Łukasz Cieniek

Influence of polyetheretherketone coatings on the Ti–13Nb–13Zr titanium alloy's bio-tribological properties and corrosion resistance

Polyetheretherketone (PEEK) coatings of 70-90μm thick were electrophoretically deposited from a suspension of PEEK powder in ethanol on near-β Ti-13Nb-13Zr titanium alloy. In order to produce good quality coatings, the composition of the suspension (pH) and optimized deposition parameters (applied voltage and time) were experimentally selected. The as-deposited coatings exhibited the uniform distribution of PEEK powders on the substrate. The subsequent annealing at a temperature above the PEEK melting point enabled homogeneous, semi-crystalline coatings with spherulitic morphology to be produced. A micro-scratch test showed that the coatings exhibited very good adhesion to the titanium alloy substrate. Coating delamination was not observed even up to a maximal load of 30N. The PEEK coatings significantly improved the tribological properties of the Ti-13Nb-13Zr alloy. The coefficient of friction was reduced from 0.55 for an uncoated alloy to 0.40 and 0.12 for a coated alloy in a dry sliding and sliding in Ringers solution, respectively. The PEEK coatings exhibited excellent wear resistance in both contact conditions. Their wear rate was more than 200 times smaller compared with the wear rate of the uncoated Ti-13Nb-13Zr alloy. The obtained results indicate that electrophoretically deposited PEEK coatings on the near-β titanium alloy exhibit very useful properties for their prospective tribological applications in medicine.

Influence of Sr-Doping on the Structure of LaCoO3 Thin Films Prepared by Pulsed Laser Deposition

The aim of the research was to investigate the influence of strontium on the structure thin films La1-x SrxCoO3 (x=0; 0.1, 0.2). The LaCoO3 and LaCoO3 doped by Sr films were grown by pulsed laser deposition (PLD) on Si [100] substrate using an Excimer KrF (= 248 nm). To characterize the structure and morphology of the thin films were used the SEM, AFM and XRD methods. X-Ray Diffraction analysis showed only LaCoO3 phase in the thin film not doped andLa0.1Sr0.9CoO3 and La0.2Sr0.8CoO3 phases in thin films doped by Sr. The crystallites size, calculated by Williamson-Hall plots, was smaller for films doped by Sr. The surface of the thin films was free from the drops. SEM analysis showed change of the shape of thin films as a result of doping by Sr. Highly developed layer surface was observed using the AFM microscope for thin films doped by Sr.

Microstructure and selected mechanical and electrical property analysis of Sr-doped LaCoO3 perovskite thin films deposited by the PLD technique

Abstract This work presents the results concerning microstructural, mechanical property and electrical resistance investigations of La1-xSrxCoO3 thin films produced by the laser ablation (PLD – Pulsed Laser Deposition) method on Si and MgO single crystal substrates with (001) orientation. The microstructure and chemical/phase composition analysis of the deposited films was carried out using scanning/transmission electron microscopy, X-ray diffraction and atomic force microscopy. Additionally, adhesion and nanohardness tests were performed. The investigations allowed verification of the quality of the prepared La1-xSrxCoO3 thin films and show that implementing the PLD technique makes it possible to obtain smooth and dense films with nanocrystalline structures, while preserving the composition of the bulk target. Research studies showed that by properly selecting the parameters for the PLD process it is possible to deposit films with a significantly lower amount and smaller size of undesirable nanoparticles. A specialized measuring station was used to determine the response of thin films to an oxidizing gas atmosphere. The observed decrease in resistance of the thin films in the presence of 50 ppm of NO2 oxidizing gas is typical for p-type semiconductors. This indicates that all of the produced films exhibit a sensitivity to this gas and could be used as NO2 sensors.

Effect of the Electron Energy on the Structural Evolution of Functional Perovskite La0.6Ca0.4CoO3 Thin Films Produced by the Pulsed Electron Deposition (PED) Technique

Functional nonstoichiometric La0.6Ca0.4CoO3 perovskite thin films were deposited on theepi-polished [001] MgO substrates by the electron ablation process (PED - pulsed electron deposition) in low oxygene pressure conditions (~7 x 10-3 Torr). Deposition process was performed for about 4 hours with the repetition rate of 5 Hz that gave about 72 000 pulses for each sample. By adjusting both the target-substrate distance in the working chamber (70 - 80 mm) as well as the electron energy (10 - 14 kV) it is possible to affect the microstructure and quality of obtained thin films. This paperrelates to the influence of the single pulse electron energy (discharge) on the structure of La0.6Ca0.4CoO3 thin films investigated by means of scanning electron microscopy, transmission electron microscopy and atomic force microscopy. The chemical compositions were also examined using energy dispersive spectroscopy. Multiple linear scratch tests allowed to determine the thin films adhesion to the substrates.

Microstructural Investigations of Ca and La Doped CoO Thin Films Prepared by Pulsed Laser Deposition Technique

Two types of different oxides multifunctional thin films were deposited by PLD technique on the surface of Si and MgO substrates. First of them was CoO doped with Ca content characterized by fcc (halite) structure and second one was perovskite-type LaCoO3 compound. Their microstructure, chemical/phase composition and morphology were examined by means of diverse techniques (SEM, TEM, EDS). For the surface topography observations of thin films the Atomic Force Microscopy (AFM) was applied. Nanohardness and scratch tests (adhesion measurements) were also performed for estimation of (Co,Ca)O and LaCoO3 films mechanical properties and quality. Obtained results confirm that using PLD technique it is possible to carry stoichiometric composition of different compounds from the target to single crystal substrate however the microstructure and properties of obtained thin films are highly influenced by the substrate’s material and laser ablation parameters (laser wavelength, energy density, time and target-substrate distance).