The purpose of this paper is to examine the effect of processing parameters and subsequent heat treatments on the microstructures and bonding strengths of Ti-6Al-4V/AA1050 laminations formed via a non-equal channel la...The purpose of this paper is to examine the effect of processing parameters and subsequent heat treatments on the microstructures and bonding strengths of Ti-6Al-4V/AA1050 laminations formed via a non-equal channel lateral co-extrusion process.The microstructural evolution and growth mechanism in the diffusion layer were discussed further to optimize the bonding quality by appropriately adjusting process parameters.Scanning electron microscopes(SEM),energy dispersive spectrometer(EDS),and X-ray diffraction(XRD)were used to characterize interfacial diffusion layers.The shear test was used to determine the mechanical properties of the interfacial diffusion layer.The experimental results indicate that it is possible to co-extrusion Ti-6Al-4V/AA1050 compound profiles using non-equal channel lateral co-extrusion.Different heat treatment processes affect the thickness of the diffusion layer.When the temperature and time of heat treatment increase,the thickness of the reaction layers increases dramatically.Additionally,the shear strength of the Ti-6Al-4V/AA1050 composite interface is proportional to the diffusion layer thickness.It is observed that a medium interface thickness results in superior mechanical performance when compared to neither a greater nor a lesser interface thickness.Microstructural characterization of all heat treatments reveals that the only intermetallic compound observed in the diffusion layers is TiAl_(3).Due to the inter-diffusion of Ti and Al atoms,the TiAl_(3) layer grows primarily at AA1050/TiAl_(3) interfaces.展开更多
The phase transformation activation energy of the Cu61.13Zn33.94A14.93 alloys, which were treated at 4 GPa and 700 ℃ for 15 minutes, was calculated by means of differential scanning calorimetry curves obtained at var...The phase transformation activation energy of the Cu61.13Zn33.94A14.93 alloys, which were treated at 4 GPa and 700 ℃ for 15 minutes, was calculated by means of differential scanning calorimetry curves obtained at various heating and cooling rates. Then, the effects of high-pressure heat treatments on the solid-state phase transformation and the microstructures of Cu61.13Zn33.94A14.93 alloys were investigated. The results show that high-pressure heat treatments can refine the grains and can change the preferred orientation from （111） to （200） of α phase. Compared with the as-cast alloy, the sample with high-pressure heat treatment has finer grains, lower β＇→β and/β→β＇ transformation temperature and activation energy. Furthermore, we found that high cooling rate favours the formation of fine needle-like α phase in the range of 5-20℃/min.展开更多
Pd-based nanocatalyst is a potential oxygen reduction oxidation(ORR)catalyst because of its high activity in alkaline medium and low cost.In this work,bimetallic Pd Au nanocatalysts are prepared by one-pot hydrotherma...Pd-based nanocatalyst is a potential oxygen reduction oxidation(ORR)catalyst because of its high activity in alkaline medium and low cost.In this work,bimetallic Pd Au nanocatalysts are prepared by one-pot hydrothermal method using triblock pluronic copolymers,poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)(PEO19-PPO69-PEO19)(P123)as reducer and stabilizer,and heat-treatment method is applied to regulate catalyst structure and improve catalyst activity.The results show that the heat treatment can agglomerate the catalyst to a certain extent,but effectively improve the crystallinity and alloying degree of the catalyst.The ORR performance of the Pd Au nanocatalysts obtained under different heat treatment conditions is systematically investigated.Compared with commercial Pd black and Pd Au catalyst before heat treatment,the ORR performance of Au Pd nanocatalyst obtained after heat treatment for one hour at 500℃ has been enhanced.The Pd Au nanocatalysts after heat treatment also display enhanced anti-methanol toxicity ability in acidic medium.展开更多
Cu-Zn-Al slurry catalysts were prepared using a complete liquid-phase preparation technology under different heat treatment atmospheres.The catalysts were characterized using X-ray diffraction,X-ray photoelectron spec...Cu-Zn-Al slurry catalysts were prepared using a complete liquid-phase preparation technology under different heat treatment atmospheres.The catalysts were characterized using X-ray diffraction,X-ray photoelectron spectroscope,and N2 adsorption-desorption.Their application in the single-step synthesis of dimethyl ether from syngas was also investigated.The results indicate that the type of heat treatment atmosphere has an influence on the Cu species and the Cu0/Cu＋ ratio on the catalyst surface.Moreover,the final Cu/Zn ratio on the catalyst surface is mainly dependent on the composition and reaction environment of the catalyst and less on the type of heat treatment atmosphere.The prepared catalysts can suppress sintering of active sites at high temperatures,and the type of heat treatment atmosphere mainly affects the capability of the catalyst for methanol synthesis.The catalysts perform best using N2 as the heat treatment atmosphere.展开更多
We fabricated complex microfluidic devices in silica glass by water-assisted femtosecond laser ablation and sub- sequent heat treatment. The experimental results show that after heat treatment, the diameter of the mic...We fabricated complex microfluidic devices in silica glass by water-assisted femtosecond laser ablation and sub- sequent heat treatment. The experimental results show that after heat treatment, the diameter of the microehannels is significantly reduced and the internal surface roughness is improved. The diameters of the fabricated microehannels can be modulated by changing the annealing temperature and the annealing time. During annealing, the temperature affects the diameter and shape of the protrusions in microfluidic devices very strongly, and these changes are mainly caused by uniform expansion and the action of surface tension.展开更多
