This work is supported by the German Federal Ministry for Economic Affairs within the project &#8220;Feuerdrache&#8221; (0324205B). The authors thank the co-workers that contributed to this work and the project partners (InfraTec, Rehm Thermal Systems, Heraeus Noblelight, Trumpf Photonic Components) for co-financing and providing outstanding support.

1. Installation of IR camera into a conveyor belt furnace
<ol>
	<li>Decide which part of the furnace should be measured by the IR camera. 
	NOTE: Here, the peak zone of the firing process is chosen (see the orange highlighted zone in the firing area of Figure 1A).</li>
	<li>Define the temperature range of interest that the IR camera should detect (e.g., 700&#8722;900 &#176;C, the typical peak temperature range of the firing process).</li>
	<li>Determine, or at least estimate (through experiments or literature), the temperature,&#160;spectral, and angular dependent emissions of the object(s) of interest (e.g., silicon solar cell) to identify the wavelength range(s) of highest emission for the temperature range of interest (under a specific camera angle). 
	NOTE: Here, the emission is estimated based on previous literature3 and a software called RadPro10, which calculates the spectral, angular, and temperature-dependent emissivity for materials of interest.</li>
	<li>Deciding on the IR camera type 
	NOTE: Here, a midwave infrared (MWIR) indium antimonide (InSb) camera (Table of Materials) is used.
	<ol>
		<li>Choose a camera that can detect the temperature range of interest.</li>
		<li>Select a camera whose detection wavelength range matches the wavelength range of highest emission of the object of interest in the temperature range of interest.</li>
		<li>Avoid as much parasitic radiation detection by the camera as possible by avoiding objects that emit or reflect radiation into the camera field of view (e.g., IR lamps in a furnace).&#160;</li>
		<li>Decide on the necessary spatial and temporal resolution of the camera (e.g., 640 px x 512 px and 125 Hz [full image] for the used camera here).</li>
	</ol>
	</li>
	<li>Realize a sufficient optical path from the IR camera to object (see Figure 1B).
	<ol>
		<li>Avoid disturbing objects in the optical path (e.g., IR lamps causing direct or reflected light).</li>
		<li>Position the camera outside of the furnace chamber, if possible. 
		NOTE: Most cameras have low operating temperatures (e.g., up to 50 &#176;C). Make sure in advance that the camera position can be changed, if desired.</li>
		<li>Remove the furnace wall and isolation at the location where the optical path should be and replace the hole with an insulating IR window.
		<ol>
			<li>Choose the appropriate material for the window that meets the following demands: 1) as transparent as possible for the detection wavelength (&#955;) range of the camera (e.g., quartz glass window for ~0.2 &#181;m &#60; &#955; &#60; 3 &#181;m, sapphire window for ~0.4 &#181;m &#60; &#955; &#60; 4.2 &#181;m) and 2) able to isolate the furnace chamber thermally. 
			NOTE: The resulting temperatures of the window may influence the window transmission.</li>
			<li>Avoid damage of the IR window. Do not tighten the window to avoid breakage during heat expansion. 
			NOTE: The window material should have a sufficient amount of space to expand when heated up.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Check the resulting field of view (FOV) of the IR camera by examining the thermography image via the IR camera software. Identify the targeted object and its temperature in the thermography image. Adjust the FOV, if necessary.</li>
</ol>
2. Global&#160;customer temperature correction of a fabrication calibrated IR camera
CAUTION: The fabrication of the IR camera is assumed to include a radiometric calibration.
<ol>
	<li>Spot local optical artifacts, such as reflection and background radiation.</li>
	<li>Conduct classic thermocouple measurements of the object while simultaneously recording the wafer including thermocouple with the IR camera.
	<ol>
		<li>Check the validity of the used thermocouples. Search for known characteristic temperature points in the temperature profile of the processed object that can be clearly visibly detected (e.g., disruption in a smooth line). If the thermocouple measures these temperature points correctly, the thermocouple is most likely correctly calibrated.</li>
		<li>Example using silicon solar cells
		<ol>
			<li>Place the thermocouple on the rear aluminum side of the wafer. Take a temperature profile for a standard firing process11.</li>
			<li>Validate the thermocouples by determining whether there is a disruption in the temperature profile from step 2.2.2.1 around the Al-Si eutectic temperature of 577 &#176;C in the form of a flatter curve (as is the case in Figure 2D). 
			NOTE: If the disruption occurs at the temperature around 577 &#176;C, it is a sign that the temperature measurement by the thermocouple is accurate. Use only validated thermocouples for the following steps.</li>
		</ol>
		</li>
		<li>Conduct thermocouple measurements in the temperature range of interest at the same object spot (multiple times for statistical reasons), then at spatially various random spots (for statistical reasons) to obtain time-temperature profiles.</li>
