Catalytic reduction reactions using isopropanol(IPA)as a transfer hydrogenating agent are gaining significant attention due to the low cost and large-scale production of IPA.Traditional methods for carbon-carbon(C—C)...Catalytic reduction reactions using isopropanol(IPA)as a transfer hydrogenating agent are gaining significant attention due to the low cost and large-scale production of IPA.Traditional methods for carbon-carbon(C—C)bond construction often rely on expensive and scarce transition metal catalysts,raising concerns about sustainability and environmental impact.To address these challenges,we develop a bifunctional photocatalyst,phloroglucinol carbon quantum dot(PG-CQD).It facilitates catalytic transfer hydrogenation(CTH)with IPA as the hydrogen donor.PG-CQDs exhibit both dehydrogenation and reduction activities,enabling the formation of vicinal diols under mild conditions with visible light irradiation.We propose a CTH mechanism that has been successfully validated through experiments.The catalytic system demonstrates remarkable versatility,enabling the synthesis of various vicinal diols from diverseα-keto ester substrates with good or excellent yields.These findings offer a sustainable synthetic strategy that aligns with green chemistry principles and establish a promising pathway for the development of environmentally benign and energy-efficient organic transformations.展开更多
GH4169合金拥有良好的强度及的抗疲劳性能,被广泛用于航天航空发动机合金盘件,但因其服役环境恶劣,在长时间服役过程中产生的蠕变形变会影响航空发动机正常工作及装配。为分析GH4169高温合金材料蠕变行为,通过拉伸试件在650℃下不同应...GH4169合金拥有良好的强度及的抗疲劳性能,被广泛用于航天航空发动机合金盘件,但因其服役环境恶劣,在长时间服役过程中产生的蠕变形变会影响航空发动机正常工作及装配。为分析GH4169高温合金材料蠕变行为,通过拉伸试件在650℃下不同应力水平的蠕变变形规律,综合考虑θ参数法与Combined Time Hardening两种本构模型,建立适应于不同应力水平的蠕变耦合模型,编写耦合模型用户子程序。基于Abaqus,通过弹塑性有限元分析,验证蠕变耦合模型子程序的计算合理性。进一步将耦合模型应用于某涡轮盘的蠕变变形分析中,并与旋转蠕变实验进行对比,研究结果表明:建立的基于θ参数法与CTH蠕变模型的耦合模型可以更加准确地描述GH4169高温合金在不同应力水平下的蠕变行为;对于涡轮盘来说,随蠕变时间的累积,盘芯处蠕变最突出且伴随着一定的应力松弛现象,对盘件结构设计的改善具有工程指导意义。展开更多
基金National Natural Science Foundation of China(Nos.21902023 and 21901252)Shanghai Pujiang Program,China(No.19PJ1400300)+1 种基金Professor of Special Appointment(Eastern Scholar),ChinaShanghai Institutions of Higher Education Fundamental Research Funds for the Central Universities,China(No.0900000155)。
文摘Catalytic reduction reactions using isopropanol(IPA)as a transfer hydrogenating agent are gaining significant attention due to the low cost and large-scale production of IPA.Traditional methods for carbon-carbon(C—C)bond construction often rely on expensive and scarce transition metal catalysts,raising concerns about sustainability and environmental impact.To address these challenges,we develop a bifunctional photocatalyst,phloroglucinol carbon quantum dot(PG-CQD).It facilitates catalytic transfer hydrogenation(CTH)with IPA as the hydrogen donor.PG-CQDs exhibit both dehydrogenation and reduction activities,enabling the formation of vicinal diols under mild conditions with visible light irradiation.We propose a CTH mechanism that has been successfully validated through experiments.The catalytic system demonstrates remarkable versatility,enabling the synthesis of various vicinal diols from diverseα-keto ester substrates with good or excellent yields.These findings offer a sustainable synthetic strategy that aligns with green chemistry principles and establish a promising pathway for the development of environmentally benign and energy-efficient organic transformations.
文摘GH4169合金拥有良好的强度及的抗疲劳性能,被广泛用于航天航空发动机合金盘件,但因其服役环境恶劣,在长时间服役过程中产生的蠕变形变会影响航空发动机正常工作及装配。为分析GH4169高温合金材料蠕变行为,通过拉伸试件在650℃下不同应力水平的蠕变变形规律,综合考虑θ参数法与Combined Time Hardening两种本构模型,建立适应于不同应力水平的蠕变耦合模型,编写耦合模型用户子程序。基于Abaqus,通过弹塑性有限元分析,验证蠕变耦合模型子程序的计算合理性。进一步将耦合模型应用于某涡轮盘的蠕变变形分析中,并与旋转蠕变实验进行对比,研究结果表明:建立的基于θ参数法与CTH蠕变模型的耦合模型可以更加准确地描述GH4169高温合金在不同应力水平下的蠕变行为;对于涡轮盘来说,随蠕变时间的累积,盘芯处蠕变最突出且伴随着一定的应力松弛现象,对盘件结构设计的改善具有工程指导意义。
