A Cu-10wt%Fe composite was prepared through hot-pressed sintering,and the material was subsequently solution treated.The hot-pressed sintered and solution treated materials were rolled and aged.The precipitation behav...A Cu-10wt%Fe composite was prepared through hot-pressed sintering,and the material was subsequently solution treated.The hot-pressed sintered and solution treated materials were rolled and aged.The precipitation behavior and performance changes were systematically studied by using scanning electron microscopy and transmission electron microscopy.In contrast to the hot-pressed sintered specimen,the solution treatment significantly affects the thermal stability and properties of the Cu-10wt%Fe composite.The Cu-10wt%Fe composite was prepared after solid solution,cold rolling and aging at 773 K for 1 h,and it obtained excellent tensile strength of 494 MPa,uniform elongation of 16.3%,electrical conductivity of 51.1%IACS and softening temperature of 838 K.Mechanisms for the distinct difference in thermal stability and properties between hot-pressed sintered and solution treated specimens were analyzed.These findings provide a theoretical basis for designing high-performance Cu-based in-situ composites by post treatment.展开更多
Arsenic materials have attracted great attention due to their unique properties.However,research concerning iron-arsenic(Fe-As) alloys is very scarce due to the volatility of As at low temperature and the high melting...Arsenic materials have attracted great attention due to their unique properties.However,research concerning iron-arsenic(Fe-As) alloys is very scarce due to the volatility of As at low temperature and the high melting point of Fe.Herein,a new Fe-As alloy was obtained by mechanical alloying(MA) followed by vacuum hot-pressed sintering(VHPS).Moreover,a systematic study was carried out on the microstructural evolution,phase composition,leaching toxicity of As,and physical and mechanical properties of Fe-As alloys with varying weight fractions of As(20%,25%,30%,35%,45%,55%,65%,and 75%).The results showed that pre-alloyed metallic powders(PAMPs) have a fine grain size and specific supersaturated solid solution after MA,which could effectively improve the mechanical properties of Fe-As alloys by VHPS.A high density(> 7.350 g·cm^(-3)),low toxicity,and excellent mechanical properties could be obtained for FeAs alloys sintered via VHPS by adding an appropriate amount of As,which is more valuable than commercial Fe-As products.The Fe-25% As alloy with low toxicity and a relatively high density(7.635 g·cm^(-3)) provides an ultra-high compressive strength(1989.19 MPa),while the Fe-65% As alloy owns the maximum Vickers hardness(HVo.5 899.41).After leaching by the toxicity characteristic leaching procedure(TCLP),these alloys could still maintain good mechanical performance,and the strengthening mechanisms of Fe-As alloys before and after leaching were clarified.Changes in the grain size,micro structure,and phase distribution induced significant differences in the compressive strength and hardness.展开更多
Alumina-(0 similar to 20 vol. pct) iron composites were fabricated by hot-pressing of well-mixed-alumina and iron powders at 1400 degreesC and 30 MPa for 30 min. Hot-pressed bodies with nearly theoretical density were...Alumina-(0 similar to 20 vol. pct) iron composites were fabricated by hot-pressing of well-mixed-alumina and iron powders at 1400 degreesC and 30 MPa for 30 min. Hot-pressed bodies with nearly theoretical density were obtained for addition up to 10 vol. pct Fe, but relative density decreased gradually with further increase in Fe addition. The materials exhibit a homogeneous dispersion of Fe. Fracture strength of the composites exhibits a maximum value of 604 MPa at 15 vol. pct Fe, which is 1.5 times that of alumina alone. Fracture toughness increases with the increase in Fe content, reaching 7.5 MPa.m(1/2) at 20 vol. pct Fe. The theoretical values of fracture toughness was calculated and compared with the experimental one. Toughening mechanisms of the composites are also discussed.展开更多
The three-layered(W-60 vol%Cu/W-40 vol%Cu/W-20 vol%Cu)W/Cu functionally graded material(FGM)containing a Cu network structure was fabricated at different temperatures by hot-pressed sintering produced from copper-coat...The three-layered(W-60 vol%Cu/W-40 vol%Cu/W-20 vol%Cu)W/Cu functionally graded material(FGM)containing a Cu network structure was fabricated at different temperatures by hot-pressed sintering produced from copper-coated tungsten powders.The effects of various sintering temperatures on relative density,microstructure,thermal conductivity,hardness and flexural strength were investigated.Scanning electron microscopy(SEM)and X-ray diffraction(XRD)analysis show that a Cu network extends throughout the W/Cu FGM specimens sintered at 1065℃and the graded structure can be retained perfectly,and W particles are distributed homogeneously.The low-temperature sintering densification of W/Cu FGM arises because the sintering mode of the copper-coated tungsten particles includes just sintering Cu to Cu,rather than Cu to W,Cu to Cu and W to W,as required for conventional powder particles.The relative density of W/Cu FGM sintered at 1065℃for 3 h under a load of25 MPa is 96.1%.The thermal conductivity is up to204 W·m^-1·K^-1 at normal temperature and 150 W·m^-1·K^-1at 800℃.And the Vickers hardness varies with the gradient of different layers from 3.34 to 4.05 GPa.展开更多
