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.     

Note: Heated sample platform for in situ temperature-programmed XPS

We present the design, fabrication, and performance of the multi-specimen heated platform for linear in situ heating during the Temperature-Programmed XPS (TPXPS). The platform is versatile, compatible with high vacuum (HV) and bakeout. The heater platform is tested under in situ linear heating of typical high surface area sorbent∕catalyst support--nanoporous TiO(2). The platform allows the TPXPS of multiple samples located on specimen disk that can be transferred in and out of the TPXPS chamber. Electric characteristics, temperature and pressure curves are provided. Heating power supply, PID temperature controller, data-logging hardware and software are described.     

EBSD coupled to SEM in situ annealing for assessing recrystallization and grain growth mechanisms in pure tantalum

An in situ annealing stage has been developed in‐house and integrated in the chamber of a Scanning Electron Microscope equipped with an Electron BackScattered Diffraction system. Based on the Joule effect, this device can reach the temperature of 1200°C at heating rates up to 100°C/s, avoiding microstructural evolutions during heating. A high‐purity tantalum deformed sample has been annealed at variable temperature in the range 750°C–1030°C, and classical mechanisms of microstructural evolutions such as recrystallization and grain coarsening phenomena have been observed. Quantitative measurements of grain growth rates provide an estimate of the mean grain boundary mobility, which is consistent with the value estimated from physical parameters reported for that material. In situ annealing therefore appears to be suited for complementing bulk measurements at relatively high temperatures, in the context of recrystallization and grain growth in such a single‐phase material.     

Design and construction of a new temperature-controlled chamber for light and confocal microscopy under monitored conditions: biological application for plant samples

A new light microscope–temperature‐controlled chamber (LM–TCC) has been constructed. The special feature of the light microscope–temperature‐controlled chamber is the Peltier‐element temperature control of a specimen holder for biological samples, with a volume capacity of 1 mL. This system has marked advantages when compared to other approaches for temperature‐controlled microscopy. It works in a temperature range of −10°C to +95°C with an accuracy of ±0.1°C in the stationary phase. The light microscope–temperature‐controlled chamber allows rapid temperature shift rates. A maximum heating rate of 12.9°C min⁻¹ and a maximum cooling rate of 6.0°C min⁻¹ are achieved with minimized overshoots (≤1.9°C). This machinery operates at low cost and external coolants are not required. Especially with samples absorbing irradiation strongly, temperature control during microscopy is necessary to avoid overheating of samples. For example, leaf segments of Ficaria verna exposed to 4500 μmol photons m⁻² s⁻¹ in a standard microscopic preparation show a temperature increase (δT) of 18.0°C, whereas in the light microscope–temperature‐controlled chamber this is reduced to 4°C. The kinetics of microscope‐light induced δT are described and infrared thermography demonstrates the dissipation of the temperature. Chloroplasts of the cold adapted plant Ranunculus glacialis show the tendency to form stroma‐filled protrusions in relation to the exposure temperature. The relative number of chloroplasts with protrusions is reduced at 5°C when compared to 25°C. This effect is reversible. The new light microscope–temperature‐controlled chamber will be useful in a wide range of biological applications where a rapid change of temperature during microscopic observations is necessary or has to be avoided allowing a simulation of ecologically relevant temperature scenarios.     

Quantification of extreme thermal gradients during in situ transmission electron microscope heating experiments

Studies on materials affected by large thermal gradients and rapid thermal cycling are an area of increasing interest, driving the need for real time observations of microstructural evoultion under transient thermal conditions. However, current in situ transmission electron microscope (TEM) heating stages introduce uniform temperature distributions across the material during heating experiments. Here, a methodology is described to generate thermal gradients across a TEM specimen by modifying a commercially available MEMS-based heating stage. It was found that a specimen placed next to the metallic heater, over a window, cut by FIB milling, does not disrupt the overall thermal stability of the device. Infrared thermal imaging (IRTI) experiments were performed on unmodified and modified heating devices, to measure thermal gradients across the device. The mean temperature measured within the central viewing area of the unmodified device was 3–5% lower than the setpoint temperature. Using IRTI data, at setpoint temperatures ranging from 900 to 1,300°C, thermal gradients at the edge of the modified window were calculated to be in the range of 0.6 × 10⁶ to 7.0 × 10⁶°C/m. Additionally, the Ag nanocube sublimation approach was used, to measure the local temperature across a FIB-cut Si lamella at high spatial resolution inside the TEM, and demonstrate “proof of concept” of the modified MEMS device. The thermal gradient across the Si lamella, measured using the latter approach was found to be 6.3 × 10⁶°C/m, at a setpoint temperature of 1,000°C. Finally, the applicability of this approach and choice of experimental parameters are critically discussed.     

