Atmospheric pressure low-temperature plasma is a promising tool in biomedicine applications including blood coagulation,bacterial inactivation,sterilization,and cancer treatment,due to its high chemical activity and l...Atmospheric pressure low-temperature plasma is a promising tool in biomedicine applications including blood coagulation,bacterial inactivation,sterilization,and cancer treatment,due to its high chemical activity and limited thermal damage.It is of great importance to develop portable plasma sources that are safe to human touch and suitable for outdoor and household operation.In this work,a portable and rechargeable low-temperature plasma spark discharge device(130 mm×80 mm×35 mm,300 g)was designed.The discharge frequency and plume length were optimized by the selection of resistance,capacitance,electrode gap,and ground electrode aperture.Results show that the spark plasma plume is generated with a length of 12 mm and a frequency of 10 Hz at a capacitance of 0.33μF.resistance of 1 MΩ,electrode gap of 2 mm,and ground electrode aperture of 1.5 mm.Biological tests indicate that the plasma produced by this device contains abundant reactive species,which can be applied in plasma biomedicine,including daily sterilization and wound healing.展开更多
Within the past ten years,spark plasma sintering(SPS)has become an increasingly popular process for Mg manufacturing.In the SPS process,interparticle diffusion of compressed particles is rapidly achieved due to the co...Within the past ten years,spark plasma sintering(SPS)has become an increasingly popular process for Mg manufacturing.In the SPS process,interparticle diffusion of compressed particles is rapidly achieved due to the concept of Joule heating.Compared to traditional and additive manufacturing(AM)techniques,SPS gives unique control of the structural and microstructural features of Mg components.By doing so,their mechanical,tribological,and corrosion properties can be tailored.Although great advancements in this field have been made,these pieces of knowledge are scattered and have not been contextualized into a single work.The motivation of this work is to address this scientific gap and to provide a groundwork for understanding the basics of SPS manufacturing for Mg.To do so,the existing body of SPS Mg literature was first surveyed,with a focus on their structural formation and degradation mechanisms.It was found that successful Mg SPS fabrication highly depended on the processing temperature,particle size,and particle crystallinity.The addition of metal and ceramic composites also affected their microstructural features due to the Zener pinning effect.In degradative environments,their performance depends on their structural features and whether they have secondary phased composites.In industrial applications,SPS'd Mg was found to have great potential in biomedical,hydrogen storage,battery,automotive,and recycling sectors.The prospects to advance the field include using Mg as a doping agent for crystallite size refinement and using bulk metallic Mg-based glass powders for amorphous SPS components.Despite these findings,the interactions of multi-composites on the processing-structure-property relationships of SPS Mg is not well understood.In total,this work will provide a useful direction in the SPS field and serve as a milestone for future Mg-based SPS manufacturing.展开更多
In this study,a single-doped phosphors yttrium aluminum garnet(Y_(3)Al_(5)O_(12),YAG):Ce^(3+),single-doped YAG:Sc^(3+),and double-doped phosphors YAG:Ce^(3+),Sc^(3+) were prepared by spark plasma sintering(SPS)(lower ...In this study,a single-doped phosphors yttrium aluminum garnet(Y_(3)Al_(5)O_(12),YAG):Ce^(3+),single-doped YAG:Sc^(3+),and double-doped phosphors YAG:Ce^(3+),Sc^(3+) were prepared by spark plasma sintering(SPS)(lower than 1 200℃).The characteristics of synthesized phosphors were determined using scanning electron microscopy(SEM),X-ray diffraction(XRD),and fluorescence spectroscopy.During SPS,the lattice structure of YAG was maintained by the added Ce^(3+) and Sc^(3+).The emission wavelength of YAG:Ce^(3+) prepared from SPS(425-700 nm) was wider compared to that of YAG:Ce^(3+) prepared from high-temperature solid-state reaction(HSSR)(500-700 nm).The incorporation of low-dose Sc^(3+) in YAG:Ce^(3+) moved the emission peak towards the short wavelength.展开更多
W-based WTaVCr refractory high entropy alloys (RHEA) may be novel and promising candidate materials for plasma facing components in the first wall and diverter in fusion reactors. This alloy has been developed by a po...W-based WTaVCr refractory high entropy alloys (RHEA) may be novel and promising candidate materials for plasma facing components in the first wall and diverter in fusion reactors. This alloy has been developed by a powder metallurgy process combining mechanical alloying and spark plasma sintering (SPS). The SPSed samples contained two phases, in which the matrix is RHEA with a body-centered cubic structure, while the oxide phase was most likely Ta2VO6through a combined analysis of X-ray diffraction (XRD),energy-dispersive spectroscopy (EDS), and selected area electron diffraction (SAED). The higher oxygen affinity of Ta and V may explain the preferential formation of their oxide phases based on thermodynamic calculations. Electron backscatter diffraction (EBSD) revealed an average grain size of 6.2μm. WTaVCr RHEA showed a peak compressive strength of 2997 MPa at room temperature and much higher micro-and nano-hardness than W and other W-based RHEAs in the literature. Their high Rockwell hardness can be retained to at least 1000°C.展开更多
