The bulk Ti3SiC2 specimens with less than 1 wt% TiC impurity were prepared by vacuum sintering technique, and the average grain size was about 5-6 μm in the elongated direction. When the sintering temperature, soakin...The bulk Ti3SiC2 specimens with less than 1 wt% TiC impurity were prepared by vacuum sintering technique, and the average grain size was about 5-6 μm in the elongated direction. When the sintering temperature, soaking time and heating rate were 1 400 ℃, 1 h and 10℃·min-1, respectively, the highest relative density of Ti3SiC2 specimens could reach 97.8%. Meanwhile, the lowest coefficient of friction （COF） and wear rate （WR） of the Ti3SiC2 samples were 0.55 and 1.37×10-3 mm3（Nm）-1 at a sliding speed of 0.35 m/s, load pressure of 10 N and ambient condition, respectively. The COF of the Ti3SiC2 sample reduced with the increasing of the load pressure, while the WRs fluctuated little. The WR increased with the increasing of the sliding speed, and weakly influenced the COF. These changing behaviors could be attributed to the presence and coverage of the amorphous mixture oxide film ofTi, Si, A1, and Fe on the Ti3SiC2 friction surface. The self- antifriction mechanism led to reducing of the COF. The increasing of the WR was attributed to the wearing consumption.展开更多
Efforts are underway to establish a permanent lunar base on the Moon. In situ lunar regolith is anticipated to be useful as a building material after sintering. However, sintering lunar regolith into a large-scale str...Efforts are underway to establish a permanent lunar base on the Moon. In situ lunar regolith is anticipated to be useful as a building material after sintering. However, sintering lunar regolith into a large-scale structure presents challenges. Therefore, the key to lunar construction lies in assembling multiple small-sized sintered modules into a stable, large-sized structure. This study explored the feasibility of welding the sintered HUST-1 lunar regolith simulant(HLRS) using a laser device and conducted experiments using lasers of varying power. The microstructure, mineral composition, element distribution, and shear strength of the welded joint were investigated. A few low-melting minerals were fused and vaporized during welding, leading to the generation of thermal decomposition gas. Furthermore, the welded joint exhibited numerous micro-cracks, pores, and bubbles,resulting in reduced weld shear strength. Finally, the influence of laser power on weld shear strength was investigated, revealing that the highest shear strength(15.69 N/cm) was achieved at a laser power of 1000 W. This study demonstrates the feasibility of laser welding of sintered HLRS for the first time, with potential applications in lunar base construction.展开更多
Establishing a base on the Moon is one of the new goals of human lunar exploration in recent years.Sintered lunar regolith is one of the most potential building materials for lunar bases.The physical,mechanical and th...Establishing a base on the Moon is one of the new goals of human lunar exploration in recent years.Sintered lunar regolith is one of the most potential building materials for lunar bases.The physical,mechanical and thermal properties of sintered lunar regolith are vital performance indices for the structural design of a lunar base and analysis of many critical mechanical and thermal issues.In this study,the HUST-1 lunar regolith simulant(HLRS)was sintered at 1030,1040,1050,1060,1070,and 1080℃.The effect of sintering temperature on the compressive strength was investigated,and the exact value of the optimum vacuum sintering temperature was determined between 1040 and 1060℃.Then,the microstructure and material composition of vacuum sintered HLRS at different temperatures were characterized.It was found that the sintering temperature has no significant effect on the mineral composition in the temperature range of 1030-1080℃.Besides,the heat capacity,thermal conductivity,and coefficient of thermal expansion(CTE)of vacuum sintered HLRS at different temperatures were investigated.Specific heat capacity of sintered samples increases with the increase of test temperature within the temperature range from-75 to 145℃.Besides,the thermal conductivity of the sintered sample is proportional to density.Finally,the two temperatures of 1040 and 1050℃were selected for a more detailed study of mechanical properties.The results showed that compressive strength of sintered sample is much higher than tensile strength.This study reveals the effects of sintering temperature on the physical,mechanical and thermal properties of vacuum sintered HLRS,and these material parameters will provide support for the construction of future lunar bases.展开更多
