This work was supported by the US National Science Foundation Grant DMR-1455108 and CMMI-1663098.

CAUTION: Please consult all relevant materials safety data sheets (MSDS) before use. Some chemicals used in the protocol are toxic. Please use all appropriate safety practices when performing experiments, including the use of engineering controls (fume hood) and personal protective equipment (safety glasses, gloves, lab coat, full-length pants, and closed-toe shoes). The CNC (Computer Numerical Control) machine must be operated by trained personnel. Hydrofluoric acid must be handled inside a fume hood that is identified with a sign stating &#34;Danger, Hydrofluoric Acid Used in this Area&#34; or similar.
1. Sample Preparation
NOTE: Proper surface preparation of samples prior to tribocorrosion tests is critical to ensure good reliability of the performed test and enhance test repeatability. In this protocol, a commercial Al 3003 alloy (Si: 0.1, Fe: 0.4, Cu: 0.08, Mn: 1.1 wt.%, balance Al) is used as an example.
<ol>
	<li>Bulk metallic sample preparation
	<ol>
		<li>Cut as-received Al 3003 alloys (hereafter referred as Al) into several 1.5 &#215; 2 cm2 coupons using a CNC machine.</li>
		<li>Mechanically grind one side of the sample surface using sandpaper with increasing grit numbers (#180, 240, 400, 600, and 1200).
		<ol>
			<li>Grind the sample using #180 sandpaper for 30 s along one arbitrary direction.</li>
			<li>Rotate the sample 90&#730; and grind it using #240 sandpaper until the scratch lines from the previous step are completely eliminated. Use an optical microscope to aid this inspection.</li>
			<li>Repeat the sample rotation procedure and move to the next grinding paper. Use a soft brush between steps to clean the sample surface in running water to eliminate any contamination from the previous step.</li>
		</ol>
		</li>
		<li>After grinding, polish the sample surface using different sizes of high viscosity alumina polishing suspension (1 &#181;m, 0.3 &#181;m, and 0.05 &#181;m) on microfiber cloth pads. Use a different cloth pad for each compound size.
		<ol>
			<li>Pour ~ 1 oz of 1 &#181;m alumina suspension (10-30% alumina, 0.6-1% silica glass, 70-90% water) on a clean cloth pad. Polish the sample in one direction or draw a shape of &#39;8&#39; (avoid drawing a shape of &#39;0&#39;) until removing the scratch lines from the previous step.</li>
			<li>Repeat for 0.3 and 0.05 &#181;m polishing suspension (10-30% alumina, 0.6-1% silica glass, 70-90% water) until reaching a mirror finish.</li>
		</ol>
		</li>
		<li>Place the polished specimen in a beaker with 40 mL of deionized (DI) water and place the beaker in an ultrasonic cleaner for 1-2 min to remove any surface particle. Use compressed gas to completely dry the surface. Figure 1a shows an example of an unpolished vs. a polished Al sample.</li>
		<li>Cut a 5 cm long, ~ 1-2 mm diameter electrical wire and strip away the protective plastic cover (~ 1 cm in length) on both ends to expose the interior Cu wire to air.</li>
		<li>Electrically connect one end of the wire to the back (the unpolished side) of the sample using a conductive tape or conductive epoxy. If using conductive epoxy, follow the manufacturer&#39;s recommendation until complete cure.</li>
		<li>Use electrochemical stop-off lacquer to paint a ~ 1&#215;1 cm2 window on the polished side and the complete back side of the sample. For the back side, paint over the exposed Cu wire.</li>
		<li>Dry the painted sample completely in a well-ventilated fume hood for at least 24 h before the experiments. Figure 1b shows an example of the painted bulk sample, which is used as working electrode for the corrosion and tribocorrosion tests.</li>
	</ol>
	</li>
	<li>Thin film sample preparation 
	NOTE: Metallic thin films deposited on a flat substrate such as glass, Si wafer, and other metal plate using non-equilibrium processing techniques such as physical vapor deposition and electrodeposition can be used for tribocorrosion testing after proper preparation. Here a magnetron-sputtered Al-Mn thin film sample deposited on Si substrate is used as an example to explain the critical steps.