How to increase strength without sacrificing ductility has been developed as a key goal in the manufacture of high-performance metals or alloys. Herein, the double-nanophase intragranular yttrium oxide dispersion stre...How to increase strength without sacrificing ductility has been developed as a key goal in the manufacture of high-performance metals or alloys. Herein, the double-nanophase intragranular yttrium oxide dispersion strengthened iron alloy with high strength and appreciable ductility was fabricated by solution combustion route and subsequent spark plasma sintering, and the influences of yttrium oxide content and sintering temperature on microstructures and mechanical properties were investigated. The results show at the same sintering temperature,with the increase of yttrium oxide content, the relative density of the sintered alloy decreases and the strength increases. For Fe–2wt%Y_(2)O_(3)alloy, as the sintering temperature increases gradually, the compressive strength decreases, while the strain-to-failure increases. The Fe–2wt%Y_(2)O_(3)alloy with 15.5 nm Y_(2)O_(3)particles uniformly distributed into the 147.5 nm iron grain interior sintered at 650℃ presents a high ultimate compressive strength of 1.86 GPa and large strain-to-failure of 29%. The grain boundary strengthening and intragranular second-phase particle dispersion strengthening are the main dominant mechanisms to enhance the mechanical properties of the alloy.展开更多
In this paper,the characteristics of detonation combustion ignited by AC-driven non-thermal plasma and spark plug in air/acetylene mixture have been compared in a doubletube experiment system.The two tubes had the sam...In this paper,the characteristics of detonation combustion ignited by AC-driven non-thermal plasma and spark plug in air/acetylene mixture have been compared in a doubletube experiment system.The two tubes had the same structure,and their closed ends were installed with a plasma generator and a spark plug,respectively.The propagation characteristics of the flame were measured by pressure sensors and ion probes.The experiment results show that,compared with a spark plug,the non-thermal plasma obviously broadened the range of equivalence ratio when the detonation wave could develop successfully,it also heightened the pressure value of detonation wave.Meanwhile,the detonation wave development time and the entire flame propagation time were reduced by half.All of these advantages benefited from the larger ignition volume when a non-thermal plasma was applied.展开更多
Spark plasma sintering was used to fabricate Al/diamond composites.The effect of sintering temperature on the microstructure and thermal conductivity(TC) of the composites was investigated with the combination of ex...Spark plasma sintering was used to fabricate Al/diamond composites.The effect of sintering temperature on the microstructure and thermal conductivity(TC) of the composites was investigated with the combination of experimental results and theoretical analysis.The composite sintered at 550℃shows high relative density and strong interfacial bonding,whereas the composites sintered at lower(520CC) and higher(580-600℃) temperatures indicate no interfacial bonding and poor interfacial bonding,respectively.High relative density and strong interfacial bonding can maximize the thermal conductivity of Al/diamond composites,and taking both effects of particle shape and inhomogeneous interfacial thermal conductance into consideration can give a fairly good prediction of composites' thermal conduction properties.展开更多
Mechanically activated W-Cu powders were sintered by a spark plasma sinteringsystem (SPS) in order to develop a new process and improve the properties of the alloy. Propertiessuch as density and hardness were measured...Mechanically activated W-Cu powders were sintered by a spark plasma sinteringsystem (SPS) in order to develop a new process and improve the properties of the alloy. Propertiessuch as density and hardness were measured. The microstructures of the sintered W-Cu alloy sampleswere observed by SEM (scanning electron microscope). The results show that spark plasma sinteringcan obviously lower the sintering temperature and increase the density of the alloy. This processcan also improve the hardness of the alloy. SPS is an effective method to obtain W-Cu powders withhigh density and superior physical properties.展开更多
Carbon nanotube (CNT)-reinforced TiNi matrix composites were synthesized by spark plasma sintering (SPS) employing elemental powders.The phase structure,morphology and transformation behaviors were studied.It was foun...Carbon nanotube (CNT)-reinforced TiNi matrix composites were synthesized by spark plasma sintering (SPS) employing elemental powders.The phase structure,morphology and transformation behaviors were studied.It was found that thermoelastic martensitic transformation be-haviors could be observed from the samples sintered above 800 ℃ even with a short sintering time (5min),and the transformation tempera-tures gradually increased with increasing sintering temperature because of more Ti-rich TiNi phase formation.Although decreasing the sin-tering temperature and time to 700 ℃ and 5min could not protect defective MWCNTs from reacting with Ti,still-perfect MWCNTs re-mained in the specimens sintered at 900 ℃.This method is expected to supply a basis for preparing CNT-reinforced TiNi composites.展开更多
mg-Yb203 electrical contact materials were fabricated by spark plasma sintefing (SPS). The effects of silver powder particle size on the microstructure and properties of the samples were investigated. The surface mo...mg-Yb203 electrical contact materials were fabricated by spark plasma sintefing (SPS). The effects of silver powder particle size on the microstructure and properties of the samples were investigated. The surface morphologies of the sintered samples were examined by optical microscope (OM), and the fracture morphologies were observed by scanning electron microscopy (SEM). The physical and mechanical properties such as density, electrical resistivity, microhardness, and tensile strength were also tested. The results show that the silver powder particle size has evident effects on the sintered materials. Comparing with coarse silver powder (5 ktm), homogeneous and fme microstmcture was obtained by fine silver powder (_〈0.5-1am). At the same time, the electrical conductivity, microhardness, and tensile strength of the sin- tered samples with fine silver powder were higher than those of the samples with coarse silver powder. However, silver powder particle size has little influence on the relative densities, which of all samples (both by free and coarse silver powders) is more than 95%. The fracture characteristics are ductile.展开更多
