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High thermally conductive β‐Si3N4 is a new type of filler for thermally conductive materials. Tailoring its aspect ratio is crucial to optimize the preparation process and performance of polymer‐based thermal conductive materials. In this work, β‐Si3N4/BN thermally conductive hybrid fillers were prepared by combustion synthesis in a nitrogen atmosphere using low‐cost Si, B2O3 powders as raw materials, and the aspect ratio of β‐Si3N4 crystals were regulated according to the inhibiting growth strategy of second phase BN generated by in situ reaction. With the increase of B2O3, the content of BN increased slightly, while that of β‐Si3N4 decreased slightly. The aspect ratio of β‐Si3N4 decreased from 6.3 ± 1.9 to 1.9 ± 0.6, which might be ascribed to the inhibiting effect of BN sheets on the axial growth of rod‐like β‐Si3N4. Low‐aspect‐ratio β‐Si3N4/BN/epoxy composite exhibited high thermal conductivity of 1.04 W·m‐1·K‐1at the solid content of 50 wt%, which was 372.7% and 30.0% higher than that of neat epoxy and 40 wt% high‐aspect‐ratio β‐Si3N4/epoxy composite, respectively. In addition, β‐Si3N4/BN/epoxy composite also had good mechanical properties. [ABSTRACT FROM AUTHOR]

α‐Si3N4 powder was prepared by combustion synthesis method. The propagation characteristics of combustion wave were investigated by thermocouple temperature measurement and "resistance—combustion wave displacement response device." The results show that the combustion reaction takes place in a narrow area, and there is a maximum temperature gradient of 180°C/mm in the combustion front. The "resistance—combustion wave displacement response device" was innovatively used to realize the in situ measurement of combustion wave propagation process. The test results showed the pulse combustion mode in which the combustion front took 10 s as a cycle, and the quantitative data of Si–N2 discrete combustion characteristics were obtained for the first time. [ABSTRACT FROM AUTHOR]

α-Si3N4 powders with 91% α content and no impurity of Si2N2O were prepared by combustion synthesis using diamond wire Si cutting waste. The effects of H2O, SiO2 and NH4Cl additives on the nitridation mechanism, phase composition and microstructure of Si3N4 powder prepared by combustion synthesis were investigated. The results showed that the synergistic effect of H2O and SiO2 in Si cutting waste and NH4Cl improved the product α-Si3N4 content and no Si2N2O formation. The thermodynamic calculation shows that NH4Cl, H2O and SiO2 can promote the gasification of Si, and in the presence of HCl, the SiO gas produced by the reaction of H2O and Si powder transforms into SiCl4 at high temperature, thus reducing the Si2N2O content of the product. [ABSTRACT FROM AUTHOR]

Hollow spherical β‐SiC was successfully prepared in argon by combustion synthesis using Si powder and polytetrafluoroethylene (PTFE) powder. The phase composition and morphology of spherical products can be controlled by adjusting the Si/C2F4 molar ratio (MSi/(C2F4)). When MSi/(C2F4) = 3, the phase content of β‐SiC is the highest (up to 85.54%), and hollow spherical products obtained; When MSi/(C2F4) ≥ 5, the Si/SiC microspheres are solid. The synthesis mechanism of hollow β‐SiC microspheres is as follows: Si particles react with PTFE releasing heat. Then unreacted Si absorbs heat to form liquid phase microspheres, which is equivalent to the core template to form β‐SiC microspheres by reaction with cracked C. Meanwhile, the silicon diffuses from the core to the shell to form the cavity. This method can synthesize the hollow spherical β‐SiC in a simple way without prearranged spherical template and long synthesis cycle. [ABSTRACT FROM AUTHOR]

Abstract: CuIn1‐xGaxSe2 and CuIn(SySe1‐y)2 bulk materials with relative densities of 93.4%‐96.2% have been prepared by combustion synthesis, from elementary reactants and in a reaction time of a few seconds. The samples have a chalcopyrite lattice structure, and the lattice parameters decrease with increasing x and y. The substitution of In with Ga and Se with S in CuInSe2 causes an increase in the bandgap. In combustion synthesis, the high temperature accelerates the reaction and results in fast densification, the high heating rate simplifies the reaction path and avoids the formation of intermediate compounds, and the gas pressure depresses the evaporation of reactants. As a fast, furnace‐free, and scalable technique, combustion synthesis may offer a low‐cost way to produce CuInSe2‐based materials and bring new possibilities to their commercial applications. [ABSTRACT FROM AUTHOR]

