Oxidation of carbon is the main problem or Al2O3 - C refractories. ZrO2 - nitrides composite powder was synthesized through carbothermal reduction and nitridation （CRN） of zircon. The effect of ZrO2 - nitrides compo...Oxidation of carbon is the main problem or Al2O3 - C refractories. ZrO2 - nitrides composite powder was synthesized through carbothermal reduction and nitridation （CRN） of zircon. The effect of ZrO2 - nitrides composite powder addition on oxidation resistance of the Al2O3 - C refractories was investigated by measuring the thickness of oxidation layer. Phase compositions of the Al2O3 - C refractories before and after oxidation were investigated by X-ray diffraction （ XRD ）. Results show that the oxidation resistance of the Al2O3 - C refractories can be obviously improved by adding the synthesized ZrO2 - nitrides composite powder. The formation of mullite and zircon in the oxidation layer results in the densification of oxidation layer, which prevents oxygen diffusion and bnproves the oxidation resistance of the Al2O3 - C refractories.展开更多
The oxidation properties of silver alloy powders and microstructures of oxidized powders have been investigated by thermo gravity analysis(TGA), scanning electron microscopy(SEM) and wave dispersive X ray spectrosco...The oxidation properties of silver alloy powders and microstructures of oxidized powders have been investigated by thermo gravity analysis(TGA), scanning electron microscopy(SEM) and wave dispersive X ray spectroscopy(WDEX). Ag Sn RE alloy powders have been oxidized completely at 610 ℃ within 60 min, with an external pure silver scale forming around each oxidized particle. It is useful to produce electrical contact composites. The excellent oxidation properties of Ag Sn RE alloy powders are attributed to the ideal microstructure of the oxidized powders.展开更多
In order to improve oxidation resistance and ther- mal shock resistance of Al2O3-C refractories, two groups of specimens were prepared with phenolic resin as binder, adding 0, 2 wt% , 4 wt% and 6 wt% commercial SiC or...In order to improve oxidation resistance and ther- mal shock resistance of Al2O3-C refractories, two groups of specimens were prepared with phenolic resin as binder, adding 0, 2 wt% , 4 wt% and 6 wt% commercial SiC or ZrO2-SiC composite powder synthesized from zircon respectively to Al2O3- C refractories, pressing at 200 MPa, drying fully at 250℃, and then carbon embedded firing at 1400℃ for 2 h. Oxidation resistance and thermal shock resistance were researched, phase composition was analyzed by XRD. The results showed that the oxidation of SiC in additives could protect carbon in specimens effectively and thus decreased the mass loss ratio and oxidation area, and improved the oxidation resistance of the specimen. Thermal shock resistance was improved owing to the micro crack toughening of ZrO2 and grain toughening of SiC. In this experiment, the specimens with 6 wt% ZrO2 -SiC composite powder or 6 wt% SiC powder had the best oxidation resistance and thermal shock resistance.展开更多
Silver-tin oxide composite powders and silver powders were synthesized by hydrothermal method using NH3 to complex Ag+, SO 32?to reduce Ag (NH3)+2 and Na2SnO3 as the source of tin. The powders were characterized by XR...Silver-tin oxide composite powders and silver powders were synthesized by hydrothermal method using NH3 to complex Ag+, SO 32?to reduce Ag (NH3)+2 and Na2SnO3 as the source of tin. The powders were characterized by XRD, SEM and EDX. The results show that there are macroscopic and microscopic differences between two kinds of powders. Spherical silver powders are 3 μm in diameter, and silver-tin oxide composite powders are mainly flake of about 0.3 μm in thickness. Silver crystal in silver-tin oxide composite powders is preferentially oriented in the (111) crystallographic direction and its oriented index is 2.581. Crystal lattice parameter of silver crystal of silver tin-oxide composite powders is 0.409 34 nm, larger than 0.408 68 nm of silver powders. The XPS analysis shows that silver in silver-tin oxide composite powders is metallic silver and tin oxide in silver tin-oxide composite powders has the red shift for Sn4+(3d5/2) and O2-(1s).展开更多
