The new ternary CM_2A_8(CaMg_2Al_(16)O_(27))and C_2M_2A_(14)(Ca_2Mg_2Al_(28)O_(46))pure and dense ceramics were first prepared by a hot-press sintering technique,and their physical and mechanical properties were inves...The new ternary CM_2A_8(CaMg_2Al_(16)O_(27))and C_2M_2A_(14)(Ca_2Mg_2Al_(28)O_(46))pure and dense ceramics were first prepared by a hot-press sintering technique,and their physical and mechanical properties were investigated.The purity of obtained CM_2A_8 and C_2M_2A_(14) ceramics reaches 98.1 wt%and 97.5 wt%,respectively.Their microstructure is dense with few observable pores,and their grain size is about a few dozen microns.For their physical properties,the average apparent porosity of CM_2A_8 and C_2M_2A_(14) ceramics is 0.18% and 0.13%,and their average bulk density is 3.66 g/cm^3 and 3.71 g/cm^3,respectively.The relative density of CM_2A_8 ceramic is 98.12%and that of C_2M_2A_(14)ceramic is 98.67%.The thermal expansivity(50–1400℃)of CM_2A_8 and C_2M_2A_(14) ceramics is 9.24×10^(–6)K^(–1) and 8.92×10^(–6)K^(–1),respectively.The thermal conductivity of CM_2A_8 and C_2M_2A_(14) ceramic is 21.32 W/(m·K)and 23.25 W/(m·K)at 25℃and 18.76 W/(m·K)and 19.42 W/(m·K)as temperature rises to 350℃,respectively.In addition,the mechanical properties are also achieved.For CM_2A_8 ceramic,the flexural strength is 248 MPa,the fracture toughness is 2.17 MPa·m^(1/2),and the Vickers hardness is 12.26 GPa.For C_2M_2A_(14) ceramic,the flexural strength is 262 MPa,the fracture toughness is 2.23 MPa·m^(1/2),and the Vickers hardness is 12.95 GPa.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
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
Hexagonal boron nitride(h-BN)ceramics have become exceptional materials for heat-resistant components in hypersonic vehicles,owing to their superior thermal stability and excellent dielectric properties.However,their ...Hexagonal boron nitride(h-BN)ceramics have become exceptional materials for heat-resistant components in hypersonic vehicles,owing to their superior thermal stability and excellent dielectric properties.However,their densification during sintering still poses challenges for researchers,and their mechanical properties are rather unsatisfactory.In this study,SrAl_(2)Si_(2)O_(8)(SAS),with low melting point and high strength,was introduced into the h-BN ceramics to facilitate the sintering and reinforce the strength and toughness.Then,BN-SAS ceramic composites were fabricated via hot press sintering using h-BN,SrCO_(3),Al_(2)O_(3),and SiO_(2) as raw materials,and effects of sintering pressure on their microstructure,mechanical property,and thermal property were investigated.The thermal shock resistance of BN-SAS ceramic composites was evaluated.Results show that phases of as-preparedBN-SAS ceramic composites are h-BN and h-SrAl_(2)Si_(2)O_(8).With the increase of sintering pressure,the composites’densities increase,and the mechanical properties shew a rising trend followed by a slight decline.At a sintering pressure of 20 MPa,their bending strength and fracture toughness are(138±4)MPa and(1.84±0.05)MPa·m^(1/2),respectively.Composites sintered at 10 MPa exhibit a low coefficient of thermal expansion,with an average of 2.96×10^(-6) K^(-1) in the temperature range from 200 to 1200℃.The BN-SAS ceramic composites prepared at 20 MPa display higher thermal conductivity from 12.42 to 28.42 W·m^(-1)·K^(-1) within the temperature range from room temperature to 1000℃.Notably,BN-SAS composites exhibit remarkable thermal shock resistance,with residual bending strength peaking and subsequently declining sharply under a thermal shock temperature difference ranging from 600 to 1400℃.The maximum residual bending strength is recorded at a temperature difference of 800℃,with a residual strength retention rate of 101%.As the thermal shock temperature difference increase,the degree of oxidation on the ceramic surface and 展开更多
