采用高能球磨法制备了用于热浸镀锌的纳米C eO2/Zn复合粉末,并利用X射线衍射(X-ray d iffraction,XRD)、X射线光电子能谱(X-ray photoe lectron spectroscopy,XPS)、透射电镜(T ransm iss ion e lectron m i-croscopy,TEM)、扫描电镜(Sc...采用高能球磨法制备了用于热浸镀锌的纳米C eO2/Zn复合粉末,并利用X射线衍射(X-ray d iffraction,XRD)、X射线光电子能谱(X-ray photoe lectron spectroscopy,XPS)、透射电镜(T ransm iss ion e lectron m i-croscopy,TEM)、扫描电镜(Scann ing e lectron m icroscopy,SEM)以及能谱分析(X-ray energy d ispers ive spec-trum,EDS)等方法,对复合粉末的显微结构、表面成分、晶粒大小、微观形貌以及元素分布进行了研究。结果表明,随着球磨时间的延长,纳米C eO2硬团聚体逐渐解聚,Zn晶粒不断细化,形成层片状复合粉末;球磨120 m in后纳米C eO2粒子分散良好,呈理想的单个均匀弥散分布状态包覆在Zn颗粒上形成近似球形的复合粒子,其粒径分布均匀。展开更多
Lighter and more powerful next generation vehicles and other rotary machinery demand bearings to operate in harsher conditions for higher efficiency,and the continuous development of advanced low-wear and friction mat...Lighter and more powerful next generation vehicles and other rotary machinery demand bearings to operate in harsher conditions for higher efficiency,and the continuous development of advanced low-wear and friction materials is thus becoming even more important to meet these requirements.New aluminium composites reinforced with high performance lubricate phases such as graphene nanoplatelets(GNPs)are very promising and have been vigorously investigated.By maintaining a low coefficient of friction(COF)and offering great strength against wear due to their self-lubricating capability,the solid lubricant like GNPs protect the bearing surface from wear damage and prevent change in metallurgical properties during temperature fluctuations.This paper first studies the high-temperature tribological performance of aluminium matrix composites reinforced with GNP,consolidated via powder metallurgy,then elucidates their tribological mechanism.We report that the best tribological performance is achieved by the composite containing 2.0 wt%GNP,with an extraordinarily low COF of 0.09 and a specific wear rate of 3.5×10^(−2)mm^(3)·N^(−1)·m^(−1),which represent 75%and 40%reduction respectively,against the plain aluminium consolidated under identical conditions.The in-track and out-of-track Raman analysis have confirmed the role of GNPs in creating a tribofilm on the counterpart surface which contributed to the excellent performance.展开更多
Pure Ni and its composites with different percentages of Ni-Cr nano-oxides were coated over carbon steel to assess the coating features and mechanical and corrosion behavior.A nano-oxide composite of Ni-Cr was first s...Pure Ni and its composites with different percentages of Ni-Cr nano-oxides were coated over carbon steel to assess the coating features and mechanical and corrosion behavior.A nano-oxide composite of Ni-Cr was first synthesized through chemical coprecipitation with uniform distribution constituents.Electrodeposition was employed to coat pure Ni and Ni-(Ni-Cr)oxides(10,20,30,40,and 50 g/L)on the steel sheets.Transmission electron microscope and field emission scanning electron microscope were adopted to examine the microstructure of powders and coatings,and X-ray diffraction analysis was employed to study the chemical composition.The microhardness,thickness,and wear resistance of the coatings were assessed,polarization and electrochemical impedance spectroscopy(EIS)tests were conducted to analyze the corrosion behavior,and the corresponding equivalent circuit was developed.Results showed flawless and crack-free coatings for all samples and uniform distribution of nano-oxides in the Ni matrix for the samples of 10-30 g/L.Agglomerated oxides were detected at high concentrations.Maximum microhardness(HV 661),thickness(116μm),and wear resistance of coatings were found at 30 g/L.A three-loop equivalent circuit corresponded satisfactorily to all EIS data.The corrosion resistance increased with the nano-oxide concentration of up to 30 g/L but decreased at 40 g/L.The sample of 50 g/L showed the best corrosion resistance.展开更多
Ammonium metatungstate and cobalt nitrate were mixed at the molecular level in distilled water and then spray-decomposed to CoWO_4/WO_3 nanocomposite powder.The particle morphology,crystalline size,forming course,chem...Ammonium metatungstate and cobalt nitrate were mixed at the molecular level in distilled water and then spray-decomposed to CoWO_4/WO_3 nanocomposite powder.The particle morphology,crystalline size,forming course,chemical composition and phase structure of the powder were studied by SEM,TEM,DTA-TG,IR and XRD,respectively.Results show that the powder is homogeneous,spherical and nano-aggregated.展开更多
