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991.
为提升氧化锆陶瓷的使用性能,采用氧化钇稳定的四方氧化锆为基体(yttria stabilized tetragonal zirconia,3Y-TZP),将铝热法生产金属铬所得炉渣(铝铬渣)按照不同比例(质量分数为5%~15%)加入,利用无压烧结在1 400 ℃保温2 h制备出彩色氧化锆陶瓷。通过X射线衍射(XRD)、扫描电镜(SEM)、显微硬度计及万能材料试验机测试了试样的物相、显微结构及力学性能。结果表明:掺杂铝铬渣可以制备出粉红色系氧化锆复合陶瓷,其物相主要为四方氧化锆、单斜氧化锆和含铬的氧化铝,并且铝铬渣的加入促使更多的四方氧化锆保留到室温。铝铬渣的加入不利于试样的烧结致密性,随着其含量增加复合陶瓷烧结后的体积收缩率降低,基体内出现部分孔隙。但是,铝铬渣的加入提升了试样的力学性能,当其加入量为5%(质量分数)时,氧化锆复合陶瓷的显微硬度和抗折强度均达到最大值,分别为1 755.3 HV和421.3 MPa。 相似文献
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以纳米SiC为原料,用两面顶压机在不同工艺条件下(1100-1300℃,4.0-4.5GPa,20-35min)实现了无烧结助剂添加的SiC陶瓷体的烧结.研究了烧结工艺对SiC陶瓷性能的影响.用XRD、SEM、显微硬度测试仪等对SiC高压烧结体进行了表征.结果表明:采用超高压工艺可实现无烧结助剂SiC陶瓷高致密化烧结;烧结体晶粒长大得到抑制,维持在纳米级,晶格常数收缩发生了收缩;烧结体显微硬度和密度随烧结温度、烧结压力、保温时间的升高或延长而提高.在4.5GPa/1250℃/35min的超高压烧结条件下烧结的无烧结助剂SiC致密度达到96%,且显微硬度达到Hv1.96 3850. 相似文献
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The Regulatory Framework Across International Jurisdictions for Risks Associated with Consumption of Botanical Food Supplements
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Teng Yong Low Kwok Onn Wong Adelene L. L. Yap Laura H. J. De Haan Ivonne M. C. M. Rietjens 《Comprehensive Reviews in Food Science and Food Safety》2017,16(5):821-834
Dietary supplements, including those containing botanical ingredients and botanical‐derived compounds, have been marketed to consumers globally for many decades. However, the legislative framework for such products remains inconsistent across jurisdictions internationally. This study aims to compare the regulatory framework of botanical food supplements in the EU, USA, Canada, Australia, New Zealand, India, Japan, and China. The study also aims to investigate and describe safety assessment criteria for botanical food supplements where they are present in the above said jurisdictions, and attempts to analyze whether these criteria are suitable for addressing the toxicological risks associated with the use of botanical food supplement products, based on the evaluation of reported adverse effects related to botanical food supplement use as examples. Finally, this study discusses some future issues that need further attention, such as the consideration of less than lifetime exposures, potential for misidentification, and adulteration of botanical supplements by pharmacologically active substances. It is concluded that the regulatory approaches towards botanical food supplements differ significantly across jurisdictions. In addition, national authorities are increasingly considering having more regulatory oversight for such products. Further consideration of the actual impact of adverse events arising from botanical food supplement usage will be helpful in guiding such decisions. 相似文献
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以南京钟山琵琶湖景区联谊会所工程为例,提出了风景区建筑的设计原则;并在案例中尝试"敞"、"隐"、"聚"、"融"等设计手法,力求设计出属于"此时、此地、此景、此情"的风景区建筑. 相似文献
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喜树碱类衍生物的构效关系及其活性的研究进展 总被引:3,自引:0,他引:3
喜树碱具有抗肿瘤活性,但由于它的毒副作用及水溶性差而限制了对它的使用。目前,有不少关于对喜树碱分子结构改进和修饰的报道。许多高活性的喜树碱衍生物相继问世。本文对结构修饰和构效关系做一简要综述。 相似文献
1000.
It is well established that hydrogen has the potential to make a significant contribution to the world energy production.In U.S.,majority of hydrogen production plants implement steam methane reforming(SMR) for centralized hydrogen production.However,there is a wide lack of agreement on the nascent stage of using hydrogen as fuel in vehicles industry because of the difficulty in delivery and storage.By performing technological and economic analysis,this work aims to establish the most feasible hydrogen production pathway for automotives in near future.From the evaluation,processes such as thermal cracking of ammonia and centralized hydrogen production followed by bulk delivery are eliminated while on-site steam reforming of methanol and natural gas are the most technologically feasible options.These two processes are further evaluated by comprehensive economic analysis.The results showed that the steam reforming(SR) of natural gas has a shorter payback time and a higher return on investment(ROI) and internal rate of return(IRR).Sensitivity analysis has also been constructed to evaluate the impact of variables like NG feedstock price,capital of investment and operating capacity factor on the overall production cost of hydrogen.Based on this study,natural gas is prompted to be the most economically and technologically available raw material for short-term hydrogen production before the transition to renewable energy source such as solar energy,biomass and wind power. 相似文献