	<ol>
		<li>Polish a Si wafer (100 mm diameter) with 1:50 hydrofluoric acid water solution for 2 min to remove any surface oxidation layer.</li>
		<li>Clean the Si wafer with 95% ethanol. Then dry it with compressed air and transfer it directly into a magnetron sputtering machine vacuum chamber.</li>
		<li>Operate the sputtering machine at 80 W input power under a 5 mTorr argon atmosphere (99.99%)1. Grow a ~ 2-3 &#181;m thickness Al-20 at % Mn film (hereafter referred as Al thin film) using an Al-Mn target in the sputtering machine.</li>
		<li>Spin coat a thin protective layer of a positive photoresist (~ 10 mL for a 100 mL Si wafer) on the deposited side of Si wafer and dice it into several 1.5 &#215; 2 cm2 coupons.</li>
		<li>Immerse the diced sample in acetone for 1 min to completely remove the protective layer. Rinse it by alcohol and finally dry it by compressed air.</li>
		<li>Follow steps 1.1.5 and 1.1.8 to make an electrical connection and paint the sample surface for tribocorrosion test. Figure 1c shows an example of a painted thin film sample.</li>
	</ol>
	</li>
</ol>
2. Tribocorrosion Test
<ol>
	<li>Tribocorrosion machine setup
	<ol>
		<li>Perform a tribocorrosion test using a custom-designed corrosion cell installed on a universal mechanical tester (UMT) as shown in Figure 2a. Use the schematic of the tribocorrosion testing setup as shown in Figure 2b. Figure 3 shows the custom-designed corrosion cell installed on the UMT rotary stage. The force sensing resolution is 50 &#181;N and 50 mN for load ranges of 5-500 mN and 10-1000 N, respectively.</li>
		<li>For the electrochemical measurement, use 2 x&#160;10-17 Amp current resolution and 1014 &#937; input impedance.</li>
	</ol>
	</li>
	<li>Tribocorrosion rate measurement principle
	<ol>
		<li>Measure tribocorrosion resistance according to the ASTM G119 standard2, where the total material loss T = C0 + W0 + S (see introduction for details).
		<ol>
			<li>Measure the corrosion rate C0 from the potentiodynamic test.</li>
			<li>Measure the pure wear rate W0 during cathodic polarization from tribocorrosion test. Apply a ball-on-disc configuration using an alumina ball to impose reciprocal mechanical wear in the load range of mN to a few N.</li>
			<li>For the thin film sample, choose a proper normal load. This ensures that the plastic deformation is confined within the top surface so that the deposited sample thickness is large enough to resemble true bulk material behavior. Such estimation can be made by using Hertzian contact theory12.</li>
			<li>Measure the tribocorrosion rate T from tribocorrosion test at OCP.</li>
			<li>Calculate the synergy S from the above measurements and equation 1.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Measurement of corrosion rate C0 from potentiodynamic (PD) test
	<ol>
		<li>Prepare the working electrode (i.e., bulk or thin film metal specimen under analysis). Clean the surface of the metal with acetone, followed by 95% ethanol.</li>
		<li>Clean the corrosion cell before every corrosion run. Scrub the cell with household detergent and rinse thoroughly with tap water. Repeat this step 3 times.</li>
		<li>Rinse the corrosion cell 3 times with de-ionized water (DI) water to remove potential contaminants found in tap water.</li>
		<li>Pour 100 mL of 95% ethanol into the corrosion cell and swirl around to contact all internal surfaces. Pour out the ethanol and repeat this step 3 times.</li>
		<li>Leave the corrosion cell under a fume-hood for 30 min to allow all ethanol to completely evaporate.</li>
		<li>Take the clean, dry corrosion cell and rinse it with the electrolyte that will be used for the corrosion run. For each rinse, fill the corrosion cell with 40 mL of the electrolyte and repeat this procedure 3 times. For this protocol, rinse the corrosion cell with 3.5 wt% (0.6 M), pH &#8776; 7 sodium chloride aqueous solution (i.e., simulated sea water).</li>
		<li>Following the rinse, fill the corrosion cell with 40 mL of electrolyte ready for the reaction.</li>
		<li>Setup the three-electrode configuration. Use the Al sample, a standard Ag/AgCl, and an activated titanium mesh as the working, reference, and counter electrode respectively.</li>
		<li>Place the working electrode centrally at the bottom of the corrosion cell and glue the bottom using super glue. Place the exposed Cu wire tip above the expected electrolyte surface height.</li>
		<li>Place the reference electrode ~ 1 cm above the working electrode.</li>
		<li>Loosely bend the counter electrode to wrap around the specimen under test (working electrode). The distance between the counter and working electrode is ~ 2-4 cm.</li>
		<li>Connect electrodes with the potentiostat. Ensure that the electrodes are not touching.</li>
		<li>Open the electrochemical software package, which interfaces with the USB controlled potentiostat. Turn the potentiostat on.</li>
		<li>Open and use the Measurement View to view the potential and current readings of corrosion environment. During the OCP phase where no ramp potential is yet applied the current reading between the working (positive potential) and counter (negative) electrode is around 0 &#177; 0.01 &#181;A.</li>
		<li>Leave the sample to equilibrate and stabilize at OCP within the corrosion cell environment. The time duration for this varies (1 to 6 h) and is dependent on the material tested. Monitor the potential using measurement view to determine if a stabilized condition (i.e., a potential change of less than 50 mV over more than half an hour) is reached.</li>
		<li>Run the corrosion test. Following the stabilization of the corrosion potential (Ecorr), ramp the applied potential in the positive direction relative to the reference electrode.</li>
		<li>Select the cyclic voltammetry potentiostat procedure within the setup view from the procedure tab. Enable the following parameters to be sampled for the corrosion run: time, working electrode (WE) potential, and current for the corrosion run.</li>
		<li>Select the option to automate the current range. Set the highest current in the range to be 10 mA, and the lowest current in the range to be 10 nA for the WE.</li>
		<li>Ensure that the final cut-off selection is controlled through the potential by setting the &#39;cycle back&#39; parameter to 0.8 mV to allow the hysteresis loop to complete.</li>
		<li>Record OCP from the measurement view into the OCP parameter text box. Set the start potential at 100 mV below the recorded OCP value. Set the upper vertex potential to 800 mV, the lower vertex to 100 mV below the start potential and the stop potential to 100 mV below the lower vertex potential. Set the scan rate to 0.167 mV/s (ASTM standard).</li>
		<li>Press start. After a few hours, the corrosion test is finished.</li>
		<li>View the results in the software. 
