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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 >Investigations on sol-gel process and structural characterization of SiO _2-P _2O _5 powders
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Investigations on sol-gel process and structural characterization of SiO _2-P _2O _5 powders

机译：SiO _2-P _2O _5粉末的溶胶-凝胶工艺及结构表征研究

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The purpose of the study is to investigate the influence of the precursors, pH of the solution and temperature on the gelation and structure evolution of the samples from the SiO _2-P _2O _5 system. Tetraethoxysilane (TEOS) was used as precursor for SiO _2 and triethylphosphate (TEP) or phosphoric acid for P _2O _5, together with water as reagent for hydrolysis reaction and ethylic alcohol as solvent. The pH of the sols was modified by adding hydrochloric acid, in the case of TEP and by adding ammonia, in the case of H _3PO _4. The samples have been prepared starting from P _2O _5/SiO _2 = 1/10 and 1/5 molar ratio, H _2O/TEOS = 1; 2; 3 mass ratios and C _2H _5OH/TEOS = 1 mass ratio. We prepared silico-phosphate samples in the 1.5-5 pH domain and we observed that in all the cases, the lowest gelation time was found in the 3.5-4.5 pH range. We found that for the same pH value samples prepared with H _3PO _4 had a lower gelation time (few days) by comparison with the samples prepared with TEP (weeks), explainable by the low rate of the hydrolysis and condensation reactions of TEP. When the amount of water was increased, the gelation time increased in the case of samples prepared with H _3PO _4 and it was not significantly changed in the case of the samples prepared with TEP. The increasing of the solution temperature up to 40-41 °C yielded a decreasing of the gelation time (hours), especially for the samples prepared with H _3PO _4 by comparison with those prepared using TEP. In all the cases, the increased amount of water resulted in an increasing of the gelation time, even the temperature was raised. FTIR and Raman spectroscopy characterization aimed at getting information about the structural changes in the case of the samples dried in air and also for those heated at 100 °C, 300 °C, 600 °C and 900 °C. Vibration modes specific for SiOEt, SiOH, hydrogen bonds, H _2O and combined vibrations have been observed, which are in agreement with those revealed in literature data. ~(31)P and ~(29)Si MAS NMR spectra gave interesting information about first surrounding of P and Si ions meaning the type and proportion of Q species and their evolution starting from the room temperature up to 900 °C.
机译：本研究的目的是研究前体，溶液的pH值和温度对SiO _2-P _2O _5系统样品的凝胶化和结构演变的影响。四乙氧基硅烷（TEOS）用作SiO _2和磷酸三乙酯（TEP）的前体，或磷酸用于P _2O _5的前体，以及水作为水解反应试剂和乙醇作为溶剂。在TEP的情况下，通过添加盐酸，在H _3PO _4的情况下，通过添加氨水来调节溶胶的pH值。从P _2O _5 / SiO _2 = 1/10和1/5摩尔比H _2O / TEOS = 1开始制备样品。 2; 3质量比，C _2H _5OH / TEOS = 1质量比。我们在1.5-5 pH范围内制备了硅磷酸盐样品，我们观察到在所有情况下，在3.5-4.5 pH范围内胶凝时间最短。我们发现，对于相同的pH值，用H _3PO _4制备的样品与用TEP制备的样品（几周）相比具有较短的胶凝时间（几天），这可以用TEP的水解和缩合反应速率低来解释。当水的量增加时，用H _3PO _4制备的样品的胶凝时间增加，而用TEP制备的样品的胶凝时间没有明显改变。将溶液温度提高到40-41°C，可以缩短胶凝时间（小时），尤其是与使用TEP制备的样品相比，用H _3PO _4制备的样品更是如此。在所有情况下，即使温度升高，水量的增加也导致胶凝时间的增加。 FTIR和拉曼光谱表征旨在获得有关在空气中干燥的样品以及在100°C，300°C，600°C和900°C加热的样品的结构变化的信息。已经观察到SiOEt，SiOH，氢键，H _2O和组合振动特有的振动模式，这与文献数据中揭示的一致。 〜（31）P和〜（29）Si MAS NMR光谱提供了有关P和Si离子的第一周围信息的有趣信息，这意味着Q物质的类型和比例及其从室温到900°C的演化。

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