The effect of rare earths (RE) surface treatment of carbon fibers (CF) on tribological properties of CF reinforced polytetrafluoroethylene (PTFE) composites under oil-lubricated condition was investigated. Exper...The effect of rare earths (RE) surface treatment of carbon fibers (CF) on tribological properties of CF reinforced polytetrafluoroethylene (PTFE) composites under oil-lubricated condition was investigated. Experimental results revealed that RE treated CF reinforced PTFE (CF/PTFE) composite had the lowest friction coefficient and wear under various applied loads and sliding speeds compared with untreated and air-oxidated composites. X-ray photoelectron spectroscopy (XPS) study of carbon fiber surface showed that, after RE treatment, oxygen concentration increased obviously, and the amount of oxygen-containing groups on CF surfaces were largely increased. The increase in the amount of oxygen-containing groups enhanced interfacial adhesion between CF and PTFE matrix. With strong interfacial adhesion of the composite, stress could be effectively transmitted to carbon fibers; carbon fibers were strongly bonded with VITE matrix, and large scale rubbing-off of PTFE be prevented, therefore, tribological properties of the composite was improved.展开更多
In this work,surface modification of a Mg-4Sm-2Al-0.5Mn alloy with high current pulse electron beam(HCPEB)under different number of pulses were investigated.The evolution in microstructure,composition and phase compon...In this work,surface modification of a Mg-4Sm-2Al-0.5Mn alloy with high current pulse electron beam(HCPEB)under different number of pulses were investigated.The evolution in microstructure,composition and phase components and properties in the surface layer before and after HCPEB treatment were characterized.It was found that the Al 11 Sm 3 and Al 2 Sm phases in the surface layer were gradually dissolved during HCPEB treatment,leading to the formation of a chemical homogeneous melted layers.Besides,deformation bands were formed in the treated layer due to the thermal stress generated during treatment.After 15 pulses treatment,the surface hardness increases to the maximum value of about 62.2 HV,about 61.2%higher than that of the untreated state.Electrochemical results show that the 15 pulses treated sample presents the best corrosion resistance in the 3.5wt%NaCl water solution by showing the highest corrosion potential(E_(corr))of-1.339V SEC and the lowest corrosion current density(I_(corr))of 1.48×10^(-6)A·cm^(-2).The results prove that the surface properties of the Mg-4Sm-2Al-0.5Mn alloy can be significantly improved by the HCPEB treatments under proper conditions.展开更多
The behaviour of RE added into steel surface by laser rapid solidification processing(LRSP) and their effects on surface properties were studied. Experimental results show that RE can be added into steel surface layer...The behaviour of RE added into steel surface by laser rapid solidification processing(LRSP) and their effects on surface properties were studied. Experimental results show that RE can be added into steel surface layer by LRSP of RE containing coating. The RE in the steel surface can react with oxygen and sulphur, then be dissolved in the grains or grain boundaries, and form intermetallic compounds RE 2Fe 17 . The addition of RE by LRSP has very strong effects on the properties of steel surface.展开更多
Carbon fibers (CF) were surface treated with air-oxidation and rare earths (RE), respectively. The effect of RE surface treatment on tensile strength and tribological properties of CF reinforced polytetrafluoroeth...Carbon fibers (CF) were surface treated with air-oxidation and rare earths (RE), respectively. The effect of RE surface treatment on tensile strength and tribological properties of CF reinforced polytetrafluoroethylene (PTFE) composites was invest/gated. Experimental results revealed that RE was superior to air ox/dation in improving the tensile strength, elongation, and the tensile modulus of CF reinforced PTFE (CF/PTFE) composite. Compared to the untreated and air-oxidated CF/PTFE composite, the RE treated composite had the lowest friction coefficient and specific wear rate under a given applied load and reciprocating sliding frequency. The RE treatment effectively improved the interfacial adhesion between CF and PTFE. With strong interfacial coupling, the carbon fibers carried most of the load, and direct contact and adhesion between PTFE and the counterpart were reduced, accordingly the friction and wear properties of the composite were improved.展开更多
