The authors presented a new measuring method of the soil thermal conductivity,the probe method,which is designed and made based on the theory of line heat source. This method is used to measure thermal conductivity of...The authors presented a new measuring method of the soil thermal conductivity,the probe method,which is designed and made based on the theory of line heat source. This method is used to measure thermal conductivity of coarse sand,fine sand and silty clay in different water contents. The results that measured by the probe method are well consistent with those of QTM-D_2. The soil thermal conductivity increases in different levels with the increase of the water content. Compared the soil thermal conductivity measured by the probe method in laboratory with in-situ experiment,it shows that the measuring gap gradually increases with the increase of the depth. The reason is that the in-situ measuring thermal conductivity can reflect the actual situation of the soil mass.展开更多
Scanning ion conductance microscopy（SICM） is an emerging non-destructive surface topography characterization apparatus with nanoscale resolution. However, the low regulating frequency of probe in most existing modul...Scanning ion conductance microscopy（SICM） is an emerging non-destructive surface topography characterization apparatus with nanoscale resolution. However, the low regulating frequency of probe in most existing modulated current based SICM systems increases the system noise, and has difficulty in imaging sample surface with steep height changes. In order to enable SICM to have the capability of imaging surfaces with steep height changes, a novel probe that can be used in the modulated current based bopping mode is designed. The design relies on two piezoelectric ceramics with different travels to separate position adjustment and probe frequency regulation in the Z direction. To fiarther improve the resonant frequency of the probe, the material and the key dimensions for each component of the probe are optimized based on the multi-objective optimization method and the finite element analysis. The optimal design has a resonant frequency of above 10 kHz. To validate the rationality of the designed probe, microstructured grating samples are imaged using the homebuilt modulated current based SICM system. The experimental results indicate that the designed high frequency probe can effectively reduce the spike noise by 26% in the average number of spike noise. The proposed design provides a feasible solution for improving the imaging quality of the existing SICM systems which normally use ordinary probes with relatively low regulating frequency.展开更多
We report the direct measurements of conductivity and mobility in millimeter-sized single-crystalline graphene on SiO2/Si via van der Pauw geometry by using a home-designed four-probe scanning tunneling microscope（4P...We report the direct measurements of conductivity and mobility in millimeter-sized single-crystalline graphene on SiO2/Si via van der Pauw geometry by using a home-designed four-probe scanning tunneling microscope（4P-STM）. The gate-tunable conductivity and mobility are extracted from standard van der Pauw resistance measurements where the four STM probes contact the four peripheries of hexagonal graphene flakes, respectively. The high homogeneity of transport properties of the single-crystalline graphene flake is confirmed by comparing the extracted conductivities and mobilities from three setups with different geometry factors. Our studies provide a reliable solution for directly evaluating the entire electrical properties of graphene in a non-invasive way and could be extended to characterizing other two-dimensional materials.展开更多
Electrical conductivities of micron-scale aluminum wires were quantitatively measured by a four-point atomic force microscope (AFM) probe. This technique is a combination of the principles of the four-point probe meth...Electrical conductivities of micron-scale aluminum wires were quantitatively measured by a four-point atomic force microscope (AFM) probe. This technique is a combination of the principles of the four-point probe method and standard AFM. This technique was applied to the 99.999% aluminum wires with 350 nm thickness and different widths of 5.0, 25.0 and 50.0μm. Since the small dimensions of the wires, the geometrical effects were discussed in details. Experiment results show that the four-point AFM probe is mechanically flexible and robust. The four-point AFM probe technique is capable of measuring surface topography together with local electrical conductivity simultaneously. The repeatable measurements indicate that this technique could be used for fast in-situ electrical properties characterization of sensors and microelectromechanical system devices.展开更多
We have reported a method for measuring the thermal conductivity of liguids un-der high pressure previously [1,2].Such data are necessary for improving thetechnologies such like processing as acidity,pressure cracking...We have reported a method for measuring the thermal conductivity of liguids un-der high pressure previously [1,2].Such data are necessary for improving thetechnologies such like processing as acidity,pressure cracking,thermal exploitation ofpetroleum,etc. An apparatus has thus been constructed,as shown schematically in Fig.1,tomeasure the thermal conductivity of liquids under pressure up to 25 MPa and temperatureranging from 150 to 250℃.The thermal conductivity cell is cylindrical in from,35mmin length and 25mm in inner diameter.The sample is poured into the cell through展开更多
