Improving the thermal stability of diamond and other superhard materials has great significance in various applications. Here, we report the synthesis and characterization of bulk diamond–cBN–B4C–Si composites sint...Improving the thermal stability of diamond and other superhard materials has great significance in various applications. Here, we report the synthesis and characterization of bulk diamond–cBN–B4C–Si composites sintered at high pressure and high temperature(HPHT, 5.2 GPa, 1620–1680 K for 3–5 min). The results show that the diamond, cBN, B4C,BxSiC, SiO2 and amorphous carbon or a little surplus Si are present in the sintered samples. The onset oxidation temperature of 1673 K in the as-synthesized sample is much higher than that of diamond, cBN, and B4C. The high thermal stability is ascribed to the covalent bonds of B–C, C–N, and the solid-solution of BxSiC formed during the sintering process. The results obtained in this work may be useful in preparing superhard materials with high thermal stability.展开更多
Developing new functional explosives that display high stability,good energy performance,and low sensitivity are one of the key directions of energetic materials research.In this work,two-dimensional(2D)Schiff-based e...Developing new functional explosives that display high stability,good energy performance,and low sensitivity are one of the key directions of energetic materials research.In this work,two-dimensional(2D)Schiff-based energetic covalent organic frameworks(COFs)are prepared based on triaminoguanidine salts with different anions as building blocks.Benefiting from the robust covalent bond in 2D extended polygons and strongπ-πinteractions in the eclipsed interlayers,the synthesized energetic COFs showed higher thermal stability and lower mechanical sensitivity than their precursor salts.More importantly,incorporating triaminoguanidine salts into COFs effectively increase the corrosion resistance to metal under high humidity conditions,which is due to the imine moieties in COFs functioning asπacceptors and offering strong bonding with metallic ions.This work provides a new pathway for the development of high-performance energetic materials.展开更多
Composite ceramic phosphor(CCP)is a candidate light-conversion material to obtain the high-quality laser lighting source.Phosphors based on the transmissive configuration model could not simultaneously meet the requir...Composite ceramic phosphor(CCP)is a candidate light-conversion material to obtain the high-quality laser lighting source.Phosphors based on the transmissive configuration model could not simultaneously meet the requirements of angular color uniformity and high thermal stability.In this study,a novel composite structure ceramic was designed,including Al_(2)O_(3)-YAG:Ce/YAG layered ceramic with a size of 1 mm×1 mm for lighting,and Al_(2)O_(3) ceramic(φ=16.0 mm)was used as the wrapping material due to its outstanding thermal stability.The prepared ceramics exhibited excellent thermal performance and no yellow ring phenomenon.Through this design,we achieved the match of the intensity distribution of the blue and yellow lights,resulting in a high angular color uniformity of 0.9 with a view angle of±80°.All ceramics showed no luminous saturation phenomenon,even the laser power density was increased up to 47.51 W/mm^(2).A high-brightness white-light source with a luminous flux of 618 lm,a luminous efficiency of 126 lm/W,a CCT of 6615 K,and a CRI of 69.9 was obtained in the transmissive configuration.In particular,the surface temperature of the ceramic was as low as 74.1℃ under a high laser radiation(47.51 W/mm^(2)).These results indicate that Al_(2)O_(3)/Al_(2)O_(3)-YAG:Ce/YAG composite structure ceramic is a promising luminescent material in the high-power laser lighting applications.展开更多
