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991.
S.P AppleyardB Rand 《Carbon》2002,40(6):817-834
This paper reports the systematic characterisation of changes in the structure and properties of a series of unidirectional carbon-carbon composites at key stages of processing. The composites were fabricated from PAN-based carbon fibres (surface treated and untreated) and two carbon matrix systems (graphitising and non-graphitising). The effects of matrix shrinkage, together with thermal expansion mismatch and interfacial bonding, established the composite structure and hence the composite properties. The morphology and interconnectivity of the shrinkage cracks, the strength and nature of the fibre-matrix interfacial interaction and the development of matrix texture were identified as key structural features. These features were characterised and their effect on subsequent processing stages (densification) and composite properties was determined. 相似文献
992.
复合材料纤维缠绕成型CAD/CAM相关技术研究 总被引:2,自引:1,他引:2
纤维缠绕成型是制造高强度复合材料制品的一种重要的工艺方法,将CAD/CAM方法应用其中可以大大提高生产效率,降低设计成本。本文提出了纤维缠绕CAD/CAM系统的总体方案,并对其中缠绕数学模型、线型优化、丝嘴轨迹生成等量要组成部分进行了分析与研究,为CAD/CAM系统的开发奠定了理论基础。 相似文献
993.
O. K. Kamynina A. S. Rogachev L. M. Umarov 《Combustion, Explosion, and Shock Waves》2003,39(5):548-551
Deformation during gasless combustion of 5Ti + 3Si and Ti + C samples was studied experimentally. The dynamics of motion of the material in a gasless combustion wave was studied using highspeed video recording (500 frames/sec) with a spatial resolution of the order of 10 m. It was shown that behind the combustion front, the medium was first expanded and then compressed. The dimensions of the expansion and compression zones were determined. 相似文献
994.
Sweet potato pulp (SSP) obtained as a by‐product from starch extraction was blended with polycaprolactone (PCL) to prepare a biodegradable plastic material. In the blends, PCL was used as a reinforcing agent. The SPP/PCL blends were prepared by compression‐molding under high temperature and pressure, at different SPP/PCL ratios, and the mechanical properties of the molded specimens were tested. Matrix structure and thermal properties were measured by using a Fourier transform infrared (FTIR) spectrophotometer, scanning electron microscope (SEM), differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). Mechanical properties (tensile and flexural properties) were also measured to find the most suitable ratio in a SSP/PCL blend. During compression molding of the SPP/PCL blends under high pressure and temperature, chemical reaction occurred between SPP and PCL, and thus, thermal stability and mechanical strength of the blends increased and water uptake decreased. Also, by increasing the PCL content in the blend, the matrix in the blend became more homogeneous, and consequently, mechanical strength of the molded specimen increased. At 7/3 or 6/4 weight ratio of SSP/PCL, water uptake of the molded specimen became substantially less than that at 8/2. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 861–866, 2004 相似文献
995.
考察了Pd/Al2O3、In/Al2O3和Co/Al2O3对甲烷选择性还原NO的催化活性。结果表明,采用浸渍法制备的Pd/Al2O3、In/Al2O3和Co/Al2O3三种催化剂,在有氧气氛下,用CH4作还原剂催化还原NO时,Pd/Al2O3催化剂的活性最佳,热稳定性好,在550 ℃,用CH4选择还原NO,Pd/Al2O3催化剂表现出较强的催化能力,NO的转化率达到100%。在高空速实验中,该催化剂亦表现出较高的活性,其活性顺序为Pd/Al2O3>In/Al2O3>Co/Al2O3。实验研究了助催化剂、氧含量以及空速对Pd/Al2O3催化剂活性的影响。 相似文献
996.
