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Chen X.,Kunming University of Science and Technology | Chen X.,Key Laboratory of Advance Materials in Yunnan Province | Chen X.,Key Laboratory of Advance Materials of Precious Nonferrous Metals | Du J.,Kunming University of Science and Technology | And 11 more authors.
Advanced Materials Research | Year: 2012

Porous alumina ceramic was prepared using sodium dodecyl benzene sulfonate (SDBS) as foaming agent by the combination method of gel casting and foaming. The effect of solid content on the line shrinkage rate, the porosity, the fracture strength and the microscopic structure of porous aluminum ceramic were studied. The result showed that when solid content increased, the line shrinkage rate of porous alumina ceramic decreased form 20% to 1.2%, the total porosity first increased and then decreased from 43% to 57%, the fracture strength first decreased and then increased from 23MPa to 41MPa. SEM indicated that alumina ceramic had more open pores when solid content was too low, the number of closed pore increased along with solid content rising, when solid content was too high, pore size distribution uniformity decreased. © (2012) Trans Tech Publications. Source


Du J.,Kunming University of Science and Technology | Du J.,Key Laboratory of Advance Materials in Yunnan Province | Du J.,Key Laboratory of Advance Materials of Precious Nonferrous Metals | Gan G.,Kunming University of Science and Technology | And 11 more authors.
Advanced Materials Research | Year: 2012

Preparation of aqueous ceramics slurry with high solid volume and low viscosity is premise and key step of gelcasting, and dispersant play important role in slurry preparation. In this paper, triammonium citrate (TAC) was used as dispersant of PMN-PZT piezoelectric ceramics slurry, the effects of TAC on slurry stability and rheological properties and dispersion mechanism of TAC were investigated by sedimentation test, viscosity, scanning electron microscopy (SEM) and FTIR analysis. The SEM results indicated that TAC could reduce the agglomeration of powder particles and make ceramic particles well-dispersed. FTIR indicated that strong chemical absorption occurred between TAC and PMN-PZT powder, and slurry stability and rheological properties of PMN-PZT slurry were improved through electrostatic interaction of TAC. The effects of TAC on sedimentation volume and viscosity have similar tendency. When TAC content was 7.5vol% and pH of slurry was about10, PMN-PZT slurry suitable for gel-casting could be acquired. © (2012) Trans Tech Publications. Source


Gao X.,Kunming University of Science and Technology | Gao X.,Key Laboratory of Advance Materials of Yunnan Province | Gao X.,Key Laboratory of Advance Materials of Precious Nonferrous Metals | Gan G.,Kunming University of Science and Technology | And 15 more authors.
Key Engineering Materials | Year: 2012

To better understand the effects of Co-doping with Cr, Mn, and Co on electronic structure and the density of states of ZnO, the theoretical study was carried out by means of first principles and pseudopotentials method based on density functional theory (DFT). Portion of Zn atoms in ZnO were crystal randomly substituted by Mn, Cr or Co elements, and the electronic structure of Cr 2+, Mn 2+ and Co 2+ changed into 3d 4, 3d 5 and 3d 7, resulting in enhanced localized magnetic moments in ZnO. It was concluded that electronic properties of ZnO were not only related to electron energy level, but also associated with electron spin, with spin-dependent scattering and spin-dependent hopping conductivity as maybe two important mechanisms. © (2012) Trans Tech Publications. Source


Kang K.,Kunming University of Science and Technology | Kang K.,Key Laboratory of Advance Materials of Yunnan Province | Kang K.,Key Laboratory of Advance Materials of Precious Nonferrous Metals | Gan G.,Kunming University of Science and Technology | And 20 more authors.
Journal of Semiconductors | Year: 2015

An investigation was made into the effect of doping with the elemental crystal Ge or/and GeO2 on the TiO2-V2O5-Y2O3 varistor ceramics. The result shows that as the doping contents of V2O5 and Y2O3 are 0.5 mol%, respectively, co-doping with 0.3 mol% Ge and 0.9 mol% GeO2 makes the highest α value (α = 12.8), the lowest breakdown voltage V1mA (V1mA = 15.8 V/mm) and the highest grain boundary barrier ΦBB = 1.48 eV), which is remarkably superior to the TiO2-V2O5-Y2O3 varistor ceramics undoped with Ge and GeO2 and mono-doped with Ge or GeO2. The TiO2-V2O5-Y2O3-Ge-GeO2 ceramic has the prospect of becoming a novel varistor ceramic with excellent electrical properties. © 2015 Chinese Institute of Electronics. Source

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