyC) layer increases and open pore size distribution narrows, making the bulk density and residual silicon content of C/C–SiC composites decrease. Moreover, the flexural strength and tensile strength of the C/C–SiC composites were improved, which can be attributed to the increased thickness of the PyC layer. The compressive strength reduces due to the decrease of the ceramic phase content. HT improves the graphitization degree of PyC, which reduces the silicon–carbon reaction rate and thereby the content of the SiC phase. HT induces microcracks and porosity but not obviously affects the mechanical properties of C/C–SiC composites. However, the negative impact of HT can be compensated by the increased density of the C/C preforms.

Fatigue performance and material characteristics of SiC/AlSi10Mg composites by selective laser melting

By using selective laser melting, the SiC/AlSi10Mg composites were created. Under various process parameters, the impacts of SLM producing SiC/AlSi10Mg composites on density, microstructure, tensile characteristics, and fatigue properties were investigated. The results demonstrated that the density of the SiC/AlSi10Mg composites was closely related to the laser energy density. The density of SiC/AlSi10Mg composites might reach 99.7% under the ideal conditions. The Al4SiC4 phase grew with the rise in laser energy density as the aluminum matrix and SiC reacted in situ to generate a new strengthening phase Al4SiC4, which was dispersed on the matrix in a granular way. Therefore, the composite's tensile strength and microhardness reached their maximum values at 190.17HV and 435 MPa, respectively, when the energy density was 151.79J/mm3. This was due to the mixed strengthening mechanism caused by the SiC and Al4SiC4 reinforcing phase Compared with AlSi10Mg alloy, the addition of reinforcing phase SiC could significantly improve the fatigue resistance of composite materials. The fatigue fracture mode was brittle fractures, and the source of the crack was mainly from the surface pore defects. The size of the fatigue source defect size was related to the fatigue performance. The smaller the size of the defect, the more beneficial the fatigue resistance of the composite material.

Fabrication of Si/TiC–SiC/C composites as high-performance anode materials for Li-ion batteries

Si/TiC–SiC/C composites were prepared by solvothermal process, ball milling and subsequent calcination under Ar atmosphere. The microstructure of Si/TiC–SiC/C composites was characterized by X-ray diffraction, scanning electrons microscopy and transmission electron microscopy. Moreover, the relative contents of TiC and SiC phases in Si/TiC–SiC/C composites were determined by XRD Rietveld refinement and X-ray photoelectron spectroscopy, and their effects on the electrochemical properties of Si/TiC–SiC/C composites were further discussed. The results indicate that Si/TiC–SiC/C-0.33 composites with high relative content of TiC phase deliver capacity retentions of 98.0% after 50 cycles at 0.5 A g−1 and 79.5% after 150 cycles at 1 A g−1. The superior electrochemical performances should be attributed to the higher mechanical stability and better electronic conductivity of buffer matrix with higher TiC content.

High-temperature thermal stability of C/C-ZrC-SiC composites via region labeling method

To investigate the thermal stability of ceramic-matrix composites, three kinds of C/C-ZrC-SiC composites with different Zr/Si molar ratios were synthesized by reactive melt infiltration. Employing region labeling method, the high-temperature thermal stability of the composites was systematically studied by changing the temperature and holding time of thermal treatment. Results show that the mass loss rate of low Si composites has a growth trend with increasing temperature, and a crystal transformation from β-SiC to α-SiC occurs in the composites. In the calibrated area, SiC phase experiences Ostwald ripening and volume change with location migration, while ZrC phase experiences a re-sintering process with diffusion. Moreover, it is found that increasing temperature has a more obvious effect on the thermal stability than extending holding time, which is mainly attributed to the faster diffusion rate of atoms.