Al2O3-SiC-C specimens were prepared using white fused corundum （3-1,≤1 and ≤0.044 mm）,Al2O3-SiC composite powders （d50 ≤ 5 μm）,α-Al2O3 micropowder （d50 =1.2 μm）,SiC powder （≤ 0.044 mm）,flake graphite （...Al2O3-SiC-C specimens were prepared using white fused corundum （3-1,≤1 and ≤0.044 mm）,Al2O3-SiC composite powders （d50 ≤ 5 μm）,α-Al2O3 micropowder （d50 =1.2 μm）,SiC powder （≤ 0.044 mm）,flake graphite （≤ 0.088 mm）,Si powder （d50 =42.8 μm） and B4C powder （d50 ≤10 μm） as main starting materials,and thermosetting phenolic resin as binder.4%,8%,12% and 16% （in mass,the same hereinafter） of Al2O3-SiC composite powders substituted the same quantity of α-Al2O3 micropowder ＋ SiC powder.Effects of composite powder additions on apparent porosity,bulk density,cold modulus of rupture,cold crushing strength,hot modulus of rupture （1 400 ℃）,thermal shock resistance （1 100 ℃,water quenching） and oxidation resistance （1 000 and 1 500 ℃） of Al2O3-SiC -C specimens after 180 ℃ curing,1 000 ℃ 3 h carbon-embedded firing and 1 500 ℃ 3 h carbon-embedded firing,respectively,were researched.The results indicate that：（1） with the increase of Al2O3-SiC composite powder,cold strengths of the cured specimens decline,those of the specimens fired at 1 000 ℃ change a little,and those of the specimens fired at 1 500 ℃ change a little except for an obvious improvement of cold crushing strength ; （2） with the increase of Al2O3-SiC composite powder,hot modulus of rupture at 1 400 ℃ decreases and thermal shock resistance enhances significantly; （3） when Al2O3-SiC composite powder addition is 4%,the oxidation resistance at 1 500 ℃ is the best,and the reason may be the composite powder is finer and more active,which is beneficial to form dense mullite protective layer to retard the O2 diffusion into the specimens.展开更多
A new hydrometallurgical process of chlorination-distillation at low temperatures about 100 °C was developed for recovery of valuable metal and environmental protection. This process was used to treat flue dust c...A new hydrometallurgical process of chlorination-distillation at low temperatures about 100 °C was developed for recovery of valuable metal and environmental protection. This process was used to treat flue dust containing arsenic and antimony and satisfactory results were obtained. Over 99% of arsenic and antimony were recovered, and high purity As2O3 and SbCl3 were produced. A metallic alcoholate technique was developed and proved to be of significant to the utilization of antimony resources. Using this technique, a number of antimony oxide powders were prepared, such as high purity and ultrafine Sb2O3, ultrafine Sb2O3-Sb2O5 and Sb2O3-SnO2 composite powders.展开更多
The liquid-phase coating method was used to deposit Y2O3 ceramic on the surface of α-Al2O3. The coated-Al2O3p/6061AI composites were produced using squeeze casting technology. The microstructure and tensile propertie...The liquid-phase coating method was used to deposit Y2O3 ceramic on the surface of α-Al2O3. The coated-Al2O3p/6061AI composites were produced using squeeze casting technology. The microstructure and tensile properties of the composites were analysed and studied. The results showed that the coated AI2O3 particles are able to disperse homogeneously in the aluminum liquid. The microstructure of the composites is more even in comparison with that of as-received powders. The tensile testing indicated that mechanical properties of the coated-AI2O3p/6061AI composites are better than those of uncoated particles. In the composite with 30% volume fraction, the tensile strength, yield strength as well as elongation is increased by 29.8%, 38.4% and 10.3%, respectively. The SEM analysis of fracture indicated that the dimples of the coated-Al2O3p/6061Al composites are more even.展开更多
The effects of SiC particles(SiCp)on high temperature oxidation behavior of titanium matrix composites(TMCs)under different powder metallurgy processes were investigated.In situ Ti C+Ti_(5)Si_(3)reinforced titanium ma...The effects of SiC particles(SiCp)on high temperature oxidation behavior of titanium matrix composites(TMCs)under different powder metallurgy processes were investigated.In situ Ti C+Ti_(5)Si_(3)reinforced titanium matrix composites were prepared by discharge plasma sintering(SPS)and argon protective sintering(APS).The results show that the two processes have a negligible effect on the composition and hardness of the samples,but the hardness of the two samples is significantly improved by adding SiCp.The apparent porosity of SPS process is obviously smaller than that of APS process,whereas,the apparent porosity increases slightly with the addition of SiCp.The oxide layer thickness and mass gain of the samples obtained by SPS process are smaller than those obtained by APS process.The oxide thickness and mass gain of both processes are further reduced by adding SiCp.The SPS composites showed the best high temperature oxidation resistance.Therefore,TMCs with Si Cp by SPS can effectively improve the high-temperature oxidation behavior of the materials.展开更多