Carbon fibers (CFs) were surface treated with air-oxidation, rare earths (RE) after air-oxidation, and rare earths, respectively. Erichsen test was conducted to study the interfacial adhesion of PTFE composites fi...Carbon fibers (CFs) were surface treated with air-oxidation, rare earths (RE) after air-oxidation, and rare earths, respectively. Erichsen test was conducted to study the interfacial adhesion of PTFE composites filled with carbon fibers treated with different treatment methods. Tribological properties of the PTFE composites, sliding against GCr15 steel under water-lubricated condition, were investigated on a reciprocating ball-on-disk UMT-2MT tribometer. The worn surfaces of the composites were examined using scanning electron microscopy. Experimental results reveal that RE treatment is superior to air oxidation in promoting tribological properties of CF reinforced PTFE (CF/PTFE) composite. The friction and wear properties of PTFE composite filled with RE treated CF are the best of the PTFE composites. RE treatment is more effective than air oxidation to improve the tribological properties of CF/PTFE composite owing to the effective improvement of interfacial adhesion between carbon fibers and PTFE matrix.展开更多
Effects of RE and Al on the structure, impact toughness, hardness, and wear resistance of high chromium cast iron containing wolfram were investigated. The results show that without modification the volume fraction of...Effects of RE and Al on the structure, impact toughness, hardness, and wear resistance of high chromium cast iron containing wolfram were investigated. The results show that without modification the volume fraction of austenite is high and the carbide appears to be thick lath and the grain size is relatively large; proper modification using RE combined with Al can reduce volume fraction of residual austenite in the as-cast structure obviously, refine grain size of primary austenite notably, and make the morphology of carbide changing from thick lath to thin lath, rosette, and feather-like modification can also increase hardness, wear resistance and impact toughness of cast iron.展开更多
Surface-treated MmNi3.55Co0.75Mn0.4Al0.3 alloy as negative electrode material of nickel-metal hydride battery was employed to improve the high-rate dischargeability. Surface treatment was realized by dipping and stirr...Surface-treated MmNi3.55Co0.75Mn0.4Al0.3 alloy as negative electrode material of nickel-metal hydride battery was employed to improve the high-rate dischargeability. Surface treatment was realized by dipping and stirring the alloy into a HCl aqueous solution with various concentrations at room temperature. The microstructure of the alloy before and after surface treatment was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties before and after surface treatment were compared, and the alloy treated in 0.025 mol/L HCl solution showed the optimal high-rate dischargeability.展开更多
Study was made on the effect of surface modification on the behaviors of cerium oxide nanopowders.A surfactant-sodium dodecyl sulfate(C12H25SO4Na)was used to modify the surface of CeO2 powder particles.The unmodifie...Study was made on the effect of surface modification on the behaviors of cerium oxide nanopowders.A surfactant-sodium dodecyl sulfate(C12H25SO4Na)was used to modify the surface of CeO2 powder particles.The unmodified and modified CeO2 powders were characterized by using a powder comprehensive characteristic tester,laser particle size analyzer,specific surface area tester,X-ray diffraction tester,and a scanning electron microscope.The testing and analysis results showed that C12H25SO4Na surface modification might increase the flowability and dispersity,and decrease the specific surface area and agglomeration of CeO2 powders.The mechanism of the surface modification of CeO2 powder particles was also discussed.展开更多
Effect of ion nitriding modification on surface hardness, corrosion resistance and magnetostriction of (Tb0.3Dy0.7)Fe1.95 alloy was investigated. Results demonstrated that a 100-200 nm thick nitrided layer was forme...Effect of ion nitriding modification on surface hardness, corrosion resistance and magnetostriction of (Tb0.3Dy0.7)Fe1.95 alloy was investigated. Results demonstrated that a 100-200 nm thick nitrided layer was formed on the sample surface by ion nitriding treatment, which improved obviously surface hardness, wear, and corrosion resistance properties of (Tb0.3Dy0.7)Fe1.95 alloys. The surface hardness was increased from HV587 to HV622 after ion nitriding at 650 K for 6 h. Furthermore, ion nitriding treatment had almost no influence on mag- netostrictive performance as the nitrided layer was quite thin and the treatment temperature was not too high. The results might provide us a new approach for surface modification of (Tb0.3Dy0.7)Fe1.95 alloy.展开更多
The effects on abrasion resistance and the microstructure of GCr15 steel surface by the compound technology of permeating RE combined with laser melting modification was studied. The results show that after compound t...The effects on abrasion resistance and the microstructure of GCr15 steel surface by the compound technology of permeating RE combined with laser melting modification was studied. The results show that after compound treatment, the abrasion resistance of samples has been improved significantly and the weight loss has been reduced to 14% of blank sample; the microstructure has been denser and more uniform than that of untreated; meanwhile, the grain has been refined and the concentration gradients of the elements permeated have been decreased obviously.展开更多
