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排序方式: 共有841条查询结果,搜索用时 281 毫秒
761.
An extensive experimental study of the structure and properties developed in as-spun nylon 6 filaments is reported. Five polymers representing different molecular weights in the range 25,000–73,000 g/mol (viscosity average) were studied. These polymers were melt spun over a range of spinning speeds using an air drag type of drawdown device. Maximum take-up velocities achieved were in the neighborhood of 4000 m/min. The structure and properties of the as-spun filaments were characterized using density, DSC, WAXS, SAXS, birefringence, and tensile tests. The structural characteristics and properties of the filaments are strongly dependent on molecular weight. Generally, higher molecular weight leads to higher modulus and filament tenacity and lower elongation to break in the as-spun filaments. The structural changes with molecular weight are rather complicated; the complications are explained in terms of changes of crystallization rate and attainable crystallinity. 相似文献
762.
Films prepared from emulsion polymerized poly(vinyl chloride) were subjected at 0°C to accelerated photodegradation in air using a weatherometer. Photooxidation and scission of the main chain took place but dehydrochlorination or formation of polyenes was not observed. The absorption of the carbonyl group indicating oxidation was found at 1725cm?1 in the infrared absorption spectrum. Only when tetrahydrofuran, which had been used for the preparation of films, was left in the films, an absorption was also found at 1770cm?1. Oxidation occurred at the position of the methylene carbon and the cut end of the main chain. As a result of the X-ray photoelectronic spectrum (ESCA) analysis, it was found that the carbonyl concentration was higher in the surface layer of the sample than in the interior thereof. 相似文献
763.
Noriyuki Kuramoto Yoshimi Takahashi Katsutoshi Nagai Kiyohito Koyama 《Reactive and Functional Polymers》1996,30(1-3):367-373
Poly(o-anisidine) (PANs) and PANs-coated silica particles were prepared by oxidative polymerization of o-anisidine using ammonium persulphate in the absence and presence of silica particles, respectively. The entire surface of the silica particles was completely covered with PANs polymerized using low concentration of o-anisidine. The effects on the electrorheological behavior of surface modification of the silica particles coated with PANs were studied under oscillatory shear. Electrorheological properties of PANs and PANs-coated silica particle suspensions were found to exhibit higher performance in nonaqueous solutions than those of silica particle suspensions even at high temperatures. 相似文献
764.
Reverse osmosis separation for many kinds of polar organic solutes (alcohols, phenols, monocarboxylic acids, amines, and ketones) was examined by an anionic charged composite membrane. The solute permeation was carried out in single-solute aqueous solution (200 mg/L) under applied pressure of 7.88 MPa at 25°C. The correlation between the solute rejection and polar parameters for these organic solutes have been investigated. For n-alkyl alcohols, monocarboxylic acids, and ketones, the solute rejection increases with molecular weight and/or molecular branching. For undissociable polar organic solutes such as alcohols and ketones, solute rejections are closely related with the Taft's number. For dissociable polar organic solutes, solute rejections depend greatly upon the dissociation constant and the degree of dissociation of solute. This membrane showed higher rejection (80%) for phenol in an undissociated state at a 98% rejection level of NaCl. Also, rejections of phenolic derivatives depend upon the pH value of the feed solution and the polar effect of substituted groups. For acetic acid and methylamine, the solute rejection increases proportionally to the degree of dissociation of solute. From these facts, the main factors in reverse-osmosis separation by an anionic composite membrane are discussed. 相似文献
765.
Naomi TakadaToshiki Koyama Masahiro Suzuki Mutsumi KimuraKenji Hanabusa Hirofusa ShiraiSeizo Miyata 《Polymer》2002,43(7):2031-2037
New ion-conducting polymer composite films have been prepared, and their ionic conducting properties have been investigated. The polymer composite films are fabricated from partially phosphorylated poly(vinyl alcohol) with tetramethylammonium salt (P-PVA·Me4N+) and poly(acrylic acid) (PAA) or poly(ethylene glycol) (PEG). For P-PVA·Me4N+/PEG composite films, the ionic conductivity and carrier density sharply increased, and carrier mobility sharply decreased around [PEG]/[PO3]P-PVA of 2. The ionic conductivity is dominated by both carrier density and carrier mobility at [PEG]/[PO3]P-PVA<2 and only by carrier density at [PEG]/[PO3]P-PVA>2. This is attributed to the fact that the ionic conduction in P-PVA·Me4N+/PEG composite films occurred through the PEG-Me4N+ complex which was independent of the carrier mobility. On the other hand, the ionic conductivity in P-PVA·Me4N+/PAA composite films showed a bell-shaped dependence on the PAA contents with a maximum value at [CO2H]PAA/[OH]P-PVA=1. FTIR spectrum measurements demonstrated that part of the carboxylic acid residues was dissociated in the composite films. This fact implied that the ionic conduction was mediated by PAA at the low PAA content. At high PAA content, however, an excess of the carboxylic acid residues formed trapping sites for the Me4N+ ion, leading to a decrease in the ionic conductivity. Furthermore, we proposed a unique mechanism of the ionic conduction. 相似文献
766.
