Current state of the art of R&D to realize fabrication of diamond wafer is summarized with its motive force for the industrial applications. Among several artificial methods to grow diamond crystals, microwave plasma chemical vapor deposition is the most widely adopted method for electronic and quantum applications. Several trials to improve the growth rate and to enlarge size of the seed crystals were proposed. In addition to the growth technique, its processing technique to dope the impurities for electronics and spintronics applications have been also developed to control the conductivity and sensitivity of the spin-related quantum information. At present, diamond is produced mainly for mechanical application and gemstones. Based on its material constants superior to those of other semiconductor materials, diamond has been interested in the field of the power electronics. On the other hand, use of the nitrogen-vacancy center is recently interested in the field of spintronics applications, because one may be able to use its quantum information under steady state. In addition, its high thermal conductivity is expected to be very useful to avoid heating up of the power devices made of, such as GaN. Realization of these attractive applications require further developments of the growth and processing techniques and clarification of the targets in these applications.

Detonation nanodiamonds are minute carbon particles synthesized by detonating explosives in a closed chamber. Their average primary particle diameter is 4-6 nm and they have a unique structure consists of a sp³ diamond core wrapped with a sp² amorphous carbon shell. In addition to the excellent mechanical and optical properties inherited from bulk diamond, they are spherical carbon materials with a high specific surface area and a surface that can be terminated by various functional groups. As an application that makes full use of these features and characteristics, the use in lubrication as oil additives that achieve low friction and wear resistance is highly expected. In this paper, the production method of nanodiamonds via detonation and the characteristics of the obtained nanodiamonds are firstly introduced. To show the potential of nanodiamonds as lubricating oil additives, the advanced technologies of water lubrication and oil lubrication using nanodiamonds are introduced.

Diamond has excellent physical properties, attracts attention as a material for the next-generation semiconductor devices, cutting tool, alternative forms of cemented carbide mold and heat sink. However, diamond substrate is hard to machine because it possesses the high-hardness and high chemical inertness. In order to obtain atomically flat diamond surfaces with high efficiency,new polishing technique combined with ultraviolet (UV) irradiation or vacuum ultraviolet (VUV) irradiation have been developed. This paper presents examples of diamond substrate polishing using UV light and VUV light.

This paper introduces the mechanical properties of CVD diamonds for application as wear-resistant materials. Diamond films coated on cemented carbide substrates with different coefficients of thermal expansion are subjected to high compressive stress. Compressive stress suppresses crack openings and improves wear resistance. In addition, the mismatch of the coefficient of thermal expansion also imposes compressive stress on the substrate interface. For this reason, the compressive stress also contributes to the improvement of fatigue strength.

The electrochemical properties of Boron doped diamond (BDD) are excellent. Electrical potential window is wide comparison with conventionally used electrode materials such as platinum, and it is possible to make electrochemical reactions difficult with conventional electrode materials. Control of electrical resistance in synthesis of BDD using microwave CVD and hot filament CVD and its application to chemical electrodes were introduced. For industrial applications of electrolyzed sulfuric acid, which is obtained by electrolyzing sulfuric acid using BDD electrodes, is mainly applied to surface treatments such as plating on plastic and anodic oxide coating. For industrial use, it is necessary to control the concentration of oxidizers. Also, the possibility of measuring the concentration of oxidizers in electrolytic sulfuric acid using Raman spectroscopy was explained.

Synthetic gem quality diamonds are produced by HPHT and CVD methods. Demand for synthetic diamonds, sometime called lab-grown diamonds, is increasing, especially in the United States. The HPHT products are mainly manufactured in China, and the CVD products are mainly manufactured in India and the United States. Through careful observations with standard gemological tests and laboratory techniques, these synthetic diamonds can be confidently identified as synthetic.

In recent years, sensing technology has been attracting attention in various industrial fields, and the demand for state detection technology of rolling bearings is increasing. An acoustic emission (AE) technique is effective means for state detection of rolling bearings, because it is more sensitive than the conventional technique. In this study, the AE signals generated from tapered roller bearings when seizure occurred due to starved lubrication were investigated. The AE signal changes during the process of reducing lubricating oil were analyzed. The AE frequency spectra were mainly in the frequency range around 0.1 to 0.4 MHz, and the signal strength was increasing during the process of reducing lubricating oil. Before seizure occurred, the AE signal strength in the high frequency around 1.2 MHz was increasing. In addition, surface changes of the tapered roller bearing due to seizure were observed. Based on these results, it became clear that the direct contact of the metal surface corresponds to the AE frequency peak around 0.1 to 0.4 MHz, and the progress of adhesion corresponds to the shift of the centroid frequency to the high frequency side.

Floating bush journal bearings are widely used to support small-sized high-speed rotating machinery. When the journal rotational speed exceeds a stability threshold speed, the bearing shows self-excited vibration, which could be disappeared as the speed further increases and the bush rotational speed levels off in the case of low supply pressure. The peculiar phenomenon can be explained qualitatively by applying the hydrodynamic lubrication model with the axial oil film rupture being considered. However, the predictions are in quantitatively poor agreement with the measurements. In the present article, intending to obtain experimental results that would be useful for future improvement of the theoretical model, the authors experimentally observe the oil film by using a test apparatus of a cylindrical journal bearing that is equivalent to the inner oil film of a high-speed floating bush journal bearing. The width of the oil film is shown to gradually reduce with an increase in journal rotational speed due to air inflow into the bearing clearance, which results in the measured bush driving torque definitely lower than the theoretical one calculated from Petroff's formula. The ratio of the measured torque to the theoretical one is found to decrease with increasing journal rotational speed although the ratio does not simply decrease in proportion to the observed oil film width.