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131.
A film of poly(l-lactic acid) (PLLA) consisting of highly oriented α crystals was uniaxially drawn by tensile force. The effects of the draw ratio (DR), draw temperature (Td), and draw stress on the crystal/crystal transformation from the α- to the β-form crystals were studied. At the initial stage of drawing, the highly oriented α crystals of the starting film transformed into a broader orientation distribution, and significant crystal disorder was introduced. Upon further drawing, the α crystals steadily transformed into β crystals with increasing the DR. For the drawing at a constant Td, the crystal transformation proceeded more efficiently at a higher draw rate and, hence, at a higher draw stress. Furthermore, for the drawing at a constant draw rate, the transformation proceeded with DR most efficiently for the tensile draw at a Td around 140 °C, although the draw stress increased with decreasing the Td. The present result combined with the previous finding in the drawing of PLLA by solid-state extrusion [Macromolecules 36 (2003) 3601] suggests that there is a Td of around 140 °C at which the crystal transformation proceeds most efficiently with DR, suggesting that there are two factors that have opposite effects on the efficiency of the crystal transformation with increasing the Td. However, as a result of the combined effects of the Td and DR on the crystal transformation and the ductility increase with the Td, an oriented film consisting predominantly of β crystals was obtained by tensile drawing at a Td in the range of 140-170 °C to the highest DR achieved at each Td. 相似文献
132.
A study on capacity fading of lithium-ion battery with manganese spinel positive electrode during cycling 总被引:3,自引:0,他引:3
The capacity fading mechanism of lithium-ion cell was studied by disassembling the charge-discharged cells and analyzing their electrodes using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), etc. Cu ion dissolved from current collector of anode and Mn ion dissolved from LiMn2O4 spinel (cathode) were all existing in solid electrolyte interface (SEI) layer on carbon anode as Cu2O and MnO or MnO2, respectively. These depositions of Cu and Mn oxides did not uniformly deposited on the anode side, and most of them were detected on the carbon surface nearby to the separator side. The SEI layer is hard and about 0.3 μm in thickness. Furthermore, the cycling performance of the cells can be improved by adding 1,2,3-benzotrazole (a corrosion inhibitor of Cu) before assembling the cell, it then coordinates strongly with Cu ions into the electrolyte. From the results, it is obvious that the existing of Cu oxide as well as Mn oxide in the SEI layer, which blocks the normal intercalation of the lithium ions, is one of the factors for the capacity fading of the cells. 相似文献
133.
Viscoelastic properties of poly(isoprene-b-styrene) in dioctylphthalate under steady shear flow were measured near the order—disorder transition temperature. In ordered states, first normal stress difference N1 is proportional to shear rate
at low
region, but becomes proportional to
at the high
region, similar to the N1 behaviour of polymer blends undergoing shear-induced homogenization. Because the existence of microdomains was confirmed at the high
region by the flow birefringence method, it is concluded that the above N1 behaviour is not caused by shear-induced homogenization, but is probably caused by the shear-induced alignment of the microdomain structure. 相似文献
134.
Yoshiyuki Sakamoto Tomoyoshi Motohiro Shinichi Matsunaga Kohei Okumura Tomoyuki Kayama Kiyoshi Yamazaki Toshiyuki Tanaka Yoshimi Kizaki Naoki Takahashi Hirofumi Shinjoh 《Catalysis Today》2007,121(3-4):217-225
The release and reduction of NOx in a NOx storage-reduction (NSR) catalyst were studied with a transient reaction analysis in the millisecond range, which was made possible by the combination of pulsed injection of gases and time resolved time-of-flight mass spectrometry. After an O2 pulse and a subsequent NO pulse were injected into a pellet of the Pt/Ba/Al2O3 catalyst, the time profiles of several gas products, NO, N2, NH3 and H2O, were obtained as a result of the release and reduction of NOx caused by H2 injection. Comparing the time profiles in another analysis, which were obtained using a model catalyst consisting of a flat 5 nmPt/Ba(NO3)2/cordierite plate, the release and reduction of NOx on Pt/Ba/Al2O3 catalyst that stored NOx took the following two steps; in the first step NO molecules were released from Ba and in the second step the released NO was reduced into N2 by H2 pulse injection. When this H2 pulse was injected in a large amount, NO was reduced to NH3 instead of N2.
A only small amount of H2O was detected because of the strong affinity for alumina support. We can analyze the NOx regeneration process to separate two steps of the NOx release and reduction by a detailed analysis of the time profiles using a two-step reaction model. From the result of the analysis, it is found that the rate constant for NOx release increased as temperature increase. 相似文献
135.
The influence of age and cholesterol on polyunsaturated fatty acids (PUFa) levels was studied in young and old male Sprague-Dawley
rats. Animals were fed a fat-free diet supplemented with 10% (by wt) safflower oil with or without 1% cholesterol for 8 wk.
As a result of cholesterol feeding, proportions of linoleic acid (18∶2n−6) and dihomo-γ-linolenic acid (30∶3n−6) were increased
and and that of arachidonic acid (20∶4n−6) was decreased in the liver and platelet phospholipids in 64-wk-old rats, suggesting
inhibitory effects of cholesterol on 20∶4n−6 synthesis from 18∶2n−6. The prominent age-dependent effect on the levels of PUFA
was a retention of C−22 n−3 PUFA, accompanied by decreased C−22 n−6 PUFA and increased 20∶3n−6 in the liver and platelet phospholipids.
