High temperature Seebeck coefficient and resistance measurement system for thermoelectric materials in the thin disk geometry

A versatile apparatus to measure the cross-plane Seebeck coefficient and the resistivity of bulk samples shaped as disks or thin plates, over a temperature range of 300 K-620 K with possible extension to higher temperatures, is presented. It is constructed from readily available equipment and instrumentation with parts that are easily manufactured. The Seebeck coefficient is measured over an average region of the sample under steady-state conditions. The sample resistance is measured using a four-point alternating current method and scaled to room temperature measurements with known geometry to calculate resistivity. A variety of sample shapes are supported. Most importantly, the support of the thin disk geometry allows for the very same samples to be used in a laser flash instrument. The design allows for rough vacuum, high vacuum, or purging with inert gases in the sample chamber. Measurements on thermoelectric ZnSb and a Ni reference material are presented.     

A self-heating 2ω method for Seebeck coefficient measurement of thermoelectric materials

A novel and reliable self-heating 2ω method has been developed to measure the Seebeck coefficient of the microscale/nanoscale thermoelectric materials. Based on the analytical solution of the transient heat-conduction equation of the specimen heated by a harmonic current, two measurement modes have been developed: (1) the Seebeck coefficient can be directly extracted from the ratio of experimentally measured 2ω Seebeck voltage to theoretically predicted 2ω temperature drop oscillation; and (2) the Seebeck coefficient can be steadily extracted from the measured 2ω and 3ω voltages. This approach has been applied to a 25.4 μm thick K-type thermocouple and the measured Seebeck coefficient corresponds well with the nominal value.     

A high temperature apparatus for measurement of the Seebeck coefficient

A high temperature Seebeck coefficient measurement apparatus with various features to minimize typical sources of error is designed and built. Common sources of temperature and voltage measurement error are described and principles to overcome these are proposed. With these guiding principles, a high temperature Seebeck measurement apparatus with a uniaxial 4-point contact geometry is designed to operate from room temperature to over 1200 K. This instrument design is simple to operate, and suitable for bulk samples with a broad range of physical types and shapes.     

Thermal expansion of solids at high temperatures by the gamma attenuation technique

A new technique is described for the measurement of the thermal expansion of isotropic solid materials at high temperatures. The method utilizes gamma attenuation to measure thermal expansion with a noncontacting probe. The experimental apparatus and analytical method are described, and results are presented for aluminum to 900 K and type 303 stainless steel to 1660 K to illustrate the use and precision of the technique. These results agree with published values measured by other techniques, and in the case of the stainless steel alloy, some new results are presented in the temperature range 1400-1660 K.     

A laboratory apparatus for streaming potential and resistivity measurements on soil samples

We describe an apparatus designed to perform streaming potential and resistivity measurements on unconsolidated soil samples. The apparatus enables the use of both unidirectional and oscillatory flow methods to measure the streaming potential coupling coefficient (C); the direct current resistivity method is used to measure the bulk resistivity (rho) of the soil sample. Measuring both of these parameters on the same sample under the same conditions enables us to properly characterize the streaming current cross-coupling coefficient (L). The apparatus is designed to test reconstituted saturated soil samples up to a maximum grain size of 9.5 mm, and hydraulic gradients from less than 0.1 up to a maximum of 4 m of H(2)Om in flow-through experiments. Excellent agreement between C values measured using the unidirectional and oscillatory flow methods validates the oscillatory flow method for unconsolidated samples.     

A hot-wire probe for thermal measurements of nanowires and nanotubes inside a transmission electron microscope

A hot wire probe has been developed for use inside a transmission electron microscope to measure the thermal resistance of individual nanowires, nanotubes, and their contacts. No microfabrication is involved. The probe is made from a platinum Wollaston wire and is pretensioned to minimize the effects of thermal expansion, intrinsic thermal vibrations, and Lorentz forces. An in situ nanomanipulator is used to select a particular nanowire or nanotube for measurement, and contacts are made with liquid metal droplets or by electron-beam induced deposition. Detailed thermal analysis shows that for best sensitivity, the thermal resistance of the hot-wire probe should be four times that of the sample, but a mismatch of more than two orders of magnitude may be acceptable. Data analysis using the ratio of two ac signals reduces the experimental uncertainty. The range of detectable sample thermal resistances spans from approximately 10(3) to 10(9) KW. The probe can also be adapted for measurements of the electrical conductance and Seebeck coefficient of the same sample. The probe was used to study a multiwalled carbon nanotube with liquid Ga contacts. The measured thermal resistance of 3.3 x 10(7) KW had a noise level of approximately +/-3% and was repeatable to within +/-10% upon breaking and re-making the contact.     

