The behavior of gaseous nitriding on the surface nanocrystallized (SNCed) steel was investigated. The mild steel discs were SNCed on one side by using the method of ultrasonic shot peening. The opposite side of the di...The behavior of gaseous nitriding on the surface nanocrystallized (SNCed) steel was investigated. The mild steel discs were SNCed on one side by using the method of ultrasonic shot peening. The opposite side of the discs maintained the original coarse-grained condition. The gaseous nitriding was subsequently carried out at three different temperatures: 460, 500 and 560℃. The compound layer growth and diffusion behavior were then studied. It was revealed that SNC pretreatment greatly enhances both diffusion coefficient D and surface reaction rate. As a result, nitriding time could be reduced to the half. It was also found that the growth of compound layer with nitriding time conformed with parabolic relationship from the start of nitriding process in the SNCed samples.展开更多
In this paper,Si3N4 fiber materials were fabricated by nitridation of porous Si green bodies,which were prepared by the foaming method combined with gel-casting.The effect of the nitriding process(the heating rate and...In this paper,Si3N4 fiber materials were fabricated by nitridation of porous Si green bodies,which were prepared by the foaming method combined with gel-casting.The effect of the nitriding process(the heating rate and the nitrogen flow rate)on the phase and the microstructure was studied.The results show that decreasing the heating rate and the nitrogen flow rate is both beneficial to the growth of Si3N4 nanofibers and promoting the disintegration of the pore wall structure of the porous green bodies.The optimized nitrogen flow rate and the heating rate for the growth of silicon nitride fibers are 150 mL/min and 0.5℃/min,respectively.展开更多
β-Sialon/ZrN bonded corundum composites were synthesized using fused white corundum,alumina micro powder,zircon and carbon black by nitridation reaction sintering process. Phase composition and microstructure of the ...β-Sialon/ZrN bonded corundum composites were synthesized using fused white corundum,alumina micro powder,zircon and carbon black by nitridation reaction sintering process. Phase composition and microstructure of the synthesized composites were investigated by X-ray powder diffraction and scanning electronic microscope,and the formation process of the composites was discussed. The results show that the composites with different compositions can be obtained by controlling the heating temperature and contents of zircon and carbon black. The proper temperature to synthesize the composites is 1773 K.展开更多
Graphite-phase polymeric carbon nitride （CN） was reported to be a promising material in photoelectrochemical solar energy conversion. However, its high recombination rate of photogenerated carriers limits its potent...Graphite-phase polymeric carbon nitride （CN） was reported to be a promising material in photoelectrochemical solar energy conversion. However, its high recombination rate of photogenerated carriers limits its potential applications. In this article, a heterojunction of CN and sulfur-doped CN （CNS） was constructed through a solution-based processing way. Interestingly, it was observed that the photocatalytic hydrogen production of the as-prepared composite was 32.6 times higher than that of bulk carbon nitride and 2.3 times higher than that of the composites by conventional impregnating method. This study opens a new avenue to construct heterojunction of CN for large-scale industrial applications in environmental remediation.展开更多
文摘The behavior of gaseous nitriding on the surface nanocrystallized (SNCed) steel was investigated. The mild steel discs were SNCed on one side by using the method of ultrasonic shot peening. The opposite side of the discs maintained the original coarse-grained condition. The gaseous nitriding was subsequently carried out at three different temperatures: 460, 500 and 560℃. The compound layer growth and diffusion behavior were then studied. It was revealed that SNC pretreatment greatly enhances both diffusion coefficient D and surface reaction rate. As a result, nitriding time could be reduced to the half. It was also found that the growth of compound layer with nitriding time conformed with parabolic relationship from the start of nitriding process in the SNCed samples.
基金This work was supported by the National Natural Science Foundation of China(NSFC-No.51672256)National Natural Science Foundation of China-Key Projects of Henan United Fund(NSFC-No.U1904217).
文摘In this paper,Si3N4 fiber materials were fabricated by nitridation of porous Si green bodies,which were prepared by the foaming method combined with gel-casting.The effect of the nitriding process(the heating rate and the nitrogen flow rate)on the phase and the microstructure was studied.The results show that decreasing the heating rate and the nitrogen flow rate is both beneficial to the growth of Si3N4 nanofibers and promoting the disintegration of the pore wall structure of the porous green bodies.The optimized nitrogen flow rate and the heating rate for the growth of silicon nitride fibers are 150 mL/min and 0.5℃/min,respectively.
基金Project(50274021) supported by the National Natural Science Foundation of China and Baoshan Iron and Steel Co., Ltd.
文摘β-Sialon/ZrN bonded corundum composites were synthesized using fused white corundum,alumina micro powder,zircon and carbon black by nitridation reaction sintering process. Phase composition and microstructure of the synthesized composites were investigated by X-ray powder diffraction and scanning electronic microscope,and the formation process of the composites was discussed. The results show that the composites with different compositions can be obtained by controlling the heating temperature and contents of zircon and carbon black. The proper temperature to synthesize the composites is 1773 K.
基金financially supported in part by the National Natural Science Foundation of China(No. 21305065)Natural Science Foundation of Jiangsu Province(Nos. BK20160028, BK20170084)+1 种基金the Open Funds of the State Key Laboratory of Electroanalytical Chemistry (No. SKLEAC201703)the Fundamental Research Funds for the Central Universities
文摘Graphite-phase polymeric carbon nitride （CN） was reported to be a promising material in photoelectrochemical solar energy conversion. However, its high recombination rate of photogenerated carriers limits its potential applications. In this article, a heterojunction of CN and sulfur-doped CN （CNS） was constructed through a solution-based processing way. Interestingly, it was observed that the photocatalytic hydrogen production of the as-prepared composite was 32.6 times higher than that of bulk carbon nitride and 2.3 times higher than that of the composites by conventional impregnating method. This study opens a new avenue to construct heterojunction of CN for large-scale industrial applications in environmental remediation.