InSe, In2Se3, and GaSe are important III-VI semiconductors and are attractive for electronic, optical, and optoelectronic applications. This paper reports a fast and cheap way called combustion synthesis to prepare InSe, In2Se3, and GaSe. Bulk samples with relative densities up to 98% are directly produced in a few seconds. The samples show a high phase purity, correct stoichiometry, and lamellar crystals larger than 100 μm. By optical absorption, the bandgaps of InSe, In2Se3, and GaSe are determined to be 1.08, 1.24 and 1.75 eV, respectively. [ABSTRACT FROM AUTHOR]

S and Te-doped Cu2SnSe3 samples with chemical formula of Cu2SnSe3-xSx and Cu2SnSe3-xTex (x = 0.05, 0.10, 0.15, 0.20) are prepared, and the effect of S and Te-doping on thermoelectric properties is investigated. In all the samples, the Cu2SnSe3 phase is synthesized as the major product, and its lattice parameters decrease with S-doping but increase with Te-doping. EDS analysis confirms the incorporation of S and Te dopants in the Cu2SnSe3 phase, and reveals an element segregation in the Te-doped samples. S- and Te-doping decreases the electrical conductivity, enhance the Seebeck coefficient, and reduce the thermal conductivity. S-doping is effective to improve the ZT of Cu2SnSe3, and the Cu2SnSe3-xSx sample with x = 0.05 shows a ZT of 0.66 at 773 K, which is improved by more than 50% compared with that of the undoped sample. On the contrary, Te-doping leads to decreased ZT values owing to the significant reduction in electrical conductivity. [ABSTRACT FROM AUTHOR]

TiB 2 -TiC-WB composite ceramic powders have been prepared by fast combustion synthesis from Ti, W and B 4 C, by coupling the weak exothermic reaction of W + B = WB with strong ones of Ti + 2B = TiB 2 and Ti + C = TiC. With increasing W/(Ti + W) ratio, the reaction temperature and heating rate decrease while the content of WB increases, and unreacted W appears for W/(Ti + W) = 0.24. The addition of excessive B 4 C leads to lower reaction temperature, smaller grain size, and formation of WB 2 . The products show a homogeneous microstructure without element segregation on the scale of agglomerates, and in most products the average grain size is smaller than 1 µm. [ABSTRACT FROM AUTHOR]

The reaction mechanism in fast combustion synthesis of FeSe and FeSe 0.7 Te 0.3 is investigated by a special quenching experiment and thermal analysis. The reaction temperature exceeds the melting point of Se but is below that of Fe, and the reaction takes place at the interface between solid Fe and liquid Se. By thermal analysis, the reaction almost immediately starts after Se melts and persists in a broad temperature range. By linear fitting from DSC data, the activation energies are calculated to be 102 ± 8 kJ/mol for the reaction of Fe + Se = FeSe and 138 ± 22 kJ/mol for Fe+0.7Se + 0.3Te = FeSe 0.7 Te 0.3 . The reaction zone consists of continuous liquid Se and separately distributed Fe solid particles, where each Fe particle together with the surrounding Se liquid layer can be regarded as a reaction cell. In a planar reaction front, the mass transfer and heat exchange between two reaction cells can be ignored, and the reaction happens individually but simultaneously in every cell. From microstructure characterization, it is suggested that the infiltration of Se liquid also plays an important role in mass transfer besides the conventional diffusion process. An evident element segregation is observed in the Fe(Se,Te) product, and the distributions of Se and Te are complementary. To explain the segregation phenomenon, an oscillatory reaction mechanism is proposed, where Se and Te alternatively reacts with Fe accompanying the oscillation of concentrations of Se and Te in the liquid. The reaction mechanism discussed here is likely to also operate in other solid-state synthesis approaches, and may help to optimize the processing parameters to improve the quality of synthesized Fe(Se,Te) samples. [ABSTRACT FROM AUTHOR]

