Micrometer-sized diamonds were incorporated into silicon nitride(Si_(3)N_(4))matrix to manufacture high-performance Si_(3)N_(4)-based composites using spark plasma sintering at 1500℃under 50 MPa.The effects of the di...Micrometer-sized diamonds were incorporated into silicon nitride(Si_(3)N_(4))matrix to manufacture high-performance Si_(3)N_(4)-based composites using spark plasma sintering at 1500℃under 50 MPa.The effects of the diamond content on the phase composition,microstructure,mechanical properties and thermal conductivity of the composites were investigated.The results showed that the addition of diamond could effectively improve the hardness of the material.The thermal conductivity of Si_(3)N_(4)increased to 52.97 W/m·k at the maximum with the addition of 15 wt%diamond,which was 27.5%higher than that of the monolithic Si_(3)N_(4).At this point,the fracture toughness was 7.54 MPa·m^(1/2).Due to the addition of diamond,the composite material generated a new substance,MgSiN2,which effectively combined Si_(3)N_(4)with diamond.MgSiN2 might improve the hardness and thermal conductivity of the materials.展开更多
A kind of n-type HoF_3-doped zinc oxide-based transparent conductive film has been developed by electron beam evaporation and studied under thermal annealing in air and vacuum at temperatures 100–500℃.Effective subs...A kind of n-type HoF_3-doped zinc oxide-based transparent conductive film has been developed by electron beam evaporation and studied under thermal annealing in air and vacuum at temperatures 100–500℃.Effective substitutional dopings of F to O and Ho to Zn are realized for the films with smooth surface morphology and average grain size of about 50 nm.The hall mobility,electron concentration,resistivity and work function for the asdeposited films are 47.89 cm^2/Vs,1.39×10^(20)cm^(-3),9.37×10^(-4)Ω·cm and 5.069 eV,respectively.In addition,the average transmittance in the visible region(400–700 nm)approximates to 87%.The HoF_3:ZnO films annealed in air and vacuum can retain good optoelectronic properties under 300℃,thereinto,more stable electrical properties can be found in the air-annealed films than in the vacuum-annealed films,which is assumed to be a result of improved nano-crystalline lattice quality.The optimized films for most parameters can be obtained at 200℃ for the air-annealing case and at room temperature for the vacuum annealing case.The advisable optoelectronic properties imply that HoF_3:ZnO can facilitate carrier injection and has promising applications in energy and light sources as transparent electrodes.展开更多
In the field of roads,due to the effect of vehicle loads,piezoelectric materials under the road surface can convert mechanical vibration into electrical energy,which can be further used in road facilities such as traf...In the field of roads,due to the effect of vehicle loads,piezoelectric materials under the road surface can convert mechanical vibration into electrical energy,which can be further used in road facilities such as traffic signals and street lamps.The barium titanate/polyvinylidene fluoride(BaTiO_(3)/PVDF)composite,the most common hybrid ceramic-polymer system,was widely used in various fields because the composite combines the good dielectric property of ceramic materials with the good flexibility of PVDF material.Previous studies have found that conductive particles can further improve the dielectric and piezoelectric properties of other composites.However,few studies have investigated the effect of conductive carbon black on the dielectric and piezoelectric properties of BaTiO_(3)/PVDF composites.In this study,BaTiO_(3)/PVDF/conductive carbon black composites were prepared with various conductive carbon black contents based on the optimum ratio of BaTiO_(3)to PVDF.The effects of conductive carbon black content on the morphologies,thermal performance,conductivities,dielectric properties,and piezoelectric properties of the BaTiO_(3)/PVDF/conductive carbon black composites were then investigated.The addition of conductive carbon black greatly enhances the conductivities,dielectric properties,and piezoelectric properties of the BaTiO_(3)/PVDF/conductive carbon black composites,especially when the carbon black content is 0.8%by weight of PVDF.Additionally,the conductive carbon black does not have an obvious effect on the morphologies and thermal stabilities of BaTiO_(3)/PVDF/conductive carbon black composites.展开更多
Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) incorporated with nanocrystalline TiO2 powder (PEDOT:PSS+nc-TiO2) films were prepared by spin-coating technique. SEM surface morphology, UV-Vis spectra and NH3 g...Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) incorporated with nanocrystalline TiO2 powder (PEDOT:PSS+nc-TiO2) films were prepared by spin-coating technique. SEM surface morphology, UV-Vis spectra and NH3 gas sensing of were studied. Results showed that the PEDOT:PSS+nc-TiO2 film with a content of 9.0 wt% of TiO2 is most suitable for both the hole transport layer and the NH3 sensing. The responding time of the sensor made from this composite film reached a value as fast as 20 s. The rapid responsiveness to NH3 gas was attributed to the efficient movement of holes as the major charge carriers in PEDOT:PSS+nc-TiO2 composite films. Useful applications in organic electronic devices like light emitting diodes and gas thin film sensors can be envisaged.展开更多
