Polyvinylidene fluoride/lead zirconate titanate(PVDF/PZT)composite films have been prepared by direct ink writing and the effect of PZT content on crystallization behavior and electrical properties of film were system...Polyvinylidene fluoride/lead zirconate titanate(PVDF/PZT)composite films have been prepared by direct ink writing and the effect of PZT content on crystallization behavior and electrical properties of film were systematically investigated.The composite films were characterized by scanning electron microscope(SEM),X-ray diffractometer(XRD),Flourier transform infrared spectroscope(FTIR)and differential scanning calorimeter(DSC).The results show that,surface modified PZT powder(PZT@PDA)is successfully coated by polydopamine(PDA),resulting in a large number of polar groups that interact with the-CF_(2)-groups in PVDF,inducing the generation of polarβphase due to hydrogen bonding formed in the interaction.Theβphase content in composite film increases with increasing PZT@PDA content,up to 28.09%as with 5 wt.%PZT@PDA.PZT@PDA plays a role of nucleating agent to promote the generation of polar phases in the film and also acts as an impurity hindering the growth of nuclei to reduce crystallinity.Moreover,the presence of PZT@PDA in interfaces provides more sites for the occurrence of interfacial polarization and thus improving the electrical properties of films.The composite film with 5 wt.%PZT@PDA possesses the highest dielectric constant(8.61)and residual polarization value(0.6803μC/cm^(2)).展开更多
ZnO-Bi2O3-based varistor ceramics doped with Yb2O3 in the range from 0 to 0.4% （molar fraction） were obtained by a solid reaction route. The X-ray diffractometry （XRD） and scanning electron microscopy （SEM） were...ZnO-Bi2O3-based varistor ceramics doped with Yb2O3 in the range from 0 to 0.4% （molar fraction） were obtained by a solid reaction route. The X-ray diffractometry （XRD） and scanning electron microscopy （SEM） were applied to characterize the phases and microstructure of the varistor ceramics, and a DC parameter instrument for varistor ceramics was applied to investigate their electrical properties and V-I characteristics. The XRD analysis of the samples shows that the ZnO phase, Bi2O3 phase, ZnTSbaOl2-type spinel phase and Zn2Bi3Sb3O14-type pyrochlore are present, and the Yb2O3 phases and Sb2O4 phases are found in varistor ceramics with increasing amounts of Yb2O3. The average size of ZnO grain firstly increases and then decreases with the increase of Yb2O3 content. The result also shows that the threshold voltage is between 656 V/nun and 1 232 V/mm, the nonlinear coefficient is in the range of 14.1-22.3, and the leakage current is between 0.60 μA and 19.6 μA. The 0.20% Yb2O3-added ZnO-Bi2O3-based varistor ceramics sintered at 900 ℃ have the best electrical characteristics.展开更多
Microstructure and electrical properties of La2 O3-doped ZnO-Bi2 O3 thin films prepared by sol–gel process have been investigated.X-ray diffraction shows that most diffraction peaks of ZnO are equal,and the crystals ...Microstructure and electrical properties of La2 O3-doped ZnO-Bi2 O3 thin films prepared by sol–gel process have been investigated.X-ray diffraction shows that most diffraction peaks of ZnO are equal,and the crystals of ZnO grow well.Scanning electron microscopy and atomic force microscopy results indicate that the samples have a good structure and lower surface roughness.The nonlinear V–I characteristics of the films show that La2 O3 develops the electrical properties largely and the best doped content is 0.3% lanthanum ion,with the leakage current of 0.25 mA,the threshold field of 150 V/mm and the nonlinear coefficient of 4.0 in detail.展开更多
The monitoring of cutting force in a vibration cutting process has a great significance in the popularization of ultrasonic vibration cutting technology. A new monitoring method of which the cutting force of ultrasoni...The monitoring of cutting force in a vibration cutting process has a great significance in the popularization of ultrasonic vibration cutting technology. A new monitoring method of which the cutting force of ultrasonic elliptic vibration cutting is monitored using the electrical properties of transducer was proposed by studying on the relationship of cutting force, transducer electric impedance and load. A measurement system was designed for the electrical properties of transducer. The feasibility of cutting force monitoring method based on the electrical properties of piezoelectric transducer was proved by the cutting experiments.展开更多
