Hydroxyl-terminated poly(vinylbenzyl chloride) (PVBCOH) were synthesized using nitroxide-mediated controlled radical polymerization. Then, PVBCOH was used as a macro-initiator for ring-opening polymerization of lactide (LA) in the presence of stannous octanoate (Sn(Oct)2) as a catalyst. The structures, molecular weights and polydispersity index (PDI) of PVBCOH and PVBC-b-PLA were characterized by 1H-NMR, and GPC, respectively. The results indicated that PDI of PVBCOH and PVBC-b-PLA was 1.63 and 1.27, respectively. Moreover, the molecular weight and PDI of PVBCOH and PVBC-b-PLA could be well tuned by changing monomer-to-initiator ratio.
The ZrW2O8 family of materials has been shown to display the unusual property of an isotropic bulk contraction in volume with the rising of temperature. They have a number of potential applications, for example, they would be widely used in composite material and solid electrolyte based on its characteristic of negative thermal expansion and ionic conductive property. In this paper, an Al3+,V5+ double substitute negative thermal expansion (NTE) solid solution Zr1-xAlxMoW1-yVyO8 was synthesized by co-precipitation method. The phase composition, the micromorphology and the thermal expansion coefficient were obtained by using X-ray diffraction (XRD), scanning electronic microscope (SEM) and thermal mechanical analyzer (TMA), respectively. The results show that the sample’s density rises with the increasing of the content of V5+, while, its porosity declines. The thermal expansion coefficients of the samples are between -3.0~4.0×10-6 K-1, it indicates that their negative thermal expansion behavior is a little lower than that of ZrMoWO8. And the experiment also shows that these samples have displayed a fine behavior of heat shock resistance.
This paper has put forward a high-temperature quantitative X-ray powder diffraction analysis method for the determination of an isothermal section of a ternary system in comparison with a conventional method. In a three-phase region of the isothermal section at 1150 °C of Cu2O(CuO)-Al2O3-SiO2 pseudo-ternary system, the compositions of the solid phase points of three system points are determined according to the quantitative analysis of the crystalline phases in the samples carried out by Rietveld method. Then the liquid phase point of the three-phase region is determined according to the crosspoints of the tie lines of every pair of system point and solid phase point. The precisions of the analytical results have reached to be 0.1 ~ 5.0 %. By comparison, a good result is obtained for the determination of the liquid phase point of the three-phase region in the isothermal section at 1150 °C when the analytical results of high-temperature RQA analysis are used in determination of the isothermal section of the pseudo-ternary system.
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