Consolidation of polymer-derived SiC matrix composites: processing and microstructure

SiC fiber reinforced SiC matrix composite (SiC/SiC composite) has been developed by polymer impregnation and pyrolysis (PIP) method, which consists of impregnation, curing, consolidation, and re-impregnation and pyrolysis. As a prospective approach to fabricate a high performance composite, consolidation conditions, such as curing temperature to make a green body, pressure and heating rate during consolidation, were systematically controlled for effective consolidation. Because of its advantage in controlling physical characteristic, polyvinylsilane (PVS) that is liquid thermosetting organo-silicic compound was utilized as the matrix precursor. Based on the pyrolytic behavior of PVS, effects of the process conditions on microstructure of the consolidated bodies were accurately characterized. To relate those microstructure with mechanical property, flexural tests were performed for the composites after multiple PIP processing. Consequently, process conditions to make a high performance composite could be appeared. Structural conditions to be optimized for further improvement in mechanical and environmental properties were also discussed.     

Phase equilibria in Fe-Cu-X (X: Co, Cr, Si, V) ternary systems

Phase equilibria on the Fe-Cu side in the Fe-Cu-X (X: Co, Cr, Si, V) system were experimentally determined over the temperature range of 1073–1273 K. Based on the present results and previous works, the thermodynamic assessments of the phase equilibria in the Fe-Cu-X system were evaluated using the Calculation of Phase Diagram (CALPHAD) method. The Gibbs energies (G) of the bcc, fcc, and liquid phases are described by the subregular solution model, and a set of thermodynamic parameters enable us to calculate various isothermal and vertical sections and the miscibility gaps of the solid and liquid phases.     

High-temperature strengths of aluminium composite reinforced with continuous SiC fibre

Aluminium alloys were reinforced unidirectionally with 30, 35, 40 and 50 vol %SiC fibres by a liquid-pressing method. The SiC fibres for reinforcement were produced from a polycarbosilane and were yarns consisting of 500 continuous filaments of length 300 m and diameter 13m, having a tensile strength of 2000 MPa. High-temperature tensile and bending strengths of the composites were examined in air in the temperature range from room temperature to 500° C. The strengths were not influenced by temperature up to 400° C, but were decreased at 500° C. The decrease is considered to be caused by the reduction in transfer efficiency of the stress accompanying the decrease in adhesion between fibres and matrix.     

Note in statistical treatment of medical and pharmaceutical data

This study highlights the essential concept in the statistical treatment of medical and pharmaceutical data. To explain the concept, artificial data generated using random numbers was analyzed, and the importance of the confidence interval and distribution of data was shown. Sole use of the standard deviation (SD) is not considered appropriate from the viewpoint of clinical treatment, because many oversights occur. It was shown by considering the confidence interval that such oversights rarely occur, and the safety level is increased. Moreover, the probability of the occurrence of outliers from the average can be calculated by the distribution of data. Thus, pharmacokinetic data for humans were examined. The results for the human data also support the importance of the confidence interval and the distribution of differences between groups.     

Elongational viscosity at a constant elongational strain rate of polypropylene melt

The measurement of elongational viscosity has been carried out with an improved elongational rheometer, sensitive to small elongational forces and measuring simultaneously the diameter of elongating samples. Force distribution was evaluated for various conditions. The method of reduced variables, successful in linear viscoelastic properties, can be applied to the temperature dependence of elongational viscosity only at small elongational strain rate. For large elongational strain rates, the elongational viscosity was found to be non-linear and a new method characterizing non-linearity was proposed. The non-linearity parameter in elongational viscosity was independent of elongational strain rate and almost independent of temperature. Non-linearity in elongational viscosity is discussed in terms of a structural change in the polymer melt.     

Effects of low casein and fish oil on hyperlipidemia and proteinuria in nephritic rats

