Formation of γ-LiAlO2 nano-network in an Al-based metal matrix composite

We report the synthesis of a nanostructured gamma-LiAlO2 network in an Al-based metal matrix composite (MMC) by arc-melting a powder compact of Al-15wt.%Li2O. During synthesis, chemical reactions between Al and Li2O occurred, and a two-phase Al-gamma-LiAlO2 MMC was produced. The gamma-LiAlO2 was in the form of nano-network extended evenly in the Al matrix. The apparent density and Vickers' hardness number of the MMC were determined to be 2.31gcm-3 and 143, respectively, and having a relative density of 0.87. The MMC was made nano-porous by etching away Al with a 2M NaOH solution. The sizes of pores were about 150nm and the width of the branches in the gamma-LiAlO2 network was about 90nm. Atomic force microscopy revealed that the branches were composed of fine grains of 50nm in diameter. Microstructure of the network was not altered even after prolonged etching, and this suggested that gamma-LiAlO2 was chemically inert to NaOH corrosion. Specific surface area of the gamma-LiAlO2 nano-network was measured to be 79m2/g, and its porosity was determined to be 43.7%.