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971.
972.
973.
Carbon/carbon composites were made through the pyrolysis of stabilized PAN felt and phenolic resin with the addition of 5 or 10 wt % carbon black to the matrix and then heat treatment at 600–2500°C. The effects of adding carbon black to the matrix precursor on the physical properties, microstructure, and mechanical properties of the resultant composites were investigated. Adding carbon black not only reduced the weight loss but also limited the shrinkage of the resultant composites. Adding carbon black also accelerated the formation of carbon basal planes in the matrix. At 2500°C, the crystalline stacking height in the composite with 10 wt % added carbon black was 200% greater than that with no additive. The flexural strength of the composite also increased from 15 to 42 MPa (almost 300%). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 333–337, 2006 相似文献
974.
975.
反相微乳液法制备高溶度ZrO2陶瓷墨水(Ⅱ) 总被引:10,自引:0,他引:10
对喷墨打印成型用ZrO2陶瓷墨水的反相微乳液制备法进行了研究.采用已经优化的Triton x-100/正己醇/环己烷/水反相微乳液体系, 以氧氯化锆溶液和氨水溶液分别替代水, 获得了澄清的微乳液, 再将它们均匀混合反应制得了均匀分散、微粒尺寸7~8 nm、稳定存在的ZrO2陶瓷墨水.针对喷射打印墨水的理化性能要求, 考察了所制备的ZrO2陶瓷墨水的理化性能(流变性能、表面张力、电导率、稳定性等), 并对性能改善进行了探讨.所制两个陶瓷墨水当pH<8时, 电导率分别为20 mS/m和35 mS/m, 表面张力分别为21.6 mN/m和34.3 mN/m左右, 粘度为25 mPa*s和32 mPa*s, 且无剪切增稠效应.这些结果说明所制陶瓷墨水的性能指标基本满足非连续式打印机要求.从透光率测试结果表明所制陶瓷墨水属反相微乳液. 相似文献
976.
Paul F. Becher Peter Angelini W. H. Warwick Terry N. Tiegs 《Journal of the American Ceramic Society》1990,73(1):91-96
Alumina composites reinforced with 20 vol% SiC whiskers were exposed to applied stresses in four-point flexure at temperatures of 1000°, 1100°, and 1200°C in air for periods of up to 14 weeks. At 1000° and 1100°C, an "apparent" fatigue limit was established at stresses of ∼ 75% of the fast fracture strength. However, after long-term (>6 weeks) tests at 1100°C, some evidence of crack generation as a result of creep cavitation was detected. At 1200°C applied stresses as low as 38% of the 1200°C fracture strength were sufficient to promote creep deformation and accompanying cavitation and crack generation and growth resulting in failures in times of <250 h. 相似文献
977.
978.
Field Validation of DNDC Model for Methane and Nitrous Oxide Emissions from Rice-based Production Systems of India 总被引:6,自引:0,他引:6
Y. Jagadeesh Babu C. Li S. Frolking D. R. Nayak T. K. Adhya 《Nutrient Cycling in Agroecosystems》2006,74(2):157-174
The DNDC (DeNitrification and DeComposition) model was tested against experimental data on CH4 and N2O emissions from rice fields at different geographical locations in India. There was a good agreement between the simulated
and observed values of CH4 and N2O emissions. The difference between observed and simulated CH4 emissions in all sites ranged from −11.6 to 62.5 kg C ha−1 season−1. Most discrepancies between simulated and observed seasonal fluxes were less than 20% of the field estimate of the seasonal
flux. The relative deviation between observed and simulated cumulative N2O emissions ranged from −237.8 to 28.6%. However, some discrepancies existed between observed and simulated seasonal patterns
of CH4 and N2O emissions. The model simulated zero N2O emissions from continuously flooded rice fields and poorly simulated CH4 emissions from Allahabad site. For all other simulated cases, the model satisfactorily simulated the seasonal variations
in greenhouse gas emission from paddy fields with different land management. The model also simulated the C and N balances
in all the sites, including other gas fluxes, viz. CO2, NO, NO2, N2 and NH3 emissions. Sensitivity tests for CH4 indicate that soil texture and pH significantly influenced the CH4 emission. Changes in organic C content had a moderate influence on CH4 emission on these sites. Introducing the mid-season drainage reduced CH4 emissions significantly. Process-based biogeochemical modeling, as with DNDC, can help in identifying strategies for optimizing
resource use, increasing productivity, closing yield gaps and reducing adverse environmental impacts. 相似文献
979.
In the present study, the effects of charge‐transfer complex formation and intramolecular fragmentation (side‐chain lactonization) in radical copolymerization of tert‐butyl vinyl ether (t‐BVE) with anhydrides of maleic (MA) and citraconic (CA) acids and the structure–thermal behavior relationships of the resulting copolymers were examined using the 1H‐NMR, FTIR, DSC, and TGA analysis methods. It was shown that copolymerization under the chosen conditions proceeded through intramolecular fragmentation with the formation of γ‐lactone units. Side‐chain fragmentation of t‐BVE–MA and t‐BVE–CA copolymers also was confirmed by TGA and DSC analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2455–2463, 2006 2006 相似文献
980.