纤维素―铝酸锶复合膜的制备及表征

将微晶纤维素溶解于氯化1-正丁基-3-甲基咪唑([Bmim]Cl)离子液体中,加入铝酸锶荧光粉,然后流延成膜,制备得到了纤维素―铝酸锶复合膜。利用红外光谱、X射线衍射、热重分析、扫描电镜和荧光发射光谱对复合膜进行了表征。结果表明,铝酸锶荧光粉在纤维素膜中分布均匀,铝酸锶荧光粉和纤维素之间存在着一定的相互作用,纤维素对荧光粉体发光影响较小。     

溶胶-凝胶法制备的钛酸锶钡超细粉体的结构与性能

采用溶胶-凝胶法制备了不同Ba／Sr比的BST粉体，研究了粉体的热处理制度，粉体及其烧结体的微观结构，烧结体的介电性能以及居里温度与组成的关系等。研究结果表明用溶胶．凝胶法制备的BST超细粉体，由于其尺寸细小，粉体的比表面积很大，因而烧结活性更高，在1350℃烧成4h可获得结构致密的单一钙钛矿相的瓷体。     

Two-Phase Calorimetry. II. Studies on the Thermodynamics of Cesium and Strontium Extraction by Mixtures of H+CCD− and PEG-400 in FS-13

Abstract

Thermochemical characterization of the partitioning of cesium and strontium from nitric acid solutions into mixtures of the acid form of chlorinated cobalt dicarbollide (H⁺CCD^?) and polyethylene glycol (PEG-400) in FS-13 diluent has been completed using isothermal titration microcalorimetry and radiotracer distribution methods. The phase transfer reaction for Cs⁺ is a straightforward (H⁺ for Cs⁺) cation exchange reaction. In contrast, the extraction of Sr²⁺ does not proceed in the absence of the co-solvent molecule PEG-400. This molecule is believed to facilitate the dehydration of the Sr²⁺ aquo cation to overcome its resistance to partitioning. The phase transfer reactions for both Cs⁺ and Sr²⁺ are enthalpy driven (exothermic), but partially compensated by an unfavorable entropy. The results of the calorimetry studies suggest that the PEG-400 functions as a stoichiometric phase transfer reagent rather than acting simply as a phase transfer catalyst or phase modifier. The calorimetry results also demonstrate that the extraction of Sr²⁺ is complex, including evidence for both the partitioning of Sr(NO₃)⁺ and endothermic ion pairing interactions in the organic phase that contribute to the net enthalpic effect. The thermodynamics of the liquid-liquid distribution equilibria are discussed mainly considering the basic features of the ion solvation thermochemistry.     

掺锶羟基磷灰石及其在口腔保健领域中的应用

主要综述了掺锶羟基磷灰石的生物特性和制备方法,以金属锶元素取代羟基磷灰石中的部分钙元素进行改性,可得到掺锶羟基磷灰石,掺锶后改善和提高了羟基磷灰石的结晶性、溶解性、降解性和机械性能,并增强生物相容性。详细讨论了掺锶羟基磷灰石在口腔保健领域中的功效及作用,指出了掺锶羟基磷灰石在口腔保健用品中具有广阔的应用前景。     

Effect of strontium doping on structural and dielectric behaviour of barium titanate nanoceramics

ABSTRACT

Barium strontium titanate (Ba_(1?x)Sr_xTiO₃ where, x?=?0.0, 0.2, 0.3, 0.4 and 0.5) nanoparticles have been successfully synthesised by sol–gel method and characterised thoroughly. With the increase in Sr concentration (x?>?0.3), the symmetry of the crystal structure changed from tetragonal to cubic phase. The dielectric behaviour of the ceramic nanoparticles was evaluated using impedance analyser with an operating frequency of 1?Hz to 1?MHz. A very high dielectric constant 4915 was obtained for Ba_0.7Sr_0.3TiO₃ at 1?Hz frequency with low dielectric loss of 1.91, which showed very good value than the one previously reported. The density of the material was found to be >98% of theoretical density. Dielectric constants were measured by varying the temperature from 35 to 150°C and the Curie temperatures were also evaluated. The small amount of Sr doping was beneficial for obtaining high dielectric constant material which can be used in various electronic applications.     