	</ol>
	</li>
	<li>Determine the local uncorrected thermography object temperature underneath the thermocouples from the thermocouple measurements from step 2.2.3 while placing the thermocouple on the upper side of the object.
	<ol>
		<li>Check for a possible local temperature drop around the contacting thermocouple (due to heat dissipation and shading). Assume the temperature in the vicinity of the thermocouple as the object temperature directly under the thermocouple, if a local temperature drop is not present.</li>
		<li>Perform the following steps if a local temperature drop is present.
		<ol>
			<li>Determine the spatial temperature gradient of the present temperature drop in the part that is not covered by the thermocouple. 
			NOTE: It is recommended to determine the gradient at multiple spots around the temperature drop (radially) and determine&#160;an average gradient.</li>
			<li>Estimate the contribution of possible optical artifacts induced by the thermocouple (example protocol for a case in which homogenous temperature along the cell depth direction is assumed, such as in Si solar cells).
			<ol>
				<li>Place the thermocouple on the surface opposite to the measured surface and repeat the thermocouple and thermography measurement in this configuration (as shown in Figure 3A). Turn the object, including the thermocouple, around so that the thermocouple is not in the optical path between the camera and object. 
				NOTE: If the gradient of the local temperature drop is the same for the thermocouple being inside and outside of the optical path (i.e., attached to the measured or opposite surface), it is a sign that the thermocouple most likely does not induce optical artifacts.</li>
				<li>Extrapolate the gradient of the temperature drop in the case of the thermocouple contacting the measured surface (i.e., inside optical path) to the area covered by the thermocouple to obtain the temperature of the object underneath the thermocouple.</li>
				<li>Repeat 2.3.2.2.2 for each measurement from step 2.2.3.</li>
			</ol>
			</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Alternative to 2.3: Determine the local uncorrected thermography object temperature underneath the thermocouples from the thermocouple measurements from step 2.2.3 while placing the thermocouple on the lower side of the object.&#160;To determine the local uncorrected thermography solar cell temperature under the thermocouple, extract the local temperature at the position of the thermocouple.&#160; 
	NOTE: Keeping the thermocouple on the rear&#160;side prevents the thermocouple from blocking the sight on the object&#160;by the camera. Therefore, on the one hand, the temperature correction is significantly simpler. On the other hand, thermocouples are usually not positioned on the lower side of the object&#160;during the firing process, thus might lead to operational complications, which is why this alternative needs to be carried out extra carefully.&#160;</li>
	<li>Correct the uncorrected thermography image with respect to the thermocouple measured temperatures with the data generated from steps 2.3 or 2.4.
	<ol>
		<li>Plot the measured temperatures via thermocouples against the determined temperatures via uncorrected IR thermography. Conduct a curve fitting.</li>
		<li>Apply the obtained curve fit as a general uniform global correction formula for the uncorrected thermography image.</li>
	</ol>
	</li>
	<li>Repeat the temperature correction for each new object type or configuration, especially when the optical parameters differ.</li>
</ol>
3. Evaluation of spatial surface temperature distribution via IR thermography
NOTE: The firing conditions are assumed to be identical for this section.
<ol>
	<li>Creation of a two-dimensional peak temperature distribution map (see Figure 4A)
	<ol>
		<li>Write a script with an appropriate programing language to track the surface object temperature for each object surface spot along the entire camera FOV, i.e. acting as a &#34;virtual thermocouple&#34; placed at all object&#160;spots simultaneously. 
		NOTE: Here, the script is written in MATLAB.</li>
		<li>Extract the maximum value, i.e. the peak temperature, for each object spot and plot these temperatures in a corresponding 2D distribution map.</li>
	</ol>
	</li>
	<li>Average temperature distribution in and perpendicular to the object throughput direction (see Figure 4B)
	<ol>
		<li>In throughput direction: average the 2D temperature distribution in the dimension which is opposite to the throughput direction. What remains, is the average 1D temperature distribution in throughput direction.</li>
		<li>Perpendicular to the throughput direction: average the 2D temperature distribution in the dimension which is in throughput direction. What remains, is the average 1D temperature distribution perpendicular&#160;to the throughput direction. 
		NOTE: It is recommended to leave out the last centimeter (at least) of the edge for the averaging since optical artifacts at the object edge might falsify the resulting temperature average.</li>
	</ol>
	</li>
</ol>