Herein,double-perovskite Ba_(2)LaTaO_(6) Eu-doped orange-red phosphors were successfully synthesized using a high-temperature solid-phase method.The phosphor phase purity was investigated using X-ray diffraction and m...Herein,double-perovskite Ba_(2)LaTaO_(6) Eu-doped orange-red phosphors were successfully synthesized using a high-temperature solid-phase method.The phosphor phase purity was investigated using X-ray diffraction and microscopic morphology analyses.Their luminescence properties were investigated using absorption,emission,excitation,and temperature-dependent spectra.The transition mechanism mainly involves a magnetic-dipole transition with an energy transfer mode featuring multipole-multipole interactions,and concentration quenching is achieved via dipole-dipole interactions.In addition,the intensity of the temperature-dependent spectrum increases abnormally between 298 and 373 K,with the luminous intensity at 373 K increasing to 110%of that observed at room temperature.This phenomenon can be attributed to lattice defects in Ba_(2)LaTaO_(6):Eu^(3+),and the phosphor luminous intensity at473 K remains at 80.62%of that at room temperature.In addition,white-light-emitting diode devices based on this novel Ba_(2)LaTaO_(6):0.35Eu^(3+)phosphor were fabricated to evaluate the potential applications of the as-prepared phosphor.展开更多
Polycrystalline diamond compacts(PDC), which are composed of diamond and WC/Co substrate, and synthesized at high pressure and high temperature(HPHT), are widely applied as the tooth of drilling bit. However, the ...Polycrystalline diamond compacts(PDC), which are composed of diamond and WC/Co substrate, and synthesized at high pressure and high temperature(HPHT), are widely applied as the tooth of drilling bit. However, the thermal stability of PDC will be reduced when diamond transforms into graphite due to cobalt in PDC acting as a catalyst during the drilling work. In this study, a new three-layer structured PDC with enhanced thermal stability has been successfully synthesized at pressures of 5.5–7.0 GPa and temperatures of 1650–1750?C. In this structure, the diamond-Si C composite acts as the working layer,and the diamond-Si C-Co composite and WC/Co cements are as the intermediate layer and substrate,respectively. It is found that the initial oxidizing temperature of the three-layered PDC is enhanced up to820?C, which is significantly higher than that(~780?C) of the conventional PDC counterpart.展开更多
A hot cathode bucket ion source is used for the EAST(experimental advanced superconducting tokamak)neutral beam injector.The thermal electrons emitted from the surface of the cathode are extracted and accelerated by...A hot cathode bucket ion source is used for the EAST(experimental advanced superconducting tokamak)neutral beam injector.The thermal electrons emitted from the surface of the cathode are extracted and accelerated by the electric field formed by the arc voltage,which is applied between the arc chamber of the ion source and the cathode.This paper analyzes the effects of arc voltage on the arc discharge in a hot cathode high current ion source.展开更多
The eutectic CoFeNi2V0.5Nb0.75 high entropy alloys (HEAs) were heated at 500, 600, 700, 800 and 1000 ℃, respectively for 6 h and subsequently quenched in the water to investigate their thermal stability and phase t...The eutectic CoFeNi2V0.5Nb0.75 high entropy alloys (HEAs) were heated at 500, 600, 700, 800 and 1000 ℃, respectively for 6 h and subsequently quenched in the water to investigate their thermal stability and phase transformation at high temperature. The microstructure and mechanical properties of the samples were investigated by scanning electron microscopy, X-ray diffraction, compressive and hardness tests. It was found that the as-cast CoFeNi2V0.5Nb0.75 HEAs showed a eutectic microstructure with alternating fcc solid solution phase and Fe2Nb-type Laves phase. The NbNi4-type intermetallic phase appeared when the heat-treated temperature was higher than 600 ℃. With increasing quenching temperature, the volume fraction of the NbNi4-type intermetallic phase increased while that of the eutectic regions decreased. The sample quenched at 800 ℃ showed the most excellent comprehensive mechanical properties; its fracture strength, yield strength and plastic strain were as high as 2586.76 MPa, 2075.18 MPa and 16.73%, respectively. Moreover, the eutectic CoFeNi2V0.5Nb0.75 HEAs exhibited apparent age hardening, especially quenched at 700 ℃, the hardness reached up to the maximum value of HV 727.52.展开更多