Electrical steel sheets with 6.5%(mas fraction) Si with good shapes and superior magnetic inductions were successfully produced by a specially designed processing route including ingot casting, hot rolling and warm ro...Electrical steel sheets with 6.5%(mas fraction) Si with good shapes and superior magnetic inductions were successfully produced by a specially designed processing route including ingot casting, hot rolling and warm rolling both with interpass thermal treatment, and final annealing. The sheets were of 0.2 mm and 0.3 mm thick over 140 mm width. A detailed study of the microstructural and textural evolutions from the hot rolling to annealing was carried out by optical microscopy, X-ray diffraction and electron backscattered diffraction. The hot rolled sheet characterized by near-equiaxed grains was dominated by the mixture of <001>//ND fiber(λ-fiber), <110>//RD fiber(α-fiber) and <111>//ND fiber(γ-fiber) textures owing to the partial recrystallization and strain induced boundary migration(SIBM) during the hot rolling interpass thermal treatment. The static recovery and SIBM during the warm rolling interpass thermal treatment result in large and elongated warm rolling grains. The warm rolling texture is dominated by obvious λ, Goss and strong γ-fiber textures. The application of the interpass thermal treatment during hot and warm rolling significantly enhances the impact of SIBM during annealing, which is responsible for the formation of the moderate λ-fiber, some near-λ fiber texture components and the obviously weakened γ-fiber texture in the annealed sheet, leading to a higher magnetic induction compared to the commercially produced 6.5% Si steel by chemical vapor deposition(CVD).展开更多
Due to their outstanding electrical contact properties,Cd-containing silver-matrix electrical contact materials can meet the requirements of high stability and long life for military defense and aerospace applications...Due to their outstanding electrical contact properties,Cd-containing silver-matrix electrical contact materials can meet the requirements of high stability and long life for military defense and aerospace applications.In order to further reduce the Cd content under the premise of meeting the high-performance requirements,in this study,high-purity intermediate Ti_(2)Cd powder of MAX phase(Ti_(2)CdC)was synthesized with a pressureless technique and then applied to reinforce the Ag matrix.The Cd content of the as-prepared Ag/Ti_(2)Cd composites was actually reduced by 38.31%compared with conventional Ag/CdO material.Based on the systematic study of the effect of heat treatment temperature on the physical phase,morphology,interface and comprehensive physical properties of Ag/Ti_(2)Cd composites,the preferred samples(heat treated at 400°C for 1 h)showed high density(97.77%),low resistivity(2.34μΩ·cm),moderate hardness(90.8HV),high tensile strength(189.9 MPa),and exhibited good electrical contact performance after 40000 cycles of arc discharging under severe conditions(DC 28 V/20 A).The results of microscopic morphological evolution,phase change and elemental distribution of the electrical contact surface show that the combination of high stability of Ti_(2)Cd reinforcing phase,good interfacial bonding with Ag matrix and improved melt pool viscosity in the primary stage of arc erosion,results in low and stable contact resistance(average value 13.20 mΩ)and welding force(average value 0.6 N),low fluctuation of static force(2.2-2.5 N).The decomposition and absorption energy of Ti_(2)Cd and the arc extinguishing effect of Cd vapor are the main reasons for the stable arcing energy and arcing time of electric contacts in the late stage of arc erosion.展开更多