12 vol%WCp/2024Al composite was fabricated from mixed powders by hot-pressing at various tempera-tures. Investigation of the interfacial reaction between the WC phase and the Al alloy matrix was performed by X-ray dif...12 vol%WCp/2024Al composite was fabricated from mixed powders by hot-pressing at various tempera-tures. Investigation of the interfacial reaction between the WC phase and the Al alloy matrix was performed by X-ray diffraction （XRD）, transmission electron microscope （TEM） and energy dispersive spectroscopy （EDS）. A multiple layer interface structure, which is composed of Al/ WAl12/AlnC3/WC, is found to form by the interfacial reaction during hot-pressing. Further study shows that the AlaC3 layer forms along with a given crystal orientation of WC phase and might retard the interfacial reaction process.展开更多
Synthesis and ion transport properties of hot-pressed solid polymer electrolytes （SPEs）, （l-x） PEO： x KI, where x is the content of KI in wt%, are reported. A hot-press technique has been used for the formation o...Synthesis and ion transport properties of hot-pressed solid polymer electrolytes （SPEs）, （l-x） PEO： x KI, where x is the content of KI in wt%, are reported. A hot-press technique has been used for the formation of the polymeric membranes in place of the usual solution cast method. The composition （80 PEO：20 KI） was identified as the highest conducting polymer electrolyte on the basis of compositional dependent conductivity studies of PEO：KI films. A conductivity enhancement of more than two orders of magnitude from that of the pure PEO was achieved. Materials characterization and ion transport mechanism were explained by using various experimental techniques.展开更多
Densification, phase transformation and fracture toughness were studied in hot-pressed Si_3N_4 seeded by in-houseproduced large, elongated β-Si_3N_4 seeds. A mixture of Y_2O_3-Al_2O_3 was used as the sintering aid. C...Densification, phase transformation and fracture toughness were studied in hot-pressed Si_3N_4 seeded by in-houseproduced large, elongated β-Si_3N_4 seeds. A mixture of Y_2O_3-Al_2O_3 was used as the sintering aid. Concentration ofseeds were varied from 0 to 6 wt pct and the sintering time at 1700℃ was varied from 1 to 4 h. Maximum fracturetoughness of 9.0 MPam^(1/2) was measured in samples containing 5 wt pct seeds, hot pressed at 1700℃ for 4 h.展开更多
Ⅰ. INTRODUCTIONSilicon nitride （Si<sub>3</sub>N<sub>4</sub>）ceramics is among the most hopeful structural materials with excellent mechanical and thermal properties. However, it is a brittle...Ⅰ. INTRODUCTIONSilicon nitride （Si<sub>3</sub>N<sub>4</sub>）ceramics is among the most hopeful structural materials with excellent mechanical and thermal properties. However, it is a brittle material. Fiber-reinforcement has been proved to be an effective approach to improving the展开更多
SnSe-based thermoelectric materials are being explored since they have potential high thermoelectric figure of merit.We synthesized polycrystalline Al_(x)Sn_(1-x)Se(x=0.01,0.02,0.03 and 0.04)by hot-pressing method,and...SnSe-based thermoelectric materials are being explored since they have potential high thermoelectric figure of merit.We synthesized polycrystalline Al_(x)Sn_(1-x)Se(x=0.01,0.02,0.03 and 0.04)by hot-pressing method,and combined theoretical estimation with experimental measurement to investigate the in-fluence of Al doping on thermoelectric properties of SnSe.It was found that dopant Al can effectively adjust the band structure of SnSe by introducing intermediate band.Al doping with low content(x=0.01 and 0.02)can introduce a single intermediate band close to the valence band maximum or conduction band minimum,achieving band engineering optimization.In high temperature region(498 K<T<823 K),the electronic transport properties significantly enhance with thermal excitation.The lattice thermal conductivity reduces with the Al atomic point defect scattering,leading to a low thermal conductivity of 0.47 W m^(-1) K^(-1) in Al_(0.04)Sn_(0.96)Se at 823 K.As a result,a high ZT of 0.84 at 823 K is obtained from the Al_(0.04)Sn_(0.96) Se perpendicular to the pressing direction,which is 58.5%larger than that of SnSe.In addition,dopant Al can adjust the anisotropy of polycrystalline SnSe.The anisotropy of electronic properties are enhanced with low doping level(x=0.01,0.02)and suppressed with high doping level(x=0.03,0.04).展开更多
The Nd-Fe-B magnets are pre-sintered and then processed with hot-pressing,and the resulting magnets are called the hot-pressed pretreated(HPP)magnets.The coercivity of the HPP magnets increases as the annealed tempera...The Nd-Fe-B magnets are pre-sintered and then processed with hot-pressing,and the resulting magnets are called the hot-pressed pretreated(HPP)magnets.The coercivity of the HPP magnets increases as the annealed temperature increases.When the annealing temperature is 900℃,the coercivity of the magnet is only 17.6 kOe(1 Oe=79.5775 A·m^-1),but when the annealing temperature rises up to 1060℃,the coercivity of the magnet reaches 23.53 kOe,which is remarkably increased by 33.7%.The microstructure analysis indicates that the grain surface of the HPP magnet becomes smoother as the annealed temperature increases.The microstructure factorαis changed according to the intrinsic coercivity model formula.Theαof the magnet at 900℃is only 0.578,but it is 0.825 at 1060℃.Microstructural optimization is due mainly to the increase of coercivity of the HPP magnet.展开更多
A new NiCu alloy was developed and utilized as binder phase for WC composites.The composites with spherical cast WC particle contents of 55-65 wt.%were prepared by rapid hot-pressing technique.The microstructures were...A new NiCu alloy was developed and utilized as binder phase for WC composites.The composites with spherical cast WC particle contents of 55-65 wt.%were prepared by rapid hot-pressing technique.The microstructures were characterized by scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDS),and transmission electron microscopy(TEM).The results reveal that the cast WC particles are uniformly dispersed within the NiCu matrix.The interface between WC and NiCu alloy is clear with no additional phase observed.Mechanical properties testing indicates that the hardness of the composite shows minimal variation as the cast WC particle content increases.Both the transverse rupture strength(TRS)and fracture toughness show a comparable decline,while the impact toughness first increases and then decreases.The NiCu alloy matrix plays a critical role in enhancing the fracture toughness of the composite.However,at high strain rates,the impact toughness deteriorates due to strain rate hardening of the NiCu matrix and a reduced density resulting from the higher WC content.展开更多
