Varistor behavior study in undoped tungsten trioxide ceramic

In this paper, varistor property and mechanism of undoped tungsten trioxide (WO₃) ceramic have been studied. Experimental results revealed that pure WO₃ ceramic could exhibit a nonohmic behavior which was formed in the cooling process of ceramic, and very sensitive to heat treatment in different atmospheres. By comparison with the reported SnO₂ and ZnO varistor systems, it is supposed that the surface of WO₃ grain is more ready to adsorb oxygen and form high enough barriers at grain boundaries responsible for varistor behavior. The influences of heat treatments on the varistor properties of WO₃ ceramic have been investigated.     

Methane non-oxidative aromatization on Mo/ZSM-5: Effect of adding triethoxyphenylsilanes into the synthesis system of ZSM-5

A series of ZSM-5 zeolites were synthesized by adding triethoxyphenylsilane (PTEOS) into the initial sol of the synthesis system. The samples were studied by XRD, SEM, N₂ adsorption-desorption and acid assessment of d₃-acetonitrile adsorption. Characterization results showed that the crystal size of the ZSM-5 zeolites could be adjusted in a certain range by introducing different contents of PTEOS. Besides, the resultant materials possess hierarchical porosity in addition to those micropores generated by the MFI channels. Moreover, supported Mo/ZSM-5 catalysts were prepared, and their catalytic performances were investigated in the methane non-oxidative aromatization. It was found that the Mo/ZSM-5 catalyst, bearing suitable crystal size and mesoporous characteristic showed relatively high shape-selectivity to benzene and high stability for the reaction of methane aromatization.     

Multiple solutions for a semilinear equation involving singular potential and critical exponent

Variational methods are used to prove the existence of positive and sign-changing solutions for a semilinear equation involving singular potential and critical exponent in any bounded domain.     

On spacelike hypersurfaces with constant scalar curvature in the de Sitter space

We classify spacelike hypersurfaces of the de Sitter space with constant scalar curvature and with two principal curvatures. Moreover, we prove that if Mn is a complete spacelike hypersurface with constant scalar curvature n(n−1)R and with two distinct principal curvatures such that the multiplicity of one of the principal curvatures is n−1, then R<(n−2)c/n. Additionally, we prove several rigidity theorems for such hypersurfaces.     

Ljusternik-Schnirelman theory in partially ordered Hilbert spaces

We present several variants of Ljusternik-Schnirelman type theorems in partially ordered Hilbert spaces, which assert the locations of the critical points constructed by the minimax method in terms of the order structures. These results are applied to nonlinear Dirichlet boundary value problems to obtain the multiplicity of sign-changing solutions.

     

Studies on the Formation Mechanism of Silica-Sodalite in the System of Sodium Hydroxide-Silica-Ethylene Glycol

In 1985,Bibby and Dale first reported the synthesis of silica-sodalite from organic solvent such as ethylene glycol or propanol.In 1987, Van Erp and his coworkers reported the formation of crystalline aluminosilicates in organic solvents such as hexanol,glycol, glycerol, sulfolane and pyridine. Because the concepts effective in the aqueous synthesis cannot be simply applied to the nonaqueous media,the formation mechanism of zeolite in the nonaqueous system has not been investigated yet.     

STUDIES OK TRANSFORMATION FOR ZEOLITE CRYSTAL(Ⅲ)——THE STABILITY OF ZEOLITE NaY AND THE STRUCTURE OF ZEOLITE NaPc

We investigated the crystallization of NaY and especially the transformation for NaY to NaPc type zeolite from an initial gel of the batch composition 3.3Na2O Al2O3 10SiO2 200H2O at 100℃and the changes of zeolite structures in the process of the transformation crystal using the modern techniques,A more detailed liquid phase transportation mechanism of the transformation was suggested.     

聚碳酸亚丙酯聚氨酯的合成与性能

用ＣＯ２与环氧丙烷共聚产物聚碳酸亚丙酯制备出聚氨酯（ＰＰＣＰＵ）．同时探讨了ＰＰＣＰＵ最佳合成方法,考察了异氰酸酯基与羟基的比值、扩链交联剂用量等因素对其力学性能的影响．研究了ＰＰＣＰＵ的形态结构及其性能对配比的依赖关系．发现聚碳酸亚丙酯的耐热性因聚氨酯的形成而得到较大的改善,并发现该类材料具有优异的耐水性能．