This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry &#38; Energy (MOTIE) of the Republic of Korea (No. 20214000000280), and the Chung-Ang University Graduate Research Scholarship 2021.

1. Fabrication of electrode and supercapacitor (Figure 1)
<ol>
	<li>Prepare the electrodes prior to the electrochemical analysis by combining 80 weight (wt)% of the electrode active material (0.8 g activated carbon), 10 wt% of the conductive material (0.1 g carbon black), and 10 wt% of the binder (0.1 g polytetrafluoroethylene (PTFE)).
	<ol>
		<li>Drop isopropanol (IPA; 0.1-0.2 mL) into the above-mentioned mixture, then spread the mixture thinly into a dough with a roller.</li>
	</ol>
	</li>
	<li>Before attaching the electrode to stainless steel (SUS) mesh, cut the SUS mesh to dimensions of 1.5 cm (width) &#215; 5 cm (length). After weighing the SUS mesh, coat the electrode (1 cm2) with a thickness of 0.1-0.2 mm on a SUS mesh and compress it with an electrode pressing machine. Here, the mass range of the electrode was 0.001-0.003 g.</li>
	<li>Dry the assembled supercapacitor electrode in an oven at 80 &#176;C for about 1 day to evaporate the IPA.</li>
	<li>Weigh the SUS mesh to obtain the weight of the electrode and then immerse the mesh in the electrolyte (2 M H2SO4 aqueous solution).</li>
	<li>Place the SUS mesh in a desiccator to remove air bubbles at the surface of the supercapacitor electrode.</li>
</ol>
2. Preparation of sequence file for electrochemical analysis
<ol>
	<li>CV sequence settings to obtain the analysis results.
	<ol>
		<li>Run the potentiostat measurement program to set the measurement experiment sequence file (Figure 2A).</li>
		<li>Click the Experiment button in the toolbar and go to Sequence File Editor &#62; New or click the New Sequence button (Figure 2B). Click the Add button to add a sequence step (Figure 3A).</li>
		<li>In every step, set Control as Sweep, Configuration as PSTAT, Mode as CYCLIC, and Range as Auto. Set the Reference for Initial(V) and Middle(V) as Eref and put -200e-3 in the Value. Set the Reference for Final(V) as Eref and put 800e-3 in the Value.</li>
		<li>The voltage scan rate is set as the desired value&#160;by&#160;the user. Here, the scan rate&#160;was&#160;set to 10&#160;mV/s. Put the value in Scanrate(V/s) as 10.0000e-3. Copy step-1 and click Paste[Dn] to paste it to step-2~5. Change the value of Scanrate(V/s) to either 20.000e-3, 30.000e-3, 50.000e-3, and 100.00e-3 respectively.</li>
		<li>Set Quiet time(s) as 0 and Segments as the number 2n+1 where n is the number of cycles. Here, 21 was applied for 10 cycles.</li>
		<li>Set Cut Off Condition as follows: for Condition-1 set Item as Step End and Go Next as Next.</li>
		<li>In the Controlling Miscellaneous Setting section, in the Sampling tab, set Item as Times(s), OP as &#62;=, and DeltaValue as 0.333333 (step-1), 0.166666 (step-2), 0.111111 (step-3), 0.06667 (step-4), and 0.03333&#160;(step-5) for each scan rate. This is the time interval for recording the data.</li>
		<li>Click Save As to save the CV analysis sequence file in any folder of the computer.</li>
	</ol>
	</li>
	<li>GCD sequence settings to obtain the analysis results
	<ol>
		<li>Run the potentiostat measurement program to set the measurement experiment sequence file (Figure 2A).</li>
		<li>Click the Experiment button in the toolbar and go to Sequence File Editor &#62; New or click the New Sequence button (Figure 2B). Click the Add button to add a sequence step (Figure 4A,B).</li>
		<li>In Step-1, set Control as CONSTANT, Configuration as GSTAT, Mode as NORMAL, and Range as Auto. Set the Reference for Current(A) as ZERO. When the mass of the electrode is 0.00235 g, set Value as 1.8618e-3 which means the current density is 1 A/g.</li>
		<li>Set Cut Off Condition as follow: for Condition-1 set Item as Voltage, OP as &#62;=, DeltaValue as 800e-3, and Go Next as Next.</li>
		<li>Set the following in the Controlling Miscellaneous setting section: in the Sampling tab, set Item as Times(s), OP as &#62;=, and DeltaValue as 0.1.</li>
		<li>In Step-2, each set is the same as in Step-1, except set value of Current(A) as the negative value of Step-1 (-1.8618e-3). Set Condition-1 as follows: Item as Voltage, OP as &#60;=, DeltaValue as -200e-3, and Go Next as Next.</li>
		<li>In Step-3, set Control as LOOP, Configuration as CYCLE, and set List-1 in Condition-1 of Cut Off Condition as Loop Next, Go Next as Step-1, and set List-2 as Step End, and Go Next as Next. Set the Iteration value as 10 which is the number of repeating cycles.</li>