HyperCoal was prepared from low-rank coal via high-temperature solvent extraction with N-methylpyrrolidone as an extraction solvent and a liquid-to-solid ratio of 50 mL/g in a high-temperature and high-pressure reacto...HyperCoal was prepared from low-rank coal via high-temperature solvent extraction with N-methylpyrrolidone as an extraction solvent and a liquid-to-solid ratio of 50 mL/g in a high-temperature and high-pressure reactor. When HyperCoal was used as a binder and pulverized coal was used as the raw material, the compressive strength of the hot-pressed briquettes(each with a diameter of 20 mm and mass of 5 g) under different conditions was studied using a hot-pressing mold and a high-temperature furnace. The compressive strength of the hot-pressed briquettes was substantially improved and reached 436 N when the holding time period was 15 min, the hot-pressing temperature was 673 K, and the HyperCoal content, was 15 wt%. Changes in the carbonaceous structure, as reflected by the intensity ratio between the Raman G-and D-bands(IG/ID), strongly affected the compressive strength of hot-pressed briquettes prepared at different hot-pressing temperatures. Compared with cold-pressed briquettes, hot-pressed briquettes have many advantages, including high compressive strength, low ash content, high moisture resistance, and good thermal stability; thus, we expect that hot-pressed briquettes will have broad application prospects.展开更多
B4Cp/6061Al composites have become important structural and functional materials and can be fabricated by powder metallurgy and subsequent hot rolling. In this work, the effects of the hot-pressing temperature on micr...B4Cp/6061Al composites have become important structural and functional materials and can be fabricated by powder metallurgy and subsequent hot rolling. In this work, the effects of the hot-pressing temperature on microstructures and mechanical behaviors of the B4Cp/6061Al composites were investigated. The results showed that compared with the T4 heat treated B4Cp/6061Al composite hot pressed at 560℃, the yield strength and failure strain of the composites hot pressed at 580℃ were increased to 235 MPa and 18.4%, respectively. This was associated with the interface bonding strength between the B4C particles and the matrix. However, the reaction products, identified to be MgAl2O4 phases, were detected in the composites hot pressed at 600℃. The formation of the MgAl2O4 phases resulted in the Mg depletion, thus reducing the yield strength to 203.5 MPa after the T4 heat treatment due to the effect of the solid solution strengthening being weakened. In addition, the variation of hardness and electrical conductivity was mainly related to the Mg content in the matrix. Based on the as-rolled microstructures observed by SEM, SR-μCT and fracture surfaces, the deformation schematic diagram was depicted to reflect the tensile deformation process of the composites.展开更多
Piezoelectric poly(vinylidene fluoride)(PVDF)has received considerable attention due to its ability of interconverting mechanical into electric energies and potential applications in wearable electronics.To achieve pi...Piezoelectric poly(vinylidene fluoride)(PVDF)has received considerable attention due to its ability of interconverting mechanical into electric energies and potential applications in wearable electronics.To achieve piezoelectricity,it is important to simultaneously control the formation of polar phases,crystallinity,and dipole alignments in PVDF-based films.Here we demonstrate that piezoelectricity can be obtained by directly hot-pressing PVDF films sandwiched between chitosan or cellulose films.The electrostatic interactions between PVDF and chitosan or cellulose enabled an exceptional high content of polar phases(β-andγ-phases)up to 90%and a measured piezoelectric charge coefficient d_(33)of up to-30 pC/N.This study provides a simple and low-cost approach for obtaining piezoelectric PVDF films used for sensors,actuators,and energy harvesters.展开更多
Safety issues induced by infinite anode volume change and uncontrolled lithium(Li)dendrite growth have become the biggest obstacle to the practical application of Li metal batteries.In addition,the tra-ditional rollin...Safety issues induced by infinite anode volume change and uncontrolled lithium(Li)dendrite growth have become the biggest obstacle to the practical application of Li metal batteries.In addition,the tra-ditional rolling method makes it difficult to manufacture thin Li foil with high mechanical strength and low Li content.Herein,a three-dimensional(3D)lithophilic carbon paper/copper(Cu)current collector hybrid anode with ultra-low Li metal content is prepared by a hot-pressing method.The highly re-versible and stable lithiophilic layer LiC_(x) formed in situ by heating/pressing treatment provides abun-dant nucleation sites and reduces the Li nucleation overpotential,thereby effectively suppressing Li den-drite growth.Moreover,the volume change and pulverization problems of Li metal anode during depo-sition/stripping also can be accommodated by the 3D skeleton.The optimization effect has been directly confirmed by in-situ optical and ex-situ scanning electron microscope observation.Therefore,highly sta-ble performance(158.4 mA h g^(-1) at 2 C after 200 cycles with a capacity retention of 95.24%)in Li@LCP-Cu||NCM811 coin cell can be achieved.Furthermore,the solid-state battery assembled with the hybrid anode,poly(vinylidene fluoride)(PVDF)-based polymer electrolyte and polyethylene oxide(PEO)interface functional layer also exhibits the best electrochemical and safety performance,which also proves that the Li@LCP-Cu anode has great potential for application in solid-state batteries.展开更多