Dense bulk samples of (Ag,In)-co-doped Cu2SnSe3 have been prepared by a fast and one-step method of combustion synthesis, and their thermoelectric properties have been investigated from 323 to 823 K. The experimental results show that Ag-doping at Cu site remarkably enhances the Seebeck coefficient, reduces both electrical and thermal conductivities, and finally increases the figure of merit (ZT) value. The ZT of the Cu1.85Ag0.15SnSe3 sample reaches 0.80 at 773 K, which is improved by about 70% compared with the unadulterated sample (ZT = 0.46 at 773 K). First principle calculation indicates that Ag-doping changes the electronic structure of Cu2SnSe3 and results in larger effective mass of carriers, thus enhancing the Seebeck coefficient and reducing the electrical conductivity. The low electrical conductivity caused by Ag-doping can be repaired by accompanying In-doping at Sn site, and by (Ag,In)-co-doping the thermoelectric properties are further promoted. The (Ag,In)-co-doped sample of Cu1.85Ag0.15Sn0.9In0.1Se3 shows the maximum ZT of 1.42 at 823 K, which is likely the best result for Cu2SnSe3-based materials up to now. This work indicates that co-doping may provide an effective solution to optimize the conflicting material properties for increasing ZT. [ABSTRACT FROM AUTHOR]

Abstract: Combustion synthesis is widely used for preparing various refractory and hard materials, including alloys, intermetallics, ceramics, and cermets. The unique reaction condition in combustion synthesis with extremely-high temperature and fast heating/cooling rate offers the products interesting microstructures and superior mechanical properties. In comparison with conventional powder metallurgy approaches, combustion synthesis exhibits the advantages of short processing time, less energy consumption, and lower cost, thus providing a more efficient way to produce refractory and hard materials. This article reviews recent progress in combustion synthesis of refractory and hard materials, with an emphasis on the results reported in the last decade. Both the synthesis of powders and direct fabrication of bulk materials are discussed. For the synthesis of powders, results in two aspects are reviewed, viz. synthesis of ultrafine and especially nano-sized powders by thermal reduction reactions or post chemical etching, and synthesis of nitride and carbide powders in air. For direct fabrication of bulk materials, two techniques are involved, viz. combustion synthesis with simultaneous densification assisted by a mechanical or gas pressure, and combustion synthesis casting in a high-pressure Ar atmosphere or in a high-gravity field. [Copyright &y& Elsevier]

This article studies the preparation of Fe3Al alloy by combustion synthesis melt-casting under ultra-high gravity. The heavier Fe melt could rapidly separate from the mixed melt under ultra-high gravity field of 1,000 g, and reacted with the loose aluminum powder to form Fe3Al intermetallic compound. In this Fe3Al alloy, almost all the pores were eliminated during the rapid solidification, and a high compacted alloy ingot was obtained. The Fe3Al alloy exhibited very small rate of oxidation below 1,000°C, but the oxidation rate increased sharply at higher temperature due to the increased scale spallation. [ABSTRACT FROM AUTHOR]

Abstract: Si–Al–Y–O glasses and glass-ceramics were prepared via melt-casting by combustion synthesis under high gravity. The phase assemblage and microstructure of the cast products strongly depended on the content of SiO2 and the additive ZrO2 or La2O3 in the starting compositions. With increasing content of SiO2, the glass-forming ability of the melt was enhanced. The additive ZrO2 was not dissolved into the glass and inclined to crystallize, but La2O3 was inclined to remain in the glass matrix instead of precipitation. With a short processing period and lower energy consumption, combustion synthesis under high gravity can offer a new approach to fast fabrication of glass and glass-ceramic materials. [Copyright &y& Elsevier]

Abstract Combustion synthesis is a fast and energy-efficient process to prepare inorganic materials from self-sustained combustion reactions. It is widely used for preparing ceramics, metals, and their composites. The unique condition in combustion synthesis with high temperatures and large heating rates offers good opportunities to explore new materials and novel microstructures. This paper gives a viewpoint on recent progress in combustion synthesis, from fundamentals to applications. New results on theories, processings, and materials are reviewed, and perspectives on the development of combustion synthesis are provided. [ABSTRACT FROM AUTHOR]

