Zirconium oxide （ZrO：） and boron carbide （B4C） were added to ZrB2 raw powders to prepare ZrB2 porous ceramics by reactive spark plasma sintering （RSPS）. The reactions between ZrO2 and B,C which produce ZrB2 and...Zirconium oxide （ZrO：） and boron carbide （B4C） were added to ZrB2 raw powders to prepare ZrB2 porous ceramics by reactive spark plasma sintering （RSPS）. The reactions between ZrO2 and B,C which produce ZrB2 and gas （such as CO and B2O3） result in pore formation. X-Ray Diffraction results indicated that the products phase was ZrB2 and the reaction was completed after the RSPS process. The porosity could be controlled by changing the ratio of synthesized ZrB2 to raw ZrB2 powders. The porosity of porous ceramics with 20 wt% and 40 wt% synthsized ZrB2 are 0.185 and 0.222, respectivly. And dense ZrB：SiC ceramic with a porosity of 0.057 was prepared under the same conditions for comparison. The pores were homogeneously distributed within the microstructure of the porous ceramics. The results indicate a promising method for preparing porous ZrB：based ceramics.展开更多
In this paper, the synthesis of Ti_3 SiC_2 from SiC/Ti powder using reactive spark plasma sintering(R-SPS) in the temperature range of 1300-1400 ℃ is reported. The results show that the purity of Ti_3 SiC_2 is improv...In this paper, the synthesis of Ti_3 SiC_2 from SiC/Ti powder using reactive spark plasma sintering(R-SPS) in the temperature range of 1300-1400 ℃ is reported. The results show that the purity of Ti_3 SiC_2 is improved up to 75 wt% when the holding time is increased from 10 to 20 min at1400 ℃. The thermodynamic and experimental results indicate that Ti_3 SiC_2 formation takes place via the reaction of a pre-formed TiC phase with the silicides, formed from the eutectic compositions.Detailed analysis of mechanical behaviour indicates that samples with higher percentage of secondary phases exhibit higher microhardness and better resistance compared to the near single phase Ti_3 SiC_2.展开更多
B_(x)C-TiB_(2)ceramic composites were fabricated via reactive spark plasma sintering using TiC and B as the raw materials.The impact of B/TiC mole ratios on the phase compositions,densification behaviors,microstructu...B_(x)C-TiB_(2)ceramic composites were fabricated via reactive spark plasma sintering using TiC and B as the raw materials.The impact of B/TiC mole ratios on the phase compositions,densification behaviors,microstructure,and mechanical properties of the ceramic composites were investigated.The results showed that the stoichiometry of‘B_(x)C’could be tailored by changing initial boron content and the obtained B_(4.5)C,B_(6.5)C and B_(8.5)C phases have the same crystal structure(R-3 m).The excess of B enhanced the reaction between TiC and B,which released a large amount of hot energy and promoted the densification of the composites.The TB8.5 composite sintered at 1900°C had the best comprehensive mechanical properties,with hardness and flexural strength of 40.36 GPa and 551 MPa,respectively.The formation of nano-sized TiB_(2)grains induced by reaction were beneficial for improving the mechanical properties of these composites.展开更多
Ultrafine-grained Al_(2)O_(3)–rare earth:yttrium aluminium garnet(Al_(2)O_(3)–RE:YAG)(RE=Ce;Ce+Gd)composite ceramics were obtained for the first time by reactive spark plasma sintering(SPS)using commercially availab...Ultrafine-grained Al_(2)O_(3)–rare earth:yttrium aluminium garnet(Al_(2)O_(3)–RE:YAG)(RE=Ce;Ce+Gd)composite ceramics were obtained for the first time by reactive spark plasma sintering(SPS)using commercially available initial oxide powders.The effect of key sintering parameters(temperature,dwell time,and external pressure(P_(load)))on densification peculiarities,structural-phase states,and luminescent properties of composites was studied comprehensively.Differences in phase formation and densification between Ce-doped and Ce,Gd-codoped systems were shown.Parameters of reactive SPS,at which there is partial melting with the formation of near-eutectic zones of the Al_(2)O_(3)–YAG system/coexistence of several variations of the YAG-type phase,were established.Pure corundum–garnet biphasic ceramics with an optimal balance between microstructural and luminescence performance were synthesized at 1425℃/30 min/30–60 MPa.The external quantum efficiency(EQE)of the phosphor converters reached 80.7%and 72%with close lifetime of~63.8 ns,similar to those of commercial Ce:YAG materials,which is promising for further applications in the field of high-power white light-emitting diodes(WLEDs)and laser diodes(LDs).展开更多
Al2O3 dispersion-strengthened copper alloy was prepared by reactive synthesis and spark plasma sintering（SPS） process. Studies show that nano-sized c-Al2O3 particles with 27.4 nm mean size and 50-nm interval are hom...Al2O3 dispersion-strengthened copper alloy was prepared by reactive synthesis and spark plasma sintering（SPS） process. Studies show that nano-sized c-Al2O3 particles with 27.4 nm mean size and 50-nm interval are homogeneously distributed in copper matrix. The density of SPS alloy is about 99 %, meanwhile, the electrical conductivity of sintered alloy is 72 % IACS and the Rockwell hardness can reach to HRB 91.展开更多