FeAl intermetallic compound with different contents of rare earth oxide La2O3 addition was prepared by hot pressing the mechanically alloyed powders.Effect of La2O3 on microstructure and high-temperature wear property...FeAl intermetallic compound with different contents of rare earth oxide La2O3 addition was prepared by hot pressing the mechanically alloyed powders.Effect of La2O3 on microstructure and high-temperature wear property of the sintered FeAl samples was investigated in this paper.The results showed that 1 wt.% La2O3 addition could refine the microstructure and increase the density of the FeAl intermetallic compound,and correspondingly improved the high-temperature wear resistance.SEM and EDS analyses of the wo...展开更多
A hot-press tackified preform was used to improve the uniformity of the laminates thickness and the mechanical properties of the obtained laminates were studied using vacuum assisted resin transfer molding（VARTM）. T...A hot-press tackified preform was used to improve the uniformity of the laminates thickness and the mechanical properties of the obtained laminates were studied using vacuum assisted resin transfer molding（VARTM）. Two modified preforms were prepared under 0.1 and 0.6 MPa in an autoclave and then were used to fabricate the laminates via VARTM. Permeability and thickness distribution of the laminates were obtained by using a special device. Moreover, the tensile and compressive strengths of the obtained laminates were studied and compared with the unmodified ones. Results show that the tackified laminates present a maximum and minimum thickness under 0.1 and 0.6 MPa, respectively. The thicknesses and in-plane permeability of the tackified laminates, with better thickness uniformity, are significantly decreased compared with that of the unmodified cases, while the tensile and compressive strengths of the tackified laminates are improved obviously. Results show that the mechanical property of the tackified laminates prepared by hotpressing at 0.1 MPa is better than that processed at 0.6 MPa.展开更多
A new pressing method was proposed for hot-pressing process. Experimental results indicated that the porosity in Al2O3/TiC/ Ni/Mo (hereafter called AI2O3/TiC composite) composite compacts decreases by 6% after adoptin...A new pressing method was proposed for hot-pressing process. Experimental results indicated that the porosity in Al2O3/TiC/ Ni/Mo (hereafter called AI2O3/TiC composite) composite compacts decreases by 6% after adopting this new technique, compared to traditional hot-pressing technique under the same sintering temperature. The flexural strength and Vicker hardness increase from 883 MPa to 980 MPa and from 16 GPa to 21.1 GPa, respectively. A theoretical model was given to analyze the densification mechanism of the composite in the process of repetitious-hot-pressing.展开更多
In this work, the tungsten particulate reinforced Al2O3 dispersion strengthened copper base composites were successfully fabricated by using a vacuum hot-press sintering method. With the test temperature varying from ...In this work, the tungsten particulate reinforced Al2O3 dispersion strengthened copper base composites were successfully fabricated by using a vacuum hot-press sintering method. With the test temperature varying from 650 to 950 ℃ and the strain rate varying from 0.01 to 5 s-1, the W(50)/Cu-Al2O3 composites were isothermally compressed on a Gleeble-1500D thermal simulator. The true stress-strain curves of the W(50)/Cu-Al2O3 under different test conditions were obtained. The dynamic recrystallization of the W(50)/Cu-Al2O3 composite occurs during the isothermal compression. The constitutive equations and the hot deformation activation energy of W(50)/Cu-Al2O3 composites were calculated on the basis of the above experimental results.展开更多
BN-MgA1ON composites were prepared by hot-pressing sintering under nitrogen atmosphere with BN-Mg- A1ON composite powders as raw material and Y2 O3 as sintering additive. Based on thermodynamic analysis, the oxi- dati...BN-MgA1ON composites were prepared by hot-pressing sintering under nitrogen atmosphere with BN-Mg- A1ON composite powders as raw material and Y2 O3 as sintering additive. Based on thermodynamic analysis, the oxi- dation resistance of BN-MgAION composites was investigated and the dynamics of oxidation process was also ana- lyzed. The oxidation process and the micro-morphology of the samples before and after oxidation were characterized by X-ray diffraction and scanning electron microscopy. The dynamics of oxidation resistance of the BN-MgA1ON composites was investigated via the analysis of the constant temperature oxidation mass gain curves. The results show that the main components of the material are MgA1ON, Sialon, BN and CaYAI3 07 at 1 650--1750 ＊C, and the content of CaYA1307 decreases as the sintering temperature increases. The BN-MgA1ON composites prepared at 1750 ℃ is uniform and compact with the balanced distributions of A1, Mg, O, and N. The oxidation process of BN- MgA1ON composites in air mainly consists of MgAION, Sialon and BN oxidation. The section after being oxidized at 1000--1300 ℃ involves three layers, namely, the outer layer, the middle layer and the inner layer. The oxidation process follows the parabola model. The apparent activation energy of the oxidation process is 2.13 × 10 5 J/mol and the frequency factor is 4.66 × 10 6.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant No.52101181).