		<li>Step-1, step-2, and step-3 form a single loop. Copy and paste them after step-4 and change the value of Current (A) to either 3.7236e-3, 5.5855e-3, 9.3091e-3, or 18.618e-3, calculated for various current densities of 2,3,5, and 10 A/g.</li>
		<li>Click Save As to save the GCD analysis sequence file in any folder of the computer.</li>
	</ol>
	</li>
	<li>EIS sequence settings to obtain the analysis results
	<ol>
		<li>Run the potentiostat measurement program to set the measurement experiment sequence file (Figure 2A).</li>
		<li>Click the Experiment button in the toolbar and go to Sequence File Editor &#62; New or click the New Sequence button (Figure 2B). Click the Add button to add a sequence step (Figure 5A,B).</li>
		<li>In Step-1, set Control as CONSTANT, Configuration as PSTAT, Mode as TIMER STOP, and Range as Auto. Set the Reference for Voltage(V) as Eref and Value as 500e-3 which is half of the size of the voltage range.</li>
		<li>Set cut-off condition as follows: for Condition-1 set Item as Step Time, OP as &#62;=, DeltaValue as 3:00, and Go Next as Next. This is the process for stabilizing the potentiostat device.</li>
		<li>In Step-2, set Control as EIS, Configuration as PSTAT, Mode as LOG, and Range as Auto. Set Speed of Initial (Hz) as Normal and value of Initial (Hz) and Middle (Hz) as 1.0000e+6 which is the high-frequency value and Final (Hz) as 10.000e-6, which is the low-frequency value.</li>
		<li>Set the Reference for Bias(V) as Eref and Value as 500e-3. To get a linear response result, set the amplitude (Vrms) as 10.000e-3. Set Density as 10 and Iteration as 1.</li>
		<li>Click Save as to save the EIS analysis sequence file in any folder of the computer.</li>
	</ol>
	</li>
</ol>
3. Electrochemical analysis
<ol>
	<li>Operate the potentiostat device and run the measurement program to perform the CV, GCD, and EIS analyses. Fill 100 mL of 2 M H2SO4 aqueous electrolyte in a glass container (a beaker-shaped glass container was used).</li>
	<li>Before starting the measurement, in the potentiostat, connect the three types of lines: the working electrode (L-WE), the reference electrode (L-RE), and the counter electrode (L-CE), to the SUS mesh, reference electrode (Ag/AgCl), and counter electrode (Pt wire), respectively (Figure 6). Connect the fourth line, the working sensor (L-WS) to the L-WE.</li>
	<li>Cover the glass container with a cap, and immerse the three electrodes in the electrolyte through a perforation in the cap. Position the electrodes so that the WE is maintained at a constant distance between the CE and RE.</li>
	<li>Run the measurement program and open the prepared sequence. Click Apply to CH to insert the sequence to the potentiostat&#39;s channel. Start the measurement by clicking the Start button.</li>
</ol>
4. Data analysis
<ol>
	<li>CV data analysis for fitting the graph
	<ol>
		<li>Open raw measurement data in the convert program to obtain the results in spreadsheet format. Click the File button and open the raw data. Select all cycles and click Export ASCII on the toolbar. Check the Cycle, Voltage, and Current in Columns to Export on the right side of the program.</li>
		<li>Click Create Directory and then click Export to convert raw data to spreadsheet format.</li>
		<li>Open the spreadsheet file and extract the voltage and current values of cycles 10, 20, 30, 40, and 50, which are the last cycles at each scan rate.</li>
		<li>Plot the CV graph with the voltage as the X-axis and specific current density as the Y-axis.</li>
	</ol>
	</li>
	<li>GCD data analysis for fitting the graph
	<ol>
		<li>Open raw measurement data in the convert program to obtain the results in spreadsheet format. Click the File button and open the raw data. Select all cycles and click Export ASCII on the toolbar. Check the Cycle, Voltage, and CycleTime in Columns to Export on the right side of the program.</li>
		<li>Click Create Directory and then click Export to convert raw data to spreadsheet format.</li>
		<li>Open the spreadsheet file and extract the voltage and CycleTime values for cycles 10, 20, 30, 40, and 50, which are the last cycles at each current density.</li>
		<li>Plot the GCD graph with the cycle time as the X-axis and voltage as the Y-axis.</li>
	</ol>
	</li>
	<li>EIS data analysis for fitting the graph
	<ol>
		<li>Open raw measurement data in EIS program. Click the Open file icon and open raw data and click the file name that was applied to see the detailed data.</li>
		<li>Extract Z&#39; [Ohm] as the X value and Z&#39;&#39; [Ohm] as the Y value and plot the EIS graph.</li>
	</ol>
	 </li>
</ol>