A new class of high-entropy M3B4 borides of the Ta_(3)B_(4)-prototyped orthorhombic structure has been synthesized in the bulk form for the first time.Specimens with compositions of(V0.2Cr0.2Nb0.2Mo0.2Ta0.2)3B4 and(V0...A new class of high-entropy M3B4 borides of the Ta_(3)B_(4)-prototyped orthorhombic structure has been synthesized in the bulk form for the first time.Specimens with compositions of(V0.2Cr0.2Nb0.2Mo0.2Ta0.2)3B4 and(V0.2Cr0.2Nb0.2Ta0.2W0.2)_(3)B_(4) were fabricated via reactive spark plasma sintering of high-energy-ball-milled elemental boron and metal precursors.The sintered specimens were〜98.7%in relative densities with virtually no oxide contamination,albeit the presence of minor(4-5 vol%)secondary high-entropy M5B6 phases.Despite that Mo_(3)B_(4) or W_(3)B_(4) are not stable phase,20%of M03B4 and W3B4 can be stabilized into the high-entropy M3B4 borides.Vickers hardness was measured to be 18.6 and 19.8 GPa at a standard load of 9.8 N.This work has further expanded the family of different structures of high-entropy ceramics reported to date.展开更多
ZrB2 ceramics with various hexagonal BN(hBN)additions up to 37 vol%were reactively densified by spark plasma sintering using powder mixtures containing ZrB2,ZrN and boron.ZrN-boron based additives effectively promoted...ZrB2 ceramics with various hexagonal BN(hBN)additions up to 37 vol%were reactively densified by spark plasma sintering using powder mixtures containing ZrB2,ZrN and boron.ZrN-boron based additives effectively promoted the densification process,ZrB2 ceramics reached>99%relative density at 2000℃and an applied pressure of 60 MPa with only 5 vol%in-situ formed hBN,whereas the relative density of pure ZrB2 was only 91.2%at the same conditions.Increasing thehBN contents,the morphology of hBN grains gradually changed from quasi-spherical to flake dominated,which has substantial influence on their mechanical properties.In-situ ZrB2-10 vol%hBN ceramics demonstrated high flexural strength of 597±22 MPa,relatively low Young’s modulus of 406 GPa and good machinability,especially for the impressively large strain to failure(1.47×10^-3)which is superior to most of their counterparts in the ZrB2 based particulate reinforced ceramics.展开更多
基金Funded by the National Natural Science Foundation of China(No.51272190)the 111 Project(No.B13035)
文摘Zirconium oxide （ZrO：） and boron carbide （B4C） were added to ZrB2 raw powders to prepare ZrB2 porous ceramics by reactive spark plasma sintering （RSPS）. The reactions between ZrO2 and B,C which produce ZrB2 and gas （such as CO and B2O3） result in pore formation. X-Ray Diffraction results indicated that the products phase was ZrB2 and the reaction was completed after the RSPS process. The porosity could be controlled by changing the ratio of synthesized ZrB2 to raw ZrB2 powders. The porosity of porous ceramics with 20 wt% and 40 wt% synthsized ZrB2 are 0.185 and 0.222, respectivly. And dense ZrB：SiC ceramic with a porosity of 0.057 was prepared under the same conditions for comparison. The pores were homogeneously distributed within the microstructure of the porous ceramics. The results indicate a promising method for preparing porous ZrB：based ceramics.
文摘In this paper, the synthesis of Ti_3 SiC_2 from SiC/Ti powder using reactive spark plasma sintering(R-SPS) in the temperature range of 1300-1400 ℃ is reported. The results show that the purity of Ti_3 SiC_2 is improved up to 75 wt% when the holding time is increased from 10 to 20 min at1400 ℃. The thermodynamic and experimental results indicate that Ti_3 SiC_2 formation takes place via the reaction of a pre-formed TiC phase with the silicides, formed from the eutectic compositions.Detailed analysis of mechanical behaviour indicates that samples with higher percentage of secondary phases exhibit higher microhardness and better resistance compared to the near single phase Ti_3 SiC_2.
基金support from the National Natural Science Foundation of China(51901063),the Fundamental Research Funds for the Central Universities of China(JZ2021HGTB0094 and PA2021GDGP0059)is greatly acknowledged。
文摘B_(x)C-TiB_(2)ceramic composites were fabricated via reactive spark plasma sintering using TiC and B as the raw materials.The impact of B/TiC mole ratios on the phase compositions,densification behaviors,microstructure,and mechanical properties of the ceramic composites were investigated.The results showed that the stoichiometry of‘B_(x)C’could be tailored by changing initial boron content and the obtained B_(4.5)C,B_(6.5)C and B_(8.5)C phases have the same crystal structure(R-3 m).The excess of B enhanced the reaction between TiC and B,which released a large amount of hot energy and promoted the densification of the composites.The TB8.5 composite sintered at 1900°C had the best comprehensive mechanical properties,with hardness and flexural strength of 40.36 GPa and 551 MPa,respectively.The formation of nano-sized TiB_(2)grains induced by reaction were beneficial for improving the mechanical properties of these composites.
