Materials Science Forum Vols. 663-665

Abstract: Micro-scale plake-like SrTO3 particles were synthesized by two routes of topochemical conversion. One is by growing on Sr3Ti2O7 (S3T2) core particles in molten salt condition, and the other is from the layer-structured SrBi4Ti4O15 (SBT) precursor in a KCl medium. The effects of the morphology and size of the precursor to platelet SrTiO3 crystals were studied. X-ray diffraction analysis revealed that the crystallographic {010} plane of SBT was converted into the pseudo-cubic {001} plane of SrTiO3. The polycrystalline SrTiO3 particles from BST precursor exhibited a plate-like shape with 10-15μm in length and a high aspect ratio, and were more suitable for preparing textured ceramics by templated grain growth process than the platelets from the S3T2 precursors.

Abstract: The sintering behavior and microwave dielectric properties of the (Ca0.9375Sr0.0625)0.25(Li0.5Sm0.5)0.75TiO3 (CSLST) ceramics doped with different amounts of Li2O-B2O3-SiO2-CaO-Al2O3 (LBSCA) glass were investigated. The sintering temperature of the CSLST ceramics can be effectively reduced over 200oC due to the addition of LBSCA glass. For the 5 wt% LBSCA-doped CSLST ceramics, which are sintered at only 1000 oC for 5 h, show optimum microwave dielectric properties as follows: εr=84.74, Qf=2446 GHz and τf=-12.48 ppm/oC.

Abstract: In this article, we report on the observations that in the aqueous electrolyte of aluminum nitrate, the thin metallic conducting films on both internal and external surface of porous silicon (PS) thin films that emit visible photoluminescence at room temperature prior to electrochemical deposition have been obtained under electrochemical deposition condition. Add to this high surface-to-volume ratio and these make it a good candidate for the catalyst supporter. We have investigated the surface morphology of PS after the interval of about 30 hours of electrochemically deposited aluminum by means of scanning electron microscopy (SEM). It has been shown from SEM images that not only micrometer-sized pores are smoothed by deposition of aluminum microcrystal, but also the presences of semi-sphere aluminum microcrystal which rooted in the tip of micrometer-sized pores are observed. On the one hand, this extremely interesting phenomenon which the micrometer-sized pores are smoothed may be explained in terms of principle of electrochemical deposition; on the other hand, we have laid the formation mechanism of semi-spherical aluminum microcrystal at the door of Gibbs free energy.

Abstract: Ordered double perovskite oxides (Sr2-3xLa2xBax)FeMoO6 (0≤x≤0.3) have been investigated in this work. X-ray powder diffraction reveals that the crystal structure of the compounds changes from a tetragonal I4/m lattice to a cubic Fm 3m lattice around x=0.2. Though the nominal average size of the A site cation of (Sr2-3xLa2xBax)FeMoO6 is designed to be almost independent of x, the refinements of the crystal structure show that the lattice constants increase with x in both the tetragonal and the cubic phase regions due to electron doping. As the x increases, the degree of cationic ordering on the B site is decreased pronouncedly, while the Curie temperature of the compounds is nearly unchanged.

Abstract: Transparent conducting Ti-Ga co-doped zinc oxide (TGZO) thin films with high transmittance, low resistivity were firstly prepared on glass substrate by direct current (DC) magnetron sputtering at room temperature. X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that the TGZO films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. The lowest resistivity obtained in our experiment is 3.95×10-4Ω⋅cm. The average transmittance of the films is over 92% in the range of 400~760 nm.

Abstract: Transparent conducting Ti-Al co-doped zinc oxide films (TGZO) with high transparency and relatively low resistivity have been successfully prepared on water-cooled glass substrate by DC magnetron sputtering at room temperature. All the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. The Ar sputtering pressure was varied from 1.5 to 13 Pa. The electrical resistivity decreases when the sputtering pressure increases from 1.5 to 7.5 Pa. The electrical resistivity increases when the sputtering pressure increases from 7.5 to 13 Pa. When the sputtering pressure is 7.5 Pa, it is obtained that the lowest resistivity is 2.18×10-4Ω⋅cm. In the visible region, all the deposited films show a high average transmittance of above 92 %.

Abstract: A serious of triply-responsive poly(N,N-dimethylaminoethyl methacrylate) (PMAEMA) containing an azobenzene group as the terminal group were synthesized by atom transfer radical polymerization (ATRP). The ATRP process of DMAEMA was initiated by an azobenzene derivative substituted with a 2-bromoisobutyryl group (Azo-Br) using CuCl/Me6TREN as catalyst and the mixture of DMA and H2O (v/v = 3:1) as solvent. The molecular weights and their distributions of the resulting homopolymers (Azo-PDMAEMA) were characterized by gel permeation chromatography (GPC). The polymers are soluble in aqueous media and exhibit a lower critical solution temperature (LCST) that alternated reversibly in response to pH and photoisomerization of the terminal azobenzene moiety. It was found that the LCST increased as pH decreased in the range of testing. Under UV light irradiation, the trans-to-cis photoisomerization of the azobenzene moiety resulted in a higher LCST, while it recovered under visible light irradiation.

Abstract: The four-layer structure angle-dependent pigments with compositions of Mica/TiO2 /Al2O3/Fe2O3, Mica/TiO2/Al2O3/Cr2O3 and Mica/TiO2/Al2O3/Co2O3 were firstly prepared by the wet-chemical coating method, respectively. The as-prepared pigments were performed by precipitating different metal ions, such as Cr3+, Fe3+, Co2+and Al3+, on the pretreated substrates, mica titanium. The optical effects of four-layer structure pigments were investigated in detail by using the five angles’ spectrophotometer. The angle-dependent spectral reflectance and color changes can be quantitatively measured, and the results show that the angle-dependent effects for the as-prepared pigment were improved by the increasing coated Al2O3 layers.

Abstract: Biocompatible and biodegradable synthetic materials have attracted considerable attention during the past two decades. In this work, a series of amphiphilic triblock copolymers containing D-galactopyranose were synthesized by atom transfer radical polymerization (ATRP). The macroinitiator was prepared by the esterification between poly(ethylene glycol) monomethyl ether with a number-average molecular weight of 1200 g/mol (MeOPEO-1200) and 2-bromoisobutyryl bromide. The sugar-bearing monomer, 6-O-methacryloyl-1,2;3,4-di-O-isopropylidene-D-galactopyranose (MAIPG) was polymerized using PMDETA/CuBr as catalytic system and anisol as solvent. The chemical structure and composition of the resultant polymer MeOPEO-b-PMAIPG were verified by 1H NMR. The molecular weights and their polydispersities were characterized by gel permeation chromatography (GPC). The results indicate that the polymerization follows the mechanism of ATRP. The amphiphilic copolymers can self-assembly to from micelles with PMAIPG as the core and PEO as the corona, which have potential applications as biomaterials or controlled release drug delivery systems.

Abstract: In order to improve the service life of copper crystallizer, a layer of Ni-based alloy on thick copperplate surface was performed by plasma spray process, and then YAG pulsed laser was used to remelt spray coating. Microstructure analysis, hardness test, and the wear resistance comparison experiments were taken to the specimen. The result shown that the Ni-based alloy cladding, metallurgy bonding with the copperplate, can be performed by taking the method of the YAG laser remelt technology; the structure of the cladding is compact, without defects such as pores and cracks. The micro hardness of cladding zone is between 450-490HV, which is much higher than that of the copper substrate (about 90 HV). The wear tests showed the laser cladding layer performed 14 times higher wear resistance compared to copper substrate.