The authors have nothing to disclose.

This study provides a protocol for various analyses using a three-electrode system with a potentiostat device. This system is widely used to evaluate the electrochemical performance of supercapacitors. A suitable sequence for each analysis (CV, GCD, and EIS) is important for obtaining optimized electrochemical data. Compared with the two-electrode system having a simple setup, the three-electrode system is specialized for analyzing supercapacitors at the material level15. However, the selection of...

Supercapacitors have attracted enormous attention as suitable power sources for a variety of applications such as microelectronic devices, electric vehicles (EVs), and stationary energy storage systems. In EV applications, supercapacitors can be used for rapid acceleration and can enable the storage of regenerative energy during the deceleration and braking processes. In renewable energy fields, such as solar power generation1 and wind power generation2, supercapacitors can be used as stationary energy storage systems3,4. Renewable energy generation is limited by the fluctuating and intermittent nature of these energy supplies; therefore, an energy storage system that can respond immediately during irregular power generation is required5. Supercapacitors, which store energy via mechanisms that differ from those of lithium-ion batteries, exhibit a high power density, stable cycle performance, and fast charging-discharging6. Depending on the storage mechanism, supercapacitors can be distinguished into double-layer capacitors (EDLCs) and pseudocapacitors7. EDLCs accumulate electrostatic charge at the electrode surface. Therefore, the capacitance is determined by the amount of charge, which is affected by the surface area and porous structure of the electrode materials. By contrast, pseudocapacitors, which consist of conducting polymers and metal oxide materials, store charge through a Faradaic reaction process. The various electrochemical properties of supercapacitors are related to the electrode materials, and developing new electrode materials is the main issue in improving the performance of supercapacitors8. Hence, evaluating the electrochemical properties of these new materials or systems is important in the progress of research and further applications in real life. In this regard, electrochemical evaluation using a three-electrode system is the most basic and widely utilized method in lab-scale research of energy storage systems9,10,11,12,13.
The three-electrode system is a simple and reliable approach for evaluating the electrochemical properties, such as the specific capacitance, resistance, conductivity, and cycle life of supercapacitors14. The system offers the benefit of enabling analysis of the electrochemical characteristics of single materials15, which is in contrast to the two-electrode system, where the characteristics can be studied through the analysis of the given material. The two-electrode system just gives information about the reaction between two electrodes. It is suitable for analyzing the electrochemical properties of the entire energy storage system. The potential of the electrode is not fixed. Therefore, it is not known at what voltage the reaction takes place. However, three-electrode system analyzes only one electrode with fixing potential which can perform a detailed analysis of the single electrode. Therefore, the system is targeted toward analyzing the specific performance at the material level. The three-electrode system consists of a working electrode (WE), reference electrode (RE), and counter electrode (CE)16,17. The WE is the target of research, assessment as it performs the electrochemical reaction of interest18 and is composed of a redox material that is of potential interest. In the case of EDLCs, utilizing high surface area materials is the main issue. Therefore, porous materials with a high surface area and micropores, such as porous carbon, graphene, and nanotubes, are preferred19,20. Activated carbon is the most common material for EDLCs because of its high specific area (&#62;1000 m2/g) and many micropores. Pseudocapacitors are fabricated with materials that can undergo a Faradaic reaction21. Metal oxides (RuOx, MnOx, etc.) and conducting polymers (PANI, PPy, etc.) are commonly used22. The RE and CE are used to analyze the electrochemical properties of the WE. The RE serves as a reference for measuring and controlling the potential of the system; the normal hydrogen electrode (NHE) and Ag/AgCl (saturated KCl) are generally chosen as the RE23. The CE is paired with the WE and completes the electrical circuit to allow charge transfer. For the CE, electrochemically inert materials are used, such as platinum (Pt) and gold (Au)24. All components of the three-electrode system are connected to a potentiostat device, which controls the potential of the entire circuit.
Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) are typical analytical methods that use a three-electrode system. Various electrochemical characteristics of supercapacitors can be assessed using these methods. CV is the basic electrochemical method used to investigate the electrochemical behavior (electron transfer coefficient, reversible or irreversible, etc.) and capacitive properties of material during repeated redox processes14,24. The CV plot shows redox peaks related to the reduction and oxidation of the material. Through this information, researchers can evaluate the electrode performance and determine the potential where the material is reduced and oxidized. Furthermore, through CV analysis, it is possible to determine the amount of charge that material or electrode can store. The total charge is a function of the potential, and the capacitance can be easily calculated6,18. Capacitance is the main issue in supercapacitors. A higher capacitance represents the ability to store more charge. EDLCs give rise to rectangular CV patterns with linear lines so that the capacitance of the electrode can be calculated easily. Pseudocapacitors present redox peaks in rectangular plots. Based on this information, researchers can assess the electrochemical properties of materials using CV measurements18.
GCD is a commonly employed method for identifying the cycle stability of an electrode. For long-term use, the cycle stability should be verified at a constant current density. Each cycle consists of charge-discharge steps14. Researchers can determine the cycle stability through variations in the charge-discharge graph, specific capacitance retention, and Coulombic efficiency. EDLCs give rise to a linear pattern; thus, the specific capacitance of the electrode can be calculated easily using the slope of the discharge curve6. However, pseudocapacitors exhibit a nonlinear pattern. The discharge slope varies during the discharging process7. Furthermore, the internal resistance can be analyzed through the current-resistance (IR) drop, which is the potential drop owing to the resistance6,25.
EIS is a useful method for identifying the impedance of energy storage systems without destruction of the sample26. The impedance can be calculated by applying a sinusoidal voltage and determining the phase angle14. The impedance is also a function of the frequency. Therefore, the EIS spectrum is acquired over a range of frequencies. At high frequencies, kinetic factors such as the internal resistance and charge transfer are operative24,27. At low frequencies, the diffusion factor and Warburg impedance can be detected, which are related to mass transfer and thermodynamics24,27. EIS is a powerful tool for analyzing the kinetic and thermodynamic properties of a material at the same time28. This study describes the analysis protocols for evaluating the electrochemical performance of supercapacitors using a three-electrode system.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Activated carbon</td>
			<td>GS</td>
			<td></td>
			<td>Active material</td>
		</tr>
		<tr>
			<td>Ag/AgCl electrode</td>
			<td>BASi</td>
			<td>RE-5B</td>
			<td>Reference electrode</td>
		</tr>
		<tr>
			<td>Carbon black</td>
			<td>Hyundai</td>
			<td></td>
			<td>Conductive material</td>
		</tr>
		<tr>
			<td>Desicator</td>
			<td>Navimro</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Electrode pressing machine</td>
			<td>Rotech</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Extractor</td>
			<td>WonA Tech</td>
			<td></td>
			<td>Convert program (raw data to excel form)</td>
		</tr>
		<tr>
			<td>Isopropanol(IPA)</td>
			<td>Samchun</td>
			<td>I0346</td>
			<td>Solvent to melt the binder</td>
		</tr>
		<tr>
			<td>Polytetrafluoroethylene(PTFE)</td>
			<td>Hyundai</td>
			<td></td>
			<td>Binder</td>
		</tr>
		<tr>
			<td>Potentiostat</td>
			<td>WonA Tech</td>
			<td>Zive SP1</td>
			<td></td>
		</tr>
		<tr>
			<td>Pt electrode</td>
			<td>BASi</td>
			<td>MW-018122017</td>
			<td>Counter electrode</td>
		</tr>
		<tr>
			<td>Reaction flask</td>
			<td>Duran</td>
			<td></td>
			<td>Container for electrolyte</td>
		</tr>
		<tr>
			<td>SM6</td>
			<td>WonA Tech</td>
			<td></td>
			<td>Program of setting sequence and measuring electrochemical result</td>
		</tr>
		<tr>
			<td>Sulfuric acid</td>
			<td>Samshun</td>
			<td>S1423</td>
			<td>Electrolyte</td>
		</tr>
		<tr>
			<td>SUS mesh</td>
			<td>Navimro</td>
			<td></td>
			<td>Current collector</td>
		</tr>
		<tr>
			<td>Teflon cap</td>
			<td>WonA Tech</td>
			<td></td>
			<td>Cap of the electrolyte continer</td>
		</tr>
		<tr>
			<td>Zman</td>
			<td>WonA Tech</td>
			<td></td>
			<td>EIS program</td>
		</tr>
	</tbody>
</table>

