A SiC/ZrSiO4？SiO2 （SZS） coating was successfully fabricated on the carbon/carbon （C/C） composites by pack cementation, slurry painting and sintering to improve the anti-oxidation property and thermal shock r...A SiC/ZrSiO4？SiO2 （SZS） coating was successfully fabricated on the carbon/carbon （C/C） composites by pack cementation, slurry painting and sintering to improve the anti-oxidation property and thermal shock resistance. The anti-oxidation properties under different oxygen partial pressures （OPP） and thermal shock resistance of the SZS coating were investigated. The results show that the SZS coated sample under low OPP, corresponding to the ambient air, during isothermal oxidation was 0.54% in mass gain after 111 h oxidation at 1500 ° C and less than 0.03% in mass loss after 50 h oxidation in high OPP, corresponding to the air flow rate of 36 L/h. Additionally, the residual compressive strengths （RCS） of the SZS coated samples after oxidation for 50 h in high OPP and 80 h in low OPP remain about 70% and 72.5% of those of original C/C samples, respectively. Moreover, the mass loss of SZS coated samples subjected to the thermal cycle from 1500 ° C in high OPP to boiling water for 30 times was merely 1.61%.展开更多
A sophisticated stir casting route to fabricate large scale AA6061-31%B4C composite was developed. Key process parameters were studied, microstructure and mechanical properties of the composite were investigated. The ...A sophisticated stir casting route to fabricate large scale AA6061-31%B4C composite was developed. Key process parameters were studied, microstructure and mechanical properties of the composite were investigated. The results indicated that vacuum stirring/casting, B4C/Mg feeding and ingots cooling were essential to the successful fabrication of AA6061-31%B4C composite. Chemical erosion examination verified the designed B4 C content; X-ray fluorescence spectrometer（XFS） showed the chemical composition of Mg and Si in the matrix conformed to industry standards; scanning electronic microscope（SEM） and X-ray diffraction（XRD） revealed that B4 C particles were evenly distributed in the composites with well dispersed Mg2Si precipitates. Tensile testing results showed that the AA6061-31%B4C composite had a tensile strength of 340 MPa, improved by 112.5% compared with AA1100-31%B4C composite, which is attributed to the enhanced strength of the matrix alloy.展开更多
With LiAc-2H2O as Li precursor,pure olivine phase LiFePO4/C was synthesized at a relatively low temperature（650 ℃） and short sintering period（4 h） by molten salt carbothermal reduction method.Scanning electron mi...With LiAc-2H2O as Li precursor,pure olivine phase LiFePO4/C was synthesized at a relatively low temperature（650 ℃） and short sintering period（4 h） by molten salt carbothermal reduction method.Scanning electron micrograph shows that particle size of the product is about 1μm,smaller than that of the sample synthesized with Li2CO3 as Li precursor.Electrochemical measurements prove that LiFePO4/C obtained from LiAc-2H2O shows high capacity.The initial discharge capacities are 148 mA-h/g at 0.5C rate and 115 mA-h/g at 5C rate,respectively.After 50 cycles,the capacity retention ratios are 93% and 89% at 0.5C rate and 5C rate,respectively.展开更多
The compressive properties of the aluminum matrix composite reinforced with 55% B4C （volume fraction） particles were characterized using Gleeble 3500 thermal-mechanical testing machine. The compressive stress--strai...The compressive properties of the aluminum matrix composite reinforced with 55% B4C （volume fraction） particles were characterized using Gleeble 3500 thermal-mechanical testing machine. The compressive stress--strain curves were obtained at the temperature ranging from 298 to 773 K and strain rate ranging from 1×10^（-3） to 5 s ^（-1）. The results showed that the dynamic compressive strength decreased more slowly than the quasi-static compressive strength at elevated temperatures, which was attributed to the different failure modes of the composite under dynamic and quasi-static load. The strain rate sensitivity increased from 0.02 to 0.13 when the temperature increased from room temperature to 773 K, suggesting that the strain rate sensitivity of this type of composite is a function of temperature.展开更多
The B4C/2024Al composites were successfully produced by pressureless infiltration method, and the effects of heat treatment on phase content and mechanical properties were investigated by X-ray diffraction （XRD）, sc...The B4C/2024Al composites were successfully produced by pressureless infiltration method, and the effects of heat treatment on phase content and mechanical properties were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and mechanical properties testing. The results show that phases of BnC/2024Al composites include B4C, Al, Al3BC, AlB2 and Al2Cu. The phase species remain unchanged; however, the phase content of the composites changes significantly after heat treatment at the temperature of 660, 700, 800 or 900 ℃ for 12, 24 or 36 h. It is found that the heat treatment results in not only considerable enhancement in hardness, but also reduction in bending strength of the composites. Heat treatment at 800 ℃ for 36 h does best to hardness of the composites, while at 700 ℃ for 36 h it is the most beneficial to their comprehensive mechanical properties.展开更多
