Nitrogen-doped carbon materials with vacancies/defects have been developed as highly efficient ORR electrocatalysts but with poor activity for OER,which limits their application in rechargeable metal-air batteries.Fil...Nitrogen-doped carbon materials with vacancies/defects have been developed as highly efficient ORR electrocatalysts but with poor activity for OER,which limits their application in rechargeable metal-air batteries.Filling the vacancies/defects with heteroatoms is expected to be an effective strategy to obtain surprising catalytic activities and improve their stability especially under the strongly oxidizing conditions during the OER process.Herein,we successfully transformed the defect-rich 3 D carbon nanosheets(DCN)into a bifunctional ORR/OER electrocatalyst(DCN-M)by utilizing the in-situ generated vacancies to capture metal cations via a modified salt-sealed strategy.By varying the metal(Fe,Ni)content,the captured metal cations in DCN-M existed in different chemical states,i.e.,metal atoms were stabilized by CàN bonds at low metal contents,while at high metal contents,bimetal particles were covered by graphene layers,taking responsibility for catalyzing the ORR and OER,respectively.In addition,the in-situ formed graphene layers with an interconnected structure facilitate the electron transport during the reactions.The Janus-feature of DCN-M in structures ensures superior bifunctional activity and good stability towards ORR/OER for the rechargeable Zn-air battery.This work provides an effective strategy to design multifunctional electrocatalysts by heteroatom filling into vacancies of carbon materials.展开更多
In lost foam casting(LFC)the foam pattern is the key criterion,and the filling process is crucialto ensure the high quality of the foam pattern.Filling which lacks uniformity and denseness will cause variousdefects an...In lost foam casting(LFC)the foam pattern is the key criterion,and the filling process is crucialto ensure the high quality of the foam pattern.Filling which lacks uniformity and denseness will cause variousdefects and affect the surface quality of the casting.The influential factors of the filling process are realized in thisresearch.Optimization of the filling process,enhancement of efficiency,decrease of waste,etc.,are obtained bythe numerical simulation of the filling process using a computer.The equations governing the dense gas-solid two-phase flow are established,and the physical significanceof each equation is discussed.The Euler/Lagrange numerical model is used to simulate the fluid dynamiccharacteristics of the dense two-phase flow during the mould filling process in lost foam casting.The experimentsand numerical results showed that this method can be a very promising tool in the mould filling simulation of beads’movement.展开更多
A model was established based on the combination of the equation of continuity, the equation of conservation of momentum and the equation of general energy to describe the filling and solidification of TiAl melt by pe...A model was established based on the combination of the equation of continuity, the equation of conservation of momentum and the equation of general energy to describe the filling and solidification of TiAl melt by permanent mold centrifugal casting. The model was solved numerically and the filling and solidification processes in the centrifugal field were discussed. The results indicate that the centrifugal field essentially influences the filling and solidification processes of TiAl melt. The melt will first fill the cavity along the back boundary until it reaches the end. After the end is fully filled, the whole cavity will be filled gradually by the way that free surface of the melt moves towards the entrance, hence the entrance is the last part to be filled. Furthermore, the mechanism by which internal defects can be formed in centrifugally cast TiAl components were interpreted.展开更多
Objective To discuss repairing effects of articular cartilage defects by nitric oxide synthase inhibitor (S methylisothiourea, SMT), and explore the role of nitric oxide in cartilage repair. Methods Full-thickness def...Objective To discuss repairing effects of articular cartilage defects by nitric oxide synthase inhibitor (S methylisothiourea, SMT), and explore the role of nitric oxide in cartilage repair. Methods Full-thickness defects of cartilage were created in the intercondylar trochlear groove of femur of thirty-six adult New Zealand white rabbits, and were divided into three gorups. Twenty-four defects were untreated as the control, twenty-four were filled with fibrin glue and impregnated with rhBMP AS rhBMP group, the rest twenty-four were filled with fibrin glue and impregnated with rhBMP, and hypodermic injection with SMT as SMT group. The animals were sacrified at sixteen weeks postoperatively, and the gross appearance of the defect was estimated. The repair tissue was examined histologically and was evaluated according to the grading scale of histology. The amount of released NO and the activities of nitric oxide synthase(NOS) were examined by chemical colorimetry. The distribution of type-Ⅰ , Ⅱ展开更多