evaluating the electrochemical properties of supercapacitors using the three-electrode system

The three-electrode system is a basic and general analytical platform for investigating the electrochemical performance and characteristics of energy storage systems at the material level. Supercapacitors are one of the most important emergent energy storage systems developed in the past decade. Here, the electrochemical performance of a supercapacitor was evaluated using a three-electrode system with a potentiostat device. The three-electrode system consisted of a working electrode (WE), reference electrode (RE), and counter electrode (CE). The WE is the electrode where the potential is controlled and the current is measured, and it is the target of research. The RE acts as a reference for measuring and controlling the potential of the system, and the CE is used to complete the closed circuit to enable electrochemical measurements. This system provides accurate analytical results for evaluating electrochemical parameters such as the specific capacitance, stability, and impedance through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Several experimental design protocols are proposed by controlling the parameter values of the sequence when using a three-electrode system with a potentiostat device to evaluate the electrochemical performance of supercapacitors. Through these protocols, the researcher can set up a three-electrode system to obtain reasonable electrochemical results for assessing the performance of supercapacitors.

The electrodes were manufactured according to protocol step 1 (Figure 1). Thin and homogeneous electrodes were attached to SUS mesh with a size of 1 cm2 and 0.1-0.2 mm thickness. After drying, the weight of the pure electrode was obtained. The electrode was immersed in a 2 M H2SO4 aqueous electrolyte, and the electrolyte was allowed to sufficiently permeate the electrode before the electrochemical analyses. The production sequence and system setting for the e...

