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811.
A simple theory of electrolyte conductance is coupled electric/magnetic fields is presented. The procedure for estimating the relative importance of Hall conductivity is quicker than others hitherto proposed. 相似文献
812.
The study of a downward gas jet was performed in a two–dimensional (2–D) fluidized bed of sand particles under conditions of minimum fluidization and at atmospheric pressure and room temperature. The jet shifted through a cyclic sequence of left–central–right–central–left positions. The probability of the left and right jets was 40% each, while the less stable central jet occurred only 20% of the time. Discrete probability distributions of jet presence for each of the three jet configurations and an overall distribution are presented. They show that jets are dominant along the external walls of the nozzle. The depth of the downward jet increased with air flowrate in agreement with the correlation from Massimilla and Russo (1973). 相似文献
813.
A fast pyrolysis (Ultrapyrolysis) process was employed to convert automobile shredder residue (ASR) into chemical products. Experiments were conducted at atmospheric pressure and temperatures between 700 and 850°C with residence times between 0.3 and 1.4 seconds. Pyrolysis products included 59 to 68 mass% solid residue, 13 to 23 mass% pyrolysis gas (dry) and 4 to 12 mass% pyrolytic water from a feed containing 39 mass% organic matter and 2 mass% moisture. No measurable amounts of liquid pyrolysis oil were produced. The five most abundant pyrolysis gases, in vol%, were CO (18–29), CO2 (20–23), CH4 (17–22), C2H4 (20–22) and C3H6 (1–11), accounting for more than 90% of the total volume. The use of a higher organic content ASR feed (58 mass%) resulted in less solid residue and more pyrolysis gas. However, no significant changes were noted in the composition of the pyrolysis gas. 相似文献
814.
L. T. Guan F. G. Du G. Z. Wang Y. K. Chen M. Xiao S. J. Wang Y. Z. Meng 《Journal of Polymer Research》2007,14(3):245-251
Completely biodegradable foams of poly(propylene carbonate) (PPC) derived from carbon dioxide and propylene oxide were fabricated
using N, N′-dinitroso pentamethylene tetramine (DPT) as chemical blowing agent, and urea as the activator to lower the decomposition
temperature of DPT. Thermal decomposition behavior and gas evolution behavior of the DPT composite with various urea to DPT
ratios were investigated to optimize the composition of the blowing agent. The formulation of blowing agent mixture and foaming
condition, the foam morphologies, the molecular weight change, as well as the mechanical properties of produced PPC foams
were studied extensively. The experimental results demonstrated that the greatest blowing ratio of 14.8 can be afforded in
case 12 phr blowing agent was used at 170 °C for 30 min. Gel permeation chromatography (GPC) and thermal analysis revealed
that DPT acted as both chain-extension agent and blowing agent for PPC matrix. The molecular weight of PPC subjected to foaming
increased by 76%. The foamed PPC exhibited superior mechanical properties and can be used as packaging material for many practical
applications. 相似文献
815.
Pozzolanic properties of reject fly ash in blended cement pastes 总被引:2,自引:0,他引:2
Low-grade fly ash (reject fly ash, r-FA), a significant portion of the pulverized fuel ash (PFA) produced from coal-fired power plants and rejected from the ash classifying process, has remained unused due to its high carbon content and large particle size. But it may be used in certain areas, such as in solidification and stabilization processes of hazardous waste and materials for road base or subbase construction, which require relatively lower strength and reactivity. It is therefore necessary to extend research on the properties of r-FA and explore its possible applications. This paper presents experimental results of a study on the mechanical and hydration properties of cementitious materials prepared by blending r-FA with ordinary Portland cement (OPC). Parallel mixes were also prepared with the good ash [i.e., classified fine fly ash (f-FA)] for comparison. Selective chemical activators were added to the mix to study the effects of the activators on the properties of the blend system. The results show that r-FA generally has a lower rate of hydration than f-FA particularly at the early stage of hydration. Adding Ca(OH)2 alone almost had no effect on accelerating the hydration of r-FA. But adding a small quantity of Na2SO4 or K2SO4 together with Ca(OH)2 significantly accelerated the hydration reaction. The results of the compressive strength measurement correlated nicely with the degree of hydration results. It was also found that water-to-binder ratio (w/b) was an important factor in affecting the strength development and the hydration degree of r-FA pastes. 相似文献
816.
817.
Schubert U.-A. Anderle F. Spengler J. Zühlke J. Eberle H.-J. Grasselli R.K. Knözinger H. 《Topics in Catalysis》2001,15(2-4):195-200
Titania-supported vanadia catalysts were modified by addition of antimony oxide for application in o-xylene selective oxidation to phthalic anhydride. It was shown that active and selective catalysts can be prepared by ball-milling mixtures of powders of TiO2, V2O5and Sb2O3followed by calcination. X-ray photoelectron spectroscopy proves the formation of highly dispersed overlayers of vanadium oxide and antimony oxide, in which V5+is partially reduced to lower oxidation states and Sb3+is partially oxidized to Sb5+. Antimony oxide segregated into the outermost surface layers. It is therefore inferred that the presence of the antimony oxide modifier spatially separates V–O species and leads to site isolation which may be responsible for the positive effect of the modifier for the catalyst's selectivity. 相似文献
818.
Effects of filler on microstructure and toughening behavior of cyanate ester (CE)/bentonite (BT) nanocomposites with different content of BT have been studied by positron annihilation lifetime spectroscopy, X‐ray diffraction, transmission electron microscopy, dynamic mechanical analysis, etc. The interesting results found by PALS indicate that the size and concentration of the free volume holes and the apparent free volume fraction increased with increasing the content of BT, which indicates that adding nano‐layers to thermosetting materials can lead to the high crosslinking density structure “looser.” The experimental results reveal that the increases in size of free volume holes and apparent free volume fraction are related to the increasing conversion of cure reaction. On the other hand, the mechanism of toughening (by adding the nano‐clay to the thermosetting material) has been discussed by combining free volume and interfacial property. It is shown that, for the high crosslinking thermosetting material‐based nanocomposites, both the property of free volume and dispersion state of nano‐layers are the two key factors in determining toughening property. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1509–1515, 2006 相似文献
819.
The research and development of catalysts, the design and operation of catalytic reactors are complicated by the phenomenon of catalyst deactivation which is affected by various factors. In this paper, the effect of internal mass transfer resistance in the second order catalytic reaction system of uniform independent deactivation on both reaction and deactivation rates of straight cylindrical pore model has been discussed. In addition, the quantitative relations between effectiveness factor and Thiele modulus in second order reaction and first order deactivation system have been correlated 相似文献
820.
Cotton cellulose was independently oxidized with potassium periodate, potassium dichromate-sulfuric acid, and potassium dichromate–oxalic acid, and the resulting oxidized celluloses were further modified by treatment with chlorous acid or sodium borohydride. The various modified celluloses so obtained were grafted with 2-methyl-5-vinylpyridine using a thiourea–dioxide–H2O2 redox system. It was found that the initiation characteristics of the cellulose samples vary widely with the oxidizing agent used. Further modification of the oxidized celluloses by treating them with chlorous acid enhances considerably their susceptibility toward grafting. The opposite holds true when these oxidized celluloses were modified by sodium borohydride treatment. Excluding thiourea dioxide from the polymerization system offsets grafting onto cotton cellulose while considerable grafting takes place on the various oxidized celluloses and their further modified samples. The work was also extended to study the factors which affect the graft uptake, homopolymer formation, and total conversion. In addition, the reactions involved in initiation of grafting were elucidated. 相似文献