Friction and wear during twin-disc experiments under ambient and cryogenic conditions

We present a classical rolling contact apparatus where two discs roll and slide under a constant normal loading. Experimental results concerning bearing steel used in ambient air or under severe temperature conditions (liquid nitrogen) are presented. A simplified model proposed by Kalker (Fastsim) is used to identify the dynamic friction coefficient between these discs and to study the apparatus parameters’ influence on dissipated energy. Wear evolution is simulated using classical Archard's law and compared to measured profiles. Influence of ambient conditions is highlighted by comparing friction and wear coefficients.     

改进JYJ-90型天幕靶用于XX产品初速测试

为改进一套JYJ-90型天幕靶用于测试XX产品弹丸的飞行速度，以光电转换原理为基础，采用光电子技术形成弹丸空间坐标的无形光幕，同时由光电传感器与多路测试仪结合测每发弹的初速，全部数据由计算机采集和处理。完成了一套用于上述目的的测试系统。这种集光、机、电、计算机多种先进技术为一体的先进测试设备可以完全有效地用于XX产品弹丸的初速测试。     

Simple apparatus for the multipurpose measurements of different thermoelectric parameters

A simple apparatus for the simultaneous measurement of Seebeck coefficient (α) and electrical resistivity (ρ) in the temperature range 100-600 K, Hall coefficient (R_H) and transverse Nernst-Ettingshausen coefficient (N) in the temperature range 300-600 K of the bar shaped samples has been fabricated. The instrument has been designed so simply that the sample can be easily mounted for the fast measurements of different thermoelectric parameters. The sample holder assembly of the apparatus has been designed so cleverly that any part of that section can be replaced in case of any damage; and so it can be regarded as a modular based system. The apparatus is relatively cheaper in cost and also portable.     

一种测量板料拉深摩擦因数的传感器设计

针对板料拉深成形中如何测量板料法兰处真实摩擦分布情况以及如何评价润滑剂好坏的难题,设计了一套基于电阻应变计和双层悬臂梁原理的探针组合式传感器安装于拉深凹模中,用来实时测量板料法兰上一点处所受的垂向正向力和径向切向力,可计算出该测量点处的实时摩擦因数.试验证明：该传感器能真实地反映板料拉深成形过程中法兰平面上的实际摩擦分布情况.     

新型多功能膜/基结合力测定仪的研制

采用改进划痕法原理及切向力检测临界载荷方法，研制了一种新型多功能膜／基结合力测定仪。该仪器结构新颖，实用简便，不仅能测定金属膜层与基体的结合强度，还能对金属膜层进行模拟单颗粒磨损试验。试验表明，该仪器具有较高的可靠性。     

Simple apparatus to measure Seebeck coefficient up to 900 K

An apparatus for measuring Seebeck coefficient (S) has been designed that allows measurement of S from room temperature to 900 K. It is constructed from readily available equipment and instrumentation with parts that can be easily fabricated. The details of instrument fabrication, sources of errors, method of calibration, typical measurement in test sample are described. We report the Seebeck coefficient measurement of Ca-cobaltite (Ca₃Co₄O₉) a p-type thermoelectric material. The obtained results from the fabricated setup are well matched with the reported and standard instrument data with standard deviation of ±3%.     

微型热电发电器的性能测试分析

按照微型热电发电器输出功率的理论模型，对内阻、塞贝克系数和热导率等热电性能参数在不同温度范围内进行了测量和拟合。实验测试了不同电偶臂对数、电偶臂高度以及不同冷热端温度时微型热电发电器的最大输出功率，结果表明：一定范围内的最大输出功率随电偶臂高度的减小而增大，对电偶臂高度面积的比值进行适当选取，可使最大输出功率达到最优值；一定范围内的最大输出功率随电偶臂对数的增多而增大；温差和平均温度达到一定值时，最大输出功率可得到最优。根据测试分析结果，研制了微小型热电转换装置。     

Development of an integrated apparatus of micro-EDM and micro-CMM

Authors have developed a 4-axis micro-CMM that has miniaturized probe. By using an L-shaped probe, the micro-CMM can measure three dimensional coordinates of the high aspect ratio structures such as micro-holes. However, an installation error of the probe primarily affects the accuracy in the micro-CMM because the probe was previously machined in other micro-EDMs. In this research, we developed an integrated apparatus of micro-EDM and micro-CMM. The micro-EDM has 5-axis control with a general plate tool electrode and it can make probes of various shapes by the electric discharge scanning method. And the 4-axis micro-CMM has a mechanism that rotates the probe and it can measure with sub-micrometer accuracy. In this paper, Authors introduce a basic configuration of the integrated apparatus, machining method of the probe, and measuring method and measurement result of the micro-hole.     

