Ultra-High-Speed Performance of Ball Bearings and Annular Seals in Liquid Hydrogen at Up to 3 Million DN (120,000 rpm)©

The ultra-high-speed performance of a hybrid ceramic 25-mm-bore ball bearing, as well as that of floating-ring seals with a sealing diameter of 30 mm, was determined in liquid hydrogen at speeds to 120,000 rpm, 3 million DN, under thrust loads to 3,140 N and sealed pressures to 1.7 MPaG. The bearings had Si₃N₄ balls and a single outer land-guided retainer. The hybrid ceramic bearing exhibited excellent performance at high load, contrasting with the seized all-steel bearing; however, the ceramic balls developed superficial micro-cracks due to frictional heating. Effective cooling of the bearing was achieved by increasing the jet speed through the nozzles. The bearing power loss drastically increased with increasing speed and cooling flow rate. The critical load capacity without bearing damage was also evaluated. Furthermore, the sealing performance of the one-ring seal was superior to that of the two-ring seal in preventing the sealing ring seizure against the runner.     

Spectrometry and Performance Characteristics of a BGO–ФЭУ-165 Scintiblock in a Temperatire Range of +25 to –140°C

The possibility of the joint operation of a -165 photomultiplier based on microchannel plates and a BGO crystal, which are cooled to a temperature required for the operation of a semiconductor Ge detector, is investigated taking into account the temperature dependence of proper PMT characteristics. The system was cooled from room temperature to –140°C for 8 h. The limiting temperature at which the PMT holds its serviceability was determined, and the temperature changes in the spectroscopic characteristics of the system (the energy resolution and signal-to-noise ratio) were studied.     

Wear test of cemented tungsten carbide at high atmospheric temperature (400°C)

Cemented tungsten carbide–cobalt (WC–Co) alloy has good mechanical properties, so it is widely used for cutting tools, wear-resistant dies and rolls, and shock-resistant punching dies. In this study, a wear test between cemented WC–Co alloy and carbon steel is carried out using a pin-on-disc wear-testing machine. The characteristics as to wear rate, coefficient of friction and surface roughness are investigated. Pin specimen and disc specimen surfaces are analyzed by a fluorescent X-ray analyzer. In addition, the wear characteristics of WC–Co alloy are confirmed by SEM observation of the microstructure of the cemented WC–Co alloy specimen. This revised version was published online in August 2006 with corrections to the Cover Date.     

An evaluation of cast stainless steel (CF8M) fracture toughness caused by thermal aging at 430°C

Cast stainless steel may experience embrittlement when it is exposed approximately to 300°C for a long period. In the present investigation, the three classes of the thermally-aged CF8M specimen were prepared using an artificially-accelerated aging method. After the specimens were held for 300, 1800 and 3600hrs. at 430°C, respectively, the specimens were quenched in water which is at room temperature. Load versus load line displacement curves andJ- R curves were obtained using the unloading compliance method,J _IC values were obtained using the ASTM E 813–87 and ASTM E 813–81 methods. In addition to these methods,J _IC values were obtained using the SZW (stretch zone width) method described in JSME S 001–1981. The results of the unloading compliance method areJ _Q = 543.9kj/m² for virgin materials. The values ofJ _IC for the degraded materials at 300, 1800 and 3600hrs. are obtained 369.25kJ/m², 311.02kJ/², 276.7kJ/², respectively. The results obtained by the SZW method are compared with those obtained by the unloading compliance method. Both results are quite similar. Through the elastic-plastic fracture toughness test, it is found that the value ofJ _IC is decreased with an increase of the aging time.     

In-situ TEM on (de)hydrogenation of Pd at 0.5-4.5 bar hydrogen pressure and 20-400°C

We have developed a nanoreactor, sample holder and gas system for in-situ transmission electron microscopy (TEM) of hydrogen storage materials up to at least 4.5 bar. The MEMS-based nanoreactor has a microheater, two electron-transparent windows and a gas inlet and outlet. The holder contains various O-rings to have leak-tight connections with the nanoreactor. The system was tested with the (de)hydrogenation of Pd at pressures up to 4.5 bar. The Pd film consisted of islands being 15 nm thick and 50-500 nm wide. In electron diffraction mode we observed reproducibly a crystal lattice expansion and shrinkage owing to hydrogenation and dehydrogenation, respectively. In selected-area electron diffraction and bright/dark-field modes the (de)hydrogenation of individual Pd particles was followed. Some Pd islands are consistently hydrogenated faster than others. When thermally cycled, thermal hysteresis of about 10-16 °C between hydrogen absorption and desorption was observed for hydrogen pressures of 0.5-4.5 bar. Experiments at 0.8 bar and 3.2 bar showed that the (de)hydrogenation temperature is not affected by the electron beam. This result shows that this is a fast method to investigate hydrogen storage materials with information at the nanometer scale.     

The 12C(α,α)12C nuclear resonance at 4.26 MeV and its application in RBS analysis of carbon content in thin films

The nuclear resonance in the ${}^{12}\text{C}\text{(αα)}{}^{12}\text{C}$ elastic scattering reaction at 4.26 MeV has been used to improve the sensitivity for carbon and to determine the depth distribution in thin films. The resonance response as a function of carbon content and α-energy, was studied using samples with known carbon thicknesses. The method has been applied in an investigation of the residual carbon on bare silicon wafers after the plasma cleaning of photo-resist layers.