基金financially supported by the National Natural Science Foundation of China(21776146)the Key Research and Development Programme of Shandong Province(2019JZZY010905)the Taishan Scholar Program of Shandong Province(ts201712046)。
文摘Nitrogen-doped carbon materials with vacancies/defects have been developed as highly efficient ORR electrocatalysts but with poor activity for OER,which limits their application in rechargeable metal-air batteries.Filling the vacancies/defects with heteroatoms is expected to be an effective strategy to obtain surprising catalytic activities and improve their stability especially under the strongly oxidizing conditions during the OER process.Herein,we successfully transformed the defect-rich 3 D carbon nanosheets(DCN)into a bifunctional ORR/OER electrocatalyst(DCN-M)by utilizing the in-situ generated vacancies to capture metal cations via a modified salt-sealed strategy.By varying the metal(Fe,Ni)content,the captured metal cations in DCN-M existed in different chemical states,i.e.,metal atoms were stabilized by CàN bonds at low metal contents,while at high metal contents,bimetal particles were covered by graphene layers,taking responsibility for catalyzing the ORR and OER,respectively.In addition,the in-situ formed graphene layers with an interconnected structure facilitate the electron transport during the reactions.The Janus-feature of DCN-M in structures ensures superior bifunctional activity and good stability towards ORR/OER for the rechargeable Zn-air battery.This work provides an effective strategy to design multifunctional electrocatalysts by heteroatom filling into vacancies of carbon materials.
基金The National High Technology Research and Development Program of China(863Program)(2006AA04Z140)The National Natural Science Foundation of China(NSFC)(50605024)
文摘In lost foam casting(LFC)the foam pattern is the key criterion,and the filling process is crucialto ensure the high quality of the foam pattern.Filling which lacks uniformity and denseness will cause variousdefects and affect the surface quality of the casting.The influential factors of the filling process are realized in thisresearch.Optimization of the filling process,enhancement of efficiency,decrease of waste,etc.,are obtained bythe numerical simulation of the filling process using a computer.The equations governing the dense gas-solid two-phase flow are established,and the physical significanceof each equation is discussed.The Euler/Lagrange numerical model is used to simulate the fluid dynamiccharacteristics of the dense two-phase flow during the mould filling process in lost foam casting.The experimentsand numerical results showed that this method can be a very promising tool in the mould filling simulation of beads’movement.
基金Project(4040-304019) supported by Shandong University of Technology of China
文摘A model was established based on the combination of the equation of continuity, the equation of conservation of momentum and the equation of general energy to describe the filling and solidification of TiAl melt by permanent mold centrifugal casting. The model was solved numerically and the filling and solidification processes in the centrifugal field were discussed. The results indicate that the centrifugal field essentially influences the filling and solidification processes of TiAl melt. The melt will first fill the cavity along the back boundary until it reaches the end. After the end is fully filled, the whole cavity will be filled gradually by the way that free surface of the melt moves towards the entrance, hence the entrance is the last part to be filled. Furthermore, the mechanism by which internal defects can be formed in centrifugally cast TiAl components were interpreted.
文摘Objective To discuss repairing effects of articular cartilage defects by nitric oxide synthase inhibitor (S methylisothiourea, SMT), and explore the role of nitric oxide in cartilage repair. Methods Full-thickness defects of cartilage were created in the intercondylar trochlear groove of femur of thirty-six adult New Zealand white rabbits, and were divided into three gorups. Twenty-four defects were untreated as the control, twenty-four were filled with fibrin glue and impregnated with rhBMP AS rhBMP group, the rest twenty-four were filled with fibrin glue and impregnated with rhBMP, and hypodermic injection with SMT as SMT group. The animals were sacrified at sixteen weeks postoperatively, and the gross appearance of the defect was estimated. The repair tissue was examined histologically and was evaluated according to the grading scale of histology. The amount of released NO and the activities of nitric oxide synthase(NOS) were examined by chemical colorimetry. The distribution of type-Ⅰ , Ⅱ
