Name: in situ surface temperature measurement in a conveyor belt furnace via inline infrared thermography
Uploaded: 2020-05-30T13:00:00
Description: Watch this Scientific Journal Video about In Situ Surface Temperature Measurement in a Conveyor Belt Furnace via Inline Infrared Thermography at JoVE.com

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 e...

<ol>
	<li>Xu, J., Zhang, J., Kuang, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Conveyor Belt Furnace Thermal Processing. , (2018).</li><li>Breitenstein, O., Warta, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Langenkamp Lock-in Thermography: Basics and Use for Evaluating Electronic Devices and Materials. , (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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+and+Simulation+of+Emissivity+of+Silicon-Related+Materials+and+Structures.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+Situ+Solar+Wafer+Temperature+Measurement+during+Firing+Process+via+Inline+IR+Thermography.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In-situ+wafer+temperature+measurement+during+firing+process+via+inline+infrared+thermography.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Understanding+and+Use+of+IR+Belt+Furnace+for+Rapid+Thermal+Firing+of+Screen-Printed+Contacts+to+Si+Solar+Cells.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physical+understanding+of+printed+thick-film+front+contacts+of+crystalline+Si+solar+cells-Review+of+existing+models+and+recent+developments.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aluminum+Alloying+in+Local+Contact+Areas+on+Dielectrically+Passivated+Rear+Surfaces+of+Silicon+Solar+Cells.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+the+firing+step+on+Al+2+O+3+passivation+on+p-type+Czochralski+Si+wafers:+Electrical+and+chemical+approaches.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RAD-PRO:+Effective+Software+for+Modeling+Radiative+Properties+in+Rapid+Thermal+Processing.">RAD-PRO: Effective Software for Modeling Radiative Properties in Rapid Thermal Processing.</a> 2005 13th International Conference on Advanced Thermal Processing of Semiconductors. , (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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=22.8%+efficient+silicon+solar+cell.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PERC+:+industrial+PERC+solar+cells+with+rear+Al+grid+enabling+bifaciality+and+reduced+Al+paste+consumption.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+the+burnout+phase+of+the+contact+firing+process+for+industrial+PERC.">Evaluation of the burnout phase of the contact firing process for industrial PERC.</a> AIP Conference Proceedings. 2147 (1), 040015 (2019).</li></ol>

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 border="0" cellpadding="0" cellspacing="0" style="width:665px;" width="665">
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		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Datalogger incl. Thermal barrier</td>
			<td style="width:121px;">Datapaq Ltd.</td>
			<td style="width:161px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">IR thermography camera &#34;Image IR 8300&#34;</td>
			<td style="width:121px;">InfraTec GmbH</td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">IR thermography software &#34;IRBIS Professional 3.1&#34;</td>
			<td style="width:121px;">InfraTec GmbH</td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Solar cells</td>
			<td style="width:121px;">Fraunhofer ISE</td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Solar firing furnace &#34;RFS 250 Plus&#34;</td>
			<td style="width:121px;">Rehm Thermal Systems GmbH</td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sheath thermocouples type K</td>
			<td style="width:121px;">TMH GmbH</td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Thermocouple quartzframe</td>
			<td style="width:121px;">Heraeus Noblelight GmbH</td>
			<td style="width:161px;"></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. ...

