Journal of the Ceramic Society of Japan 

About: Journal of the Ceramic Society of Japan is an academic journal. The journal publishes majorly in the area(s): Ceramic & Sintering. Over the lifetime, 6978 publications have been published receiving 59508 citations.

New design concept of structural ceramics―ceramic nanocomposites

Abstract: Ceramic nanocomposites can be divided into three categories: intergranular nanocomposite, intergranular nanocomposite and nano/nano composite. The intra- and intergranular nanocomposites were found to show the two to five times higher toughness and strength at room temperature than those of monolithic materials. The hardness, toughness, strength and fracture resistance for creep and fatigue at high temperatures as well as the thermal shock fracture resistance were also strongly improved for these composites. On the other hand, the new function such as machinability and superplasticity was observed for the nano/nano composites. The fabrication processes of these nanocomposites by sintering methods, micro and nanostructure observations, improvements of mechanical properties were reviewed and the roles of the nano-size dispersoids were discussed. Finally the new approach on structural materials design will be given.

Optical Properties and Structure of Defects in Silica Glass

Abstract: This paper reviews what is known about the structures and optical properties of point defects in silica glass and other amorphous forms of SiO2. The available structural information derives mainly from the results of electron spin resonance (ESR) spectrometry-a method which is directly applicable only to the subclass of defects which are paramagnetic. The intrinsic paramagnetic centers so far identified by ESR include E' centers (≡Si·), nonbridging-oxygen hole centers (≡Si-O·), peroxy radicals (≡Si-O-O·), and self-trapped holes. Examples of intrinsic diamagnetic defects believed to occur in silica in include neutral oxygen vacancies (≡Si-Si≡), two-coordinated silicone (O-Si-O-), and peroxy linkages (≡Si-O-O-Si≡). The most common extrinsic defects are associated with hydroxyl and chloride impurities. Radiolytically induced H0 and H2 play important roles in the post-irradiation growth and decay kinetics of defects in glasses containing_??_100ppm OH. A compendium of ESR/optical correlations taken from the literature points to the most likely origins of many defect-related optical absorption bands in the visible, ultraviolet and vacuumultraviolet spectral regions. Others of these bands have been ascribed to interstitial O2, O3 and Cl2 molecules on the basis of similarities of their spectral positions and widths to those of the corresponding species in the gas phase.

ポリマーから誘導されたケイ素系セラミックス ─合成・性質・応用に関する総説─

Abstract: This review presents the synthesis, characterization techniques, processing and potential applications of silicon-based ceramic materials derived from organosilicon polymers. The Si-ceramics are prepared by thermolysis of molecular precursors. The influence of the initial molecular structure of the precursor on the properties of the final ceramic material and its applications is discussed. The thermolytic decomposition of suitable Si-based polymers provides materials which are denoted as polymer-derived ceramics (PDCs). In particular, this procedure is a promising method for the preparation of ternary and multinary silicon-based ceramics in the system SiCNO. There is no other synthetic approach known to produce e.g. SiCO or SiCN based ceramics. In the case of PDCs route, common preceramic polymers are poly(organosilazanes), poly(organosilylcarbodiimides) and poly(organosiloxanes). One basic advantage of the PDC route is that the materials can be easily shaped in form of fibers, layers or bulk composite materials by applying processing techniques established in the plastic industry. The PDCs in general exhibit enhanced thermomechanical properties, i.e., temperature stabilities up to approximately 1500°C. Recent investigations have shown that in some cases the high temperature stability in terms of decomposition and/or crystallization can be increased even up to 2000°C if the preceramic polymer contains some amount of boron. The composition and microstructure of the PDC are a result of the molecular structure of the preceramic polymer. Therefore, the observed differences in the macroscopic properties are also closely related to the variation of composition and solid state structure of these materials.

Development of Self-Setting Calcium Phosphate Cements

Abstract: This paper reviews recent studies on self-setting calcium phosphate cements (CPC). Discussions are focused on the cement setting reactions, the products formed, the effects of the products on properties of the cement, and in vivo characteristics of CPC. Although cementation can occur in systems based on several different mixtures, data in the literature at present indicate that mixtures of tetracalcium phosphate and dicalcium phosphate (or dicalcium phosphate dihydrate) may be most desirable because they produce cements that have greater strengths and contain nearly pure hydroxyapatite. The strengths of CPC are considerably lower than ceramic calcium phosphate biomaterial and are also lower than some of the dental cements. On the other hand, the combination of self-setting capability and high biocompatibility makes CPC a unique biomaterial. Near perfect adaptation of the cement to the tissue surfaces in a defect, and an optimum resorption rate followed by new bone formation are some of the distinctive advantages of CPC. In its present state CPC appears to be suitable for a number of applications. Much remains to be done to further improve its properties to meet the requirements for different applications.