A 92WC-8Co powder mixture with 33 nm WC grains was prepared by strengthening ball milling and was then sintered by spark plasma sintering (SPS) at 1000-1200℃ for 5-18 rain under 10-25 kN, respectively. Movement of ...A 92WC-8Co powder mixture with 33 nm WC grains was prepared by strengthening ball milling and was then sintered by spark plasma sintering (SPS) at 1000-1200℃ for 5-18 rain under 10-25 kN, respectively. Movement of the position of low punch shown shrinkage of the sintered body began above 800℃. The shrinkage slowly rose as the temperature rose from 800 to 1000℃ and then quickly rose at above 1000℃ and then gradually rose at above 1150℃. The densities of the samples increased with an increase in sintering temperature, rapidly below 1100℃, and then gradually above 1100℃. WC grains grow gradually with increasing sintering temperature. The powder was sintered to near full density at 1100℃ for 5 rain under 10 kN. The best result of the sample with 275 nm WC grains and no pores was obtained at 1150℃ under 10 kN for 5 rain. The research found the graphite die had a function of carburization, which could compensate the sintered body for the lack of carbon, and had the normal microstructure.展开更多
Diamond/metal composites with 50 vol.% diamond have been produced by spark plasma sintering(SPS) using pure Ag as a matrix and diamond particles as reinforcement.Three kinds of powder mixing processes were used to p...Diamond/metal composites with 50 vol.% diamond have been produced by spark plasma sintering(SPS) using pure Ag as a matrix and diamond particles as reinforcement.Three kinds of powder mixing processes were used to prepare the mixture of diamond/Ag powders:dry mixing without milling medium,wet mixing and magnetic blending.Subsequently,they were all consolidated by SPS at various processing parameters to produce bulk diamond/Ag composites.Then samples were heat treated in order to obtain a higher thermal conductivity.The effect of processing parameters on the morphologies of the mixed powders,the microstructure and the thermal conductivity of the composites were investigated by comparing the experimental data.It reveals that particles were easy to agglomerate and the distribution of mixed powders was inhomogeneous by dry mixing method,and wet mixing method is too complex.The most favorable mixing process is magnetic blending by which the powders can be homogenously mixed and the composites prepared by optimized SPS processing parameters can obtain the highest relative density and the best thermal conductivity among the composites prepared by different processes.The magnetic blending diamond/Ag composites even have a 23% increase in thermal conductivity compared with pure silver sintered by SPS.展开更多
A high Nb containing TiA1 alloy was prepared from the pre-alloyed powder of Ti-45Al-8.5Nb-0.2B-0.2W-0.02Y (at%) by spark plasma sintering (SPS). Its high-temperature mechanical properties and compressive deformati...A high Nb containing TiA1 alloy was prepared from the pre-alloyed powder of Ti-45Al-8.5Nb-0.2B-0.2W-0.02Y (at%) by spark plasma sintering (SPS). Its high-temperature mechanical properties and compressive deformation behavior were investigated in a temperature range of 700 to 1050℃ and a strain rate range of 0.002 to 0.2 s 1. The results show that the high-temperature mechanical properties of the high Nb containing TiA1 alloy are sensitive to deformation temperature and strain rate, and the sensitivity to strain rate tends to rise with the deformation temperature increasing. The hot workability of the alloy is good at temperatures higher than 900℃, while fracture occurs at lower temperatures. The flow curves of the samples compressed at or above 900℃ exhibit obvious flow softening after the peak stress. Un- der the deformation condition of 900-1050℃ and 0.002-0.2 s 1, the interrelations of peak flow stress, strain rate, and deformation tempera- ture follow the Arrhenius' equation modified by a hyperbolic sine function with a stress exponent of 5.99 and an apparent activation energy of 441.2 kJ.mol-1.展开更多
The relative density of WC-Co cemented carbides during spark plasma sintering(SPS) was analyzed.Based on the change in displacement of the ram in the SPS system,the relative densities in the sintering process can be...The relative density of WC-Co cemented carbides during spark plasma sintering(SPS) was analyzed.Based on the change in displacement of the ram in the SPS system,the relative densities in the sintering process can be achieved at different temperatures.The results indicated that densification of the samples started at near 900°C,the density rapidly reached its maximum at the increasing temperature stage,in which the temperature was lower than the sintering temperature of 1200°C,and most of the densification took place in the stage.Besides,the theoretical values were consistent with the experimental results.展开更多