Hexagonal boron nitride (h-BN) was added into polymer blends of methyl-vinyl-silicone rubber (MVQ) and ethylene-vinyl-acetate copolymer (EVA) to prepare thermally conductive and electrically insulating composites by m...Hexagonal boron nitride (h-BN) was added into polymer blends of methyl-vinyl-silicone rubber (MVQ) and ethylene-vinyl-acetate copolymer (EVA) to prepare thermally conductive and electrically insulating composites by melt processing method. According to Young’s equation, the wettability coefficient points out that the dispersion of h-BN in EVA is thermodynamically more favorable than in MVQ. The result of SEM showed that h-BN was selectively located in EVA. There existed double percolation effect in h-BN/MVQ/EVA ternary composites, which resulted in promoting for both mechanical properties and thermal conductivity. The thermal conductivity of h-BN/MVQ/EVA composites were related with h-BN content and EVA/MVQ ratio. When EVA content was 30 wt% in the matrix blend, the relatively increased rate of thermal conductivity of h-BN/MVQ/EVA composites was the highest. The tensile strength and the elongation at break were mainly related with the EVA content in polymer matrix. The increasing amount of EVA and h-BN in the composites resulted in a decrease in dielectric constant.展开更多
Engineering property of kaolin clay contaminated by diesel oil was studied through a series of laboratory experiments.Oil contents(mass fraction) of 4%,8%,12%,16% and 20% were selected to represent different contamina...Engineering property of kaolin clay contaminated by diesel oil was studied through a series of laboratory experiments.Oil contents(mass fraction) of 4%,8%,12%,16% and 20% were selected to represent different contamination degrees,and the soil specimens were manually prepared through mixing and static compaction method.Initial water content and dry density of the test kaolin clay were controlled at 10% and 1.58 g/cm^3,respectively.Test results indicate that since part of the diesel oil will be released from soil by evaporation,the real water content should be derived through calibration of the quasi water content obtained by traditional test method.As contamination degree of the kaolin clay increases,both liquid limit and plastic limit decrease,but there's only a slight increase for plasticity index.Swelling pressure of contaminated kaolin clay under confined condition will be lowered when oil-content gets higher.Unconfined compressive strength(UCS) of the oil-contaminated kaolin clay is influenced by not only oil content but also curing period.Increase of contamination degree will continually lower UCS of the kaolin clay specimen.In addition,electrical resistivity of the contaminated kaolin clay with given water content decreases with the increase of oil content.However,soil resistivity is in good relationship with oil content and UCS.Finally,oil content of 8% is found to be a critical value for engineering property of kaolin clay to transit from water-dominated towards oil-dominated characteristics.展开更多
In this study,the effect of welding parameters on the microstructure and mechanical properties of the dissimilar resistance spot welded DP1000–QP1180 joints was investigated.Heat affected zone(HAZ)width of QP1180 sid...In this study,the effect of welding parameters on the microstructure and mechanical properties of the dissimilar resistance spot welded DP1000–QP1180 joints was investigated.Heat affected zone(HAZ)width of QP1180 side was smaller than that of DP1000 side.HAZ width and indentation depth increased with increasing welding current and welding time.The nugget size increased with increasing welding current whereas it increased at lower currents and decreased at higher currents with increasing welding time.The lowest hardness was on the DP1000 side.On the QP1180 side,the center of HAZ had the peak hardness.With increasing welding current,hardness values throughout the weld zone decreased and the tensile shear load increased.At lower welding currents,the welding time did not affect the tensile shear load.Tensile elongation decreased with the increase of welding time,whereas there is no relationship between the welding current and elongation.The spot-welded joints having higher strength exhibited a more ductile fracture characteristic.展开更多
