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排序方式: 共有2450条查询结果,搜索用时 15 毫秒
61.
Rekha Agrawal Jyoti Shah Govind Gupta Ritu Srivastava Chhemendra Sharma Ravinder Kotnala 《应用聚合物科学杂志》2020,137(48):49566
A facile and eco-friendly synthesis of polypyrrole from monomer pyrrole using nominal amount of ferric chloride hexahydrate (FeCl3.6H2O) oxidant in aqueous solution by chemically oxidative polymerization method has been reported. The use of aqueous solvent and ferric chloride hexahydrate salt in polypyrrole synthesis have an eco-friendly route favorable for the production of polypyrrole in large quantities. The synthesized polypyrrole samples exhibit good electrical conductivity (2 S/cm) and yield of 80% for reaction time of 8 hr at 5°C. Quality and properties of polypyrrole samples have been thoroughly investigated with varying reaction time and temperature while other synthesis parameters like molar ratio of oxidant to monomer, oxidant concentration, and solvent were kept constant. X-ray diffraction analysis of polypyrrole with a shorter reaction time shows the presence of iron oxide (Fe2O3) peaks. The complete reaction may not occur at shorter reaction times due to which residual ferric ions converted into Fe2O3. X-ray photoelectron spectroscopy measurement of polypyrrole also confirms the formation of Fe2O3. Appropriate selection of reaction time and temperature produced pure phase polypyrrole with high yield and good conductivity. Synthesized polypyrrole by our eco-friendly and cost-effective technique exhibits prominent electromagnetic shielding effectiveness value of 30 dB in the X-band (8–12 GHz). 相似文献
62.
The objectives were to reduce bitterness in reduced-fat Cheddar cheese made with an exopolysaccharide (EPS)-producing culture and study relationships among ultra-filtration (UF), residual chymosin activity (RCA), and cheese bitterness. In previous studies, EPS-producing cultures improved the textural, melting, and viscoelastic properties of reduced-fat Cheddar cheese. However, the EPS-positive cheese developed bitterness after 2 to 3 mo of ripening due to increased RCA. We hypothesized that the reduced amount of chymosin needed to coagulate UF milk might result in reduced RCA and bitterness in cheese. Reduced-fat Cheddar cheeses were manufactured with EPS-producing and nonproducing cultures using skim milk or UF milk (1.2×) adjusted to a casein:fat ratio of 1.35. The EPS-producing culture increased moisture and RCA in reduced-fat Cheddar cheese. Lower RCA was found in cheese made from UF milk compared with that in cheese made from control milk. Ultrafiltration at a low concentration rate (1.2×) produced EPS-positive, reduced-fat cheese with similar RCA to that in the EPS-negative cheese. Slower proteolysis was observed in UF cheeses compared with non-UF cheeses. Panelists reported that UF EPS-positive cheese was less bitter than EPS-positive cheese made from control milk. This study showed that UF at a low concentration factor (1.2×) could successfully reduce bitterness in cheese containing a high moisture level. Because this technology reduced the RCA level (per g of protein) to a level similar to that in the control cheeses, the contribution of chymosin to cheese proteolysis would be similar in both cheeses. 相似文献
63.