Wood has no inherent natural resistance against agents of biodegradation. We evaluated the effects of metal bath heat treatment(MBHT) on decay resistance and dimensional stability of Chinese parasol(Firmiana simplex) ...Wood has no inherent natural resistance against agents of biodegradation. We evaluated the effects of metal bath heat treatment(MBHT) on decay resistance and dimensional stability of Chinese parasol(Firmiana simplex) and Chinese fir(Cunninghamia lanceolata) wood. A low melting point alloy was used as heating medium in the treatment of the wood samples at 150, 180, and 210 °C for2, 4, and 8 h. Heat-treated and control samples were exposed to brown rot fungus(Poria placenta) and white rot fungus(Coriolus versicolor) for decay resistance testing and anti-swelling efficiency(ASE). The improved decay resistance with increase temperatures with low mass losses of 7.3 and 7.3% for F. simplex, and 3.9 and 3.6% for C.lanceolata at 210 °C for 8 h against Coriolus versicolor and Poria placenta, respectively. ASE indicated that MBHT contributed to improved dimensional stability of both wood species after treatment. Scanning electron micrograph results indicate that metal bath-treated samples showed strong decay resistance. Therefore, our approach to thermally modify wood should be explored to overcome the energy utilization by using low melting point alloy for the heat treatment of wood.展开更多
Pinus massoniana L. was thermally treated with low melting point alloy as heating medium to investigate the strength properties changes. Contact angle, color and scanning electron microscopy were recorded to assess th...Pinus massoniana L. was thermally treated with low melting point alloy as heating medium to investigate the strength properties changes. Contact angle, color and scanning electron microscopy were recorded to assess the effectiveness of the treatment. Samples were pre-treated in a micro-wave for 5 min followed by metal bath heat treatment at 150, 180, and 210 °C for 2, 4, and 8 h,respectively. Strength properties of metal bath treated wood were decreased with increase temperature and time.Density, modulus of rupture, impact bending, modulus of elasticity were reduced for all treatments. Maximum compressive strength slightly increased at 150 °C for 4 h followed by gradual reduction. The Janka hardness was reduced in the tangential and radial directions. Treatment of the wood at 210 °C for 8 h caused the wood to become brittle and rupture. The contact angle was considerably higher after thermal treatment. The color of the wood became darker with increasing temperature of thermal treatment. Micrographs of the heat-treated samples showed damage to the cell wall with increase in temperature. Metal bath heat treatment of wood was carried out successfully and some strength properties were reduced.展开更多
In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosi...In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40 Cr Mn Si B steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thickness and the number of the circumferential divisions. The results show that as the tempering temperature was increased from 350 to 600 ℃, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface.展开更多
Natural foods,such as whole pulses,are recommended in the dietary guidelines of the US and China.The plant cell wall structure in whole pulses has important implications for the nutritional functionalities of starch.I...Natural foods,such as whole pulses,are recommended in the dietary guidelines of the US and China.The plant cell wall structure in whole pulses has important implications for the nutritional functionalities of starch.In this study,garbanzo bean cells with varying degrees of cell wall integrity were subjected to dry heat treatment(DHT)and used to elucidate the food structure-starch digestion properties of pulse food.The morphological features suggested that all cell samples do not exhibit remarkable changes after being subjected to DHT.Molecular rearrangement and the crystallite disruption of starch granules entrapped in cells occurred during DHT as assessed by the crystal structure and thermal properties.DHT decreased the inhibitory effects of enzymes of both the soluble and insoluble components,but the digestion rate and extent of slightly and highly damaged cell samples did not exhibit significant differences compared with their native counterparts.We concluded that the starch digestion of pulse cotyledon cells is primarily determined by the intactness of the cellular structure.This study reveals the role of food structure on the ability to retain the desirable nutritional properties of starch after subjection to physical modification.展开更多
In this work,Bi2Te3 films（250 nm） are fabricated on Si O2/Si substrates by radio frequency（RF） magnetron sputtering at room temperature,and the prepared films are annealed over the temperature range of 200 °C...In this work,Bi2Te3 films（250 nm） are fabricated on Si O2/Si substrates by radio frequency（RF） magnetron sputtering at room temperature,and the prepared films are annealed over the temperature range of 200 °C to 400 °C.Crystallinity and electrical properties of the films can be tuned correspondingly.The power factors of Bi2Te3 films of 0.85 μW/K2 cm to 11.43 μW/K2 cm were achieved after annealing.The infrared reflectance measurements from 2.5 μm to 5.0 μm demonstrate that there is also a slight red-shift of the plasma oscillation frequency in the Bi2Te3 films.By means of plasmonic calculations,we attribute the red-shift of absorption peaks to the reduction of carrier concentration and the change of effective mass of Bi2Te3 films with the increased annealing temperature.展开更多