The B4C/Mg composites fabricated by metal-assisted pressureless infiltration technique were used as experimental material, and the wear behavior and mechanism of this material were studied. A pin-on-disc apparatus was...The B4C/Mg composites fabricated by metal-assisted pressureless infiltration technique were used as experimental material, and the wear behavior and mechanism of this material were studied. A pin-on-disc apparatus was used to evaluate the wear behavior where loads of 20, 40, 60 and 80 N, and a sliding velocity of 250 r/min were exerted. The results show that B4C/Mg composites possess superior wear resistance than pure Mg under various applied loads, and the content of Ti, as infiltration inducer, has an influence on the wear resistance of B4C/Mg composites. The dominant wear mechanism for pure Mg is abrasion, while that for B4C/Mg composites under low loads is adhesion and delamination. Under high loads, the wear mechanism of B4C/Mg composites can be attributed to thermal softening and melting or plastic deformation.展开更多
This work aimed to fabricate B4C reinforced aluminum matrix composites via blended powder semisolid forming that is an implementation of the benefits of semisolid forming to the powder metallurgy. Al7075 elements were...This work aimed to fabricate B4C reinforced aluminum matrix composites via blended powder semisolid forming that is an implementation of the benefits of semisolid forming to the powder metallurgy. Al7075 elements were incrementally added to ethanol solution under mechanical mixing. Al7075 constituents and B4C particles were blended in a high energy ball mill. Cold compacted Al7075/B4C blends were pressed at semisolid state. The effects of the size of the matrix（20, 45 and 63 μm）, reinforcing volume fraction（5%, 10% and 20%） and semisolid compaction pressure（50 and 100 MPa） on the morphology, microstructure, density, hardness, compression and bending strength were thoroughly analyzed. Experimental results revealed that the highest microstructural uniformity was achieved when large B4C particles（45 μm） were distributed within the small particles（20 μm） of the matrix phase. Composites with matrix particles larger than reinforcing phase indicated agglomerations in loadings more than 10%（volume fraction）. Agglomerated regions resisted against penetration of the liquid phase to the pores and lowered the density and strength of these composites. Composites with 20 μm Al7075 and 20%（volume fraction） 45 μm B4C powder pressed under 100 MPa exhibited the highest values of hardness（HV 190） and compressive strength（336 MPa）.展开更多
基金Project supported by the Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Center,ChinaProject(51205417)supported by the National Natural Science Foundation of China
文摘A SiC/ZrSiO4？SiO2 （SZS） coating was successfully fabricated on the carbon/carbon （C/C） composites by pack cementation, slurry painting and sintering to improve the anti-oxidation property and thermal shock resistance. The anti-oxidation properties under different oxygen partial pressures （OPP） and thermal shock resistance of the SZS coating were investigated. The results show that the SZS coated sample under low OPP, corresponding to the ambient air, during isothermal oxidation was 0.54% in mass gain after 111 h oxidation at 1500 ° C and less than 0.03% in mass loss after 50 h oxidation in high OPP, corresponding to the air flow rate of 36 L/h. Additionally, the residual compressive strengths （RCS） of the SZS coated samples after oxidation for 50 h in high OPP and 80 h in low OPP remain about 70% and 72.5% of those of original C/C samples, respectively. Moreover, the mass loss of SZS coated samples subjected to the thermal cycle from 1500 ° C in high OPP to boiling water for 30 times was merely 1.61%.
基金founded by Joint Laboratory of Nuclear Materials and Service Safety (2013966003),China
文摘A sophisticated stir casting route to fabricate large scale AA6061-31%B4C composite was developed. Key process parameters were studied, microstructure and mechanical properties of the composite were investigated. The results indicated that vacuum stirring/casting, B4C/Mg feeding and ingots cooling were essential to the successful fabrication of AA6061-31%B4C composite. Chemical erosion examination verified the designed B4 C content; X-ray fluorescence spectrometer（XFS） showed the chemical composition of Mg and Si in the matrix conformed to industry standards; scanning electronic microscope（SEM） and X-ray diffraction（XRD） revealed that B4 C particles were evenly distributed in the composites with well dispersed Mg2Si precipitates. Tensile testing results showed that the AA6061-31%B4C composite had a tensile strength of 340 MPa, improved by 112.5% compared with AA1100-31%B4C composite, which is attributed to the enhanced strength of the matrix alloy.