In this study, we have investigated how the dielectric loss tangent and permittivity of AlN ceramics are affected by factors such as powder mixing methods, milling time, sintering temperature, and the addition of a se...In this study, we have investigated how the dielectric loss tangent and permittivity of AlN ceramics are affected by factors such as powder mixing methods, milling time, sintering temperature, and the addition of a second conductive phase. All ceramic samples were pre-pared by spark plasma sintering (SPS) under a pressure of 30 MPa. AlN composite ceramics sintered with 30wt%-40wt%SiC at 1600℃ for 5 min exhibited the best dielectric loss tangent, which is greater than 0.3. In addition to AlN and β-SiC, the samples also contained 2H-SiC and Fe5Si3, as detected by X-ray difraction (XRD). The relative densities of the sintered ceramics were higher than 93%. Experimental results indicate that nano-SiC has a strong capability of absorbing electromagnetic waves. The dielectric constant and dielectric loss of AlN-SiC ce-ramics with the same content of SiC decreased as the frequency of electromagnetic waves increased from 1 kHz to 1 MHz.展开更多
An equiatomic FeSiBAlNi amorphous high-entropy alloy (HEA) was fabricated by mechanical alloying (MA). A fully amorphous phase was obtained in the FeSiBAlNi HEA after 240 h of MA. The bulk FeSiBAlNi samples were s...An equiatomic FeSiBAlNi amorphous high-entropy alloy (HEA) was fabricated by mechanical alloying (MA). A fully amorphous phase was obtained in the FeSiBAlNi HEA after 240 h of MA. The bulk FeSiBAlNi samples were sintered by spark plasma sintering (SPS) at 520 and 1080℃ under a pressure of 80 MPa. The sample sintered at 520℃ exhibited an amorphous composite structure comprising solid-solution phases (body-centered cubic (bcc) and face-centered cubic (fee) phases). When the as-milled amorphous HEA was consoli- dated at 1080℃, another fcc phase appeared and the amorphous phase disappeared. The sample sintered by SPS at 1080℃ exhibited a slightly higher melting temperature compared with those of the as-milled alloy and the bulk sample sintered at 520℃. The corrosion behav- iors of the as-sintered samples were investigated by potentiodynamic polarization measurements and immersion tests in seawater solution. The results showed that the HEA obtained by SPS at 1080℃ exhibited better corrosion resistance than that obtained by SPS at 520℃.展开更多
Despite the importance of aluminum alloys as candidate materials for applications in aerospace and automotive industries, very little work has been published on spark plasma and microwave processing of aluminum alloys...Despite the importance of aluminum alloys as candidate materials for applications in aerospace and automotive industries, very little work has been published on spark plasma and microwave processing of aluminum alloys. In the present work, the possibility was explored to process A12124 and A16061 alloys by spark plasma and microwave sintering techniques, and the microstructures and properties were compared. The alloys were sintered for 20 rain at 400, 450, and 500℃. It is found that compared to microwave sintering, spark plasma sintering is an effective way to obtain homogenous, dense, and hard alloys. Fully dense (100%) A16061 and A12124 alloys were obtained by spark plasma sintering for 20 rain at 450 and 500℃, respectively. Maximum relative densities were achieved for A16061 (92.52%) and A12124 (93.52%) alloys by microwave sintering at 500℃for 20 min. The Vickers microhardness of spark plasma sintered samples increases with the increase of sintering temperature from 400 to 500℃, and reaches the values of Hv 70.16 and Hv 117.10 for A16061 and A12124 alloys, respectively. For microwave siutered samples, the microhardness increases with the increase of sintering temperature from 400 to 450℃, and then decreases with the further increase of sintering temperature to 500~C.展开更多
Zirconia powders doped with yttrium prepared by special liquid-phase precipitation method were sintered by spark plasma sintering (SPS) to obtain high performance samples. The microstructure, phase composition, and ...Zirconia powders doped with yttrium prepared by special liquid-phase precipitation method were sintered by spark plasma sintering (SPS) to obtain high performance samples. The microstructure, phase composition, and mechanical properties of the samples were studied. The results of X-ray diffraction (XRD), Raman spectrum, and transmission electron microscope (TEM) show that the phase is tetragonal. The powders with large surface area and high sintering activity, due to small crystallite size, could be densified at 1100℃. The highest relative density of the sample obtained at 1300℃ is higher than 99% (the tetragonal phase is 6.08 g/cm^3). The Hv and KIC are 13.76 GPa and 15.4 MPa.m^1/2, respectively.展开更多
Melt-spun ribbons with nominal composition of Nd14–xFe76+xCo3Zr1B6(x=0,0.5,1) were consolidated into isotropic bulk magnets by spark plasma sintering method.It was found that the Nd content and sintering temperature ...Melt-spun ribbons with nominal composition of Nd14–xFe76+xCo3Zr1B6(x=0,0.5,1) were consolidated into isotropic bulk magnets by spark plasma sintering method.It was found that the Nd content and sintering temperature had significant influence on the density and magnetic properties of the sintered magnets.Homogeneous microstructure and fine grain(50–100 nm) were obtained when sintering below 700 ℃,and the initial magnetization curve showed that the coercivity was controlled by the pinning mechanism.However,ab...展开更多
A 0.3wt%graphene nanoplatelets(GNPs)reinforced 7075 aluminum alloy matrix(7075 Al)composite was fabricated by spark plasma sintering and its strength and wear resistance were investigated.The microstructures of the in...A 0.3wt%graphene nanoplatelets(GNPs)reinforced 7075 aluminum alloy matrix(7075 Al)composite was fabricated by spark plasma sintering and its strength and wear resistance were investigated.The microstructures of the internal structure,the friction surface,and the wear debris were characterized by scanning electron microscopy,X-ray diffraction,and Raman spectroscopy.Compared with the original 7075 aluminum alloy,the hardness and elastic modulus of the 7075 Al/GNPs composite were found to have increased by 29%and 36%,respectively.The results of tribological experiments indicated that the composite also exhibited a lower wear rate than the original 7075 aluminum alloy.展开更多
