A solid state synthesis of ultrafine/nanocrystalline WC-10Co composite powders was reported from WO3 , Co3O4 and carbon powders after reduction and carburization at relatively low temperatures in a short time under pu...A solid state synthesis of ultrafine/nanocrystalline WC-10Co composite powders was reported from WO3 , Co3O4 and carbon powders after reduction and carburization at relatively low temperatures in a short time under pure H2 atmosphere. The effects of ball milling time and reaction temperature on the preparation of ultrafine/nanocrystalline WC-Co composite powders were studied using X-ray diffraction and scanning electron microscope (SEM). The results show that fine mixed oxide powders (WO3 , Co3O4 and carbon powders) can be obtained by long time ball milling. Increasing the reaction temperature can decrease the formation of Co3W3C and graphite phases and increase the WC crystallite size. Long-time ball milling and high reaction temperature are favorable to obtain fine and pure composite powders consisting of nanocrystalline WC from WO3 , Co3O4 and carbon powders.展开更多
A novel chemical liquid reduction process was employed to prepare nanosized Mo-Cu powders. The precipitates were first obtained by adding ammonium heptamolybdate （（NH4）6Mo7024·4H2O） solution into excess hydra...A novel chemical liquid reduction process was employed to prepare nanosized Mo-Cu powders. The precipitates were first obtained by adding ammonium heptamolybdate （（NH4）6Mo7024·4H2O） solution into excess hydrazine hydrate solution, and then mixed the copper chloride solution. The precipitates were subsequently washed, dried, followed by reducing in H2 atmosphere to convert into Mo-Cu composite powders. The composition, morphology and particle size of the Mo-Cu composite powders were characterized by the XRD, SEM and TEM. The effects of the chemical reaction temperature and the magnetic stirring on the morphology of the Mo-Cu powders were also studied. The results show that Mo-Cu powders produced by the chemical liquid reduction process are nearly spherical shape and dispersive distribution state, with particle size ranging from 50 to 100 nm. The chemical reaction temperature and magnetic stirring will change the particle feature of the powders. Because of the Cu3M0209, the reduction process in H2 is the one-stage reduction from the precipitates to the Mo-Cu composite powders.展开更多
MXene, a new type of two-dimensional layered transition metal carbide material differing from graphene, demonstrates intriguing chemical/physical properties and wide applications in recent years. Here, the preparation...MXene, a new type of two-dimensional layered transition metal carbide material differing from graphene, demonstrates intriguing chemical/physical properties and wide applications in recent years. Here, the preparation of the self-assembled MXene-gold nanoparticles （MXene@AuNPs） nanocomposites with tunable sizes is reported. The nano- composites are obtained via the self-reduction reactions of MXene material in a HAuCI4 solution at room temperature. The sizes of the Au particles can be well-controlled by reg- ulating the self-reduction reaction time. They can greatly in- fluence the catalytic behaviors of the MXene@AuNPs composites. MXene@AuNPs composites with optimized re- duction time show high catalytic performances and good cycle stability for model catalytic reactions of nRro-compounds, such as 2-nitrophenol and 4-nitrophenol. This work demon- strates a new approach for the preparation of tunable MXene- based self-assembled composites.展开更多
基金Projects(50823006, 51021063, 51271152) supported by the National Natural Science Foundation of ChinaProject(NCET-10-0842)supported by the Program for New Century Excellent Talents in Universities of China
文摘A solid state synthesis of ultrafine/nanocrystalline WC-10Co composite powders was reported from WO3 , Co3O4 and carbon powders after reduction and carburization at relatively low temperatures in a short time under pure H2 atmosphere. The effects of ball milling time and reaction temperature on the preparation of ultrafine/nanocrystalline WC-Co composite powders were studied using X-ray diffraction and scanning electron microscope (SEM). The results show that fine mixed oxide powders (WO3 , Co3O4 and carbon powders) can be obtained by long time ball milling. Increasing the reaction temperature can decrease the formation of Co3W3C and graphite phases and increase the WC crystallite size. Long-time ball milling and high reaction temperature are favorable to obtain fine and pure composite powders consisting of nanocrystalline WC from WO3 , Co3O4 and carbon powders.
基金Project(51274246) supported by the National Natural Science Foundation of China
文摘A novel chemical liquid reduction process was employed to prepare nanosized Mo-Cu powders. The precipitates were first obtained by adding ammonium heptamolybdate （（NH4）6Mo7024·4H2O） solution into excess hydrazine hydrate solution, and then mixed the copper chloride solution. The precipitates were subsequently washed, dried, followed by reducing in H2 atmosphere to convert into Mo-Cu composite powders. The composition, morphology and particle size of the Mo-Cu composite powders were characterized by the XRD, SEM and TEM. The effects of the chemical reaction temperature and the magnetic stirring on the morphology of the Mo-Cu powders were also studied. The results show that Mo-Cu powders produced by the chemical liquid reduction process are nearly spherical shape and dispersive distribution state, with particle size ranging from 50 to 100 nm. The chemical reaction temperature and magnetic stirring will change the particle feature of the powders. Because of the Cu3M0209, the reduction process in H2 is the one-stage reduction from the precipitates to the Mo-Cu composite powders.
基金supported by the National Natural Science Foundation of China (21473153 and 51771162)Support Program for the Top Young Talents of Hebei Province, China Postdoctoral Science Foundation (2015M580214)the Scientific and Technological Research and Development Program of Qinhuangdao City (201701B004)
文摘MXene, a new type of two-dimensional layered transition metal carbide material differing from graphene, demonstrates intriguing chemical/physical properties and wide applications in recent years. Here, the preparation of the self-assembled MXene-gold nanoparticles （MXene@AuNPs） nanocomposites with tunable sizes is reported. The nano- composites are obtained via the self-reduction reactions of MXene material in a HAuCI4 solution at room temperature. The sizes of the Au particles can be well-controlled by reg- ulating the self-reduction reaction time. They can greatly in- fluence the catalytic behaviors of the MXene@AuNPs composites. MXene@AuNPs composites with optimized re- duction time show high catalytic performances and good cycle stability for model catalytic reactions of nRro-compounds, such as 2-nitrophenol and 4-nitrophenol. This work demon- strates a new approach for the preparation of tunable MXene- based self-assembled composites.