Three techniques of root pressure probe, pressure chamber and high pressure flow meter were used to measure the hydraulic conductivities （Lpr） of whole root systems of young maize （Zea mays L.） seedlings grown hyd...Three techniques of root pressure probe, pressure chamber and high pressure flow meter were used to measure the hydraulic conductivities （Lpr） of whole root systems of young maize （Zea mays L.） seedlings grown hydroponically under either drought or normal water conditions. Compared to normal water conditions, drought stress simulated by polyethylene glycol 6 000 （osmotic potential =-0.2 MPa） reduced Lpr in the root system by over 50%. It indicated that water permeability in the roots decreased significantly when plants suffered from water shortages. Moreover, there was no significant difference （P〈 0.05） on the Lpr values in the root systems developed under a given water stress regime among the three techniques used. Therefore, all three methods are acceptable to study the hydraulic conductivity of maize seedling root systems. We have also highlighted some of the technical limitations of each method. It can be inferred that the root pressure probe is preferable for young maize seedlings because it is subtle and has the additional ability to determine solute transport properties, but the method is time consuming. Other advantages and disadvantages of each technique are discussed in order to acquaint researchers with basic information that could contribute to their choice of an appropriate technique for future studies.展开更多
The title compound was prepared and treated by high temperature gaseous mix rare earth permeation. ICP, IR, TG-DTA, XPS, XRD were used to characterize the title compound and the treated sample. The results confirm tha...The title compound was prepared and treated by high temperature gaseous mix rare earth permeation. ICP, IR, TG-DTA, XPS, XRD were used to characterize the title compound and the treated sample. The results confirm that Ce and La can be permeated into the body of the title compound. Four-probe method was used to measure the conductivities. A novel result that the conductivity of the permeated compound (δ=9.2×10 -3 S·cm -1)improved by 7.1×106 times than that of the title compound(δ=1.29×10 -9 S·cm -1) is received.展开更多
Silicon carbide(SiC) is a promising platform for fabricating high-voltage, high-frequency and high-temperature electronic devices such as metal oxide semiconductor field effect transistors in which many junctions or i...Silicon carbide(SiC) is a promising platform for fabricating high-voltage, high-frequency and high-temperature electronic devices such as metal oxide semiconductor field effect transistors in which many junctions or interfaces are involved. The work function(WF) plays an essential role in these devices. However, studies of the effect of conductive type and polar surfaces on the WF of SiC are limited. Here, we report the measurement of WFs of Si-and C-terminated polar surfaces for both p-type and n-type conductive 4H-SiC single crystals by scanning Kelvin probe microscopy(SKPFM). The results show that p-type SiC exhibits a higher WF than n-type SiC.The WF of a C-terminated polar surface is higher than that of a Si-terminated polar surface, which is further confirmed by first-principles calculations. By revealing this long-standing knowledge gap, our work facilitates the fabrication and development of SiC-based electronic devices, which have tremendous potential applications in electric vehicles, photovoltaics, and so on. This work also shows that SKPFM is a good method for identifying polar surfaces of SiC and other polar materials nondestructively, quickly and conveniently.展开更多
Conventional conductivity methods for measuring the void fraction in gas-liquid multiphase systems are typically affected by accuracy problems due to the presence of fluid flow and salinity.This study presents a novel...Conventional conductivity methods for measuring the void fraction in gas-liquid multiphase systems are typically affected by accuracy problems due to the presence of fluid flow and salinity.This study presents a novel approach for determining the void fraction based on a reciprocating dynamic conductivity probe used to measure the liquid film thickness under forced annular-flow conditions.The measurement system comprises a cyclone,a conductivity probe,a probe reciprocating device,and a data acquisition and processing system.This method ensures that the flow pattern is adjusted to a forced annular flow,thereby minimizing the influence of complex and variable gas-liquid flow patterns on the measurement results;Moreover,it determines the liquid film thickness solely according to circuit connectivity rather than specific conductivity values,thereby mitigating the impact of salinity.The reliability of the measurement system is demonstrated through laboratory experiments.The experimental results indicate that,in a range of gas phase superficial velocities 5–20 m/s and liquid phase superficial velocities 0.079–0.48 m/s,the maximum measurement deviation for the void fraction is 4.23%.展开更多
This investigation was done to study the gas filled powder insulation and thermal conductivity probe for the measurent of thermal conductivity of powders.The mathematical analysis showed that the heat capacity of the ...This investigation was done to study the gas filled powder insulation and thermal conductivity probe for the measurent of thermal conductivity of powders.The mathematical analysis showed that the heat capacity of the probe itself and the thermal rsistance between the probe and powder must be considered .The authors developed a slender probe and measured the effective thermal conductivity of sillca and carbon black powders under a variety of conditions.展开更多
基金Supported by Project of National Natural Science Foundation of China(No.41372239)
文摘The authors presented a new measuring method of the soil thermal conductivity,the probe method,which is designed and made based on the theory of line heat source. This method is used to measure thermal conductivity of coarse sand,fine sand and silty clay in different water contents. The results that measured by the probe method are well consistent with those of QTM-D_2. The soil thermal conductivity increases in different levels with the increase of the water content. Compared the soil thermal conductivity measured by the probe method in laboratory with in-situ experiment,it shows that the measuring gap gradually increases with the increase of the depth. The reason is that the in-situ measuring thermal conductivity can reflect the actual situation of the soil mass.
