Generation of NiTi nanoparticles using liquid assisted laser ablation technique

Abstract

Due to their size specific and unique properties, nanoparticles materials have become increasingly popular, promising a breakthrough in the development of novel methods in biosensing, medical diagnostics, surface plasmonics (photo-voltaics applications), therapeutics, cosmetics coatings, etc. Laser ablation has shown itself as an alternative physical nanofabrication method, which offers novel opportunities to solve the toxicity problem caused by contamination with chemical precursors or additives in chemical synthesis procedures. Pulsed laser ablation is an alternative method addressing the deficits of the conventional methods (like mechanical milling and grinding, or chemical generation), offering the access to an unlimited nanomaterials spectrum, since the nanoparticles may be generated from almost any solid material. Advantages of this method are the high purity of the nanomaterial, the material variety, and the in-situ dispersion of the nanoparticles in a variety of liquids allowing safe and stable handling of the colloids. This thesis investigates the influence of laser wavelengths, laser fluences and rotation speed of the target (in the method of rotating the NiTi target during laser ablation) on the size, shape, productivity and quality of the NiTi nanoparticles, generated throughunderwater solid state Nd:YAG laser ablation technique. The experiments were performed on Ni55%-Ti45% sheet to synthesize NiTi nano-particles at three different wavelengths (1064 nm, 532 nm and 355 nm) with varying laser fluences ranging from 30-50 J/cm2 and with varying speed of the rotating NiTi target from 10 rpm to 40 rpm (rotation per minute). Synthesized NiTi nano-particles were characterized through SEM, DLS, XRD, EDS, TEM and UV-Vis spectrum. It was observed that minimum average particle size of 130 nm was investigated for the laser wavelength of 355 nm with fluence of 50 J/cm2 in case of ablation in flowing liquid (de-ionized water). The crystallinity and lattice spacing of NiTi alloy nanoparticles were confirmed from the XRD analysis and TEM images, respectively.