基金supported by National Natural Science Foundation of China(Nos.51677083 and 51377075)Postgraduate Research and Practice Innovation Program of Jiangsu Province(SJCX18_0340)
文摘Atmospheric pressure low-temperature plasma is a promising tool in biomedicine applications including blood coagulation,bacterial inactivation,sterilization,and cancer treatment,due to its high chemical activity and limited thermal damage.It is of great importance to develop portable plasma sources that are safe to human touch and suitable for outdoor and household operation.In this work,a portable and rechargeable low-temperature plasma spark discharge device(130 mm×80 mm×35 mm,300 g)was designed.The discharge frequency and plume length were optimized by the selection of resistance,capacitance,electrode gap,and ground electrode aperture.Results show that the spark plasma plume is generated with a length of 12 mm and a frequency of 10 Hz at a capacitance of 0.33μF.resistance of 1 MΩ,electrode gap of 2 mm,and ground electrode aperture of 1.5 mm.Biological tests indicate that the plasma produced by this device contains abundant reactive species,which can be applied in plasma biomedicine,including daily sterilization and wound healing.
文摘Within the past ten years,spark plasma sintering(SPS)has become an increasingly popular process for Mg manufacturing.In the SPS process,interparticle diffusion of compressed particles is rapidly achieved due to the concept of Joule heating.Compared to traditional and additive manufacturing(AM)techniques,SPS gives unique control of the structural and microstructural features of Mg components.By doing so,their mechanical,tribological,and corrosion properties can be tailored.Although great advancements in this field have been made,these pieces of knowledge are scattered and have not been contextualized into a single work.The motivation of this work is to address this scientific gap and to provide a groundwork for understanding the basics of SPS manufacturing for Mg.To do so,the existing body of SPS Mg literature was first surveyed,with a focus on their structural formation and degradation mechanisms.It was found that successful Mg SPS fabrication highly depended on the processing temperature,particle size,and particle crystallinity.The addition of metal and ceramic composites also affected their microstructural features due to the Zener pinning effect.In degradative environments,their performance depends on their structural features and whether they have secondary phased composites.In industrial applications,SPS'd Mg was found to have great potential in biomedical,hydrogen storage,battery,automotive,and recycling sectors.The prospects to advance the field include using Mg as a doping agent for crystallite size refinement and using bulk metallic Mg-based glass powders for amorphous SPS components.Despite these findings,the interactions of multi-composites on the processing-structure-property relationships of SPS Mg is not well understood.In total,this work will provide a useful direction in the SPS field and serve as a milestone for future Mg-based SPS manufacturing.
基金Funded by the Primary Research and Development Plan of Jiangsu Province(No.BE2016175)。
文摘In this study,a single-doped phosphors yttrium aluminum garnet(Y_(3)Al_(5)O_(12),YAG):Ce^(3+),single-doped YAG:Sc^(3+),and double-doped phosphors YAG:Ce^(3+),Sc^(3+) were prepared by spark plasma sintering(SPS)(lower than 1 200℃).The characteristics of synthesized phosphors were determined using scanning electron microscopy(SEM),X-ray diffraction(XRD),and fluorescence spectroscopy.During SPS,the lattice structure of YAG was maintained by the added Ce^(3+) and Sc^(3+).The emission wavelength of YAG:Ce^(3+) prepared from SPS(425-700 nm) was wider compared to that of YAG:Ce^(3+) prepared from high-temperature solid-state reaction(HSSR)(500-700 nm).The incorporation of low-dose Sc^(3+) in YAG:Ce^(3+) moved the emission peak towards the short wavelength.
基金supported by the National Science Foundation under Grant No.CMMI-1762190The research was performed in part in the Nebraska Nanoscale Facility:National Nanotechnology Coordinated Infrastructure and the Nebraska Center for Materials and Nanoscience (and/or NERCF),which are supported by the National Science Foundation under Award ECCS:2025298+1 种基金the Nebraska Research Initiativesupported by the U.S.Department of Energy,Office of Nuclear Energy under DOE Idaho Operations Office Contract DE-AC07-051D14517 as part of a Nuclear Science User Facilities experiment。
文摘W-based WTaVCr refractory high entropy alloys (RHEA) may be novel and promising candidate materials for plasma facing components in the first wall and diverter in fusion reactors. This alloy has been developed by a powder metallurgy process combining mechanical alloying and spark plasma sintering (SPS). The SPSed samples contained two phases, in which the matrix is RHEA with a body-centered cubic structure, while the oxide phase was most likely Ta2VO6through a combined analysis of X-ray diffraction (XRD),energy-dispersive spectroscopy (EDS), and selected area electron diffraction (SAED). The higher oxygen affinity of Ta and V may explain the preferential formation of their oxide phases based on thermodynamic calculations. Electron backscatter diffraction (EBSD) revealed an average grain size of 6.2μm. WTaVCr RHEA showed a peak compressive strength of 2997 MPa at room temperature and much higher micro-and nano-hardness than W and other W-based RHEAs in the literature. Their high Rockwell hardness can be retained to at least 1000°C.