基金Supported by National Natural Science Foundation of China(Grant No.51375363)
文摘Scanning ion conductance microscopy（SICM） is an emerging non-destructive surface topography characterization apparatus with nanoscale resolution. However, the low regulating frequency of probe in most existing modulated current based SICM systems increases the system noise, and has difficulty in imaging sample surface with steep height changes. In order to enable SICM to have the capability of imaging surfaces with steep height changes, a novel probe that can be used in the modulated current based bopping mode is designed. The design relies on two piezoelectric ceramics with different travels to separate position adjustment and probe frequency regulation in the Z direction. To fiarther improve the resonant frequency of the probe, the material and the key dimensions for each component of the probe are optimized based on the multi-objective optimization method and the finite element analysis. The optimal design has a resonant frequency of above 10 kHz. To validate the rationality of the designed probe, microstructured grating samples are imaged using the homebuilt modulated current based SICM system. The experimental results indicate that the designed high frequency probe can effectively reduce the spike noise by 26% in the average number of spike noise. The proposed design provides a feasible solution for improving the imaging quality of the existing SICM systems which normally use ordinary probes with relatively low regulating frequency.
基金supported by the Science Fund from the Ministry of Science and Technology of China(Grant No.2013CBA01600)the National Key Research&Development Project of China(Grant No.2016YFA0202300)+1 种基金the National Natural Science Foundation of China(Grant Nos.61474141,61674170,61335006,61390501,51325204,and 51210003)the Chinese Academy of Sciences(CAS) and Youth Innovation Promotion Association of CAS(Grant No.20150005)
文摘We report the direct measurements of conductivity and mobility in millimeter-sized single-crystalline graphene on SiO2/Si via van der Pauw geometry by using a home-designed four-probe scanning tunneling microscope（4P-STM）. The gate-tunable conductivity and mobility are extracted from standard van der Pauw resistance measurements where the four STM probes contact the four peripheries of hexagonal graphene flakes, respectively. The high homogeneity of transport properties of the single-crystalline graphene flake is confirmed by comparing the extracted conductivities and mobilities from three setups with different geometry factors. Our studies provide a reliable solution for directly evaluating the entire electrical properties of graphene in a non-invasive way and could be extended to characterizing other two-dimensional materials.
基金Project( 17206011) supported by the Japan Society for the Promotion of Science
文摘Electrical conductivities of micron-scale aluminum wires were quantitatively measured by a four-point atomic force microscope (AFM) probe. This technique is a combination of the principles of the four-point probe method and standard AFM. This technique was applied to the 99.999% aluminum wires with 350 nm thickness and different widths of 5.0, 25.0 and 50.0μm. Since the small dimensions of the wires, the geometrical effects were discussed in details. Experiment results show that the four-point AFM probe is mechanically flexible and robust. The four-point AFM probe technique is capable of measuring surface topography together with local electrical conductivity simultaneously. The repeatable measurements indicate that this technique could be used for fast in-situ electrical properties characterization of sensors and microelectromechanical system devices.