Carbothermal reduction of ZrSiO4 for in situ formation of ZrO2-based composites using spark plasma sintering

In the present study, ZrO2 based composites were synthesized in-situ and sintered by the novel RSPS-assisted carbothermal reduction of ZrSiO4 (Z) in the presence of graphite (G) and Activated Carbon (AC). The RSPS process was performed using a vacuum furnace at different temperatures of 1400–1600°C for 5–15 min under an external pressure of 30 MPa. The thermodynamic analysis was conducted on the synthesis process by FactSage software. The microstructure development and mechanical properties of RSPS-ed ZrO2-based composites were investigated. The Phase evolution and phase content, as functions of temperature, were characterized using x-ray diffraction and FESEM/EDS analysis. The XRD studies showed that all primary ZrSiO4 was decomposed into ZrO2, ZrC, SiC, and SiO2 phases. The unreacted graphite or activated carbon was also identified in the samples. Finally, the hardness and flexural strength of the composites were examined by Vickers hardness and 3-point bending strength tests. The results indicate that the SPS-ed ZrSiO4 + Activated Carbon composite (ZAS-3) has the best mechanical properties. A density of 2.87 ± 0.05 g/Cm3, an open porosity of 0.02%, a bending strength of 132.4 ± 11.2 MPa and a hardness of 9.86 ± 1.1 GPa were estimated for the SPS-ed ZrSiO4 + Activated Carbon mixture of powders at 1600°C.

ZrSi2-SiC/SiC Gradient Coating of Micro-Structure and Anti-Oxidation Property on C/C Composites Prepared by SAPS

A ZrSi2-SiC/SiC gradient coating system was designed to reduce the thermal stress of anti-oxidation coatings for C/C composites and prolong their anti-oxidation time at a high temperature. The SiC transition layer was prepared by pack cementation and the gradient ZrSi2-SiC outer coatings with different ZrSi2 contents added were deposited by supersonic air plasma spraying (SAPS). The micro-morphologies and phase compositions of the coatings were studied by SEM, EDS, XRD, and TG/DSC, and their anti-oxidation performances were tested by a static oxidation experiment. The findings suggested that the gradient coating with 30 wt.% ZrSi2 content displayed the optimum and dense microstructure without obvious pores and microcracks, compared with the other three proportional coatings. During the oxidation test, because of the oxidation reaction of ZrSi2 and SiC phases, a large amount of silica was formed in the coating to fill the pores and microcracks and densify the coating further. Oxidation products ZrO2 and ZrSiO4, having a high melting point and outstanding anti-oxidation property, were embedded in the SiO2 glass layer to reduce the layer volatilization rate and improve the ability to block oxygen. Therefore, the specimen with 30 wt.% ZrSi2 still kept mass gain after 188 h oxidation time at 1500 °C. However, when the oxidation time was increased to 198 h, it had a mass loss of 0.1%, because the coating compactness was destroyed by the escape of the oxidation gases.

Influence of Ni on the structural evolution of polymer-derived SiOC ceramics

Polymer derived ceramics (PDCs) technique is an advanced method for preparing high performance ceramics, in which pyrolysis process is an important step. In order to study the effect of the Ni transition metal on the pyrolysis process of polysiloxane, different contents of Ni acetate tetrahydrate (Ni(ac)2·4H2O)-impregnated polysiloxane (PSO) precursors were pyrolyzed in argon atmosphere between 1000 °C and 1300 °C. The organic-inorganic conversion behavior of precursors, the elemental and structural characterization of the Ni-free and Ni-containing SiOC ceramics were investigated. The results revealed that the presence of Ni not only enabled the growth of carbon nanotubes (CNTs) but also promoted the crystallization of carbon and SiC phase during the pyrolysis process. Additionally, high Ni content and pyrolysis temperature raised the diameters of CNTs and crystallinity of turbostratic layer carbon and SiC.

Investigating the Effects of SiC Abrasive Particles on Friction Element Welding

The use of dissimilar materials is increasing exponentially in the automotive industry due to the possibility of achieving weight reduction from the multi-material design. Friction Element Welding (FEW) is an advanced solid-state joining technique employed for joining dissimilar materials using a friction element. The processing time of FEW is relatively higher than a few of its competitive joining techniques, with the cleaning step contributing to the majority of the processing time. The current research investigates the effect of SiC abrasive particles on the processing time of FEW and its joint strength. The experimental results show a decrease in the processing time and an increase in the joint strength by reducing the abrasive particle size and the volume fraction of the abrasive particles used. When subjected to tensile loading, one of the samples showed interfacial failure, whereas others exhibited button pull-out failure. The best case from the experiments was chosen for comparison with the standard FEW test, which did not involve abrasives. The comparison shows a 14.3% reduction in processing time with a 10.8% increase in joint strength using abrasives. Inspection of the microscopic images revealed the presence of the SiC phase at the periphery of the friction element around the weld zone and the formation of a defect-free joint. The microhardness test detected a higher hardness along the weld zone for the case involving abrasives compared to the standard FEW test. The hardness data support the higher joint strength results obtained for the FEW joints formed with the abrasives.

