The results of experimental investigation of n-type semiconductor based on Bi2Te3 alloy were presented. This material is used in manufacture of thermoelectric coolers and electrical power generation devices. BizTe2.88...The results of experimental investigation of n-type semiconductor based on Bi2Te3 alloy were presented. This material is used in manufacture of thermoelectric coolers and electrical power generation devices. BizTe2.88Se0.12 solid solution single crystal has been grown using the Czochralski method. Monitoring of structure changes of the sample was carried out by electron microscope. The elemental composition of the studied alloy was obtained by energy dispersive spectrometry （EDS） analysis and empirical formula of the compound was established. X-ray diffraction analysis confirmed that the Bi2Te2.88Se0.12 sample was a single phase with rhombohedral structure. The behavior upon heating was studied using differential thermal analysis （DTA） technique. Changes in physical and chemical properties of materials were measured as a function of increasing temperature by thermogravimetric analysis （TGA）. The lattice parameters values obtained by X-ray powder diffraction analyses of Bi2Te2.88Se0.12 are very similar to BizTe3 lattice constants, indicating that a small portion of tellurium is replaced with selenium. The obtained values for specific electrical and thermal conductivities are in correlation with available literature data. The Vickers microhardness values are in range between HV 187 and HV 39.02 and decrease with load increasing. It is shown that very complex process of infrared thermography can be applied for characterization of thermoelectric elements and modules.展开更多
A two-dimensional model for freezing and thawing phase change heat transfer in biological tissue embedded with two cryoprobes was established.In this model,the blood vessels were considered as tree-like branched fract...A two-dimensional model for freezing and thawing phase change heat transfer in biological tissue embedded with two cryoprobes was established.In this model,the blood vessels were considered as tree-like branched fractal network,and the effective flow rate and effective thermal conductivity of blood were obtained by fractal method.The temperature distribution and ice crystal growth process in biological tissue embedded with two cryoprobes during freezing-thawing process were numerically simulated.The results show that the growth velocity of ice crystal in freezing process from 200 to 400 s is more rapid than that from 400 to 600 s. Thawing process of frozen tissue occurs in the regions around cryoprobes tips and tissue boundary simultaneously,and the phase interfaces are close to each other until ice crystal melts completely.The distance of two cryoprobes has a more profound effect on the temperature distribution in freezing process at 400 s than at 800 s.展开更多
Ultralong phosphorescent materials have numerous applications across biological imaging, lightemitting devices, X-ray detection and anti-counterfeiting. Triplet-state molecular phosphorescence typically accompanies th...Ultralong phosphorescent materials have numerous applications across biological imaging, lightemitting devices, X-ray detection and anti-counterfeiting. Triplet-state molecular phosphorescence typically accompanies the singlet-state fluorescence during photoluminescence, and it is still difficult to achieve direct triplet photoemission as ultralong room temperature phosphorescence(RTP). Here, we have designed Zn-IMDC(IMDC, 4,5-imidazoledicarboxylic acid) and Cd-IMDC, two-dimensional(2D)hydrogen-bond organized metal–organic crystalline microsheets that exhibit rarely direct ultralong RTP upon UV excitation, benefiting from the appropriate heavy-atom effect and multiple triplet energy levels. The excitation-dependent and thermally stimulated ultralong phosphorescence endow the metal–organic systems great opportunities for information safety application and temperature-gated afterglow emission. The well-defined 2D microsheets present color-tunable and anisotropic optical waveguides under different excitation and temperature conditions, providing an effective way to obtain intelligent RTP-based photonic systems at the micro-and nano-scales.展开更多
Cu12Sb4S13 tetrahedrite has received great attention as an earth-abundant and environmental-friendly thermoelectric material. This work aims to uncover the thermoelectric performance-enhancing effect and the mechanism...Cu12Sb4S13 tetrahedrite has received great attention as an earth-abundant and environmental-friendly thermoelectric material. This work aims to uncover the thermoelectric performance-enhancing effect and the mechanism of nickel doping on tetrahedrite. A series of Cu12-xNixSb4S13-δ（x = 0.5, 0.7, 1.0, 1.5 and 2.0） compounds were synthesized by mechanical alloying combined with spark plasma sintering. It is found that the thermal conductivity sharply reduces with increasing Ni content over the entire temperature range,0.9 W m^-1K^-1, accompanied with an enhanced thermoelectric power factor. The model predicted that the reduced lattice thermal conductivity is attributed to mid-frequency phonon scattering, caused by precipitates and dislocations resulting from Ni doping. Consequently, a high ZT value up to 0.95 at 723 K was achieved for Cu11NiSb4S13-δ, corresponding to a ~46% increase over non-doped Cu12Sb4S13-δ. Furthermore,the cyclic measurement showed that the Ni-doped tetrahedrites displayed high chemical stability.展开更多
基金"Development of ecological knowledge-based advanced materials and technologies for multifunctional application" (Grant No.TR34005)"New approach to designing materials for energy conversion and storage" (Grant No.OI172060)"0-3D nanostructures for application in electronics and renewable energy sources:synthesis,characterisation and processing" (Grant No.III45007)
文摘The results of experimental investigation of n-type semiconductor based on Bi2Te3 alloy were presented. This material is used in manufacture of thermoelectric coolers and electrical power generation devices. BizTe2.88Se0.12 solid solution single crystal has been grown using the Czochralski method. Monitoring of structure changes of the sample was carried out by electron microscope. The elemental composition of the studied alloy was obtained by energy dispersive spectrometry （EDS） analysis and empirical formula of the compound was established. X-ray diffraction analysis confirmed that the Bi2Te2.88Se0.12 sample was a single phase with rhombohedral structure. The behavior upon heating was studied using differential thermal analysis （DTA） technique. Changes in physical and chemical properties of materials were measured as a function of increasing temperature by thermogravimetric analysis （TGA）. The lattice parameters values obtained by X-ray powder diffraction analyses of Bi2Te2.88Se0.12 are very similar to BizTe3 lattice constants, indicating that a small portion of tellurium is replaced with selenium. The obtained values for specific electrical and thermal conductivities are in correlation with available literature data. The Vickers microhardness values are in range between HV 187 and HV 39.02 and decrease with load increasing. It is shown that very complex process of infrared thermography can be applied for characterization of thermoelectric elements and modules.