文摘A Cu-10wt%Fe composite was prepared through hot-pressed sintering,and the material was subsequently solution treated.The hot-pressed sintered and solution treated materials were rolled and aged.The precipitation behavior and performance changes were systematically studied by using scanning electron microscopy and transmission electron microscopy.In contrast to the hot-pressed sintered specimen,the solution treatment significantly affects the thermal stability and properties of the Cu-10wt%Fe composite.The Cu-10wt%Fe composite was prepared after solid solution,cold rolling and aging at 773 K for 1 h,and it obtained excellent tensile strength of 494 MPa,uniform elongation of 16.3%,electrical conductivity of 51.1%IACS and softening temperature of 838 K.Mechanisms for the distinct difference in thermal stability and properties between hot-pressed sintered and solution treated specimens were analyzed.These findings provide a theoretical basis for designing high-performance Cu-based in-situ composites by post treatment.
基金financially supported by the National Natural Science Foundation of China (No.52104406)the Natural Science Foundation of Hunan Province (No.2022JJ20074)+1 种基金the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (No.52121004)the National Natural Science Foundation of China for Distinguished Young Scholars (No.51825403)。
文摘Arsenic materials have attracted great attention due to their unique properties.However,research concerning iron-arsenic(Fe-As) alloys is very scarce due to the volatility of As at low temperature and the high melting point of Fe.Herein,a new Fe-As alloy was obtained by mechanical alloying(MA) followed by vacuum hot-pressed sintering(VHPS).Moreover,a systematic study was carried out on the microstructural evolution,phase composition,leaching toxicity of As,and physical and mechanical properties of Fe-As alloys with varying weight fractions of As(20%,25%,30%,35%,45%,55%,65%,and 75%).The results showed that pre-alloyed metallic powders(PAMPs) have a fine grain size and specific supersaturated solid solution after MA,which could effectively improve the mechanical properties of Fe-As alloys by VHPS.A high density(> 7.350 g·cm^(-3)),low toxicity,and excellent mechanical properties could be obtained for FeAs alloys sintered via VHPS by adding an appropriate amount of As,which is more valuable than commercial Fe-As products.The Fe-25% As alloy with low toxicity and a relatively high density(7.635 g·cm^(-3)) provides an ultra-high compressive strength(1989.19 MPa),while the Fe-65% As alloy owns the maximum Vickers hardness(HVo.5 899.41).After leaching by the toxicity characteristic leaching procedure(TCLP),these alloys could still maintain good mechanical performance,and the strengthening mechanisms of Fe-As alloys before and after leaching were clarified.Changes in the grain size,micro structure,and phase distribution induced significant differences in the compressive strength and hardness.
文摘Alumina-(0 similar to 20 vol. pct) iron composites were fabricated by hot-pressing of well-mixed-alumina and iron powders at 1400 degreesC and 30 MPa for 30 min. Hot-pressed bodies with nearly theoretical density were obtained for addition up to 10 vol. pct Fe, but relative density decreased gradually with further increase in Fe addition. The materials exhibit a homogeneous dispersion of Fe. Fracture strength of the composites exhibits a maximum value of 604 MPa at 15 vol. pct Fe, which is 1.5 times that of alumina alone. Fracture toughness increases with the increase in Fe content, reaching 7.5 MPa.m(1/2) at 20 vol. pct Fe. The theoretical values of fracture toughness was calculated and compared with the experimental one. Toughening mechanisms of the composites are also discussed.
基金financially supported by the Wenzhou Public Welfare Technology Research Industry Project(No.G20140042)。
文摘The three-layered(W-60 vol%Cu/W-40 vol%Cu/W-20 vol%Cu)W/Cu functionally graded material(FGM)containing a Cu network structure was fabricated at different temperatures by hot-pressed sintering produced from copper-coated tungsten powders.The effects of various sintering temperatures on relative density,microstructure,thermal conductivity,hardness and flexural strength were investigated.Scanning electron microscopy(SEM)and X-ray diffraction(XRD)analysis show that a Cu network extends throughout the W/Cu FGM specimens sintered at 1065℃and the graded structure can be retained perfectly,and W particles are distributed homogeneously.The low-temperature sintering densification of W/Cu FGM arises because the sintering mode of the copper-coated tungsten particles includes just sintering Cu to Cu,rather than Cu to W,Cu to Cu and W to W,as required for conventional powder particles.The relative density of W/Cu FGM sintered at 1065℃for 3 h under a load of25 MPa is 96.1%.The thermal conductivity is up to204 W·m^-1·K^-1 at normal temperature and 150 W·m^-1·K^-1at 800℃.And the Vickers hardness varies with the gradient of different layers from 3.34 to 4.05 GPa.