Ti 1−x W x C solid solution powders have been prepared by combustion synthesis in two reaction modes of self-propagating high-temperature synthesis (SHS) and thermal explosion (TE). The reaction mechanism in combustion synthesis is investigated and the effects of processing parameters are discussed. Two reaction paths are proposed for the formation of the Ti 1−x W x C solid solution. In path 1, Ti 1−x W x C crystals are directly precipitated from Ti-W-C melt, and in path 2 the Ti 1−x W x C phase is formed by solid-state reaction between TiC and WC. The availability of the two reaction paths depends on the x value and reaction temperature. For smaller x values and higher temperatures, the reaction path 1 dominates and almost full conversion is achieved. For larger x values and lower temperatures, however, path 2 becomes dominant. In path 2, the rate-limiting step is the formation of WC by slow diffusion-controlled solid-state reaction between W and C, which is unable to be completed during the short reaction period and results in the presence of W 2 C and unreacted W in the products. The reaction between W and C cannot be improved by the addition of excessive C, but can be promoted by using carbon black instead of graphite powder as C source or carrying out the synthesis in a high-pressure N 2 atmosphere instead of vacuum. In the fast combustion reaction with high heating/cooling rates, a non-equilibrium state is likely to be created because the mass transfer and energy exchange are limited. The non-equilibrium condition has a strong influence on the reaction kinetics, where the decomposition of W 2 C is avoided, a localized compositional heterogeneity is caused, and ultrafine grains on a submicron scale are obtained in the products. [ABSTRACT FROM AUTHOR]

Cu 2 SnSe 3 samples with different secondary phases are prepared from compositions of Cu x SnSe 3 (x=1.8–2.2) and Cu 2 Sn y Se 3 (y=0.8–1.2), and their thermoelectric properties are investigated. For Cu x SnSe 3 samples, the secondary phase is SnSe 2 for x=1.8 and 1.9 and SnSe for x=2.2, and nearly single-phase Cu 2 SnSe 3 is obtained for x=2.0 and 2.1. For Cu 2 Sn y Se 3 samples, the secondary phase is CuSe for y=0.8 and SnSe for x=1.1 and 1.2, and single-phase Cu 2 SnSe 3 is produced for y=0.9 and 1.0. The lattice structure of synthesized Cu 2 SnSe 3 depends on the x and y values, which is cubic for x≤2.0 or y≤1.0 and monoclinic for x>2.0 or y>1.0. Compared with the single-phase Cu 2 SnSe 3 sample (ZT=0.4 2 at 77 3 K), the samples with SnSe 2 secondary phase show a greatly-enhanced ZT of 0.84 at 773 K, which is likely the best result for un-doped Cu 2 SnSe 3 up to now. The samples with SnSe secondary phase exhibit poor thermoelectric properties. [ABSTRACT FROM AUTHOR]

Iron-based superconductor of FeSe 0.5 Te 0.5 has been prepared by chemical-furnace-assisted combustion synthesis. The chemical furnace preheats the reactant and enhances the reaction temperature, thus increasing the volume fraction of liquid and the solubility of Fe and improving the mass transfer. Accordingly, the chemical reaction and crystal growth are greatly promoted, resulting in higher compositional homogeneity, better crystallinity, and larger crystal size. The synthesized FeSe 0.5 Te 0.5 sample consists of two-dimensional thin slice crystals. It is proposed that, the slice crystal shape is derived from the intrinsic tetragonal lattice of FeSe 0.5 Te 0.5 , and forms by anisotropic crystal growth with fast growth in (001) face. The crystal growth of FeSe 0.5 Te 0.5 is also affected by cooling condition, and by control of the cooling condition lamellar crystals are produced with a thickness of about 1 mm and (001) preferred orientation. The transport properties of the synthesized FeSe 0.5 Te 0.5 sample have been investigated, showing an onset T c of about 13 K in the resistivity vs. temperature curve and a sharp drop of magnetic susceptibility at about 15 K. Compared with the conventional solid state reaction approach, chemical-furnace-assisted combustion synthesis may provide a more efficient way to prepare iron-based superconductors with much-reduced processing time and not requiring furnaces. [ABSTRACT FROM AUTHOR]

