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141.
Nuclear magnetic resonance (NMR) relaxation methods have been used to investigate the internal structure of porous silica gelled from colloidal silica and potassium silicate mixtures. These materials possess a narrow pore size distribution with average pore diameter ranging from 470 to 2400 Å (47 to 240 nm) as determined from mercury intrusion porosimetry. NMR relaxation measurements were performed on deionized water impregnated into the pore space. These results determine the distribution of local surface-to-volume ratios and show that all of the silica samples are very uniform on a length scale greater than 5 μ. NMR relaxation measurements performed on silica samples partially filled with water provide a precise confirmation of the theoretical model upon which the NMR pore structure analysis is based. Measurements of the relaxation strength at the water—silica interface were found to depend systematically on the initial composition of the material. The self-diffusion coefficient of water, saturated in the pore space, is reduced by 14% from its bulk value.  相似文献   
142.
This article is concerned with the static and dynamic mechanical properties of high‐density polyethylene (HDPE) reinforced with sawdust (SD) at a strain rate of up to 103 s?1. In this study, the static and dynamic properties of HDPE/SD composites with different filler loadings of 5, 10, 15, 20, and 30 wt% SD were deliberated at different levels of strain rates (0.001, 0.01, 0.1, 650, 900, and 1100 s?1) using a conventional universal testing machine and the split Hopkinson pressure bar apparatus. The results showed that the stress–strain curves, yield behavior, stiffness, and strength properties of the HDPE/SD composites were strongly affected by both the strain rate and the filler loadings. Furthermore, the rate sensitivityof the HDPE/SD composites showed a great dependency on the applied strain rate, increasing as the strain rate increased. However, the thermal activation values showed a contrary trend. Meanwhile, for the postdamage analysis, the results showed that the applied strain rates influenced the deformation behavior of the tested HDPE/SD composites. Moreover, for the fractographic analysis at dynamic loading, the composites showed that all the specimens underwent a severe catastrophic deformation. J. VINYL ADDIT. TECHNOL., 24:162–173, 2018. © 2016 Society of Plastics Engineers  相似文献   
143.
Bamboo is a fast‐growing, readily available natural material with tensile specific strength equivalent to that of steel (250–625 MPa/g/cm3). In the pursuit of sustainable construction materials, a composite was made with potassium polysialate siloxo geopolymer as the matrix and randomly oriented chopped bamboo fibers (Guadua angustifolia) from the Amazon region as the reinforcement. Four‐point flexural strength testing of the geopolymer composite reinforced with bamboo fibers was carried out according to ASTM standard C78/C78M‐10e1. Potassium‐based metakaolin geopolymer reinforced with 5 wt% (8 vol%) untreated bamboo fibers yielded 7.5 MPa four‐point flexural strength. Scanning electron microscopy and optical microscopy were used to investigate the microstructure. In addition, X‐ray diffraction was used to confirm the formation of geopolymer.  相似文献   
144.
Separation of the radioisotope 85Kr from 136Xe is an important target during used nuclear fuel recycling. We report a detailed study on the Kr and Xe adsorption, diffusion, and membrane permeation properties of the silicoaluminophosphate zeolite SAPO‐34. Adsorption and diffusion measurements on SAPO‐34 crystals indicate their potential for use in Kr‐Xe separation membranes, but also highlight competing effects of adsorption and diffusion selectivity. SAPO‐34 membranes are synthesized on α?alumina disk and tubular substrates via steam assisted conversion seeding and hydrothermal growth, and are characterized in detail. Membrane transport measurements reveal that SAPO‐34 membranes can separate Kr from Xe by molecular sieving, with Kr permeabilities around 50 Barrer and mixture selectivity of 25–30 for Kr at ambient or slight sub‐ambient conditions. The membrane transport characteristics are modeled by the Maxwell‐Stefan equations, whose predictions are in very good agreement with experiment and confirm the minimal competing effects of adsorption and diffusion. © 2016 American Institute of Chemical Engineers AIChE J, 63: 761–769, 2017  相似文献   
145.
