聚合物/纳米CaCO3复合材料研究进展

综述了表面处理对聚合物／纳米CaCO3复合材料力学性能的影响、纳米CaCO3在聚合物基体中的分散机理和对聚合物结晶行为的影响，并展望了聚合物／纳米CaCO3复合材料的发展方向和前景。     

Dietary Supplementation of Calcium may Counteract Obesity in Mice Mediated by Changes in Plasma Fatty Acids

The scope of this study was to assess the impact of calcium and conjugated linoleic acid (CLA) supplementation on plasma fatty acid profiles and to evaluate potential synergistic effects of both compounds against dietary obesity. Mice separated into five experimental groups were followed: control (C), high-fat diet (HF), HF with calcium (Ca), HF plus CLA and HF with both Ca and CLA. Plasma metabolites and fatty acids were determined by commercial kits and gas chromatography, respectively. Both dietary calcium and CLA supplementation contributed to lower body fat gain under a HF diet. Maximum efficacy was seen with calcium; no additional effect was associated with the combined treatment with CLA. Plasma leptin, adiponectin and HOMA index were in accordance with an altered glucose/insulin homeostasis in the HF and HF + CLA groups, whereas control levels were attained under Ca-enriched diets. Plasma fatty acids showed minor changes associated to CLA treatment, but a high impact on PUFA was observed under Ca-enriched diets. Our results show that the mechanism underlying the anti-obesity effects of calcium supplementation is mediated mainly by changes in PUFA plasma profile. In addition, the lack of synergy on body weight reduction in combination with associated lipid profiles of calcium and CLA suggests that calcium may interfere with absorption and/or bioactivity of CLA, which can be of relevance when using CLA-fortified dairy products against human obesity.     

FP膨胀增强剂作用机理分析

通过差热分析，扫描电镜和孔径试验的方法，探讨了ＦＰ在砼中早强、增强、抗裂、抗渗的机理，并进行了分析．     

无皂乳液聚合制备碳酸钙-聚苯乙烯复合物胶粒

研究了碳酸钙－苯乙烯－过硫酸铵体系的无皂乳液聚合反应。分别探讨了反应时间、引发剂用量、单体用量、碳酸钙用量对苯乙烯的转化率、碳酸钙的表观包覆率、包复率的影响及反应时间对复合物胶粒表面电性的影响。     

氢气还原分解硫酸钙的热力学研究

运用热力学计算软件HSC对氢气还原硫酸钙进行了热力学研究。计算发现,加入氢气后硫酸钙的分解温度较自行分解所需的温度显著降低,且氢气浓度越低对硫酸钙反应越有利。根据热力学计算结果,利用磷石膏在流化床分解炉中进行热态试验,考察了反应温度、气体流量、床层高度对磷石膏分解时反应动力学的影响。实验结果表明,当气体流量242mL/min、床层高径比(H0/D)4.8、温度控制在1 000～1 050℃时,对于流化床中氢气还原分解磷石膏有利。     

Thermal behaviour and phases evolution during the sintering of porous inorganic membranes

Anorthite-based highly porous membranes were successfully produced using calcined oyster shell to enhance the pore network. The calcined oyster shells produce CaO responsible for the crystallisation of gehlenite and anorthite at relatively low temperature. While the crystallisation produced nano and meso size of intergranular pores, vitrification of feldspar is responsible for development of the capillary porosities. The increasing sintering temperature from 1200 °C to 1300 °C implies the increase in average pores radius from 1.2 μm to 14.3 μm due to the formation of spherical pores from vitrification. The combination of different class of porosities in the matrices results in the interconnection with improvement of the permeability of the porous network. Porosity, permeability and chemical stability were improved with 20 wt.% of calcined oyster shell addition allowing the possible development of high strength porous network which is promising for the membranes support and other applications including liquid separation as well as liquid filtration where high pressure is used.     

Behavior and mechanism of in-situ synthesis of auxiliary electrode for electrochemical sulfur sensor by calcium aluminate system

The behavior and mechanism of in-situ synthesis of the auxiliary electrode for sulfur sensor were investigated in this work, aiming for better application of calcium aluminate system in synthesizing the auxiliary electrode used for sulfur sensor. The in-situ reaction experiment was developed. In addition, the thermodynamic and kinetic calculations were adopted to further study the in-situ reaction possibility and the reaction rate. The results indicated that the value of lg(a_[S]/a_[O]) should be greater than a particular value to ensure the occurrence of the in-situ reaction. After immersion into the molten iron, the CaS phase was synthesized in the calcium aluminate system. The relationship between the reaction rate and reaction time was exponential, and the initial reaction rate was affected by the CaO content incorporated in the calcium aluminate system and the sulfur content in the molten iron. The initial in-situ reaction rate greatly increased with the increase of the CaO content and sulfur content. For example, the initial reaction rate was as high as 14.87 s^-1 when the calcium aluminate system containing 60 wt% of CaO and for a sulfur content of 0.077 wt% in the molten iron. Moreover, the reason that the sulfur sensor fabricated by the ZrO₂(MgO) tube with the calcium aluminate coating with different components had the same response time when measuring the different sulfur contents in the molten iron was further explained.     

Effect of nanosilica addition on bioactivity and in vivo properties of calcium aluminate cement

This study aims at assessing the influence of nanosilica on the bioactivity and mechanical properties of calcium aluminate cement. For this purpose, nanosilica was applied as a replacement for calcium aluminate cement at 0, 2, 5 and 8 wt%. The main components were analyzed by scanning electron microscope coupled with surface imaging and elemental analysis, fourier transform infrared spectroscopy and X-ray diffraction analysis. To estimate the bioactivity of specimens, hydroxyapatite formation on the surface of cement paste was investigated in the simulated body fluid solution. In addition, in vivo evaluation of calcium aluminate cement was performed in subcutaneous tissue of rats. To investigate the mechanical properties, both compressive and flexural strengths were also measured. The results revealed that by increasing nanosilica up to 8 wt%, the strength enhanced. Moreover all cement paste samples with various amounts of nanosilica represented good bioactivity because of formation of bonelike apatite layer on the surface of specimens within 28 days after soaking in simulated body fluid. In vivo experiments indicated that the cement sample was absorbed by the tissue and there was no infection at the implant site. Based on the in vitro and in vivo results, the specimen with 2 wt% nanosilica represented the highest bioactivity.     

Influences of gallium substitution on the phase stability,mechanical strength and cellular response of β-tricalcium phosphate bioceramics

β-tricalcium phosphate (β-TCP), a well-accepted synthetic bone grafting biomaterial, is confronted with limitations of poor phase stability and lacking the capacity to mediate the biological functions. In the current study, gallium (Ga) was substituted for calcium in the β-TCP, and the influences of Ga substitution on the phase stability, compressive strength and cellular response of β-TCP bioceramics were investigated. The results indicated that substitution of at least 2.5 mol% Ga for calcium prevented the β-TCP from transforming into α-TCP at 1250 °C. The β-TCP bioceramics substituted with 2.5 mol% Ga attained the highest compressive strength. The β-TCP bioceramics substituted with 2.5 and 5 mol% Ga showed good cytocompatibility, and suppressed in vitro osteoclastic activity as well as osteoblastic differentiation. Considering the favorable mechanical strength and the inhibitory effect on the osteoclastic activity, the β-TCP bioceramics substituted with 2.5 mol% Ga are promising for treating the bone defect in the pathological state of excessively rapid bone resorption.