A kind of aluminum oxide nanowire airgel thermal insulation material and preparation method thereof

Abstract

The invention relates to an alumina nanowire airgel thermal insulation material and a preparation method thereof. The method comprises: preparing a dispersion of alumina nanowires with a certain aspect ratio; mixing the alumina nanowires with acidic silica sol; Stir and sonicate to mix evenly; then add a certain amount of boric acid, and get a viscous mixed solution without bubbles through a vacuum pumping process; freeze the solution under liquid nitrogen, and then freeze-dry to obtain porous alumina nanowires Airgel; the porous alumina nanowire aerogel is subjected to hierarchical high-temperature heat treatment to realize the overlapping of nano-skeleton nodes; the porous alumina nanowire aerogel is obtained. The invention adopts aluminum oxide nanowires with high aspect ratio for three-dimensional overlapping, and uses silica sol and boric acid as sintering aids to realize the formation of high-temperature stable phases and the strengthening of nano-skeletons. The method of the invention is easy to prepare and has a short period, so that the nano crystal airgel has high porosity, high specific surface area and high temperature resistance.

Description

technical field [0001] The invention relates to the technical field of airgel preparation, in particular to an aluminum oxide nanowire airgel thermal insulation material and a preparation method thereof. Background technique [0002] Airgel material is a gel material whose dispersion medium is gas. It is a nanoporous solid material with a network structure composed of colloidal particles or polymer molecules. The size of the pores in this material is on the order of nanometers. . Its porosity is as high as 80-99.8%, the typical size of the pores is 1-100nm, and the specific surface area is 200-1000m 2 / g, while the density can be as low as 3kg / m 3 , The thermal conductivity at room temperature can be as low as 0.012W / m·k. It is precisely because of these characteristics that airgel materials have broad application potential in thermal, acoustic, optical, microelectronics, and particle detection. At present, the most widely used field of aerogel is still the field of heat...

AI Technical Summary

Problems solved by technology

Carbon aerogels and ceramic aerogels have good high temperature resistance, but there are certain limitations in their application, that is, thermal insulation applications above 1400 °C can only be achieved in an oxygen-free environment, while carbon aerogels and ceramic aerogels There is no effective way to overcome the antioxidant

Oxide aerogels such as silica, alumina, and zirconia will undergo severe crystal transformation and sintering at high temperatures, leading to structural collapse, resulting in the growth of nanoparticles and the reduction of pores, so that the specific surface area of ​​the aerogel will decrease sharply. decline, greatly weakening its thermal insulation performance and failure of thermal insulation

Aiming at the limitations of oxide aerogels, related studies have carried out modification processes such as rare earth metal oxides or multi-component doping, but their effects are limited

[0004] Chinese patent application CN108249901A discloses a method for preparing a high-temperature-resistant airgel material. Although the airgel prepared by this method has good high-temperature resistance characteristics, the heat-resistant temperature is above 1000 ° C, and can even withstand high temperatures above 1300 ° C. , but the airgel material will still produce a series of phase transitions at high temperatures above 1200°C, making its specific surface area after high-temperature heat treatment small, no more than 100m 2 / g, so the high temperature insulation performance of the airgel material is not very good

However, the preparation process of the material requires sol-gel process, aging and solvent replacement, supercritical drying and other steps, which greatly increases the complexity of the preparation and prolongs the preparation cycle of the material.

Images