<ol><li>Xu, J., Zhang, J., Kuang, K. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aXu%2C+J+%22Conveyor+Belt+Furnace+Thermal+Processing%22">Conveyor Belt Furnace Thermal Processing</a>. , Springer. Heidelberg, Germany. (2018).</li>
<li>Breitenstein, O., Warta, M. W. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aBreitenstein%2C+O+%22Langenkamp+Lock-in+Thermography%3A+Basics+and+Use+for+Evaluating+Electronic+Devices+and+Materials%22">Langenkamp Lock-in Thermography: Basics and Use for Evaluating Electronic Devices and Materials</a>. , Springer. Heidelberg, Germany. (2010).</li>
<li>Ravindra, N. M., Ravindra, K., Mahendra, S., Sopori, B., Fiory, A. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Modeling+and+Simulation+of+Emissivity+of+Silicon-Related+Materials+and+Structures%5BTitle%5D)+AND+%22Journal+of+Electronic+Materials%22%5BJournal%5D)">Modeling and Simulation of Emissivity of Silicon-Related Materials and Structures.</a> Journal of Electronic Materials. 32 (10), 1052-1058 (2003).</li>
<li>Ourinson, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((In+Situ+Solar+Wafer+Temperature+Measurement+during+Firing+Process+via+Inline+IR+Thermography%5BTitle%5D)+AND+%22Physica+Status+Solidi+%28RRL%29+-+Rapid+Research+Letters%22%5BJournal%5D)">In Situ Solar Wafer Temperature Measurement during Firing Process via Inline IR Thermography.</a> Physica Status Solidi (RRL) - Rapid Research Letters. 13 (10), 1900270(2019).</li>
<li>Ourinson, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((In-situ+wafer+temperature+measurement+during+firing+process+via+inline+infrared+thermography%5BTitle%5D)+AND+%22AIP+Conference+Proceedings%22%5BJournal%5D)">In-situ wafer temperature measurement during firing process via inline infrared thermography.</a> AIP Conference Proceedings. 2156, 020013(2019).</li>
<li>Cooper, I. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Understanding+and+Use+of+IR+Belt+Furnace+for+Rapid+Thermal+Firing+of+Screen-Printed+Contacts+to+Si+Solar+Cells%5BTitle%5D)+AND+%22IEEE+Electron+Device+Letters%22%5BJournal%5D)">Understanding and Use of IR Belt Furnace for Rapid Thermal Firing of Screen-Printed Contacts to Si Solar Cells.</a> IEEE Electron Device Letters. 31 (5), 461-463 (2010).</li>
<li>Schubert, G., Huster, F., Fath, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Physical+understanding+of+printed+thick-film+front+contacts+of+crystalline+Si+solar+cells-Review+of+existing+models+and+recent+developments%5BTitle%5D)+AND+%22Solar+Energy+Materials+and+Solar+Cells%22%5BJournal%5D)">Physical understanding of printed thick-film front contacts of crystalline Si solar cells-Review of existing models and recent developments.</a> Solar Energy Materials and Solar Cells. 90 (18-19), 3399-3406 (2006).</li>
<li>Rauer, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Aluminum+Alloying+in+Local+Contact+Areas+on+Dielectrically+Passivated+Rear+Surfaces+of+Silicon+Solar+Cells%5BTitle%5D)+AND+%22IEEE+Electron+Device+Letters%22%5BJournal%5D)">Aluminum Alloying in Local Contact Areas on Dielectrically Passivated Rear Surfaces of Silicon Solar Cells.</a> IEEE Electron Device Letters. 32 (7), 916-918 (2011).</li>
<li>Pawlik, M., Vilcot, J. -P., Halbwax, M., Gauthier, M., Le Quang, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Impact+of+the+firing+step+on+Al+2+O+3+passivation+on+p-type+Czochralski+Si+wafers%3A+Electrical+and+chemical+approaches%5BTitle%5D)+AND+%22Japanese+Journal+of+Applied+Physics%22%5BJournal%5D)">Impact of the firing step on Al 2 O 3 passivation on p-type Czochralski Si wafers: Electrical and chemical approaches.</a> Japanese Journal of Applied Physics. 54 (8), 21(2015).</li>
<li>Lee, B. J., Zhang, Z. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((RAD-PRO%3A+Effective+Software+for+Modeling+Radiative+Properties+in+Rapid+Thermal+Processing%5BTitle%5D)+AND+%222005+13th+International+Conference+on+Advanced+Thermal+Processing+of+Semiconductors%22%5BJournal%5D)">RAD-PRO: Effective Software for Modeling Radiative Properties in Rapid Thermal Processing.</a> 2005 13th International Conference on Advanced Thermal Processing of Semiconductors. , Santa Barbara, CA. (2005).</li>
<li>Temperature Measurements. , Available from: 
 <a target="_blank" href="https://meettechniek.info/measuring/temperature.html">https://meettechniek.info/measuring/temperature.html</a> (2020).</li>
<li>Blakers, A. W., Wang, A., Milne, A. M., Zhao, J., Green, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((22.8%25+efficient+silicon+solar+cell%5BTitle%5D)+AND+%22Applied+Physics+Letters%22%5BJournal%5D)">22.8% efficient silicon solar cell.</a> Applied Physics Letters. 55 (13), 1363-1365 (1989).</li>
<li>Dullweber, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((PERC%2B%3A+industrial+PERC+solar+cells+with+rear+Al+grid+enabling+bifaciality+and+reduced+Al+paste+consumption%5BTitle%5D)+AND+%22Progress+in+Photovoltaics%3A+Research+and+Applications%22%5BJournal%5D)">PERC+: industrial PERC solar cells with rear Al grid enabling bifaciality and reduced Al paste consumption.</a> Progress in Photovoltaics: Research and Applications. 24 (12), 1487-1498 (2016).</li>
<li>Ourinson, D., Emanuel, G., Lorenz, A., Clement, F., Glunz, S. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Evaluation+of+the+burnout+phase+of+the+contact+firing+process+for+industrial+PERC%5BTitle%5D)+AND+%22AIP+Conference+Proceedings%22%5BJournal%5D)">Evaluation of the burnout phase of the contact firing process for industrial PERC.</a> AIP Conference Proceedings. 2147 (1), 040015(2019).</li>
</ol>

