Papers by Keyword: Carbothermal Reduction Nitridation

Abstract: Sialon-SiC composite powders were synthesized from kyanite tailings through the carbothermal reduction nitridation (CRN) technique. Using Sialon-SiC composites to substitute Si₃N₄ composites via the CRN technique synthesize Sialon/Si₃N₄-SiC composite refractories. The phase composition, cross section morphology, and the substituent amount of Sialon-SiC composites impact on refractories mechanical properties were investigated, respectively. The optimized synthesis temperature for the CRN reaction was found to be 1550 °C for 4 h with the excess carbon 20%. The substituent amount of Sialon-SiC was 25%, the mechanical properties of Sialon/Si₃N₄-SiC composite refractories reached optimal performance, which bending strength value was 41.8 MPa and compression strength value was 61.6 MPa.

Abstract: β-Sialonwhiskers which the molecular structuralformula of β-Sialonis Si₃Al₃O₃N₅(z = 3) were synthesized from fly ash and graphite under appropriate technological conditions by carbothermal reduction–nitridation process. The effects of carbon content, reaction temperature and reaction time on synthesis ofβ-Sialonwere analysed by XRD, SEM techniques. The results proved that, the condition of the carbon content over 80% is the best parameter to promote theβ-Sialon powder production. Compared to other kinds of temperature, 1430 °C is the optimal temperature to promoteβ-Sialon powder generation. Compared to 3h, holding time of 6h is promoting theβ-Sialon powder generation.The main morphology of β-Sialon was rod-like whisker.

Abstract: Silicon nitride (β-Si₃N₄) nano-belts had been synthesized by used silica bricks and carbon powder as raw materials through carbothermal reduction nitridation. The morphology and microstructure of β-Si₃N₄ nano-belts were characterized by scanning electron microscopy (SEM/HRSEM), energy disperse spectrum (EDS) and X-ray diffraction (XRD). Results showed that the well-crystallized β-Si₃N₄ nano-beltes were grown with thinness of 50-150nm and width of 3-5μm. The relatively purer β-Si₃N₄ were prone to be thin films with thinness of 150nm, while the as-grown SiCN (impurityβ-Si₃N₄with C elements) were presented as nanorods with cross section length of 150*150nm. Orientation growth mechanism by grain dislocation and vapor-solid (VS) mechanism were both involved in the growth of nanostructures of β-Si₃N₄ nano-beltes and SiCN nanorods.

Abstract: Ti(C,N) powder was prepared via carbothermal reduction nitridation (CRN) using rutile and carbon black as the raw material. The phase evolution and the reaction mechanism during the CRN synthesis of Ti(C,N) were investigated, and the effect of reaction temperature and C/TiO₂ molar ratio on the phase composition and x value in TiC_1–xN_x was analyzed. The XRD and SEM results show that: Ti(C,N) powder was synthesized at 1500°C for 4h with the C/TiO₂ molar ratio of 2.2, under the nitrogen pressure of 0.2MPa. Irregular granular structure and the growth stripes were observed in the final products. The growth of Ti(C,N) grains in CRN process was followed by the gas-solid mechanism.The phase compositions of the products were quite dependent on the reaction temperature and the C/TiO₂ molar ratio. The TiN content in Ti(C,N) decreased with the increase of reaction temperature. TiC_1–xN_x powder with different x values can be synthesized by optimizing the experiment conditions including the synthesis temperature and the C/TiO₂ molar ratio.

Abstract: Sialon-based eco-materials were synthesized by using the gold mineral tailings that containing abundant Si and Al elements as the major raw material with minor additives through the carbothermal reduction nitridation route. This study realized the conversion of eco-materials from solid waste, gold mineral tailings. The effects of sintering temperature, holding time and x value during carbothermal reduction nitridation process on the phase composition and microstructure of as-fabricated Sialon-based materials were explored. The XRD results indicated that when sintering temperature is 1550°C, holding time is 6h, and x value is 1.0, Ca-α-Sialon/SiC/Fe₃Si composites was successfully synthesized. The relative content _{Subscript text}of each phase in the products is I(α-Sialon): I(SiC): I(Fe₃Si)=82:10:8. The SEM images showed the densificated microstructure and uniform grains with the long column shape.

Abstract: Rutile and fly ash powders were nitridized at different temperatures for 4 h. The influence of temperature on phase composition of nitridation products from rutile and fly ash was studied. XRD, SEM and EDS analyses show that: the phase compositions of the products was quite dependent on the reaction temperature. Mullite, O'-Sialon and X-Sialon were formed from 1400 °C to 1450 °C. Rising temperature would get Mullite nitrided. Meanwhile, O'-Sialon and X-Sialon would be nitrided and transformed into β-Sialon. At temperatures above 1550 °C, the main phases of the products were hexagonal columnar β-Sialon and irregular TiC_0.3N_0.7 grains.

Abstract: The chemical composition, phase constituents and microstructure of gasification slag from Texaco gasifier, the carbothermal reduction nitridation of gasification slag were investigated by X-ray fluorescence spectrometry, X-ray diffractometry and scanning electron microscopy. The effect of nitridation temperature on the phase composition and morphology of nitridation reaction products was studied. Ca-α-sialon—SiC multiphase ceramics were fabricated and characterized. The results showed that: The coal gasification slag was an ideal raw material to synthesize Sialon powder. When introducing 3wt%Y₂O₃+2wt% MgO into sialon powder carbothermally synthesized at 1450°C, the Vickers hardness and fracture toughness of Sialon-SiC multiphase ceramics hot-pressed at 1650 °C were 18.6 GPa and 5.2 MPa·m^1/2, respectively.