基金Project(21001041) supported by the National Natural Science Foundation of ChinaProject(102300410256) supported by Henan Province Foundation and Advanced Technology Research Program,China+1 种基金Project(102102210183) supported by the Key Scientific and Technological Research Project of Henan Province,ChinaProject(2011B480005) supported by the Natural Science Research Project of Henan Province,China
文摘With LiAc-2H2O as Li precursor,pure olivine phase LiFePO4/C was synthesized at a relatively low temperature（650 ℃） and short sintering period（4 h） by molten salt carbothermal reduction method.Scanning electron micrograph shows that particle size of the product is about 1μm,smaller than that of the sample synthesized with Li2CO3 as Li precursor.Electrochemical measurements prove that LiFePO4/C obtained from LiAc-2H2O shows high capacity.The initial discharge capacities are 148 mA-h/g at 0.5C rate and 115 mA-h/g at 5C rate,respectively.After 50 cycles,the capacity retention ratios are 93% and 89% at 0.5C rate and 5C rate,respectively.
文摘The compressive properties of the aluminum matrix composite reinforced with 55% B4C （volume fraction） particles were characterized using Gleeble 3500 thermal-mechanical testing machine. The compressive stress--strain curves were obtained at the temperature ranging from 298 to 773 K and strain rate ranging from 1×10^（-3） to 5 s ^（-1）. The results showed that the dynamic compressive strength decreased more slowly than the quasi-static compressive strength at elevated temperatures, which was attributed to the different failure modes of the composite under dynamic and quasi-static load. The strain rate sensitivity increased from 0.02 to 0.13 when the temperature increased from room temperature to 773 K, suggesting that the strain rate sensitivity of this type of composite is a function of temperature.
基金Project(2011CB605805)supported by the National Basic Research Program of China
文摘The B4C/2024Al composites were successfully produced by pressureless infiltration method, and the effects of heat treatment on phase content and mechanical properties were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and mechanical properties testing. The results show that phases of BnC/2024Al composites include B4C, Al, Al3BC, AlB2 and Al2Cu. The phase species remain unchanged; however, the phase content of the composites changes significantly after heat treatment at the temperature of 660, 700, 800 or 900 ℃ for 12, 24 or 36 h. It is found that the heat treatment results in not only considerable enhancement in hardness, but also reduction in bending strength of the composites. Heat treatment at 800 ℃ for 36 h does best to hardness of the composites, while at 700 ℃ for 36 h it is the most beneficial to their comprehensive mechanical properties.
基金Project(51271051)supported by the National Natural Sciecne Foundation of China
文摘The B4C/Mg composites fabricated by metal-assisted pressureless infiltration technique were used as experimental material, and the wear behavior and mechanism of this material were studied. A pin-on-disc apparatus was used to evaluate the wear behavior where loads of 20, 40, 60 and 80 N, and a sliding velocity of 250 r/min were exerted. The results show that B4C/Mg composites possess superior wear resistance than pure Mg under various applied loads, and the content of Ti, as infiltration inducer, has an influence on the wear resistance of B4C/Mg composites. The dominant wear mechanism for pure Mg is abrasion, while that for B4C/Mg composites under low loads is adhesion and delamination. Under high loads, the wear mechanism of B4C/Mg composites can be attributed to thermal softening and melting or plastic deformation.
基金Tabriz Branch,Islamic Azad University for the financial support of this research,which is based on a research project contract
文摘This work aimed to fabricate B4C reinforced aluminum matrix composites via blended powder semisolid forming that is an implementation of the benefits of semisolid forming to the powder metallurgy. Al7075 elements were incrementally added to ethanol solution under mechanical mixing. Al7075 constituents and B4C particles were blended in a high energy ball mill. Cold compacted Al7075/B4C blends were pressed at semisolid state. The effects of the size of the matrix（20, 45 and 63 μm）, reinforcing volume fraction（5%, 10% and 20%） and semisolid compaction pressure（50 and 100 MPa） on the morphology, microstructure, density, hardness, compression and bending strength were thoroughly analyzed. Experimental results revealed that the highest microstructural uniformity was achieved when large B4C particles（45 μm） were distributed within the small particles（20 μm） of the matrix phase. Composites with matrix particles larger than reinforcing phase indicated agglomerations in loadings more than 10%（volume fraction）. Agglomerated regions resisted against penetration of the liquid phase to the pores and lowered the density and strength of these composites. Composites with 20 μm Al7075 and 20%（volume fraction） 45 μm B4C powder pressed under 100 MPa exhibited the highest values of hardness（HV 190） and compressive strength（336 MPa）.