The surface oxidation behavior of pressureless sintered Al2O3/SiC nanocomposite was studied from 1000 to 1400 ℃ for more than 10 h in air. Weight gain during the process of heat treatment was measured by TG analysis....The surface oxidation behavior of pressureless sintered Al2O3/SiC nanocomposite was studied from 1000 to 1400 ℃ for more than 10 h in air. Weight gain during the process of heat treatment was measured by TG analysis. Phase transformation and microstructure changes of these specimens due to oxidation were investigated with X-ray diffraction (XRD), SEM and EDX technology. Thermogravimetric analysis show that the weight gain as a result of oxidation of SiC become significant above 1200 ℃. In the range of 1000 - 1300 ℃, the SiC grits are usually coated with a layer of amorphous silica after oxidation. Above 1300 ℃, the amorphous silica reacted with alumina matrix and formed mullite or crystallized into cristobalite. The rate of oxidation depends on the formation of dense cristobalite film. Large amount of needle-like mullite and alumina crystals are formed on the surface after oxidation at 1400℃.展开更多
The latest progress and research status of laser cladding ceramic coating was summarized. Technique characteristics and influence factors of laser cladding technique were introduced. Laser cladding technique includes ...The latest progress and research status of laser cladding ceramic coating was summarized. Technique characteristics and influence factors of laser cladding technique were introduced. Laser cladding technique includes the mixing method and laser irradiation. The mixing method can be classified as pre-coating method and synchronization method. The technique parameters include size of facula, scanning speed, cladding sector and times, adding quantity of powder, thickness of coating and quantity of joint coating. The results show that proper technique parameters can be controlled in order to acquire high quality laser cladding coating. Strengthened effect mechanism of rare earth additive is concluded, and the main effects of rare earth additive are micro-alloying, purifying boundary, fining crystal grains, improving crystal boundary, restraining columnar crystal growing. The development of laser cladding ceramic coating research was discussed.展开更多
Titamum oxide coatings were formed on me titanium net surface by micro-arc oxidation (MAO) in Na3PO4 solution using an AC power supply. Then the titanium oxide coatings were treated by La (NO3)3 soaking to improve...Titamum oxide coatings were formed on me titanium net surface by micro-arc oxidation (MAO) in Na3PO4 solution using an AC power supply. Then the titanium oxide coatings were treated by La (NO3)3 soaking to improve the activity. The structures and photocatalytic ability of titanium oxide coatings before and after surface La (NO3)3 treatment were characterized and evaluated by XRD, SEM, EDX and photocatalytic decoloration of acid brilliant scarlet dye aqueous solution, respectively. The results show that the titanium oxide film is mainly consisted of anatase. After the La(NO3)3 treatment, the sodium ions on TiO2/ Ti film surface are replaced by lanthanum. It is found that the photocatalytic activity of the titanium oxide coatings is enhanced after La(NO3)3 treatment. When La(NO3)3 aqueous concenuration is 0.1 mol·L^-1 and soak time is 12 h, the TiO2/Ti films photocatalytic decoloration rate increases from 15% to 34.8%.展开更多
基金the National Natural Science Foundation of China (50275093)
文摘The effect of rare earths (RE) surface treatment of carbon fibers (CF) on tribological properties of CF reinforced polytetrafluoroethylene (PTFE) composites under oil-lubricated condition was investigated. Experimental results revealed that RE treated CF reinforced PTFE (CF/PTFE) composite had the lowest friction coefficient and wear under various applied loads and sliding speeds compared with untreated and air-oxidated composites. X-ray photoelectron spectroscopy (XPS) study of carbon fiber surface showed that, after RE treatment, oxygen concentration increased obviously, and the amount of oxygen-containing groups on CF surfaces were largely increased. The increase in the amount of oxygen-containing groups enhanced interfacial adhesion between CF and PTFE matrix. With strong interfacial adhesion of the composite, stress could be effectively transmitted to carbon fibers; carbon fibers were strongly bonded with VITE matrix, and large scale rubbing-off of PTFE be prevented, therefore, tribological properties of the composite was improved.
基金This work was supported by the National Natural Science Foundations of China(No.51271121,51471109).
