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71.
A fluidized bed granulation method, pressure swing granulation (PSG), was applied to granulation of a hardmetal powder without pressing lubricants for making the upstream process of spark plasma sintering (SPS) more efficient.
The properties of the granules were examined and compared with those of spray dried granules and extruded ones under the present system using a sieve.
Spherical granules between 0.15 and 0.84 mm in diameter difficult to obtain by the spray drying were obtained with high yield. The flowability of the granules was far better than that of spray dried granules and similar to that of extruded ones. Iron contamination and oxidization during pressure swing granulation were tolerable to the real production. 相似文献
72.
Atsuhiko Yamanaka Tooru Kitagawa Masayuki Tsutsumi Toshihiro Kashima Hiroyuki Fujishiro Kimiko Ema Yoshinobu Izumi Shigehiro Nishijima 《应用聚合物科学杂志》2004,93(6):2918-2925
High strength polyethylene fiber (Toyobo, Dyneema® fiber: hereinafter abbreviated to DF) has a negative thermal expansion coefficient. Relation between fiber structure and thermal strain of DF used as reinforcement of DF reinforced plastic (DFRP) for cryogenic use was investigated. The crystallinities and orientation angles of several kinds of polyethylene fibers having different modulus from 15 to 134Gpa (herein after abbreviated to DFs) were measured by NMR and X‐ray. We obtained the parameters of the mechanical series‐parallel model composed of crystal and amorphous by crystallinity and modulus. Thermal expansion coefficients of DFs were estimated by mechanical series‐parallel model. All DFs having different modulus showed negative thermal expansion coefficients in the temperature range from 180 to 300K, and absolute values of those markedly increased by increasing tensile modulus of DF. The estimated thermal expansion coefficients showed negative values, and thermal strains showed a similar curve to observed ones mostly. Average thermal expansion coefficients in the temperature range from 180 to 300K estimated by mechanical model agreed with the observed ones. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2918–2925, 2004 相似文献
73.
Masayuki Nogami Akihiko Koiwai Takamasa Nonaka 《Journal of the American Ceramic Society》2016,99(4):1248-1254
Glasses doped with well‐controlled Eu3+ and Eu2+ ions have attracted considerable interest due to the possibility of tuning the wavelength range of the emitted light from violet to red by using their 5D0→7Fj and 5d–4f electron transitions. Glasses were prepared to dope Eu3+ ions in a Na2O–Al2O3–SiO2 system, and the changes in the valence state of Eu3+ ions and the glass structure surrounding the Eu atoms during heating under H2 atmosphere were investigated using fluorescence spectroscopy, X‐ray absorption fine‐structure spectroscopy, and 27Al magic‐angle spinning solid‐state nuclear magnetic resonance spectroscopy. The reduction behavior of Eu3+ ions was dependent on the Al/Na molar ratio of the glass. For Al/Na < 1, the Al3+ ions formed the AlO4 network structure accompanied by the Na+ ions as charge compensators; the Eu3+ ions occupied the interstitial positions in the SiO4 network structure and were not reduced even under heating in H2 gas. On the other hand, in the glasses containing Al2O3 with the Al/Na ratio exceeding unity, the Eu3+ ions commenced to be coordinated by the AlO4 units in addition to the SiO4 network structure. When heated in H2 gas, H2 gas molecules reacted with the AlO4 units surrounding Eu3+ ions to form AlO6 units terminated with OH bonds, and reduced Eu3+ ions to Eu2+ via the extracted electrons. 相似文献
74.
Chemical mimicry is an effective strategy when signal receivers recognize and discriminate models by relying on chemical cues. Some aphid enemies mimic the cuticular chemicals of aphids through various means thus avoiding detection and attack by aphid-tending ants. However, because ants have been reported to learn the chemical signatures of aphids in order to distinguish the aphids, the efficacy of chemical mimicry is predicted to depend on the experience of the ants that had tended aphids. The present study tested this hypothesis using two predator species: larvae of the green lacewing Mallada desjardinsi, and larvae of the ladybeetle Scymnus posticalis. Lacewing larvae carry the carcasses of aphids on which they have preyed upon their backs, and these function via chemical camouflage to reduce the aggressiveness of aphid-tending ants toward the larvae. Ladybeetle larvae reportedly produce a covering of wax structures, and their chemicals appear to attenuate ant aggression. We examined whether the behavior of the ant Tetramorium tsushimae toward these predators changed depending on their aphid-tending experience. Ants moderated their aggressiveness toward both predators when they had previously tended aphids, indicating that chemical mimicry by both aphid predators is dependent on previous experience of the ants in tending aphids. Chemical mimicry by the predators of ant-tended aphids is therefore considered to exploit learning-dependent aphid recognition systems of ants. 相似文献
75.
