Based on the strength and microstructure tests,the effects of the hydantoin epoxy resin content and curing time on the mechanical properties and microstructure of copper tailings specimens were studied.The results sho...Based on the strength and microstructure tests,the effects of the hydantoin epoxy resin content and curing time on the mechanical properties and microstructure of copper tailings specimens were studied.The results showed that the strength of the solidified specimens was increased to 20.84 MPa with 30 wt.%addition of hydantoin epoxy resin.When the specimens with 10%hydantoin epoxy resin were cured for 7 and 14 d,the strengths were 6.33 and 6.67 MPa respectively,which met the requirements as foundation filler and building materials.The microscopic tests showed that the agglomeration was enhanced and the porosities of the solidified specimens were reduced with increase in the hydantoin epoxy resin content,which could greatly enhance the strength of solidified specimens.展开更多
A theoretical study is carried out on Gaunt＇s palladium-catalyzed selective C（sp3）-H activation of unprotected aliphatic amines. In this reaction, the methyl group is proposed to be activated through a four-membere...A theoretical study is carried out on Gaunt＇s palladium-catalyzed selective C（sp3）-H activation of unprotected aliphatic amines. In this reaction, the methyl group is proposed to be activated through a four-membered cyclometallation pathway even though an ethyl group is present in the substrate. Our calculation shows that the methyl and ethyl activation processes proceed in nitrogen-atom-directed pathway rather than carbonyl-directed one. More important, methyl activation is more favorable than ethyl activation with nitrogen atom as the directing group. Further studies on the structural parameters show that the lactone structure in cyclic substrate is the origin of the selective methyl activation. When the lactone moiety is changed to ketone, ether or alkyl, the selectivity could be reversed so that the ethyl activation becomes more favorable. This result validates the pro- oosal that lactone structure is key to selective methyl activation.展开更多
基金financial support from the National Natural Science Foundation of China (Nos. 41972282, 41807253)the Natural Science Foundation of Hunan Province, China (No. 2021JJ30804)the Research Fund Program from Yunnan Diqing Nonferrous Metal Co., Ltd., China (No. DQYS-ZYB-09-(2021)001)
文摘Based on the strength and microstructure tests,the effects of the hydantoin epoxy resin content and curing time on the mechanical properties and microstructure of copper tailings specimens were studied.The results showed that the strength of the solidified specimens was increased to 20.84 MPa with 30 wt.%addition of hydantoin epoxy resin.When the specimens with 10%hydantoin epoxy resin were cured for 7 and 14 d,the strengths were 6.33 and 6.67 MPa respectively,which met the requirements as foundation filler and building materials.The microscopic tests showed that the agglomeration was enhanced and the porosities of the solidified specimens were reduced with increase in the hydantoin epoxy resin content,which could greatly enhance the strength of solidified specimens.
基金supported by the National Natural Science Foundation of China(21325208,21172209,21361140372,21202006)the National Basic Research Program of China(2012CB215306)+2 种基金Financial Resources Federal Credit Union(WK2060190025,WK2060190040,FRF-TP-14-015A2)Chinese Academy of Sciences(KJCX2-EW-J02)Program for Changjiang Scholars and Innovative Research Team and the supercomputer center of Shanghai and USTC
文摘A theoretical study is carried out on Gaunt＇s palladium-catalyzed selective C（sp3）-H activation of unprotected aliphatic amines. In this reaction, the methyl group is proposed to be activated through a four-membered cyclometallation pathway even though an ethyl group is present in the substrate. Our calculation shows that the methyl and ethyl activation processes proceed in nitrogen-atom-directed pathway rather than carbonyl-directed one. More important, methyl activation is more favorable than ethyl activation with nitrogen atom as the directing group. Further studies on the structural parameters show that the lactone structure in cyclic substrate is the origin of the selective methyl activation. When the lactone moiety is changed to ketone, ether or alkyl, the selectivity could be reversed so that the ethyl activation becomes more favorable. This result validates the pro- oosal that lactone structure is key to selective methyl activation.
