Study On Preparation Of High Strength Alumina Aerogel Composites

Alumina aerogel has excellent high temperature stability besides the basic properties of aerogels. This makes it become an ideal material to preparare high temperature heat insulation material. Pure alumina aerogels, however, derived from wet gel followed drying, generally have poor mechanical properties and tend to break into fragments, which severely restricts the practical application and commercial production. Attapulgite (ATP) is a type of rare natural hydrated magnesium aluminum silicate clay mineral with fibrous crystal structure, layer-chain structure, possesses fine adsorptive, filling and adiabatic properties. Owing to its special crystal structure and stable physical and chemical properties, we prepared reinforced ATP/Al2O3 aerogel composites via directly ambient pressure drying.Firstly, the effects of sol-gel parameters such as volume ratio of water and ethanol, molars ratios of propylene oxide (PO) and the adding way of attapulgites were studied. And the optimal conditions are confirmed as follows, H2O:EtOH=3:7vol, n(Al):n(PO)=1:8, and stable attapulgite suspension is required.Secondly, we studied the effect of attapulgite content on mechanical properties of alumina aerogel composites. The thermal property and bulk density were slightly improved after attapulgite was added, and the matrix density decreased significantly. The compressive strength of aerogel composites are dramatic enhanced by adding attapulgite, and the compressive strength increased from 26.74 to 75.44MPa when the attapulgite content raised from 0 to 26.09wt%. The compressive of ATP(26.09wt%)/Al2O3 aerogel composites increased almost threefold compared to the pure alumina aerogel.Finally, the reinforcing mechanism of ATP on alumina aerogel was put forward. Comparative analysis of pure Al2O3 aerogel and ATP(26.09wt%)/Al2O3 aerogel composites was performed, including phase composition, microstructure, surface area and thermal stability. SEM and TEM analysis show that alumina aerogel particles are just closely adhered to attapulgite sticks. It indicates that the alumina aerogel matrix still exhibits nono-porous network structure, and the attapulgite plays a role of skeleton which can improve the mechanical property. Specific area and pore structure parameters of different aerogels with different temperature heat treatment show that ATP can effectively inhibit sintering of alumina particles, which indicates that ATP/Al2O3 aerogel composites are more suitable for use at high temperatures. After adding ATP, specific surface damage reduced from 43.94% to 34.37%, pore volume loss decreased from 48% to 7.34%. We found that the alumina aerogel still retain its original crystal structure through XRD, FT-IR, TGA analysis. It indicates that the addition of ATP won’t degrade the alumina aerogel some basic properties, such as used as catalyst and catalyst carrier properties and thermal stability, etc.