The WC-Co composite coatings bonded tightly to steel substrate have been made by vacuum fusion sinter （VFS）. The concentration distribution of some components were measured by the electron probe, and the microstruct...The WC-Co composite coatings bonded tightly to steel substrate have been made by vacuum fusion sinter （VFS）. The concentration distribution of some components were measured by the electron probe, and the microstructure and morphology of VFS coatings were observed and analyzed by SEM, X-ray diffractometer and microhardness tester. Diffusion coefficient of every element was calculated by using the experimental results. The influence of the interracial diffusion on the microstructure, Vickers hardness and interracial bond strength of the VFS coatings was studied in detail. The experimental results show that there is a metallurgical bond area between the VFS WC-Co coatings and the steel substrate. The VFS coatings are characterized by the gradient hardness of the interface and the high bond strength to the steel substate, both of which are beneficial to the improvement of the wear resistance and corrosion resistance.展开更多
Regenerative artificial bone material and bone parts were fabricated using vacuum-sintered bodies of a “titanium medical apatite (TMA?)” that is formed by chemically connecting Ti oxide molecules to the reactive [Ca...Regenerative artificial bone material and bone parts were fabricated using vacuum-sintered bodies of a “titanium medical apatite (TMA?)” that is formed by chemically connecting Ti oxide molecules to the reactive [Ca10 (PO4 )6 ] group of hydroxyapatite (HAp). Sintering at temperatures of 1273 - 1773 K caused this TMA sintered bodies to recrystallize and form a varying mix of α-TCP (tricalcium phosphate), β-TCP and Perovskite-CaTiO3 phases. The Perovskite crystals proved to be quite stable and hard, forming a uniform distribution of similarly sized fibers in all directions under vacuum sintering, but an irregular distribution and size when sintered in the presence of oxygen. Complete recrystallization was achieved by vacuum sintering at temperatures in excess of 1473 K. In particular, TMA vacuum-sintered bodies at 1573 K are given the maximum value;a Vickers hardness of 400, a bending strength of 43 MPa, a compressive strength of 270 MPa and a density of approximately 2300 kg/m3 was achieved that closely corresponds to that of compact bone or a tooth. As these TMA bodies could also be cut into various forms, they are considered a promising biomaterial for use as artificial bone in the regeneration of natural bone, or to provide reinforcement of bone junctions in dental and orthopedic surgery.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
A new kind of sintering process, combined sintering process. i.e. vacuum sintering plus hot isolate pressure sintering (HIP), was introduced for producing ultrafine WC-10% Co (mass fraction. so as the follows) cemen...A new kind of sintering process, combined sintering process. i.e. vacuum sintering plus hot isolate pressure sintering (HIP), was introduced for producing ultrafine WC-10% Co (mass fraction. so as the follows) cemented carbides. The effects of some processing parameters on the microstructure and mechanical properties of the obtained cemented carbides were studied. The results show that the rapid shrinkage and the pronounced densification of tile cemented carbides took place during the vacuum sintering stage, which is intinaately correlated with the local liquid sintering occurred during this earl} sintering stage for the high surface activity of ultrafine WC-Co powder. The way of high pressure imposing. isothermal treatment cycle during ac.acuum sintering and HIP sintering stage directly influence the densitication of compacts and the mechanical properties of the produced WC-10%Co cemented carbides.展开更多
Si2N2O ceramics were prepared using amorphous Si3N4 as the raw material and Li2CO3 as the sintering additive through vacuum multi-stage sintering.The influence of the Li2CO3 addition(0%,1%,2%,3%,and 5%,by mass)on the ...Si2N2O ceramics were prepared using amorphous Si3N4 as the raw material and Li2CO3 as the sintering additive through vacuum multi-stage sintering.The influence of the Li2CO3 addition(0%,1%,2%,3%,and 5%,by mass)on the phase composition,the microstructure,the porosity,the mechanical properties,the dielectric constant and the tangent of the dielectric loss angle of the porous Si2N2O ceramics was investigated.The results reveal that a suitable addition of Li2CO3 can promote the generation of Si2N2O but excessive or inadequate Li2CO3 causes decomposition of Si2N2O ceramics.The prepared porous Si2N2O ceramics have good mechanical properties,good thermal shock resistance,and low dielectric properties,which have excellent potential for application in microwave sintering furnaces.展开更多
