Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering （ LPS ）. The Si2 N2O phase was generated by an in-situ reaction 2 Si3 N4 （ s ） ＋ 1.5 02 （ g...Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering （ LPS ）. The Si2 N2O phase was generated by an in-situ reaction 2 Si3 N4 （ s ） ＋ 1.5 02 （ g ） = 3 Si2 N2O （ s ） ＋ N2 （ g ） . The content of Si2 N2 O phase up to 60% in the volume was obtained at a sintering temperature of 1 650℃ and reduced when the sintering temperature increased or decreased, indicating the reaction is reversible. The mass loss, relative density and average grain size increased with increasing the sintering temperature. The average grain size was less than 500 nm when the sintering temperature was below 1 700 ℃. The sintering procedure contains a complex crystallization and a phase transition ： amorphous silicon nitride→equiaxial α- Si3 N4→ equiaxial β- Si3 N4→ rod- like Si2 N2O→ needle- like β- Si3N4 . Small round-shaped β→ Si3 N4 particles were entrapped in the Si2 N2O grains and a high density of staking faults was situated in the middle of Si2 N2O grains at a sintering temperature of 1 650 ℃. The toughness inereased from 3.5 MPa·m^1/2 at 1 600 ℃ to 7.2 MPa· m^1/2 at 1 800 ℃ . The hardness was as high as 21.5 GPa （Vickers） at 1 600 ℃ .展开更多
将工业偏钛酸浆料和尿素混合均匀后高温煅烧制备g-C3N4/TiO2光催化复合材料,对其结构进行了表征,以NO为目标物、波长430~470 nm的12 W LED灯为光源,用对NO的去除率评价复合材料的气相光催化活性.结果表明,所制样品为氮掺杂Ti O2与g-C3N4...将工业偏钛酸浆料和尿素混合均匀后高温煅烧制备g-C3N4/TiO2光催化复合材料,对其结构进行了表征,以NO为目标物、波长430~470 nm的12 W LED灯为光源,用对NO的去除率评价复合材料的气相光催化活性.结果表明,所制样品为氮掺杂Ti O2与g-C3N4/TiO2的复合物.复合材料的最佳制备条件为尿素与偏钛酸质量比2：1,450℃下煅烧1 h,该条件下样品产率最高,对NO的去除率达48.40%.展开更多
Using low-cost precipitated silica(SiO2) as the carrier,a ternary SiO2-TiO2/g-C3N4 composite photocatalyst was prepared via the sol-gel method associated with a wet-grinding process.The asprepared composite exhibits p...Using low-cost precipitated silica(SiO2) as the carrier,a ternary SiO2-TiO2/g-C3N4 composite photocatalyst was prepared via the sol-gel method associated with a wet-grinding process.The asprepared composite exhibits photocatalytic hydrogen production and pollutant degradation performance under solar-like irradiation.The effect of SiO2 carrier on the properties of the heterostructure between TiO2 and g-C3N4(CN) was systematically studied.It is found that SiO2 has important effects on promoting the interaction between TiO2 and CN.The particle size of TiO2 and CN was obviously reduced during the calcination process due to the effects of SiO2.Especially,the TiO2 particles exhibit monodispersed state with particle size below 10 nm(quantum dots),resulting in the improvement of the contact area and the interaction betweenTiO2 and CN,and leading to the formation of efficient TiO2/CN Zscheme heterostructure in SiO2-TiO2/CN.Besides,the introduction of SiO2 can increase the specific surface area and light absorption of SiO2-TiO2/CN,further promoting the photocatalytic reaction.As expected,the optimum SiO2-TiO2/CN composite exhibits 12.3,3.1 and 2.9 times higher photocatalytic hydrogen production rate than that of SiO2-TiO2,CN and TiO2/CN under solar-like irradiation,while the photocatalytic active component in SiO2-TiO2/CN is only about 60 wt%.Moreover,the rhodamine B degradation rate of SiO2-TiO2/CN is also higher than that of SiO2-TiO2,CN and TiO2/CN.展开更多
基金Funded by the National Science Foundation of China ( No.50375037)
文摘Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering （ LPS ）. The Si2 N2O phase was generated by an in-situ reaction 2 Si3 N4 （ s ） ＋ 1.5 02 （ g ） = 3 Si2 N2O （ s ） ＋ N2 （ g ） . The content of Si2 N2 O phase up to 60% in the volume was obtained at a sintering temperature of 1 650℃ and reduced when the sintering temperature increased or decreased, indicating the reaction is reversible. The mass loss, relative density and average grain size increased with increasing the sintering temperature. The average grain size was less than 500 nm when the sintering temperature was below 1 700 ℃. The sintering procedure contains a complex crystallization and a phase transition ： amorphous silicon nitride→equiaxial α- Si3 N4→ equiaxial β- Si3 N4→ rod- like Si2 N2O→ needle- like β- Si3N4 . Small round-shaped β→ Si3 N4 particles were entrapped in the Si2 N2O grains and a high density of staking faults was situated in the middle of Si2 N2O grains at a sintering temperature of 1 650 ℃. The toughness inereased from 3.5 MPa·m^1/2 at 1 600 ℃ to 7.2 MPa· m^1/2 at 1 800 ℃ . The hardness was as high as 21.5 GPa （Vickers） at 1 600 ℃ .
基金partly supported by the National Natural Science Foundation of China(Nos.21577132,21978276)。
文摘Using low-cost precipitated silica(SiO2) as the carrier,a ternary SiO2-TiO2/g-C3N4 composite photocatalyst was prepared via the sol-gel method associated with a wet-grinding process.The asprepared composite exhibits photocatalytic hydrogen production and pollutant degradation performance under solar-like irradiation.The effect of SiO2 carrier on the properties of the heterostructure between TiO2 and g-C3N4(CN) was systematically studied.It is found that SiO2 has important effects on promoting the interaction between TiO2 and CN.The particle size of TiO2 and CN was obviously reduced during the calcination process due to the effects of SiO2.Especially,the TiO2 particles exhibit monodispersed state with particle size below 10 nm(quantum dots),resulting in the improvement of the contact area and the interaction betweenTiO2 and CN,and leading to the formation of efficient TiO2/CN Zscheme heterostructure in SiO2-TiO2/CN.Besides,the introduction of SiO2 can increase the specific surface area and light absorption of SiO2-TiO2/CN,further promoting the photocatalytic reaction.As expected,the optimum SiO2-TiO2/CN composite exhibits 12.3,3.1 and 2.9 times higher photocatalytic hydrogen production rate than that of SiO2-TiO2,CN and TiO2/CN under solar-like irradiation,while the photocatalytic active component in SiO2-TiO2/CN is only about 60 wt%.Moreover,the rhodamine B degradation rate of SiO2-TiO2/CN is also higher than that of SiO2-TiO2,CN and TiO2/CN.
