ABSTRACT
A pulsed wire discharge (PWD) apparatus for the mass production of nanopowders has been developed. The apparatus has a continuous wire feeder, which is operated in synchronization with a discharging circuit. The apparatus is designed for operation at a maximum repetition rate of 1.4 Hz at a stored energy of 160 J. In the present study, Cu nanopowder was synthesized using the PWD apparatus and the performance of the apparatus was examined. Cu nanopowder of 2.0 g quantity was prepared in N(2) gas at 100 kPa for 90 s. The particle size distribution of the Cu nanopowder was analyzed by transmission electron microscopy and the mean surface diameter was determined to be 65 nm. The ratio of the production mass of the powder to input energy was 362 g/kW h.
Subject(s)
Copper/chemistry , Electrochemistry/instrumentation , Nanostructures/chemistry , Nanostructures/ultrastructure , Nanotechnology/instrumentation , Signal Processing, Computer-Assisted/instrumentation , Electrochemistry/methods , Equipment Design , Equipment Failure Analysis , Nanotechnology/methods , Particle Size , Powders , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
The crystallographic grain orientation of ZrB2-ZrC composites manufactured using a spark plasma sintering (SPS) method, a new sintering technique in development for poorly sinterable ceramic materials, was analysed by the scanning electron microscopy-electron backscattered diffraction (SEM-EBSD) method. Their crystallographic features have been compared with those of a conventionally sintered specimen using a pressureless sintering (PLS) method. In the composite sintered by PLS, (0001) planes of ZrB2 were orientated in the direction parallel to the specimen surface (RD) but (1010) and (2110) planes randomly orientated. In the case of SPS, (0001) planes of ZrB2 were orientated normal to the specimen surface (ND) and weakly to the RD. In both cases of PLS and SPS, ZrC grains had a randomly orientated grain structure. The distribution of grain boundary misorientation of PLS and SPS-processed composites showed the same tendency that high-angle boundaries were more prevalent than low-angle boundaries. But in the case of ZrC grains in the SPS sample, the proportion of CSL boundaries with low sigma value (3, 5, 7, 9, 11) was relatively larger.
ABSTRACT
Effects of Ni dispersions on microstructure and mechanical properties have been studied for Y2O3-stabilized tetragonal zirconia (Y-TZP)/Ni nanocomposites with Ni dispersion up to 10 vol%. Composites were successfully fabricated by reducing and hot-pressing Y-TZP/NiO powder mixtures. Fracture strength was significantly improved from 1.5 GPa for monolithic Y-TZP to 1.9 GPa for nanocomposites with a small addition of Ni (1-2 vol%). Magnetic properties of Y-TZP/Ni nanocomposites were also investigated. Magnetization curves of Y-TZP/Ni nanocomposites showed typical hysteresis loops of soft magnetic materials, whereas coercivity was much larger than that of pure Ni metal. A new function arising from magnetomechanical effects of metallic Ni is also discussed for the present nanocomposites.
Subject(s)
Crystallization/methods , Magnetics , Nanotechnology/methods , Nickel/chemistry , Zirconium/chemistry , Compressive Strength , Elasticity , Hardness , Hot Temperature , Manufactured Materials , Materials Testing , Molecular Conformation , Particle Size , Powders , Quality Control , Stress, Mechanical , Surface PropertiesABSTRACT
The activity and mass of lipoprotein lipase (LPL) in postheparin plasma (PHP) from patients with hypertriglyceridemia coupled with hypertension, impaired glucose tolerance, hyperinsulinemia were investigated in order to clarify the cause of hypertriglyceridemia and the effects of bezafibrate (CAS 41859-67-0), a novel lipid lowering agent. Eight weeks of treatment with bezafibrate (200 mg/d) lowered plasma total cholesterol and triglyceride by 7 and 39%, respectively, and increased plasma high density lipoprotein (HDL) cholesterol by 23% in the patients (n = 15). The LPL activity and mass of PHP in the patients were found to be lower than in the normal controls. The LPL activity and mass of PHP in the patients before treatment with bezafibrate (n = 15) were 2.05 +/- 1.06 mumol/ml/h and 147 +/- 45 ng/ml, respectively, whereas after treatment with 200 mg/d of bezafibrate for 8 weeks, these values were 3.62 +/- 1.30 mumol/ml/h (p < 0.01) and 226 +/- 57 ng/ml (p < 0.05), respectively. The increases of LPL mass were positively correlated with the decrease of triglyceride levels during the same period. These results suggest that the expression of LPL enzyme protein is impaired in patients with hypertriglyceridemia coupled with hypertension, impaired glucose tolerance and hyperinsulinemia, and the impaired expression of LPL recovers during treatment with bezafibrate, resulting in improvement of hypertriglyceridemia.