基金financially supported by the Program for Changjiang Scholars and Innovative Research Teams in University(PCSIRT)(No.IRT0713)
文摘12 vol%WCp/2024Al composite was fabricated from mixed powders by hot-pressing at various tempera-tures. Investigation of the interfacial reaction between the WC phase and the Al alloy matrix was performed by X-ray diffraction （XRD）, transmission electron microscope （TEM） and energy dispersive spectroscopy （EDS）. A multiple layer interface structure, which is composed of Al/ WAl12/AlnC3/WC, is found to form by the interfacial reaction during hot-pressing. Further study shows that the AlaC3 layer forms along with a given crystal orientation of WC phase and might retard the interfacial reaction process.
基金financially supported by DST, New Delhi through the ‘Fast Track Young Scientist Research Project’(No. SR/FTP/PS-23/2009)
文摘Synthesis and ion transport properties of hot-pressed solid polymer electrolytes （SPEs）, （l-x） PEO： x KI, where x is the content of KI in wt%, are reported. A hot-press technique has been used for the formation of the polymeric membranes in place of the usual solution cast method. The composition （80 PEO：20 KI） was identified as the highest conducting polymer electrolyte on the basis of compositional dependent conductivity studies of PEO：KI films. A conductivity enhancement of more than two orders of magnitude from that of the pure PEO was achieved. Materials characterization and ion transport mechanism were explained by using various experimental techniques.
文摘Densification, phase transformation and fracture toughness were studied in hot-pressed Si_3N_4 seeded by in-houseproduced large, elongated β-Si_3N_4 seeds. A mixture of Y_2O_3-Al_2O_3 was used as the sintering aid. Concentration ofseeds were varied from 0 to 6 wt pct and the sintering time at 1700℃ was varied from 1 to 4 h. Maximum fracturetoughness of 9.0 MPam^(1/2) was measured in samples containing 5 wt pct seeds, hot pressed at 1700℃ for 4 h.
文摘Ⅰ. INTRODUCTIONSilicon nitride （Si<sub>3</sub>N<sub>4</sub>）ceramics is among the most hopeful structural materials with excellent mechanical and thermal properties. However, it is a brittle material. Fiber-reinforcement has been proved to be an effective approach to improving the
基金For financial support,the authors are grateful to the funding support from the China Postdoctoral Science Foundation under grant number of 2019M653619the National Natural Science Foundation of China under grant numbers of 52006167,51825604 and 51721004the 111 Project under grant number of B16038.
文摘SnSe-based thermoelectric materials are being explored since they have potential high thermoelectric figure of merit.We synthesized polycrystalline Al_(x)Sn_(1-x)Se(x=0.01,0.02,0.03 and 0.04)by hot-pressing method,and combined theoretical estimation with experimental measurement to investigate the in-fluence of Al doping on thermoelectric properties of SnSe.It was found that dopant Al can effectively adjust the band structure of SnSe by introducing intermediate band.Al doping with low content(x=0.01 and 0.02)can introduce a single intermediate band close to the valence band maximum or conduction band minimum,achieving band engineering optimization.In high temperature region(498 K<T<823 K),the electronic transport properties significantly enhance with thermal excitation.The lattice thermal conductivity reduces with the Al atomic point defect scattering,leading to a low thermal conductivity of 0.47 W m^(-1) K^(-1) in Al_(0.04)Sn_(0.96)Se at 823 K.As a result,a high ZT of 0.84 at 823 K is obtained from the Al_(0.04)Sn_(0.96) Se perpendicular to the pressing direction,which is 58.5%larger than that of SnSe.In addition,dopant Al can adjust the anisotropy of polycrystalline SnSe.The anisotropy of electronic properties are enhanced with low doping level(x=0.01,0.02)and suppressed with high doping level(x=0.03,0.04).
基金Project supported by the Major Project of“Science and Technology Innovation 2025”in Ningbo City,China(Grant Nos.2018B10086 and 2018B10017).
文摘The Nd-Fe-B magnets are pre-sintered and then processed with hot-pressing,and the resulting magnets are called the hot-pressed pretreated(HPP)magnets.The coercivity of the HPP magnets increases as the annealed temperature increases.When the annealing temperature is 900℃,the coercivity of the magnet is only 17.6 kOe(1 Oe=79.5775 A·m^-1),but when the annealing temperature rises up to 1060℃,the coercivity of the magnet reaches 23.53 kOe,which is remarkably increased by 33.7%.The microstructure analysis indicates that the grain surface of the HPP magnet becomes smoother as the annealed temperature increases.The microstructure factorαis changed according to the intrinsic coercivity model formula.Theαof the magnet at 900℃is only 0.578,but it is 0.825 at 1060℃.Microstructural optimization is due mainly to the increase of coercivity of the HPP magnet.