基金supported by the Russian Science Foundation(No.20-73-10242)Also,this work was partially supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22010301)+3 种基金the International Partnership Program of Chinese Academy of Sciences(No.121631KYSB20200039)the International Cooperation Project of Shanghai Science and Technology Commission(No.20520750200)Denis Yu.Kosyanov is grateful to the Council on grants of the President of the Russian Federation(No.SP-3221.2022.1)for supporting the studies devoted to obtaining advanced ceramic materialsThe SR XRD measurements were done at the shared research center SSTRC on the basis of the VEPP-4-VEPP-2000 complex at the Budker Institute of Nuclear Physics SB RAS.
文摘Ultrafine-grained Al_(2)O_(3)–rare earth:yttrium aluminium garnet(Al_(2)O_(3)–RE:YAG)(RE=Ce;Ce+Gd)composite ceramics were obtained for the first time by reactive spark plasma sintering(SPS)using commercially available initial oxide powders.The effect of key sintering parameters(temperature,dwell time,and external pressure(P_(load)))on densification peculiarities,structural-phase states,and luminescent properties of composites was studied comprehensively.Differences in phase formation and densification between Ce-doped and Ce,Gd-codoped systems were shown.Parameters of reactive SPS,at which there is partial melting with the formation of near-eutectic zones of the Al_(2)O_(3)–YAG system/coexistence of several variations of the YAG-type phase,were established.Pure corundum–garnet biphasic ceramics with an optimal balance between microstructural and luminescence performance were synthesized at 1425℃/30 min/30–60 MPa.The external quantum efficiency(EQE)of the phosphor converters reached 80.7%and 72%with close lifetime of~63.8 ns,similar to those of commercial Ce:YAG materials,which is promising for further applications in the field of high-power white light-emitting diodes(WLEDs)and laser diodes(LDs).
基金financially supported by the National Natural Science Foundation of China (No. 5043202)
文摘Al2O3 dispersion-strengthened copper alloy was prepared by reactive synthesis and spark plasma sintering（SPS） process. Studies show that nano-sized c-Al2O3 particles with 27.4 nm mean size and 50-nm interval are homogeneously distributed in copper matrix. The density of SPS alloy is about 99 %, meanwhile, the electrical conductivity of sintered alloy is 72 % IACS and the Rockwell hardness can reach to HRB 91.
基金an office of Naval Research MURI Program(Grant No.N00014-15-1-2863)Qizhang YAN and Jian LUO also acknowledge partial support from the Air Force Office of Scientific Research(Grant No.FA9550-19-1-01327)for the microscopy work.
文摘A new class of high-entropy M3B4 borides of the Ta_(3)B_(4)-prototyped orthorhombic structure has been synthesized in the bulk form for the first time.Specimens with compositions of(V0.2Cr0.2Nb0.2Mo0.2Ta0.2)3B4 and(V0.2Cr0.2Nb0.2Ta0.2W0.2)_(3)B_(4) were fabricated via reactive spark plasma sintering of high-energy-ball-milled elemental boron and metal precursors.The sintered specimens were〜98.7%in relative densities with virtually no oxide contamination,albeit the presence of minor(4-5 vol%)secondary high-entropy M5B6 phases.Despite that Mo_(3)B_(4) or W_(3)B_(4) are not stable phase,20%of M03B4 and W3B4 can be stabilized into the high-entropy M3B4 borides.Vickers hardness was measured to be 18.6 and 19.8 GPa at a standard load of 9.8 N.This work has further expanded the family of different structures of high-entropy ceramics reported to date.
基金supported financially by grants from the National Natural Science Foundation of China(NSFC)(No.51972243 and 51521001)。
文摘ZrB2 ceramics with various hexagonal BN(hBN)additions up to 37 vol%were reactively densified by spark plasma sintering using powder mixtures containing ZrB2,ZrN and boron.ZrN-boron based additives effectively promoted the densification process,ZrB2 ceramics reached>99%relative density at 2000℃and an applied pressure of 60 MPa with only 5 vol%in-situ formed hBN,whereas the relative density of pure ZrB2 was only 91.2%at the same conditions.Increasing thehBN contents,the morphology of hBN grains gradually changed from quasi-spherical to flake dominated,which has substantial influence on their mechanical properties.In-situ ZrB2-10 vol%hBN ceramics demonstrated high flexural strength of 597±22 MPa,relatively low Young’s modulus of 406 GPa and good machinability,especially for the impressively large strain to failure(1.47×10^-3)which is superior to most of their counterparts in the ZrB2 based particulate reinforced ceramics.