Since Cu-Al powder characteristics have important effects on the preparation of Cu/Al2O3 composite, the apparent activation energy of Al internal oxidation reaction in Cu-Al pre-alloyed powders with different characte...Since Cu-Al powder characteristics have important effects on the preparation of Cu/Al2O3 composite, the apparent activation energy of Al internal oxidation reaction in Cu-Al pre-alloyed powders with different characteristics was calculated in the present investigation. The microstructure and properties of the synthesized Cu/Al2O3 were studied. The results show that high-energy milling can obviously promote internal oxidation of Al in Cu-Al powders in the same solid solubility. At the same milling conditions and internal oxidation parameters, the solid solution of Al in Cu either in low or high amount will result in the poor microstructure and properties of the Cu/Al2O3 composite. Subsequently, when high-energy milling and internal oxidation are synchronously used to prepare the Cu/Al2O3 composite, there should be an appropriate solubility and milling effect for the pre-alloyed powders.展开更多
Y（NO3）3 and NH3·H2O were used as a raw materials,and nano-Y2O3 powder was successfully synthesized by a precipitation method.Employing TEOS as a raw material,SiO2 powder was successfully prepared by a alkoxide-...Y（NO3）3 and NH3·H2O were used as a raw materials,and nano-Y2O3 powder was successfully synthesized by a precipitation method.Employing TEOS as a raw material,SiO2 powder was successfully prepared by a alkoxide-hydrolysis method,and a Y2O3/SiO2 composite powder was obtained by coating.The Y2O3,SiO2,and Y2O3/SiO2 powders were characterized using X-ray diffraction（XRD）,scanning electron microscopy（SEM）,and Fourier transform infrared spectrophotometer（FT-IR）;the Y2O3 and Y2O3/SiO2 powders were further examined by photoluminescence（PL） spectra.The results indicated that the Y2O3 powder had a body-centered cubic structure with an average size of 35 nm,while the SiO2 powder was amorphous,with an average size of 145 nm and a narrow size distribution.The PL spectra of the Y2O3 and Y2O3/SiO2 powders showed that their wavelength of emission spectra were 585 nm,while their wavelength of excitation spectra were in the range of 240-260 nm.The optical properties of the Y2O3/SiO2 powder were identical to the Y2O3 powder.展开更多
The purpose of this study is to investigate the oxidation behaviors of the TA15 titanium alloy and TiBw/TA15 composite with network microstructure in the temperature range of 873–1073 K.The results show that the oxid...The purpose of this study is to investigate the oxidation behaviors of the TA15 titanium alloy and TiBw/TA15 composite with network microstructure in the temperature range of 873–1073 K.The results show that the oxidation kinetics of the TA15 titanium alloy and TiBw/TA15 composite follows different laws at various oxidation temperatures.Moreover,the effective activation energy Q for oxidation of the TA15 titanium alloy and TiBw/TA15 composite is determined to be 299±19.9 kJ/mol and 339±8.31 kJ/mol at the temperature of 973–1073 K,respectively.The experimental achievements of oxidation kinetics and oxide scales formed in the test temperatures indicate that the TiBw/TA15 composite exhibits a higher oxidation resistance than TA15 titanium alloy.A schematic diagram of oxidation mechanism is established to further reveal the oxidation process for TiBw/TA15 composite at elevated temperatures.展开更多
The development of low-carbon refractories is of great significance,but it is limited by the deteriorated properties that resulted from the decreased graphite content.Incorporating composite powders has proved to be e...The development of low-carbon refractories is of great significance,but it is limited by the deteriorated properties that resulted from the decreased graphite content.Incorporating composite powders has proved to be effective in improving the properties of low-carbon refractories.The recent progress in the synthesis of composite powders including modified graphite,nanocarbon-containing composite powders,oxide/non-oxide and non-oxide composite powders and their applications in low-carbon refractories were reviewed,and the future development of composite powder technology was prospected.展开更多