Abstract: Bulk YAG-based ceramics have been prepared by melt-casting under high gravity with the addition of glass. The glass helps to reduce the porosity and grain size of the casted ceramics. In the casting process, the glass melt can feed the shrinkage cavities produced during fast solidification of YAG. With the addition of glass, the grain boundary migration of YAG is pinned and thus grain growth is limited. The effect of the glass strongly depends on its chemical composition and crystallization behavior, where a higher SiO2 content is necessary to avoid devitrification. [Copyright &y& Elsevier]

A fast and furnace-free way is reported to synthesize ZnSe from self-sustained combustion reaction between Zn and Se. The synthesized ZnSe shows a zincblende structure and large particle size of > 100 μm, which can be reduced by two magnitude to 1.4 μm by using NaCl as diluent. It is proposed that the added NaCl can lower the reaction temperature and diminish the interfacial area of ZnSe grains by a steric hindrance effect. The ZnSe samples show the characteristic band-edge absorption in visible region, and the band gap energy is estimated to be 2.43–2.58 eV. Under an ultraviolet excitation, the ZnSe samples do not show the near-band-edge blue emission but exhibit strong red emission, which is likely related to the intrinsic point defects in ZnSe. Compared with previous studies, the ZnSe samples synthesized in this work show red emission peaks at even larger wavelength up to 730 nm. [ABSTRACT FROM AUTHOR]

Thermoelectric materials are attractive for solar thermal energy conversion and waste heat recovery. The existing methods for fabricating thermoelectric materials involve multi-step processes with considerable time and energy consumption. Here we report a fast and one-step way to prepare thermoelectric materials by gas-pressure or high-gravity assisted combustion synthesis. Dense Cu 2 SnSe 3 samples with a porosity below 2% were prepared from self-sustained combustion reaction of element powders. The electrical conductivity of the Cu 2 SnSe 3 samples was greatly enhanced and the thermal conductivity was reduced by partial substitution of Sn with In. The ZT values of the un-doped and In-doped Cu 2 SnSe 3 samples reached 0.51 and 0.62 at 773 K, respectively, which are comparable to the best results reported for Cu 2 SnSe 3 produced by other methods. Combustion synthesis offers an efficient way to prepare thermoelectric materials with reduced time and energy consumption, which may open up new possibilities for synthesis of thermoelectric materials. [ABSTRACT FROM AUTHOR]

Nitride based ceramics are considered as a kind of promising material for structural and functional integration due to their robust structure, extreme environmental resistance and electromagnetically transparency. It is still challenging to prepare nitride based ceramics with homogeneous and controllable microstructure because of their low self-diffusion coefficient and difficulty in sintering. Here, we developed a gelcasting-SHS process by combining gelcasting forming and self-propagating high temperature synthesis (SHS) for the preparation of porous BN-Si 3 N 4 composite ceramics. First, carbon residue problem in the gelcasting -SHS process was studied. Based on the result, porous BN-Si 3 N 4 composite ceramics with high porosity (69.42 ~ 86.48%), high strength (21.7 ~ 81.0 MPa) and low dielectric constants (1.42 ~ 2.87) were synthesized. In addition, the thermal shock resistance of porous BN-Si 3 N 4 composite ceramics until 1000 ℃ was evaluated. [ABSTRACT FROM AUTHOR]

A new method is reported for fast fabrication of W–Cr alloys by combustion synthesis under Ar gas pressure of 2 MPa. The W–Cr alloy with W/Cr=1 in atomic ratio shows a hierarchical microstructure consisting of both micro- and nano-sized grains, which is proposed to be produced by spinodal decomposition. The hierarchical microstructure contributes to an improved hardness of 9.6 GPa, which is about 50% higher than that of W–Cr alloys prepared by conventional powder sintering. [ABSTRACT FROM AUTHOR]