WC- 10Co nanocomposite powder produced by spray pyrolysis-continuoas reduction and carbonization technology was used, and the vacuum sinteriag plus sinterhip process was cdopted to prepare ultrafine WCCo cemented carb...WC- 10Co nanocomposite powder produced by spray pyrolysis-continuoas reduction and carbonization technology was used, and the vacuum sinteriag plus sinterhip process was cdopted to prepare ultrafine WCCo cemented carbide. The microstructure, grain size, porosity, density, Rockwell A hardness （ HRA ）, transverse rupture strength （ TRS ） , saturated magnetization and coercivity force were studied. The experimental results show that average grain size of the sample prepared by vacuum sintering plas sinterhip technology was about 420 nm, transverse rupture strength was more than 3460 MPa, and Rockwell A hardness of sintered specimen was more than 92.5. Ultrafine WC- 10Co cemented carbide with high strength and high hardness is obtained.展开更多
The present study reports the formation of ultrafine hard particles of nanocomposite WC with different additions of ZrO2 powders (0.5 - 20 vol.%). The initial mixed powders of WC with the desired ZrO2 concentrations w...The present study reports the formation of ultrafine hard particles of nanocomposite WC with different additions of ZrO2 powders (0.5 - 20 vol.%). The initial mixed powders of WC with the desired ZrO2 concentrations were mechanically mixed for 360 ks (end-product) under argon gas atmosphere at room temperature, using high energy ball mill. The end-product consists of average grain size of about 17 nm in diameter. The obtained nanocomposite powders were consolidated into fully dense compact, using spark plasma sintering (SPS) technique in vacuum. The experimental results revealed that the consolidation step, which was conducted at 1673 K with uniaxial pressure ranging from 19.6 to 38.2 MPa for short time (0.18 ks), does not lead to dramatic grain growth in the powders so that the consolidated nanocomposite bulk objects maintain their nanocrystalline behavior, being fine grains with an average size of 63 nm in diameter. The relative densities of consolidated nanocomposite WC/ZrO2 materials increase from 99.1% for WC-0.5% ZrO2 to 99.93% for WC-20% ZrO2. The indentation fracture toughness of the composites can be tailored between 7.31 and 19.46 MPa/m1/2 by controlling the volume fraction of ZrO2 matrix from 0.5% to 20%. The results show that the Poisson’s ratio increased monotonically with increasing the ZrO2 concentrations to get a maximum value of 0.268 for WC-20% ZrO2. In the whole range of ZrO2 concentrations (0.5 - 20 vol.%), high hardness values (20.73 to 22.83 GPa) were achieved. The Young’s modulus tends to decrease with increasing the volume fraction of the ZrO2 matrix to reach a minimum value of 583.2 GPa for WC-20% ZrO2. These hard and tough WC/ZrO2 nanocomposites are proposed to be employed as higher abrasive-wear resistant materials.展开更多
Ag–CdO composites are still one of the most commonly used electrical contact materials in low-voltage applications owing to their excellent electrical and mechanical properties.Nevertheless,considering the restrictio...Ag–CdO composites are still one of the most commonly used electrical contact materials in low-voltage applications owing to their excellent electrical and mechanical properties.Nevertheless,considering the restriction on using Cd due to its toxicity,it is necessary to find alternative materials that can replace these composites.In this study,the synthesis of Ag-ZnO alloys from Ag-Zn solid solutions was investigated by hot mechanochemical processing.The hot mechanochemical processing was conducted in a modified attritor mill at 138℃under flowing O2 at 1200 cm3/min for 3.0 h.The microstructure and phase evolution were investigated using X-ray diffractometry,field emission gun scanning electron microscopy and transmission electron microscopy.The results suggest that it is possible to complete the oxidation of Ag-Zn solid solution by hot mechanochemical processing at a low temperature and short time.This novel synthesis route can produce Ag-ZnO composites with a homogeneous distribution of nanoscale ZnO precipitates,which is impossible to achieve using the conventional material processing methods.Considering the fact that the fundamental approach to improving electric contact material performance resides in obtaining uniform dispersion of the second-phase in the Ag matrix,this new processing route could open the possibility for Ag-ZnO composites to replace non-environmentally friendly Ag-CdO.展开更多
