Sintering of most ceramic and composite materials are only possible at temperatures over 1000℃ due to their high melting point. Sintering is acknowledged as an expensive process, which takes several hours to several days. In addition, high temperature sintering affects the final product by causing undesired grain coarsening or changing the initial chemical stoichiometry. Our research group has proposed a “non-firing sintering”, where no firing process is required for achieving high densities. The underlying idea of this method involves the chemical activation of powder surface via ball milling, where the surface of particles is rubbed against balls. In this review, we will introduce the mechanism of the method as well as some process know-how, with some examples. Some examples of silica simulation models are also introduced to clarify the mechanism of reaction on the silica interfaces.
Plasma nanoManufacturing process is a novel physicochemical processing system consisting of plasma chemical vaporization machining (PCVM) for shape creation and plasma-assisted polishing (PAP) for surface finishing. PCVM enables us to make an arbitrary free form with nanometer order shape accuracy for optical components by numerically controlled scanning of localized plasma. In the case of PAP, surface of the substrate is modified by irradiation of atmospheric pressure plasma, and modified soft layer is removed by soft abrasive. And damage-free surfaces with subnanometer order surface roughness for difficult-to-polish materials, such as wide-gap semiconductor and functional engineering ceramics, are obtained by applying PAP. In this paper, the outline of plasma nanoManufacturing process and some results are introduced.
Because self-healing ability can overcome the fatal weakness of ceramics, research and development of self-healing ceramics is expected as one of key technologies that can greatly expand the application of ceramics. One of the promising uses of self-healing ceramics is a sliding member. However, research on the effect of self-healing ability on tribological properties has not yet progressed. Likewise, no self-healing ceramics suitable for sliding members has been developed. To develop self-healing ceramics suitable for a sliding member, it is necessary to prove and demonstrate a new self-healing mechanism. Therefore, basic findings on self-healing ceramics will be introduced in this paper. Therefore, the paper will exhibit the research history of self-healing ceramics and the classification and mechanism of self-healing materials including self-healing ceramics. Finally, the possibility of self-healing ceramics for sliding members considered by the authors will be introduced.
There are many kinds of ceramics and they show various characteristics. Among them, those that make use of superior mechanical properties and heat resistance properties are called engineering ceramics. In particular, engineering ceramics including Al2O3, ZrO2, Si3N4 and SiC has features of high mechanical and heat resistance properties. They are applied to wear-resistant and heat-resistant members, cutting tools and so on. This paper introduces engineering-ceramic applications to rolling and sliding elements such as rolling bearings, ball screws, artificial joints, and water-lubricated bearings. In addition, it refers to recent research topics on high-performance engineering ceramics.
Ceramics are resistant to deformation, destruction and corrosion. Therefore, they are very suitable as a sealing material. Using ceramics we have solved a variety of problems and expanded the adaptive sealing region. For example DLC, which has excellent chemical stability, solved the corrosion problem in general industrial machinery. In addition, DLC has excellent tribological properties too. Using these properties and with appropriate design, DLC coatings can be used as a low friction material. SiC, which has strong mechanical properties and high thermal conductivity, has solved thermal problems in mechanical seals for the water pumps of automotive engines. Moreover, ceramics are ideal for the base materials of surface textures and functional coatings, and are expected to be used more widely in these regions in the near future.
Silicone fluids are known to have high viscosity indices, high oxidation onset temperatures, and low glass transition temperatures. Silicone characteristics make those fluids appealing for use as lubricants in extreme temperature applications, and where lubricant longevity is desired. Despite thermal and oxidative benefits, silicone lubricants have a reputation as being poor lubricants in metal-to-metal applications, and are typically only selected for use in plastic applications. Most industrial knowledge about silicone lubricants is based on characteristics of polydimethyl siloxanes, in which case, lubricity limitations do exists. However, other silicone based lubricating fluid technologies have been commercially available for decades that far exceed known lubricity performance of PDMS. Phenyl-methyl siloxanes are great low temperature lubricants, and fluoro siloxanes have increased lubricity performance over polydimethyl siloxanes, even in metal-to-metal applications. New siloxane-based materials combine thermal stability of phenyl-methyl siloxanes and lubricity of fluoro-siloxanes. This article will focus on characterization of new phenyl-fluoro siloxane copolymer fluids, development of greases based on new silicone chemistry, as well as applications.