Abstract: Combustion synthesis (CS) of Si3N4 with the addition of polytetrafluoroethylene (PTFE) was carried out at a relatively low N2 pressure of 2MPa. It was found that the additive PTFE promoted the nitridation of Si. The α-Si3N4 contents in the periphery of the combustion-synthesized products showed great dependence on the contents of PTFE added in the reactants, which reached 77.7wt.% with 4wt.% PTFE addition. The residual silicon in the center of the combustion-synthesized products could be completely nitrided by further heat treatment at 1300°C for 1h in N2. The temperature difference between the center and the edge of the samples was responsible for the discrepancy in both phase composition and morphology of the products. [Copyright &y& Elsevier]

The preparation of MgO-stabilized ZrO 2 powders was based on combustion synthesis between Mg powders and CO 2 with ZrO 2 powders as the diluent. The effects of the diluent content on the combustion process parameters, phase composition, microstructure, and high-temperature stability were systemically investigated. As the diluent content increased, the reaction temperature, propagation velocity, and MgO content decreased. The reactant powders underwent different reaction processes and were transformed into different phase compositions due to the change in diluent content. The obtained MgO-stabilized ZrO 2 powders exhibited excellent high-temperature stability up to 1400 °C. [ABSTRACT FROM AUTHOR]

Porous β-Si 3 N 4 ceramics were prepared by combustion synthesis using Si, α-Si 3 N 4 and Y 2 O 3 powders as raw materials. The effects of α-Si 3 N 4 diluent content in pellet on nitriding rate, shrinkage, porosity and flexural strength of porous ceramics were investigated. The results show that porous β-Si 3 N 4 ceramic with porosity of 49 % and flexural strength of 151 MPa can be obtained by combustion synthesis when the content of α-Si 3 N 4 diluent in raw materials is equal to that of Si, and the linear shrinkage of porous ceramic is only 2.8 %. In addition, the porous ceramic can be drilled and turned by WC drill and turning tool respectively. [ABSTRACT FROM AUTHOR]

Abstract: A novel method for preparing Al2O3/ZrO2 (Y2O3) eutectic was developed by combining combustion synthesis with melt-casting under ultra-high gravity (CSMC-UHG). The application of UHG=800 g resulted in a high relative density of 99.8%, and an orientation-growth along the UHG direction. The microstructure was composed of aligned growth regimes containing a triangular dispersion of orderly ZrO2 rods in Al2O3 matrix with a spacing of 300nm. The eutectic had a high fracture toughness up to 17.9MPa·m1/2, which was mainly attributed to the nanostructure and the elastic bridge effects of the aligned ZrO2 rods. [Copyright &y& Elsevier]

Single-phase silicon oxynitride (Si 2 N 2 O) was prepared in a N 2 atmosphere by combustion synthesis with Si and SiO 2 as the reactants. The effects of process parameters, including N 2 pressure, Si 2 N 2 O diluent and NH 4 Cl content, on the combustion temperature, as well as phase composition and microstructure of products were investigated. The high-temperature wetting behavior of Si melt on the as-prepared Si 2 N 2 O coating was then tested by the sessile drop method. It was found that Si melt shows poor wettability to Si 2 N 2 O coating at 1500 °C with the steady contact angle of 120°, indicating that the combustion-synthesized Si 2 N 2 O powders could be used as a potential novel releasing agent material for photovoltaic silicon casting application. [ABSTRACT FROM AUTHOR]

Alpha phase silicon nitride (α-Si 3 N 4) powders were synthesized by combustion reaction of the in-situ nano-SiO 2 coated Si and Si 3 N 4 reactants with pressurized nitrogen. The combustion temperature profile as well as the product phase composition and morphology were investigated. Regardless of the combustion temperature reached as high as 1800 °C, up to 86 wt% α-Si 3 N 4 was obtained in the combustion-synthesized product from the reactants with only 6 wt% SiO 2 addition, which is three times higher than that of without SiO 2 coating, meanwhile, the morphology of Si 3 N 4 grains changed from rod-like to equiaxed grain，indicating the in-situ coated SiO 2 tailored the nitridation reaction path of Si successfully by enhancing the silicon monoxide (SiO) gas phase formation. [ABSTRACT FROM AUTHOR]