A polymer (poly(9,10)anthracenevinylene-alt-4,4'-(9,9-bis(4-(4'-(1,2,2'-triphenyviny)phenoxy)butyl)-9H- fluorene-2,7-diyl) dibenzaldehyde), P1) was successfully synthesized through the Wittig-Horner re...A polymer (poly(9,10)anthracenevinylene-alt-4,4'-(9,9-bis(4-(4'-(1,2,2'-triphenyviny)phenoxy)butyl)-9H- fluorene-2,7-diyl) dibenzaldehyde), P1) was successfully synthesized through the Wittig-Horner reaction by employing fluorene and 9,10-distyrylanthracene moieties as building blocks for backbone and tetraphenylethenes as pendant groups. Photophysical and thermal properties of the resulting polymeric emitter were fully characterized by ultraviolet-visible (UV- Vis) absorption and photoluminescence (PL) spectra, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). While P1 emits an orange-light centered at 567 nm in dilute tetrahydrofuran (THF) solution, the solid powder of the polymer exhibits strong yellow emission peaked at 541 nm. It is also found that the as-synthesized polymer shows unique property of aggregation-enhanced emission (AEE). In addition, P1 possesses high thermal stability with a decomposition temperature (Td,5%) of 430 ℃ and high morphological stability with a glass transition temperature (Tg) of 171℃. Under the stimulus of mechanical force, the emission of P1 can be changed from yellow to red (△λmax = 61 rim), showing a remarkable mechanochromism. The results from XRD analysis suggest that such mechanochromic phenomenonof PI is probably caused by the destruction of crystalline structure, which leads to the conformational planarization of the distyrylanthracene moieties forming by the polymerization and the increase of molecular conjugation of the backbone.展开更多
Photosensitive polyimide precursor containing glycol monocinnamate group was synthesized by a new method. The photoresist, made from the above polyimide precursor, was spin coated onto silicon wafers, prebaked...Photosensitive polyimide precursor containing glycol monocinnamate group was synthesized by a new method. The photoresist, made from the above polyimide precursor, was spin coated onto silicon wafers, prebaked and then exposed to UV light. The appropriate conditions of the photolithographic procedures were determined. This photosensitive polyimide precursor showed good light sensitivity and the polyimide which was obtained by heating the polyimide precursor had a high thermal stability.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51301075)the Project of Development and Reform Commission of Jilin Province,China(Grant No.2014Y136)
文摘Improving the thermal stability of diamond and other superhard materials has great significance in various applications. Here, we report the synthesis and characterization of bulk diamond–cBN–B4C–Si composites sintered at high pressure and high temperature(HPHT, 5.2 GPa, 1620–1680 K for 3–5 min). The results show that the diamond, cBN, B4C,BxSiC, SiO2 and amorphous carbon or a little surplus Si are present in the sintered samples. The onset oxidation temperature of 1673 K in the as-synthesized sample is much higher than that of diamond, cBN, and B4C. The high thermal stability is ascribed to the covalent bonds of B–C, C–N, and the solid-solution of BxSiC formed during the sintering process. The results obtained in this work may be useful in preparing superhard materials with high thermal stability.
基金supported the National Natural Science Foundation of China(Nos.22175155,21825106 and 22275168)the Henan Science Fund for Excellent Young Scholars(No.212300410084)the opening project of State Key Laboratory of Explosion Science and Technology(Beijing Institute of Technology)(No.KFJJ22–05 M)。
文摘Developing new functional explosives that display high stability,good energy performance,and low sensitivity are one of the key directions of energetic materials research.In this work,two-dimensional(2D)Schiff-based energetic covalent organic frameworks(COFs)are prepared based on triaminoguanidine salts with different anions as building blocks.Benefiting from the robust covalent bond in 2D extended polygons and strongπ-πinteractions in the eclipsed interlayers,the synthesized energetic COFs showed higher thermal stability and lower mechanical sensitivity than their precursor salts.More importantly,incorporating triaminoguanidine salts into COFs effectively increase the corrosion resistance to metal under high humidity conditions,which is due to the imine moieties in COFs functioning asπacceptors and offering strong bonding with metallic ions.This work provides a new pathway for the development of high-performance energetic materials.
