Multi-layer haemocompatible diamond-like carbon coatings obtained by combined radio frequency plasma enhanced chemical vapor deposition and magnetron sputtering

Radio-frequency Plasma Enhanced Chemical Vapour Deposition (in different methane dilutions) was used to synthesize adherent and haemocompatible diamond-like carbon (DLC) films on medical grade titanium substrates. The improvement of the adherence has been achieved by interposing a functional buffer layer with graded composition TixTiC1-x (x = 0-1) synthesized by magnetron co-sputtering. Bonding strength values of up to ~67 MPa have been measured by pull-out tests. Films with different sp(3)/sp(2) ratio have been obtained by changing the methane concentration in the deposition chamber. Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction were employed for the physical-chemical characterization of the samples. The highest concentration of sp(3)-C (~87 %), corresponding to a lower DLC surface energy (28.7 mJ/m(2) ), was deposited in a pure methane atmosphere. The biological response of the DLC films was assayed by a state-of-the-art biological analysis method (surface enhanced laser desorption/ionization-time of flight mass spectroscopy), in conjunction with other dedicated testing techniques: Western blot and partial thromboplastin time. The data support a cause-effect relationship between sp(3)-C content, surface energy and coagulation time, as well as between platelet-surface adherence properties and protein adsorption profiles.

Structural properties of silver doped hydroxyapatite and their biocompatibility

The aim of this study was to obtain a novel hydroxyapatite-based material with high biocompatibility. The structural properties of the samples were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The X-ray diffraction studies revealed the characteristic peaks of hydroxyapatite in each sample. Other phases or impurities were not observed. The scanning electron microscopy observations suggest that the doping components have no influence on the surface morphology of the samples, which reveals a homogeneous aspect of the synthesized particles for all samples. The presence of calcium (Ca), phosphor (P), oxygen (O) and silver (Ag) in the Ag:HAp is confirmed by energy dispersive X-ray (EDAX) and X-ray Photoelectron Spectroscopy analyses. Nanocrystalline silver doped HAp stimulated viability and potentiated the activation of murine macrophages.

Structure and magnetic properties of nanosized magnetite obtained by glass recrystallization

We present the preparation, structural and magnetic properties of nanosized magnetite obtained by the crystallization of a series of Fe-containing borosilicate glasses. Several compositions with the ratio Fe2O3/SiO2 spanning from 0.37 to 0.67 were investigated as a function of two nucleators Cr2O3 and P2O5, respectively, and modifiers and intermediates (Al2O3 and MgO). Mössbauer spectroscopy revealed the degree, the type and the location of disorder induced by a specific composition and nucleators. In addition to magnetite, it was also revealed the presence of large amounts of Fe-rich paramagnetic phases. The magnetic response is analysed in relation with the amount of Fe ions which remain dispersed in the glassy matrix as noninteracting (paramagnetic) ions. We discuss the role of the nucleators on the disorder in both tetrahedral and octahedral sites of the magnetite.

Highly adherent bioactive glass thin films synthetized by magnetron sputtering at low temperature

Thin (380-510 nm) films of a low silica content bioglass with MgO, B(2)O(3), and CaF(2) as additives were deposited at low-temperature (150°C) by radio-frequency magnetron sputtering onto titanium substrates. The influence of sputtering conditions on morphology, structure, composition, bonding strength and in vitro bioactivity of sputtered bioglass films was investigated. Excellent pull-out adherence (~73 MPa) was obtained when using a 0.3 Pa argon sputtering pressure (BG-a). The adherence declined (~46 MPa) upon increasing the working pressure to 0.4 Pa (BG-b) or when using a reactive gas mixture (~50 MPa). The SBF tests clearly demonstrated strong biomineralization features for all bioglass sputtered films. The biomineralization rate increased from BG-a to BG-b, and yet more for BG-c. A well-crystallized calcium hydrogen phosphate-like phase was observed after 3 and 15 days of immersion in SBF in all bioglass layers, which transformed monotonously into hydroxyapatite under prolonged SBF immersion. Alkali and alkali-earth salts (NaCl, KCl and CaCO(3)) were also found at the surface of samples soaked in SBF for 30 days. The study indicated that features such as composition, structure, adherence and bioactivity of bioglass films can be tailored simply by altering the magnetron sputtering working conditions, proving that this less explored technique is a promising alternative for preparing implant-type coatings.

Biomineralization capability of adherent bio-glass films prepared by magnetron sputtering

Radiofrequency magnetron sputtering deposition at low temperature (150 degrees C) was used to deposit bioactive glass coatings onto titanium substrates. Three different working atmospheres were used: Ar 100%, Ar + 7%O(2), and Ar + 20%O(2). The preliminary adhesion tests (pull-out) produced excellent adhesion values (approximately 75 MPa) for the as-deposited bio-glass films. Bioactivity tests in simulated body fluid were carried out for 30 days. SEM-EDS, XRD and FTIR measurements were performed. The tests clearly showed strong bioactive features for all the prepared films. The best biomineralization capability, expressed by the thickest chemically grown carbonated hydroxyapatite layer, was obtained for the bio-glass coating sputtered in a reactive atmosphere with 7% O(2).

ZnO particles of wurtzite structure as a component in ZnO/carbon nanotube composite

Composites based on carbon nanotubes and ZnO particles with needle shapes were prepared for applications in energy storage. Depending on the temperature (85 or 25 °C) at which the reaction between NaOH and ZnCl(2) was carried out, particles with two different morphologies: needle-shaped (NS) and double-pyramid-shaped (DPS), respectively, are obtained. Scanning electron microscopy, photoluminescence, UV-Vis absorption spectroscopy, x-ray diffraction and Raman light scattering studies reveal that the NS and DPS particles belong to ZnO with wurtzite (WZ) structure and ε-Zn (OH)(2) as precursors of ZnO, respectively. Using the ZnO/carbon nanotube composite as a negative electrode and an electrolytic solution containing LiPF(6), the charge-discharge characteristics of rechargeable lithium ions cells were determined. Additional information concerning the electrochemical reactions at the interface of the two electrodes was obtained by cyclic voltammetry.