Fatty acid modified polyurethane dispersion for surface coatings: Effect of fatty acid content and ionic content 总被引:1,自引:0,他引:1
Ashish Patel Chintankumar Patel M.G. Patel Mehul Patel Ashok Dighe 《Progress in Organic Coatings》2010
The higher molecular weight fatty acid modified polyurethane–urea dispersions (PUDs) were prepared with effective utilization of fatty acid and ionic emulsifier. The PUDs were prepared using oligomer of linoleic fatty acid, dimethylol propionic acid (DMPA), linear polyester diol, isophorone diisocyanate (IPDI), triethylamine (TEA) and ethylenediamine (EDA) by prepolymer mixing method. Resultant PUDs had so-called controlled branched polymer structures. To incorporate fatty acid residues in the backbone of the polyurethane two types of oligomers were used which were synthesized by esterifying linoleic acid and phthalic anhydride (PA) with different monomers having different hydroxyl functionality i.e. trimethylol propane (TMP), pentaerythritol and neopentyl glycol (NPG). The oligomers were mixed with linear polyester diol in different proportions and used as polyol part in prepolymer for PUDs. Various compositional variations such as type of oligomer, content of oligomer and ionic emulsifier were studied for stability and compatibility with water. The PUDs were also examined by FTIR, AFM, GPC, particle size analyzer, viscometer, TGA, DMA and tensile tester to analyze structures and properties. Chemical, water and corrosion resistances of the dried films were also evaluated to study the effect of oligomer content in modified PUDs. These properties are found to be significantly affected by the content and type of oligomer as well as ionic content in the polymer. 相似文献
64.
The fracture behavior of glass-cloth-reinforced composites has been studied. Fracture of these composites proceeds by tensile failure of fibers rather than by the shear failure of the matrix or the interface. Although the spread of damage in these composites is restricted to small distances away from the crack path due to the interweaving of the fibers, this distance is found to be appreciably larger for the samples with smaller initial crack lengths. Characteristic distances associated with the Whitney-Nuismer criteria are, in turn, found to be smaller for these composites than for the angle ply laminates or randomly oriented short-fiber composites reported in literature in which the spread of the damage is much greater. Analysis through the crack growth resistance also supports this correlation with the extent of damage spread and indicates that the critical crack length for these composites may be equal to the best fit value of the characteristic distance of the average stress criterion. 相似文献
65.
M. Sterlin Leo Hudson Himanshu Raghubanshi Seema Awasthi T. Sadhasivam Ashish Bhatnager Satoru Simizu S.G. Sankar O.N. Srivastava 《International Journal of Hydrogen Energy》2014
Graphene oxide (GO) has been prepared by employing modified Staudenmaier's method through thermal exfoliation of graphite oxide. High pressure hydrogen sorption isotherms up to 50 bar of GO, reduced by thermal reduction (TR-GO), chemical reduction (CR-GO) and graphene sheets decorated with Fe nanoclusters (Fe-GS) have been investigated. Thermal reduction of GO at 623 K under high vacuum yields TR-GO. Chemical reduction of GO using hydrazine forms CR-GO. Fe-GS was synthesized through arc-discharge between the ends of two graphite rods with one rod carrying Fe nanoparticles. The surface areas of these graphene samples were determined from the nitrogen adsorption isotherm employing Brunauer, Emmett and Teller (BET) method. Kelvin's equation was used to determine the pore size distribution of all graphene based samples. Hydrogen pressure-composition isotherms (PCI) were determined at 300 K and at 77 K, between 0.1 and 50 bar. Further, in this paper, we present a comparative adsorption isotherm analysis of hydrogen and helium on TR-GO. This reveals that the volume of hydrogen and helium adsorbed by TR-GO is nearly equal. The similar uptake volume determined for both hydrogen and helium indicates the possibility of monolayer adsorption of hydrogen and also nearly similar binding energy between TR-GO and H2/He. 相似文献
66.
The present study was aimed to utilize low‐cost alumina (Al2O3) nanoparticles for improving the heat transfer behavior in an intercooler of two‐stage air compressor. Experimental investigation was carried out with three different volume concentrations of 0.5%, 0.75%, and 1.0% Al2O3/water nanofluids to assess the performance of the intercooler, that is, counterflow heat exchanger at different loads. Thermal properties such as thermal conductivity and overall heat transfer coefficient of nanofluid increased substantially with increasing concentration of Al2O3 nanoparticles. Specific heat capacity of nanofluids were lower than base water. The intercooler performance parameters such as effectiveness and efficiency improved appreciably with the employment of nanofluid. The efficiency increased by about 6.1% with maximum concentration of nanofluid, that is, 1% at 3‐bar compressor load. It is concluded from the study that high concentration of Al2O3 nanoparticles dispersion in water would offer better heat transfer performance of the intercooler. 相似文献
67.