Electric properties of La0.8Sr0.2CoO3 nanoceramics

The electric measurements were carried out for La_0.8Sr_0.2CoO₃ nanoceramics by using impedance spectroscopy methods. The resistance of sample was practically independent of frequency in measurement range. Its dependence on reciprocal temperature showed quite complicated mechanism of conduction. The most striking property of investigated sample was its resistance decreasing with increasing applied polarization.     

Studies on the structure and microstructure of lead strontium titanate thin films

Pb1-xSrxTiO3 （0≤x≤0.9） thin films on Si （100） substrate were prepared by the sol-gel process and their characteristics were investigated as a function of strontium content（x）. With increasing of the strontium content, the tetragonality （c/a） was slightly decreased, the splitting peaks become less prominent and the splitting peaks tend to merge into a single peak. Furthermore, the grain size of the films was systematically reduced with the increase in strontium content.     

聚锑酸离子交换剂的制备及分离锶和钇

以三氧化二锑为原料,双氧水为氧化剂,经氧化回流法制备聚锑酸无机离子交换剂.该聚锑酸离子交换剂对锶-钇混合溶液中的锶具有较好的选择性吸附能力.通过正交实验设计法对反应影响因素进行了优化,结果表明,在60 ℃时加入40 mL水和12 mL H_2O_2氧化10 g Sb_2O_3固体,反应120 min可制得对Sr~(2+)和Y~(3+)具有较高分离系数的聚锑酸离子交换剂.理化性能研究表明,产物是一种阳离子交换剂,对溶液中的Sr~(2+)和Y~(3+)的动态吸附分离具有较高的选择性.     

Thermal Instability and Microstructure of Strontium M-type Hexaferrite Nanoparticles Synthesized by Citrate Approach

The dried gel of SrFe12O19, prepared by citrate approach, was investigated by means of infrared spectroscopy （ IR ）, thermogravimetric analysis （ TG ）, differential scanning calorimetry （ DSC ）, X- ray diffraction（ XRD ） techniques, energy dispersive spectroscopy（ EDS ）, and transmission electron microscopy（ TEM ）. The thermal instability and the thermal decomposition of low-temperature strontium M-type hexaferrite crystallized at about 600℃ were confirmed for the first time by XRD method. The decomposition of the low-temperature strontium M-type hexaferrite took place at about 688.6℃ determined by DSC investigation. The low-temperature strontium M-type hexaferrite nanopartieles were decomposed into SrFeO2.5 with an orthorthombic cell and Fe2O3 with a tetragonal cell as well as possibl α-Fe2O3 . The agglomerated particles with sizes less than 200 nm obtained at 800℃ were plesiomorphous to strontium M-type hexaferrite. The thermally stable strontium M-type hexaferrite nanopartieles with sizes less than 100um cotdd take place at 900 ℃ . Up to 1000 ℃ , the phose transformotion to form strontium M-type hexaferrite was ended, the calcinations with the sizes more than 1μm were composed of α-Fe2O3 and strontium M-type hexaferrite. The method of distinguishing γ-Fe2O3 with a spinel structure from Fe2O3 with tetragonal cells by using powder XRD method was proposed. Fe2O3 with tetragonal cells to be crystallized before the crystallization of thermally stable strontium M-type hexaferrite was confirmed for the first time. The reason why α- Fe2O3 as an additional phase appears in the calcinations is the cationic vacancy of stroutium M-type hexaferrite , SrFe12-x□O19 （0≤x ≤0.5）.     

Relaxor Behavior of (Sr0.8Ba0.2)TiO3 Ceramic Solid Solution Doped with Bismuth

The dielectric properties of (Sr_0.8Ba_0.2)_1-1.5xBi_xTiO₃ ceramics in the range 0 x 0.18 are investigated. A ferroelectric relaxor behavior is observed. The degree of the diffuseness and the relaxation of the phase transition increases as the Bi content increases. A random electric field is suggested to be responsible for the relaxor behavior observations. The dependence of the diffuseness on the grain size is presented.