Masayuki Nogami Yoichi Goto Yasushi Tsurita Toshihiro Kasuga 《Journal of the American Ceramic Society》2001,84(11):2553-2556
The effect of phosphorus ions on the proton conductivity was examined for the sol–gel-derived glasses. The porous glasses were prepared through hydrolysis of PO(OCH3 )3 and Si(OC2 H5 )4 , in which the phosphorus ions consisted of the POH bonds and were dissolved into the silica matrix without any P-O-Si bond. The electrical conductivity increased in a humid atmosphere and reached ∼30 mS/cm at 50°C under 70% RH. High conductivity is achieved by both the POH bonds and the molecular water bonded to the POH bonds. The conductivity increased with a change in humidity from 40% to 80% RH. The phosphorus ions were selectively dissolved in water, resulting in a lower conductivity. 相似文献
76.
Hyperbranched polyamidoamine–grafted silica was prepared according to dendrimer synthesis methodology. The modified silica was dispersed uniformly in epoxy resin, and the curing of epoxy resin proceeded successfully by heating in the presence of the modified silica; the gel fraction of the epoxy resin cured by the hyperbranched polyamidoamine–grafted silica (grafting = 80.2%) reached 77% at 170°C after 48 h. The gel fraction increased with increasing terminal amino group content of the hyperbranched polyamidoamine–grafted silica. In addition, the curing ability of the silica increased by complexation of the terminal amino groups of the grafted polyamidoamine with boron trifluoride. The modulus of elasticity of the curing materials obtained using the modified silica as a curing agent was lower than that using conventional a curing agent such as ethylenediamine in the presence of untreated silica. On the other hand, the heat resistance of the curing product using the modified silica was superior to that using ethylenediamine, but no difference in glass‐transition temperature was observed. It is expected that hyperbranched polyamidoamine grafted‐silica is incorporated uniformly with chemical bonds in the matrix of the epoxy resin. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 573–579, 2001 相似文献
77.
Masayuki Yamaguchi 《应用聚合物科学杂志》2001,82(5):1277-1283
Flow instability in a capillary extrusion is studied for a high molecular weight, plasticized poly(vinyl chloride) (PVC). The onset of melt fracture correlates with the long time relaxation ascribed to the generation and/or growth of PVC crystallites. An increase in the residence time in the cylinder leads to this long time relaxation and results in the melt fracture, although the apparent shear stress remains constant, irrespective of the residence time. The extrudate temperature and the species of the plasticizer also have a significant influence on the apparatus of the extruded products. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1277–1283, 2001 相似文献
78.
Kimihiro Yamashita Motohide Matsuda Yasushi Inda Takao Umegaki Masayuki Ito Toshinori Okura 《Journal of the American Ceramic Society》1997,80(7):1907-1909
Dielectric depression and dispersion were observed in BaTiO3 ceramic films fabricated by electrophoretic deposition followed by sintering. The dielectric constants were depressed down to 6800–4600 around the Curie point ( T C ). The dielectric dispersion occurred above T C . These dielectric properties are attributable to a surface layer formed during sintering. XRD analysis indicated that the surface layer was a hexagonal-like BaTiO3 phase. A mixed solvent of acetylacetone and alcohol employed in the present work may have been responsible for the formation of the surface layer. 相似文献
79.
80.
纤维复合材料已经研究了数十年了。他们有着比传统材料,如钢材,优秀的多的力学性能。然而,由于相对较低的产量,梭织、编织与其3D纤维结构的复合材料被认为较难大量生产。因此,近年来,针织物在复合材料界获得了较高的关注,它的高度可塑性使针织复合材料可以直接生产制造成各种复杂形状的复合材料如管状、圆锥型等,使得材料的浪费可以降到了最低。本文使用了有表面处理和没有表面处理的纬编平针碳纤维制成复合材料。对两种复合材料的经向和纬向分别做了拉伸试验。结果显示:有表面处理的材料具有更好的拉伸性能,尤其是在wale方向上,有表面处理的复合材料比没有表面处理的复合材料的拉伸强度提高75.68%。 相似文献