The effects of amino acid-fortified low casein and fish oil (FO) diets on hyperlipidemia and proteinuria were studied in rats with nephrotoxic serum nephritis. After an antiserum injection, rats were maintained for 14 d on four different experimental diets: a 20% casein diet containing corn oil (CO) or FO, or an 8% casein diet supplemented with cystine plus threonine containing CO or FO. The 8% casein diets reduced urinary protein excretion in nephritic rats without inducing severe growth retardation or fatty liver compared with the basal 20% casein diets. Both the 8% casein diet and the FO diet decreased serum cholesterol, triglyceride and phospholipid levels in nephritic rats, and nonesterified fatty acid levels were decreased by FO feeding. In nephritic animals, hepatic cholesterol synthesis was decreased by the 8% casein diets compared with the 20% casein diets, and tended to be reduced by FO feeding between groups at the same casein levels. No effect of diet was observed on fatty acid synthesis among the nephritic rats. FO administration to the nephritic animals suppressed fecal steroid excretion. While lipoprotein lipase activity was unchanged among the nephritic rats, hepatic triglyceride lipase activity was reduced by either the 8% casein or FO diet. The results suggest that the hypolipidemic action of low casein diets may, at least in part, be due to reduced hepatic cholesterol synthesis and suppressed triglyceride secretion from the liver. They also suggest that the hypolipidemic action of FO may, at least in part, be due to reduced hepatic cholesterol synthesis and decreased fatty acid mobilization from peripheral adipose tissue.     

Ni_(40.5)Co_(32.5)Al_(27)马氏体合金的冷变形和再结晶行为

采用金相观察和硬度测定方法研究了马氏体Ni40.5Co32.5Al27合金的冷轧组织和再结晶行为。结果表明,马氏体Ni40.5Co32.5Al27合金有优异的冷加工能力,其临界冷轧压下量在46.2%~46.9%之间;马氏体相β′和延性γ相变形协调性好,合金经大变形后两相相界没有微裂纹。冷轧Ni40.5Co32.5Al27合金在1073K~1173K发生强烈回复,在1273K温度发生完全再结晶,随着淬火温度的升高合金中γ相体积分数不断减少,β′相晶粒不断长大。     

Development of a new continuous Si-Ti-C-O fibre using an organometallic polymer precursor

A polytitanocarbosilane, which is useful as the precursor polymer for ceramic fibre, was synthesized using polydimethylsilane, polyborodiphenylsiloxane and titanium tetraisopropoxide. The polytitanocarbosilane was melt-spun and using the continuous heat-treatment process from the polymer fibre to ceramic fibre, flexible Si-Ti-C-O fibre was produced. The density, tensile strength and Young's modulus of this amorphous ceramic fibre were found to be 2.35 g cm^–3, 3.0±0.2 and 220±10 GPa, respectively. The Si-Ti-C-O fibre retained its high tensile strength to higher temperatures (about 1200° C). The specific resistance of this ceramic fibre covered a wide range of 10⁷ to 10^–1cm. This ceramic fibre is considered to be useful as reinforcement fibre for composites.     

Acute and chronic nephrotoxicity of platinum nanoparticles in mice

Platinum nanoparticles are being utilized in various industrial applications, including in catalysis, cosmetics, and dietary supplements. Although reducing the size of the nanoparticles improves the physicochemical properties and provides useful performance characteristics, the safety of the material remains a major concern. The aim of the present study was to evaluate the biological effects of platinum particles less than 1 nm in size (snPt1). In mice administered with a single intravenous dose of snPt1, histological analysis revealed necrosis of tubular epithelial cells and urinary casts in the kidney, without obvious toxic effects in the lung, spleen, and heart. These mice exhibited dose-dependent elevation of blood urea nitrogen, an indicator of kidney damage. Direct application of snPt1 to in vitro cultures of renal cells induced significant cytotoxicity. In mice administered for 4 weeks with twice-weekly intraperitoneal snPt1, histological analysis of the kidney revealed urinary casts, tubular atrophy, and inflammatory cell accumulation. Notably, these toxic effects were not observed in mice injected with 8-nm platinum particles, either by single- or multiple-dose administration. Our findings suggest that exposure to platinum particles of less than 1 nm in size may induce nephrotoxicity and disrupt some kidney functions. However, this toxicity may be reduced by increasing the nanoparticle size.     

Thermodynamic Assessments of the Ag-Ni Binary and Ag-Cu-Ni Ternary Systems

The phase diagram of the Ag-Ni binary system has been evaluated by using the calculation of phase diagrams (CALPHAD) method based on experimental data of the phase equilibria and thermodynamic properties. Gibbs free energies of the liquid and fcc phases were described by the subregular solution model with the Redlich–Kister equation. On the basis of the thermodynamic parameters of the Ag-Ni, Ag-Cu, and Cu-Ni systems, and experimental information of the phase equilibria in the Ag-Cu-Ni system, the thermodynamic assessment in the Ag-Cu-Ni system was carried out. The calculated results in both the Ag-Ni and Ag-Cu-Ni systems are in reasonable agreement with experimental data.