文摘In this work,surface modification of a Mg-4Sm-2Al-0.5Mn alloy with high current pulse electron beam(HCPEB)under different number of pulses were investigated.The evolution in microstructure,composition and phase components and properties in the surface layer before and after HCPEB treatment were characterized.It was found that the Al 11 Sm 3 and Al 2 Sm phases in the surface layer were gradually dissolved during HCPEB treatment,leading to the formation of a chemical homogeneous melted layers.Besides,deformation bands were formed in the treated layer due to the thermal stress generated during treatment.After 15 pulses treatment,the surface hardness increases to the maximum value of about 62.2 HV,about 61.2%higher than that of the untreated state.Electrochemical results show that the 15 pulses treated sample presents the best corrosion resistance in the 3.5wt%NaCl water solution by showing the highest corrosion potential(E_(corr))of-1.339V SEC and the lowest corrosion current density(I_(corr))of 1.48×10^(-6)A·cm^(-2).The results prove that the surface properties of the Mg-4Sm-2Al-0.5Mn alloy can be significantly improved by the HCPEB treatments under proper conditions.
文摘The behaviour of RE added into steel surface by laser rapid solidification processing(LRSP) and their effects on surface properties were studied. Experimental results show that RE can be added into steel surface layer by LRSP of RE containing coating. The RE in the steel surface can react with oxygen and sulphur, then be dissolved in the grains or grain boundaries, and form intermetallic compounds RE 2Fe 17 . The addition of RE by LRSP has very strong effects on the properties of steel surface.
基金Project supported by the National Natural Science Foundation of China (50275093)
文摘Carbon fibers (CF) were surface treated with air-oxidation and rare earths (RE), respectively. The effect of RE surface treatment on tensile strength and tribological properties of CF reinforced polytetrafluoroethylene (PTFE) composites was invest/gated. Experimental results revealed that RE was superior to air ox/dation in improving the tensile strength, elongation, and the tensile modulus of CF reinforced PTFE (CF/PTFE) composite. Compared to the untreated and air-oxidated CF/PTFE composite, the RE treated composite had the lowest friction coefficient and specific wear rate under a given applied load and reciprocating sliding frequency. The RE treatment effectively improved the interfacial adhesion between CF and PTFE. With strong interfacial coupling, the carbon fibers carried most of the load, and direct contact and adhesion between PTFE and the counterpart were reduced, accordingly the friction and wear properties of the composite were improved.
基金Project supported bythe National Natural Science Foundation of China (50275093)
文摘Carbon fibers (CFs) were surface treated with air-oxidation, rare earths (RE) after air-oxidation, and rare earths, respectively. Erichsen test was conducted to study the interfacial adhesion of PTFE composites filled with carbon fibers treated with different treatment methods. Tribological properties of the PTFE composites, sliding against GCr15 steel under water-lubricated condition, were investigated on a reciprocating ball-on-disk UMT-2MT tribometer. The worn surfaces of the composites were examined using scanning electron microscopy. Experimental results reveal that RE treatment is superior to air oxidation in promoting tribological properties of CF reinforced PTFE (CF/PTFE) composite. The friction and wear properties of PTFE composite filled with RE treated CF are the best of the PTFE composites. RE treatment is more effective than air oxidation to improve the tribological properties of CF/PTFE composite owing to the effective improvement of interfacial adhesion between carbon fibers and PTFE matrix.
文摘Effects of RE and Al on the structure, impact toughness, hardness, and wear resistance of high chromium cast iron containing wolfram were investigated. The results show that without modification the volume fraction of austenite is high and the carbide appears to be thick lath and the grain size is relatively large; proper modification using RE combined with Al can reduce volume fraction of residual austenite in the as-cast structure obviously, refine grain size of primary austenite notably, and make the morphology of carbide changing from thick lath to thin lath, rosette, and feather-like modification can also increase hardness, wear resistance and impact toughness of cast iron.
基金supported by Hi-Tech Research and Development Program (863) of China (2006AA11A159)
文摘Surface-treated MmNi3.55Co0.75Mn0.4Al0.3 alloy as negative electrode material of nickel-metal hydride battery was employed to improve the high-rate dischargeability. Surface treatment was realized by dipping and stirring the alloy into a HCl aqueous solution with various concentrations at room temperature. The microstructure of the alloy before and after surface treatment was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties before and after surface treatment were compared, and the alloy treated in 0.025 mol/L HCl solution showed the optimal high-rate dischargeability.
