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排序方式: 共有1007条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(40):17737-17748
Due to problems such as pores on surface-treated coatings, the corrosion resistance of pure titanium bipolar plates for proton-exchange membrane fuel cells can be further improved by increasing the corrosion resistance of pure titanium by using differential speed-rolling (DSR); however, these materials have not yet reached the standard requirements of bipolar plates (corrosion current density icorr<103 nA·cm?2). In this work, the corrosion resistance of pure titanium was improved by optimizing the DSR process while the strength was maintained. The best corrosion resistance of the DSR pure titanium was achieved when the roller speed ratio was 2, while icorr was 429 nA·cm?2 in a solution of 0.5 M H2SO4 and 2 mg/L HF at room temperature. The formability of the DSR pure titanium for bipolar plates was verified. The optimal holding pressure range was 6.8–7.0 kN. 相似文献
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Molecular dynamics simulations are used to investigate polymer networks made by either end-linking or randomly crosslinking a melt of linear precursor chains. The resulting network structures are very different, since end-linking leads to nearly ideal monodisperse networks, while random crosslinking leads to polydisperse networks, characterized by an exponential strand length distribution. Networks with average strand length 20 and 100 were generated. These networks were used to study the effects of disorder in the network connectivity on observables averaged either over the entire network or selected sub-structures. Heterogeneities in the randomly crosslinked networks cause significant differences in the localization of monomers, however, neither the localization of crosslinks nor the microscopic strain response are significantly affected. Compared to end-linked networks, randomly crosslinked networks have a slightly increased tube diameter, and as a result a slightly decreased shear modulus, but otherwise identical stress-strain behavior. For the investigated systems, we conclude that the microscopic strain response, tube diameter, and stress-strain relation are all insensitive to the heterogeneities due to the linking process by which the network were made. 相似文献
4.
Natural rubber (NR) can be degraded depending on various factors such as heat, mechanical force, chemical reaction, and light.
Light is a very interesting factor because it can cause the NR to degrade under low temperature and pressure. The photo-degradation
of NR films was carried out to investigate the effects of the light and the temperature on the reduction of the weight-average
molecular weight (Mw) and the double bonds in the NR films. The NR films, with and without catalysts, titanium dioxide (TiO2), and potassium persulfate (K2S2O8), were exposed to light from a mercury light bulb at 7,000 and 36,000 lux, and at the temperature of 25 °C and 80 °C for
192 hrs. After exposure, the Mw of the NR films was analyzed by gel permeation chromatography (GPC). Changes in the Mw were
used to construct a kinetic model for the process, (1/Mw)=(1/Mw0)+(kt/2M0) where k is the rate constant, and M0 is the Mw of the monomer unit. The linear relationship between 1/Mw and time suggested pseudo first-order processes with
random scission. The Mw distribution information from the GPC was used to calculate the number of double bonds in the NR films.
The trend of the double bonds reduction curves was quite similar to the result obtained from the calculation from the FTIR
spectra. This indicated that this calculation method might possibly be another alternative way to obtain the number of double
bonds in the NR. 相似文献
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Seung-Hwan Kim Seung-Bok Choi Sung-Ryong Hong M.-S.Moon-Sik Han 《International Journal of Mechanical Sciences》2004,46(1):269-157
This paper presents vibration control of a flexible beam structure using a hybrid mount which consists of elastic rubber and piezoelectric stack actuator. After identifying stiffness and damping properties of the rubber and piezoelectric elements, a mechanical model of the hybrid mount is established. The mount model is then incorporated with the beam structure, and the governing equation of motion is obtained in a state space. A sliding mode controller is designed in order to actively attenuate the vibration of the beam structure subjected to high-frequency and small magnitude excitations. The controller is experimentally realized and measured control responses such as acceleration of the beam structure and force transmission through the hybrid mount are evaluated and presented in both frequency and time domains. 相似文献
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新型多效能复合式橡胶防老剂FNPPD的制备 总被引:1,自引:0,他引:1
介绍了一种新型多效复合式橡胶防老剂FNPPD及其制备。其中包括该剂主要成分668防老剂(N-苯基N′-另辛基对苯二胺)的加氢法合成;合成668的原料之一2-辛酮的制备方法,以及668与酮胺类化合物复合为FNPPD防老剂的工艺过程。生产FNPPD具有可观的经济效益和市场前景。 相似文献
10.
The equivalent inclusion method (EIM) assuming linear elasticity is used to calculate the mechanical interactions between spherical rubber particles in an amorphous matrix, as in a rubber toughened polymer. The influences of the various calculation parameters are examined and it is shown that the method can provide reliable results with regard to the level of hydrostatic stress in the particles. Damage of the material is simulated by replacing the most stressed particles by voids. Numerical simulations for several hundreds of interacting particles give information on the kinetics and spatial organisation of the damage. It appears that, as the volume fraction of particles increases from 10 to 20%, the spatial configuration of the damage evolves from a localised to a diffuse mode. These results are discussed in relation to the efficiency of rubber toughening. 相似文献