Effect of plasma gas atmosphere on hydroxyapatite-coated titanium-based implants

The study was designed to understand the influence of different atmospheres of plasma gas on hydroxyapatite-coated commercially pure Titanium (Ti) and titanium alloy (Ti-6Al-4V). Ti and Ti-6Al-4V were plasma spray-coated with hydroxyapatite in argon, nitrogen, argon/hydrogen, and nitrogen/hydrogen atmospheres. The microstructure, porosity, calcium to phosphate (Ca-P) ratio, surface roughness, and hardness of the coat were characterized using a scanning electron microscope, energy dispersive spectroscopy, image analyzer, profilometer, and Vickers hardness tester. The analyses of the coatings obtained in different plasma gas atmospheres showed variation in microstructure, morphology, porosity, surface roughness, and hardness. As the enthalpy decreased, an increase in porosity was observed in nitrogen/hydrogen, nitrogen, argon/hydrogen, and argon atmospheres, respectively. Peak Ca-P ratio was observed in argon, which is the most inert atmosphere compared to other tested plasma atmospheres. Atmospheres with high enthalpy presented an even surface with comparatively low surface roughness. Hardness value decreased with increasing porosity. The plasma gas atmosphere has a significant influence on Ca-P ratio, porosity, and microcracks of hydroxyapatite-coated oral implants.

The Effect of Plasma Gas Composition on the Nanostructures and Optical Properties of TiO2 Films Prepared by Helicon-PECVD

TiO2 films were deposited from oxygen/titanium tetraisopropoxide (TTIP) plasmas at low temperature by Helicon-PECVD at floating potential ([Formula: see text] or substrate self-bias of [Formula: see text]50[Formula: see text]V. The influence of titanium precursor partial pressure on the morphology, nanostructure and optical properties was investigated. Low titanium partial pressure ([TTIP] [Formula: see text] 0.013[Formula: see text]Pa) was applied by controlling the TTIP flow rate which is introduced by its own vapor pressure, whereas higher titanium partial pressure was formed through increasing the flow rate by using a carrier gas (CG). Then the precursor partial pressures [TTIP[Formula: see text]CG] [Formula: see text][Formula: see text]Pa and 0.093[Formula: see text]Pa were obtained. At [Formula: see text], all the films exhibit a columnar structure, but the degree of inhomogeneity is decreased with the precursor partial pressure. Phase transformation from anatase ([TTIP] [Formula: see text] 0.013[Formula: see text]Pa) to amorphous ([TTIP[Formula: see text]CG] [Formula: see text][Formula: see text]Pa) has been evidenced since the O[Formula: see text] ion to neutral flux ratio in the plasma was decreased and more carbon contained in the film. However, in the case of [Formula: see text]50[Formula: see text]V, the related growth rate for different precursor partial pressures is slightly ([Formula: see text] 15%) decreased. The columnar morphology at [TTIP] [Formula: see text] 0.013[Formula: see text]Pa has been changed into a granular structure, but still homogeneous columns are observed for [TTIP[Formula: see text]CG] [Formula: see text][Formula: see text]Pa and 0.093[Formula: see text]Pa. Rutile phase has been generated at [TTIP] [Formula: see text][Formula: see text]Pa. Ellipsometry measurements were performed on the films deposited at [Formula: see text]50[Formula: see text]V; results show that the precursor addition from low to high levels leads to a decrease in refractive index.

Effect of Plasma Gas Flow Direction on Hydrophilicity of Polymer by Small Zone Cold Plasma Treatment and Hydrophobic Plasma Treatment

Plasma treatment is the most popular surface modification process of polymers. A small cold plasma zone treatment is an important modification technique in modern industry. In this study, the effect of gas flow direction on plasma treatment was investigated. In order to decrease the plasma zone area, we added a separate cylinder to surround the upper electrode. The separate cylinder is effective in limiting the plasma discharge area, and we could find a light and dark area in the vacuum chamber. After O2 plasma treatment, the result shows that only PP nonwoven in the discharge area became hydrophilic, but the other position away from the plasma zone was not affected. The water adsorption of PP nonwoven increased from 34.8% to 537.4%. When the sample is further from the plasma zone, near the up stream of gas flow, the surface property is less hydrophilic. The water contact angle analysis of PS and glass shows the same results as those of PP nonwoven. But PET in plasma zone or dark zone (plasma zone: 75° to 31°, dark zone: 75° to 52°) both show hydrophilic property. The wettability effect in the dark zone may be due to the UV-light irradiation in the process of plasma excitation.