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Mechanical/optical behaviors of imogolite hydrogels depending on their compositions and oriented structures
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A robust acrylamide (AAm) hydrogel reinforced by imogolite (IG), a perfect rigid nanotubular clay mineral, exhibited distinct tensile stress–strain characteristics and strain‐induced birefringence in accordance with the compositions of the gels. The gel showed a reversible anisotropic/isotropic structural transition in response to stretching/releasing before the breakdown strain. The strain‐induced birefringence of the IG‐reinforced gels could be fixed by the in situ interpenetrating polymerization of other AAm monomers that were impregnated into the gels in the stretched states. This resulted in gels with nonvolatile anisotropic birefringence, and therefore, the fixed anisotropic IG ordering showed specific stress–strain characteristics depending on the orientation of IG. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41691. 相似文献
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ABSTRACT: We report uniform and low-defect synthesis of bilayer graphene on evaporated polycrystalline nickel films. We use atmospheric pressure chemical vapor deposition with ultra-fast substrate cooling after exposure to methane at 1000C. The optimized process parameters i.e. growth-time, annealing profile and flow rates of various gases are reported. By using Raman spectroscopy mapping, the ratio of 2D to G peak intensities (I2D/IG) is in the 0.9-1.6 range over 96 percent of 200umx200um area. Moreover, the average ratio of D to G peak intensities (ID/IG) is about 0.1. 相似文献
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In studies conducted in the early 1980s, it was suggested that the use of room-type air cleaners were relatively ineffective in reducing the hazards associated with the presence of radon decay products in indoor air. Some studies suggested that air cleaning could actually increase the dose delivered by the decay products by shifting the activity-weighted particle size distribution to smaller sizes to the point where dose increase even though exposure decreased. A recently developed automated, semicontinuous instrument now permits the direct measurement of activity-weighted size distributions in occupied homes so that the exposure to those occupants can be directly determined and the effect of the air cleaners on dose be estimated. Three different types of air cleaners were tested in this study; an electrostatic air cleaner (EAC), an ion generator / fan system (IG / F), and a filtration unit that was operated at two different fan speeds (LO-FIL and HI-FIL). The three units reduced the median exposure to radon progeny by 63% for the EAC, 34% for the IG / F unit, 66% for the filtration system at both low and high flow rates. Based on a model for lung dosimetry, the median reductions is estimated dose to the secretory cells of the bronchial epithelium are 50% for the EAC, 28% for the IG / F unit, and 68% for the filtration system at both fan speeds. In these studies, the performance of the EAC and filtration systems produce rather similar activity weighted size distributions while the lower dose reduction for the IG / F system is due to a small peak in activity in the size range of 1.5–5 nm. The source of this peak is not known, and requires further study to determine if the system is generating particles in this size range 相似文献
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钛合金牙根种植体表面烧结复合涂层的研究 总被引:5,自引:1,他引:5
采用两步法烧结法制备了新型的钛合金牙根植体表面复合涂层。通过涂层配方设计,使底釉和表面涂层膨胀系数基本与牙根基体材料钛合金匹配。生理盐水浸泡实验表明,底釉有良好的化学稳定性,表面涂层有良好的生物活性。 相似文献
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《Ceramics International》2022,48(1):463-471
The high reliability and extended life of seawater hydraulic components is dependent on the tribological properties of key friction pairs, more and more attention has been given to the performance degradation and lifetime of the friction pairs. In this paper, the wear process of Tungsten carbide (WC) with 6%wt of Ni (WC–6Ni)/SiC friction pair is studied through the tribological test under seawater lubrication. Considering the random effects and the complex wear mechanism of WC-6Ni/SiC, an efficient Inverse Gaussian (IG) process supported lifetime prediction model is established by coupling the multiple stresses under seawater lubrication, and the parameters in the proposed IG process model are derived. Two actual cases are used to validate the proposed method. The prediction model and experimental results show the high accuracy in time-varying lifetime prediction of WC-6Ni/SiC, which is of great significance to the evaluation of friction pair and the maintenance for seawater hydraulic components. 相似文献
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There is renewed interest in the domestication of Irvingia tree species due to the potential use of various parts of the tree as raw materials for a wide range of applications such as biodiesel production, cosmetics, perfumes, soap, weight-loss supplement etc. The current study investigates the properties of extracts from the seed kernels of two Irvingia species – Irvingia gabonensis (IG) and Irvingia wombolu (IW) as natural wood adhesives. Three extraction methods using various solvent/solute media were compared in terms of yield, composition and mechanical properties. Statistically, the analysis revealed significant differences between the different extraction methods. The adhesion properties of the extracts were tested on wood veneers according to the American Society for Testing and Materials standard (ASTM D – 906-64). The shear strength of the extracts ranged from 0.55 to 1.5 MPa and 0.86–1.7 MPa for IG and IW, respectively. The initial decomposition temperature of all Irvingia Kernel extract ranges from 138.3 to 149.11 °C for IG and 129.5–145.3 °C for IW. As a result, the hot melt temperature for the adhesive experiments was set around 150 °C. The results indicate that Irvingia kernel extract is a more promising source of non-formaldehyde based adhesives in wood composite production. 相似文献
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Many insect species sequester compounds acquired from their host plants for defense against natural enemies. The distribution of these compounds is likely to affect both their efficacy as defenses, and their costs. In this study we examined the distribution of sequestered iridoid glycosides (IGs) in two congeneric species of nymphalid butterfly, Euphydryas anicia and E. phaeton, and found that the pattern of localization of IGs differed between the two species. Although IG concentrations were quite high in the heads of both species, the relative concentrations in wings and abdomens differed substantially. Euphydryas anicia had relatively high IG concentrations in their abdomens and low IG concentrations in their wings, whereas the reverse was true in E. phaeton. We interpret these results in light of two current hypotheses regarding where sequestered chemicals should be localized: that they should be found in wings, which would allow non-lethal sampling by predators; and that their distribution is constrained by the distribution of tissue types to which sequestered compounds bind. We also offer the third hypothesis, that costs of storage may differ among body parts, and that the localization of compounds may reflect a cost-reduction strategy. Results from E. phaeton were consistent with all three of these non-mutually exclusive hypotheses, whereas results from E. anicia were only consistent with the notion that tissue bias among body parts plays a role in IG distribution. The finding that these two congeneric butterflies exhibit different patterns of IG localization suggests that they have been shaped by different selection regimes. 相似文献