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991.
Temperature measurements have been performed in the process of electron‐beam curing of EB‐I and EB‐II epoxy resin systems. The influence of initiator content, resin type, and dose rate on the temperature of the systems was studied. Transverse and longitudinal temperatures of samples in the glass vessel were also analyzed. The nature of temperature curves varied with the different epoxy resin systems in the steel mold, but did not change with different contents of the initiator. At the same time, the heat had no effect on the gel fraction of epoxy resin systems. The temperature curve was greatly affected by the dose rate, and its peak value, peak width, and plateau value also increased with it. The transverse temperature of EB‐II glass vessel samples increased as the radiation dose increased and, in the same sample, the temperature reduced as the distance between the radiation center and the test point increased. The longitudinal temperature of EB‐I and EB‐II resin systems in a glass vessel decreased as the radiation depth increased. As the radiation dose increased, the temperature of the EB‐I resin system increased simultaneously, while that of the EB‐II resin system initially increased and then kept constant when the dose reached a certain value. The temperatures of these two resin systems decreased rapidly when the radiation process stopped. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2217–2222, 2004 相似文献
992.
Polysiloxane loaded with SiC as inert filler, and Al as active filler, was pyrolyzed in nitrogen to fabricate SiOC composites, and the processing and properties of the filled SiOC composites were investigated. Adding SiC fillers could reduce the linear shrinkage of filler-free cured polysiloxane in order to obtain monolithic SiC/SiOC composites. The flexural strength of SiC/SiOC composites reached 201.3 MPa at a SiC filler content of 27.6 vol.%. However, SiC/SiOC composites exhibited poor oxidation resistance, thermal shock resistance and high temperature resistance. Al fillers could react with hydrocarbon generated during polysiloxane pyrolysis at 600 °C and N2 at 800 °C to form Al4C3 and AlN, respectively. The volume expansions resulting from these two reactions were in favor of the reduction in linear shrinkage and the improvement in flexural strength of SiC/SiOC composites. The flexural strength of Al-containing SiC/SiOC composites was 1.36 times that of SiC/SiOC composites without Al at an Al filler content of 20 vol.%. The addition of Al fillers remarkably improved the high temperature resistance and oxidation resistance of SiC/SiOC composites, but not thermal shock resistance. 相似文献
993.
Ion beam irradiation can be used to modify the structure and gas transport properties of glassy polymers. This is the first of two studies that focus on the impact of H+ ion irradiation on the structure and permeation properties of the polyimide Matrimid®. Specifically, the evolution in chemical structure after H+ irradiation over a range of fluences was analyzed using FTIR spectroscopy and dissolution studies. Although H+ ion irradiation at very low ion fluences induced little modification in the chemical structure, irradiation at relatively high ion fluences resulted in crosslinking of the irradiated films. The branched structure of the aliphatic methyl (CH3) was the most sensitive to the H+ ion irradiation. The para‐disubstituted aromatic ring showed the strongest resistance toward ion irradiation and required fairly high doses to induce degradation. Two potential crosslinking mechanisms related to the degradation of the aliphatic methyl and the benzophenone carbonyl were presented. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2010–2019, 2003 相似文献
994.
Ti-oxides incorporated within the framework of microporous zeolites and mesoporous molecular sieves were found to exhibit
high and unique photocatalytic activity for the decomposition of NO into N2 and O2 as well as the reduction of CO2 with H2O to produce CH4 and CH3OH. Spectroscopic investigations of these catalytic systems using photoluminescence, UV-vis, XAFS (XANES and FT-EXAFS) and
IR analyses revealed that the charge transfer excited state of the isolated tetra-coordinated Ti-oxides plays a vital role
in these photocatalytic reactions. The reactivity of such Ti-oxides was found to depend strongly on their local structures
which were controlled by the unique framework structures of the micro- and mesoporous material supports. 相似文献
995.
磷铝酸盐水泥浆体的抗冻性研究 总被引:1,自引:0,他引:1
抗冻性是砼耐久性的重要方面,尤其影响北方地区砼工程的使用寿命。引气能提高砼的抗冻性,但同时又存在气泡的稳定性问题和砼其他性能的受损问题。若能提高砼中水泥浆体的抗冻性,则对提高砼耐久性更有意义。作者从宏观和微观两方面研究了磷铝酸盐水泥浆体的抗冻性,同时与硅酸盐水泥、硫铝酸盐水泥浆体进行了比较;采用压汞测孔方法测试了三种水泥浆体冻融前后的孔结构,并用分形理论分析了各自特征。结果证实:磷铝酸盐水泥具有优越的抗冻融性能,其自身优良的水化特性以及体系的低碱度是良好抗冻性的内在原因。 相似文献
996.
