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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Crystallization of amorphous silicates far from equilibrium part I: A versatile nitrate-based sol-gel synthesis of amorphous porous Ca,Mg-rich silicates
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Crystallization of amorphous silicates far from equilibrium part I: A versatile nitrate-based sol-gel synthesis of amorphous porous Ca,Mg-rich silicates

机译：非晶态硅酸盐的结晶远未达到平衡部分I：多种多样的基于硝酸盐的溶胶-凝胶法合成非晶态多孔富含Ca，Mg的硅酸盐

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An easy-to-use, comprehensive sol-gel method is developed to produce amorphous calcium and magnesium silicates from nitrate precursors and TetraEthOxySilane (TEOS). Final products were designed to suit basic prerequisites of starting materials for experimental investigation of crystallization around the glass transition temperature range. After gelification, thermo-gravimetric methods and infrared-spectroscopy were used to follow dehydration, decarbonation and denitrification of the xerogel. A temperature of 500 °C is found to successfully remove volatiles without causing crystallization. The microstructure revealed by transmission electron microscopy (TEM) consists of 10-20 nm individual mesoparticles of 10-20 nm. Samples annealed at 500 °C were found entirely amorphous at the TEM scale. The porosity observed by TEM and characterized by nitrogen adsorption-desorption is homogeneous and varies from 4.6 to 8.5 nm as a function of the composition. Bulk analyses by ICPMS and local analyses by EDS-TEM demonstrate that the stoichiometry can be achieved and the homogeneity is confirmed at least down to 100 × 100 nm. At lower scale, irradiation by the electron beam produces a significant volatilization of Ca and Mg, which makes chemical analyses unreliable. Pros and cons of the method and special cares for specific applications are discussed. The method was also successfully used to produce a wider range of amorphous analogs having complex compositions or containing trace elements for applications in the field of mineral physics and chemistry.
机译：开发了一种易于使用的综合溶胶-凝胶法，可从硝酸盐前体和四乙氧基硅烷（TEOS）生产非晶态硅酸钙和硅酸镁。最终产品的设计符合原材料的基本前提条件，用于玻璃化转变温度范围内的结晶实验研究。胶凝后，使用热重法和红外光谱法跟踪干凝胶的脱水，脱碳和反硝化。发现500°C的温度可成功去除挥发物，而不会引起结晶。透射电子显微镜（TEM）揭示的微观结构由10-20 nm的10-20 nm的单个中观粒子组成。发现在500°C退火的样品在TEM尺寸下完全为非晶态。通过TEM观察并以氮吸附-解吸为特征的孔隙率是均质的，并且作为组成的函数在4.6至8.5nm之间变化。通过ICPMS进行的批量分析和通过EDS-TEM进行的局部分析表明，可以实现化学计量，并且至少在100×100 nm范围内可以确认均匀性。在较小的规模下，电子束的照射会导致Ca和Mg的大量挥发，这使化学分析变得不可靠。讨论了该方法的优缺点以及针对特定应用的特别注意事项。该方法还成功地用于生产范围更广的具有复杂组成或含有微量元素的无定形类似物，用于矿物物理和化学领域。

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