基金financially supported by the Guangdong Basic and Applied Basic Research Foundation,China (No.2021A1515110202)the Natural Science Foundation Program of Beijing,China (Nos.2224104,2202031,2174079+6 种基金2162027)the National Natural Science Foundation Program of China (Nos.52131307,52130407,52071013,52104359,51774035,and 52174344)the Scientific and Technological Innovation Foundation of Foshan,China (No.BK21BE007)the National Key Research and Development Program of China (Nos.2021YFB3701900,2022YFB3705400,and 2022YFB3708800)the Beijing Municipal Science & Technology Commission,Administrative Commission of Zhongguancun Science Park,China (No.Z221100005822001)the S&T Program of Hebei,China(No.20311001D)the Fundamental Research Funds for the Central Universities (Nos.FRF-IDRY-20-022,FRF-TP-20-032A2,FRF-TP-20-100A1Z,and FRF-IDRY-22-030)。
文摘How to increase strength without sacrificing ductility has been developed as a key goal in the manufacture of high-performance metals or alloys. Herein, the double-nanophase intragranular yttrium oxide dispersion strengthened iron alloy with high strength and appreciable ductility was fabricated by solution combustion route and subsequent spark plasma sintering, and the influences of yttrium oxide content and sintering temperature on microstructures and mechanical properties were investigated. The results show at the same sintering temperature,with the increase of yttrium oxide content, the relative density of the sintered alloy decreases and the strength increases. For Fe–2wt%Y_(2)O_(3)alloy, as the sintering temperature increases gradually, the compressive strength decreases, while the strain-to-failure increases. The Fe–2wt%Y_(2)O_(3)alloy with 15.5 nm Y_(2)O_(3)particles uniformly distributed into the 147.5 nm iron grain interior sintered at 650℃ presents a high ultimate compressive strength of 1.86 GPa and large strain-to-failure of 29%. The grain boundary strengthening and intragranular second-phase particle dispersion strengthening are the main dominant mechanisms to enhance the mechanical properties of the alloy.
基金supported by National Natural Science Foundation of China(No.51176001)
文摘In this paper,the characteristics of detonation combustion ignited by AC-driven non-thermal plasma and spark plug in air/acetylene mixture have been compared in a doubletube experiment system.The two tubes had the same structure,and their closed ends were installed with a plasma generator and a spark plug,respectively.The propagation characteristics of the flame were measured by pressure sensors and ion probes.The experiment results show that,compared with a spark plug,the non-thermal plasma obviously broadened the range of equivalence ratio when the detonation wave could develop successfully,it also heightened the pressure value of detonation wave.Meanwhile,the detonation wave development time and the entire flame propagation time were reduced by half.All of these advantages benefited from the larger ignition volume when a non-thermal plasma was applied.
基金supported by the National Natural Science Foundation of China(No.50971020)
文摘Spark plasma sintering was used to fabricate Al/diamond composites.The effect of sintering temperature on the microstructure and thermal conductivity(TC) of the composites was investigated with the combination of experimental results and theoretical analysis.The composite sintered at 550℃shows high relative density and strong interfacial bonding,whereas the composites sintered at lower(520CC) and higher(580-600℃) temperatures indicate no interfacial bonding and poor interfacial bonding,respectively.High relative density and strong interfacial bonding can maximize the thermal conductivity of Al/diamond composites,and taking both effects of particle shape and inhomogeneous interfacial thermal conductance into consideration can give a fairly good prediction of composites' thermal conduction properties.
基金This work was financially supported by the National Natural Science Foundation of China (No. 50174007)
文摘Mechanically activated W-Cu powders were sintered by a spark plasma sinteringsystem (SPS) in order to develop a new process and improve the properties of the alloy. Propertiessuch as density and hardness were measured. The microstructures of the sintered W-Cu alloy sampleswere observed by SEM (scanning electron microscope). The results show that spark plasma sinteringcan obviously lower the sintering temperature and increase the density of the alloy. This processcan also improve the hardness of the alloy. SPS is an effective method to obtain W-Cu powders withhigh density and superior physical properties.
基金financially supported by Natural Science Foundation of China (No.51071059 and No.50971052)the Fundamental Research Funds for the Central Universities (No.HIT.KLOF.2010005)
文摘Carbon nanotube (CNT)-reinforced TiNi matrix composites were synthesized by spark plasma sintering (SPS) employing elemental powders.The phase structure,morphology and transformation behaviors were studied.It was found that thermoelastic martensitic transformation be-haviors could be observed from the samples sintered above 800 ℃ even with a short sintering time (5min),and the transformation tempera-tures gradually increased with increasing sintering temperature because of more Ti-rich TiNi phase formation.Although decreasing the sin-tering temperature and time to 700 ℃ and 5min could not protect defective MWCNTs from reacting with Ti,still-perfect MWCNTs re-mained in the specimens sintered at 900 ℃.This method is expected to supply a basis for preparing CNT-reinforced TiNi composites.