文摘We have reported a method for measuring the thermal conductivity of liguids un-der high pressure previously [1,2].Such data are necessary for improving thetechnologies such like processing as acidity,pressure cracking,thermal exploitation ofpetroleum,etc. An apparatus has thus been constructed,as shown schematically in Fig.1,tomeasure the thermal conductivity of liquids under pressure up to 25 MPa and temperatureranging from 150 to 250℃.The thermal conductivity cell is cylindrical in from,35mmin length and 25mm in inner diameter.The sample is poured into the cell through
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education,China(20093702120002)the Shandong Province Postdoctoral Special Fund Innovative Projects,China(200903024)
文摘Three techniques of root pressure probe, pressure chamber and high pressure flow meter were used to measure the hydraulic conductivities （Lpr） of whole root systems of young maize （Zea mays L.） seedlings grown hydroponically under either drought or normal water conditions. Compared to normal water conditions, drought stress simulated by polyethylene glycol 6 000 （osmotic potential =-0.2 MPa） reduced Lpr in the root system by over 50%. It indicated that water permeability in the roots decreased significantly when plants suffered from water shortages. Moreover, there was no significant difference （P〈 0.05） on the Lpr values in the root systems developed under a given water stress regime among the three techniques used. Therefore, all three methods are acceptable to study the hydraulic conductivity of maize seedling root systems. We have also highlighted some of the technical limitations of each method. It can be inferred that the root pressure probe is preferable for young maize seedlings because it is subtle and has the additional ability to determine solute transport properties, but the method is time consuming. Other advantages and disadvantages of each technique are discussed in order to acquaint researchers with basic information that could contribute to their choice of an appropriate technique for future studies.
文摘The title compound was prepared and treated by high temperature gaseous mix rare earth permeation. ICP, IR, TG-DTA, XPS, XRD were used to characterize the title compound and the treated sample. The results confirm that Ce and La can be permeated into the body of the title compound. Four-probe method was used to measure the conductivities. A novel result that the conductivity of the permeated compound (δ=9.2×10 -3 S·cm -1)improved by 7.1×106 times than that of the title compound(δ=1.29×10 -9 S·cm -1) is received.
基金financially supported by the Beijing Municipal Science and Technology Project (Grant No. Z231100006023015)the Major Scientific and Technological Research and Development of Shunyi District of Beijingthe Chinese Academy of Sciences。
文摘Silicon carbide(SiC) is a promising platform for fabricating high-voltage, high-frequency and high-temperature electronic devices such as metal oxide semiconductor field effect transistors in which many junctions or interfaces are involved. The work function(WF) plays an essential role in these devices. However, studies of the effect of conductive type and polar surfaces on the WF of SiC are limited. Here, we report the measurement of WFs of Si-and C-terminated polar surfaces for both p-type and n-type conductive 4H-SiC single crystals by scanning Kelvin probe microscopy(SKPFM). The results show that p-type SiC exhibits a higher WF than n-type SiC.The WF of a C-terminated polar surface is higher than that of a Si-terminated polar surface, which is further confirmed by first-principles calculations. By revealing this long-standing knowledge gap, our work facilitates the fabrication and development of SiC-based electronic devices, which have tremendous potential applications in electric vehicles, photovoltaics, and so on. This work also shows that SKPFM is a good method for identifying polar surfaces of SiC and other polar materials nondestructively, quickly and conveniently.
基金the National Natural Science Foundation of China(No.62173049)the Open Fund of the Hubei Key Laboratory of Oil and Gas Drilling and Production Engineering(Yangtze University),YQZC202309.
文摘Conventional conductivity methods for measuring the void fraction in gas-liquid multiphase systems are typically affected by accuracy problems due to the presence of fluid flow and salinity.This study presents a novel approach for determining the void fraction based on a reciprocating dynamic conductivity probe used to measure the liquid film thickness under forced annular-flow conditions.The measurement system comprises a cyclone,a conductivity probe,a probe reciprocating device,and a data acquisition and processing system.This method ensures that the flow pattern is adjusted to a forced annular flow,thereby minimizing the influence of complex and variable gas-liquid flow patterns on the measurement results;Moreover,it determines the liquid film thickness solely according to circuit connectivity rather than specific conductivity values,thereby mitigating the impact of salinity.The reliability of the measurement system is demonstrated through laboratory experiments.The experimental results indicate that,in a range of gas phase superficial velocities 5–20 m/s and liquid phase superficial velocities 0.079–0.48 m/s,the maximum measurement deviation for the void fraction is 4.23%.
文摘This investigation was done to study the gas filled powder insulation and thermal conductivity probe for the measurent of thermal conductivity of powders.The mathematical analysis showed that the heat capacity of the probe itself and the thermal rsistance between the probe and powder must be considered .The authors developed a slender probe and measured the effective thermal conductivity of sillca and carbon black powders under a variety of conditions.
