THEORETICAL STUDIES OF THE NATURE OF THE 2210 cm^(-1) IR ABSORPTION PEAK IN SILICON CRYSTAL CONTAINING HYDROGEN (Ⅲ)——TEMPERATURE EFFECTS OF THE PEAK SHAPEAND THE SYMMETRIC BREAKING OF DEFECT COMPLEX

It is verified that the phonon scattering process and the residual linewidthare the dominant factors of the linewidth of 2210 cm^(-1) IR absorption peak except the anomalous linewidth at 200 K. By investigating the anomalities of the peak shape and thelinewidth of the peak at 200 K, we put forward a mechanism that the T_d symmetry of defect-complex corresponding to the 2210 cm^(-1) peak can he transferred into the D_(2d) symmetry as temperature rises to above 200 K. The quantitative analysis shows that the V+4H-model is indeed of two states: The T_d configuration is stable at temperature lower than 200 K, while the D_(2d) one is stable at temperature higher than 200 K. We can draw the conclusion that the V +4H-model corresponds to the 2210 cm^(-1) IR absorption peak from the symmetric breaking mechanism, which can quantitatively fit the experimental results.

三氟丙基改性硅聚醚的合成及其消抑泡性能

以三氟丙基为氟链节,合成了氟含氢硅油(FHSi)和相对分子质量不同、结构相同的两种丙烯醇聚醚(P1和P2),并通过硅氢加成反应制备了含氟硅聚醚(FPSi)。研究了分别用试样P1和P2改性得到的FPSi的表面张力、折光率和在柴油与机油混合体系中的分散状态,考察了试样P1和P2的相对分子质量和FHSi的黏度对FPSi在柴油与机油混合体系中的消泡和抑泡性能的影响。实验结果表明,随FHSi黏度的增加,FPSi的折光率呈下降趋势,而25℃时表面张力在(25.8±0.7)mN/m内变化,明显低于起泡介质的表面张力(30.6mN/m)。FPSi在柴油与机油的混合体系中以细小微粒的形式分散,分散状态与聚醚的相对分子质量无关。随FHSi黏度的增加,FPSi消泡性能呈现变差趋势,抑泡性能有变好的趋势,FPSi的消泡和抑泡性能均优于不含氟的硅聚醚。随同种结构的聚醚链的相对分子质量的增加,FPSi的消泡性能基本不变,抑泡性能有所提高。

有机硅消泡剂的制备与表征

以含氟含氢硅油和烯丙基聚醚为原料,通过硅氢加成反应合成了含氟有机硅-聚醚共聚物(PEMSO),并采用红外光谱表征其结构。然后以PEMSO、硅膏和硅树脂为活性成分,Span和Tween为复配乳化剂,羧甲基纤维素钠为增稠剂,采用机械乳化法制得含氟有机硅-聚醚消泡剂。研究了消泡剂性能的影响因素,结果表明:制备硅膏时,疏水白炭黑优选B-260;二甲基硅油黏度优选500 m Pa·s;乳化剂的HLB值优选8,用量优选6%;增稠剂用量优选0.5%;产品的消泡和抑泡性能基本不受温度和pH值的影响;该自制含氟有机硅-聚醚消泡剂的固体质量分数为20%,摇动100次后的消泡时间为2 s,抑泡性能为10 mL,具有较好的市场前景。