Arturo J. Hernndez-Maldonado Gongshin Qi Ralph T. Yang 《Applied catalysis. B, Environmental》2005,61(3-4):212-218
Monolayer CuCl/γ-Al2O3 sorbent was studied for desulfurization of a commercial jet fuel (364.3 ppmw S) and a commercial diesel (140 ppmw S). The sorbent was prepared by means of spontaneous monolayer dispersion methods. Deep desulfurization (sulfur levels of <1 ppmw) was accomplished with this sorbent using a fixed-bed adsorber. The CuCl/γ-Al2O3 sorbent was capable of removing 6.4 and 11.2 mg of sulfur per gram for jet fuel at breakthrough (at <1 ppmw S) and saturation, respectively. The same sorbent was capable of removing 0.94 and 1.8 mg of sulfur per gram for BP diesel at breakthrough and saturation, respectively. The difference in sulfur capacities for jet fuel and diesel was apparently caused by the difference in concentrations of strongly binding compounds, such as nitrogen heterocycles, heavy (polynuclear) aromatics and fuel additives. In comparison with CuCl/γ-Al2O3, Cu(I)Y zeolite has higher sulfur capacities but is less stable and can be easily oxidized to Cu(II)Y by fuel additives (such as oxygenates) and moisture and consequently loses π-complexation ability. However, all these cuprous π-complexation sorbents selectively adsorb thiophenic compounds over aromatics and olefins (as predicted by the high separation factors), which resulted in the observed desulfurization capability. A feasibility study is shown for efficient regeneration of CuCl/γ-Al2O3 using ultrasound at ambient temperature. Possible problems associated with desulfurization using π-complexation sorbents for commercial fuels are discussed. 相似文献
997.
A catalyst for NOx storage/reduction was prepared to improve the activity of Ba–Pt/γ-Al2O3 by replacing Ba with a mixture of Ba and Mg. The catalyst was prepared by impregnating Pt and then co-impregnating Ba and
Mg (Mg:Ba molar ratio = 1) on commercial γ-Al2O3. The tests have been carried out in the presence of CO2 at temperatures between 200 and 400 °C in order to understand the role of both the feed and various alkaline-earth metals.
The storage capacity of the two catalysts was different like the mechanism in the reduction process. 相似文献
998.
Solvent assisted spreading of CoO over monolayer MoO3/Al2O3 catalysts has been studied. CoCO3 · Co(OH)2 and CoCO3 reacted with MoO3/Al2O3 in water slurries. CoO deposition over MoO3/Al2O3 extrudates was followed by EPMA. In the set of eleven MoO3/Al2O3 catalysts, the amount of CoO adsorbed was roughly proportional to the surface area of MoO3 monolayer. The adsorbed Co species efficiently enhanced the HDS activity. 相似文献
999.
改性木粉/PVC复合材料的研究进展 总被引:1,自引:0,他引:1
概述了PVC木塑复合材料的发展和背景与性能。简述了木质材料的性质和木粉改性的方法,如物理方法和化学方法。介绍了木塑复合材料的生产流程、成型方法(模压成型、挤出成型、注射成型及其成型设备,讨论了对工艺参数的一些要求。指出目前国内PVC木塑复合材料发展存在的一些问题,并指明了PVC木塑复合材料的应用前景。 相似文献
1000.
Wang-Gi Kim Jaeyoung Yang Sangsup Han Chanhwi Cho Chang-Ha Lee Hanju Lee 《Korean Journal of Chemical Engineering》1995,12(5):503-511
An experimental and theoretical study is performed for bulk separation of H2/CO2 mixture (70/30 volume %) by PSA process with zeolite 5A, a process widely used commercially in conjunction with the catalytic
steam reforming of natural gas or naphtha. For the optimized adsorption conditions of PSA, the characteristics of adsorption/desorption
characteristics have been studied through breakthrough and desorption experiments under various conditions. The purge-to-feed
ratio is important to the H2 product purity only at a long adsorption step time. H2 could be concentrated from 70% in the feed to 99.99% at H2 recovery of 67.5%. The results of all five steps in PSA are successfully predicted by the LDF model considering an energy
balance and nonlinear isotherm. For the model, the effective diffusivities (D,) are obtained separately from the uptake curves
of H2 and CO2. The Langmuir-Freundlich isotherm is used to correlate the experimental equilibrium data and is very well fitted to the results. 相似文献