Magnesium matrix composites(MgMCs)have always suffered low strengthening efficiency and poor ductility due to the difficulties in pursuing the well-bonded interface.Herein,graphene nanoplatelets(GNPs)were decorated wi...Magnesium matrix composites(MgMCs)have always suffered low strengthening efficiency and poor ductility due to the difficulties in pursuing the well-bonded interface.Herein,graphene nanoplatelets(GNPs)were decorated with magnesium oxide nanoparticles(MgO NPs)through chemical co-precipitation and then incorporated into AZ91 alloy to fabricate MgMCs via powder thixoforging.The effect of MgO on the interface of the Mg/graphene system was investigated based on the first-principles calculations,and the result indicated that modifying GNPs with MgO NPs was helpful in improving the Mg-GNP interface bonding.The interface structural analysis revealed that the MgO NPs were firmly bonded with both GNPs andα-Mg through the distortion area bonding and semi-coherent interfacial bonding,severing as a bridge to fasten the interface bonding of composites.In addition,the MgO NPs on GNPs acted as a barrier to prevent GNPs from seriously reacting with the AZ91 alloy.As a result,the AZ91/MgO@GNPs composite was endowed with enhancements of 31%and 10%in the yield strength,and increments of 71%and 61%in elongation compared with the AZ91 alloy and AZ91/GNPs composite,respectively,exhibiting a more significant potential in optimizing the strength-toughness tradeoffcompared with the AZ91/GNPs.Moreover,the possible strengthening and toughening mechanisms were also discussed in detail.This work offers a relatively novel surface modification strategy to modulate the Mg-GNP interface for a simultane-ous improvement of strength and ductility.展开更多
The ball milling process and the CuWO-WOprecursors were investigated, and a new highly concentrated wet ball-milled process(HWM) was designed. W-20 wt% Cu composite powders with excellent sintering property were synth...The ball milling process and the CuWO-WOprecursors were investigated, and a new highly concentrated wet ball-milled process(HWM) was designed. W-20 wt% Cu composite powders with excellent sintering property were synthesized by highly concentrated wet ballmilled process and co-reduction. The powders were characterized by scanning electron microscopy(SEM), X-ray diffraction(XRD), field electron transmission electron microscopy(FESEM) and laser-diffraction diameter tester.The results indicate that particle size of W03-CuO powder mixtures decreases to 390 nm rapidly with the milling time increasing to 5 h. The CuWOprecursors promote the microstructural homogeneity of W and Cu. W-Cu composite powders have a highly dispersed and well sintering property. The particle size of W-Cu powders milled by HWM for 5 h is about 680 nm. High-resolution transmission electron microscopy(HRTEM) result suggests that W phase and Cu phase are mixed at nanometer scale. The above W-Cu composite powders reach the relative density of about 99.3%.展开更多
文摘Oxidation of carbon is the main problem or Al2O3 - C refractories. ZrO2 - nitrides composite powder was synthesized through carbothermal reduction and nitridation （CRN） of zircon. The effect of ZrO2 - nitrides composite powder addition on oxidation resistance of the Al2O3 - C refractories was investigated by measuring the thickness of oxidation layer. Phase compositions of the Al2O3 - C refractories before and after oxidation were investigated by X-ray diffraction （ XRD ）. Results show that the oxidation resistance of the Al2O3 - C refractories can be obviously improved by adding the synthesized ZrO2 - nitrides composite powder. The formation of mullite and zircon in the oxidation layer results in the densification of oxidation layer, which prevents oxygen diffusion and bnproves the oxidation resistance of the Al2O3 - C refractories.
文摘The oxidation properties of silver alloy powders and microstructures of oxidized powders have been investigated by thermo gravity analysis(TGA), scanning electron microscopy(SEM) and wave dispersive X ray spectroscopy(WDEX). Ag Sn RE alloy powders have been oxidized completely at 610 ℃ within 60 min, with an external pure silver scale forming around each oxidized particle. It is useful to produce electrical contact composites. The excellent oxidation properties of Ag Sn RE alloy powders are attributed to the ideal microstructure of the oxidized powders.