A Controller for Heating a Liquid-Metal Ion Source

A pulse controller for heating a liquid-metal ion emitter in which a standard platinum resistance thermometer (R ₀ = 100 ) simultaneously acts as a heater and temperature sensor has been developed. High-voltage galvanic decoupling between the controller and power supply circuits makes it possible to keep the ion emitter and controller potential at a level of 6–12 kV with respect to the ground. The ion emitter is heated by constant-amplitude current pulses with an adjustable duration. The voltage across the heater is proportional to its resistance and, hence, temperature. The controller stabilizes the temperature of the ion emitter in the range 130–220°C with an accuracy of better than ±1°C. The efficiency of the device is 30%.     

Determination of magnetic field using a Fabry–Perot cavity containing novel nanoparticles

Mn_0.75Zn_0.25Fe₂O₄ nanoparticles were used to characterize magnetic fields using an all-fiber Fabry–Perot interferometer. The 20-nm nanoparticles were fabricated with citrate and displayed a coercive field of approximately 10?mT. The nanoparticles were dispersed in oleic acid to prepare a magnetic fluid to fill a Fabry–Perot structure fabricated by arc splicing with conventional single-mode and hollow core photonic crystal fibers. This device provided sensitivity and resolution of 0.11?dB/mT and 0.09?mT, respectively. Thermal analysis indicated that the magnetic measurements are weakly depending on temperature (0.7?pm/°C and 7?×?10^?3?dB/°C). This device offers low-cost fabrication, simple implementation and may be used in several industrial applications.     

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.     

An experimental study on spray and combustion characteristics based on fuel temperature of direct injection bio-ethanol-gasoline blending fuel

This study investigated the spray and combustion characteristics of a direct injection spark ignition type system based on the changes in the temperature of the blended fuel (with bio-ethanol and gasoline). The test was performed in a chamber with a constant volume. The diameter and width of the chamber were 86 mm and 39 mm, respectively. The bio-ethanol test fuel was blended at volume ratios of 0 %, 10 %, 20 % and 100 %. The temperature of the fuel was set as −7, 25 and 35 °C. The fuel injection pressure and ambient pressure were set as 4.5 and 0.5 MPa, respectively. The shape and characteristics of the spray were investigated through a spray experiment. The increase in the fuel temperature changed its density and viscosity; this in turn increased spray penetration and spray area and increased the bio-ethanol blending ratio. The combustion visualization and experimental analysis indicated that the decrease in the fuel temperature and the increase in the bio-ethanol blending ratio led to the high viscosity and low heating value. This resulted in an increase in the ignition delay and a decrease in the rate of heat release. It is necessary to adjust the spray strategy and ignition timing to adopt bio-ethanol blended fuel as an alternative fuel.

     

Thermal characteristics of an ammonia-charged closed-loop pulsating heat pipe

At this age, engineering applications are demanding effective ways of heat recovery and energy savings for their optimum performance. Among other cooling techniques, pulsating heat pipes have emerged as a convenient and cost effective thermal design solution due to its excellent heat transfer capability, high thermal efficiency and structural simplicity. The paper presents an experimental study on the operational limit of an aluminum closed-loop pulsating heat pipe (CLPHP) charged with ammonia. It consists of total 14 turns of aluminum pipe with 3 mm inner and 4 mm outer diameter. Ammonia was used as working fluid with 3 different filling ratios such as 0.4, 0.6 and 0.8. Operation orientations were vertical, 30°, 45°, 60°, 90° and 180° inclinations. Constant electric heat input of 36 W was applied to the heating block and temperature rise in various sections was monitored till steady state was reached. Temperature was measured at different locations of the CLPHP by using thermocouples. The effects of operational orientations and filling ratios were investigated on heat transfer by working fluid Q̇_php (Watt), overall heat transfer coefficient U (W/m² °C) and thermal resistance R (°C/W) considering the measured temperature. The result shows that, 0.4 and 0.6 fill ratios and inclination angle of 30º give better result than any other arrangements for CLPHP.