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Evaluating the Electrochemical Properties of Supercapacitors using the Three-Electrode System

The protocol describes the evaluation of various electrochemical properties of supercapacitors using a three-electrode system with a potentiostat device.

The three-electrode system is a basic and general analytical platform for investigating the electrochemical performance and characteristics of energy ...

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11.6K Views.  Chung-Ang University. The protocol describes the evaluation of various electrochemical properties of supercapacitors using a three-electrode system with a potentiostat device.

Video: Evaluating the Electrochemical Properties of Supercapacitors using the Three-Electrode System

Fabrication of VB2/Air Cells for Electrochemical Testing

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Fabrication of VB2/Air Cells for Electrochemical Testing

A protocol is presented to study multi-electron metal/air battery systems by using previous technology developed for the zinc/air cell. Electrochemical testing is then performed on fabricated batteries to evaluate performance.

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Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

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In this article a detailed procedure for surface doping of silicon substrate as well as silicon nanowires is demonstrated. Phosphorus dopant source was formed using tetraethyl methylenediphosphonate monolayer on a silicon substrate. This monolayer containing substrate was brought to contact with a pristine intrinsic silicon target substrate and annealed while in contact. Sheet resistance of the target substrate was measured using 4 point probe. Intrinsic silicon nanowires were synthesized by chemical vapor deposition (CVD) process using a vapor-liquid-solid (VLS) mechanism; gold nanoparticles were used as catalyst for nanowire growth. The nanowires were suspended in ethanol by mild sonication. This suspension was used to dropcast the nanowires on silicon substrate with a silicon nitride dielectric top layer. These nanowires were doped with phosphorus in similar manner as used for the intrinsic silicon wafer. Standard photolithography process was used to fabricate metal electrodes for the formation of nanowire based field effect transistor (NW-FET). The electrical properties of a representative nanowire device were measured by a semiconductor device analyzer and a probe station.

A detailed procedure for surface doping of Silicon interfaces is provided. The ultra-shallow surface doping is demonstrated by using phosphorus containing monolayers and rapid annealing process. The method can be used for doping of macroscopic area surfaces as well as nanostructures.

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Using Microwave and Macroscopic Samples of Dielectric Solids to Study the Photonic Properties of Disordered Photonic Bandgap Materials

Recently, disordered photonic materials have been suggested as an alternative to periodic crystals for the formation of a complete photonic bandgap (PBG). In this article we will describe the methods for constructing and characterizing macroscopic disordered photonic structures using microwaves. The microwave regime offers the most convenient experimental sample size to build and test PBG media. Easily manipulated dielectric lattice components extend flexibility in building various 2D structures on top of pre-printed plastic templates. Once built, the structures could be quickly modified with point and line defects to make freeform waveguides and filters. Testing is done using a widely available Vector Network Analyzer and pairs of microwave horn antennas. Due to the scale invariance property of electromagnetic fields, the results we obtained in the microwave region can be directly applied to infrared and optical regions. Our approach is simple but delivers exciting new insight into the nature of light and disordered matter interaction.

Our representative results include the first experimental demonstration of the existence of a complete and isotropic PBG in a two-dimensional (2D) hyperuniform disordered dielectric structure. Additionally we demonstrate experimentally the ability of this novel photonic structure to guide electromagnetic waves (EM) through freeform waveguides of arbitrary shape.

Disordered structures offer new mechanisms for forming photonic bandgaps and unprecedented freedom in functional-defect designs. To circumvent the computational challenges of disordered systems, we construct modular macroscopic samples of the new class of PBG materials and use microwaves to characterize their scale-invariant photonic properties, in an easy and inexpensive manner.

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Integrating a Triplet-triplet Annihilation Up-conversion System to Enhance Dye-sensitized Solar Cell Response to Sub-bandgap Light

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An integrated device, incorporating a dye-sensitized solar cell and triplet-triplet annihilation up-conversion unit was produced, affording enhanced light harvesting, from a wider section of the solar spectrum. Under modest irradiation levels a significantly enhanced response to low energy photons was demonstrated, yielding a record figure of merit for dye-sensitized solar cells.