This work is aimed to study the effect of boron on wear resistance of Fe-Cr-B alloys containing different boron contents(0 wt%,5 wt%,7 wt%and 9 wt%)from room temperature(RT)to 800°C in order to explore their appl...This work is aimed to study the effect of boron on wear resistance of Fe-Cr-B alloys containing different boron contents(0 wt%,5 wt%,7 wt%and 9 wt%)from room temperature(RT)to 800°C in order to explore their applications as high-temperature wear resistant mechanical parts.Additionally,the wear mechanism of alloys is evaluated.The tribological properties of alloys are systematically studied by using a ball-on-disc tribometer at 10 N and 0.20 m/s from RT to 800°C sliding against Si3N4 ceramic ball.The boron element greatly improves the wear resistance of specimens as compared with that of unreinforced specimen.The friction coefficients of specimens decrease with increasing of testing temperature.The wear rates of Fe-Cr-B alloys decrease firstly and then raise with the increase of boron content.The specific wear rates of specimens with boron are 1/10 of the unreinforced specimen.Fe-21wt%Cr-7wt%B keeps the best tribological properties at high temperature.展开更多
The effect of surface roughness of aluminum oxide (95%) substrate on the properties of Ni-Cr alloy thin film is studied.The thin films are prepared on the substrates with different roughness by using magnetron sputter...The effect of surface roughness of aluminum oxide (95%) substrate on the properties of Ni-Cr alloy thin film is studied.The thin films are prepared on the substrates with different roughness by using magnetron sputtering.The micro-structure,adhesive and electrical properties of the thin films were investigated by using scanning electron microscopy,scratch method and four-probe method.The burst voltage and current of the thin film transducers with different substrates were measured according to D-optimization method.The results show that the particle size,structural defect,resistivity and adhesion strength of the thin film increase with the increase of the substrate roughness.The difference among the burst time of the samples with difference substrate roughness gradually decreases with the increase of stimulation amount.The burst time is approximate to 20 μs in the charging voltage of 37 V.展开更多
Mechanical properties and microstructure of multifunctional composites produced with palm kernel shell ash nano particle(PKSAnp)-A356 alloy composites was studied.The composites were produced using Double layer feedin...Mechanical properties and microstructure of multifunctional composites produced with palm kernel shell ash nano particle(PKSAnp)-A356 alloy composites was studied.The composites were produced using Double layer feeding stir casting method(DLF-SCM) by adding 1 wt%-4 wt.% PKSAnp.The microstructure,density,electrical and mechanical properties were determined.The results shows that there was a uniform distribution of the PKSAnp in A356 alloy.The mismatch at the interface between the PKSAnp and A356 alloy was 4.26%.Improvement of 30.47%,41.91%,49.52%,40.90% and 65.09% were obtained for hardness values,tensile,yield strength,%elongation and impact energy at 4 wt% PKASnp.The work has established that the developed composites can be used for multifunctional applications where combination of toughness and strength is vital.展开更多
基金Project(22020JJ4729)supported by the Natural Science Foundation of Hunan Province,China。
文摘Polyvinylidene fluoride/lead zirconate titanate(PVDF/PZT)composite films have been prepared by direct ink writing and the effect of PZT content on crystallization behavior and electrical properties of film were systematically investigated.The composite films were characterized by scanning electron microscope(SEM),X-ray diffractometer(XRD),Flourier transform infrared spectroscope(FTIR)and differential scanning calorimeter(DSC).The results show that,surface modified PZT powder(PZT@PDA)is successfully coated by polydopamine(PDA),resulting in a large number of polar groups that interact with the-CF_(2)-groups in PVDF,inducing the generation of polarβphase due to hydrogen bonding formed in the interaction.Theβphase content in composite film increases with increasing PZT@PDA content,up to 28.09%as with 5 wt.%PZT@PDA.PZT@PDA plays a role of nucleating agent to promote the generation of polar phases in the film and also acts as an impurity hindering the growth of nuclei to reduce crystallinity.Moreover,the presence of PZT@PDA in interfaces provides more sites for the occurrence of interfacial polarization and thus improving the electrical properties of films.The composite film with 5 wt.%PZT@PDA possesses the highest dielectric constant(8.61)and residual polarization value(0.6803μC/cm^(2)).