文摘In order to improve oxidation resistance and ther- mal shock resistance of Al2O3-C refractories, two groups of specimens were prepared with phenolic resin as binder, adding 0, 2 wt% , 4 wt% and 6 wt% commercial SiC or ZrO2-SiC composite powder synthesized from zircon respectively to Al2O3- C refractories, pressing at 200 MPa, drying fully at 250℃, and then carbon embedded firing at 1400℃ for 2 h. Oxidation resistance and thermal shock resistance were researched, phase composition was analyzed by XRD. The results showed that the oxidation of SiC in additives could protect carbon in specimens effectively and thus decreased the mass loss ratio and oxidation area, and improved the oxidation resistance of the specimen. Thermal shock resistance was improved owing to the micro crack toughening of ZrO2 and grain toughening of SiC. In this experiment, the specimens with 6 wt% ZrO2 -SiC composite powder or 6 wt% SiC powder had the best oxidation resistance and thermal shock resistance.
文摘Silver-tin oxide composite powders and silver powders were synthesized by hydrothermal method using NH3 to complex Ag+, SO 32?to reduce Ag (NH3)+2 and Na2SnO3 as the source of tin. The powders were characterized by XRD, SEM and EDX. The results show that there are macroscopic and microscopic differences between two kinds of powders. Spherical silver powders are 3 μm in diameter, and silver-tin oxide composite powders are mainly flake of about 0.3 μm in thickness. Silver crystal in silver-tin oxide composite powders is preferentially oriented in the (111) crystallographic direction and its oriented index is 2.581. Crystal lattice parameter of silver crystal of silver tin-oxide composite powders is 0.409 34 nm, larger than 0.408 68 nm of silver powders. The XPS analysis shows that silver in silver-tin oxide composite powders is metallic silver and tin oxide in silver tin-oxide composite powders has the red shift for Sn4+(3d5/2) and O2-(1s).
文摘Al2O3-SiC-C specimens were prepared using white fused corundum （3-1,≤1 and ≤0.044 mm）,Al2O3-SiC composite powders （d50 ≤ 5 μm）,α-Al2O3 micropowder （d50 =1.2 μm）,SiC powder （≤ 0.044 mm）,flake graphite （≤ 0.088 mm）,Si powder （d50 =42.8 μm） and B4C powder （d50 ≤10 μm） as main starting materials,and thermosetting phenolic resin as binder.4%,8%,12% and 16% （in mass,the same hereinafter） of Al2O3-SiC composite powders substituted the same quantity of α-Al2O3 micropowder ＋ SiC powder.Effects of composite powder additions on apparent porosity,bulk density,cold modulus of rupture,cold crushing strength,hot modulus of rupture （1 400 ℃）,thermal shock resistance （1 100 ℃,water quenching） and oxidation resistance （1 000 and 1 500 ℃） of Al2O3-SiC -C specimens after 180 ℃ curing,1 000 ℃ 3 h carbon-embedded firing and 1 500 ℃ 3 h carbon-embedded firing,respectively,were researched.The results indicate that：（1） with the increase of Al2O3-SiC composite powder,cold strengths of the cured specimens decline,those of the specimens fired at 1 000 ℃ change a little,and those of the specimens fired at 1 500 ℃ change a little except for an obvious improvement of cold crushing strength ; （2） with the increase of Al2O3-SiC composite powder,hot modulus of rupture at 1 400 ℃ decreases and thermal shock resistance enhances significantly; （3） when Al2O3-SiC composite powder addition is 4%,the oxidation resistance at 1 500 ℃ is the best,and the reason may be the composite powder is finer and more active,which is beneficial to form dense mullite protective layer to retard the O2 diffusion into the specimens.
文摘A new hydrometallurgical process of chlorination-distillation at low temperatures about 100 °C was developed for recovery of valuable metal and environmental protection. This process was used to treat flue dust containing arsenic and antimony and satisfactory results were obtained. Over 99% of arsenic and antimony were recovered, and high purity As2O3 and SbCl3 were produced. A metallic alcoholate technique was developed and proved to be of significant to the utilization of antimony resources. Using this technique, a number of antimony oxide powders were prepared, such as high purity and ultrafine Sb2O3, ultrafine Sb2O3-Sb2O5 and Sb2O3-SnO2 composite powders.
