The feasibility of 5 kg β-SiC synthesized in one batch was demonstrated through igniting the mixture of Si, C-black and polytetrafluoroethylene （PTFE） under different nitrogen pressures. The effect of experimental ...The feasibility of 5 kg β-SiC synthesized in one batch was demonstrated through igniting the mixture of Si, C-black and polytetrafluoroethylene （PTFE） under different nitrogen pressures. The effect of experimental parameters, including the contents of PTFE, nitrogen pressure, preheating, and raw materials distribution forms were investigated. The results show that the products are β-SiC with equiaxed grains. The average grain size is less than 200 nm. The powders loaded loosely promote reaction heat dispersing, resulting in small grains. High purity β-SiC powders are obtained when the PTFE content is as low as 5wt%, which simplifies the process and decreases the cost effectively. The ceramic sintered from the obtained β-SiC powders presents the hardness of 22.20 GPa, the bending strength as high as 715.15 MPa and the fracture toughness of 8.179 MPa·m^1/2, which are higher than those of ceramics fabricated with α-SiC produced by combustion synthesis.展开更多
A Self-Propagating Combustion Synthesis (SPCS) method, citrate SPCS method, was used to synthesize crystalline powders of La-substituted barium hexaferrit, according to the formula Ba1-xLaxFe11.5Cr0.5O19(x=0～0.25). T...A Self-Propagating Combustion Synthesis (SPCS) method, citrate SPCS method, was used to synthesize crystalline powders of La-substituted barium hexaferrit, according to the formula Ba1-xLaxFe11.5Cr0.5O19(x=0～0.25). The structures, morphologies and ferromagnetic properties of La3+ substituted composites were characterized by powder X-Ray Diffractometer (XRD), Transmission Electron Microscope (TEM) and Vibrating Sample Magnetometer (VSM). XRD results showed that it was possible to obtain single-phase barium ferrite powders at 1100 ℃ and La content x<0.2. From the SEM, it was observed that the particles calcined at 1100 ℃ had a plate-like hexagonal shape. The results of magnetic mensuration revealed that the magnetic properties of La-substituted samples were obviously affected by La content .With the increasing of the La content, the saturation magnetization of Ba1-xLaxFe11.5Cr0.5O19 (x=0～0.25) increased from 50.1 to 56.2 emu·g-1, and coercivity increased from 1411.1 Oe to 1544.6 Oe.展开更多
以甘氨酸为络合剂,采用低温自蔓延燃烧法合成La和Nd共掺杂Bi Fe O_(3)(Bi_(0.9-x)La_(0.1)Nd_xFe O_(3),x=0.1,0.2,0.3,0.4,at%)陶瓷粉体,利用X射线衍射(XRD)、漫反射光谱(DRS)、扫描电镜(SEM)和傅里叶红外光谱(FT-IR)等技术分析产物的...以甘氨酸为络合剂,采用低温自蔓延燃烧法合成La和Nd共掺杂Bi Fe O_(3)(Bi_(0.9-x)La_(0.1)Nd_xFe O_(3),x=0.1,0.2,0.3,0.4,at%)陶瓷粉体,利用X射线衍射(XRD)、漫反射光谱(DRS)、扫描电镜(SEM)和傅里叶红外光谱(FT-IR)等技术分析产物的相组成和微观结构。结果表明:与传统固相反应法相比,低温自蔓延燃烧法的合成温度大幅降低到600℃。当La和Nd元素的掺杂量不高于30 at%时,合成的陶瓷粉体为单一的四方钙钛矿结构,固溶极限有所提高。600℃煅烧2 h所得产物的颗粒平均尺寸约为27 nm,且分散性良好。La和Nd共掺杂可以有效降低Bi Fe O_(3)的禁带宽度,提高可见光的利用率。采用低温自蔓延合成的La和Nd共掺杂Bi Fe O_(3)在铁电陶瓷和光催化材料方面具有一定的应用价值。展开更多
文摘The feasibility of 5 kg β-SiC synthesized in one batch was demonstrated through igniting the mixture of Si, C-black and polytetrafluoroethylene （PTFE） under different nitrogen pressures. The effect of experimental parameters, including the contents of PTFE, nitrogen pressure, preheating, and raw materials distribution forms were investigated. The results show that the products are β-SiC with equiaxed grains. The average grain size is less than 200 nm. The powders loaded loosely promote reaction heat dispersing, resulting in small grains. High purity β-SiC powders are obtained when the PTFE content is as low as 5wt%, which simplifies the process and decreases the cost effectively. The ceramic sintered from the obtained β-SiC powders presents the hardness of 22.20 GPa, the bending strength as high as 715.15 MPa and the fracture toughness of 8.179 MPa·m^1/2, which are higher than those of ceramics fabricated with α-SiC produced by combustion synthesis.
基金the Science and Technology Key Project of Zhejiang Province (2006C21080)Zhejiang Provincial Natural Science Foundation of China (Y405038)
文摘A Self-Propagating Combustion Synthesis (SPCS) method, citrate SPCS method, was used to synthesize crystalline powders of La-substituted barium hexaferrit, according to the formula Ba1-xLaxFe11.5Cr0.5O19(x=0～0.25). The structures, morphologies and ferromagnetic properties of La3+ substituted composites were characterized by powder X-Ray Diffractometer (XRD), Transmission Electron Microscope (TEM) and Vibrating Sample Magnetometer (VSM). XRD results showed that it was possible to obtain single-phase barium ferrite powders at 1100 ℃ and La content x<0.2. From the SEM, it was observed that the particles calcined at 1100 ℃ had a plate-like hexagonal shape. The results of magnetic mensuration revealed that the magnetic properties of La-substituted samples were obviously affected by La content .With the increasing of the La content, the saturation magnetization of Ba1-xLaxFe11.5Cr0.5O19 (x=0～0.25) increased from 50.1 to 56.2 emu·g-1, and coercivity increased from 1411.1 Oe to 1544.6 Oe.
文摘以甘氨酸为络合剂,采用低温自蔓延燃烧法合成La和Nd共掺杂Bi Fe O_(3)(Bi_(0.9-x)La_(0.1)Nd_xFe O_(3),x=0.1,0.2,0.3,0.4,at%)陶瓷粉体,利用X射线衍射(XRD)、漫反射光谱(DRS)、扫描电镜(SEM)和傅里叶红外光谱(FT-IR)等技术分析产物的相组成和微观结构。结果表明:与传统固相反应法相比,低温自蔓延燃烧法的合成温度大幅降低到600℃。当La和Nd元素的掺杂量不高于30 at%时,合成的陶瓷粉体为单一的四方钙钛矿结构,固溶极限有所提高。600℃煅烧2 h所得产物的颗粒平均尺寸约为27 nm,且分散性良好。La和Nd共掺杂可以有效降低Bi Fe O_(3)的禁带宽度,提高可见光的利用率。采用低温自蔓延合成的La和Nd共掺杂Bi Fe O_(3)在铁电陶瓷和光催化材料方面具有一定的应用价值。