High crystalline hexagonal boron nitride nanoplates with high aspect ratio of ~400 have been synthesized by combustion synthesis method through magnesiothermic reduction reaction between B 2 O 3 and Mg in N 2 pressure. The synthesized hexagonal boron nitride nanoplates were about 50 nm in thickness and larger than 20 μm in lateral size. The six-fold symmetric spots electron diffraction pattern of transmission electron microscopy shows that the nanoplate is well crystallized. Hexagonal boron nitride nanoplates grow via an Oswald ripening process and have larger lateral size when it was prepared with larger magnesium particles. High temperature liquid magnesium provides an important environment for the growth and crystallization of boron nitride. This work provides an effective way to achieve low-cost and large-scale preparation of high-quality boron nitride nanoplates. [ABSTRACT FROM AUTHOR]

MgO/Graphene composites were prepared by combustion synthesis (CS) followed with spark plasma sintering (SPS) using LiF as sintering additive. The densification mechanism of MgO/Graphene composites doped with LiF was systematically investigated. With incorporating small amount of graphene into MgO, the spectral absorptivity of the composite was improved, whereas the density, hardness and average grain size were decreased. The densification of submicron sized MgO/Graphene ceramics was realized by the balance between sintering promoted by LiF and grain refinement of graphene. Unlabelled Image [ABSTRACT FROM AUTHOR]

High α-phase content Si 3 N 4 powders were fabricated by combustion synthesis method using coarse Si powder with NH 4 Cl additive. The effects of Si particle size and NH 4 Cl additive on the macrokinetic feature, phase composition, microstructure of combustion synthesized α-Si 3 N 4 powder were investigated. Without the addition of NH 4 Cl, the content of α-Si 3 N 4 in the products first decreases under a critical Si particle size of 7.8 μm, and then increases with increasing Si particle size. With the addition of 6 wt% NH 4 Cl, high α-phase content Si 3 N 4 powder (>90 wt%) was obtained by using coarse (19.6 μm) Si powder. The addition of NH 4 Cl reduces the maximum combustion temperature and retention time of liquid Si by promoting the gasification of Si, which lead to the increase of α-Si 3 N 4 content in the product. The use of coarse Si powder is of great significance for the low-cost production of high-quality α-Si 3 N 4 powder. [ABSTRACT FROM AUTHOR]

Abstract MgAl 2 O 4 -graphene composites have been fabricated from combustion synthesized ceramic-graphene powder mixtures by spark plasma sintering. The synthesis and dispersion of graphene was accomplished readily by a combustion reaction between Mg powders and CO 2 gas. Compared with that of pure MgAl 2 O 4 , the relative density decreases from 100% to 95.1% and the average grain size decreases from 94 to 0.4 µm for composites containing 2.5 wt% graphene. The bending strength and fracture toughness of the as-prepared MgAl 2 O 4 -graphene composites increased by 34% (from 217 to 291 MPa) and 32% (from 1.91 to 2.52 MPa m1/2) at 0.5 wt% graphene content. The prepared MgAl 2 O 4 -graphene composites may provide an alternative refractory material to withstand harsh environments. [ABSTRACT FROM AUTHOR]

Highlights • The gradient composite was prepared by combustion synthesis. • The gradient ceramic/metal composite of TiC-TiB 2 /Al 0.3 CoCrFeNi. • In-situ ceramics of TiC-TiB 2 have a gradient distribution in the matrix. • The hardness of the composite material is a gradient distribution. Abstract The gradient ceramic/metal composite of TiC-TiB 2 /Al 0.3 CoCrFeNi was prepared by combustion synthesis under ultra-high gravity field. Right after the formation of the mixture by combustion, the ceramics and metals are separated in an ultra-gravity field due to the difference in mass density, resulted in a gradient distribution of ceramics (TiC-TiB 2) along the gravitational field in the high-entropy alloy (Al 0.3 CoCrFeNi) matrix. The hardness of the material shows a significant gradient change. [ABSTRACT FROM AUTHOR]