We present a comprehensive investigation on CrAlGe and realize that it is an itinerant ferromagnet with strong tunability of the Curie temperature T_(C)and the spontaneous momentμ_(0)depending on annealing heat treat...We present a comprehensive investigation on CrAlGe and realize that it is an itinerant ferromagnet with strong tunability of the Curie temperature T_(C)and the spontaneous momentμ_(0)depending on annealing heat treatment.While the value of T_(C) was previously reported to be 80 K withμ_(0)≈0.41μB,in this work the two quantities attain values as high as 170 K and 0.66μ_(B),respectively.Heat treatment does not cause changes of the lattice parameters and symmetry,but results in a slight narrowing of the Bragg peaks.The strong tunability of the itinerant ferromagnetism indicates significantly tunable hybridization between the Cr 3d electrons and the conduction bands,in agreement with the dominant Cr–Al/Ge bonds of this compound.Further tuning along the same line towards even stronger or weaker itinerant ferromagnetism promises an interesting follow-up to clarify the localized-itinerant duality of the 3d electrons in this compound.展开更多
The effects of isothermal heat treatment on the semi-solid microstructure evolution of VW63Z(Mg-6Gd-3Y-0.4Zr,wt.%)alloy are studied.It shows that the microstructure of VW63Z alloy could transform from equiaxed crystal...The effects of isothermal heat treatment on the semi-solid microstructure evolution of VW63Z(Mg-6Gd-3Y-0.4Zr,wt.%)alloy are studied.It shows that the microstructure of VW63Z alloy could transform from equiaxed crystal to semi-solid spherical crystal after isothermal heat treatment above 620℃.With the heating temperature elevating from 620℃ to 635℃ and the holding time prolonging from 10 min to 35 min,the liquid fraction increases gradually.The semi-solid microstructure evolution of VW63Z alloy can be divided into three stages,i.e.,particle coarsening and spheroidization;particle necking,coalescence,and Ostwald ripening;and dynamic equilibrium.The semi-solid process window of VW63Z alloy ranges from 620℃ to 635℃,where the best process parameters are holding at 635℃ for 20 min-30 min.The solid fraction,the average particle size,and the shape factor are 41.1%-53.8%,81.5μm-83.2μm,and 0.70-0.75,respectively.The maximum relative deviations of the solid fraction,the particle size,and the shape factor at different heights of the same billet are 44.6%,17.4%,and 16.6%,respectively,which means that it should pay attention to the uniformity of edge and core of VW63Z alloy during isothermal heat treatment.The driving force of microstructure is supposed to be the reduction of solid-liquid interface free energy.展开更多
A pseudoplastic metal nanoparticle fluid （PMNF） is used in nanoimprint to fabricate semiconductors and func- tional devices. The evaporation of the solvent and the sintering of the Au PMNF are investigated. The key ...A pseudoplastic metal nanoparticle fluid （PMNF） is used in nanoimprint to fabricate semiconductors and func- tional devices. The evaporation of the solvent and the sintering of the Au PMNF are investigated. The key parameters, which influence the morphology of patterning, such as the radius of metal particles, the concentra- tion of metal particles, the Hamaker constant of the solvent, viscosity of the fluids and the evaporation velocity, are analyzed. Based on a two-sphere sintering model, the equations are derived, which represent the relationships between the relative shrinkage and radius of the metal particles, sintering temperature and time. The optimal parameters for the heat treatment are provided in nanoimprint.展开更多
High strength aluminium alloy AA7075(Al-Zn-Mg-Cu) is a precipitate hardenable alloy widely used in the aerospace,defense,marine and automobile industries.Use of the heat treatable aluminium alloys in all these sectors...High strength aluminium alloy AA7075(Al-Zn-Mg-Cu) is a precipitate hardenable alloy widely used in the aerospace,defense,marine and automobile industries.Use of the heat treatable aluminium alloys in all these sectors is ever-increasing owing to their excellent strength-toweight ratio and reasonably good corrosion resistance.The shortage in corrosion resistance,however,usually poses negative concern about their reliability and lifetime when they service in the variable marine environments.These alloys also exhibit low weldability due to poor solidification microstructure,porosity in fusion zone and lose their mechanical properties when they are welded by fusion welding techniques.Friction stir welding(FSW) is a reliable technique to retain the properties of the alloy as the joining takes place in the solid state.The welds are susceptible to corrosion due to the microstructural changes in the weld nugget during FSW.In this work,the effect of post weld treatments,viz.,peak aging(T6) and retrogression & reaging(RRA),on the microstructure,mechanical properties and pitting corrosion has been studied.Friction stir welding of 8 mm-thick AA7075 alloy was carried out.The microstructural changes of base metal and nugget zone of friction stir welds were studied using optical microscopy,scanning electron microscopy and transmission electron microscopy.Tensile and hardness test of base metal and welds has been carried out.Pitting corrosion resistance was determined through dynamic polarization test.It was observed that the hardness and strength of weld were observed to be comparatively high in peak aged(T6) condition but the welds showed poor corrosion resistance.The resistance to pitting corrosion was improved and the mechanical properties were maintained by RRA treatment.The resistance to pitting corrosion was improved in RRA condition with the minimum loss of weld strength.展开更多