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Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step process that finishes with Negishi coupling. Negishi coupling is a cross-coupling process in which a chemical precursor is first lithiated, followed by transmetallation with ZnCl2. The resultant organozinc compound can be coupled to a dibrominated aromatic precursor to give the conjugated monomer. Polymer films can be prepared via electropolymerization of the monomer and characterized using cyclic voltammetry and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. Nanoparticles (NPs) are prepared via emulsion polymerization of the monomer using a two-surfactant system to yield an aqueous dispersion of the polymer NPs. The NPs are characterized using dynamic light scattering, electron microscopy, and UV-Vis-NIR-spectroscopy. Cytocompatibility of NPs is investigated using the cell viability assay. Finally, the NP suspensions are irradiated with a NIR laser to determine their effectiveness as potential materials for photothermal therapy (PTT).

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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 ...

Uncoupling Coriolis Force and Rotating Buoyancy Effects on Full-Field Heat Transfer Properties of a Rotating Channel

An experimental method for exploring the heat transfer characteristics of an axially rotating channel is proposed. The governing flow parameters that characterize the transport phenomena in a rotating channel are identified via the parametric analysis of the momentum and energy equations referring to a rotating frame of reference. Based on these dimensionless flow equations, an experimental strategy that links the design of the test module, the experimental program and the data analysis is formulated with the attempt to reveal the isolated Coriolis-force and buoyancy effects on heat transfer performances. The effects of Coriolis force and rotating buoyancy are illustrated using the selective results measured from rotating channels with various geometries. While the Coriolis-force and rotating-buoyancy impacts share several common features among the various rotating channels, the unique heat transfer signatures are found in association with the flow direction, the channel shape and the arrangement of heat transfer enhancement devices. Regardless of the flow configurations of the rotating channels, the presented experimental method enables the development of physically consistent heat transfer correlations that permit the evaluation of isolated and interdependent Coriolis-force and rotating-buoyancy effects on the heat transfer properties of rotating channels.

Here, we present an experimental method for decoupling the interdependent Coriolis-force and rotating-buoyancy effects on full-field heat transfer distributions of a rotating channel.

An experimental method for exploring the heat transfer characteristics of an axially rotating channel is proposed. The governing flow parameters that ...

Three-electrode Coin Cell Preparation and Electrodeposition Analytics for Lithium-ion Batteries

As lithium-ion batteries find use in high energy and power applications, such as in electric and hybrid-electric vehicles, monitoring the degradation and subsequent safety issues becomes increasingly important. In a Li-ion cell setup, the voltage measurement across the positive and negative terminals inherently includes the effect of the cathode and anode which are coupled and sum to the total cell performance. Accordingly, the ability to monitor the degradation aspects associated with a specific electrode is extremely difficult because the electrodes are fundamentally coupled. A three-electrode setup can overcome this problem. By introducing a third (reference) electrode, the influence of each electrode can be decoupled, and the electrochemical properties can be measured independently. The reference electrode (RE) must have a stable potential that can then be calibrated against a known reference, for example, lithium metal. The three-electrode cell can be used to run electrochemical tests such as cycling, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). Three-electrode cell EIS measurements can elucidate the contribution of individual electrode impedance to the full cell. In addition, monitoring the anode potential allows the detection of electrodeposition due to lithium plating, which can cause safety concerns. This is especially important for the fast charging of Li-ion batteries in electric vehicles. In order to monitor and characterize the safety and degradation aspects of an electrochemical cell, a three-electrode setup can prove invaluable. This paper aims to provide a guide to constructing a three-electrode coin cell setup using the 2032-coin cell architecture, which is easy to produce, reliable, and cost-effective.

Three-electrode cells are useful in studying the electrochemistry of lithium-ion batteries. Such an electrochemical setup allows the phenomena associated with the cathode and anode to be decoupled and examined independently. Here, we present a guide for construction and use of a three-electrode coin cell with emphasis on lithium plating analytics.