基金supported by the National Natural Science Foundation of China (No. 51572019)the National Science Fund for Excellent Young Scholars of China (No. 51522402)
文摘The new ternary CM_2A_8(CaMg_2Al_(16)O_(27))and C_2M_2A_(14)(Ca_2Mg_2Al_(28)O_(46))pure and dense ceramics were first prepared by a hot-press sintering technique,and their physical and mechanical properties were investigated.The purity of obtained CM_2A_8 and C_2M_2A_(14) ceramics reaches 98.1 wt%and 97.5 wt%,respectively.Their microstructure is dense with few observable pores,and their grain size is about a few dozen microns.For their physical properties,the average apparent porosity of CM_2A_8 and C_2M_2A_(14) ceramics is 0.18% and 0.13%,and their average bulk density is 3.66 g/cm^3 and 3.71 g/cm^3,respectively.The relative density of CM_2A_8 ceramic is 98.12%and that of C_2M_2A_(14)ceramic is 98.67%.The thermal expansivity(50–1400℃)of CM_2A_8 and C_2M_2A_(14) ceramics is 9.24×10^(–6)K^(–1) and 8.92×10^(–6)K^(–1),respectively.The thermal conductivity of CM_2A_8 and C_2M_2A_(14) ceramic is 21.32 W/(m·K)and 23.25 W/(m·K)at 25℃and 18.76 W/(m·K)and 19.42 W/(m·K)as temperature rises to 350℃,respectively.In addition,the mechanical properties are also achieved.For CM_2A_8 ceramic,the flexural strength is 248 MPa,the fracture toughness is 2.17 MPa·m^(1/2),and the Vickers hardness is 12.26 GPa.For C_2M_2A_(14) ceramic,the flexural strength is 262 MPa,the fracture toughness is 2.23 MPa·m^(1/2),and the Vickers hardness is 12.95 GPa.
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.
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National Natural Science Foundation of China (52072088, 52072089)Natural Science Foundation of Heilongjiang Province (LH2023E061)+1 种基金Scientific and Technological Innovation Leading Talent of Harbin Manufacturing (2022CXRCCG001)Fundamental Research Funds for the Central Universities (3072023CFJ1003)。
文摘Hexagonal boron nitride(h-BN)ceramics have become exceptional materials for heat-resistant components in hypersonic vehicles,owing to their superior thermal stability and excellent dielectric properties.However,their densification during sintering still poses challenges for researchers,and their mechanical properties are rather unsatisfactory.In this study,SrAl_(2)Si_(2)O_(8)(SAS),with low melting point and high strength,was introduced into the h-BN ceramics to facilitate the sintering and reinforce the strength and toughness.Then,BN-SAS ceramic composites were fabricated via hot press sintering using h-BN,SrCO_(3),Al_(2)O_(3),and SiO_(2) as raw materials,and effects of sintering pressure on their microstructure,mechanical property,and thermal property were investigated.The thermal shock resistance of BN-SAS ceramic composites was evaluated.Results show that phases of as-preparedBN-SAS ceramic composites are h-BN and h-SrAl_(2)Si_(2)O_(8).With the increase of sintering pressure,the composites’densities increase,and the mechanical properties shew a rising trend followed by a slight decline.At a sintering pressure of 20 MPa,their bending strength and fracture toughness are(138±4)MPa and(1.84±0.05)MPa·m^(1/2),respectively.Composites sintered at 10 MPa exhibit a low coefficient of thermal expansion,with an average of 2.96×10^(-6) K^(-1) in the temperature range from 200 to 1200℃.The BN-SAS ceramic composites prepared at 20 MPa display higher thermal conductivity from 12.42 to 28.42 W·m^(-1)·K^(-1) within the temperature range from room temperature to 1000℃.Notably,BN-SAS composites exhibit remarkable thermal shock resistance,with residual bending strength peaking and subsequently declining sharply under a thermal shock temperature difference ranging from 600 to 1400℃.The maximum residual bending strength is recorded at a temperature difference of 800℃,with a residual strength retention rate of 101%.As the thermal shock temperature difference increase,the degree of oxidation on the ceramic surface and