This paper reports the effects of post weld heat treatments, namely artificial ageing and solution treatment followed by artificial ageing, on microstructure and mechanical properties of 12 mm thick friction stir weld...This paper reports the effects of post weld heat treatments, namely artificial ageing and solution treatment followed by artificial ageing, on microstructure and mechanical properties of 12 mm thick friction stir welded joints of precipitation hardenable high strength armour grade AA7075-T651 aluminium alloy. The tensile properties, such as yield strength, tensile strength, elongation and notch tensile strength, are evaluated and correlated with the microhardness and microstructural features. The scanning electron microscope is used to characterie the fracture surfaces. The solution treatment followed by ageing heat treatment cycle is found to be marginally beneficial in improving the tensile properties of friction stir welds of AA7075-T651 aluminium alloy.展开更多
Friction stir welding(FSW) of high strength aluminum alloys has been emerged as an alternative joining technique to avoid the problems during fusion welding.In recent times FSW is being used for armor grade AA7075 alu...Friction stir welding(FSW) of high strength aluminum alloys has been emerged as an alternative joining technique to avoid the problems during fusion welding.In recent times FSW is being used for armor grade AA7075 aluminum alloy in defense,aerospace and marine applications where it has to serve in non uniform loading and corrosive environments.Even though friction stir welds of AA7075 alloy possess better mechanical properties but suffer from poor corrosion resistance.The present work involves use of retrogression and reaging(RRA) post weld heat treatment to improve the corrosion resistance of welded joints of aluminum alloys.An attempt also has been made to change the chemical composition of the weld nugget by adding B4C nano particles with the aid of the FSW on a specially prepared base metal plate in butt position.The effects of peak aged condition(T6),RRA and addition of B4C nano particles on microstructure,hardness and pitting corrosion of nugget zone of the friction stir welds of AA7075 alloy have been studied.Even though RRA improved the pitting corrosion resistance,its hardness was slightly lost.Significant improvement in pitting corrosion resistance was achieved with addition of boron carbide powder and post weld heat treatment of RRA.展开更多
In this study,a mathematical model was developed to optimize the heat treatment process for maximum tensile strength and ductility of aluminum(8011) silicon carbide particulate composites.The process parameters are so...In this study,a mathematical model was developed to optimize the heat treatment process for maximum tensile strength and ductility of aluminum(8011) silicon carbide particulate composites.The process parameters are solutionizing time,aging temperature,and aging time.The experiments were performed on an universal testing machine according to centre rotatable design matrix.A mathematical model was developed with the main and interactive effects of the parameters considered.The analysis of variance technique was used to check the adequacy of the developed model.The optimum parameters were obtained for maximum tensile strength.Fractographic examination shows the cracks and dimples on the fractured surfaces of heat-treated specimen.展开更多
In this paper, the heat tratment of wood samples of 8 tree species with different colour were made at different temperature and time. Using SC-1 Model colorimeter, the colorimetric parameter was measured at quantitati...In this paper, the heat tratment of wood samples of 8 tree species with different colour were made at different temperature and time. Using SC-1 Model colorimeter, the colorimetric parameter was measured at quantitative measuring for treatment fore-and-after wood sampIes color. The effect of heat treatment conditions on wood color was analyzed. The results indicated: the temperature and time of heat treatment affected on big extent for wood samples color, in which the heat temperature was more evident than others. The luminance index of wood color parameter was more sensitive to treatment condition, which it reduced with temperature and time increasing, this kind of variation tendency was the same as all wood samples, but the variations extent was more different among the different wood species. After heat treatment the wood color hue and saturation variation direction were different for different wood species.This phenomenon had the relation to the migration and volatilization of color extract in heating process, or the rapid oxidation of lignin and some chemical element in high temperature.展开更多
The typical magnetic domains of Sm（CObalFe0.25Cuo.07Zr0.02）7.4 magnets quenched through various heattreatment steps have been revealed by using magnetic force microscopy （MFM）. For the specimens in which the nomin...The typical magnetic domains of Sm（CObalFe0.25Cuo.07Zr0.02）7.4 magnets quenched through various heattreatment steps have been revealed by using magnetic force microscopy （MFM）. For the specimens in which the nominal c-axis is perpendicular to the imaging plane, the domain configurations change from plate-like for the as-sintered magnet to corrugation and spike-like for the homogenized one, and then to a coarse and finally to a finer domain structure when isothermally aged at 830℃ and then annealed at 400℃. However, only plate-like domains can be detected on the surfaces with the nominal c-axis parallel to the imaging plane. The finer domain （so-called interaction domain） is a characteristic magnetic domain pattern of the SmCo 2：IT-type magnets with high coercivities. Domain walls in a zigzag shape are revealed by means of MFM in final bulk SraCo 2：17-type sintered magnets.展开更多