The authors have nothing to disclose.

Commonly, thermography temperature is corrected via measuring and adapting the optical parameters of the object, transmissive window and path, and environmental temperature of the object and transmissive window2. As an alternative method, a temperature correction technique based on thermocouple measurements is described in this protocol. For the latter method, knowledge of the parameters mentioned above is not required. For the application shown here, this method is sufficient. However, it cannot ...

Process control and quality assurance of objects processed in conveyor belt furnaces1 is important and accomplished by measuring the surface temperature of the object. Currently, the temperature is typically measured by a thermocouple1. As thermocouple measurements require contact with the object, thermocouples inevitably damage the object. Therefore, it is common to choose representative samples of a batch for temperature measurements, which are not further processed since they become damaged. The measured temperatures of these damaged objects are then generalized to the remaining samples from the batch, which are further processed. Accordingly, production must be interrupted for thermocouple measurements. Furthermore, the contact is local, needs to be readjusted after each measurement, and influences the local temperature.
Infrared (IR) thermography2 has a number of advantages over classic thermocouple measurements and represents a contactless, in-situ, real-time, time-saving, and spatially resolved temperature measurement method. Using this method, each sample of the batch, including those that are further processed, can be measured without interrupting production. In addition, the surface temperature distribution can be measured, which provides insight into temperature homogeneity during the process. The real-time feature allows correction of temperature settings on-the-fly. So far, the possible reasons for not using IR thermography in conveyor belt furnaces are 1) unknown optical parameters of hot objects (especially for nonmetals3) and 2) parasitic environmental radiation in the furnace (i.e., reflected radiation detected by the IR camera in addition to the emitted radiation from the object), which leads to false temperature output2.
Here, as a representative proof-of-concept example of IR thermography in a conveyor belt furnace, we successfully installed an inline thermography system into an IR lamp powered solar firing furnace (Figure 1), which is used during the contact firing process of industrial Si solar cells (Figure 2A,B)4,5. The firing process is a crucial step at the end of industrial solar cell production6. During this step, the contacts of the cell are formed7,8, and surface passivation is activated9. To successfully achieve the latter, the time-temperature profile during the firing process (Figure 2C) must be accurately realized. Therefore, sufficient and efficient temperature control is required. This protocol describes how to install an IR camera into a conveyor belt furnace, conduct a customer correction of a factory calibrated IR camera, and evaluate the spatial surface temperature distribution of a target object.

<table><tbody><tr><td>Datalogger incl. Thermal barrier</td><td>Datapaq Ltd.</td><td></td><td></td></tr><tr><td>IR thermography camera &quot;Image IR 8300&quot;</td><td>InfraTec GmbH</td><td></td><td></td></tr><tr><td>IR thermography software &quot;IRBIS Professional 3.1&quot;</td><td>InfraTec GmbH</td><td></td><td></td></tr><tr><td>Solar cells</td><td>Fraunhofer ISE</td><td></td><td></td></tr><tr><td>Solar firing furnace &quot;RFS 250 Plus&quot;</td><td>Rehm Thermal Systems GmbH</td><td></td><td></td></tr><tr><td>Sheath thermocouples type K</td><td>TMH GmbH</td><td></td><td></td></tr><tr><td>Thermocouple quartzframe</td><td>Heraeus Noblelight GmbH</td><td></td><td></td></tr></tbody></table>

in situ surface temperature measurement in a conveyor belt furnace via inline infrared thermography

Measuring the surface temperature of objects that are processed in conveyor belt furnaces is an important tool in process control and quality assurance. Currently, the surface temperature of objects processed in conveyor belt furnaces is typically measured via thermocouples. However, infrared (IR) thermography presents multiple advantages compared to thermocouple measurements, as it is a contactless, real-time, and spatially resolved method. Here, as a representative proof-of-concept example, an inline thermography system is successfully installed into an IR lamp powered solar firing furnace, which is used for the contact firing process of industrial Si solar cells. This protocol describes how to install an IR camera into a conveyor belt furnace, conduct a customer correction of a factory calibrated IR camera, and perform the evaluation of spatial surface temperature distribution on a target object.