Microstructure and mechanical properties of SiC particle reinforced Zr-based metallic glass surface composite layers produced by laser alloying

Metallic glasses (MGs) are a promising candidate for advanced structural applications due to their superior mechanical properties. Improving their surface mechanical properties would be of great importance for promoting their structural and functional applications. In this study, SiC particles were used as the reinforcement to improve the mechanical properties of Zr-based MG via laser surface alloying. The influences of the average laser power and overlap ratio between neighboring laser processing lines on the microstructure and mechanical properties of the laser-alloyed surface layer were investigated. The experimental results indicated that ZrC and SiC phases were successfully introduced into the MG matrix by laser surface alloying, and the content of these two hard ceramic phases was dependent on the laser processing parameters. The formed laser-alloyed surface layers exhibited a significant improvement in overall hardness compared with the as-cast specimen. At a relatively high overlap ratio of 70%, the average hardness of the MG matrix within the laser-alloyed surface layer reached 28.91 GPa, which was three times higher than that of the as-cast specimen (6.46 GPa). Furthermore, the microstructural characteristics and mechanical properties of the cross-sections of the laser-alloyed samples were characterized. The thickness of the laser-alloyed surface layer reached several tens of microns, and the SiC particles were uniformly dispersed in the whole laser-alloyed surface layer. This study confirms the feasibility for improving the mechanical properties of MGs by laser surface alloying, which is expected to broaden the application of MGs as structural and functional components under harsh severe conditions.

In-situ formation of titanium carbide in carbon-rich silicon oxycarbide ceramic for enhanced thermal stability

Silicon oxycarbide (SiOC) ceramic has attracted great attention as fascinating candidate of high-temperature material, however, its thermal stability is significantly limited by the phase separation at high temperature. Here, a TiC/SiOC ceramic was prepared by pyrolysis of a tetrabutyl titanate modified carbon-rich polysiloxane (TBT/PSO) precursor. The TiC phase is in-situ formed by the carbothermal reaction of TBT-derived amorphous TiO2 phase with excess free-carbon phase during pyrolysis, and its size and amount increase with the pyrolysis temperature. The SiC phase appears at a higher temperature than the TiC phase and is hindered by the increased Ti content in the TBT/PSO precursor. Thus, the TiC/SiOC ceramic exhibits better thermal stability and crystallization resistance than the TiC-free SiOC ceramic under the thermal treatment (1500 °C) in argon atmosphere. The in-situ formation of metal carbide into the carbon-rich SiOC ceramic would further expand its application at high temperature environments.

Improving mechanical properties of SiCw/SiC composite by phase content optimization via reactive melt infiltration

Inspired by the preparation methods of continuous fiber reinforced ceramic matrix composites (CFCCs), a novel silicon carbide whiskers (SiCw)-toughened SiC CMC with isotropic high strength and toughness, high density, and relatively low cost and short manufacturing cycle is prepared by a combination of gel-casting (GC) and reactive melt infiltration (RMI). The content and degree of graphitization of resin carbon during RMI are altered by annealing the SiCw/C mixture and adjusting the amount of SiCw to optimize phase composition and improve the mechanical properties of SiCw/SiC composites. The results reveal that the content of SiC phase is directly related to the flexural strength, reaching a maximum value of 339 MPa at 83 vol%. Also, the increase in C content increases the fracture toughness, reaching a value of 6.2 MPa m1/2 at carbon content of 4.6 vol%. The toughening of SiCw/SiC composites is realized by SiCw toughening, residual SiCw/C toughening and SiC particle toughening.

Composition of Carbon Clusters in Implanted Silicon Using Atom Probe Tomography.

Atom probe tomography was employed to observe and derive the composition of carbon clusters in implanted silicon. This value, which is of interest to the microelectronic industry when considering ion implantation defects, was estimated not to exceed 2 at%. This measurement has been done by fitting the distribution of first nearest neighbor distances between monoatomic carbon ions (C+ and C2+). Carbon quantification has been considerably improved through the detection of molecular ions, using lower electric field conditions as well as equal proportions of 12C and 13C. In these conditions and using another quantification method, we have shown that the carbon content in clusters approaches 50 at%. This result very likely indicates that clusters are nuclei of the SiC phase.