The phase evolution of Bi-2223 precursor powder prepared by spray pyrolysis method is studied with different heat treatment parameters. The results show that the reaction temperature and phase composition of precursor...The phase evolution of Bi-2223 precursor powder prepared by spray pyrolysis method is studied with different heat treatment parameters. The results show that the reaction temperature and phase composition of precursor powder depend on heat treatment atmosphere. Phase assemblage of(Bi,Pb)-2212, AEC, CuO, and small Bi-2201 can be obtained by heat-treated in N2-0.1%O_2 atmosphere. For precursor powder, there is sufficient reaction process at 770℃, and the dimension of Bi-2212 phase increases rapidly with the increase of heat treatment temperature and time. The dimension of AEC phase also increases by extending heat treatment time. As a balance among phase assemblage, dimension of particle and adequate reaction, a reasonable precursor powder can be obtained by heat-treated at 770℃ for 12 h–16 h in N2-0.1%O_2 atmosphere. Critical current of 37-filament Bi-2223 tape is about 120 A, which confirms that these heat treatment parameters are reasonable.展开更多
基金the financial support by the National Natural Science Foundation of China(No.12272094,51805087 and 51705080)the Natural Science Foundation of Fujian Province of China(No.2022J01541)。
文摘The purpose of this paper is to examine the effect of processing parameters and subsequent heat treatments on the microstructures and bonding strengths of Ti-6Al-4V/AA1050 laminations formed via a non-equal channel lateral co-extrusion process.The microstructural evolution and growth mechanism in the diffusion layer were discussed further to optimize the bonding quality by appropriately adjusting process parameters.Scanning electron microscopes(SEM),energy dispersive spectrometer(EDS),and X-ray diffraction(XRD)were used to characterize interfacial diffusion layers.The shear test was used to determine the mechanical properties of the interfacial diffusion layer.The experimental results indicate that it is possible to co-extrusion Ti-6Al-4V/AA1050 compound profiles using non-equal channel lateral co-extrusion.Different heat treatment processes affect the thickness of the diffusion layer.When the temperature and time of heat treatment increase,the thickness of the reaction layers increases dramatically.Additionally,the shear strength of the Ti-6Al-4V/AA1050 composite interface is proportional to the diffusion layer thickness.It is observed that a medium interface thickness results in superior mechanical performance when compared to neither a greater nor a lesser interface thickness.Microstructural characterization of all heat treatments reveals that the only intermetallic compound observed in the diffusion layers is TiAl_(3).Due to the inter-diffusion of Ti and Al atoms,the TiAl_(3) layer grows primarily at AA1050/TiAl_(3) interfaces.
文摘The phase transformation activation energy of the Cu61.13Zn33.94A14.93 alloys, which were treated at 4 GPa and 700 ℃ for 15 minutes, was calculated by means of differential scanning calorimetry curves obtained at various heating and cooling rates. Then, the effects of high-pressure heat treatments on the solid-state phase transformation and the microstructures of Cu61.13Zn33.94A14.93 alloys were investigated. The results show that high-pressure heat treatments can refine the grains and can change the preferred orientation from （111） to （200） of α phase. Compared with the as-cast alloy, the sample with high-pressure heat treatment has finer grains, lower β＇→β and/β→β＇ transformation temperature and activation energy. Furthermore, we found that high cooling rate favours the formation of fine needle-like α phase in the range of 5-20℃/min.
基金Financial supports from the National Natural Science Foundation of China (21503120, 21403126)Hubei Provincial Natural Science Foundation of China (2018CFB659)Innovation Foundation from China Three Gorges University (2019SSPY150)
文摘Pd-based nanocatalyst is a potential oxygen reduction oxidation(ORR)catalyst because of its high activity in alkaline medium and low cost.In this work,bimetallic Pd Au nanocatalysts are prepared by one-pot hydrothermal method using triblock pluronic copolymers,poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)(PEO19-PPO69-PEO19)(P123)as reducer and stabilizer,and heat-treatment method is applied to regulate catalyst structure and improve catalyst activity.The results show that the heat treatment can agglomerate the catalyst to a certain extent,but effectively improve the crystallinity and alloying degree of the catalyst.The ORR performance of the Pd Au nanocatalysts obtained under different heat treatment conditions is systematically investigated.Compared with commercial Pd black and Pd Au catalyst before heat treatment,the ORR performance of Au Pd nanocatalyst obtained after heat treatment for one hour at 500℃ has been enhanced.The Pd Au nanocatalysts after heat treatment also display enhanced anti-methanol toxicity ability in acidic medium.
基金supported by the National Natural Science Foundation of China(No.20706039)the National Basic Research Program(973 Program) of China (No.2005CB221204)+1 种基金the Program for the Top Young Academic Leaders of Higher Learning Institutions of Shanxi of China in 2010the Young Scientific and the Technical Fund of Shanxi of China (No.2006021010)
文摘Cu-Zn-Al slurry catalysts were prepared using a complete liquid-phase preparation technology under different heat treatment atmospheres.The catalysts were characterized using X-ray diffraction,X-ray photoelectron spectroscope,and N2 adsorption-desorption.Their application in the single-step synthesis of dimethyl ether from syngas was also investigated.The results indicate that the type of heat treatment atmosphere has an influence on the Cu species and the Cu0/Cu＋ ratio on the catalyst surface.Moreover,the final Cu/Zn ratio on the catalyst surface is mainly dependent on the composition and reaction environment of the catalyst and less on the type of heat treatment atmosphere.The prepared catalysts can suppress sintering of active sites at high temperatures,and the type of heat treatment atmosphere mainly affects the capability of the catalyst for methanol synthesis.The catalysts perform best using N2 as the heat treatment atmosphere.