基金supported by the National Key Research and Development Program of China(No.2021YFB3701801)the Regional Innovation and Development Joint Fund of National Natural Science of China(No.U20A20236)。
文摘A new NiCu alloy was developed and utilized as binder phase for WC composites.The composites with spherical cast WC particle contents of 55-65 wt.%were prepared by rapid hot-pressing technique.The microstructures were characterized by scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDS),and transmission electron microscopy(TEM).The results reveal that the cast WC particles are uniformly dispersed within the NiCu matrix.The interface between WC and NiCu alloy is clear with no additional phase observed.Mechanical properties testing indicates that the hardness of the composite shows minimal variation as the cast WC particle content increases.Both the transverse rupture strength(TRS)and fracture toughness show a comparable decline,while the impact toughness first increases and then decreases.The NiCu alloy matrix plays a critical role in enhancing the fracture toughness of the composite.However,at high strain rates,the impact toughness deteriorates due to strain rate hardening of the NiCu matrix and a reduced density resulting from the higher WC content.
基金financially supported by the NationalNatural Science Foundation of China (No. 51574023)the National Key Research and Development Program ofChina (No. 2016YFB0600701)
文摘HyperCoal was prepared from low-rank coal via high-temperature solvent extraction with N-methylpyrrolidone as an extraction solvent and a liquid-to-solid ratio of 50 mL/g in a high-temperature and high-pressure reactor. When HyperCoal was used as a binder and pulverized coal was used as the raw material, the compressive strength of the hot-pressed briquettes(each with a diameter of 20 mm and mass of 5 g) under different conditions was studied using a hot-pressing mold and a high-temperature furnace. The compressive strength of the hot-pressed briquettes was substantially improved and reached 436 N when the holding time period was 15 min, the hot-pressing temperature was 673 K, and the HyperCoal content, was 15 wt%. Changes in the carbonaceous structure, as reflected by the intensity ratio between the Raman G-and D-bands(IG/ID), strongly affected the compressive strength of hot-pressed briquettes prepared at different hot-pressing temperatures. Compared with cold-pressed briquettes, hot-pressed briquettes have many advantages, including high compressive strength, low ash content, high moisture resistance, and good thermal stability; thus, we expect that hot-pressed briquettes will have broad application prospects.
基金financial support of National Key Research and Development Program of China (No. 2017YFA0403803)the National Natural Science Foundation of China (Nos.51525401, 51774065, 51601028, 51690163)+1 种基金Dalian Support Plan for Innovation of High-level Talents (Top and Leading Talents, 2015R013)fundamental research funds for the central universities (Nos. DUT18RC(3)042, DUT17RC(3)108)
文摘B4Cp/6061Al composites have become important structural and functional materials and can be fabricated by powder metallurgy and subsequent hot rolling. In this work, the effects of the hot-pressing temperature on microstructures and mechanical behaviors of the B4Cp/6061Al composites were investigated. The results showed that compared with the T4 heat treated B4Cp/6061Al composite hot pressed at 560℃, the yield strength and failure strain of the composites hot pressed at 580℃ were increased to 235 MPa and 18.4%, respectively. This was associated with the interface bonding strength between the B4C particles and the matrix. However, the reaction products, identified to be MgAl2O4 phases, were detected in the composites hot pressed at 600℃. The formation of the MgAl2O4 phases resulted in the Mg depletion, thus reducing the yield strength to 203.5 MPa after the T4 heat treatment due to the effect of the solid solution strengthening being weakened. In addition, the variation of hardness and electrical conductivity was mainly related to the Mg content in the matrix. Based on the as-rolled microstructures observed by SEM, SR-μCT and fracture surfaces, the deformation schematic diagram was depicted to reflect the tensile deformation process of the composites.
基金financially supported by the National Natural Science Foundation of China(Nos.51973150 and 21674076)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.19KJA320009)a Project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)。
文摘Piezoelectric poly(vinylidene fluoride)(PVDF)has received considerable attention due to its ability of interconverting mechanical into electric energies and potential applications in wearable electronics.To achieve piezoelectricity,it is important to simultaneously control the formation of polar phases,crystallinity,and dipole alignments in PVDF-based films.Here we demonstrate that piezoelectricity can be obtained by directly hot-pressing PVDF films sandwiched between chitosan or cellulose films.The electrostatic interactions between PVDF and chitosan or cellulose enabled an exceptional high content of polar phases(β-andγ-phases)up to 90%and a measured piezoelectric charge coefficient d_(33)of up to-30 pC/N.This study provides a simple and low-cost approach for obtaining piezoelectric PVDF films used for sensors,actuators,and energy harvesters.
基金supported by the National Key R&D Program of China (Grant No.2020YFA0710500)The authors acknowledge the basic scientific research business expenses Program of Xi’an Jiaotong University (Grant No.xzy022022053)the Independent Research Project of the State Key Laboratory of Electrical Insulation and Power Equipment (Grant No.EIPE23303)for financial support.
