Synthesis of Novel Materials by Laser Rapid Solidification

High power lasers have been widely used in industry as well as in laboratory for materials surface heat treatment, cladding, welding, cutting, thin film deposition by laser ablation and so on (Bogue, 2010; Chao & Liang, 2004; Wang et al., 2008; Kruusing, 2004), but they are seldom used in the synthesis of pure bulk materials. In recent years, we explored the synthesis of pure bulk materials with a high power CO2 laser (Liang et al., 2007; 2007; 2008; 2009; Zhang et al., 2010). It is shown that a variety of materials can be successfully synthesized by laser rapid solidification (LRS). The materials synthesized by LRS exhibit unique microstructures, superior properties which may not be realized by traditional synthetic methods. Compared to the commonly used solid state reactions and wet chemical routes which are usually severe time and energy wasting or require expensive precursors, the laser synthetic technique provides a new and rapid method for the production of materials, with which tens of grams of a sample can be produced in a few or tens of seconds. In this paper we address the synthesis and characteristics of negative thermal expansion materials and ionic conductive materials using LRS. Particular attention will be paid to the unique microstructures, special or controlled phase formation and related superior properties of the materials synthesized by LRS which may not be obtained by other methods. The oriented crystalline growth dictated by heat transfer directions and the particular phases formed at high temperatures in the molten pool and pressures induced during the rapid solidification process will be discussed. Besides, many factors such as laser power, scan speed and cooling environments are shown to affect the laser rapid solidification rate and hence the pressures induced. With the help of experimental results, the influence of these factors on the cooling rate, pressures induced and the phases of final products are revealed.