Ultra-small sepiolite fiber toughened alumina aerogel with enhanced thermal stability and machinability
- PDF / 2,755,448 Bytes
- 12 Pages / 595.276 x 790.866 pts Page_size
- 12 Downloads / 171 Views
Ultra‑small sepiolite fiber toughened alumina aerogel with enhanced thermal stability and machinability Xiaokang Zhang1 · Rui Zhang2 · Chao Zhao1
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Herein, a new sepiolite/alumina aerogel composite with outstanding toughness and machinability was prepared using AlCl3·6H2O precursor and sepiolite fibers by a specific sol–gel process and supercritical fluid drying. Sepiolite was added into the aluminum sols containing as high as 37 wt% of A lCl3·6H2O and the resulting sepiolite fibers dispersed randomly and uniformly with the lengths of 60–100 nm and diameters of 2–3 nm. With the increase in the ratio of sepiolite, the sepiolitealumina aerogel composites exhibit no shrinkage during the sol–gel process and supercritical fluid drying, while a linear shrinkage of 4.6% was observed after heat-treatment at 1000 °C. Compared with undoped alumina aerogels, the sepiolite/ alumina aerogel composites exhibit outstanding toughness and machinability on grinding, slicing and perforating. Meanwhile, the morphology, phase nature, and porosity of sepiolite/alumina aerogel composites with different sepiolite content (from 0 to 0.06 g/cm3) were investigated. Keywords Alumina aerogel · Sepiolite fiber · Sol–gel process · Morphology · Toughness
1 Introduction Alumina aerogels possess the characters of low density, high-temperature stability, high porosity, and high-surface area, and exhibit better performance in catalysis [1, 2] and thermal insulation [3] at the high temperature of 1000 °C and beyond than any other monomeric aerogels. The sol–gel method using hydrated alumina salts (primarily AlCl3·6H2O and Al(NO3)3·9H2O) [4] or aluminum alkoxides (aluminum tri-sec-butoxide) [5] as precursors is the main method to prepare alumina aerogels. Up to now, there are still some challenges that hinder their industrial applications, such as the severe shrinkages in sol–gel process, drying process and heat treatment [6–8], low mechanical strength [9], and lack of formability and machinability [10]. At the same time, the cost prefer to be lower when people try to solve the above problems. Many efforts had been made to improve the above * Chao Zhao [email protected] 1
Cixi Institute of Biomedical Engineering, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, P. R. China
School of Materials Sciences and Engineering, Shanghai Institute of Technology, Shanghai 2001418, P. R. China
2
weaknesses. Zhang [11] used a self-made acetoaceticgrafted polyvinyl alcohol as a template and dispersing agent to disperse the Al3+ ions and Al clusters that contributed to a negligible shrinkage of the aluminum gels during the sol–gel progress. Zu [12] modified the surface of alumina aerogel with trimethylethoxysilane in the supercritical ethanol drying step. Silica on the surface of boehmite could inhibit the crystal growth and the phase transition during the heattreatment at a high temperature of about 1200 °C, which led
Data Loading...