提高镁回收率的途径及效益分析:白云石碳酸化法生产轻质碳酸镁新工艺研究 总被引:11,自引:0,他引:11
本文提出了白云石碳酸化法生产轻质碳酸镁,二次碳酸化法新工艺的理论依据、实验结果及技术经济分析。 相似文献
997.
Dynamic properties of polymethylvinylsiloxane (PMVS) filled with filler‐blends composed of carbon black (CB) and silica (SiO2) were investigated using an advanced rheometric expansion system. A variety of weight fraction of CB to SiO2 were 0/100, 10/90, 30/70, 50/50, 70/30, 90/10, and 100/0, and a bifunctional organsilane, bis(3‐triethoxysilylpropyl)tetrasurfane, was used to facilitate the filler dispersion. The results reveal that the incorporation of CB/SiO2 filler‐blends into PMVS result in a reduced Payne effect. This effect reaches a minimum when the ratio of CB/SiO2 approaches 1, and then it began to rebound with the ratio increase. Meanwhile, a characteristic Newtonian viscosity plateau appearing in low frequencies also significantly decreases, depending on the amount of CB or SiO2 added. On the basis of a simplified Fowke model, we ascribe this phenomenon to the deteriorated filler network, which is predominantly induced by the totally different surface activity between CB and SiO2. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3477–3482, 2006 相似文献
998.
999.
Baoqing Deng Shanshan Kong Chang Nyung Kim 《Korean Journal of Chemical Engineering》2007,24(4):577-582
In this paper, a mathematical model is presented to describe the photocatalytic degradation of VOCs in a packed bed reactor.
Here, the adsorption of VOCs on the wall of the reactor is taken into account and the diffusion of VOCs in the axial direction
is neglected. First-order kinetics is used to describe the photocatalytic oxidation of VOCs. The analytical solution of the
present model is obtained by traveling wave method. The solution shows that the reactor performance is totally dependent on
the inlet concentration of VOCs when the time is large enough. The present model is validated through the experimental result
of the photocatalytic oxidation of trichloroethylene in a packed bed and the predicted results accord well with the experimental
data. The influence of flow rate and inlet concentration on the performance of the reactor is discussed in detail. High flow
rate offers high reaction rate and low conversion efficiency. The different inlet conditions and different reaction patterns
are also investigated. The model would be useful to estimate the rate constant and help to the design of the reactor. 相似文献
1000.
Adsorption and antibacterial effect of copper-exchanged montmorillonite on Escherichia coli K88 总被引:1,自引:0,他引:1
Calcium montmorillonite (Ca-MMT), sodium montmorillonite (Na-MMT) and acid-activated montmorillonite (AAM), and their Cu2+-exchanged montmorillonites (Cu-MMT), Cu*Ca-MMT, Cu*Na-MMT and Cu*AAM, were used to study the antibacterial activity on Escherichia coli K88. AAM, Na-MMT and Ca-MMT showed some ability to reduce bacterial plate counts by 37.4%, 13.4% and 14.2%, respectively. Exchanging the montmorillonite with Cu2+ enhanced the antibacterial activity. The Cu*AAM, Cu*Na-MMT and Cu*Ca-MMT reduced the bacterial plate counts by 98.6%, 97.5% and 95.6%. Attempts were made to study the desorption of Cu2+ by washing with sterile physiological saline solution for 24 h. The washing solutions did not show a significant reduction of the bacterial counts, while the washed Cu-MMT retained their full antibacterial activity. Results from time-depending studies showed that the reduction of the bacterial counts by Cu-MMT increased during 24 h. The ranking of antibacterial activity of the three Cu-MMT was as Cu*AAM > Cu*Na-MMT > Cu*Ca-MMT. E. coli thrived optimally in a pH range from 5 to 7. Beyond this range, the bacterial counts decreased as the pH reduced the viability of the bacteria. The ranking of antibacterial activity of Cu-MMT was not affected by pH. The mechanism by which bacterial counts are reduced may involve the enhanced affinity of Cu-MMT for E. coli K88 and the antibacterial activity of Cu2+. 相似文献