基金Funded by the Natural Science Foundation of Hubei Province(No.2012FFB05104)the National Natural Science Foundation of China (No.51275370)+3 种基金the Fundamental Research Funds for the Central Universities (No.2010-II-020)the Project for Science and Technology Plan of Wuhan City (No.2013010501010139)the Academic Leader Program of Wuhan City (No.201150530146)the Project for Teaching and Research Project of Wuhan University of Technology(No.2012016)
文摘The bulk Ti3SiC2 specimens with less than 1 wt% TiC impurity were prepared by vacuum sintering technique, and the average grain size was about 5-6 μm in the elongated direction. When the sintering temperature, soaking time and heating rate were 1 400 ℃, 1 h and 10℃·min-1, respectively, the highest relative density of Ti3SiC2 specimens could reach 97.8%. Meanwhile, the lowest coefficient of friction （COF） and wear rate （WR） of the Ti3SiC2 samples were 0.55 and 1.37×10-3 mm3（Nm）-1 at a sliding speed of 0.35 m/s, load pressure of 10 N and ambient condition, respectively. The COF of the Ti3SiC2 sample reduced with the increasing of the load pressure, while the WRs fluctuated little. The WR increased with the increasing of the sliding speed, and weakly influenced the COF. These changing behaviors could be attributed to the presence and coverage of the amorphous mixture oxide film ofTi, Si, A1, and Fe on the Ti3SiC2 friction surface. The self- antifriction mechanism led to reducing of the COF. The increasing of the WR was attributed to the wearing consumption.
基金supported by the National Key Research and Development Program of China(Grant Nos.2023YFB3711300 and 2021YFF0500300)the Strategic Research and Consulting Project of the Chinese Academy of Engineering(Grant Nos.2023-XZ-90 and 2023-JB-09-10)。
文摘Efforts are underway to establish a permanent lunar base on the Moon. In situ lunar regolith is anticipated to be useful as a building material after sintering. However, sintering lunar regolith into a large-scale structure presents challenges. Therefore, the key to lunar construction lies in assembling multiple small-sized sintered modules into a stable, large-sized structure. This study explored the feasibility of welding the sintered HUST-1 lunar regolith simulant(HLRS) using a laser device and conducted experiments using lasers of varying power. The microstructure, mineral composition, element distribution, and shear strength of the welded joint were investigated. A few low-melting minerals were fused and vaporized during welding, leading to the generation of thermal decomposition gas. Furthermore, the welded joint exhibited numerous micro-cracks, pores, and bubbles,resulting in reduced weld shear strength. Finally, the influence of laser power on weld shear strength was investigated, revealing that the highest shear strength(15.69 N/cm) was achieved at a laser power of 1000 W. This study demonstrates the feasibility of laser welding of sintered HLRS for the first time, with potential applications in lunar base construction.
基金supported by the National Key Research and Development Program of China(Nos.2021YFF0500300 and 2023YFB3711300)the Strategic Research and Consulting Project of the Chinese Academy of Engineering(Nos.2023-XZ-90 and 2023-JB-09-10).
文摘Establishing a base on the Moon is one of the new goals of human lunar exploration in recent years.Sintered lunar regolith is one of the most potential building materials for lunar bases.The physical,mechanical and thermal properties of sintered lunar regolith are vital performance indices for the structural design of a lunar base and analysis of many critical mechanical and thermal issues.In this study,the HUST-1 lunar regolith simulant(HLRS)was sintered at 1030,1040,1050,1060,1070,and 1080℃.The effect of sintering temperature on the compressive strength was investigated,and the exact value of the optimum vacuum sintering temperature was determined between 1040 and 1060℃.Then,the microstructure and material composition of vacuum sintered HLRS at different temperatures were characterized.It was found that the sintering temperature has no significant effect on the mineral composition in the temperature range of 1030-1080℃.Besides,the heat capacity,thermal conductivity,and coefficient of thermal expansion(CTE)of vacuum sintered HLRS at different temperatures were investigated.Specific heat capacity of sintered samples increases with the increase of test temperature within the temperature range from-75 to 145℃.Besides,the thermal conductivity of the sintered sample is proportional to density.Finally,the two temperatures of 1040 and 1050℃were selected for a more detailed study of mechanical properties.The results showed that compressive strength of sintered sample is much higher than tensile strength.This study reveals the effects of sintering temperature on the physical,mechanical and thermal properties of vacuum sintered HLRS,and these material parameters will provide support for the construction of future lunar bases.
