Apatite-related calcium phosphate, the main component of biological hard tissue, has good biocompatibility and is an economical material. Methods for the synthesis of apatite materials including hydroxyapatite (HAp) have previously been established. Therefore, for many years, apatite materials have been utilized as substitute materials for bone in orthopedic and dental fields. Such types of conventional substitute materials, which are implanted in the human body, should ostensibly be chemically stable to maintain their quality over time. However, recent advances in tissue engineering have altered this concept. Physicians and researchers now seek to identify materials that alter their properties temporally and spatially to achieve ideal tissue regeneration. In order to use apatite materials for tissue engineering and as drug delivery systems, the materials require both a high affinity for cells, tissues and/or functional molecules (e.g. growth factors and genes) and controllable bioabsorbability. To achieve these properties, various physicochemical modifications of apatite materials have been attempted. In addition, fabrication desiring three-dimensional structures (e.g. size, morphology and porosity) of apatite materials for implant sites could be one of the crucial techniques used to obtain ideal prognoses. In this review, the latest research trends relating to the techniques for the fabrication and modification of apatite materials are introduced.
X-ray absorption fine structure (XAFS) analysis was applied to identify the chemical state of silver and zinc in the glaze of anti-bacterial ceramics. Anti-bacterial ceramics for example tile and sanitary ware are very important from the view point of hygiene. Ag and Zn have been known as inorganic anti-bacterial agents for a long time, and are widely used as raw materials for the anti-bacterial ceramics. These anti-bacterial agents were incorporated into the amorphous alminosilicate glaze. The anti-bacterial activities of the ceramics were confirmed by film covered method using Staphylococcus aureus. Ag K-edge XAFS analysis showed that the chemical state of Ag atoms in the Ag-glaze were monovalent, and the Ag-O bond length was increased compared to that of Ag20. Zn K-edge XAFS analysis showed that the chemical state of Zn atoms in the Zn-glaze were quite similar to that of Zn 2 Si0 4 .
In this study, rapid debinding of alumina molded bodies was carried out using superheated steam treatment. The superheated steam treatment was performed with a temperature increase of 10°C/min to a holding temperature range of 500°C to 800°C. The molded body after superheated steam treatment to 800°C resulted in a carbon removal rate of 99.3%. No cracking occurred in sintered bodies obtained by debinding in superheated steam and then firing at 1,600°C in air. However, many large cracks occurred in sintered bodies that had been treated in air under similar temperature conditions. Thus, it was suggested that superheated steam treatment is highly effective for rapid debinding of molded bodies. To understand the debinding behavior under superheated steam, thermal analyses were performed with thermogravimetric and differential scanning calorimetric analysis and gas chromatography in humidified atmospheres. These results suggested that the debinding in superheated steam suppressed thermal runaway and the generation of pyrolysis gas caused by the chain of exothermic reactions derived from the oxidation of the forming aid (binder).
Glass fibers and sheets were treated by the low temperature plasma process working with argon atmosphere in order to develop high performance glass fiber reinforced plastic (GFRP). In particular, surface properties, such as roughness and wetting behavior of glass fiber and sheet, were examined with plasma treatments. The surface structure of plasma-treated glass samples was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM), and the relationship between the surface structure and the wettability was discussed. Interfacial shear strength between the plasma-treated fiber and epoxy resin was evaluated. The argon plasma treatment process improved the interfacial shear strength up to 160% of the untreated samples. The nanometer-level surface roughness of glass fiber with plasma treatment played an important role in the increase in interfacial fracture behavior. It was found that the plasma treatment process was effective for fabricating high performance GFRP.
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