基金Project supported by the Science and Technology Foundation of Heilongjiang Province,China (Grant No. A200912)the Program of Excellence Team in the Harbin Institute of Technology,China
文摘We fabricated complex microfluidic devices in silica glass by water-assisted femtosecond laser ablation and sub- sequent heat treatment. The experimental results show that after heat treatment, the diameter of the microehannels is significantly reduced and the internal surface roughness is improved. The diameters of the fabricated microehannels can be modulated by changing the annealing temperature and the annealing time. During annealing, the temperature affects the diameter and shape of the protrusions in microfluidic devices very strongly, and these changes are mainly caused by uniform expansion and the action of surface tension.
基金financially supported by the Special Scientific Research Fund for Public Service Sectors of Forestry(Grant No.201504603)Science and Technology Projects of Fujian Province(2014NZ003)the National Natural Science Foundation of China(Grant Nos.31370560,31170520)
文摘Wood has no inherent natural resistance against agents of biodegradation. We evaluated the effects of metal bath heat treatment(MBHT) on decay resistance and dimensional stability of Chinese parasol(Firmiana simplex) and Chinese fir(Cunninghamia lanceolata) wood. A low melting point alloy was used as heating medium in the treatment of the wood samples at 150, 180, and 210 °C for2, 4, and 8 h. Heat-treated and control samples were exposed to brown rot fungus(Poria placenta) and white rot fungus(Coriolus versicolor) for decay resistance testing and anti-swelling efficiency(ASE). The improved decay resistance with increase temperatures with low mass losses of 7.3 and 7.3% for F. simplex, and 3.9 and 3.6% for C.lanceolata at 210 °C for 8 h against Coriolus versicolor and Poria placenta, respectively. ASE indicated that MBHT contributed to improved dimensional stability of both wood species after treatment. Scanning electron micrograph results indicate that metal bath-treated samples showed strong decay resistance. Therefore, our approach to thermally modify wood should be explored to overcome the energy utilization by using low melting point alloy for the heat treatment of wood.
基金financially supported by the Special Scientific Research Fund for Public Service Sectors of Forestry(Grant No.201504603)Science and Technology Projects of Fujian Province(2014NZ003)the National Natural Science Foundation of China(Grant Nos.31370560,31170520)
文摘Pinus massoniana L. was thermally treated with low melting point alloy as heating medium to investigate the strength properties changes. Contact angle, color and scanning electron microscopy were recorded to assess the effectiveness of the treatment. Samples were pre-treated in a micro-wave for 5 min followed by metal bath heat treatment at 150, 180, and 210 °C for 2, 4, and 8 h,respectively. Strength properties of metal bath treated wood were decreased with increase temperature and time.Density, modulus of rupture, impact bending, modulus of elasticity were reduced for all treatments. Maximum compressive strength slightly increased at 150 °C for 4 h followed by gradual reduction. The Janka hardness was reduced in the tangential and radial directions. Treatment of the wood at 210 °C for 8 h caused the wood to become brittle and rupture. The contact angle was considerably higher after thermal treatment. The color of the wood became darker with increasing temperature of thermal treatment. Micrographs of the heat-treated samples showed damage to the cell wall with increase in temperature. Metal bath heat treatment of wood was carried out successfully and some strength properties were reduced.
基金funded by the National Natural Science Foundation of China (Grant No.11972018)sponsored by the Defense Pre-Research Joint Foundation of Chinese Ordnance Industry (Grant No. 6141B012858)。
文摘In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40 Cr Mn Si B steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thickness and the number of the circumferential divisions. The results show that as the tempering temperature was increased from 350 to 600 ℃, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface.
基金the National Natural Science Foundation of China(31701546)the Fundamental Research Funds for the Central Universities of China(2019ZD40)+5 种基金the 111 Project(B17018)for financial supportPearl River Talent Recruitment Program of Guangdong Province(2017GC010229)the Pearl River Nova Program of Guangzhou(201906010079)the National Natural Science Foundation of China(32001691)the special fund for scientific innovation strategyconstruction of high-level academy of agriculture science(R2019YJYB1001)the Application-oriented Projects of Guangdong Province(2017B020232002)。
文摘Natural foods,such as whole pulses,are recommended in the dietary guidelines of the US and China.The plant cell wall structure in whole pulses has important implications for the nutritional functionalities of starch.In this study,garbanzo bean cells with varying degrees of cell wall integrity were subjected to dry heat treatment(DHT)and used to elucidate the food structure-starch digestion properties of pulse food.The morphological features suggested that all cell samples do not exhibit remarkable changes after being subjected to DHT.Molecular rearrangement and the crystallite disruption of starch granules entrapped in cells occurred during DHT as assessed by the crystal structure and thermal properties.DHT decreased the inhibitory effects of enzymes of both the soluble and insoluble components,but the digestion rate and extent of slightly and highly damaged cell samples did not exhibit significant differences compared with their native counterparts.We concluded that the starch digestion of pulse cotyledon cells is primarily determined by the intactness of the cellular structure.This study reveals the role of food structure on the ability to retain the desirable nutritional properties of starch after subjection to physical modification.