In-situ TEM study of Kr ion irradiation tolerance of SiFeOC nanocomposite

In this work, ion irradiation of polymer derived SiFeOC nanocomposite was carried out using 1.2 MeV Kr ions at room temperature and 600°C. The starting composite was composed of Fe3Si, SiC, SiOC, SiO2, and graphitic C. In-situ TEM investigations show uniform distribution of nano-crystalline Fe3Si and SiC phases in the amorphous SiOC matrix. During ion irradiation, the SiOC bulk microstructure and interfaces between Fe3Si or SiC crystallites and the SiOC matrix remain defect-free and demonstrate outstanding ion irradiation resistance. At room temperature, the crystalline domains are stable up to 2 dpa. At 600°C, Fe3Si crystallites are more stable than SiC; SiC crystallites are stable up to 4 dpa while the Fe3Si crystallites are stable up to 10 dpa. These crystallites also coalescence and amorphize simultaneously during ion irradiation. The exceptional tolerance to defect formation and irradiation of the SiFeOC nanocomposite provides important guidance to developing irradiation resistant fuels for advanced gas cooled reactors.

Effect of the fabrication process on the microstructural evolution of carbon fibers and flexural property on C/SiC composites by the NITE method

Nano-infiltration and transient eutectic phase (NITE) SiC matrix composites are designed for application in aerospace propulsion systems, particularly in fasteners and thrusters. A variety of carbon fibers with different properties have been selected as reinforcements for SiC matrix composites. Carbon fibers are known to be stable at high temperatures; however, the effects of high applied pressure at high temperatures on the fiber microstructure evolution and mechanical properties are not well-known. As a scoping study for fabricating NITE C/SiC composites, the behaviors of various carbon fibers in SiC composites. Pitch-based fibers, namely, GRANOX XN-05 and YS-90A, and a polyacrylonitrile-based fiber, namely, TORAYCA T-300B, were selected for matrix reinforcement. The 3-point bending test results indicated pseudo-ductile behaviors in the cases of YS-90A and T-300B fiber reinforcements. Fracture resistance evaluation based on the single-notch bending test indicated that the YS-90A fiber reinforced composite afforded the highest fracture resistance among the three C/SiC composites. The microstructure evolution on YS-90A and T-300B fibers was limited to near the fiber surface. Therefore, YS-90A and T-300B carbon fibers are potential candidates for reinforcement in NITE C/SiC composites.

Investigation of Microstructural Features and Mechanical Characteristics of the Pressureless Sintered B4C/C(Graphite) Composites and the B4C-SiC-Si Composites Fabricated by the Silicon Infiltration Process.

The B4C/C(graphite) composites were fabricated by employing a pressureless sintering process. The pressureless sintered B4C/C(graphite) composites exhibited extremely low mechanical characteristics. The liquid silicon infiltration technique was employed for enhancing the mechanical property of B4C/C(graphite) composites. Since the porosity of the B4C/C(graphite) composites was about 25–38%, the liquid silicon was able to infiltrate into the interior composites, thereby reacting with B4C and graphite to generate silicon carbide. Thus, boron carbide, silicon carbide, and residual silicon were sintered together forming B4C-SiC-Si composites. The pressureless sintered B4C/C(graphite) composites were transformed into the B4C-SiC-Si composites following the silicon infiltration process. This work comprises an investigation of the microstructure, phase composition, and mechanical characteristics of the pressureless sintered B4C/C(graphite) composites and B4C-SiC-Si composites. The XRD data demonstrated that the pressureless sintered bulks were composed of the B4C phase and graphite phase. The pressureless sintered B4C/C(graphite) composites exhibited a porous microstructure, an extremely low mechanical property, and low wear resistance. The XRD data of the B4C-SiC-Si specimens showed that silicon infiltrated specimens comprised a B4C phase, SiC phase, and residual Si. The B4C-SiC-Si composites manifested a compact and homogenous microstructure. The mechanical property of the B4C-SiC-Si composites was substantially enhanced in comparison to the pressureless sintered B4C/C(graphite) composites. The density, relative density, fracture strength, fracture toughness, elastic modulus, and Vickers hardness of the B4C-SiC-Si composites were notably enhanced as compared to the pressureless sintered B4C/C(graphite) composites. The B4C-SiC-Si composites also manifested outstanding resistance to wear as a consequence of silicon infiltration. The B4C-SiC-Si composites demonstrated excellent wear resistance and superior mechanical characteristics.

