Method for preparing silicon-aluminum aerogel by using fly ash as raw material through normal pressure drying

Abstract

The invention discloses a method for preparing silicon-aluminum aerogel by using fly ash as a raw material through normal pressure drying, which comprises the following steps of: mixing, grinding and calcining the fly ash and sodium carbonate to enable acidic oxides and amphoteric oxides in the fly ash to react with the sodium carbonate, then dissolving a sintered material with hydrochloric acid, and carrying out suction filtration to obtain a filtrate, i.e. silicon-aluminum sol; settling and aging the silicon-aluminum sol to form silicon-aluminum gel; soaking with circulating water to remove chloride ions; soaking with an ethanol solvent instead of water; soaking with an organosilicon compound as a surface hydrophobic agent for surface hydrophobic treatment; and preparing the silicon-aluminum aerogel through normal pressure drying. The invention uses the industrial waste fly ash as the raw material to replace an organosilicon source with high price and a certain toxicity, and uses normal pressure drying to replace supercritical drying, so the safety performance is greatly enhanced, the production cost is greatly lowered; and the method has simple process and convenient operation and is suitable for large-scale production. The prepared silicon-aluminum aerogel can be widely applied to the fields of heat insulating materials and the like.

Description

technical field [0001] The invention belongs to silica-alumina gel, and relates to a method for preparing silica-alumina airgel by drying coal ash as a raw material under normal pressure. The prepared silica-alumina airgel is widely used in thermal insulation materials and other fields. Background technique [0002] Silica airgel is a new type of low-density, high-porosity nano-porous material with controllable structure. It has a continuous network structure. The pore size and particle diameter range are on the order of nanometers. The typical pore size is 1-100nm. , the solid-state network structure unit size is 1-20nm, the void rate is as high as 80.0%-99.8%, and the specific surface area is as high as 800-1000m 2 / g, therefore, silica airgel has unique mechanical, thermal, acoustic, and optical properties, and has a wide range of applications. However, silica airgel has poor thermal stability at high temperatures, and the long-term use temperature should not be higher ...

AI Technical Summary

Problems solved by technology

However, silica airgel has poor thermal stability at high temperatures, and the long-term use temperature should not be higher than 650°C, so it is difficult to apply in high-temperature fields

Alumina airgel not only has low thermal conductivity (30℃, 1atm thermal conductivity is only 29mW / m·k, 800℃\1atm thermal conductivity is only 98mW / m·k), but also has good high temperature thermal stability (long-term The use temperature is as high as 950°C), which is an ideal material for thermal insulation materials; however, the inherent strength of alumina airgel materials, high brittleness, poor ability to block infrared radiation, and difficulty in forming limit the alumina airgel materials. Applications in industry

[0003] In order to obtain porous silicon-aluminum composite aerogels, the method currently used is to use existing silica gel and aluminum salts as raw materials (mostly adopt tetraethyl orthosilicate and aluminum nitrate), according to sol-gel and supercritical drying However, this raw material is relatively expensive and has certain toxicity, and supercritical drying requires the use of an autoclave, which is complicated in process, high in cost, and has certain dangers