无定型氧化硅转变为α-方石英的振动光谱

红外和喇曼光谱是分子结构信息的重要来源，也是研究表面和催化问题的强有力手段，常用来表征活性中心及吸附物种的结构．为提高稳定性，催化剂一般都要经过焙烧处理，在焙烧过程中，载体结构可能会发生变化，有时还会形成一定的晶相．载体结构变化时，一般会伴随振动光谱的变化，因此在利用振动光谱研究催化体系时，弄清载体的振动光谱是十分必要的．二氧化硅是最常用的催化剂载体之一，但它具有比较多的结构形式，除无定型氧化硅中硅氧四面体可连接成不同的结构外，它还具有石英、鳞石英、方石英等多个晶相系列．对氧化硅的不同结构形式，…

Vibration Spectroscopy on Transformation of Amorphous Silica to-cristobalite

By calculating commercial silica at 1500℃ or adding sodium oxalate and calcinating at 850℃, α-cristobalite was obtained. The Raman and IR spectra of amorphous silica and α-cristobalite were studied. The Raman and IR spectra showed obvious changes. While amorphous silica transformed to α-cristobalite. The peak positions and peak shape changed, and new vibration mode appeared in the crystal phase. For amorphous silica, the Raman spectrum has a broad band between 210-515 cm- 1 and two weak peaks at 793 and 966 cm -1. After phase transition, the broad band split into two strong peaks at 416 and 231 cm-1, and the positions of weak peaks changed. The IR spectrum of SiO2 has two strong peaks at about 1100 and 480 cm-1 and a weak peak at 800 cm-1. For α-cristobalite, a strong new peak appeared at 620 cm-1, and the adsorption at 800 cm-1 increased considerably. α-cristobalite also has two adsorption peaks in far-infrared.