Nanocharacterization of spark plasma sintered TiB2–SiC–graphene composites

This investigation studies TiB 2 –SiC–graphene ceramics in terms of microstructure and mechanical properties. Spark plasma sintering (SPS) at 1800 °C was employed as manufacturing route, and the as-sintered composite was studied using high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), X-Ray diffractometry (XRD), and nano-indentation. The system was found to be unreactive, and all results dismissed the in-situ nucleation of B 4 C and TiC phases. Although TiO 2 and B 2 O 3 surface impurities were mainly reduced upon the incorporation of graphene nano-platelets (GNPs), the presence of SiO 2 in the final microstructure was confirmed by both XRD and HRTEM methods. The TiB 2 phase achieved a hardness of 35 GPa and a Young modulus of 539 GPa, which were roughly 45% and 25% higher than those measured for the SiC phase. • Microstructure and mechanical properties of TiB 2 –SiC–graphene composite was studied. • TEM, SEM, XPS, EDS, XRD, and nanoindentation tests were used for characterization. • Surface impurities of TiO 2 and B 2 O 3 were reduced by graphene nano-platelets.

Azide self-propagating high-temperature synthesis of highly dispersed TiN–SiC ceramic nitride-carbide powder composites

The study covers the method of azide self-propagating high-temperature synthesis (SHS-Az) to obtain a highly dispersed TiN–SiC ceramic composite with a theoretical ratio of nitride and carbide phases from 1 : 4 to 4 : 1 (in moles) using the combustion of the corresponding composition of powder reagent mixtures: NaN3 sodium azide, (NH4)2TiF6, (NH4)2SiF6 and Na2SiF6 halide salts, titanium, silicon and carbon in a nitrogen gas atmosphere. Thermodynamic calculations using the Thermo computer program showed that the optimum nitrogen pressure in the reactor is about 4 MPa, and the final composition of SHS-Az products can be completely different depending on the composition of reagents: it may include only target phases (TiN–SiC), contain silicon nitride and free carbon phases impurities (TiN–SiC–Si3N4–C) along with the target phases or consist only of nitride and free carbon phases (TiN–Si3N4–C). It was found that only target TiN and SiC phases are formed when using halide salt (NH4)2TiF6, at any ratio of nitride and carbide phases in the final powder composition. In cases where halide salts (NH4)2SiF6 and Na2SiF6 are used, target TiN and SiC phases are synthesized with an increased titanium content in reagents, i.e. only when composites of the 2TiN–SiC and 4TiN–SiC with an increased content nitride phase are obtained. Experimental studies of combustion products using scanning electron microscopy, energy dispersion analysis and X-ray phase analysis showed that they differ significantly from the theoretical compositions of products by the completely absent or significantly reduced SiC phase content in the final composition of powder composites synthesized during the combustion of bulk charge with carbon, and at the same time the absence of free carbon in the final composition of powder composites obtained. This difference is explained by the fact that when the combustion of a silicon and carbon powder mixture is initiated, silicon nitride is synthesized at the first stage with the temperature rising to high values of about over 1900 °C, at which the synthesized Si3N4 dissociates, and then at the second stage the resulting silicon reacts with carbon to form SiC that is more stable at high temperatures. But during combustion, very small light particles of carbon black (soot) may be removed (blown out) from a burning highly porous charge sample of bulk density by gases released at the first stage of combustion and not participate in the transformation of Si3N4 into SiC. In this regard, in case of low-carbon charge combustion, silicon carbide either does not form at all, or it is formed in small quantities compared to the theoretically possible amount, and Si3N4 silicon nitride remains the main component of the composite. A noticeable amount of SiC is formed only when burning high-carbon charges, but this amount is significantly less than the possible theoretical one, and the difference between them is replaced by the silicon nitride content. Therefore, it was experimentally shown for the first time that the SHS process can be used to obtain composites of highly dispersed ceramic powders TiN–Si3N4 and TiN–Si3N4–SiC consisting of a mixture of nanoscale (less than 100 nm) and submicron (100 to 500 nm) particles with a relatively low content of free silicon admixture (less than 1.4 %).