This study investigates the effect of graphene oxide(GO)on the mechanical and corrosion behavior,antibacterial performance,and cell response of Mg–Zn–Mn(MZM)nanocomposite.MZM/GO nanocomposites with different amounts...This study investigates the effect of graphene oxide(GO)on the mechanical and corrosion behavior,antibacterial performance,and cell response of Mg–Zn–Mn(MZM)nanocomposite.MZM/GO nanocomposites with different amounts of GO(i.e.,0.5 wt%,1.0 wt%,and1.5 wt%)were fabricated by the semi-powder metallurgy method.The influence of GO on the MZM nanocomposite was analyzed through the hardness,compressive,corrosion,antibacterial,and cytotoxicity tests.The experimental results showed that,with the increase in the amount of GO(0.5 wt%and 1.5 wt%),the hardness value,compressive strength,and antibacterial performance of the MZM nanocomposite increased,whereas the cell viability and osteogenesis level decreased after the addition of 1.5 wt%GO.Moreover,the electrochemical examination results showed that the corrosion behavior of the MZM alloy was significantly enhanced after encapsulation in 0.5 wt%GO.In summary,MZM nanocomposites reinforced with GO can be used for implant applications because of their antibacterial performance and mechanical property.展开更多
文摘采用高能球磨法制备了用于热浸镀锌的纳米C eO2/Zn复合粉末,并利用X射线衍射(X-ray d iffraction,XRD)、X射线光电子能谱(X-ray photoe lectron spectroscopy,XPS)、透射电镜(T ransm iss ion e lectron m i-croscopy,TEM)、扫描电镜(Scann ing e lectron m icroscopy,SEM)以及能谱分析(X-ray energy d ispers ive spec-trum,EDS)等方法,对复合粉末的显微结构、表面成分、晶粒大小、微观形貌以及元素分布进行了研究。结果表明,随着球磨时间的延长,纳米C eO2硬团聚体逐渐解聚,Zn晶粒不断细化,形成层片状复合粉末;球磨120 m in后纳米C eO2粒子分散良好,呈理想的单个均匀弥散分布状态包覆在Zn颗粒上形成近似球形的复合粒子,其粒径分布均匀。
基金supported by the“The Royal Society”(INF\PHD\180005).
文摘Lighter and more powerful next generation vehicles and other rotary machinery demand bearings to operate in harsher conditions for higher efficiency,and the continuous development of advanced low-wear and friction materials is thus becoming even more important to meet these requirements.New aluminium composites reinforced with high performance lubricate phases such as graphene nanoplatelets(GNPs)are very promising and have been vigorously investigated.By maintaining a low coefficient of friction(COF)and offering great strength against wear due to their self-lubricating capability,the solid lubricant like GNPs protect the bearing surface from wear damage and prevent change in metallurgical properties during temperature fluctuations.This paper first studies the high-temperature tribological performance of aluminium matrix composites reinforced with GNP,consolidated via powder metallurgy,then elucidates their tribological mechanism.We report that the best tribological performance is achieved by the composite containing 2.0 wt%GNP,with an extraordinarily low COF of 0.09 and a specific wear rate of 3.5×10^(−2)mm^(3)·N^(−1)·m^(−1),which represent 75%and 40%reduction respectively,against the plain aluminium consolidated under identical conditions.The in-track and out-of-track Raman analysis have confirmed the role of GNPs in creating a tribofilm on the counterpart surface which contributed to the excellent performance.
文摘Pure Ni and its composites with different percentages of Ni-Cr nano-oxides were coated over carbon steel to assess the coating features and mechanical and corrosion behavior.A nano-oxide composite of Ni-Cr was first synthesized through chemical coprecipitation with uniform distribution constituents.Electrodeposition was employed to coat pure Ni and Ni-(Ni-Cr)oxides(10,20,30,40,and 50 g/L)on the steel sheets.Transmission electron microscope and field emission scanning electron microscope were adopted to examine the microstructure of powders and coatings,and X-ray diffraction analysis was employed to study the chemical composition.The microhardness,thickness,and wear resistance of the coatings were assessed,polarization and electrochemical impedance spectroscopy(EIS)tests were conducted to analyze the corrosion behavior,and the corresponding equivalent circuit was developed.Results showed flawless and crack-free coatings for all samples and uniform distribution of nano-oxides in the Ni matrix for the samples of 10-30 g/L.Agglomerated oxides were detected at high concentrations.Maximum microhardness(HV 661),thickness(116μm),and wear resistance of coatings were found at 30 g/L.A three-loop equivalent circuit corresponded satisfactorily to all EIS data.The corrosion resistance increased with the nano-oxide concentration of up to 30 g/L but decreased at 40 g/L.The sample of 50 g/L showed the best corrosion resistance.
文摘Ammonium metatungstate and cobalt nitrate were mixed at the molecular level in distilled water and then spray-decomposed to CoWO_4/WO_3 nanocomposite powder.The particle morphology,crystalline size,forming course,chemical composition and phase structure of the powder were studied by SEM,TEM,DTA-TG,IR and XRD,respectively.Results show that the powder is homogeneous,spherical and nano-aggregated.
