Papers by Keyword: Silica Matrix

Abstract: mplant fixation is correlated with direct bone apposition on the implant surface. In a former study it was reported that a new coating material enhances the bone-to-implant-contact in comparison to machined and rough surfaces. This study is aimed at clarifying the effect of an enhanced bone-to-implant-contact that is induced by a new coating material. The coating is produced by spin and spray coating and consists of a silica matrix, in which nanocrystalline hydroxyapatite is embedded. The coating material exhibits a high porosity in the micrometer and nanometer scale. Coated implants were inserted subcutaneously in Wistar Rats. The specimens were excised after 6 and 12 days. EDX and SEM analysis showed a reduction of the silica amount within 6 days. In accordance to former results of a bone grafting material with the same structure, this matrix change is responsible for an initial bone formation at early stages.

Abstract: The apposition of bone at early stages is critical for rapid loading and therefore there is much effort in improving the implant surfaces for a rapid osseointegration. The aim of this study is to investigate the effect of roughness, hydrophilicity and coating on osseointegration. Machined (smooth), sand-blasted (rough), hydrophilic and coated implants were tested in vivo for 2, 4 and 6 weeks. The hydrophilic surfaces were obtained by atmospheric oxygen plasma treatment of machined and sand-blasted implants. The coating is obtained by a spin-spray-process using sol-gel-technique. SEM and TEM investigations revealed that the coating consists of a nanoporous silica matrix with embedded synthetic, nanocrystalline hydroxyapatite. Histological polished sections were manufactured and the bone-to-implant-contact was calculated. The difference between smooth and rough implants was marginal and not significant. There were no statistical differences between hydrophilic and control implants, whereas the BIC of the hydrophilic surfaces was lower by trend. All coated implants offered an increased bone to implant-contact. However, the BIC was decreasing at 6 weeks due to the missing of mechanical stress and a faster bone metabolism in rabbits. The coating offers a new opportunity to enhance the osseointegration and therefore an earlier implant loading.

Abstract: To address the issues of poor thermal conductivity and fragmentation of metal hydride particles undergoing hydriding/dehydriding reactions, a metal hydride-based composite material was developed. The active metal phase was embedded in a silica matrix and a graphite filler was incorporated by ball milling. A set of compact pellet samples at different composition were prepared and tested. Experimental data obtained from the thermal conductivity measurements shown that using powder graphite produced a quite linear increase in the thermal conductivity of the metal hydride – silica composite. Ongoing studies include composition optimization as well as long-term testing upon cycling of such metal hydride composites to evaluate their potentiality in technological hydrogen storage applications.

Abstract: A novel technique was developed to synthesize porous silica–matrix ceramics from silicon carbide and alumina with an Y2O3 addition, using pine sawdust as a pore former. The porous ceramics were fabricated at temperatures of 1300–1500 oC in air by a reaction–bonding process based on two reactions: (1)SiC+2O2→SiO2+CO2 (Oxidation) and (2)2SiO2+3Al2O3→3Al2O3·2SiO2 (Mullitization). Reaction–bonding behavior, mechanical property and open porosity were investigated as a function of Y2O3 content as well as sintering temperature and holding time. Moreover, phase composition and microstructure of the porous silica–matrix ceramics were studied by X–ray diffraction (XRD) and scanning electron microscopy (SEM).