The present work is concerned with determining the viscosity,diffusion,thermal diffusion factor and thermal conductivity of five equimolar binary gas mixtures including:CF4-He,CF4-Ne,CF4-Ar,CF4-Kr,CF4-Xe from the prin...The present work is concerned with determining the viscosity,diffusion,thermal diffusion factor and thermal conductivity of five equimolar binary gas mixtures including:CF4-He,CF4-Ne,CF4-Ar,CF4-Kr,CF4-Xe from the principle of corresponding states of viscosity by the inversion technique.The Lennard-Jones (12-6) model potential is used as the initial model potential.The calculated interaction potential energies obtained from the inversion procedure is employed to reproduce the viscosities,diffusions,thermal diffusion factors,and thermal conductivities.The accuracies of the calculated viscosity and diffusion coefficients were 1% and 4%,respectively.展开更多
In our previous work,we calculated transport properties of pure gaseous polyatomic carbon tetrafluoride(CF4) and five equimolar binary gas mixtures of CF4 with noble gases through inversion technique.The present work ...In our previous work,we calculated transport properties of pure gaseous polyatomic carbon tetrafluoride(CF4) and five equimolar binary gas mixtures of CF4 with noble gases through inversion technique.The present work is a continuation of our studies on determining the transport properties of binary gas mixtures CF4 with some gases including three diatomic molecules CO,N2,and O2,a linear polyatomic CO2,and two non-linear polyatomic molecules SF6 and CH4.The Chapman-Enskog and Vesovic-Wakeham methods as well as inversion procedure are used to determine the viscosities,diffusivities,and thermal conductivities,which deviates from the literature values within 1%,4%,and 5%,respectively.展开更多
Increasing the phonon scattering center by adding nanoparticles to thermoelectric materials is an effective method of regulating the thermal conductivity.In this study,a series of Ca3 Co_(4)O_(9)/x wt.%CNTs(x=0,3,5,7,...Increasing the phonon scattering center by adding nanoparticles to thermoelectric materials is an effective method of regulating the thermal conductivity.In this study,a series of Ca3 Co_(4)O_(9)/x wt.%CNTs(x=0,3,5,7,10)polycrystalline ceramic thermoelectric materials by adding carbon nanotubes(CNTs)were prepared with sol-gel method and cold-pressing sintering technology.The results of x-ray diffraction and field emission scanning electron microscopy show that the materials have a single-phase structure with high orientation and sheet like microstructure.The effect of adding carbon nanotubes to the thermoelectric properties of Ca_(3)Co_(4)O_(9)was systematically measured.The test results of thermoelectric properties show that the addition of carbon nanotubes reduces the electrical conductivity and Seebeck coefficient of the material.Nevertheless,the thermal conductivity of the samples with carbon nanotubes addition is lower than that of the samples without carbon nanotubes.At 625 K,the thermal conductivity of Ca3 Co_(4)O_(9)/10 wt.%CNTs sample is reduced to0.408 W·m^(-1)·K^(-1),which is about 73%lower than that of the original sample.When the three parameters are coupled,the figure of merit of Ca_(3)Co_(4)O_(9)/3 wt.%CNTs sample reaches 0.052,which is 29%higher than that of the original sample.This shows that an appropriate amount of carbon nanotubes addition can reduce the thermal conductivity of Ca_(3)Co_(4)O_(9)ceramic samples and improve their thermoelectric properties.展开更多
High strength SiC whisker-reinforced Ti3SiC2 composites(SiCw/Ti3SiC2)with an improved thermal conductivity and mechanical properties were fabricated by spark plasma sintering.The bending strength of 10 wt%SiCw/Ti3SiC2...High strength SiC whisker-reinforced Ti3SiC2 composites(SiCw/Ti3SiC2)with an improved thermal conductivity and mechanical properties were fabricated by spark plasma sintering.The bending strength of 10 wt%SiCw/Ti3SiC2 was 635 MPa,which was approximately 50%higher than that of the monolithic Ti3SiC2(428 MPa).The Vickers hardness and thermal conductivity(k)also increased by 36%and 25%,respectively,from the monolithic Ti3SiC2 by the incorporation of 10 wt%SiCw.This remarkable improvement both in mechanical and thermal properties was attributed to the fine-grained uniform composite microstructure along with the effects of incorporated SiCw.The SiCw/Ti3SiC2 can be a feasible candidate for the in-core structural application in nuclear reactors due to the excellent mechanical and thermal properties.展开更多