As it is crucial to measure the temperature of the objects processed in inline furnaces, here we present inline thermography as a promising alternative to classic temperature measurements by thermocouples. Thermocouples damage the object, measure the temperature locally, and require a production interruption. Our inline thermography camera however, measures the object temperature in a contactless, real-time, spatially-resolved manner.We use inline furnaces for contact firing of silicon solar cells. Therefore, we installed a thermography camera inline into our furnace to investigate these advantages. Select a camera with a detection wavelength range that matches the wavelength range of the highest emission of the object of interest in the temperature range of interest as much as possible.To install the camera outside of the furnace chamber, remove the furnace wall and isolation at the location where the optical path should be located, avoiding disturbing objects, such as infrared lamps, in the optical path. Close the hole with a window that isolates the furnace chamber thermally while being as transparent as possible for the detection wavelength range of the camera. Then, place the camera above the windows so that the camera has a visual on the moving belt.Avoid as much parasitic radiation detection by the camera as possible by avoiding nearby objects that emit or reflect radiation in the detection wavelength range of the camera. Then, examine the thermography image via the infrared camera software to check the resulting field of view of the camera. For a customer temperature correction for Silicon solar cells, first check the solar cell for local optical artifacts.As the temperature correction is based on thermocouples, to check the thermocouple validity, mount the thermocouple on the rear aluminum side of the wafer, and measure the time temperature profile for a standard firing process. If the time temperature profile shows a disruption in the form of a flatter curve at the aluminum silicon eutectic temperature of 577 degrees Celsius, the thermocouple is most likely correctly calibrated. Conduct thermocouple measurements with the validated thermocouple mounted on the rear side of the solar cell, and record the wafer with the infrared camera.Conduct multiple thermocouple measurements in the temperature range of interest at the same object spot and at spatially various random object spots to obtain statistically significant time temperature profiles. To determine the local uncorrected thermography solar cell temperature under the thermocouple, extract the local temperature at the position of the thermocouple. Log the measured temperatures via thermocouples against the determined temperatures via uncorrected infrared thermography, and obtain a curve fit as a general uniform global correction formula for the uncorrected thermography image.Then use this curve fit data to correct the uncorrected thermography image globally. To create a two-dimensional peak temperature distribution map, write a script in an appropriate programming language to track the surface temperature for each object's surface spot along the entire camera field of view to act as a virtual thermocouple placed at all of the wafer spots simultaneously. Then, extract the peak temperature value for each spot, and plot these temperatures in a corresponding 2D distribution map.To perform an average temperature distribution in the throughput direction, average the 2D temperature distribution in the dimension perpendicular to the throughput direction. To perform an average temperature distribution perpendicular to the throughput direction, average the 2D temperature distribution in the dimension in the throughput direction. As demonstrated in this figure, the corrected temperature of this Silicon solar cell can be clearly detected by the infrared camera in different configurations.Monofacially metalized, bifacially metalized, and non-metalized perk samples. In these analyses, the temperature range of interest resembled the typical peak temperature range of the firing process. As observed in this image, the contacting thermocouple on the rear side of the solar cell causes a temperature drop around itself, most likely due to heat dissipation and shading.The latter drop is important for estimating the cell temperature during firing without thermocouples, compared to the temperature measured by the thermocouple, as for this cell positioned onto a frame when contacted by a thermocouple. If placed directly on the belt, the infrared camera allows observation of the local heat dissipation of the cells by the conveyor belt. This image shows a representative two-dimensional spatial solar cell peak temperature distribution, and the deduced average distribution in and perpendicular to the transport direction.As we use inline furnaces for contact firing of silicon solar cells, we installed an infrared camera into our furnace to create an innovative thermography application. Obtaining spatially resolved peak temperature distributions during the firing process allows the investigation of temperature distribution correlations to the spatially resolved solar cell parameters that are significantly effected by the firing.

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Engineering

In-situ Tapering of Chalcogenide Fiber for Mid-infrared Supercontinuum Generation

Supercontinuum generation (SCG) in a tapered chalcogenide fiber is desirable for broadening mid-infrared (or mid-IR, roughly the 2-20 &mu;m wavelength range) frequency combs1, 2 for applications such as molecular fingerprinting, 3 trace gas detection, 4 laser-driven particle acceleration, 5 and x-ray production via high harmonic generation. 6 Achieving efficient SCG in a tapered optical fiber requires precise control of the group velocity dispersion (GVD) and the temporal properties of the optical pulses at the beginning of the fiber, 7 which depend strongly on the geometry of the taper. 8 Due to variations in the tapering setup and procedure for successive SCG experiments-such as fiber length, tapering environment temperature, or power coupled into the fiber, in-situ spectral monitoring of the SCG is necessary to optimize the output spectrum for a single experiment.
	In-situ fiber tapering for SCG consists of coupling the pump source through the fiber to be tapered to a spectral measurement device. The fiber is then tapered while the spectral measurement signal is observed in real-time. When the signal reaches its peak, the tapering is stopped. The in-situ tapering procedure allows for generation of a stable, octave-spanning, mid-IR frequency comb from the sub harmonic of a commercially available near-IR frequency comb. 9 This method lowers cost due to the reduction in time and materials required to fabricate an optimal taper with a waist length of only 2 mm.
	The in-situ tapering technique can be extended to optimizing microstructured optical fiber (MOF) for SCG10 or tuning of the passband of MOFs, 11 optimizing tapered fiber pairs for fused fiber couplers12 and wavelength division multiplexers (WDMs), 13 or modifying dispersion compensation for compression or stretching of optical pulses.14-16