基金Project(BK2011243) supported by the Natural Science Foundation of Jiangsu Province,ChinaProject(2007DA10512711408) supported by the Visiting Scholarship of State Key Laboratory of Power Transmission Equipment & System Security and New Technology (Chongqing University),China+4 种基金Project(EIPE11204) supported by the State Key Laboratory of Electrical Insulation and Power Equipment,ChinaProject(KF201104) supported by the State Key Laboratory of New Ceramic and Fine Processing,ChinaProject(KFJJ201105) supported by the Opening Project of State Key Laboratory of Electronic Thin Films and Integrated Devices,ChinaProject(10KJD430002) supported by the Universities Natural Science Research Project of Jiangsu Province,ChinaProject(11JDG084) supported by the Research Foundation of Jiangsu University,China
文摘ZnO-Bi2O3-based varistor ceramics doped with Yb2O3 in the range from 0 to 0.4% （molar fraction） were obtained by a solid reaction route. The X-ray diffractometry （XRD） and scanning electron microscopy （SEM） were applied to characterize the phases and microstructure of the varistor ceramics, and a DC parameter instrument for varistor ceramics was applied to investigate their electrical properties and V-I characteristics. The XRD analysis of the samples shows that the ZnO phase, Bi2O3 phase, ZnTSbaOl2-type spinel phase and Zn2Bi3Sb3O14-type pyrochlore are present, and the Yb2O3 phases and Sb2O4 phases are found in varistor ceramics with increasing amounts of Yb2O3. The average size of ZnO grain firstly increases and then decreases with the increase of Yb2O3 content. The result also shows that the threshold voltage is between 656 V/nun and 1 232 V/mm, the nonlinear coefficient is in the range of 14.1-22.3, and the leakage current is between 0.60 μA and 19.6 μA. The 0.20% Yb2O3-added ZnO-Bi2O3-based varistor ceramics sintered at 900 ℃ have the best electrical characteristics.
基金Project(20123227120021)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of ChinaProject(BK2012156)supported by the Natural Science Foundation of Jiangsu Province,China+3 种基金Project(KFJJ201105)supported by the Opening Project of State Key Laboratory of Electronic Thin Films and Integrated Devices,ChinaProject(CJ20125001)supported by the Application Program for Basic Research of Changzhou,ChinaProject(13KJB430006)supported by the Universities Natural Science Research project of Jiangsu Province,ChinaProject supported by the Industrial Center of Jiangsu University Undergraduate Practice-Innovation Training Program,China
文摘Microstructure and electrical properties of La2 O3-doped ZnO-Bi2 O3 thin films prepared by sol–gel process have been investigated.X-ray diffraction shows that most diffraction peaks of ZnO are equal,and the crystals of ZnO grow well.Scanning electron microscopy and atomic force microscopy results indicate that the samples have a good structure and lower surface roughness.The nonlinear V–I characteristics of the films show that La2 O3 develops the electrical properties largely and the best doped content is 0.3% lanthanum ion,with the leakage current of 0.25 mA,the threshold field of 150 V/mm and the nonlinear coefficient of 4.0 in detail.
文摘The monitoring of cutting force in a vibration cutting process has a great significance in the popularization of ultrasonic vibration cutting technology. A new monitoring method of which the cutting force of ultrasonic elliptic vibration cutting is monitored using the electrical properties of transducer was proposed by studying on the relationship of cutting force, transducer electric impedance and load. A measurement system was designed for the electrical properties of transducer. The feasibility of cutting force monitoring method based on the electrical properties of piezoelectric transducer was proved by the cutting experiments.
基金Projects(51004035,51374002,50734001)supported by the National Natural Science Foundation of ChinaProject(2012BAE03B00)supported by the National Key Technology R&D Program,China+1 种基金Project(2012AA03A506)supported by the High-tech R&D Program,ChinaProject(N120407009)supported by the Fundamental Research Funds for the Central Universities,China
文摘Electrical steel sheets with 6.5%(mas fraction) Si with good shapes and superior magnetic inductions were successfully produced by a specially designed processing route including ingot casting, hot rolling and warm rolling both with interpass thermal treatment, and final annealing. The sheets were of 0.2 mm and 0.3 mm thick over 140 mm width. A detailed study of the microstructural and textural evolutions from the hot rolling to annealing was carried out by optical microscopy, X-ray diffraction and electron backscattered diffraction. The hot rolled sheet characterized by near-equiaxed grains was dominated by the mixture of <001>//ND fiber(λ-fiber), <110>//RD fiber(α-fiber) and <111>//ND fiber(γ-fiber) textures owing to the partial recrystallization and strain induced boundary migration(SIBM) during the hot rolling interpass thermal treatment. The static recovery and SIBM during the warm rolling interpass thermal treatment result in large and elongated warm rolling grains. The warm rolling texture is dominated by obvious λ, Goss and strong γ-fiber textures. The application of the interpass thermal treatment during hot and warm rolling significantly enhances the impact of SIBM during annealing, which is responsible for the formation of the moderate λ-fiber, some near-λ fiber texture components and the obviously weakened γ-fiber texture in the annealed sheet, leading to a higher magnetic induction compared to the commercially produced 6.5% Si steel by chemical vapor deposition(CVD).