文摘mg-Yb203 electrical contact materials were fabricated by spark plasma sintefing (SPS). The effects of silver powder particle size on the microstructure and properties of the samples were investigated. The surface morphologies of the sintered samples were examined by optical microscope (OM), and the fracture morphologies were observed by scanning electron microscopy (SEM). The physical and mechanical properties such as density, electrical resistivity, microhardness, and tensile strength were also tested. The results show that the silver powder particle size has evident effects on the sintered materials. Comparing with coarse silver powder (5 ktm), homogeneous and fme microstmcture was obtained by fine silver powder (_〈0.5-1am). At the same time, the electrical conductivity, microhardness, and tensile strength of the sin- tered samples with fine silver powder were higher than those of the samples with coarse silver powder. However, silver powder particle size has little influence on the relative densities, which of all samples (both by free and coarse silver powders) is more than 95%. The fracture characteristics are ductile.
文摘A 92WC-8Co powder mixture with 33 nm WC grains was prepared by strengthening ball milling and was then sintered by spark plasma sintering (SPS) at 1000-1200℃ for 5-18 rain under 10-25 kN, respectively. Movement of the position of low punch shown shrinkage of the sintered body began above 800℃. The shrinkage slowly rose as the temperature rose from 800 to 1000℃ and then quickly rose at above 1000℃ and then gradually rose at above 1150℃. The densities of the samples increased with an increase in sintering temperature, rapidly below 1100℃, and then gradually above 1100℃. WC grains grow gradually with increasing sintering temperature. The powder was sintered to near full density at 1100℃ for 5 rain under 10 kN. The best result of the sample with 275 nm WC grains and no pores was obtained at 1150℃ under 10 kN for 5 rain. The research found the graphite die had a function of carburization, which could compensate the sintered body for the lack of carbon, and had the normal microstructure.
基金supported by the National Nature Science Foundation of China (No.50971020)
文摘Diamond/metal composites with 50 vol.% diamond have been produced by spark plasma sintering(SPS) using pure Ag as a matrix and diamond particles as reinforcement.Three kinds of powder mixing processes were used to prepare the mixture of diamond/Ag powders:dry mixing without milling medium,wet mixing and magnetic blending.Subsequently,they were all consolidated by SPS at various processing parameters to produce bulk diamond/Ag composites.Then samples were heat treated in order to obtain a higher thermal conductivity.The effect of processing parameters on the morphologies of the mixed powders,the microstructure and the thermal conductivity of the composites were investigated by comparing the experimental data.It reveals that particles were easy to agglomerate and the distribution of mixed powders was inhomogeneous by dry mixing method,and wet mixing method is too complex.The most favorable mixing process is magnetic blending by which the powders can be homogenously mixed and the composites prepared by optimized SPS processing parameters can obtain the highest relative density and the best thermal conductivity among the composites prepared by different processes.The magnetic blending diamond/Ag composites even have a 23% increase in thermal conductivity compared with pure silver sintered by SPS.
基金supported by the National Natural Science Foundation of China (No.50974017)Research Fund for the Doctoral Program of Higher Education of China (No.20110006120023)
文摘A high Nb containing TiA1 alloy was prepared from the pre-alloyed powder of Ti-45Al-8.5Nb-0.2B-0.2W-0.02Y (at%) by spark plasma sintering (SPS). Its high-temperature mechanical properties and compressive deformation behavior were investigated in a temperature range of 700 to 1050℃ and a strain rate range of 0.002 to 0.2 s 1. The results show that the high-temperature mechanical properties of the high Nb containing TiA1 alloy are sensitive to deformation temperature and strain rate, and the sensitivity to strain rate tends to rise with the deformation temperature increasing. The hot workability of the alloy is good at temperatures higher than 900℃, while fracture occurs at lower temperatures. The flow curves of the samples compressed at or above 900℃ exhibit obvious flow softening after the peak stress. Un- der the deformation condition of 900-1050℃ and 0.002-0.2 s 1, the interrelations of peak flow stress, strain rate, and deformation tempera- ture follow the Arrhenius' equation modified by a hyperbolic sine function with a stress exponent of 5.99 and an apparent activation energy of 441.2 kJ.mol-1.
文摘The relative density of WC-Co cemented carbides during spark plasma sintering(SPS) was analyzed.Based on the change in displacement of the ram in the SPS system,the relative densities in the sintering process can be achieved at different temperatures.The results indicated that densification of the samples started at near 900°C,the density rapidly reached its maximum at the increasing temperature stage,in which the temperature was lower than the sintering temperature of 1200°C,and most of the densification took place in the stage.Besides,the theoretical values were consistent with the experimental results.
