In this study,the effect of severe plastic deformation on the Mg grain refinement and recovery mechanism was investigated.Technical pure magnesium was deformed at room temperature by cycling extrusion-compression(CEC)...In this study,the effect of severe plastic deformation on the Mg grain refinement and recovery mechanism was investigated.Technical pure magnesium was deformed at room temperature by cycling extrusion-compression(CEC)process up to large deformation.Several steps of deformation have been used by applying 1,2 and 4 passes of CEC giving a total effective plastic strain ofε=3.1.Mechanical and structural properties of Mg in initial state and the states after successive steps of deformation were investigated.The mechanical properties were determined by microhardness and compression tests at room temperature.The structural investigations involved light microscope observations,electron back scattered diffraction and texture measurements by X-ray diffraction.It was found that the CEC process refines the grain size down to 6.4μm and reduces strong rolling texture components.However,only the first two passes had a strong effect on mechanical properties while a larger number of CEC cycles(above 4)led to failure of the samples with a small effect on hardness.This observation correlates with texture evolution indicating a more random orientation distribution that slows down the typical for hep metals rapid work hardening.It was found that the CEC process activated twin dynamic recrystallization in deformed Mg.This process led to the formation of new randomly oriented grains inside the twinned areas and as a consequence it reduced the strong rolling texture components.展开更多
The microstructure, phase consistence and microhardness of thermal sprayed coatings were investigated. The tungsten and chromium carbide coatings and also composite NiCrSiB coating were analyzed. The microstructure of...The microstructure, phase consistence and microhardness of thermal sprayed coatings were investigated. The tungsten and chromium carbide coatings and also composite NiCrSiB coating were analyzed. The microstructure of coatings were observed by using optical microscopy (MO), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Almost equiaxial carbide particles settled inside the surrounded material of coating were found. The cracks propagating thorough the particles and along boundaries between the particles and surrounded material were observed. This phenomenon was connected with the porosity of coatings. The decarburization process was detected in coatings by phase composition investigation using X-ray method. The decarburization process was the reason due to which beside initial Cr3C2 the Cr7C3 and Cr23C6 particles were found. In the tungsten coatings beside the initial WC carbides the W2Cones were found.展开更多
In this study the catalytic properties of gold nanoparticles in electro-oxidation process of glucose, were investigated, taking into account, an influence of catalyst composition. Graphene oxide was applied and for el...In this study the catalytic properties of gold nanoparticles in electro-oxidation process of glucose, were investigated, taking into account, an influence of catalyst composition. Graphene oxide was applied and for electro-oxidation studies of glucose, cyclic voltamperometry was used. It was found that an application of graphene oxide sheets during catalyst synthesis have an influence on gold nanoparticles (AuNPs) size and size distribution. It was confirmed that the application of composite catalyst consisting of graphane-AuNPs significantly changes electro-oxidation of glucose shifting the potential of oxidation to higher positive values and increasing oxidation current.展开更多
The article presents results of electrodeposition of Co-Mo Co-Mo-C alloys in a magnetic field characterized by low overvoltage of hydrogen evolution.Addition of molybdenum and carbon was to lower the values of overvol...The article presents results of electrodeposition of Co-Mo Co-Mo-C alloys in a magnetic field characterized by low overvoltage of hydrogen evolution.Addition of molybdenum and carbon was to lower the values of overvoltage of hydrogen evolution on cobalt.The influence of bath pH,bath composite,current density and magnetic field with different orientation on the deposits composition,structure and overpotential for hydrogen evolution reaction(HER) was determined.Electrocatalytic properties of the obtained alloy coatings within the range of hydrogen evolution were tested in a concentrated NaOH solution.The comparison of electrocatalytic properties of Co-Mo alloys with properties of Co-Mo-C ones enabled determining the influence of carbon presence in cathodic deposits on the overpotential values for hydrogen evolution.展开更多
基金The project was performed within the activity(11.11.180.653)of the Department of Materials Science and Non-Ferrous Metals Engineering at AGH-UST Krakow,Poland.