In-situ Tapering of Chalcogenide Fiber for Mid-infrared Supercontinuum Generation

We describe a method for in-situ tapering of As2S3 fibers to achieve efficient mid-infrared supercontinuum generation. By tapering while monitoring the supercontinuum&#x2019;s spectrum, the spectral width can be maximized for a fiber taper. In-situ fiber tapering can be applied to optimize the performance of other fiber-based devices.

Supercontinuum  generation (SCG) in a tapered chalcogenide fiber is desirable for broadening mid-infrared  (or mid-IR, roughly the 2-20 &mu;m wavelength ...

Fabrication and Operation of a Nano-Optical Conveyor Belt

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological and physical sciences over the past few decades. The progress made in this field invites further study of even smaller systems and at a larger scale, with tools that could be distributed more easily and made more widely available. Unfortunately, the fundamental laws of diffraction limit the minimum size of the focal spot of a laser beam, which makes particles smaller than a half-wavelength in diameter hard to trap and generally prevents an operator from discriminating between particles which are closer together than one half-wavelength. This precludes the optical manipulation of many closely-spaced nanoparticles and&#160;limits the&#160;resolution of optical-mechanical systems. Furthermore, manipulation using focused beams requires beam-forming or steering optics, which can be very bulky and expensive. To address these limitations in the system scalability of conventional optical trapping our lab has devised an alternative technique which utilizes near-field optics to move particles across a chip. Instead of focusing laser beams in the far-field, the optical near field of plasmonic resonators produces the necessary local optical intensity enhancement to overcome the restrictions of diffraction and manipulate particles at higher resolution. Closely-spaced resonators produce strong optical traps which can be addressed to mediate the hand-off of particles from one to the next in a conveyor-belt-like fashion. Here, we describe how to design and produce a conveyor belt using a gold surface patterned with plasmonic C-shaped resonators and how to operate it with polarized laser light to achieve super-resolution nanoparticle manipulation and transport. The nano-optical conveyor belt chip can be produced using lithography techniques and easily packaged and distributed.

The scalability and resolution of conventional optical manipulation techniques are limited by diffraction. We circumvent the diffraction limit and describe a method of optically transporting nanoparticles across a chip using a gold surface patterned with a path of closely spaced C-shaped plasmonic resonators.

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

The Measurement of Unsteady Surface Pressure Using a Remote Microphone Probe

Microphones are widely applied to measure pressure fluctuations at the walls of solid bodies immersed in turbulent flows. Turbulent motions with various characteristic length scales can result in pressure fluctuations over a wide frequency range. This property of turbulence requires sensing devices to have sufficient sensitivity over a wide range of frequencies. Furthermore, the small characteristic length scales of turbulent structures require small sensing areas and the ability to place the sensors in very close proximity to each other. The complex geometries of the solid bodies, often including large surface curvatures or discontinuities, require the probe to have the ability to be set up in very limited spaces. The development of a remote microphone probe, which is inexpensive, consistent, and repeatable, is described in the present communication. It allows for the measurement of pressure fluctuations with high spatial resolution and dynamic response over a wide range of frequencies. The probe is small enough to be placed within the interior of typical wind tunnel models. The remote microphone probe includes a small, rigid, and hollow tube that penetrates the model surface to form the sensing area. This tube is connected to a standard microphone, at some distance away from the surface, using a "T" junction. An experimental method is introduced to determine the dynamic response of the remote microphone probe. In addition, an analytical method for determining the dynamic response is described. The analytical method can be applied in the design stage to determine the dimensions and properties of the RMP components.

Here, we present a protocol to measure, with high spatial resolution, the unsteady surface pressure in turbulent flows. This method demonstrates the construction of a remote microphone probe (RMP) and the determination of its frequency-dependent, complex transfer function. An analytical determination of the dynamic response is presented and validated.