As shown in Figure 3B&#8722;D, the example object (here, a silicon solar cell; strictly speaking, a passivated emitter and rear cell [PERC]12; Figure 2A,B) can be clearly detected by the IR camera in different configurations4. The different configurations are monofacially metallized (Figure 3B), bifacially metallized13 (<strong ...

Watch this Scientific Journal Video about In Situ Surface Temperature Measurement in a Conveyor Belt Furnace via Inline Infrared Thermography at JoVE.com

In Situ Surface Temperature Measurement in a Conveyor Belt Furnace via Inline Infrared Thermography

This protocol describes how to install an infrared camera into a conveyor belt furnace, conduct a customer correction of a factory calibrated IR camera, and evaluate the spatial surface temperature distribution of an object of interest. The example objects are industrial silicon solar cells.

Measuring the surface temperature of objects that are processed in conveyor belt furnaces is an important tool in process control and quality assurance. ...

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JoVE Journal

Engineering

4.4K Views.  Fraunhofer Institute for Solar Energy Systems ISE. Omdat het cruciaal is om de temperatuur van de objecten verwerkt in inline ovens te meten, presenteren we hier inline thermografie als een veelbelovend alternatief voor klassieke temperatuurmetingen door thermokoppels. Thermokoppels beschadigen het object, meten de temperatuur lokaal en vereisen een productieonderbreking. Onze inline thermografiecamera meet echter de objecttemperatuur op een contactloze, real-time, ruimtelijk opgeloste manier.We gebruiken inline ovens voor contact bakk...

Video: In Situ Surface Temperature Measurement in a Conveyor Belt Furnace via Inline Infrared Thermography

Quantitative Visualization and Detection of Skin Cancer Using Dynamic Thermal Imaging

In 2010 approximately 68,720 melanomas will be diagnosed in the US alone, with around 8,650 resulting in death 1. To date, the only effective treatment for melanoma remains surgical excision, therefore, the key to extended survival is early detection 2,3. Considering the large numbers of patients diagnosed every year and the limitations in accessing specialized care quickly, the development of objective in vivo diagnostic instruments to aid the diagnosis is essential. New techniques to detect skin cancer, especially non-invasive diagnostic tools, are being explored in numerous laboratories. Along with the surgical methods, techniques such as digital photography, dermoscopy, multispectral imaging systems (MelaFind), laser-based systems (confocal scanning laser microscopy, laser doppler perfusion imaging, optical coherence tomography), ultrasound, magnetic resonance imaging, are being tested. Each technique offers unique advantages and disadvantages, many of which pose a compromise between effectiveness and accuracy versus ease of use and cost considerations. Details about these techniques and comparisons are available in the literature 4.
Infrared (IR) imaging was shown to be a useful method to diagnose the signs of certain diseases by measuring the local skin temperature. There is a large body of evidence showing that disease or deviation from normal functioning are accompanied by changes of the temperature of the body, which again affect the temperature of the skin 5,6. Accurate data about the temperature of the human body and skin can provide a wealth of information on the processes responsible for heat generation and thermoregulation, in particular the deviation from normal conditions, often caused by disease. However, IR imaging has not been widely recognized in medicine due to the premature use of the technology 7,8 several decades ago, when temperature measurement accuracy and the spatial resolution were inadequate and sophisticated image processing tools were unavailable. This situation changed dramatically in the late 1990s-2000s. Advances in IR instrumentation, implementation of digital image processing algorithms and dynamic IR imaging, which enables scientists to analyze not only the spatial, but also the temporal thermal behavior of the skin 9, allowed breakthroughs in the field.
In our research, we explore the feasibility of IR imaging, combined with theoretical and experimental studies, as a cost effective, non-invasive, in vivo optical measurement technique for tumor detection, with emphasis on the screening and early detection of melanoma 10-13. In this study, we show data obtained in a patient study in which patients that possess a pigmented lesion with a clinical indication for biopsy are selected for imaging. We compared the difference in thermal responses between healthy and malignant tissue and compared our data with biopsy results. We concluded that the increased metabolic activity of the melanoma lesion can be detected by dynamic infrared imaging.

We demonstrated that malignant pigmented lesions with increased metabolic activity generate quantifiable amounts of heat and the measurement of the transient thermal response of the skin to a cooling excitation allows quantitative identification of melanoma and other skin cancers (vs. non-proliferative nevi) at an early stage of the disease.

In 2010 approximately 68,720 melanomas will be diagnosed in the US alone, with around 8,650 resulting in death 1. To date, the only effective treatment ...