In an open waterway flow passage, the inclusion of flow distributor paves a way to understand the idea of flow uniformity of the water along the upstream side and prevents non-uniform flow of water besides the passage length as a function of flow rate. The interesting idea in the flow distributor is its length and porosity. The essential conditions that should be satisfied are: there should not be any turbulence and there should be a possibility of achieving uniform circumferential flow in the flow passage. The other critical issue is the accurate measurement of low velocity of water. In this paper, a propeller-turbine-type anemometer is specially designed, fabricated and calibrated to measure the local velocity of water in the range of 0.001–0.01 m/s. This paper signifies how the flow uniformity is achieved by varying the size and porosity of the flow distributor.  相似文献   
146.
The impact of manufactured nanomaterials on human health and the environment is a major concern for commercial use of nanotechnology based products. A judicious choice of selective usage, lower nanomaterial concentration and use in combination with conventional therapeutic materials may provide the best solution. For example, silver nanoparticles (Ag NPs) are known to be bactericidal and also cytotoxic to mammalian cells. Herein, we investigate the molecular mechanism of Ag NP mediated cytotoxicity in both cancer and non-cancer cells and find that optimum particle concentration leads to programmed cell death in vitro. Also, the benefit of the cytotoxic effects of Ag NPs was tested for therapeutic use in conjunction with conventional gene therapy. The synergistic effect of Ag NPs on the uracil phosphoribosyltransferase expression system sensitized the cells more towards treatment with the drug 5-fluorouracil. Induction of the apoptotic pathway makes Ag NPs a representative of a new chemosensitization strategy for future application in gene therapy.  相似文献   
147.
148.
2D ternary semiconductor single crystals, an emerging class of new materials, have attracted significant interest recently owing to their great potential for academic interest and practical application. In addition to other types of metal dichalcogenides, 2D tin dichalcogenides are also important layered compounds with similar capabilities. Yet, multi‐elemental single crystals enable to assist multiple degrees of freedom for dominant physical properties via ratio alteration. This study reports the growth of single crystals Se‐doped SnS2 or SnSSe alloys, and demonstrates their capability for the fabrication of phototransistors with high performance. Based on exfoliation from bulk high quality single crystals, this study establishes the characteristics of few‐layered SnSSe in structural, optical, and electrical properties. Moreover, few‐layered SnSSe phototransistors are fabricated on both rigid (SiO2/Si) and versatile polyethylene terephthalate substrates and their optoelectronic properties are examined. SnSSe as a phototransistor is demonstrated to exhibit a high photoresponsivity of about 6000 A W?1 with ultra‐high photogain ≈8.8 × 105, fast response time ≈9 ms, and specific detectivity (D*) ≈8.2 × 1012 J. These unique features are much higher than those of recently published phototransistors configured with other few‐layered 2D single crystals, making ultrathin SnSSe a highly qualified candidate for next‐generation optoelectronic applications.  相似文献   
149.
A comparative performance analysis in terms of delay, power dissipation, power delay product (PDP), and crosstalk noise between SWCNT bundle interconnects with resistance estimated using conventionally (temperature independent model), and thermally aware model is investigated. The results are also compared with those of currently used copper interconnects at 22 nm technology node. It is observed that, with rise in temperature from 300 to 500 K, SWCNT bundles have a lower delay than that of copper interconnect at different lengths from 100 to \(1000\,\upmu \hbox {m}\) whereas reverse is true for power dissipation. The SPICE simulation results further reveal that for temperature variations ranging from 300 to 500 K, compared to conventional metal (copper) conductors, crosstalk noise voltage levels (positive peaks) in capacitively coupled SWCNT bundle, at the far end of victim line, are significantly low. Moreover, a relative average improvement in delay, power, and PDP using a thermally aware model in comparison with a temperature independent model is about 22.44, 7.59 and 31.96 %, respectively, with length variations from 100 to \(1000\,\upmu \hbox {m}\), whereas for varied tube diameter is about 16.6, 5.6 and 19.72 %, respectively. The average relative improvement in the time duration reduction of victim output, for varied tube diameters, is about 21.7 % by using a thermally-aware model instead of a temperature-independent model of an SWCNT bundle resistance.  相似文献   
150.
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