基金This work was financially supported by the National Natural Science Foundation of China(52101064)Jiangsu Planned Projects for Postdoctoral Research Funds(2020Z158)Industry-University-Research Cooperation Projects(RH2000002728,RH2000002332,RH2100000263).
文摘Due to their outstanding electrical contact properties,Cd-containing silver-matrix electrical contact materials can meet the requirements of high stability and long life for military defense and aerospace applications.In order to further reduce the Cd content under the premise of meeting the high-performance requirements,in this study,high-purity intermediate Ti_(2)Cd powder of MAX phase(Ti_(2)CdC)was synthesized with a pressureless technique and then applied to reinforce the Ag matrix.The Cd content of the as-prepared Ag/Ti_(2)Cd composites was actually reduced by 38.31%compared with conventional Ag/CdO material.Based on the systematic study of the effect of heat treatment temperature on the physical phase,morphology,interface and comprehensive physical properties of Ag/Ti_(2)Cd composites,the preferred samples(heat treated at 400°C for 1 h)showed high density(97.77%),low resistivity(2.34μΩ·cm),moderate hardness(90.8HV),high tensile strength(189.9 MPa),and exhibited good electrical contact performance after 40000 cycles of arc discharging under severe conditions(DC 28 V/20 A).The results of microscopic morphological evolution,phase change and elemental distribution of the electrical contact surface show that the combination of high stability of Ti_(2)Cd reinforcing phase,good interfacial bonding with Ag matrix and improved melt pool viscosity in the primary stage of arc erosion,results in low and stable contact resistance(average value 13.20 mΩ)and welding force(average value 0.6 N),low fluctuation of static force(2.2-2.5 N).The decomposition and absorption energy of Ti_(2)Cd and the arc extinguishing effect of Cd vapor are the main reasons for the stable arcing energy and arcing time of electric contacts in the late stage of arc erosion.
文摘Hexagonal boron nitride (h-BN) was added into polymer blends of methyl-vinyl-silicone rubber (MVQ) and ethylene-vinyl-acetate copolymer (EVA) to prepare thermally conductive and electrically insulating composites by melt processing method. According to Young’s equation, the wettability coefficient points out that the dispersion of h-BN in EVA is thermodynamically more favorable than in MVQ. The result of SEM showed that h-BN was selectively located in EVA. There existed double percolation effect in h-BN/MVQ/EVA ternary composites, which resulted in promoting for both mechanical properties and thermal conductivity. The thermal conductivity of h-BN/MVQ/EVA composites were related with h-BN content and EVA/MVQ ratio. When EVA content was 30 wt% in the matrix blend, the relatively increased rate of thermal conductivity of h-BN/MVQ/EVA composites was the highest. The tensile strength and the elongation at break were mainly related with the EVA content in polymer matrix. The increasing amount of EVA and h-BN in the composites resulted in a decrease in dielectric constant.
基金Projects(41330641,41272311,41202192)supported by the National Natural Science Foundation of ChinaProject(BK2010060)supported by the Key Project of Natural Science Foundation of Jiangsu Province,China
文摘Engineering property of kaolin clay contaminated by diesel oil was studied through a series of laboratory experiments.Oil contents(mass fraction) of 4%,8%,12%,16% and 20% were selected to represent different contamination degrees,and the soil specimens were manually prepared through mixing and static compaction method.Initial water content and dry density of the test kaolin clay were controlled at 10% and 1.58 g/cm^3,respectively.Test results indicate that since part of the diesel oil will be released from soil by evaporation,the real water content should be derived through calibration of the quasi water content obtained by traditional test method.As contamination degree of the kaolin clay increases,both liquid limit and plastic limit decrease,but there's only a slight increase for plasticity index.Swelling pressure of contaminated kaolin clay under confined condition will be lowered when oil-content gets higher.Unconfined compressive strength(UCS) of the oil-contaminated kaolin clay is influenced by not only oil content but also curing period.Increase of contamination degree will continually lower UCS of the kaolin clay specimen.In addition,electrical resistivity of the contaminated kaolin clay with given water content decreases with the increase of oil content.However,soil resistivity is in good relationship with oil content and UCS.Finally,oil content of 8% is found to be a critical value for engineering property of kaolin clay to transit from water-dominated towards oil-dominated characteristics.