基金Project supported by the National Key Basic Research Program(NKBRP20047CCA03900)National Natural Science Foundation of China(2056601)
文摘Study was made on the effect of surface modification on the behaviors of cerium oxide nanopowders.A surfactant-sodium dodecyl sulfate(C12H25SO4Na)was used to modify the surface of CeO2 powder particles.The unmodified and modified CeO2 powders were characterized by using a powder comprehensive characteristic tester,laser particle size analyzer,specific surface area tester,X-ray diffraction tester,and a scanning electron microscope.The testing and analysis results showed that C12H25SO4Na surface modification might increase the flowability and dispersity,and decrease the specific surface area and agglomeration of CeO2 powders.The mechanism of the surface modification of CeO2 powder particles was also discussed.
基金supported by National High-Tech R&D Program (2006AA03Z106)Beijing Natural Science Foundation (2062012)National Natural Science Foundation (50801006)
文摘Effect of ion nitriding modification on surface hardness, corrosion resistance and magnetostriction of (Tb0.3Dy0.7)Fe1.95 alloy was investigated. Results demonstrated that a 100-200 nm thick nitrided layer was formed on the sample surface by ion nitriding treatment, which improved obviously surface hardness, wear, and corrosion resistance properties of (Tb0.3Dy0.7)Fe1.95 alloys. The surface hardness was increased from HV587 to HV622 after ion nitriding at 650 K for 6 h. Furthermore, ion nitriding treatment had almost no influence on mag- netostrictive performance as the nitrided layer was quite thin and the treatment temperature was not too high. The results might provide us a new approach for surface modification of (Tb0.3Dy0.7)Fe1.95 alloy.
基金Supported by the Science Foundation of Harbin Institute of Technology
文摘The effects on abrasion resistance and the microstructure of GCr15 steel surface by the compound technology of permeating RE combined with laser melting modification was studied. The results show that after compound treatment, the abrasion resistance of samples has been improved significantly and the weight loss has been reduced to 14% of blank sample; the microstructure has been denser and more uniform than that of untreated; meanwhile, the grain has been refined and the concentration gradients of the elements permeated have been decreased obviously.
基金Project supported bythe Ministry of Science and Technology via‘863’High Technology Projects (2002AA332080)
文摘The surface oxidation behavior of pressureless sintered Al2O3/SiC nanocomposite was studied from 1000 to 1400 ℃ for more than 10 h in air. Weight gain during the process of heat treatment was measured by TG analysis. Phase transformation and microstructure changes of these specimens due to oxidation were investigated with X-ray diffraction (XRD), SEM and EDX technology. Thermogravimetric analysis show that the weight gain as a result of oxidation of SiC become significant above 1200 ℃. In the range of 1000 - 1300 ℃, the SiC grits are usually coated with a layer of amorphous silica after oxidation. Above 1300 ℃, the amorphous silica reacted with alumina matrix and formed mullite or crystallized into cristobalite. The rate of oxidation depends on the formation of dense cristobalite film. Large amount of needle-like mullite and alumina crystals are formed on the surface after oxidation at 1400℃.
文摘The latest progress and research status of laser cladding ceramic coating was summarized. Technique characteristics and influence factors of laser cladding technique were introduced. Laser cladding technique includes the mixing method and laser irradiation. The mixing method can be classified as pre-coating method and synchronization method. The technique parameters include size of facula, scanning speed, cladding sector and times, adding quantity of powder, thickness of coating and quantity of joint coating. The results show that proper technique parameters can be controlled in order to acquire high quality laser cladding coating. Strengthened effect mechanism of rare earth additive is concluded, and the main effects of rare earth additive are micro-alloying, purifying boundary, fining crystal grains, improving crystal boundary, restraining columnar crystal growing. The development of laser cladding ceramic coating research was discussed.
文摘Titamum oxide coatings were formed on me titanium net surface by micro-arc oxidation (MAO) in Na3PO4 solution using an AC power supply. Then the titanium oxide coatings were treated by La (NO3)3 soaking to improve the activity. The structures and photocatalytic ability of titanium oxide coatings before and after surface La (NO3)3 treatment were characterized and evaluated by XRD, SEM, EDX and photocatalytic decoloration of acid brilliant scarlet dye aqueous solution, respectively. The results show that the titanium oxide film is mainly consisted of anatase. After the La(NO3)3 treatment, the sodium ions on TiO2/ Ti film surface are replaced by lanthanum. It is found that the photocatalytic activity of the titanium oxide coatings is enhanced after La(NO3)3 treatment. When La(NO3)3 aqueous concenuration is 0.1 mol·L^-1 and soak time is 12 h, the TiO2/Ti films photocatalytic decoloration rate increases from 15% to 34.8%.