基金Project(50436030)supported by the National Natural Science Foundation of China
文摘A two-dimensional model for freezing and thawing phase change heat transfer in biological tissue embedded with two cryoprobes was established.In this model,the blood vessels were considered as tree-like branched fractal network,and the effective flow rate and effective thermal conductivity of blood were obtained by fractal method.The temperature distribution and ice crystal growth process in biological tissue embedded with two cryoprobes during freezing-thawing process were numerically simulated.The results show that the growth velocity of ice crystal in freezing process from 200 to 400 s is more rapid than that from 400 to 600 s. Thawing process of frozen tissue occurs in the regions around cryoprobes tips and tissue boundary simultaneously,and the phase interfaces are close to each other until ice crystal melts completely.The distance of two cryoprobes has a more profound effect on the temperature distribution in freezing process at 400 s than at 800 s.
基金supported by the Beijing Municipal Natural Science Foundation(JQ20003)the National Natural Science Foundation of China(21771021,21822501,and 22061130206)+3 种基金the Fok Ying-Tong Education Foundation(171008)the Measurements Fund of Beijing Normal Universitythe State Key Laboratory of Heavy Oil Processing。
文摘Ultralong phosphorescent materials have numerous applications across biological imaging, lightemitting devices, X-ray detection and anti-counterfeiting. Triplet-state molecular phosphorescence typically accompanies the singlet-state fluorescence during photoluminescence, and it is still difficult to achieve direct triplet photoemission as ultralong room temperature phosphorescence(RTP). Here, we have designed Zn-IMDC(IMDC, 4,5-imidazoledicarboxylic acid) and Cd-IMDC, two-dimensional(2D)hydrogen-bond organized metal–organic crystalline microsheets that exhibit rarely direct ultralong RTP upon UV excitation, benefiting from the appropriate heavy-atom effect and multiple triplet energy levels. The excitation-dependent and thermally stimulated ultralong phosphorescence endow the metal–organic systems great opportunities for information safety application and temperature-gated afterglow emission. The well-defined 2D microsheets present color-tunable and anisotropic optical waveguides under different excitation and temperature conditions, providing an effective way to obtain intelligent RTP-based photonic systems at the micro-and nano-scales.
基金supported by the Basic Science Center Project of National Natural Science Foundation of China (51788104 and 11474176)Shenzhen Science and Technology Plan (JCYJ20150827165038323)
文摘Cu12Sb4S13 tetrahedrite has received great attention as an earth-abundant and environmental-friendly thermoelectric material. This work aims to uncover the thermoelectric performance-enhancing effect and the mechanism of nickel doping on tetrahedrite. A series of Cu12-xNixSb4S13-δ（x = 0.5, 0.7, 1.0, 1.5 and 2.0） compounds were synthesized by mechanical alloying combined with spark plasma sintering. It is found that the thermal conductivity sharply reduces with increasing Ni content over the entire temperature range,0.9 W m^-1K^-1, accompanied with an enhanced thermoelectric power factor. The model predicted that the reduced lattice thermal conductivity is attributed to mid-frequency phonon scattering, caused by precipitates and dislocations resulting from Ni doping. Consequently, a high ZT value up to 0.95 at 723 K was achieved for Cu11NiSb4S13-δ, corresponding to a ~46% increase over non-doped Cu12Sb4S13-δ. Furthermore,the cyclic measurement showed that the Ni-doped tetrahedrites displayed high chemical stability.
