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41.
Shinnosuke Miyauchi Yasuo Hattori Toshiyuki Takamatsu Yoshio Sorimachi 《应用聚合物科学杂志》1992,44(3):377-381
A method to generate a porous region near the surface of a polymer is suggested. In this method the region near the surface is swollen by immersing the polymer for a short time in a solvent. Subsequently, the polymer is introduced in a nonsolvent (for the polymer) that is, however, miscible with the solvent. The formation of the porous region is a result of (1) the swelling accompanied by the disentanglement of the surface molecular chains, and the dissolution of some of them during the immersion in the solvent, and (2) the rapid extraction of the solvent from the swollen region by the nonsolvent. The porous surface provides a matrix into which a second incompatible monomer can be polymerized so that the two otherwise incompatible polymers can adhere to one another. 相似文献
42.
Spectroscopic evidence for the interaction of hydroxyl groups and chromium ions was obtained using a catalyst prepared from chromyl chloride. A new OH peak, observed at 3705 cm–1 after pumping away CO gas, is attributed to the direct interaction of OH with the low-valent chromium. This peak shifts to 3590 cm–1 on contact with O2 at room temperature and it is assigned to a hydroxyl interacting with the oxidized chromium. New assignments are also proposed for IR bands of CO presorbed on the catalyst. The peak due to CO at 2188 cm–1 decreases as the OH intensity at 3705 cm–1 increases, suggesting that the former peak arises from adsorption on Cr(II) species to which two oxygen atoms are attached. 相似文献
43.
Takashi Mitamura Hiroyuki Ogino Hidehiko Kobayashi Toshiyuki Mori Hiroshi Yamamura 《Journal of the American Ceramic Society》1993,76(8):2127-2128
Preparation of BaLa2 O4 , Ba3 ,Y4 O9 , Ba ,In2 O5 , and Ba3 Ga2 O6 powders and their sintering were investigated in Ar or air. These sintered bodies with perovskite-related structure were synthesized by reaction sintering, using mixed powders in the atomic ratios of Ba/La = 1, Ba/Y = 0.75, Ba/In = 1, and Ba/Ga = 1.5. The order-disorder transition temperatures of the BaLa2 O4 , Ba3 Y4 O9 , Ba2 In2 O5 , and Ba3 Ga2 O6 sintered bodies were 270°, 350°, 880°, and 123Oo C, respectively. It was found that the temperatures were influenced by the ionic radius of cations in B sites, and the transition temperatures decreased with increasing ionic radius. 相似文献
44.
Motoi Takahashi Toshiyuki Mori Fei Ye Ajayan Vinu Hidehiko Kobayashi John Drennan 《Journal of the American Ceramic Society》2007,90(4):1291-1294
A Pt on nano-sized CeO2 particles that in turn are supported on carbon black (CB) was synthesized using the co-impregnation method. This potential anode material for fuel cell applications was synthesized in a stepwise process. The pure CeO2 was synthesized using an ammonium carbonate precipitation method, and the Pt particles dispersed on the CeO2 in such a way that a uniform dispersion with the CB was obtained (Pt–CeO2 /CB). The electrochemical activity of the methanol (CH3 OH) oxidation reaction on the Pt–CeO2 /CB was investigated using cyclic voltammetry and chronoamperometry experimentation. The onset potential of CH3 OH oxidation reaction on the Pt–CeO2 /CB anode was shifted to a lower potential as compared with that on commercially available Pt–Ru/carbon (C) alloy anode. In addition, the activation energy of the Pt–CeO2 /CB anode was much lower than that of the Pt–Ru/C alloy anode. Moreover, the current density of the Pt–CeO2 /CB anode was much higher than that of the Pt–Ru/C alloy anode at temperatures between 28° and 60°C. These results suggest that the anode performance of the Pt–CeO2 /CB anode at the operating temperature of typical fuel cells (80°C) is superior to that of the more usual Pt–Ru/C alloy anode. Importantly, the rare metal, Ru, is not required in the present anode material and the amount of Pt required is also significantly reduced. As a consequence, we report a promising candidate Pt–CeO2 /CB composite anode for application in the development of direct methanol fuel cells. 相似文献
45.
A supramolecular polymer formed by N,N′,N″-tris(3,7-dimethyloctyl)benzene-1,3,5-tricarboxamide (DO3B) in n-decane (C10) possesses large macro-dipoles naturally generated by three-fold inter-molecular hydrogen bonding aligned along its helical columnar structure connected by defective portions, which are DO3B molecules containing failure in the hydrogen bond formation, in the order of head to tail arrangement without dipole inversion like type-A polymers. 相似文献
46.
Morphology and fracture mechanisms in two nanoclay‐filled epoxy systems were investigated using both microscopy and spectroscopy tools. Clay exfoliation was achieved using a series of sample preparation steps, and confirmed using wide angle X‐ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Significant improvement in modulus was obtained when clay exfoliation was achieved. Incorporation of core‐shell rubber (CSR) in both caly‐filled epoxy systems leads to greatly enhanced fracture toughness. Optical microscopy and TEM observations of the CSR‐modified nanocomposites suggest that CSR cavitation. shear yielding of the matrix, clay layer delamination. CSR bridging, crack bifurcation. and crack deflection are among the operative toughening mechanisms observed, depending on the nature of the epoxy matrix utilized. 相似文献
47.
48.
Biomimetic Process for Producing SiC "Wood" 总被引:6,自引:0,他引:6
49.
Twelve kinds of cation-exchange membranes were treated with hydrogen peroxide. Some of them (Selemion CMV, Nepton CR-61, Scrion C-100, SAM-1) were completely destroyed. Heterogeneity is believed to be present in that part of their chemical structures that is decomposable by the treatment. The other membranes were converted into porous membranes by the decomposition of the resinous part. Water permeabilities and electric resistances of the porous membranes were examined to evaluate the pore radius. It was concluded that the “paste method” membranes have a heterogeneity or localized distribution of the resinous part under 50 mμ. The “paste method” membranes seemed to resemble the “graft method” membranes in chemical structure and to be much different from the mosaic-type membranes such as Permaplex and MC-3142. These results were also supported by extraction of the membranes with appropriate solvents and observation by electron microscopy. 相似文献
50.
A round bar specimen and a square bar specimen cut out from medium-density polyethylene pipes with a notch were made and a fatigue test was conducted to cause a brittle fracture. The initiation and growth of a craze and crack at the tip of a notch was observed. In the range where loading cycles are few and displacement of the specimen does not increase, the craze prior to crack initiation occurs. Also, the effect of frequency was investigated. The pure creep failure and the fatigue failure at low frequency were compared. The lower the frequency, the smaller the reciprocal of the actual loading time Tf becomes. It is also found that this tensile fatigue test is a useful test method to assure the quality of pipes. 相似文献