文摘In this study,the effect of severe plastic deformation on the Mg grain refinement and recovery mechanism was investigated.Technical pure magnesium was deformed at room temperature by cycling extrusion-compression(CEC)process up to large deformation.Several steps of deformation have been used by applying 1,2 and 4 passes of CEC giving a total effective plastic strain ofε=3.1.Mechanical and structural properties of Mg in initial state and the states after successive steps of deformation were investigated.The mechanical properties were determined by microhardness and compression tests at room temperature.The structural investigations involved light microscope observations,electron back scattered diffraction and texture measurements by X-ray diffraction.It was found that the CEC process refines the grain size down to 6.4μm and reduces strong rolling texture components.However,only the first two passes had a strong effect on mechanical properties while a larger number of CEC cycles(above 4)led to failure of the samples with a small effect on hardness.This observation correlates with texture evolution indicating a more random orientation distribution that slows down the typical for hep metals rapid work hardening.It was found that the CEC process activated twin dynamic recrystallization in deformed Mg.This process led to the formation of new randomly oriented grains inside the twinned areas and as a consequence it reduced the strong rolling texture components.
基金the Project No.POIR.01.01.01-00-0032/16 in the frame of Smart Growth Operational Programme 2014-2020 financed by the National Centre for Research and Development(Poland)。
基金financially supported by polish project NR15 0001 06the Ministry of Higher Education and Science/AGH University of Science and Technology,Krakow,Poland,grant number 11.11.180.255 is greatly acknowledged.
文摘The microstructure, phase consistence and microhardness of thermal sprayed coatings were investigated. The tungsten and chromium carbide coatings and also composite NiCrSiB coating were analyzed. The microstructure of coatings were observed by using optical microscopy (MO), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Almost equiaxial carbide particles settled inside the surrounded material of coating were found. The cracks propagating thorough the particles and along boundaries between the particles and surrounded material were observed. This phenomenon was connected with the porosity of coatings. The decarburization process was detected in coatings by phase composition investigation using X-ray method. The decarburization process was the reason due to which beside initial Cr3C2 the Cr7C3 and Cr23C6 particles were found. In the tungsten coatings beside the initial WC carbides the W2Cones were found.
基金The authors gratefully acknowledge for financial support from AGH University of Science and Technology(con-tract No.11.11.180.373.2011)and European Grant No.POIG.01.01.02.-00-015/09-00.
文摘In this study the catalytic properties of gold nanoparticles in electro-oxidation process of glucose, were investigated, taking into account, an influence of catalyst composition. Graphene oxide was applied and for electro-oxidation studies of glucose, cyclic voltamperometry was used. It was found that an application of graphene oxide sheets during catalyst synthesis have an influence on gold nanoparticles (AuNPs) size and size distribution. It was confirmed that the application of composite catalyst consisting of graphane-AuNPs significantly changes electro-oxidation of glucose shifting the potential of oxidation to higher positive values and increasing oxidation current.
基金Item Sponsored by Polish National Center of Science under grant 2011/01/N/ST5/05509 and 2011/01/D/ST5/05743
文摘The article presents results of electrodeposition of Co-Mo Co-Mo-C alloys in a magnetic field characterized by low overvoltage of hydrogen evolution.Addition of molybdenum and carbon was to lower the values of overvoltage of hydrogen evolution on cobalt.The influence of bath pH,bath composite,current density and magnetic field with different orientation on the deposits composition,structure and overpotential for hydrogen evolution reaction(HER) was determined.Electrocatalytic properties of the obtained alloy coatings within the range of hydrogen evolution were tested in a concentrated NaOH solution.The comparison of electrocatalytic properties of Co-Mo alloys with properties of Co-Mo-C ones enabled determining the influence of carbon presence in cathodic deposits on the overpotential values for hydrogen evolution.