Medicine

High-resolution Thermal Micro-imaging Using Europium Chelate Luminescent Coatings

Micro-electronic devices often undergo significant self-heating when biased to their typical operating conditions. This paper describes a convenient optical micro-imaging technique which can be used to map and quantify such behavior. Europium thenoyltrifluoroacetonate (EuTFC) has a 612 nm luminescence line whose activation efficiency drops strongly with increasing temperature, due to T-dependent interactions between the Eu3+ ion and the organic chelating compound. This material may be readily coated on to a sample surface by thermal sublimation in vacuum. When the coating is excited with ultraviolet light (337 nm) an optical micro-image of the 612 nm luminescent response can be converted directly into a map of the sample surface temperature. This technique offers spatial resolution limited only by the microscope optics (about 1 micron) and time resolution limited by the speed of the camera employed. It offers the additional advantages of only requiring comparatively simple and non-specialized equipment, and giving a quantitative probe of sample temperature.

Europium thenoyltrifluoroacetonate (EuTFC) has an optical luminescence line at 612 nm, whose activation efficiency decreases strongly with temperature. If a sample coated with a thin film of this material is micro-imaged, the 612 nm luminescent response intensity may be converted into a direct map of sample surface temperature.

Micro-electronic devices often undergo significant self-heating when biased to their typical operating conditions. This paper describes a convenient ...

Fiber Optic Distributed Sensors for High-resolution Temperature Field Mapping

The reliability of computational fluid dynamics (CFD) codes is checked by comparing simulations with experimental data. A typical data set consists chiefly of velocity and temperature readings, both ideally having high spatial and temporal resolution to facilitate rigorous code validation. While high resolution velocity data is readily obtained through optical measurement techniques such as particle image velocimetry, it has proven difficult to obtain temperature data with similar resolution. Traditional sensors such as thermocouples cannot fill this role, but the recent development of distributed sensing based on Rayleigh scattering and swept-wave interferometry offers resolution suitable for CFD code validation work. Thousands of temperature measurements can be generated along a single thin optical fiber at hundreds of Hertz. Sensors function over large temperature ranges and within opaque fluids where optical techniques are unsuitable. But this type of sensor is sensitive to strain and humidity as well as temperature and so accuracy is affected by handling, vibration, and shifts in relative humidity. Such behavior is quite unlike traditional sensors and so unconventional installation and operating procedures are necessary to ensure accurate measurements. This paper demonstrates implementation of a Rayleigh scattering-type distributed temperature sensor in a thermal mixing experiment involving two air jets at 25 and 45 &#176;C. We present criteria to guide selection of optical fiber for the sensor and describe installation setup for a jet mixing experiment. We illustrate sensor baselining, which links readings to an absolute temperature standard, and discuss practical issues such as errors due to flow-induced vibration. This material can aid those interested in temperature measurements having high data density and bandwidth for fluid dynamics experiments and similar applications. We highlight pitfalls specific to these sensors for consideration in experiment design and operation.

We demonstrate use of a fiber optic distributed sensor for mapping the temperature field of mixing air jets. The Rayleigh scattering-based sensor generates thousands of data points along a single fiber to provide exceptional spatial resolution that is unattainable with traditional sensors such as thermocouples.

The reliability of computational fluid dynamics (CFD) codes is checked by comparing simulations with experimental data. A typical data set consists ...

Subsurface Defect Localization by Structured Heating Using Laser Projected Photothermal Thermography

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering thermal wave fields that are disturbed by the defect. This effect is measured and used to locate the defect. We form the destructively interfering wave fields by using a modified projector. The original light engine of the projector is replaced with a fiber-coupled high-power diode laser. Its beam is shaped and aligned to the projector&#39;s spatial light modulator and optimized for optimal optical throughput and homogeneous projection by first characterizing the beam profile, and, second, correcting it mechanically and numerically. A high-performance infrared (IR) camera is set up according to the tight geometrical situation (including corrections of the geometrical image distortions) and the requirement to detect weak temperature oscillations at the sample surface. Data acquisition can be performed once a synchronization between the individual thermal wave field sources, the scanning stage, and the IR camera is established by using a dedicated experimental setup which needs to be tuned to the specific material being investigated. During data post-processing, the relevant information on the presence of a defect below the surface of the sample is extracted. It is retrieved from the oscillating part of the acquired thermal radiation coming from the so-called depletion line of the sample surface. The exact location of the defect is deduced from the analysis of the spatial-temporal shape of these oscillations in a final step. The method is reference-free and very sensitive to changes within the thermal wave field. So far, the method has been tested with steel samples but is applicable to different materials as well, in particular to temperature sensitive materials.

This method aims at locating vertical subsurface defects. Here, we couple a laser with a spatial light modulator and trigger its video input to heat a sample surface deterministically with two anti-phased modulated lines while acquiring highly resolved thermal images. The defect position is retrieved from evaluating thermal wave interference minima.

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering ...