Ratio of 20∶3n−6/20∶4n−6 increased in 64-wk-old rats regardless of dietary cholesterol, suggesting depressed Δ5-desaturase
with age. In aorta phospholipids, 20∶3n−6 content and 20∶3n−6/20∶4n−6 ratio increased with cholesterol supplementation, but
not with age. These results suggest that changes of PUFA composition of platelet phospholipids with age are closely linked
with changes in liver phospholipids. The 20∶4n−6 content in both platelet and aorta phospholipids is kept constant, despite
other n−6 and n−3 PUFA being affected by age. 相似文献
136.
The selective detection of acetylene in gases extracted from isolation oils has been studied to develop an electrochemical
sensor for the diagnostic monitoring of the condition of in-service electrical instruments. Effects of coexisting gases (CH4, C2H6, C2H4, H2 and CO) on the oxidation current of C2H2 were tested using gas-permeable gold-coated and platinum-black electrodes as the sensor. The gold-coated electrode showed
good behaviour for the selective current detection of acetylene under potentiostatic conditions (−0.1 V/Pt-black reference
electrode) in 10m H2SO4 electrolyte solution. 相似文献
137.
Nitroalkyl acrylates and methacrylates involving some new compounds were prepared. The homopolymerization of these monomers in toluene and their copolymerization with styrene in acetone were carried out with azobisisobutyronitrile as initiator. The rate of polymerization of the nitroalkyl acrylates showed a correlation with the number of nitro groups situated on the ester side chain. The apparent activation energies of the polymerization were found to be 22.0–27.5 kcal./mole for the nitroalkyl acrylates and about 11.5–13.0 kcal./mole for the nitroalkyl methacrylates. From the reactivity ratios and Q-e values of the copolymerization the following information was obtained. The copolymerization behavior of nitroalkyl acrylates and methacrylates showed an alternating tendency, and these monomers belong to the conjugative monomer groups. On the reactivities of these monomers, the polarity of vinyl group was affected a little by nitro group of ester bond side, and the resonance affected little. These monomers were crosslinked with 2-methyl-2-nitro-1,3-propylene diacrylate. Some of the polymers showed marked improvement in the physical properties of elastomers. 相似文献
138.
Keiichi Tomishige Shogo Kanazawa Motoki Sato Kenji Ikushima Kimio Kunimori 《Catalysis Letters》2002,84(1-2):69-74
Pt(0.3)/Ni(10)/Al2O3, prepared by a sequential impregnation method, exhibited a more excellent performance in methane reforming with CO2 and O2 in terms of the catalytic activity and the temperature profile of the catalyst bed than Pt(0.3) + Ni(10)/Al2O3 prepared by a coimpregnation method, Ni(10)/Al2O3, Pt(0.3)/Al2O3, and Pt(10)/Al2O3. It is thought that this is because the surface Pt atoms on Ni catalyst can contribute to the enhancement of the catalyst reducibility. 相似文献
139.
Texture of primary recrystallization on nonoriented electrical steel sheet with phase transformation
T. Kumano T. Kubota N. Takahashi 《Journal of Materials Engineering and Performance》1995,4(4):401-412
The magnetic properties of nonoriented (NO) electrical steel sheet are commonly improved if the texture of their products
possesses “cube texture” (e.g., {100 〈0vw〉, “goss texture”) (i.e., 110〈011〉, and less 222 texture). Industrially “cube type”
has not been obtained, but “goss texture” has been. In a greater or lesser degree, {222} texture exists. To improve “goss
texture” and reduce 222 texture, the grain size of the material prior to cold rolling should be larger. When the grain size
before cold rolling is larger, during primary recrystallization, “goss texture” is enriched, 222 texture is decreased, and
the grain grows so easily that higher induction and lower core loss can be obtained. This does not depend on the presence
of phase transformation. In case of NO steel with phase transformation, heat treatment before cold rolling has been done below
the austenite transition temperature (Acin1) in order to prevent the fine grain size caused by α → γ(+α) → α transformation.
By using material that was heated over Acin1 and cooled with changing cooling rates, this study describes (a) the relationship
between textures before cold rolling and the texture of the final product, and (b) the development of the magnetic properties. 相似文献
140.
The extended X-ray absorption fine structure (EXAFS) method and transmission electron microscopy (TEM) have been used for characterizing the local structure and morphology of ferric oxyhydroxides, α-FeOOH and γ-FeOOH, with and without chromium. These ferric oxyhydroxide powders were prepared from aqueous solutions containing iron and chromium ions. Radial structural functions for iron obtained by Fe K edge EXAFS spectra showed that the linkage of structural units formed by FeO6 octahedra in γ-FeOOH is distorted by chromium addition, while such distortion in α-FeOOH is not clearly detected. On the other hand, Cr K edge EXAFS spectra showed that the local structure around chromium does not necessarily correspond to the local structure around of iron, which is observed by Fe K edge EXAFS spectra. This suggests that the structural units containing iron and chromium are heterogeneously distributed in these ferric oxyhydroxides. The local structural information was discussed coupled with morphological features of these ferric oxyhydroxides observed by TEM. 相似文献