基金This investigation was supported by the National Natural Science Foundation of China(No.59771014 and 50071019).The supports are gratefully acknowledged.
文摘The liquid-phase coating method was used to deposit Y2O3 ceramic on the surface of α-Al2O3. The coated-Al2O3p/6061AI composites were produced using squeeze casting technology. The microstructure and tensile properties of the composites were analysed and studied. The results showed that the coated AI2O3 particles are able to disperse homogeneously in the aluminum liquid. The microstructure of the composites is more even in comparison with that of as-received powders. The tensile testing indicated that mechanical properties of the coated-AI2O3p/6061AI composites are better than those of uncoated particles. In the composite with 30% volume fraction, the tensile strength, yield strength as well as elongation is increased by 29.8%, 38.4% and 10.3%, respectively. The SEM analysis of fracture indicated that the dimples of the coated-Al2O3p/6061Al composites are more even.
基金Funded by the Key Projects of Equipment Pre-research Foundation of the Ministry of Equipment Development of the Central Military Commission of China(No.6140922010201)the Key R&D Plan of Zhenjiang in 2018(No.GY2018021)。
文摘The effects of SiC particles(SiCp)on high temperature oxidation behavior of titanium matrix composites(TMCs)under different powder metallurgy processes were investigated.In situ Ti C+Ti_(5)Si_(3)reinforced titanium matrix composites were prepared by discharge plasma sintering(SPS)and argon protective sintering(APS).The results show that the two processes have a negligible effect on the composition and hardness of the samples,but the hardness of the two samples is significantly improved by adding SiCp.The apparent porosity of SPS process is obviously smaller than that of APS process,whereas,the apparent porosity increases slightly with the addition of SiCp.The oxide layer thickness and mass gain of the samples obtained by SPS process are smaller than those obtained by APS process.The oxide thickness and mass gain of both processes are further reduced by adding SiCp.The SPS composites showed the best high temperature oxidation resistance.Therefore,TMCs with Si Cp by SPS can effectively improve the high-temperature oxidation behavior of the materials.
基金supported by the National Natural Science Foundation of China (No.50574075)Program for New Century Excellent Talents in University(No.NCET-05-0873)Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP 20060700011)
文摘Since Cu-Al powder characteristics have important effects on the preparation of Cu/Al2O3 composite, the apparent activation energy of Al internal oxidation reaction in Cu-Al pre-alloyed powders with different characteristics was calculated in the present investigation. The microstructure and properties of the synthesized Cu/Al2O3 were studied. The results show that high-energy milling can obviously promote internal oxidation of Al in Cu-Al powders in the same solid solubility. At the same milling conditions and internal oxidation parameters, the solid solution of Al in Cu either in low or high amount will result in the poor microstructure and properties of the Cu/Al2O3 composite. Subsequently, when high-energy milling and internal oxidation are synchronously used to prepare the Cu/Al2O3 composite, there should be an appropriate solubility and milling effect for the pre-alloyed powders.
基金supported by the National Basic Research Program of China (No.2007CB613603)
文摘Y（NO3）3 and NH3·H2O were used as a raw materials,and nano-Y2O3 powder was successfully synthesized by a precipitation method.Employing TEOS as a raw material,SiO2 powder was successfully prepared by a alkoxide-hydrolysis method,and a Y2O3/SiO2 composite powder was obtained by coating.The Y2O3,SiO2,and Y2O3/SiO2 powders were characterized using X-ray diffraction（XRD）,scanning electron microscopy（SEM）,and Fourier transform infrared spectrophotometer（FT-IR）;the Y2O3 and Y2O3/SiO2 powders were further examined by photoluminescence（PL） spectra.The results indicated that the Y2O3 powder had a body-centered cubic structure with an average size of 35 nm,while the SiO2 powder was amorphous,with an average size of 145 nm and a narrow size distribution.The PL spectra of the Y2O3 and Y2O3/SiO2 powders showed that their wavelength of emission spectra were 585 nm,while their wavelength of excitation spectra were in the range of 240-260 nm.The optical properties of the Y2O3/SiO2 powder were identical to the Y2O3 powder.