The thermal phonon transport is a key matter for heat managing in materials science which is crucial for device miniaturization and power density increase. Herein, we report the synthesis, structure and characterizati...The thermal phonon transport is a key matter for heat managing in materials science which is crucial for device miniaturization and power density increase. Herein, we report the synthesis, structure and characterization of a new compound, Cs2Ge3Ga6Se14, with a unique anisotropic structure simultaneously containing Ge^3+ and Ge^2+ that adopt(Ge1)2^3+ Se6 dimer or(Ge2)^2+Se6 octahedron, respectively. The thermal conductivity was measured to be 0.57–0.48 W m^-1 K^-1 from 323 to 773 K, the lowest value among all the known Ge-containing compounds, approaching its glass limit according to the Cahill’s formulation. More importantly, we discover for the first time that the vibration uncoupling of Ge with different valence states hinders the effective thermal energy transport between the(Ge1)2^3+ Se6 dimer and(Ge2)^2+Se6 octahedron, and consequently lowers the thermal conductivity. In addition, we propose a structure factor f = sin(180) ×d/l(i =A, B)iGe Qi, with which a structure map of the Cs2 Ge3 M6 Q14 family is given.展开更多
Two new correlations of thermal conductivity and viscosity correlation of R134a areproposed in this paper. These correlations have been tested and the test results show thatthese correlations have high accuracy and wi...Two new correlations of thermal conductivity and viscosity correlation of R134a areproposed in this paper. These correlations have been tested and the test results show thatthese correlations have high accuracy and wide application range.展开更多
Based on the study of a new type of conducting polymer poly （3,4-ethylenedioxythiophene） （PEDOT）,we focussed on the preparation and characteristics of PEDOT nanoparticles made by reversed micelle method.Moreover,w...Based on the study of a new type of conducting polymer poly （3,4-ethylenedioxythiophene） （PEDOT）,we focussed on the preparation and characteristics of PEDOT nanoparticles made by reversed micelle method.Moreover,we deeply investigated the optical,electrical and the thermal stability of PEDOT nanoparticles.The main results are as follows： the small-sized PEDOT nanoparticles were prepared and utilized by different methods,such as ultraviolet/visible （UV-Vis） spectroscopy,Fourier-transform infrared （FT- IR） spectrum,scanning electron microscopy（SEM） and so on.The results show that the amount of oxidizer,ultrasonic treatment,polymerizing temperature and doping degree can influent morphology,electrical ability and gas sensitivity of PEDOT nanoparticles.The Bragg peaks of nanoparticles at 6.7°,12.7°,25° were observed by XRD and the better orientation of molecular chain was attributed to the effective doping of toluene-p-sulfonic acid,which also resulted in an enhancement of thermal stability of nanoparticles than conventional PEDOT.展开更多
基金Funded by the Key Research and Development Plan of Jiangxi Province(No.2020ZDYFB0017)the National Key Research and Development Plan(No.2021YFB3701400)the National Natural Science Foundation of China((No.92163208)。
文摘Micrometer-sized diamonds were incorporated into silicon nitride(Si_(3)N_(4))matrix to manufacture high-performance Si_(3)N_(4)-based composites using spark plasma sintering at 1500℃under 50 MPa.The effects of the diamond content on the phase composition,microstructure,mechanical properties and thermal conductivity of the composites were investigated.The results showed that the addition of diamond could effectively improve the hardness of the material.The thermal conductivity of Si_(3)N_(4)increased to 52.97 W/m·k at the maximum with the addition of 15 wt%diamond,which was 27.5%higher than that of the monolithic Si_(3)N_(4).At this point,the fracture toughness was 7.54 MPa·m^(1/2).Due to the addition of diamond,the composite material generated a new substance,MgSiN2,which effectively combined Si_(3)N_(4)with diamond.MgSiN2 might improve the hardness and thermal conductivity of the materials.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61774154 and 51503196
文摘A kind of n-type HoF_3-doped zinc oxide-based transparent conductive film has been developed by electron beam evaporation and studied under thermal annealing in air and vacuum at temperatures 100–500℃.Effective substitutional dopings of F to O and Ho to Zn are realized for the films with smooth surface morphology and average grain size of about 50 nm.The hall mobility,electron concentration,resistivity and work function for the asdeposited films are 47.89 cm^2/Vs,1.39×10^(20)cm^(-3),9.37×10^(-4)Ω·cm and 5.069 eV,respectively.In addition,the average transmittance in the visible region(400–700 nm)approximates to 87%.The HoF_3:ZnO films annealed in air and vacuum can retain good optoelectronic properties under 300℃,thereinto,more stable electrical properties can be found in the air-annealed films than in the vacuum-annealed films,which is assumed to be a result of improved nano-crystalline lattice quality.The optimized films for most parameters can be obtained at 200℃ for the air-annealing case and at room temperature for the vacuum annealing case.The advisable optoelectronic properties imply that HoF_3:ZnO can facilitate carrier injection and has promising applications in energy and light sources as transparent electrodes.
