Synthesis of Mullite Whiskers and Their Application in Composites

Abstract

Mullite whiskers were synthesized by a vapor-solid reaction. Mullite composition xerogels were fired at 900" to 1600°C with AIFj in an airtight container. An average whisker increased in length from 7 pm at 1100°C to 10 pm at 16OO0C, whereas an average whisker decreased in aspect ratio from 25 to 10 with increased firing temperature. The whiskers elongated to the c-axis and the side planes were the (110). A clear lattice image corresponding to (110) lattice spacing up to the edges of the whiskers was observed with high-resolution electron microscopy, and no droplet was observed on the tips of the whiskers. The chemical composition of the whiskers synthesized below 1100°C showed an apparent A120,-rich composition of about 72 mol%. Composites reinforced by 15 vol% of mullite whiskers in the matrix of 75 vol% mullite/25 vol% Y-TZP enhanced the fracture toughness compared with those materials without mullite whiskers. [

Molten salt synthesis of mullite whiskers from various alumina precursors

“…According to this principle, the formation of Al-rich mullite was ascribed to the low synthesizing temperature by MSS. In addition, the same phenomenon was observed when mullite whiskers were synthesized below 1100 • C by a vapor-solid reaction [29].…”

Glass–ceramics and composites containing aluminum borate whiskers

“…The in situ direct growth of whiskers in a glass, analogous to the creation of fluorcansite platelets in toughened glass-ceramics, is an attractive alternative method. Unfortunately, the number of oxide systems that can be exploited are limited, as oxide whiskers are usually produced by vapor-solid phase reactions [5,6]. Very recently, the formation and crystallization behavior of glasses in the Al 2 O 3 -B 2 O 3 -SiO 2 system has been investigated, demonstrating that whisker-shaped aluminum borate crystals can be obtained after thermal treatment [7][8][9].…”

Influence of silica sources on morphology of mullite whiskers in Na2SO4 flux

“…Recently, porous mullite ceramics prepared with mullite whiskers were selected as membrane reactor and hightemperature particulate filter due to its specific pore distribution [5,6]. Various processing routes have been reported for their preparation such as vapor-phase-reaction [7], thermal decomposition of minerals [8] and rare earth oxide doping [9,10].…”