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.     

The effect of synthesis conditions on the physicochemical properties of magnesium aluminate materials

Magnesium aluminate-based materials were prepared by applying different methods: (i) mechanochemical milling of the initial mixture of magnesium and aluminium nitrate powders (in appropriate stoichiometric amounts) followed by heat treatment at temperatures of 650 °C and 850 °C and (ii) melting of the mixture of nitrate precursors at 240 °C followed by thermal treatment at 650 °C, 750 °C and 850 °C. The effect of synthesis method on the structure and morphology of the obtained solids was studied by using various techniques such as: nitrogen adsorption-desorption isotherms, powder XRD, IR spectroscopy and SEM. It was shown that the mechanochemical milling performed before calcination procedure leads to obtaining of nanocrystalline magnesium aluminate spinel phase at lower temperature of 650 °C in comparison with the method using thermal treatment only (at 750 °C). The obtained nanomaterials exhibit mesoporous structure.     

Effects of zirconium silicate and chromite addition on the microstructure and bulk density of magnesia–magnesium aluminate spinel-based refractory materials

Six synthesized magnesium aluminate spinel-based refractory compositions used in steel and cement applications, were prepared using a two stage sintering process at 1760 °C, starting with approximately 1:1 wt% ratio of pure magnesia and alumina with additions of zirconium silicate (0.5, 1.0 and 2.0 wt%) and chromite (2.0, 3.0 and 5.0 wt%). These compositions were investigated for effects on densification, chemical and mineralogical phases formed.     

Eu(DMBM)_2(2,2′-bipy)NO_3的合成与荧光光谱

本工作首次合成了Eu(DMBM)_2(2,2′-bipy)NO_3(DMBM=二对甲氧基苯甲酰甲烷,2,2′-bipy-2,2′-联吡啶)。通过元素分析、热谱、电导率、红外和拉曼光谱、质子核磁共振谱对所合成化合物进行了表征。在77K测定了固体配合物的激发光谱和发光光谱。光谱数据说明配合物含有两种Eu(Ⅲ)格位。配合物中三种配体在Eu(Ⅲ)周围的分布情况略有不同,显示出不同的晶体场效应。光谱数据表明,配合物中Eu(Ⅲ)格位属于非中心对称的点群C_1或C_3或C_2。     

Standard reference materials for cements

The eight portland cements and two calcium aluminate cements in the Standard Reference Material (SRM) 1880 series are among the most popular SRMs in the catalog of the National Institute of Standards and Technology (NIST) Standard Reference Materials Program. Numerous laboratories rely on them for elemental analysis and qualification for ASTM C 114-00 Standard Test Methods for Chemical Analysis of Hydraulic Cement. NIST has collected new candidate materials from around the world and partnered with Construction Technology Laboratories (CTL) in their preparation and certification. This paper describes the procedures taken at NIST and CTL to prepare and test materials for certification including the homogeneity testing, the X-ray fluorescence methods and the statistical data analysis performed for value assignment.     

硼酸使掺铁铝酸锂发光增强的现象

在硼酸存在下合成了掺铁铝酸锂荧光体,研究了在不同温度下硼酸加入量对荧光体发光强度的影响,并通过X射线粉末衍射和粒度分析,初步探讨了发光增加的原因。     

Partial Oxidation of Methane to Syngas over Calcined Ni–Mg/Al Layered Double Hydroxides

The catalytic partial oxidation of CH₄ to syngas was carried out over an Ni–Mg/Al mixed-oxide catalyst prepared from layered double hydroxide-type precursors. The catalysts were characterized by XRD, TPR, UV-DRS, XRF, BET and CHNS analysis. The effects of the catalyst composition and the calcination temperature on the catalytic performance and the extent of catalyst deactivation were investigated. Ni–Mg/Al oxide catalysts converted CH₄ into syngas efficiently with high selectivity. The catalyst performance was strongly related to the Ni particle size and the calcination temperature. The catalysts that were calcined at higher temperature exhibited a better catalytic performance. In conclusion, the NiAl₂O₄ spinel phase had a positive effect on the stability of the catalyst.     

长链羧酸铕四元配合物的合成及其发光性质

合成了铕与长链羧酸、二苯甲酰甲烷、邻菲啰啉形成的四元配合物,用元素分析、红外光谱、核磁共振氢谱和紫外光谱对所合成的铕四元配合物进行了表征。由于长链羧酸的引入,铕配合物在氯仿等挥发性有机溶剂中具有良好的溶解性,这为今后与高分子基体复合创造了条件。铕配合物在342nm光波激发下,发出以铕的特征发射谱线612nm左右为主的强荧光。     

铝酸钠溶液分解反应研究

为了研究氧化铝生产过程中铝酸钠溶液的分解反应动力学方程及反应器的优化操作设计, 首先用络合滴定法测定了氧化铝在氢氧化钠溶液中在50~65℃范围内的溶解度, 它为研究动力学提供了基础数据, 并得出溶解度方程为: Tc/4.221857.10ln-=* 在温度精度控制在±0.1℃的间歇釜式玻璃反应器中,在温度为50~60℃、氧化钠浓度为110gL-1和起始铝酸钠浓度为1.92molL-1的条件下,进行了65~84h的铝酸钠溶液的分解反应动力学实验。通过关联实验结果确定了反应动力学方程为: ()2312)/)((/10043.83exp101664.1**--=-cccARTrttA 该方程计算值与实验值的相对误差≤5%。 将溶解度方程与动力学方程进一步应用于反应器的优化操作设计,计算表明:采用动力学方程提供的铝酸钠最优操作过程,铝酸钠的分解率能提高4%左右。     

苯丙烯酸邻菲罗啉铕钇配合物的合成及荧光特性

在乙醇介质中，合成了标题化合物，测定了其组成，红外光谱及荧光光谱，结果表明，羧酸的羟基氧及邻菲罗啉中的氮原子均与稀土离子配位，铕钇配合物的荧光强度值高于铕配合物。