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排序方式: 共有245条查询结果,搜索用时 15 毫秒
1.
热塑性聚氨酯增韧改性聚甲醛的研究 总被引:1,自引:0,他引:1
本文对POM/TPPU/Z-3共混体系进行了研究,结果表明,增容剂Z-3可控制共混体系中分散相的颗粒尺寸及分布,起着聚集剂的作用。随着TPPU用量的增加,共混合金的结晶度和拉伸强度增降低,缺口冲击强度出现峰值,MI下降,当POM/TPPU/Z-3=100/7/0.49时,共混合金的缺口冲击强度达到最大值。 相似文献
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The partial oxidation of methane to synthesis gas was studied at atmospheric pressure and in the temperature range of 550–800°C over -Al2O3-supported bimetallic Pt–Co, and monometallic Pt and Co catalysts, respectively. Both methane conversion and CO selectivity over a bimetallic Pt0.5Co1 catalyst were higher than those over monometallic Pt0.5 and Co1 catalysts. Furthermore, the addition of platinum in Pt–Co bimetallic catalysts effectively improved their resistance to carbon deposition with no coking occurring on Pt0.5Co1 during 80 h reaction. The FTIR study of CO adsorption observed only linearly bonded CO on bimetallic Pt–Co catalysts. TPR and XPS showed enhanced formation of a cobalt surface phase (CSP) in bimetallic Pt–Co catalysts. The origins of the good coking resistivity of bimetallic Pt–Co catalysts were discussed. 相似文献
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聚甲醛的强韧化改性研究 总被引:2,自引:0,他引:2
分别以热塑性聚氨酯和短切玻璃纤维为增韧剂和增强剂,以传统的共混方式,对聚甲醛进行了增韧和增强改性研究,获得了强度和韧性同时提高的改性材料。 相似文献
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光屏蔽剂对聚甲醛老化过程结构与性能的影响 总被引:1,自引:0,他引:1
采用炭黑和氧化锌两种光屏蔽剂对共聚甲醛进行耐老化改性。研究了改性前后聚甲醛在紫外光老化及热氧老化过程中的表面层及内部发生的微观物理化学变化,包括熔点、结晶度、表面羰基量及分子量变化等。结果表明,紫外光的照射主要导致聚甲醛试样表面层发生晶体破坏和无定形部分分子链降解,内层则主要发生非晶区重整结晶;热氧作用下聚甲醛发生氧化降解的同时整体较均匀地发生非晶区重整结晶,以上情况均导致聚甲醛结晶度上升、拉伸强度提高,但抗冲击韧性及断裂伸长率显著下降,如经过1000 h紫外光辐照后,聚甲醛表面层结晶度由42.06% 上升至 76.27%,而简支梁缺口冲击强度由6.74 kJ/m2 迅速下降至1.85 kJ/m2。通过添加1.5%~3%的炭黑或氧化锌可以有效地抑制紫外光对聚甲醛的降解和重结晶过程,从而提高材料老化后的性能保持率,但炭黑对抗氧剂过强的吸附力导致聚甲醛的热氧稳定性下降。 相似文献
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LI Yok-sheung 《水动力学研究与进展(B辑)》2011,23(1):95-104
A severe typhoon Utor,occurring between July 3 and 8,2001,brought heavy rainfall,strong wind and storm surge.Utor was responsible for tremendous destruction and economic losses in Philippines,Taiwan and Guangdong.An air-sea model system (MM5 and Princeton Ocean Model(POM))was built to simulate meteorological dynamics and ocean circulation in the South China Sea(SCS).In the POM the output of MM5 was used as the input data.With an increased number of vertical levels,a high-resolution planetary boundary layer scheme and updated landuse/vegetation data,the accuracy of computing wind,temperature and other meteorological fields are improved in near surface and upper levels in MM5 simulations.The simulated trajectory and wind speed of Utor are close to the observed results.The simulated distribution of rainfall is accorded well with measured data in the Pearl River Delta(PRD)area.At different meteorological stations in Hong Kong,the wind,temperature and sea surface pressure are well simulated.The simulated ocean surface current and surface temperature fields have an obvious rightward-biased response to the typhoon Utor,and the maximum velocity and the lowest temperature region appear in the 30 km of the right side of the typhoon track.The typhoon Utor could make the water 50m under the surface ocean unwell to surface and the ocean surface temperature decrease by about 2°C. 相似文献
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采用机械共混法制备了MP/TPU/POM复合材料,借助RH2000型毛细管流变仪研究了改性前后POM的流变性能。结果表明,复合阻燃剂的加入并没有改变POM的假塑性特征,阻燃POM仍为假塑性流体,其表观黏度随剪切速率的增加而降低;阻燃POM的黏流活化能和表观黏度随温度的升高而降低,其对温度的敏感性低于纯POM;阻燃后POM的非牛顿指数降低,非牛顿性增强。 相似文献
10.
《International Journal of Hydrogen Energy》2022,47(5):3001-3012
The efficient visible light-driven photoelectrocatalyst (denoted as g-C3N4-CO-TETA-Pr-SiW11) was designed through the organic linker strategy by combination of polyoxometalate (POM) (cluster of [SiW11O39]?8 (SiW11)) with graphitic carbon nitride (g-C3N4). For this purpose, a reactive tetradentate NH2 linker was introduced by oxidation and subsequently amidation reactions on the surface of g-C3N4 frameworks then SiW11 was bonded to the organic linker to generate g-C3N4-CO-TETA-Pr-SiW11. In this study, for the first time, this organic linker strategy was applied for covalent combination of POM and g-C3N4 to design a stable photocatalyst with high-performance. Photoelectrocatalytic performance of prepared catalysts was investigated under visible light irradiation. The photocurrent density of 0.17 mA cm?2 for g-C3N4-CO-TETA-Pr-SiW11 compared with 0.077 mA cm?2 for g-C3N4 was achieved. Investigation of the transient open circuit potential decay and photoluminescence showed the efficient electron-hole separation for g-C3N4-CO-TETA-Pr-SiW11. The arc diameter in Nyquist plots indicated the improved charge transfer and charge carrier's lifetimes after decorating of g-C3N4 with POM. Mott?Schottky plots demonstrated a greater electron transfer at the photo electrode/electrolyte interface for g-C3N4-CO-TETA-Pr-SiW112.8 in compared to g-C3N4. Also, the photoconversion efficiency exhibited more than 2.4 time enhancement for g-C3N4-CO-TETA-Pr-SiW11 photoanode compared to g-C3N4. 相似文献