基金financially supported by the International S&T Cooperation Program of China(No.2010DFR50360)
文摘In this study, we have investigated how the dielectric loss tangent and permittivity of AlN ceramics are affected by factors such as powder mixing methods, milling time, sintering temperature, and the addition of a second conductive phase. All ceramic samples were pre-pared by spark plasma sintering (SPS) under a pressure of 30 MPa. AlN composite ceramics sintered with 30wt%-40wt%SiC at 1600℃ for 5 min exhibited the best dielectric loss tangent, which is greater than 0.3. In addition to AlN and β-SiC, the samples also contained 2H-SiC and Fe5Si3, as detected by X-ray difraction (XRD). The relative densities of the sintered ceramics were higher than 93%. Experimental results indicate that nano-SiC has a strong capability of absorbing electromagnetic waves. The dielectric constant and dielectric loss of AlN-SiC ce-ramics with the same content of SiC decreased as the frequency of electromagnetic waves increased from 1 kHz to 1 MHz.
基金the Natural Science Foundation of China (No. 51171072)the Excellent Middle-age and Young Scientists Research Award Foundation of Shandong Province (No. BS2012CL002)the International Cooperation Training Project of Excellent Young and Middle-aged Teachers of Shandong Province, China
文摘An equiatomic FeSiBAlNi amorphous high-entropy alloy (HEA) was fabricated by mechanical alloying (MA). A fully amorphous phase was obtained in the FeSiBAlNi HEA after 240 h of MA. The bulk FeSiBAlNi samples were sintered by spark plasma sintering (SPS) at 520 and 1080℃ under a pressure of 80 MPa. The sample sintered at 520℃ exhibited an amorphous composite structure comprising solid-solution phases (body-centered cubic (bcc) and face-centered cubic (fee) phases). When the as-milled amorphous HEA was consoli- dated at 1080℃, another fcc phase appeared and the amorphous phase disappeared. The sample sintered by SPS at 1080℃ exhibited a slightly higher melting temperature compared with those of the as-milled alloy and the bulk sample sintered at 520℃. The corrosion behav- iors of the as-sintered samples were investigated by potentiodynamic polarization measurements and immersion tests in seawater solution. The results showed that the HEA obtained by SPS at 1080℃ exhibited better corrosion resistance than that obtained by SPS at 520℃.
基金supported by the King Abdul Aziz City for Science and Technology (KACST) (No. ARP-28-122)
文摘Despite the importance of aluminum alloys as candidate materials for applications in aerospace and automotive industries, very little work has been published on spark plasma and microwave processing of aluminum alloys. In the present work, the possibility was explored to process A12124 and A16061 alloys by spark plasma and microwave sintering techniques, and the microstructures and properties were compared. The alloys were sintered for 20 rain at 400, 450, and 500℃. It is found that compared to microwave sintering, spark plasma sintering is an effective way to obtain homogenous, dense, and hard alloys. Fully dense (100%) A16061 and A12124 alloys were obtained by spark plasma sintering for 20 rain at 450 and 500℃, respectively. Maximum relative densities were achieved for A16061 (92.52%) and A12124 (93.52%) alloys by microwave sintering at 500℃for 20 min. The Vickers microhardness of spark plasma sintered samples increases with the increase of sintering temperature from 400 to 500℃, and reaches the values of Hv 70.16 and Hv 117.10 for A16061 and A12124 alloys, respectively. For microwave siutered samples, the microhardness increases with the increase of sintering temperature from 400 to 450℃, and then decreases with the further increase of sintering temperature to 500~C.
文摘Zirconia powders doped with yttrium prepared by special liquid-phase precipitation method were sintered by spark plasma sintering (SPS) to obtain high performance samples. The microstructure, phase composition, and mechanical properties of the samples were studied. The results of X-ray diffraction (XRD), Raman spectrum, and transmission electron microscope (TEM) show that the phase is tetragonal. The powders with large surface area and high sintering activity, due to small crystallite size, could be densified at 1100℃. The highest relative density of the sample obtained at 1300℃ is higher than 99% (the tetragonal phase is 6.08 g/cm^3). The Hv and KIC are 13.76 GPa and 15.4 MPa.m^1/2, respectively.
基金supported by the National Natural Science Foundation of China (50801049)
文摘Melt-spun ribbons with nominal composition of Nd14–xFe76+xCo3Zr1B6(x=0,0.5,1) were consolidated into isotropic bulk magnets by spark plasma sintering method.It was found that the Nd content and sintering temperature had significant influence on the density and magnetic properties of the sintered magnets.Homogeneous microstructure and fine grain(50–100 nm) were obtained when sintering below 700 ℃,and the initial magnetization curve showed that the coercivity was controlled by the pinning mechanism.However,ab...
基金This work was financially supported by the Program for New Century Excellent Talents in University(No.NCET-11-0951).
文摘A 0.3wt%graphene nanoplatelets(GNPs)reinforced 7075 aluminum alloy matrix(7075 Al)composite was fabricated by spark plasma sintering and its strength and wear resistance were investigated.The microstructures of the internal structure,the friction surface,and the wear debris were characterized by scanning electron microscopy,X-ray diffraction,and Raman spectroscopy.Compared with the original 7075 aluminum alloy,the hardness and elastic modulus of the 7075 Al/GNPs composite were found to have increased by 29%and 36%,respectively.The results of tribological experiments indicated that the composite also exhibited a lower wear rate than the original 7075 aluminum alloy.