基金We are grateful for the financial supported by the National Natural Science Foundation of China(Grant No.52178408)the National Key R&D Program of China(Grant No.2018YFE0103800).
文摘In the field of roads,due to the effect of vehicle loads,piezoelectric materials under the road surface can convert mechanical vibration into electrical energy,which can be further used in road facilities such as traffic signals and street lamps.The barium titanate/polyvinylidene fluoride(BaTiO_(3)/PVDF)composite,the most common hybrid ceramic-polymer system,was widely used in various fields because the composite combines the good dielectric property of ceramic materials with the good flexibility of PVDF material.Previous studies have found that conductive particles can further improve the dielectric and piezoelectric properties of other composites.However,few studies have investigated the effect of conductive carbon black on the dielectric and piezoelectric properties of BaTiO_(3)/PVDF composites.In this study,BaTiO_(3)/PVDF/conductive carbon black composites were prepared with various conductive carbon black contents based on the optimum ratio of BaTiO_(3)to PVDF.The effects of conductive carbon black content on the morphologies,thermal performance,conductivities,dielectric properties,and piezoelectric properties of the BaTiO_(3)/PVDF/conductive carbon black composites were then investigated.The addition of conductive carbon black greatly enhances the conductivities,dielectric properties,and piezoelectric properties of the BaTiO_(3)/PVDF/conductive carbon black composites,especially when the carbon black content is 0.8%by weight of PVDF.Additionally,the conductive carbon black does not have an obvious effect on the morphologies and thermal stabilities of BaTiO_(3)/PVDF/conductive carbon black composites.
文摘Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) incorporated with nanocrystalline TiO2 powder (PEDOT:PSS+nc-TiO2) films were prepared by spin-coating technique. SEM surface morphology, UV-Vis spectra and NH3 gas sensing of were studied. Results showed that the PEDOT:PSS+nc-TiO2 film with a content of 9.0 wt% of TiO2 is most suitable for both the hole transport layer and the NH3 sensing. The responding time of the sensor made from this composite film reached a value as fast as 20 s. The rapid responsiveness to NH3 gas was attributed to the efficient movement of holes as the major charge carriers in PEDOT:PSS+nc-TiO2 composite films. Useful applications in organic electronic devices like light emitting diodes and gas thin film sensors can be envisaged.
基金Research Committees of Shiraz University and Shiraz University of Technology for supporting this project and making computer facilities available
文摘The present work is concerned with determining the viscosity,diffusion,thermal diffusion factor and thermal conductivity of five equimolar binary gas mixtures including:CF4-He,CF4-Ne,CF4-Ar,CF4-Kr,CF4-Xe from the principle of corresponding states of viscosity by the inversion technique.The Lennard-Jones (12-6) model potential is used as the initial model potential.The calculated interaction potential energies obtained from the inversion procedure is employed to reproduce the viscosities,diffusions,thermal diffusion factors,and thermal conductivities.The accuracies of the calculated viscosity and diffusion coefficients were 1% and 4%,respectively.
文摘In our previous work,we calculated transport properties of pure gaseous polyatomic carbon tetrafluoride(CF4) and five equimolar binary gas mixtures of CF4 with noble gases through inversion technique.The present work is a continuation of our studies on determining the transport properties of binary gas mixtures CF4 with some gases including three diatomic molecules CO,N2,and O2,a linear polyatomic CO2,and two non-linear polyatomic molecules SF6 and CH4.The Chapman-Enskog and Vesovic-Wakeham methods as well as inversion procedure are used to determine the viscosities,diffusivities,and thermal conductivities,which deviates from the literature values within 1%,4%,and 5%,respectively.