基金financially supported by the National Natural Science Foundation of China(Nos.51674093 and 91860122).
文摘The purpose of this study is to investigate the oxidation behaviors of the TA15 titanium alloy and TiBw/TA15 composite with network microstructure in the temperature range of 873–1073 K.The results show that the oxidation kinetics of the TA15 titanium alloy and TiBw/TA15 composite follows different laws at various oxidation temperatures.Moreover,the effective activation energy Q for oxidation of the TA15 titanium alloy and TiBw/TA15 composite is determined to be 299±19.9 kJ/mol and 339±8.31 kJ/mol at the temperature of 973–1073 K,respectively.The experimental achievements of oxidation kinetics and oxide scales formed in the test temperatures indicate that the TiBw/TA15 composite exhibits a higher oxidation resistance than TA15 titanium alloy.A schematic diagram of oxidation mechanism is established to further reveal the oxidation process for TiBw/TA15 composite at elevated temperatures.
基金The authors thankfully acknowledge the financial support of the National Natural Science Foundation of China(Nos.U20A20239,U1908227,and 51772236)for sponsoring this work.
文摘The development of low-carbon refractories is of great significance,but it is limited by the deteriorated properties that resulted from the decreased graphite content.Incorporating composite powders has proved to be effective in improving the properties of low-carbon refractories.The recent progress in the synthesis of composite powders including modified graphite,nanocarbon-containing composite powders,oxide/non-oxide and non-oxide composite powders and their applications in low-carbon refractories were reviewed,and the future development of composite powder technology was prospected.
基金supported by the National Natural Science Foundation of China(No.51761028)the Natural Science Foundation of Gansu Province,China(No.21JR7RA232).
文摘Magnesium matrix composites(MgMCs)have always suffered low strengthening efficiency and poor ductility due to the difficulties in pursuing the well-bonded interface.Herein,graphene nanoplatelets(GNPs)were decorated with magnesium oxide nanoparticles(MgO NPs)through chemical co-precipitation and then incorporated into AZ91 alloy to fabricate MgMCs via powder thixoforging.The effect of MgO on the interface of the Mg/graphene system was investigated based on the first-principles calculations,and the result indicated that modifying GNPs with MgO NPs was helpful in improving the Mg-GNP interface bonding.The interface structural analysis revealed that the MgO NPs were firmly bonded with both GNPs andα-Mg through the distortion area bonding and semi-coherent interfacial bonding,severing as a bridge to fasten the interface bonding of composites.In addition,the MgO NPs on GNPs acted as a barrier to prevent GNPs from seriously reacting with the AZ91 alloy.As a result,the AZ91/MgO@GNPs composite was endowed with enhancements of 31%and 10%in the yield strength,and increments of 71%and 61%in elongation compared with the AZ91 alloy and AZ91/GNPs composite,respectively,exhibiting a more significant potential in optimizing the strength-toughness tradeoffcompared with the AZ91/GNPs.Moreover,the possible strengthening and toughening mechanisms were also discussed in detail.This work offers a relatively novel surface modification strategy to modulate the Mg-GNP interface for a simultane-ous improvement of strength and ductility.
基金financially supported by the National Natural Science Foundation of China (No. 51274246)
文摘The ball milling process and the CuWO-WOprecursors were investigated, and a new highly concentrated wet ball-milled process(HWM) was designed. W-20 wt% Cu composite powders with excellent sintering property were synthesized by highly concentrated wet ballmilled process and co-reduction. The powders were characterized by scanning electron microscopy(SEM), X-ray diffraction(XRD), field electron transmission electron microscopy(FESEM) and laser-diffraction diameter tester.The results indicate that particle size of W03-CuO powder mixtures decreases to 390 nm rapidly with the milling time increasing to 5 h. The CuWOprecursors promote the microstructural homogeneity of W and Cu. W-Cu composite powders have a highly dispersed and well sintering property. The particle size of W-Cu powders milled by HWM for 5 h is about 680 nm. High-resolution transmission electron microscopy(HRTEM) result suggests that W phase and Cu phase are mixed at nanometer scale. The above W-Cu composite powders reach the relative density of about 99.3%.