基金Project supported by Beycelik Gestamp Inc.,Turkey
文摘In this study,the effect of welding parameters on the microstructure and mechanical properties of the dissimilar resistance spot welded DP1000–QP1180 joints was investigated.Heat affected zone(HAZ)width of QP1180 side was smaller than that of DP1000 side.HAZ width and indentation depth increased with increasing welding current and welding time.The nugget size increased with increasing welding current whereas it increased at lower currents and decreased at higher currents with increasing welding time.The lowest hardness was on the DP1000 side.On the QP1180 side,the center of HAZ had the peak hardness.With increasing welding current,hardness values throughout the weld zone decreased and the tensile shear load increased.At lower welding currents,the welding time did not affect the tensile shear load.Tensile elongation decreased with the increase of welding time,whereas there is no relationship between the welding current and elongation.The spot-welded joints having higher strength exhibited a more ductile fracture characteristic.
基金Projects(51775365,51405329) supported by the National Natural Science Foundation of ChinaProject(2015M570239) supported by the China Postdoctoral Science Foundation
文摘This work is aimed to study the effect of boron on wear resistance of Fe-Cr-B alloys containing different boron contents(0 wt%,5 wt%,7 wt%and 9 wt%)from room temperature(RT)to 800°C in order to explore their applications as high-temperature wear resistant mechanical parts.Additionally,the wear mechanism of alloys is evaluated.The tribological properties of alloys are systematically studied by using a ball-on-disc tribometer at 10 N and 0.20 m/s from RT to 800°C sliding against Si3N4 ceramic ball.The boron element greatly improves the wear resistance of specimens as compared with that of unreinforced specimen.The friction coefficients of specimens decrease with increasing of testing temperature.The wear rates of Fe-Cr-B alloys decrease firstly and then raise with the increase of boron content.The specific wear rates of specimens with boron are 1/10 of the unreinforced specimen.Fe-21wt%Cr-7wt%B keeps the best tribological properties at high temperature.
文摘The effect of surface roughness of aluminum oxide (95%) substrate on the properties of Ni-Cr alloy thin film is studied.The thin films are prepared on the substrates with different roughness by using magnetron sputtering.The micro-structure,adhesive and electrical properties of the thin films were investigated by using scanning electron microscopy,scratch method and four-probe method.The burst voltage and current of the thin film transducers with different substrates were measured according to D-optimization method.The results show that the particle size,structural defect,resistivity and adhesion strength of the thin film increase with the increase of the substrate roughness.The difference among the burst time of the samples with difference substrate roughness gradually decreases with the increase of stimulation amount.The burst time is approximate to 20 μs in the charging voltage of 37 V.
基金The authors would like to acknowledge Tertiary Education Trust Fund(TETFund)Nigeria for providing financial aid for this project under the project number:TETFUND/DESS/UNI/NSUKKA/2017/RP/VOL.I.
文摘Mechanical properties and microstructure of multifunctional composites produced with palm kernel shell ash nano particle(PKSAnp)-A356 alloy composites was studied.The composites were produced using Double layer feeding stir casting method(DLF-SCM) by adding 1 wt%-4 wt.% PKSAnp.The microstructure,density,electrical and mechanical properties were determined.The results shows that there was a uniform distribution of the PKSAnp in A356 alloy.The mismatch at the interface between the PKSAnp and A356 alloy was 4.26%.Improvement of 30.47%,41.91%,49.52%,40.90% and 65.09% were obtained for hardness values,tensile,yield strength,%elongation and impact energy at 4 wt% PKASnp.The work has established that the developed composites can be used for multifunctional applications where combination of toughness and strength is vital.