The aim of this report is to build a portable solar thermal bank based on a Scheffler reflector that is capable of boiling-type cooking using HITEC as a thermal storage material. This report reviews the problems related to solar cooking and evaluates the novel layout of a portable solar thermal bank which includes a daily thermal storage vessel. This stove is in the shape of a cylindrical container filled with phase-changing latent heat storage material. Inside the container, we provide a small gap taking into account the volumetric expansion of the phase change material (PCM) during the melting process. The solar thermal bank is charged in the sun. It is placed directly for a few hours under the focus of a Scheffler reflector, which charges the solar thermal bank with enough thermal energy stored. After a while, the cooking process can be completed by users using that stored heat. The top cavity is used as a cooking pot in a solar thermal bank. Cooking meals do not require direct sunlight, which is typical for most solar cookers. The portable solar thermal bank is an alternative for low-income households and adapts to local traditions of indoor cooking. It is portable and can be used safely to cook indoors or outdoors. In this study, a solar cooker with a thermal storage device was developed using a PCM. The size of the stove has been calculated by calculating the energy consumption for two to three people. HITEC salt has been chosen as a phase change material for thermal storage, which will be used for cooking when there is no sunlight. It enhances the applicability of solar cooking and preserves cooking possibilities using energy stored throughout the day at low production costs. 相似文献
68.
Ashish Nadar Atindra Mohan Banerjee M.R. Pai R.V. Pai Sher Singh Meena R. Tewari A.K. Tripathi 《International Journal of Hydrogen Energy》2018,43(1):37-52
Supported iron oxides have been established as an important class of catalyst for high temperature sulfuric acid decomposition. With an objective to elucidate the role of support in modifying the overall catalytic properties of dispersed iron oxide catalysts, a series of supported iron oxide based catalysts, Fe2O3 (15 wt%)/MO2 (M = Zr, Ce, Ti and Si), synthesized by adsorption-equilibrium method, is investigated for sulfuric acid decomposition reaction. The structure of dispersed iron oxide phases largely depended on the nature of the support oxide as revealed by the XRD and Mössbauer studies. α-Fe2O3 is found to be present as a major phase on ZrO2 and CeO2 support while ε-Fe2O3 was the major phase on silica supported iron oxide. On the other hand, presence of mixed oxide Fe2TiO5 was revealed over TiO2 support. Strong dispersed metal oxide-support interactions inhibited the total reduction of the dispersed phase on SiO2 and TiO2 as compared to complete reduction of dispersed iron oxide on CeO2 and ZrO2 supports during temperature programmed reduction upto 1000 °C. The order of catalytic activity at a temperature of ~750 °C is observed as Fe2O3/SiO2 > Fe2TiO5/TiO2 > Fe2O3/ZrO2 > Fe2O3/CeO2, while at higher temperatures of ~900 °C the SO2 yield is found to be comparable for all catalysts. A relationship between the rate of sulfate decomposition and catalytic activity is established through detailed TG-DTA investigations of sulfated catalyst and support. Considerable influence of the support oxide on the composition, structure, redox properties, morphology and catalytic activities of the active iron oxide dispersed phase has been observed. Thus, the support oxides operate as a critical component in the complex supported metal oxide catalysts and these findings might influence the design and development of future high temperature sulfuric acid decomposition catalysts. 相似文献
69.
3D Numerical study of temperature variation for subsonic rarefied gas flow in a microchannel is carried out using an in-house MPI-based parallelized DSMC code. The temperature drop in the microchannel decreases with an increase in the aspect ratio whereas it increases with an increase in the pressure ratio, the cross-aspect ratio (CAR), and the Knudsen number. 3D and 2D simulations results are compared and effect of the CAR and Knudsen number are brought out. Finally, a correlation that predicts the temperature drop is formulated along with a list of conditions that ensures a near isothermal flow. 相似文献
70.