Silica powder preparation, research

Around 1970, three different groups in the field of inorganic materials published research results on preparation of glass and ceramics via solutions or sol-gel route. H. Dislich prepared a pyrex-type borosilicate glass lens by heating a compact of metal alkoxide derived powder at temperatures as low as 650°C. R. Roy prepared a milhmeter-size small piece of silica glass via sol-gel route at temperatures around 1000°C. Mazdiyasni et al. showed that well-sintered, dense ferroelectric ceramics can be obtained at temperatures as low as 900°C, when sol-gel powders prepared from solutions of metal alkoxides are employed for sintering. 

Several solid surfaces, such as filter paper, sodium acetate, and silica gel chromatoplates with a polyacrylate binder, have been used in solid-surface luminescence work (1,2). Experimentally it is relatively easy to prepare samples for analysis. With filter paper, for example, a small volume of sample solution is spotted onto the surface, the filter paper is dried, and then the measurement is made. In many cases, an inert gas is passed over the surface during the measurement step to enhance the RTF signal. For powdered samples, the sample preparation procedure is somewhat more involved. Commercial instruments can be readily used to measure the luminescence signals, and a variety of research instruments have been developed to obtain the solid-surface luminescence data (1,2). 

Powder X-ray profiles of silicalite-1 prepared by various research workers, during their preparation of molecular sieves by isomorphously substituting the T element by titanium, tin, zirconium, vanadium, chromium, molybdenum, differ in their crystallinity (80-95%) and their unit cell volume values (Table 1). It is obvious from the Table that whenever a metal ion is being substituted, a metal free all silica polymorph should also be prepared for deciphering the unit cell expansion. The variation in the unit cell volume obtained by various workers is an indication of the inherent problems in synthesising zeolites and molecular sieves with repeatable metal substitution in the framework. 

Titania-supported vanadia catalysts have been widely used in the selective catalytic reduction (SCR) of nitric oxide by ammonia (1, 2). In an attempt to improve the catalytic performance, many researchers in recent years have used different preparation methods to examine the structure-activity relationship in this system. For example, Ozkan et al (3) used different temperature-programmed methods to obtain vanadia particles exposing different crystal planes to study the effect of crystal morphology. Nickl et al (4) deposited vanadia on titania by the vapor deposition of vanadyl alkoxide instead of the conventional impregnation technique. Other workers have focused on the synthesis of titania by alternative methods in attempts to increase the surface area or improve its porosity. Ciambelli et al (5) used laser-activated pyrolysis to produce non-porous titania powders in the anatase phase with high specific surface area and uniform particle size. Solar et al have stabilized titania by depositing it onto silica (6). In fact, the new SCR catalyst developed by W. R. Grace Co.-Conn., SYNOX , is based on a titania/silica support (7). 

Generally, the inorganic materials used to prepare the nanocomposites mainly include layered silicate clay, layered compounds, metal powder, and a variety of inorganic oxides. In our research works, nanosized zinc oxide, iron oxide, silica, and YIG particles were synthesized and used to prepare a variety of polymer nanocomposites, giving the composite materials many new features. This chapter based on our research discusses the methods of preparation and characterization of the polymer-inorganic nanocomposites. 

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