     

A Vacuum High-Temperature Electric Furnace for Investigating Thermal Properties of Materials

A vacuum electric furnace for investigating thermal properties of materials at temperatures of up to 2500°C was developed and tested. The furnace allows experimental studies of the heat conduction of both liquid and solid materials and measurements of the temperature and heat of phase transitions. It can be used to smelt and cake metals and alloys in vacuum or in an inert-gas medium. The heater is made of a graphite tube with special slots for increasing its resistance. The electric power is supplied from an ОСУ-40 step-down transformer. The temperature in the heated zone is controlled and monitored with an РТЭ-4.1 digital temperature controller connected to a computer. The power consumed by the furnace is no higher than 20 kW, and the volume of the working chamber is 0.3 L. The time for reaching the maximum temperature is at most 30 min.     

Design of multi-scaffold fabrication system for various 3D scaffolds

Three-dimensional (3D) porous scaffolds have been fabricated recently for tissue engineering applications through solid free-form fabrication (SFF) technologies. A multi-scaffold fabrication system for the fabrication of scaffolds, such as polymer, polymer/ceramic, ceramic, and nanofiber, was designed in this study. The various components, including a dispenser with a maximum pressure of 750 kPa, a thermostat with a maximum temperature of 250°C, a high-voltage power supply with a maximum output of 60 kV, and a syringe pump with small flow control, play important roles in determining the process characteristics of scaffolds. The system can process applicable biomaterials with extremely high accuracy with a precision nozzle. Several 3D scaffolds, including PCL, PCL/PLGA/β-TCP, β-TCP, and PCL nanofibers, were fabricated. The morphology and pore size of fabricated scaffolds were observed through scanning electron microscopy. Results show that the scaffolds manufactured in this study can be effectively utilized as bone regeneration scaffolds.     

塑料微流控芯片热压成形温度控制装置

采用聚合物如塑料等制作微流控芯片是拓展芯片应用,实现芯片产业化的关键。温度是塑料微流控芯片热压成形过程中的重要工艺参数。本文采用半导体热电致冷堆,设计了适合塑料芯片制作的温度控制装置;分析了升降温过程中所需的加热／制冷功率,并对升降温特性进行了研究;设计了半导体热电致冷堆供电电源装置。对温度控制装置的升／降温及温度控制精度进行了实验,并给出了实验结果。     

Development of a variable temperature mechanical loading device for in situ neutron scattering measurements

Understanding the phase transformation and failure mechanism of NiTi shape memory alloys under variable environments of high and low temperatures is critical to the establishment of constitutive properties and to the realization of controllable design. Information regarding the correlation between the phase transformation and deformation can be obtained by in situ neutron scattering measurements. Therefore, a variable temperature mechanical loading device is designed, which can be used for mechanical loading and in situ neutron scattering measurements in a variable temperature environment. Specifically, the device can achieve precise temperature control with a temperature change from −55 °C to 200 °C in a protective atmosphere. The rated load in the axial direction is 6 kN, and the maximum displacement of the unilateral grip is larger than 30 mm. In situ neutron scattering measurements can be performed through neutron windows, and the strain can be measured by digital image correlation technology. Moreover, the force sensor is calibrated to improve test precision. Through an evaluation of temperature uncertainty, the temperature measurement performance is estimated. Tensile tests of the NiTi alloy at variable temperatures are carried out, and preliminary results are given. The four deformation stages of the NiTi alloy can be seen from the stressstrain curve, which corresponds to the existing results. This demonstrates that the designed variable temperature mechanical loading device can supply the testing demands. The device provides a new way to study the relationship between the phase transformation and mechanical properties of NiTi shape memory alloys at variable temperatures.