As lithium-ion batteries find use in high energy and power applications, such as in electric and hybrid-electric vehicles, monitoring the degradation and ...

Evaluating Targeting Accuracy in the Focal Plane for an Ultrasound-guided High-intensity Focused Ultrasound Phased-array System

Phased arrays are increasingly used as high-intensity focused ultrasound (HIFU) transducers in the existing extracorporeal ultrasound-guided HIFU (USgHIFU) systems. The HIFU transducers in such systems are usually spherical in shape with a central hole where a US imaging probe is mounted and can be rotated. The image on the plane of treatment can be reconstructed through the image sequence acquired during the rotation of the probe. Therefore, the treatment plan can be made on the reconstructed images. In order to evaluate the targeting accuracy in the focal plane of such systems, the protocol of a method using a bovine muscle and marker-embedded phantom is described. In the phantom, four solid balls at the corners of a square resin model serve as the reference markers in the reconstructed image. The target should be moved so that both its center and the center of the square model can coincide according to their relative positions in the reconstructed image. Swine muscle with a thickness of about 30 mm is placed above the phantom to mimic the beam path in clinical settings. After sonication, the treatment plane in the phantom is scanned and the boundary of the associated lesion is extracted from the scanned image. The targeting accuracy can be evaluated by measuring the distance between the centers of target and lesion, as well as three derivative parameters. This method cannot only evaluate the targeting accuracy of the target consisting of multiple focal spots rather than a single focal spot in a clinically relevant beam path of the USgHIFU phased-array system, but it can be also used in the preclinical evaluation or regular maintenance of USgHIFU systems configured with phased-array or self-focused HIFU transducer.

This study describes a protocol to evaluate the targeting accuracy in the focal plane of an ultrasound-guided high-intensity focused ultrasound phased-array system.

Phased arrays are increasingly used as high-intensity focused ultrasound (HIFU) transducers in the existing extracorporeal ultrasound-guided HIFU ...

Operation of the Collaborative Composite Manufacturing (CCM) System

The automated tape placement and the automated fiber placement (AFP) machines provide a safer working environment and reduce the labor intensity of workers than the traditional manual fiber placement does. Thus, the production accuracy, repeatability and efficiency of composite manufacturing are significantly improved. However, the current AFP systems can only produce the composite components with large open surface or simple revolution parts, which cannot meet the growing interest in small complex or closed structures from industry.
In this research, by employing a 1-degree of freedom (DoF) rotational stage, a 6-RSS parallel robot, and a 6-DoF serial robot, the dexterity of the AFP system can be significantly improved for manufacturing complex composite parts. The rotational stage mounted on the parallel robot is utilized to hold the mandrel and the serial robot carries the placement head to mimic two human hands that have enough dexterity to lay the fiber to the mandrel with complex contour.
Although the CCM system increases the flexibility of composite manufacturing, it is quite time-consuming or even impossible to generate the feasible off-line path, which ensures uniform lay-up of subsequent fibers considering the constraints like singularities, collisions between the fiber placement head and mandrel, smooth fiber direction change and keeping the fiber placement head along the norm of the part&#39;s surface, etc. Moreover, due to the existing positioning error of the robots, the on-line path correction is needed. Therefore, the on-line pose correction algorithm is proposed to correct the paths of both parallel and serial robots, and to keep the relative path between the two robots unchanged through the visual feedback when the constraint or singularity problems in the off-line path planning occur. The experimental results demonstrate the designed CCM system can fulfill the movement needed for manufacturing a composite structure with Y-shape.

Operation of the Collaborative Composite Manufacturing CCM System

A collaborative composite manufacturing system is developed for robotic lay-up of composite laminates using the prepreg tape. The proposed system allows the production of composite laminates with high levels of geometrical complexity. The issues in the path planning, coordination of the robots and control are addressed in the proposed method.

The automated tape placement and the automated fiber placement (AFP) machines provide a safer working environment and reduce the labor intensity of ...