Near-Infrared Temperature Measurement Technique for Water Surrounding an Induction-heated Small Magnetic Sphere

A technique to measure the temperature of water and non-turbid aqueous media surrounding an induction-heated small magnetic sphere is presented. This technique utilizes wavelengths of 1150 and 1412 nm, at which the absorption coefficient of water is dependent on temperature. Water or a non-turbid aqueous gel containing a 2.0-mm- or 0.5-mm-diameter magnetic sphere is irradiated with 1150 nm or 1412 nm incident light, as selected using a narrow bandpass filter; additionally, two-dimensional absorbance images, which are the transverse projections of the absorption coefficient, are acquired via a near-infrared camera. When the three-dimensional distributions of temperature can be assumed to be spherically symmetric, they are estimated by applying inverse Abel transforms to the absorbance profiles. The temperatures were observed to consistently change according to time and the induction heating power.

A technique utilizing wavelengths of 1150 and 1412 nm to measure the temperature of water surrounding an induction-heated small magnetic sphere is presented.

A technique to measure the temperature of water and non-turbid aqueous media surrounding an induction-heated small magnetic sphere is presented. This ...

Measurements of Local Instantaneous Convective Heat Transfer in a Pipe - Single and Two-phase Flow

This manuscript provides step by step description of the manufacturing process of a test section designed to measure the local instantaneous heat transfer coefficient as a function of the liquid flow rate in a transparent pipe. With certain amendments, the approach is extended to gas-liquid flows, with a particular emphasis on the effect of a single elongated (Taylor) air bubble on heat transfer enhancement. A non-invasive thermography technique is applied to measure the instantaneous temperature of a thin metal foil heated electrically. The foil is glued to cover a narrow slot cut in the pipe. The thermal inertia of the foil is small enough to detect the variation in the instantaneous foil temperature. The test section can be moved along the pipe and is long enough to cover a considerable part of the growing thermal boundary layer.
At the beginning of each experimental run, a steady state with a constant water flow rate and heat flux to the foil is attained and serves as the reference. The Taylor bubble is then injected into the pipe. The heat transfer coefficient variations due to the passage of a Taylor bubble propagating in a vertical pipe is measured as function of the distance of the measuring point from the bottom of the moving Taylor bubble. Thus, the results represent the local heat transfer coefficients. Multiple independent runs preformed under identical conditions allow accumulating sufficient data to calculate reliable ensemble-averaged results on the transient convective heat transfer. In order to perform this in a frame of reference moving with the bubble, the location of the bubble along the pipe has to be known at all times. Detailed description of measurements of the length and of the translational velocity of the Taylor bubbles by optical probes is presented.

This manuscript describes methods aimed at measuring the local instantaneous convective heat transfer coefficients in a single or two-phase pipe flow. A simple optical method to determine the length and the propagation velocity of an elongated (Taylor) air bubble moving at a constant velocity is also presented.

This manuscript provides step by step description of the manufacturing process of a test section designed to measure the local instantaneous heat transfer ...

Fabrication of Microscope Stage for Vertical Observation with Temperature Control Function

Samples are usually placed onto a horizontal microscope stage for microscopic observation. However, to observe the influence of gravity on a sample or study afloat behavior, it is necessary to make the microscope stage vertical. To accomplish this, a sideways inverted microscope tilted by 90&#176; has been devised. To observe samples with this microscope, sample containers such as Petri dishes or glass slides must be secured to the stage vertically. A device that can secure sample containers in place on a vertical microscope stage has been developed and is described here. Attachment of this device to the stage allows observation of sample dynamics in the vertical plane. The ability to regulate temperature using a silicone rubber heater also permits observation of temperature-dependent sample behaviors. Furthermore, the temperature data is transferred to an internet server. Temperature settings and log monitoring can be controlled remotely from a PC or smartphone.

Presented here is a protocol using a temperature-controlled microscope stage that allows a sample container to be mounted on a vertical microscope.

Samples are usually placed onto a horizontal microscope stage for microscopic observation. However, to observe the influence of gravity on a sample or ...

Design, Instrumentation and Usage Protocols for Distributed In Situ Thermal Hot Spots Monitoring in Electric Coils using FBG Sensor Multiplexing

Random wound coils are a key operational element of most electric apparatus in modern industrial systems, including low voltage electric machines. One of the major current bottlenecks in improved exploitation of electrical devices is the high sensitivity of their wound components to in-service thermal stress. The application of conventional thermal sensing methods (e.g., thermocouples, resistance temperature detectors) for thermal condition monitoring of current carrying random wound coils can impose considerable operational limitations due to sensor size, EMI sensitivity and the existence of electrically conductive material in their construction. Another substantial limitation exists in distributed sensing applications and is caused by what is often a considerable length and volume of conventional sensor wiring leads.
This paper reports the design of a fiber optic FBG&#160;sensing system&#160;intended for enabling real-time distributed internal thermal&#160;condition monitoring within random wound coils. The procedure of random wound coil instrumentation with the FBG sensing system is reported in a case study on an IEEE standard wound coil representative of those utilized in electrical machines. The reported work also presents and discusses important practical and technical aspects of FBG sensing system implementation and application, including the FBG array geometry design, sensing head and fiber packaging, the sensor array installation and calibration procedure and the use of a commercial interrogation system for obtaining thermal measurements. Finally, the in situ multiplexed FBG sensing system thermal monitoring performance is demonstrated in representative static and dynamic thermal conditions.&#160;

