The synthesis and dielectric properties of calcium titanate （CaTiO3） submicron powder synthesized by mechanical ball-milling method have been investigated in this paper. With the ball-milling time increased, the siz...The synthesis and dielectric properties of calcium titanate （CaTiO3） submicron powder synthesized by mechanical ball-milling method have been investigated in this paper. With the ball-milling time increased, the size of CaTiO3 particles decreased from micron to submicron, and a great deal of nanoparticles （50-100 nm） occurred. The CaTiO3 ceramics made from submicron powders achieved compact structure at the sintering temperature of 1 250℃, and had good dielectric properties： εr=171, Q×f= 4 361 GHz, τf =＋782 ppm/＋C, IR=6.5×10^12Ω, which was a similar result compared with the CaTiO3 ceramics made from nanoparticles by sol-gel method.展开更多
Base metal nickel is often used as the inner electrode in multilayer chip positive temperature coefficient resistance （PTCR）. The fine grain of ceramic powders and base metal nickel are necessary. This paper uses re...Base metal nickel is often used as the inner electrode in multilayer chip positive temperature coefficient resistance （PTCR）. The fine grain of ceramic powders and base metal nickel are necessary. This paper uses reducing hydrazine to gain submicron nickel powder whose diameter was 200-300 nm through adjusting the consumption of nucleating agent PVP properly. The submicron nickel powder could disperse well and was fit for co--fired of multilayer chip PTCR. It analyes the submicron nickel powder through x-ray Diffraction （XRD） and calculates the diameter of nickel by PDF cards. Using XRD analyses it obtains several conclusions： If the molar ratio of hydrazine hydrate and nickel sulfate is kept to be a constant, when enlarging the molar ratio of NaOH/Ni^2＋, the diameter of nickel powder would become smaller. When the temperature in the experiment raises to 70-80 ℃, nickel powder becomes smaller too. And if the molar ratio of NaOH/Ni2＋ is 4, when molar ratio of （C2H5O）2/Ni^2＋ increases, the diameter of nickel would reduce. Results from viewing the powders by optical microscope should be the fact that the electrode made by submicron nickel powder has a better formation and compactness. Furthermore, the sheet resistance testing shows that the electrode made by submicron nickel is smaller than that made by micron nickel.展开更多
A new cement free iron trough castable was prepared with dense corundum and silicon carbide as the main raw materials and submicron SiO_(2) powder(d_(50)=0.242μm,SiO_(2)=99.9 mass%)as the binder.The effect of the sub...A new cement free iron trough castable was prepared with dense corundum and silicon carbide as the main raw materials and submicron SiO_(2) powder(d_(50)=0.242μm,SiO_(2)=99.9 mass%)as the binder.The effect of the submicron SiO_(2) powder addition(3%,4%,5%,6%,7%,8%,and 9%,by mass,respectively)on the properties of the prepared castables was studied.The working mechanism of submicron SiO_(2) powder was analyzed from the perspective of the particle size distribution and infrared absorption spectrum.The results show that:(1)cement free iron trough castables can be prepared using submicron SiO_(2) powder alone as the binder;(2)compared with traditional castables,the cement free castables have made a breakthrough in the water addition and hot modulus of rupture.The optimal submicron SiO_(2) powder addition is 4%-6%.展开更多
基金Supported by Zhejiang Province Key Science and Technical Program (No.2006C11119)
文摘The synthesis and dielectric properties of calcium titanate （CaTiO3） submicron powder synthesized by mechanical ball-milling method have been investigated in this paper. With the ball-milling time increased, the size of CaTiO3 particles decreased from micron to submicron, and a great deal of nanoparticles （50-100 nm） occurred. The CaTiO3 ceramics made from submicron powders achieved compact structure at the sintering temperature of 1 250℃, and had good dielectric properties： εr=171, Q×f= 4 361 GHz, τf =＋782 ppm/＋C, IR=6.5×10^12Ω, which was a similar result compared with the CaTiO3 ceramics made from nanoparticles by sol-gel method.
基金Project supported by the "863" (Grant No. SQ2008AA03Z4471960)the National Natural Science Foundation of China(Grant No. 60676050)
文摘Base metal nickel is often used as the inner electrode in multilayer chip positive temperature coefficient resistance （PTCR）. The fine grain of ceramic powders and base metal nickel are necessary. This paper uses reducing hydrazine to gain submicron nickel powder whose diameter was 200-300 nm through adjusting the consumption of nucleating agent PVP properly. The submicron nickel powder could disperse well and was fit for co--fired of multilayer chip PTCR. It analyes the submicron nickel powder through x-ray Diffraction （XRD） and calculates the diameter of nickel by PDF cards. Using XRD analyses it obtains several conclusions： If the molar ratio of hydrazine hydrate and nickel sulfate is kept to be a constant, when enlarging the molar ratio of NaOH/Ni^2＋, the diameter of nickel powder would become smaller. When the temperature in the experiment raises to 70-80 ℃, nickel powder becomes smaller too. And if the molar ratio of NaOH/Ni2＋ is 4, when molar ratio of （C2H5O）2/Ni^2＋ increases, the diameter of nickel would reduce. Results from viewing the powders by optical microscope should be the fact that the electrode made by submicron nickel powder has a better formation and compactness. Furthermore, the sheet resistance testing shows that the electrode made by submicron nickel is smaller than that made by micron nickel.
基金support from the National Natural Science Foundation of China(NSFC,No.51804233)。
文摘A new cement free iron trough castable was prepared with dense corundum and silicon carbide as the main raw materials and submicron SiO_(2) powder(d_(50)=0.242μm,SiO_(2)=99.9 mass%)as the binder.The effect of the submicron SiO_(2) powder addition(3%,4%,5%,6%,7%,8%,and 9%,by mass,respectively)on the properties of the prepared castables was studied.The working mechanism of submicron SiO_(2) powder was analyzed from the perspective of the particle size distribution and infrared absorption spectrum.The results show that:(1)cement free iron trough castables can be prepared using submicron SiO_(2) powder alone as the binder;(2)compared with traditional castables,the cement free castables have made a breakthrough in the water addition and hot modulus of rupture.The optimal submicron SiO_(2) powder addition is 4%-6%.