     

Design and Implementation of a Three-Dimensional Temperature Measurement System for Indoor Object Monitoring

Abstract

In this paper, we report the design of a system equipped with a multielement thermopile for monitoring the temperature of indoor objects. We evaluate the performance of our measurement system, which comprises two microcontrollers, an analog-to-digital converter, two stepping motors, and four microswitches. We use an RS-232 or a wireless RS-232 interface that transmits temperature values and uses colors to indicate the temperature range on a PC screen. The system is inexpensive and can be used for three-dimensional temperature measurements. The effective detection range of this system is from ?20°C to 120°C or 180°C; the measurement error is within ±1°C. Experimental results demonstrate the effectiveness of the system for monitoring temperatures of remote indoor objects. Hence, it is possible to identify a hot spot in electrical heating equipment, a smoldering source hidden in upholstery, or the activities of a person in a room.     

Performance of a serial-connection multi-chamber piezoelectric micropump

1Introduction Micropumpsaretheessentialcomponentsin micro fluidicsystemwhichhasemergedasa popularareaofresearchwiththedevelopmentof micro electro mechanicalsystem(MEMS).Sinceoneoftheearlypiezoelectricmicropumps forinsulindeliverywasfabricatedin1978,more andmoreeffortshavebeenmadeintheresearch ofmicropumps[1].Duetotheirpreciselycon trolledflowrate,micropumpspresentpromising applicationsinanalyticalchemistry,medical treatment,pharmacy,bioengineering,fuel drop generatorforautomobileheater,etc.A…     

Time Proportioning Computer Control of Resistive Heating

ABSTRACT

The design and construction of an interface to regulate electrical power to a heater (resistive load) for temperature control is described. An overview of various techniques is presented and a specific approach to heater power control is described in detail. The method, however, can be easily adapted to other applications, for example, the manipulation of a solenoid valve to control an average fluid flow rate. The interface described here has a linear relation between the numerical computer output value and the power delivered to the load. This is convenient for both calibration and scaling purposes.     

高功率底发射VCSELs的制作与特性研究

研究制作了大面积底发射氧化限制面发射激光器,并分析了器件特性.通过增加有源区面积,改进制作工艺,采用Al2O3作钝化膜和多层复合HfO₂作增透膜等方法,提高了激光器输出功率.分析了最大输出功率与有源区直径和注入电流之间的依赖关系.结果表明:有源区直径分别为500μm和600μm的单管,室温下均达到连续输出功率1.95W,这也是目前国际上所实现的单管室温连续输出最高功率;实验所得最大输出功率与有源区直径和注入电流之间的依赖关系与理论计算所得结果一致.并特别讨论了直径200μm的器件的近场和远场光强分布,获得单横模工作.     

Prototype fabrication of a composite automobile body based on integrated structure

This paper describes the integrated fabrication and assembly approach used to replace a steel body cover in Samand Sarir automobile by composite one because composite could perform higher mechanical performance, i.e., strength, stiffness, and impact absorption energy at low velocity. Considering the integrated body as base design criteria, the steel cover is redesigned and fabricated by composite material. Tensile, flexural, and charpy impact tests were carried out to determine the properties of woven fabric laminated composite in [0/90°] and [±45°] fiber orientations. The selected composite laminate shows 2.9 times impact resistance; its desirability factors are improved 1.8 times for strength and 3.35 times for stiffness. Using finite element method, the impact of the composite body cover was simulated by ABAQUS for several thicknesses and fiber orientations. The FEM results indicate that finally laminated composite [0/90°]₇ can improve the crashworthiness of composite part in comparing to steel body cover. The integrated 3D preform of glass woven fabric was stitched like the shape of 3D model of body cover and placed in mold for prototype fabrication. It can be concluded that vacuum bagging as suggested fabrication method could be suitable for 3,000–5,000 annual production volume. Eventually, the fabricated composite body cover weighed 1.7 kg, which is 42% lighter than the steel body cover.     

A setup for thermodesorption measurements

An ultrahigh-vacuum setup for studying the interaction of ions with a solid by the thermodesorption spectroscopy method has been developed. The residual pressure achieved in the setup after heating is <2 × 10⁻⁷ Pa (the main component of the residual gas is H₂). A sample suspended by two tungsten wires is inserted into the main vacuum chamber through a lock chamber. The sample is heated by thermal radiation from the heater from room temperature to 1600–1700 K. The main features of the setup, the experimental technique, and the calibration of desorption flows are discussed. Examples of results obtained on the setup are presented.