基金supported by the National Natural Science Foundation of China(Grant No.51836009)。
文摘Increasing the phonon scattering center by adding nanoparticles to thermoelectric materials is an effective method of regulating the thermal conductivity.In this study,a series of Ca3 Co_(4)O_(9)/x wt.%CNTs(x=0,3,5,7,10)polycrystalline ceramic thermoelectric materials by adding carbon nanotubes(CNTs)were prepared with sol-gel method and cold-pressing sintering technology.The results of x-ray diffraction and field emission scanning electron microscopy show that the materials have a single-phase structure with high orientation and sheet like microstructure.The effect of adding carbon nanotubes to the thermoelectric properties of Ca_(3)Co_(4)O_(9)was systematically measured.The test results of thermoelectric properties show that the addition of carbon nanotubes reduces the electrical conductivity and Seebeck coefficient of the material.Nevertheless,the thermal conductivity of the samples with carbon nanotubes addition is lower than that of the samples without carbon nanotubes.At 625 K,the thermal conductivity of Ca3 Co_(4)O_(9)/10 wt.%CNTs sample is reduced to0.408 W·m^(-1)·K^(-1),which is about 73%lower than that of the original sample.When the three parameters are coupled,the figure of merit of Ca_(3)Co_(4)O_(9)/3 wt.%CNTs sample reaches 0.052,which is 29%higher than that of the original sample.This shows that an appropriate amount of carbon nanotubes addition can reduce the thermal conductivity of Ca_(3)Co_(4)O_(9)ceramic samples and improve their thermoelectric properties.
基金This study was supported by the National Natural Science Foundation of China(Grant Nos.11975296 and 51811540402)the Natural Science Foundation of Ningbo City(Grant No.2018A610001)the Korea Ministry of Education(NRF-2018K2A9A2A06018203).
文摘High strength SiC whisker-reinforced Ti3SiC2 composites(SiCw/Ti3SiC2)with an improved thermal conductivity and mechanical properties were fabricated by spark plasma sintering.The bending strength of 10 wt%SiCw/Ti3SiC2 was 635 MPa,which was approximately 50%higher than that of the monolithic Ti3SiC2(428 MPa).The Vickers hardness and thermal conductivity(k)also increased by 36%and 25%,respectively,from the monolithic Ti3SiC2 by the incorporation of 10 wt%SiCw.This remarkable improvement both in mechanical and thermal properties was attributed to the fine-grained uniform composite microstructure along with the effects of incorporated SiCw.The SiCw/Ti3SiC2 can be a feasible candidate for the in-core structural application in nuclear reactors due to the excellent mechanical and thermal properties.
基金supported by the National Natural Science Foundation of China (21975032 and 21571020)the National Key Research and Development Program of China (2018YFA0702100)
文摘The thermal phonon transport is a key matter for heat managing in materials science which is crucial for device miniaturization and power density increase. Herein, we report the synthesis, structure and characterization of a new compound, Cs2Ge3Ga6Se14, with a unique anisotropic structure simultaneously containing Ge^3+ and Ge^2+ that adopt(Ge1)2^3+ Se6 dimer or(Ge2)^2+Se6 octahedron, respectively. The thermal conductivity was measured to be 0.57–0.48 W m^-1 K^-1 from 323 to 773 K, the lowest value among all the known Ge-containing compounds, approaching its glass limit according to the Cahill’s formulation. More importantly, we discover for the first time that the vibration uncoupling of Ge with different valence states hinders the effective thermal energy transport between the(Ge1)2^3+ Se6 dimer and(Ge2)^2+Se6 octahedron, and consequently lowers the thermal conductivity. In addition, we propose a structure factor f = sin(180) ×d/l(i =A, B)iGe Qi, with which a structure map of the Cs2 Ge3 M6 Q14 family is given.
文摘Two new correlations of thermal conductivity and viscosity correlation of R134a areproposed in this paper. These correlations have been tested and the test results show thatthese correlations have high accuracy and wide application range.
基金Funded by the National Natural Science Foundation of China (No. 60372002)
文摘Based on the study of a new type of conducting polymer poly （3,4-ethylenedioxythiophene） （PEDOT）,we focussed on the preparation and characteristics of PEDOT nanoparticles made by reversed micelle method.Moreover,we deeply investigated the optical,electrical and the thermal stability of PEDOT nanoparticles.The main results are as follows： the small-sized PEDOT nanoparticles were prepared and utilized by different methods,such as ultraviolet/visible （UV-Vis） spectroscopy,Fourier-transform infrared （FT- IR） spectrum,scanning electron microscopy（SEM） and so on.The results show that the amount of oxidizer,ultrasonic treatment,polymerizing temperature and doping degree can influent morphology,electrical ability and gas sensitivity of PEDOT nanoparticles.The Bragg peaks of nanoparticles at 6.7°,12.7°,25° were observed by XRD and the better orientation of molecular chain was attributed to the effective doping of toluene-p-sulfonic acid,which also resulted in an enhancement of thermal stability of nanoparticles than conventional PEDOT.