文摘The WC-Co composite coatings bonded tightly to steel substrate have been made by vacuum fusion sinter （VFS）. The concentration distribution of some components were measured by the electron probe, and the microstructure and morphology of VFS coatings were observed and analyzed by SEM, X-ray diffractometer and microhardness tester. Diffusion coefficient of every element was calculated by using the experimental results. The influence of the interracial diffusion on the microstructure, Vickers hardness and interracial bond strength of the VFS coatings was studied in detail. The experimental results show that there is a metallurgical bond area between the VFS WC-Co coatings and the steel substrate. The VFS coatings are characterized by the gradient hardness of the interface and the high bond strength to the steel substate, both of which are beneficial to the improvement of the wear resistance and corrosion resistance.
文摘Regenerative artificial bone material and bone parts were fabricated using vacuum-sintered bodies of a “titanium medical apatite (TMA?)” that is formed by chemically connecting Ti oxide molecules to the reactive [Ca10 (PO4 )6 ] group of hydroxyapatite (HAp). Sintering at temperatures of 1273 - 1773 K caused this TMA sintered bodies to recrystallize and form a varying mix of α-TCP (tricalcium phosphate), β-TCP and Perovskite-CaTiO3 phases. The Perovskite crystals proved to be quite stable and hard, forming a uniform distribution of similarly sized fibers in all directions under vacuum sintering, but an irregular distribution and size when sintered in the presence of oxygen. Complete recrystallization was achieved by vacuum sintering at temperatures in excess of 1473 K. In particular, TMA vacuum-sintered bodies at 1573 K are given the maximum value;a Vickers hardness of 400, a bending strength of 43 MPa, a compressive strength of 270 MPa and a density of approximately 2300 kg/m3 was achieved that closely corresponds to that of compact bone or a tooth. As these TMA bodies could also be cut into various forms, they are considered a promising biomaterial for use as artificial bone in the regeneration of natural bone, or to provide reinforcement of bone junctions in dental and orthopedic surgery.
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A new kind of sintering process, combined sintering process. i.e. vacuum sintering plus hot isolate pressure sintering (HIP), was introduced for producing ultrafine WC-10% Co (mass fraction. so as the follows) cemented carbides. The effects of some processing parameters on the microstructure and mechanical properties of the obtained cemented carbides were studied. The results show that the rapid shrinkage and the pronounced densification of tile cemented carbides took place during the vacuum sintering stage, which is intinaately correlated with the local liquid sintering occurred during this earl} sintering stage for the high surface activity of ultrafine WC-Co powder. The way of high pressure imposing. isothermal treatment cycle during ac.acuum sintering and HIP sintering stage directly influence the densitication of compacts and the mechanical properties of the produced WC-10%Co cemented carbides.
基金The authors would like to thank the National Key R&D Program of China(2017YFB0304000)National Natural Science Foundation of China(51932008,51772277)Central China Thousand Talents Project(2042005100111).
文摘Si2N2O ceramics were prepared using amorphous Si3N4 as the raw material and Li2CO3 as the sintering additive through vacuum multi-stage sintering.The influence of the Li2CO3 addition(0%,1%,2%,3%,and 5%,by mass)on the phase composition,the microstructure,the porosity,the mechanical properties,the dielectric constant and the tangent of the dielectric loss angle of the porous Si2N2O ceramics was investigated.The results reveal that a suitable addition of Li2CO3 can promote the generation of Si2N2O but excessive or inadequate Li2CO3 causes decomposition of Si2N2O ceramics.The prepared porous Si2N2O ceramics have good mechanical properties,good thermal shock resistance,and low dielectric properties,which have excellent potential for application in microwave sintering furnaces.