This paper presents a protocol that enables instrumentation of random wound electric coils with fiber Bragg grating (FBG) thermal sensors for the purpose of distributed condition monitoring of internal thermal hot spots.

Random wound coils are a key operational element of most electric apparatus in modern industrial systems, including low voltage electric machines. One of ...

Production of CdSe&#45;SnSe Nanocomposites from Consolidated SnSe Particles

Solution&#45;Processed, Surface&#45;Engineered, Polycrystalline CdSe&#45;SnSe Exhibiting Low Thermal Conductivity

In recent years, solution processes have gained considerable traction as a cost-effective and scalable method to produce high-performance thermoelectric materials. The process entails a series of critical steps: synthesis, purification, thermal treatments, and consolidation, each playing a pivotal role in determining performance, stability, and reproducibility. We have noticed a need for more comprehensive details for each of the described steps in most published works. Recognizing the significance of detailed synthetic protocols, we describe here the approach used to synthesize and characterize one of the highest-performing polycrystalline p-type SnSe. In particular, we report the synthesis of SnSe particles in water and the subsequent surface treatment with CdSe molecular complexes that yields CdSe-SnSe nanocomposites upon consolidation. Moreover, the surface treatment inhibits grain growth through Zenner pinning of secondary phase CdSe nanoparticles and enhances defect formation at different length scales. The enhanced complexity in the CdSe-SnSe nanocomposite microstructure with respect to SnSe promotes phonon scattering and thereby significantly reduces the thermal conductivity. Such surface engineering provides opportunities in solution processing for introducing and controlling defects, making it possible to optimize the transport properties and attain a high thermoelectric figure of merit.

Author Spotlight: Advancing Energy Solutions Using Nanocomposites as Processed Thermoelectric Materials

CdSe-SnSe nanocomposites are produced by consolidating surface-engineered SnSe particles. A simple aqueous synthesis is employed to produce SnSe particles. Coating SnSe particles with CdSe molecular complexes allows for controlling grain size and increasing the number of defects present in the nanocomposite, thus lowering the thermal conductivity.

In recent years, solution processes have gained considerable traction as a cost-effective and scalable method to produce high-performance thermoelectric ...

Chemistry

Synthesis of High-ZT Thermoelectric Materials via Mechanochemical Methods

Demonstrating the Simplicity and In Situ Temperature Monitoring of the Mechanochemical Synthesis of Metal Chalcogenides Suitable for Thermoelectrics

Mechanochemical synthesis is an extremely useful strategy to reach thermoelectric materials due to its solvent-free one-step character, as the targeted thermoelectricity (TE) materials in a nanocrystalline format can be prepared by mere high-energy milling of elemental precursors. Nevertheless, the subsequent densification method (e.g., spark plasma sintering or hot pressing) is required afterward, similarly to other synthetic methodologies. In this study, the simplicity of mechanochemical synthesis is&#160;presented for two selected metal chalcogenides, namely copper sulfide (Cu1.8S, digenite) and tin selenide (SnSe, svetlanaite), which are known for high ZT values. These compounds can be prepared via a mechanically induced self-propagating reaction (MSR), which is a combustion-like process instantly yielding the products in a very short timeframe (within 1 min). The occurrence of MSR can be well-tracked by in situ temperature monitoring since an abrupt temperature increase occurs at the moment of MSR. We have developed a device which is capable of monitoring the temperature inside the milling jar every 80 ms during planetary ball milling, and it is therefore possible to very precisely track the moment of MSR ignition. The developed device presents an improvement in the monitoring capabilities in comparison with commercially available analogs. This contribution aims to provide a visual insight into all steps, with simple high-energy ball milling of elements to reach TE materials and in situ temperature monitoring being the central points.

Here, we present a protocol to synthesize two metal chalcogenides (Cu1.8S and SnSe) suitable for thermoelectrics via an ultrafast (second-range), solvent-free, and one-step mechanochemical synthesis using elemental precursors. Simultaneously, we demonstrate the monitoring of the temperature in the jar during planetary ball milling in situ by the newly developed device.

Mechanochemical synthesis is an extremely useful strategy to reach thermoelectric materials due to its solvent-free one-step character, as the targeted ...

In Situ Surface Temperature Measurement in a Conveyor Belt Furnace via Inline Infrared Thermography

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