Laszlo Jakab-Farkas

Effect of Surface Preparation and Passivation Treatment on Surface Topography of Ti6Al4V for Dental Implants

The major goal of our research work is to develop an effective and efficient procedure to prepare surfaces with an average surface roughness Ra of 1...2,5 μm and a proper surface topography, as the morphology of dental implant surface is of extreme importance in the process of implant osseointegration. The aim of present research was to elucidate the effect of surface preparation and passivation treatment on topography of Ti6Al4V surfaces for dental implants, and to perform an efficient procedure, in terms of process time. Thirty samples were prepared, some samples were subjected to sand blasting, all samples were acid etched using a dual bath of H2SO4 1n and HCl 1n (1:1) at different temperatures (60°C, 80°C, and 100°C) using different process durations (1 h, 3 h, 6 h, 12 h, and 24 h). After acid etching procedure some samples were passivated in 30% HNO3 at room temperature, for 15 min. Scanning electron microscopy was performed in order to characterize the topography of the surfaces. We found that sand blasting and passivation treatment promotes the formation of a proper surface topography with large, smooth valleys (∼50 μm), different size large peaks (∼30 μm), and micropores (<10 μm) opened on the surface of valleys and peaks, required by a good osseointegration. We showed that the same proper morphology can be achieved by acid etching at different temperatures, using different process duration. The most efficient procedure takes place at 100°C, with process times of 1...3 hours.

Morphology of Nanostructured TiO 2 Surfaces for Biomedical Implants Developed by Electrochemical Anodization

Ti6Al4V alloy is widely used for biomedical implants, and the modification of its surface, at nanoscale level, is a method to enhance its osseointegration. We modified the Ti6Al4V surface, with an initial micro rough topography, by using electrochemical anodization in 1M H3PO4 + 0.5 wt% HF electrolyte, and anodization potential of 20 V. By using short anodization duration, 5 min, or 15 min, the oxide layer presents a nanoporous morphology, and do not cover the entire surface. At an anodization time of 30 min, our results demonstrate the synthesis of continuous, highly ordered nanotubular TiO2 layer (diameter of nanotubes: 25-90 nm, thickness of the layer: 350-450 nm), superimposed over a micro rough topography, the oxide layer exhibiting a good adherence to the substrate, coherence and no brittleness. Anodization time of 2 hours provides the results very similar with those obtained at 30 min in terms of nanotubular layer topography, but some drawbacks appear in terms of surface coverage and continuity of the layer.

Optimization of Reactive Sputtering Technology for Hard Coatings Deposition

The paper presents the research work carried out in order to optimize the technology and reactive magnetron sputtering system used for the deposition of hard, multielemental, multiphase coatings. On the basis of a model of dynamic pressure developed and validated by us, regulatory structures for dynamic pressure inside the deposition chamber were designed and implemented. By using this optimization, extensive experiments involving nanostructured (Ti, Al, Si)N coatings, with a thickness of approx. 2 μm, were carried out. Using TEM microscopy, SAED and Vickers microhardness characterizations the results of deposition system optimization on the microstructure and microhardness of thin films were investigated.

Multilevel Distributed Embedded System for Control of the DC Magnetron Sputtering Process

Abstract The paper presents in detail a unique multilevel control architecture designed for the comprehensive management of the DC magnetron sputtering process and of all subsystems of the sputtering equipment. The ultimate goal is to increase the repeatability, stability and the controllability of the complex process. The presented topics include embedded and distributed electronics, data acquisition and supervisory control, networking, data management, redundant local and remote data-archiving. There are presented platform independent algorithms managing the data exchange between computational devices, and conclusions are drawn regarding the efficiency of the various algorithms used.

Macroscopic Thin Film Deposition Model for the Two-Reactive-Gas Sputtering Process

Abstract The presence of a second reactive gas in the magnetron sputtering chamber makes the process much more complicated, and the process control much more difficult than in the case of a single reactive gas. Macroscopic models have been developed in order to explain the complex phenomena and to provide support for the process control. These models are able to explain the nonlinearities of the process and the strong coupling between the control channels. This paper introduces a model created with the intention to of gaining a good grasp of the process, especially regarding the conditions necessary to obtain the required stoichiometry of the film deposited on the substrate. For this purpose, we modelled the formation of the desired ternary compound both directly from the available particle fluxes and from intermediary compounds. The surface of the substrate is divided into eight dynamically variable regions, covered by different compounds, each exposed to the streams of five types of particles. We present the analytical model and provide simulation results in order to demonstrate its capability toof describeing the nonlinear phenomena, which that characterisze the two-gas sputtering process.

Effect of Oxygen Doping on the Structure of TiN Surface Coatings

Abstract In the present work the influence of the level of oxygen doping on the structure of TiN films was investigated by dedicated experiments. The films were deposited at 400°C in an all metal UHV device by unbalanced magnetron sputtering at the same Ar and nitrogen flow rates, but the oxygen flow rate was changed in the experiments, incorporating oxygen in the range of 4 and 20 at.%. The structure of the films was investigated by XRD, Auger electron (AES) and X-ray photon electron (XPS) spectroscopy and transmission electron microscopy (TEM). The results discovered the crystal face anisotropy in the incorporation-segregation of oxygen leading to the change of the <111> texture to <002>. The structure analysis revealed that the <002> texture is developing also by competitive growth of crystals, which is the result of the limitation of the growth of the <111> oriented crystals by the TiO2 layer developing on their growth surface by the segregated oxygen species. The oxygen incorporating in the crystal lattice on the 002 crystal faces of the <002> oriented crystals is segregated by surface spinodal decomposition, developing nm sized 3D TiO-2 inclusion both in the bulk of the columns and the column boundaries.

Multilayered nanocrystalline CrN/TiAlN/MoS2 tribological thin film coatings: preparation and characterization

Nanocrystalline multilayer thin film coatings, composed of nanometer-scale thick CrN, TiAlN and MoS2 tri-layer systems, were prepared by reactive co-sputtering processes. The self-lubricated multilayer coating structures were deposited by one-fold oscillating movement of substrates in front of the sputter sources. Three independently operated direct current (dc) excited unbalanced magnetrons (UM) with rectangular cathodes of TiAl alloy (50/50%), pure chromium and MoS2 were used as sputter sources. The reactive sputtering process was performed in a mixture of Ar-N2 atmosphere. Hardened high-speed-steel (HSS) and thin oxide covered Si (100) wafers were used as substrates for tribological- and microstructure investigations, respectively. According to results of the chemical composition evaluated by Auger-electron spectroscopy (AES) and microstructure investigation by cross sectional transmission electron microscopy (XTEM), the CrN, TiAlN and the MoS2 phases form practically continuous layers with large gradient transition of composition. The as-deposited CrN/ (Al,Ti)N/MoS2 coatings have shown good friction behaviour, tested at room temperature in dry sliding condition with a ball-on-disk tribometer.