Automated instrumentation for high-temperature Seebeck coefficient measurements

The fabrication of automated instrumentation for high-temperature Seebeck coefficient measurements is presented. K-type thermocouples were used to measure the average temperature of the sample and the Seebeck voltage. The temperature dependence of the Seebeck coefficients of the thermocouple and its negative leg were obtained by the integration method. A steady-state-based differential technique was used for Seebeck coefficient measurement. The use of limited components and a thin heater simplified the sample holder design and minimized heat loss. The power supplied to the heater determined the temperature difference across the sample and the measurement was carried out by achieving a steady state. A LabVIEW-based program was constructed to automate the measurements. The complete setup was fabricated using commonly available materials. This instrument is standardized for materials with a wide range of Seebeck coefficients and temperature differences. High temperature measurements for iron, constantan, bismuth, and Bi_0.36Sb_1.45Te₃ were carried out and the results were in good agreement with standard values.     

Friction Coefficient Measurement of an In Vivo Murine Cornea

Ocular tear film mucins and lipids promote lubricity of the corneal surface during ocular movements. The mechanisms of this lubricity are difficult to model and to measure due to the delicate nature of the film itself and the conditions under which it exists. This study describes a kinetic friction coefficient measured between a glass probe and a living mouse eye. A portable custom micro-tribometer was used to prescribe sliding motions and record normal and frictional forces. Friction coefficient measured over both sliding directions resulted in µ = 0.068 under a pressure of approximately 12 kPa. In vivo measurements may enhance the understanding of corneal friction response, as well as provide an empirical friction coefficient for more complex mechanical models.     

Four-probe measurements of the in-plane thermoelectric properties of nanofilms

Measuring in-plane thermoelectric properties of submicron thin films has remained a challenging task. Here we report a method based on a suspended microdevice for four-probe measurements of the Seebeck coefficient, thermal conductivity, electrical conductivity, and thermoelectric figure of merit of patterned indium arsenide (InAs) nanofilms assembled on the microdevice. The contact thermal resistance and intrinsic thermal resistance of the 40 nm thick InAs nanofilm sample were measured by using the nanofilm itself as a differential thermocouple to determine the temperature drops at the contacts. The microdevice was also used to measure a 190 nm thick silicon dioxide (SiO(2)) film and the results were compared with those reported in the literature. A through-substrate hole under the suspended microdevice allows for transmission electron microscopy characterization of the nanofilm sample assembled on the device. This capability enables one to correlate the measured thermoelectric properties with the crystal structures of the nanofilm.     

Automated instrumentation for the determination of the high-temperature thermoelectric figure-of-merit

Here we report the fabrication of high temperature measurement instrumentation to measure the thermoelectric figure of merit. This setup facilitates the simultaneous measurement of Seebeck coefficient, thermal conductivity, and electrical resistivity required to evaluate the figure of merit. Measurement of temperature, as well as voltages using same thermocouples, simplified the design by minimizing sensors and wires. The limited number of components in the sample holder further simplify the design and make it small in size and lightweight. A dedicated thin heater has been constructed to minimize heat losses. Further, low heat loss is achieved by optimizing the insulator dimensions. To measure power delivered to the heater, the four-wire technique was used. Low cost and commonly available materials used in the fabrication of various components make it more accessible to the user as any parts can be easily replaced in case of damage. A dedicated program was built in the Python language to automate the measurement process. A p-type Bi_0.36Sb_1.45Te₃ sample was used to calibrate the instrumentation. The measured values were in good agreement with the literature results.     

High temperature Z-meter setup for characterizing thermoelectric material under large temperature gradient

To properly estimate a thermoelectric material's performance, one should be able to characterize a single thermoelectric (TE) element with a large temperature gradient. In this work, we present an experimental setup including a Z-meter that can heat the sample to a very high temperature of 1200 °C in vacuum. The Z-meter can simultaneously measure all three thermoelectric parameters (Seebeck coefficient, thermal conductivity, and electrical conductivity), as well as measure the generated power and the efficiency for a single TE leg. Furthermore, this measurement of power conversion efficiency is used to generate a measure of the material's ZT. An in situ metallurgical bond was used to achieve low thermal (0.05 Kcm(2)∕W) and electrical (3 mΩ) contact parasitics. An integrated strain gauge ensures reproducible thermal contact. At high temperature (>600 K), radiative heat transfer is modeled and the instrument is optimized to suppress the systematic error to below 7%. The TE parameters and ZT for a bulk-sample (Bi(2)Te(3)) and a thin-film sample (ErAs:InGaAlAs) with a large temperature gradient (ΔT ～ 200 K) have been measured and are within 3%-7% of the independently measured values.     

A differential laser autocollimation probe for on-machine measurement

An optical probe based on the principle of differential laser autocollimation has been developed for the purpose of on-machine measurement of mirror shapes. The probe is so compact that it can be mounted on diamond lathes. It can be rotated by a stepping motor about an axis perpendicular to the optical axis of measurement, and has been used to measure mirror shapes on an apparatus that imitates the conditions of an on-machine measurement system. The probe can reduce remarkably the measurement errors due to vibrational and thermal noises that could not be avoided previously in on-machine measurement. Estimating from repeatability, accuracy is better than 0.1 μm in measurement of a parabolic curve whose depth is >1 mm and length is ≈ 100 mm.