基金the National Key R&D Program of China(2021YFB3501700,2023YFB3506600)National Natural Science Foundation of China(52202135,61975070,and 52302141)+5 种基金Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),International S&T Cooperation Program of Jiangsu Province(BZ2023007)Key Research and Development Project of Jiangsu Province(BE2023050,BE2021040)Natural Science foundation of Jiangsu Province(BK20221226)Graduate Research and Innovation Projects of Jiangsu Province(KYCX22_2845)Special Project for Technology Innovation of Xuzhou City(KC23380,KC21379,KC22461,and KC22497)Open Project of State Key Laboratory of Crystal Materials(KF2205).
文摘Composite ceramic phosphor(CCP)is a candidate light-conversion material to obtain the high-quality laser lighting source.Phosphors based on the transmissive configuration model could not simultaneously meet the requirements of angular color uniformity and high thermal stability.In this study,a novel composite structure ceramic was designed,including Al_(2)O_(3)-YAG:Ce/YAG layered ceramic with a size of 1 mm×1 mm for lighting,and Al_(2)O_(3) ceramic(φ=16.0 mm)was used as the wrapping material due to its outstanding thermal stability.The prepared ceramics exhibited excellent thermal performance and no yellow ring phenomenon.Through this design,we achieved the match of the intensity distribution of the blue and yellow lights,resulting in a high angular color uniformity of 0.9 with a view angle of±80°.All ceramics showed no luminous saturation phenomenon,even the laser power density was increased up to 47.51 W/mm^(2).A high-brightness white-light source with a luminous flux of 618 lm,a luminous efficiency of 126 lm/W,a CCT of 6615 K,and a CRI of 69.9 was obtained in the transmissive configuration.In particular,the surface temperature of the ceramic was as low as 74.1℃ under a high laser radiation(47.51 W/mm^(2)).These results indicate that Al_(2)O_(3)/Al_(2)O_(3)-YAG:Ce/YAG composite structure ceramic is a promising luminescent material in the high-power laser lighting applications.
基金Project supported by the National Natural Science Foundation of China (52262020)the Science and Technology Foundation of Guizhou Province (ZK[2021]yiban 328)。
文摘Herein,double-perovskite Ba_(2)LaTaO_(6) Eu-doped orange-red phosphors were successfully synthesized using a high-temperature solid-phase method.The phosphor phase purity was investigated using X-ray diffraction and microscopic morphology analyses.Their luminescence properties were investigated using absorption,emission,excitation,and temperature-dependent spectra.The transition mechanism mainly involves a magnetic-dipole transition with an energy transfer mode featuring multipole-multipole interactions,and concentration quenching is achieved via dipole-dipole interactions.In addition,the intensity of the temperature-dependent spectrum increases abnormally between 298 and 373 K,with the luminous intensity at 373 K increasing to 110%of that observed at room temperature.This phenomenon can be attributed to lattice defects in Ba_(2)LaTaO_(6):Eu^(3+),and the phosphor luminous intensity at473 K remains at 80.62%of that at room temperature.In addition,white-light-emitting diode devices based on this novel Ba_(2)LaTaO_(6):0.35Eu^(3+)phosphor were fabricated to evaluate the potential applications of the as-prepared phosphor.
基金financial supports from the National Natural Science Foundation of China (No. 41572357)
文摘Polycrystalline diamond compacts(PDC), which are composed of diamond and WC/Co substrate, and synthesized at high pressure and high temperature(HPHT), are widely applied as the tooth of drilling bit. However, the thermal stability of PDC will be reduced when diamond transforms into graphite due to cobalt in PDC acting as a catalyst during the drilling work. In this study, a new three-layer structured PDC with enhanced thermal stability has been successfully synthesized at pressures of 5.5–7.0 GPa and temperatures of 1650–1750?C. In this structure, the diamond-Si C composite acts as the working layer,and the diamond-Si C-Co composite and WC/Co cements are as the intermediate layer and substrate,respectively. It is found that the initial oxidizing temperature of the three-layered PDC is enhanced up to820?C, which is significantly higher than that(~780?C) of the conventional PDC counterpart.
