Ni, Ti, and NiTi laser ablation in vacuum and in water to deposit thin films or to generate nanoparticles in solution

Abstract

An ns Nd:YAG pulsed laser was used to deposit thin films in a vacuum and to generate nanoparticles in the water of Ni, Ti, and NiTi alloys. Laser ablation was measured in terms of removing mass per laser pulse. The laser-generated plasma in vacuum was characterized in terms of temperature and energy of emitted particles. The ablation in water produces nanoparticles with dimensions of the order of 25 nm and solutions with concentrations of the order of some mg/ml. The NiTi alloy stoichiometry is well reported in the deposited thin film and in the composition of the produced nanoparticles. K E Y W O R D S nanoparticles, Ni, NiTi, nitinol, thin films, Ti 1 INTRODUCTION Ni, Ti, and the NiTi alloys have been investigated for many years because of their special chemical and physical properties. Ni is ferromagnetic, corrosion resistant, and applicable as a coating, and it is used in many metallic alloys to confer specific properties. [1] Ti reacts with oxygen, it is mechanically resistant and light, biocompatible, corrosion resistant, and used to realize many alloys. [2] The NiTi alloy shows unique shape-memory and super elastic properties due to its reversible transition between martensitic and austenitic phases depending on the temperature and stress effects. [3] Even though nickel is considered toxic, the nickel-titanium alloy is biocompatible due to the high reactivity of titanium in oxygenated environments and the formation of passivized TiO 2 surface layers; thus, this alloy is used in biomedicine to build orthodontic files, orthopaedic hooks, and many types of prostheses. [4] Our interest in this alloy is derived from its possible applications in the biomedical field for the construction of small orthopaedic prostheses, for interface films between titanium prostheses and other types of supports, and for the possibility of using NiTi nanoparticles for cytotoxicity of Ni in some cell cultures and for their insertion in tumour tissues before adequate radiation therapy with ionizing radiation. These materials are used separately as pure Ni and Ti or together as Ni 55%-Ti 45% atomic stoichiometry, in the shape of bulk, wires, thin films, and-more recently-as nanoparticles. The nanoparticle realization of Ni, Ti, and NiTi is interesting due to the unique properties offered by the large surface-to-volume ratio, which increases with decreasing particle size. Nanoparticles (NPs) based on Ni, Ti, and NiTi are used to study cellular adhesion, Ni toxicity, and Ti biocompatibility and to characterize the chemical and physical NiTi alloy properties by changing their atomic stoichiometry. [5] High interest in synthesizing Ni, Ti, and NiTi nanoparticles came from their potential use in many applications. For example, such NPs can improve the wetting ability of solid surfaces, enhance the interface adhesion, be embedded in polymers to change their optical and electrical properties, be inserted in biological environments, realize molecular markers for nuclear magnetic resonance imaging, and other applications. [6,7]

Laser-Assisted Synthesis and Oxygen Generation of Nickel Nanoparticles

“…Additionally, the authors showed that applying magnetic field indicates the possibility of controlled particle separation, depending on their size. The morphology of NiNPs obtained via PLAL technique was also reported by Torrisi et al [30]. The NPs were produced for 20 min using the 1064 nm wavelength and it was shown that the concentration decreases with the increased fluence and process duration as the laser light is absorbed in the solution, leading to the partial fragmentation of NPs and hence the reduction in mean size distribution.…”

Sub-picosecond laser surface modification of Ti–Ni alloy and its antibacterial activity

“…Although nickel is considered a toxic metal [5], the nickeltitanium alloy is biocompatible due to the high reactivity of titanium in oxygen-saturated environments and the formation of passivated TiO 2 surface layers [6]. The scientific and technical development of the Ti-Ni alloy for biomedical applications is well described [7].…”