基金Funded by he National Natural Science Foundation of China(50502026) , Key Project for Science and Technology Developmentof Wuhan City (20041003068-04) ,andthe Key Project forthe Sci .&Tech. Research of Chinese Ministry of Education (105123)
文摘WC- 10Co nanocomposite powder produced by spray pyrolysis-continuoas reduction and carbonization technology was used, and the vacuum sinteriag plus sinterhip process was cdopted to prepare ultrafine WCCo cemented carbide. The microstructure, grain size, porosity, density, Rockwell A hardness （ HRA ）, transverse rupture strength （ TRS ） , saturated magnetization and coercivity force were studied. The experimental results show that average grain size of the sample prepared by vacuum sintering plas sinterhip technology was about 420 nm, transverse rupture strength was more than 3460 MPa, and Rockwell A hardness of sintered specimen was more than 92.5. Ultrafine WC- 10Co cemented carbide with high strength and high hardness is obtained.
文摘The present study reports the formation of ultrafine hard particles of nanocomposite WC with different additions of ZrO2 powders (0.5 - 20 vol.%). The initial mixed powders of WC with the desired ZrO2 concentrations were mechanically mixed for 360 ks (end-product) under argon gas atmosphere at room temperature, using high energy ball mill. The end-product consists of average grain size of about 17 nm in diameter. The obtained nanocomposite powders were consolidated into fully dense compact, using spark plasma sintering (SPS) technique in vacuum. The experimental results revealed that the consolidation step, which was conducted at 1673 K with uniaxial pressure ranging from 19.6 to 38.2 MPa for short time (0.18 ks), does not lead to dramatic grain growth in the powders so that the consolidated nanocomposite bulk objects maintain their nanocrystalline behavior, being fine grains with an average size of 63 nm in diameter. The relative densities of consolidated nanocomposite WC/ZrO2 materials increase from 99.1% for WC-0.5% ZrO2 to 99.93% for WC-20% ZrO2. The indentation fracture toughness of the composites can be tailored between 7.31 and 19.46 MPa/m1/2 by controlling the volume fraction of ZrO2 matrix from 0.5% to 20%. The results show that the Poisson’s ratio increased monotonically with increasing the ZrO2 concentrations to get a maximum value of 0.268 for WC-20% ZrO2. In the whole range of ZrO2 concentrations (0.5 - 20 vol.%), high hardness values (20.73 to 22.83 GPa) were achieved. The Young’s modulus tends to decrease with increasing the volume fraction of the ZrO2 matrix to reach a minimum value of 583.2 GPa for WC-20% ZrO2. These hard and tough WC/ZrO2 nanocomposites are proposed to be employed as higher abrasive-wear resistant materials.
基金financially supported by the FONDECYT(Project No.11100284)the Metallurgy Department of University of Atacama for the XRD and SEM analysis(Projects EQM130125 and EQUV 003)
文摘Ag–CdO composites are still one of the most commonly used electrical contact materials in low-voltage applications owing to their excellent electrical and mechanical properties.Nevertheless,considering the restriction on using Cd due to its toxicity,it is necessary to find alternative materials that can replace these composites.In this study,the synthesis of Ag-ZnO alloys from Ag-Zn solid solutions was investigated by hot mechanochemical processing.The hot mechanochemical processing was conducted in a modified attritor mill at 138℃under flowing O2 at 1200 cm3/min for 3.0 h.The microstructure and phase evolution were investigated using X-ray diffractometry,field emission gun scanning electron microscopy and transmission electron microscopy.The results suggest that it is possible to complete the oxidation of Ag-Zn solid solution by hot mechanochemical processing at a low temperature and short time.This novel synthesis route can produce Ag-ZnO composites with a homogeneous distribution of nanoscale ZnO precipitates,which is impossible to achieve using the conventional material processing methods.Considering the fact that the fundamental approach to improving electric contact material performance resides in obtaining uniform dispersion of the second-phase in the Ag matrix,this new processing route could open the possibility for Ag-ZnO composites to replace non-environmentally friendly Ag-CdO.
文摘This study investigates the effect of graphene oxide(GO)on the mechanical and corrosion behavior,antibacterial performance,and cell response of Mg–Zn–Mn(MZM)nanocomposite.MZM/GO nanocomposites with different amounts of GO(i.e.,0.5 wt%,1.0 wt%,and1.5 wt%)were fabricated by the semi-powder metallurgy method.The influence of GO on the MZM nanocomposite was analyzed through the hardness,compressive,corrosion,antibacterial,and cytotoxicity tests.The experimental results showed that,with the increase in the amount of GO(0.5 wt%and 1.5 wt%),the hardness value,compressive strength,and antibacterial performance of the MZM nanocomposite increased,whereas the cell viability and osteogenesis level decreased after the addition of 1.5 wt%GO.Moreover,the electrochemical examination results showed that the corrosion behavior of the MZM alloy was significantly enhanced after encapsulation in 0.5 wt%GO.In summary,MZM nanocomposites reinforced with GO can be used for implant applications because of their antibacterial performance and mechanical property.