Hiroshi Koyama Masayuki Fujimoto Tomoya Ohno Hisao Suzuki Junzo Tanaka 《Journal of the American Ceramic Society》2006,89(11):3536-3540
We investigated the structural and optical properties of microporous titanium oxide (TiO2 ) fabricated by the sol–gel method using templates of colloidal crystals with polystyrene spheres when the annealing temperature was changed between 600° and 1000°C. From X-ray diffraction patterns and SEM images, the rutile TiO2 annealed at a high temperature did not form periodic porous bodies, while the anatase TiO2 annealed at lower than 800°C formed periodic porous bodies. The porous TiO2 obtained acts as an air-sphere/TiO2 photonic crystal with an FCC structure. It is suggested that TiO2 sol annealed at a lower temperature do not lead to phase transition from the anatase phase to the rutile phase to obtain the air-sphere/TiO2 photonic crystal by the sol–gel method using templates of colloidal crystals. 相似文献
767.
Yutaka Abe Eiji Matsuo Takahiro Arai Hideki Nariai Keiko Chitose Kazuya Koyama Kazuhiro Itoh 《Nuclear Engineering and Design》2006,236(14-16):1668-1681
A safe design for a fast breeder reactor (FBR) requires post-accident heat removal (PAHR) for any potential core disruptive accident (CDA). It is important to ensure that the molten core material solidifies in the sodium coolant in the reactor vessel even if all of the core material has melted. In the present experiment, molten material was injected into water to experimentally obtain the information on the molten material jet entering the coolant and its fragmentation. Visual information was obtained with a high-speed video camera, showing that fragmentation behavior on the side of the jet was different from that on the jet front, and that the injection nozzle diameter significantly influenced the jet breakup length, while the molten jet temperature and the coolant temperature did not influence the jet breakup length. Comparison of the diameters of fragments of the solidified molten material thus obtained with fragmentation theory shows that the median fragment diameter is between the critical Weber number theory and the most-unstable wavelength of the instability theory of surface waves at a gas liquid interface.The quench behavior of the molten jet in coolant was calculated for FBR conditions by using the model that reflects actual fragmentation behavior. It was clarified that the mass of molten material in the coolant pool is related to the fragment diameter under FBR conditions. 相似文献
768.
M. Morishita K. Koyama S. Shikata M. Kusumoto 《Metallurgical and Materials Transactions B》2004,35(5):891-895
The thermodynamic properties of Mg48Zn52 were investigated by calorimetry. The standard entropy of formation at 298 K, Δf
S
298
o
, was determined from measuring the heat capacity, C
p
, from near absolute zero (2 K) to 300 K by the relaxation method. The standard enthalpy of formation at 298 K, Δf
H
298
o
, was determined by solution calorimetry in hydrochloric acid solution. The standard Gibbs energy of formation at 298 K, Δf
G
298
o
, was determined from these data. The obtained results were as follows: Δf
H
298
o
(Mg48Zn52)=(−1214±(300) kJ · mol−1;ΔfS
298
o
(Mg48Zn52)=(−123±0.36) J · K−1 · mol−1; and Δf
G
298
o
(Mg48Zn52)=(−1177±(300) kJ · mol−1. The electronic contribution to the heat capacity of Mg48Zn52 was found to be approximately equal to pure magnesium, indicating that the density of states in the vicinity of the Fermi
level follows the free electron parabolic law. 相似文献
769.
The vibrations of Gifford-McMahon (GM) and pulse-tube (PT) cryocoolers were measured and analyzed. The vibrations of the cold-stage and cold-head were measured separately to investigate their vibration mechanisms. The measurements were performed while maintaining the thermal conditions of the cryocoolers at a steady state. We found that the vibration of the cold-head for the 4 K PT cryocooler was two orders of magnitude smaller than that of the 4 K GM cryocooler. On the other hand, the vibration of the cold-stages for both cryocoolers was of the same order of magnitude. From a spectral analysis of the vibrations and a simulation, we concluded that the vibration of the cold-stage is caused by an elastic deformation of the pulse tubes (or cylinders) due to the pressure oscillation of the working gas. 相似文献
770.