文摘Safety issues induced by infinite anode volume change and uncontrolled lithium(Li)dendrite growth have become the biggest obstacle to the practical application of Li metal batteries.In addition,the tra-ditional rolling method makes it difficult to manufacture thin Li foil with high mechanical strength and low Li content.Herein,a three-dimensional(3D)lithophilic carbon paper/copper(Cu)current collector hybrid anode with ultra-low Li metal content is prepared by a hot-pressing method.The highly re-versible and stable lithiophilic layer LiC_(x) formed in situ by heating/pressing treatment provides abun-dant nucleation sites and reduces the Li nucleation overpotential,thereby effectively suppressing Li den-drite growth.Moreover,the volume change and pulverization problems of Li metal anode during depo-sition/stripping also can be accommodated by the 3D skeleton.The optimization effect has been directly confirmed by in-situ optical and ex-situ scanning electron microscope observation.Therefore,highly sta-ble performance(158.4 mA h g^(-1) at 2 C after 200 cycles with a capacity retention of 95.24%)in Li@LCP-Cu||NCM811 coin cell can be achieved.Furthermore,the solid-state battery assembled with the hybrid anode,poly(vinylidene fluoride)(PVDF)-based polymer electrolyte and polyethylene oxide(PEO)interface functional layer also exhibits the best electrochemical and safety performance,which also proves that the Li@LCP-Cu anode has great potential for application in solid-state batteries.
基金supported by the National Natural Science Foundation of China (50575034)
文摘FeAl intermetallic compound with different contents of rare earth oxide La2O3 addition was prepared by hot pressing the mechanically alloyed powders.Effect of La2O3 on microstructure and high-temperature wear property of the sintered FeAl samples was investigated in this paper.The results showed that 1 wt.% La2O3 addition could refine the microstructure and increase the density of the FeAl intermetallic compound,and correspondingly improved the high-temperature wear resistance.SEM and EDS analyses of the wo...
基金Funded by the National Engineering and Research Center for Commercial Aircraft Manufacturing(No.SAMC 13-JS-15-034)
文摘A hot-press tackified preform was used to improve the uniformity of the laminates thickness and the mechanical properties of the obtained laminates were studied using vacuum assisted resin transfer molding（VARTM）. Two modified preforms were prepared under 0.1 and 0.6 MPa in an autoclave and then were used to fabricate the laminates via VARTM. Permeability and thickness distribution of the laminates were obtained by using a special device. Moreover, the tensile and compressive strengths of the obtained laminates were studied and compared with the unmodified ones. Results show that the tackified laminates present a maximum and minimum thickness under 0.1 and 0.6 MPa, respectively. The thicknesses and in-plane permeability of the tackified laminates, with better thickness uniformity, are significantly decreased compared with that of the unmodified cases, while the tensile and compressive strengths of the tackified laminates are improved obviously. Results show that the mechanical property of the tackified laminates prepared by hotpressing at 0.1 MPa is better than that processed at 0.6 MPa.
基金supported by the National Natural Science Foundation of China(No.50105011)
文摘A new pressing method was proposed for hot-pressing process. Experimental results indicated that the porosity in Al2O3/TiC/ Ni/Mo (hereafter called AI2O3/TiC composite) composite compacts decreases by 6% after adopting this new technique, compared to traditional hot-pressing technique under the same sintering temperature. The flexural strength and Vicker hardness increase from 883 MPa to 980 MPa and from 16 GPa to 21.1 GPa, respectively. A theoretical model was given to analyze the densification mechanism of the composite in the process of repetitious-hot-pressing.
基金Science Foundation for Distinguished Young Scholars of Henan Province (6521002700)
文摘In this work, the tungsten particulate reinforced Al2O3 dispersion strengthened copper base composites were successfully fabricated by using a vacuum hot-press sintering method. With the test temperature varying from 650 to 950 ℃ and the strain rate varying from 0.01 to 5 s-1, the W(50)/Cu-Al2O3 composites were isothermally compressed on a Gleeble-1500D thermal simulator. The true stress-strain curves of the W(50)/Cu-Al2O3 under different test conditions were obtained. The dynamic recrystallization of the W(50)/Cu-Al2O3 composite occurs during the isothermal compression. The constitutive equations and the hot deformation activation energy of W(50)/Cu-Al2O3 composites were calculated on the basis of the above experimental results.
基金Item Sponsored by National Natural Science Foundation of China(50904022)Education Department of Hebei Province Outstanding Youth Fund Project of China(Y2011116)
文摘BN-MgA1ON composites were prepared by hot-pressing sintering under nitrogen atmosphere with BN-Mg- A1ON composite powders as raw material and Y2 O3 as sintering additive. Based on thermodynamic analysis, the oxi- dation resistance of BN-MgAION composites was investigated and the dynamics of oxidation process was also ana- lyzed. The oxidation process and the micro-morphology of the samples before and after oxidation were characterized by X-ray diffraction and scanning electron microscopy. The dynamics of oxidation resistance of the BN-MgA1ON composites was investigated via the analysis of the constant temperature oxidation mass gain curves. The results show that the main components of the material are MgA1ON, Sialon, BN and CaYAI3 07 at 1 650--1750 ＊C, and the content of CaYA1307 decreases as the sintering temperature increases. The BN-MgA1ON composites prepared at 1750 ℃ is uniform and compact with the balanced distributions of A1, Mg, O, and N. The oxidation process of BN- MgA1ON composites in air mainly consists of MgAION, Sialon and BN oxidation. The section after being oxidized at 1000--1300 ℃ involves three layers, namely, the outer layer, the middle layer and the inner layer. The oxidation process follows the parabola model. The apparent activation energy of the oxidation process is 2.13 × 10 5 J/mol and the frequency factor is 4.66 × 10 6.