ZrN and AlN nitride ceramic powders have been synthesized by combustion synthesis using Si 3 N 4 and BN as solid nitrogen sources. The experimental results show that the metallic particles of Zr and Al are fully nitridized by the solid nitrogen sources and are converted into ZrN and AlN. Zr reacts with both Si 3 N 4 and BN in a self-sustained way, while Al reacts only with Si 3 N 4 and does not react with BN. By using Si 3 N 4 and BN as solid nitridizing agents, this work provides an alternative way to synthesize the nitrides of ZrN and AlN, which differs from the conventional nitridation method using N 2 gas as a nitridizing agent. [ABSTRACT FROM AUTHOR]

ZTA-TiC-FeCrNi cermets are prepared by a fast and furnace-free way called high-gravity combustion synthesis. The synthesized cermet samples show the maximum relative density of 97.6% and a hierarchical microstructure with grain sizes from submicron to >50 µm. The content of TiC has a strong influence on the microstructure and mechanical properties of the cermet samples. A higher TiC content results in refined microstructure, improved hardness, and reduced coefficient of friction. With increasing TiC content, the strength and toughness of the samples first increase and then drops, and reach the maximum of 469±26 MPa and 11.3±0.2 MPa m 1/2 at 20% TiC. Compared with commercial polycrystalline Al 2 O 3 ceramics, the ZTA-TiC-FeCrNi cermets exhibit better wear resistance, and the volume loss is lower by one magnitude than Al 2 O 3 under the same condition. [ABSTRACT FROM AUTHOR]

A fast and furnace-free method of combustion synthesis is employed for the first time to synthesize iron-based superconductors. Using this method, Fe 1.1 Se 1 − x Te x (0 ≤ x ≤ 1) samples can be prepared from self-sustained reactions of element powders in only tens of seconds. The obtained Fe 1.1 Se 1 − x Te x samples show clear zero resistivity and corresponding magnetic susceptibility drop at around 10–14 K. The Fe 1.1 Se 0.33 Te 0.67 sample shows the highest onset T c of about 14 K, and its upper critical field is estimated to be approximately 54T. Compared with conventional solid state reaction for preparing polycrystalline FeSe samples, combustion synthesis exhibits much-reduced time and energy consumption, but offers comparable superconducting properties. It is expected that the combustion synthesis method is available for preparing plenty of iron-based superconductors, and in this direction further work is being in progress. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel method was developed for the in suit synthesis and bonding of Cu to W–Cu composite by combining combustion synthesis and centrifugal infiltration. [•] Composition and microstructure showed a layered variation along high gravity direction. [•] Columnar grain microstructure was observed on Cu layer due to a fast cooling rate produced along high gravity. [•] The evolution of thermal conductivity and hardness along high gravity direction were investigated. [ABSTRACT FROM AUTHOR]

Abstract: Reactants were pelletized, and then combustion synthesis of Si3N4 powder was achieved under the N2 pressure of 3.0MPa. Effects of the pelletization of reactants and Si3N4 diluents on the combustion process parameters and the characteristics of products were studied. The combustion mode of single reactant pellet was preliminarily discussed. The results indicated that the combustion reaction of single pellet was layer-by-layer from the surface to the core, which led to two peaks on the combustion temperature variation waves. With increasing the diluents content, the morphologies of Si3N4 particles changed from short rods into equiaxed grains, and residual Si in the final products obviously decreased. Single phase β-Si3N4 powder mainly contained equiaxed grains was prepared when 58wt.% diluents was added. [Copyright &y& Elsevier]

Abstract: This paper studied the high temperature self-propagating synthesis of W–Ni graded alloy under ultra-high gravity field. The evolution of composition and microstructure along ultra-high gravity direction was investigated. In this W–Ni alloy, ultra-high reaction temperature resulted in the production of stable ordered Ni4W phase, and ultra-high gravity field promoted the formation of W–Ni graded alloy. Composition and microstructure exhibited a graded variation along the ultra-high gravity direction, and three functional gradients formed on the cross section. The Ni-rich layer was mainly enhanced by the Ni4W phase, while the W-rich layer was primarily reinforced by the W particles. Between them, the transitional layer served as the buffer zone of thermal expansion to relax the thermal stress. [Copyright &y& Elsevier]