基金supported by the National Magnetic Confinement Fusion Science Program of China(No.2013GB101000)National Natural Science Foundation of China(No.11405207)
文摘A hot cathode bucket ion source is used for the EAST(experimental advanced superconducting tokamak)neutral beam injector.The thermal electrons emitted from the surface of the cathode are extracted and accelerated by the electric field formed by the arc voltage,which is applied between the arc chamber of the ion source and the cathode.This paper analyzes the effects of arc voltage on the arc discharge in a hot cathode high current ion source.
基金supported by the National Natural Science Foundation of China (Nos. 51104029, 51134013, 51471044, 51104029 and 51375070)the Fundamental Research Funds for the Central Universitiesthe Natural Science Foundation of Liaoning Province (No. 2014028013)
文摘The eutectic CoFeNi2V0.5Nb0.75 high entropy alloys (HEAs) were heated at 500, 600, 700, 800 and 1000 ℃, respectively for 6 h and subsequently quenched in the water to investigate their thermal stability and phase transformation at high temperature. The microstructure and mechanical properties of the samples were investigated by scanning electron microscopy, X-ray diffraction, compressive and hardness tests. It was found that the as-cast CoFeNi2V0.5Nb0.75 HEAs showed a eutectic microstructure with alternating fcc solid solution phase and Fe2Nb-type Laves phase. The NbNi4-type intermetallic phase appeared when the heat-treated temperature was higher than 600 ℃. With increasing quenching temperature, the volume fraction of the NbNi4-type intermetallic phase increased while that of the eutectic regions decreased. The sample quenched at 800 ℃ showed the most excellent comprehensive mechanical properties; its fracture strength, yield strength and plastic strain were as high as 2586.76 MPa, 2075.18 MPa and 16.73%, respectively. Moreover, the eutectic CoFeNi2V0.5Nb0.75 HEAs exhibited apparent age hardening, especially quenched at 700 ℃, the hardness reached up to the maximum value of HV 727.52.
基金financially supported by the National Natural Science Foundation of China(Nos.51473185,51603233 and 21672267)863 Program(No.SS2015AA031701)+1 种基金the Fundamental Research Funds for the Central UniversitiesGuangdong Science and Technology Plan(Nos.2015B090913003 and 2015B090915003)
文摘A polymer (poly(9,10)anthracenevinylene-alt-4,4'-(9,9-bis(4-(4'-(1,2,2'-triphenyviny)phenoxy)butyl)-9H- fluorene-2,7-diyl) dibenzaldehyde), P1) was successfully synthesized through the Wittig-Horner reaction by employing fluorene and 9,10-distyrylanthracene moieties as building blocks for backbone and tetraphenylethenes as pendant groups. Photophysical and thermal properties of the resulting polymeric emitter were fully characterized by ultraviolet-visible (UV- Vis) absorption and photoluminescence (PL) spectra, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). While P1 emits an orange-light centered at 567 nm in dilute tetrahydrofuran (THF) solution, the solid powder of the polymer exhibits strong yellow emission peaked at 541 nm. It is also found that the as-synthesized polymer shows unique property of aggregation-enhanced emission (AEE). In addition, P1 possesses high thermal stability with a decomposition temperature (Td,5%) of 430 ℃ and high morphological stability with a glass transition temperature (Tg) of 171℃. Under the stimulus of mechanical force, the emission of P1 can be changed from yellow to red (△λmax = 61 rim), showing a remarkable mechanochromism. The results from XRD analysis suggest that such mechanochromic phenomenonof PI is probably caused by the destruction of crystalline structure, which leads to the conformational planarization of the distyrylanthracene moieties forming by the polymerization and the increase of molecular conjugation of the backbone.
文摘Photosensitive polyimide precursor containing glycol monocinnamate group was synthesized by a new method. The photoresist, made from the above polyimide precursor, was spin coated onto silicon wafers, prebaked and then exposed to UV light. The appropriate conditions of the photolithographic procedures were determined. This photosensitive polyimide precursor showed good light sensitivity and the polyimide which was obtained by heating the polyimide precursor had a high thermal stability.