In this study, the friction of eight kinds of poly(vinyl alcohol) hydrogel (PVA-H) samples has been studied under various
load and velocity conditions to elucidate the effects of PVA factors such as the degree of polymerization (DP) and the saponification
value (SV) on the tribological behavior of PVA-H. Results showed the variations of the friction properties due to the PVA
factors in the two friction conditions found for the hydrogels: elastic friction and hydrodynamic lubrication. In the elastic
friction, the larger frictions were induced by the higher values of DP and SV. In the hydrodynamic lubrication, on the other
hand, PVA-Hs with lower SV showed larger friction. The results can then be used to adjust the parameters of PVA-H in order
to get given friction properties, for instance for the friction between catheter or scalpel and PVA-H, which can be used as
a biomodel material of artery or oral mucosa, for the training of surgeons. 相似文献
This paper presents a search for Ni–Nb–Zr thin film amorphous alloys for use as optical glass device molding die materials. To efficiently search for candidate materials, we used a combinatorial method to evaluate thermal stability. First, compositionally spread Ni–Nb–Zr libraries were fabricated by combinatorial arc plasma deposition (CAPD). To evaluate thermal stability, the Ni–Nb–Zr amorphous CAPD samples in the libraries were annealed in vacuum at 723 K, representing the molding temperature for glass devices, for various time periods. The phases of the annealed CAPD samples were identified using X-ray diffractometry (XRD). From XRD identification, candidate amorphous compositions with high thermal stabilities were screened. Sputter-deposited samples with the same candidate amorphous compositions were subsequently fabricated. Other desired properties for optical glass device molding die materials, including mechanical strength, linear expansion coefficient, oxidation resistance, machinability and anti-sticking properties to molten glass, were evaluated. The investigation revealed Ni36Nb39Zr25 to be a suitable composition for a new glass lens molding die material. This material exhibited a high fracture stress, σf, of 1.3 GPa, good heat resistance, good oxidation resistance, similar linear expansion coefficient as glass, good machinability, and excellent anti-sticking properties to molten glass. 相似文献
Analyses of a high interaction closed cycle MHD generator have been performed to confirm the feasibility of the fully ionized seed concept. The results show that fully ionized seed can be realized in a full scale generator and that it has an advantage over partially ionized seed of higher adiabatic efficiency. In order to keep the plasma in a given generator stable, the results show that the seed fraction and the external load fluctuation must stay within ± 5% and ±3%, respectively. For a wider change in the external load we can also keep the plams stable if the change is so slow that we can adjust the magnetic field, the thermal input and the working gas pressure. 相似文献
Shredder dust is a residue, which is removed from valuable ferrous metals found in scrap automobile and electronic waste. It is also an industrial waste byproduct which, under legislation in place since April 1996, must be disposed of in landfill sites. One method of disposing shredder dust is by scorification, however, this is a costly process and therefore impractical. Costs could be reduced if the shredder dust had a valuable use, and, in this paper, the authors examine its effectiveness as a cement admixture.
First, molten shredder dust was crushed for use as a cement admixture. However, it was difficult to crush it completely because metallic grains were mixed in with molten shredder dust. These particles were removed by sifting and the molten shredder dust was crushed once again. Eventually, a fine 75 μm and less powder type of slag was obtained. This slag was mixed with Ordinary Portland Cement (OPC) to form a cement mortar and subsequently a mortar test was conducted. From the test results, it was found that the long-term strength of the cement did not deteriorate even when it included 30% by weight of the pulverized molten shredder dust. 相似文献
Microcrystalline silicon (μc-Si:H) thin films, which are prospective low-cost semiconductor materials, are used as photoelectrodes for the direct conversion of solar energy to chemical energy. An n-type microcrystalline cubic silicon carbide layer and an intrinsic μc-Si:H layer are deposited on glassy carbon substrates using the hot-wire cat-CVD method. The μc-Si:H electrodes are modified with platinum nanoparticles through electroless displacement deposition. The electrodes produce hydrogen gas and iodine via photoelectrochemical decomposition of hydrogen iodide with no external bias under solar illumination. Surface modification with platinum nanoparticles and surface termination with iodine improve the conversion efficiency. 相似文献
Surface wave plasma(SWP) is a kind of low temperature plasma which can be utilized for material development.In this research,argon and oxygen were used as a working gas for an SWP experiment and the influence of the plasma irradiation on a copper surface was examined.Particular,relation between the spatial characteristics of SWP and wetting characteristics was examined.As a result,it was found that spatial characteristics of the SWP affected the wetting characteristics and the oxidation characteristics. 相似文献
Even though synthetic hydroxyapatite (HAp) has a chemical composition similar to the mineral phase of bone, it is minimally
absorbed and replaced by bone tissue. This could be because HAp is composed of compactly arranged apatite crystals with homogenously
large grains. In this study, the surface and non-stoichiometry of the synthetic HAp crystals was modified by partial dissolution
and precipitation (PDP) to improve bioabsorbability of HAp. In vitro cell culture demonstrated that more osteoclasts were
activated on PDP-HAp compared with HAp. In vivo implantation using a rabbit bone defect model revealed that PDP-HAp was gradually
degraded and was replaced by bone tissue. Consistent with the in vitro results, more osteoclasts were activated in PDP-HAp
than in HAp, indicating that the former was absorbed through the stimulation of osteoclastic activity. These results suggest
that the PDP technique may have clinical utility for modifying synthetic HAp for use as superior bone graft substitutes. 相似文献
Catalytic combustion of methane was investigated on Pt and PdO-supported CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts prepared by a wet impregnation method in the presence of polyvinylpyrrolidone. The catalysts were characterized
by X-ray fluorescence analysis, X-ray powder diffraction, X-ray photoelectron spectra, transmission electron microscopy, and
BET specific surface area measurements. The Pt/CeO2–ZrO2–Bi2O3/γ-Al2O3 and PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts were selective for the total oxidation of methane into carbon dioxide and steam, and no by-products such as HCHO,
CO, and H2 were obtained. The catalytic activities of the PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts were relatively higher than those of the Pt-supported catalysts, due to the facile re-oxidation of metallic Pd
into PdO based on lattice oxygen supplied from the CeO2–ZrO2–Bi2O3 bulk. A decrease in the calcination temperature during the preparation process was found to be effective in enhancing the
specific surface area of the catalysts, whereby particle agglomeration was inhibited. Optimization of the PdO amount and calcination
temperature enabled complete oxidation of methane at temperatures as low as 320 °C on the 11.6 wt% PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalyst prepared at 400 °C. 相似文献
We investigate residual forms of hydrogen (H) atoms such as bonding configuration in poly-crystalline silicon (poly-Si) films formed by the flash-lamp-induced crystallization of catalytic chemical vapor deposited (Cat-CVD) a-Si films. Raman spectroscopy reveals that at least part of H atoms in flash-lamp-crystallized (FLC) poly-Si films form Si-H2 bonds as well as Si-H bonds with Si atoms even using Si-H-rich Cat-CVD a-Si films, which indicates the rearrangement of H atoms during crystallization. The peak desorption temperature during thermal desorption spectroscopy (TDS) is as high as 900 °C, similar to the reported value for bulk poly-Si. 相似文献