Si3N4 powder was synthesized by carbothermal re- duction nitridation reaction using sawdust as carbon source and introducing SiO2 by silica sol immersion. Effects of SiO2 content of silica sol, molding pressure, react...Si3N4 powder was synthesized by carbothermal re- duction nitridation reaction using sawdust as carbon source and introducing SiO2 by silica sol immersion. Effects of SiO2 content of silica sol, molding pressure, reaction temperature, reaction duration, and N2 flow rate on phase compositions and microstructure of result- ants were studied. The results show that using 7. 5 mass% SiO2 containing silica sol immersed sawdust as raw materials, the prepared Si3N4 powder is featured with high α-Si3N4 content, few impurities, etc. in the conditions of 1 450 ℃ of reaction temperature, 9 h of reaction duration, 400 mL ·min- 1 of N2 flow rate and 10 MPa of molding pressure.展开更多
By carbothermal reduction of Mg O with black carbon as reduction agent at a high temperature,Mg O was deposited on the surface of Mg O- Ca O clinker（ as coating） to improve the clinker ＇s hydration resistance. In t...By carbothermal reduction of Mg O with black carbon as reduction agent at a high temperature,Mg O was deposited on the surface of Mg O- Ca O clinker（ as coating） to improve the clinker ＇s hydration resistance. In the paper,effect of deposition temperature and holding time on the hydration resistance of the treated Mg O-Ca O,the deposition mechanism and Mg O coating kinetics were investigated with hydration resistance test,X-ray diffractometry（ XRD） and scanning electronic microscope（ SEM）. Results showed Mg O coating grew in a2D mode on the surface of Mg O- Ca O particles; the Mg O coating improved the hydration resistance of the coated Mg O- Ca O clinker,and the coated clinker would become stronger when coated at higher deposition temperature and longer holding time. The measurements also found that Mg O deposition process varied with the deposition temperature： it was mainly a chemical-controlled process at temperatures between 1 400- 1 500 ℃,with an apparent activation energy（ AAE） of 97. 8kJ·mol^（-1）; it would change into a diffusion-controlled process when the temperature rising to 1 500- 1 600 ℃,with apparent activation energy of 19. 2kJ·mol^（-1）.展开更多
文摘Si3N4 powder was synthesized by carbothermal re- duction nitridation reaction using sawdust as carbon source and introducing SiO2 by silica sol immersion. Effects of SiO2 content of silica sol, molding pressure, reaction temperature, reaction duration, and N2 flow rate on phase compositions and microstructure of result- ants were studied. The results show that using 7. 5 mass% SiO2 containing silica sol immersed sawdust as raw materials, the prepared Si3N4 powder is featured with high α-Si3N4 content, few impurities, etc. in the conditions of 1 450 ℃ of reaction temperature, 9 h of reaction duration, 400 mL ·min- 1 of N2 flow rate and 10 MPa of molding pressure.
基金supported by The Industrial Research Project of Shaanxi Province , China under Grant No. 2012k07-07
文摘By carbothermal reduction of Mg O with black carbon as reduction agent at a high temperature,Mg O was deposited on the surface of Mg O- Ca O clinker（ as coating） to improve the clinker ＇s hydration resistance. In the paper,effect of deposition temperature and holding time on the hydration resistance of the treated Mg O-Ca O,the deposition mechanism and Mg O coating kinetics were investigated with hydration resistance test,X-ray diffractometry（ XRD） and scanning electronic microscope（ SEM）. Results showed Mg O coating grew in a2D mode on the surface of Mg O- Ca O particles; the Mg O coating improved the hydration resistance of the coated Mg O- Ca O clinker,and the coated clinker would become stronger when coated at higher deposition temperature and longer holding time. The measurements also found that Mg O deposition process varied with the deposition temperature： it was mainly a chemical-controlled process at temperatures between 1 400- 1 500 ℃,with an apparent activation energy（ AAE） of 97. 8kJ·mol^（-1）; it would change into a diffusion-controlled process when the temperature rising to 1 500- 1 600 ℃,with apparent activation energy of 19. 2kJ·mol^（-1）.