基金supported by the National Natural Science Foundation of China under Grant No.51025208Program for Changjiang Scholars and Innovative Research Team in University under Grant No.IRT1309
文摘In this work,Bi2Te3 films（250 nm） are fabricated on Si O2/Si substrates by radio frequency（RF） magnetron sputtering at room temperature,and the prepared films are annealed over the temperature range of 200 °C to 400 °C.Crystallinity and electrical properties of the films can be tuned correspondingly.The power factors of Bi2Te3 films of 0.85 μW/K2 cm to 11.43 μW/K2 cm were achieved after annealing.The infrared reflectance measurements from 2.5 μm to 5.0 μm demonstrate that there is also a slight red-shift of the plasma oscillation frequency in the Bi2Te3 films.By means of plasmonic calculations,we attribute the red-shift of absorption peaks to the reduction of carrier concentration and the change of effective mass of Bi2Te3 films with the increased annealing temperature.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52088101,11974389,and 12141002)the National Key Research and Development Program of China(Grant Nos.2021YFA0718702 and 2017YFA0303100)+1 种基金the Chinese Academy of Sciences through the Scientific Instrument Developing Project(Grant No.ZDKYYQ20210003)the Strategic Priority Research Program(Grant No.XDB33000000)。
文摘We present a comprehensive investigation on CrAlGe and realize that it is an itinerant ferromagnet with strong tunability of the Curie temperature T_(C)and the spontaneous momentμ_(0)depending on annealing heat treatment.While the value of T_(C) was previously reported to be 80 K withμ_(0)≈0.41μB,in this work the two quantities attain values as high as 170 K and 0.66μ_(B),respectively.Heat treatment does not cause changes of the lattice parameters and symmetry,but results in a slight narrowing of the Bragg peaks.The strong tunability of the itinerant ferromagnetism indicates significantly tunable hybridization between the Cr 3d electrons and the conduction bands,in agreement with the dominant Cr–Al/Ge bonds of this compound.Further tuning along the same line towards even stronger or weaker itinerant ferromagnetism promises an interesting follow-up to clarify the localized-itinerant duality of the 3d electrons in this compound.
文摘The effects of isothermal heat treatment on the semi-solid microstructure evolution of VW63Z(Mg-6Gd-3Y-0.4Zr,wt.%)alloy are studied.It shows that the microstructure of VW63Z alloy could transform from equiaxed crystal to semi-solid spherical crystal after isothermal heat treatment above 620℃.With the heating temperature elevating from 620℃ to 635℃ and the holding time prolonging from 10 min to 35 min,the liquid fraction increases gradually.The semi-solid microstructure evolution of VW63Z alloy can be divided into three stages,i.e.,particle coarsening and spheroidization;particle necking,coalescence,and Ostwald ripening;and dynamic equilibrium.The semi-solid process window of VW63Z alloy ranges from 620℃ to 635℃,where the best process parameters are holding at 635℃ for 20 min-30 min.The solid fraction,the average particle size,and the shape factor are 41.1%-53.8%,81.5μm-83.2μm,and 0.70-0.75,respectively.The maximum relative deviations of the solid fraction,the particle size,and the shape factor at different heights of the same billet are 44.6%,17.4%,and 16.6%,respectively,which means that it should pay attention to the uniformity of edge and core of VW63Z alloy during isothermal heat treatment.The driving force of microstructure is supposed to be the reduction of solid-liquid interface free energy.
基金Supported by the National Natural Science Foundation of China under Grant Nos 51175479 and 51475436the Education Department of Henan Province under Grant Nos 13A460725 and 2013GGJS-001
文摘A pseudoplastic metal nanoparticle fluid （PMNF） is used in nanoimprint to fabricate semiconductors and func- tional devices. The evaporation of the solvent and the sintering of the Au PMNF are investigated. The key parameters, which influence the morphology of patterning, such as the radius of metal particles, the concentra- tion of metal particles, the Hamaker constant of the solvent, viscosity of the fluids and the evaporation velocity, are analyzed. Based on a two-sphere sintering model, the equations are derived, which represent the relationships between the relative shrinkage and radius of the metal particles, sintering temperature and time. The optimal parameters for the heat treatment are provided in nanoimprint.
文摘High strength aluminium alloy AA7075(Al-Zn-Mg-Cu) is a precipitate hardenable alloy widely used in the aerospace,defense,marine and automobile industries.Use of the heat treatable aluminium alloys in all these sectors is ever-increasing owing to their excellent strength-toweight ratio and reasonably good corrosion resistance.The shortage in corrosion resistance,however,usually poses negative concern about their reliability and lifetime when they service in the variable marine environments.These alloys also exhibit low weldability due to poor solidification microstructure,porosity in fusion zone and lose their mechanical properties when they are welded by fusion welding techniques.Friction stir welding(FSW) is a reliable technique to retain the properties of the alloy as the joining takes place in the solid state.The welds are susceptible to corrosion due to the microstructural changes in the weld nugget during FSW.In this work,the effect of post weld treatments,viz.,peak aging(T6) and retrogression & reaging(RRA),on the microstructure,mechanical properties and pitting corrosion has been studied.Friction stir welding of 8 mm-thick AA7075 alloy was carried out.The microstructural changes of base metal and nugget zone of friction stir welds were studied using optical microscopy,scanning electron microscopy and transmission electron microscopy.Tensile and hardness test of base metal and welds has been carried out.Pitting corrosion resistance was determined through dynamic polarization test.It was observed that the hardness and strength of weld were observed to be comparatively high in peak aged(T6) condition but the welds showed poor corrosion resistance.The resistance to pitting corrosion was improved and the mechanical properties were maintained by RRA treatment.The resistance to pitting corrosion was improved in RRA condition with the minimum loss of weld strength.
