Friction and wear of ceramics

The adhesion, friction, wear and lubricated behaviors of both oxide and non-oxide ceramics are reviewed. Ceramics are examined in contact with themselves, other harder materials and metals. Elastic, plastic and fracture behavior of ceramics in solid state contact is discussed. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as with metals. Grit size effects in two- and three-body abrasive wear are observed for ceramics. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Surface contaminants affect friction and adhesive wear. For example, carbon on silicon carbide and chlorine on aluminum oxide reduce friction while oxygen on metal surfaces in contact with ceramics increases friction. Lubrication increases the critical load necessary to initiate fracture of ceramics both in indentation and with sliding or rubbing.     

A study on development of advanced environmental-resistant materials using metal ion processing

The development of the oxidation, wear and corrosion resistant materials that could be used in severe environmental conditions is needed. The elementary technologies for surface modification include ion implantation and/or thin film coating. Furthermore, in order to develop ion implantation technique to the specimens with three-dimensional shapes, plasma-based ion implantation (PBII) techniques were investigated. As a result, it was found that the ion implantation and/or thin film coating used in this study were/was effective for improving the properties of materials, which include implantations of various kinds of ions into TiAl alloy, TiN films formed on surface of base material and coatings in high-temperature steam. The techniques proposed in this study provide useful information for all of the material systems required to use at elevated temperature. For the practical applications, several results will be presented along with laboratory test results.     

Simple preparation of TiO2 particles dispersed activated carbons and their photo-sterilization activity

We report a simple preparation method for TiO₂ particles dispersed activated carbons and their photo-sterilization activity for E. coli and B. subtilis. The TiO₂ particles dispersed activated carbons were readily prepared by steam activation of pitch containing titanium isopropoxide Ti(OiPr)₄ or titanium acetylacetonate TiO(acac)₃. The resulting activated carbons have high BET surface area and fine TiO₂ particles are uniformly dispersed. The photo-sterilization activities for E. coli and B. subtilis were estimated by the sterilization activity for bacteria spores by irradiation of black light to the solutions containing activated carbons. The obtained activated carbons exhibited high photo-sterilization activity for E. coli and B. subtilis with short irradiation time of 15 min.     

Effects of ZnO Contained in Supported Cu-Based Catalysts on Their Activities for Several Reactions

The specific activity of Cu-based catalyst supported on Al₂O₃, ZrO₂ or SiO₂ for methanol synthesis and reverse water–gas shift reactions was improved by the addition of ZnO to the catalyst. On the other hand, the specific activity of the supported Cu-based catalyst for methanol steam reforming and water–gas shift reactions was not improved by the addition of ZnO to the catalyst.     

Femtosecond electron beam generation and measurement for laser synchrotron radiation

One of the S-band twin linacs (18L linac) of Nuclear Engineering Research Laboratory of University of Tokyo is modified in order to produce femtosecond electron single bunch for femtosecond X-ray generation via Thomson backward scattering, namely laser synchrotron radiation. Laser photocathode RF gun and chicane-type magnetic pulse compressor are installed at the S-band linac. 10 ps (FWHM) laser pulse generates 5 MeV, 10 ps (FWHM), 1 nC electron single bunch, which is accelerated up to 20 MeV in the S-band accelerating tube and compressed to 200 fs (FWHM) by the chicane. Design study has been performed by using the code of PARMELA and the installation has been finished. For precise and reliable measurement of the compressed pulse length, the comparison of measurement between the femtosecond streak camera and coherent transition radiation interferometry was carried out. Good agreement between them for 1-10 ps (FWHM) pulses was achieved. A new Michelson interferometer for the 200 fs pulse is now under construction.     

Liquid-phase diffusivity of benzene within mesoporous materials measured by a laser Raman technique

The intracrystalline diffusivities of benzene within a series of porous materials in the liquid phase (cyclohexane was used as solvent) were measured by a constant volumetric method using Raman spectroscopy at a temperature range from 323 to 393 K. Silicalite-1, mono-dispersed mesoporous silica spheres (MMSS), silica gel, γ-Al₂O₃, and SiO₂–Al₂O₃ were used as adsorbents. The intracrystalline diffusivity was calculated by parameter fitting using theoretical equations and the experimental transient change of benzene concentrations with time in response to the adsorption. The intracrystalline diffusivities of benzene within mesoporous silicas were almost the same as that within the micropore of silicalite-1, though the pore diameters of silicalite-1 and mesoporous silicas were different from each other. It is considered that the pore walls as well as the solvent molecules of cyclohexane affect the diffusion of benzene molecules in the mesopore region.     