Microphones are widely applied to measure pressure fluctuations at the walls of solid bodies immersed in turbulent flows. Turbulent motions with various ...

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

Optical Trap Loading of Dielectric Microparticles In Air

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly scattered dielectric microparticles adhered to a glass substrate are momentarily detached using ultrasonic vibrations generated by a piezoelectric transducer (PZT). Then, the optical beam focused on a selected particle lifts it up to the optical trap while the vibrationally excited microparticles fall back to the substrate. A particle may be trapped at the nominal focus of the trapping beam or at a position above the focus (referred to here as the levitation position) where gravity provides the restoring force. After the measurement, the trapped particle can be placed at a desired position on the substrate in a controlled manner. 
In this protocol, an experimental procedure for selective optical trap loading in air is outlined. First, the experimental setup is briefly introduced. Second, the design and fabrication of a PZT holder and a sample enclosure are illustrated in detail. The optical trap loading of a selected microparticle is then demonstrated with step-by-step instructions including sample preparation, launching into the trap, and use of electrostatic force to excite particle motion in the trap and measure charge. Finally, we present recorded particle trajectories of Brownian and ballistic motions of a trapped microparticle in air. These trajectories can be used to measure stiffness or to verify optical alignment through time domain and frequency domain analysis. Selective trap loading enables optical tweezers to track a particle and its changes over repeated trap loadings in a reversible manner, thereby enabling studies of particle-surface interaction.

A protocol for launching and stably trapping selected dielectric microparticles in air is presented.

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly ...

Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials such as organo-lead halide perovskites is presented. The perovskite film thickness and absorption coefficient are initially characterized by profilometry and UV-VIS absorption spectroscopy. Calibration of both laser power and cavity sensitivity is described in detail. A protocol for performing Flash-photolysis Time Resolved Microwave Conductivity (TRMC) experiments, a non-contact method of determining the conductivity of a material, is presented. A process for identifying the real and imaginary components of the complex conductivity by performing TRMC as a function of microwave frequency is given. Charge carrier dynamics are determined under different excitation regimes (including both power and wavelength). Techniques for distinguishing between direct and trap-mediated decay processes are presented and discussed. Results are modelled and interpreted with reference to a general kinetic model of photoinduced charge carriers in a semiconductor. The techniques described are applicable to a wide range of optoelectronic materials, including organic and inorganic photovoltaic materials, nanoparticles, and conducting/semiconducting thin films.

A Time Resolved Microwave Conductivity technique for investigating direct and trap-mediated recombination dynamics and determining carrier mobilities of thin film semiconductors is presented here.

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials ...

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2&#183;g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

A protocol for fabricating porous, nanostructured yttria-stabilized-zirconia (YSZ) scaffolds at temperatures between 1,000 &#176;C and 1,400 &#176;C is presented.

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...

Preparation and High-temperature Anti-adhesion Behavior of a Slippery Surface on Stainless Steel

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A typical anti-wetting superhydrophobic surface easily fails when exposed to a high-temperature liquid. Recently, Nepenthes-inspired slippery surfaces demonstrated a new way to solve the adhesion problem. A lubricant layer on the slippery surface can act as a barrier between the repelled materials and the surface structure. However, the slippery surfaces in previous studies rarely showed high-temperature resistance. Here, we describe a protocol for the preparation of slippery surfaces with high-temperature resistance. A photolithography-assisted method was used to fabricate pillar structures on stainless steel. By functionalizing the surface with saline, a slippery surface was prepared by adding silicone oil. The prepared slippery surface maintained the anti-wetting property for water, even when the surface was heated to 300 &#176;C. Also, the slippery surface exhibited great anti-adhesion effects on soft tissues at high temperatures. This type of slippery surface on stainless steel has applications in medical devices, mechanical equipment, etc.

Slippery surfaces provide a new way to solve the adhesion problem. This protocol describes how to fabricate slippery surfaces at high temperatures. The results demonstrate that the slippery surfaces showed anti-wetting for liquids and a remarkable anti-adhesion effect on soft tissues at high temperatures.

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A ...

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 ...