文摘This paper reports the effects of post weld heat treatments, namely artificial ageing and solution treatment followed by artificial ageing, on microstructure and mechanical properties of 12 mm thick friction stir welded joints of precipitation hardenable high strength armour grade AA7075-T651 aluminium alloy. The tensile properties, such as yield strength, tensile strength, elongation and notch tensile strength, are evaluated and correlated with the microhardness and microstructural features. The scanning electron microscope is used to characterie the fracture surfaces. The solution treatment followed by ageing heat treatment cycle is found to be marginally beneficial in improving the tensile properties of friction stir welds of AA7075-T651 aluminium alloy.
文摘Friction stir welding(FSW) of high strength aluminum alloys has been emerged as an alternative joining technique to avoid the problems during fusion welding.In recent times FSW is being used for armor grade AA7075 aluminum alloy in defense,aerospace and marine applications where it has to serve in non uniform loading and corrosive environments.Even though friction stir welds of AA7075 alloy possess better mechanical properties but suffer from poor corrosion resistance.The present work involves use of retrogression and reaging(RRA) post weld heat treatment to improve the corrosion resistance of welded joints of aluminum alloys.An attempt also has been made to change the chemical composition of the weld nugget by adding B4C nano particles with the aid of the FSW on a specially prepared base metal plate in butt position.The effects of peak aged condition(T6),RRA and addition of B4C nano particles on microstructure,hardness and pitting corrosion of nugget zone of the friction stir welds of AA7075 alloy have been studied.Even though RRA improved the pitting corrosion resistance,its hardness was slightly lost.Significant improvement in pitting corrosion resistance was achieved with addition of boron carbide powder and post weld heat treatment of RRA.
文摘In this study,a mathematical model was developed to optimize the heat treatment process for maximum tensile strength and ductility of aluminum(8011) silicon carbide particulate composites.The process parameters are solutionizing time,aging temperature,and aging time.The experiments were performed on an universal testing machine according to centre rotatable design matrix.A mathematical model was developed with the main and interactive effects of the parameters considered.The analysis of variance technique was used to check the adequacy of the developed model.The optimum parameters were obtained for maximum tensile strength.Fractographic examination shows the cracks and dimples on the fractured surfaces of heat-treated specimen.
文摘In this paper, the heat tratment of wood samples of 8 tree species with different colour were made at different temperature and time. Using SC-1 Model colorimeter, the colorimetric parameter was measured at quantitative measuring for treatment fore-and-after wood sampIes color. The effect of heat treatment conditions on wood color was analyzed. The results indicated: the temperature and time of heat treatment affected on big extent for wood samples color, in which the heat temperature was more evident than others. The luminance index of wood color parameter was more sensitive to treatment condition, which it reduced with temperature and time increasing, this kind of variation tendency was the same as all wood samples, but the variations extent was more different among the different wood species. After heat treatment the wood color hue and saturation variation direction were different for different wood species.This phenomenon had the relation to the migration and volatilization of color extract in heating process, or the rapid oxidation of lignin and some chemical element in high temperature.
基金Project supported by the Beijing Municipal Science and Technology Committee Key Project, China (Grant No D0406002000091)the National Natural Science Foundation of China (Grant No 10374110)
文摘The typical magnetic domains of Sm（CObalFe0.25Cuo.07Zr0.02）7.4 magnets quenched through various heattreatment steps have been revealed by using magnetic force microscopy （MFM）. For the specimens in which the nominal c-axis is perpendicular to the imaging plane, the domain configurations change from plate-like for the as-sintered magnet to corrugation and spike-like for the homogenized one, and then to a coarse and finally to a finer domain structure when isothermally aged at 830℃ and then annealed at 400℃. However, only plate-like domains can be detected on the surfaces with the nominal c-axis parallel to the imaging plane. The finer domain （so-called interaction domain） is a characteristic magnetic domain pattern of the SmCo 2：IT-type magnets with high coercivities. Domain walls in a zigzag shape are revealed by means of MFM in final bulk SraCo 2：17-type sintered magnets.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB0902303)the Key Research and Development Program of Shaanxi Province,China(Grant No.2018GY-121N)the National Key Project of Magneto Constrained Fusion Energy Development Program,China(Grant No.2015GB115001)
文摘The phase evolution of Bi-2223 precursor powder prepared by spray pyrolysis method is studied with different heat treatment parameters. The results show that the reaction temperature and phase composition of precursor powder depend on heat treatment atmosphere. Phase assemblage of(Bi,Pb)-2212, AEC, CuO, and small Bi-2201 can be obtained by heat-treated in N2-0.1%O_2 atmosphere. For precursor powder, there is sufficient reaction process at 770℃, and the dimension of Bi-2212 phase increases rapidly with the increase of heat treatment temperature and time. The dimension of AEC phase also increases by extending heat treatment time. As a balance among phase assemblage, dimension of particle and adequate reaction, a reasonable precursor powder can be obtained by heat-treated at 770℃ for 12 h–16 h in N2-0.1%O_2 atmosphere. Critical current of 37-filament Bi-2223 tape is about 120 A, which confirms that these heat treatment parameters are reasonable.