Polyether‐segmented nylon hemodialysis membrane. VII. Studies on surface structures of various poly(ethylene oxide)‐segmented nylon membranes

The relationships of the surface morphologies to the surface chemical compositions in poly(ethylene oxide)‐segmented nylon (PEO–Ny) membranes prepared by the phase‐inversion method were studied using scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA), and static secondary ion mass spectrometry (SSIMS). The PEO–Ny's used were high semicrystalline PEO‐segmented polyiminosebacoyliminohexamethylene (PEO–Ny610), low semicrystalline PEO‐segmented poly(iminosebacoylimino‐m‐xylylene) (PEO–NyM10), and amorphous PEO‐ segmented poly(iminoisophthaloyliminomethylene‐1,3‐cyclohexylenemethylene) (PEO–NyBI). SEM observation showed that the surfaces of the PEO–Ny610 and PEO–NyM10 membranes were composed of crystalline spherulite and that the PEO–NyBI membrane surface had a nodular structure. ESCA analysis exhibited the enrichment of the PEO segment at the surfaces of the PEO–Ny610 and PEO–NyM10 membranes. On the other hand, the enrichment of the Ny segment was observed in the case of the PEO–NyBI membrane. SSIMS analysis revealed that the outermost surfaces of the PEO–Ny membranes except the PEO–NyBI membrane were almost covered with the PEO segment. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 517–528, 2000     

Chymase as a Novel Therapeutic Target in Acute Pancreatitis

Acute pancreatitis is still a life-threatening disease without an evidenced therapeutic agent. In this study, the effect of chymase in acute pancreatitis and the possible effect of a chymase inhibitor in acute pancreatitis were investigated. Hamsters were subcutaneously administered 3.0 g/kg of L-arginine to induce acute pancreatitis. Biological markers were measured 1, 2, and 8 h after L-arginine administration. To investigate the effect of a chymase inhibitor, a placebo (saline) or a chymase inhibitor TY-51469 (30 mg/kg) was given 1 h after L-arginine administration. The survival rates were evaluated for 24 h after L-arginine administration. Significant increases in serum lipase levels and pancreatic neutrophil numbers were observed at 1 and 2 h after L-arginine administration, respectively. Significant increases in pancreatic neutrophil numbers were observed in the placebo-treated group, but they were significantly reduced in the TY-51469-treated group. A significant increase in the pancreatic tumor necrosis factor-α mRNA level was observed in the placebo-treated group, but it disappeared in the TY-51469-treated group. Chymase activity significantly increased in the placebo-treated group, but it was significantly reduced by treatment with TY-51469. The survival rate significantly improved in the TY-51469-treated group. A chymase inhibitor may become a novel therapeutic agent for acute pancreatitis.     

Rapid determination of iodine value by 1H nuclear magnetic resonance spectroscopy

High-resolution ¹H nuclear magnetic resonance (¹H NMR) has been found to be an effective tool for the direct, rapid, and automated determination of the iodine value (IV) of vegetable oils, including hydrogenated oils (IV=45.9–140.2). The total time required to obtain the ¹H NMR data is about 3 min per sample. The IV is calculated from the number of double-bonded protons and the average molecular weight derived directly from the spectrum. The average of olefinic protons and allylic plus divinyl protons area was used to calculate the absolute number of double-bonded protons. The ¹H NMR results were compared with those obtained by the traditional Wijs-cyclohexane methods. The correlation coefficient between traditional IV and the novel ¹H NMR method was r ²=0.9994 for the regression equation Y=0.9885X + 2.8084, where X was the result given by the traditional method. With the proposed regression equation, IV calculated by the ¹H NMR method was within an error of ± 1 unit of the result obtained by the traditional method. The proposed method is practically viable if one can afford to have the NMR system.