		NOTE: Optical microscopy will be performed after each test. Discard samples showing any indication of crevice corrosion under the stop-off lacquer. The results for each test condition should be repeated at least three times. Figure 4 shows representative results of bulk and thin film Al after PD tests in 3.5 wt.% NaCl aqueous solution at pH &#8776; 7.</li>
		<li>Determine the pitting potential (Epit) from the PD test as the potential at which a rapid increase in corrosion current took place (Figure 4).</li>
		<li>Obtain a nominal value of the cathodic polarization slope (&#946;c) by fitting a straight line to the portion of the polarization curve that corresponds to potentials more than 50 mV lower than Eoc.</li>
		<li>Obtain a nominal value of the anodic polarization slope (&#946;a) likewise using the portion of the curve that started at potentials &#62; 50 mV higher than Eoc and ended at Epit.</li>
		<li>Extrapolate both of those trends to Eoc and suitable average of both to obtain a nominal corrosion current density (icorr) (Figure 4).</li>
		<li>Calculate corrosion rate C0 from the corrosion current icorr using Faraday&#39;s conversion (1 &#181;A.cm-2&#8776; 10.9 &#181;m/y) assuming uniform corrosion with the formation of Al3+. The Faraday&#39;s equation is R = M/nFP(icorr), where R is the corrosion rate, icorr is the corrosion current measured from the PD test, M is the atomic weight of the metal, P is the density, n is the charge number that indicates the number of electrons exchanged within dissolution reaction, and F is Faraday&#39;s constant equivalent to 96,485 C/mol. M/n is the equivalent weight.</li>
	</ol>
	</li>
	<li>Measurement of wear rate W0 from cathodic protection test 
	&#8203;NOTE: To measure the wear rate, an alumina ball with 4 mm diameter is used as the counter body to scratch on the sample surface while the sample is immersed in the solution, as shown in Figure 5. Below is the procedure of cathodic protection test.
	<ol>
		<li>Perform steps from 2.3.1 to 2.3.13 in section 2.3.</li>
		<li>Move the indenter probe down towards the surface of the sample as closer as possible (1 mm distance away from sample surface). Ensure the indenter stays near the center of the sample and there is no electrical contact between the electrodes, the probe, and the sample surface.</li>
		<li>Move the indenter up forward for 200 mm. Pour the 3.5 wt.% NaCl aqueous solution into the corrosion cell until all electrode, probe and sample surface are immersed.</li>
		<li>Move the indenter probe down towards the sample surface as close as possible. Connect the electrodes with the potentiostat.</li>
		<li>Open the electrochemical software package, which interfaces with the USB controlled potentiostat. Turn on the potentiostat.</li>
		<li>Select Experiment to view DC Corrosion and choose Potentiostatic mode.</li>
		<li>Apply a cathodic potential of 350 mV below OCP. This cathodic potential (350 mV below OCP) is chosen to avoid hydrogen evolution reaction during sliding, which might lead to embrittlement of the samples13. The initial potential and final potential is -350 mV vs Eoc. The total experimental time is 1,800 s including 300 s of scratching time.</li>
		<li>Set up the wear test from the UMT software by applying 1 Hz scratch frequency, 5 mm scratch length, and 0.5 N normal load. Press the Run button in the wear system to start the tribocorrosion. Note, the scratch frequency, scratch length, and applied load are testing parameters that can be varied based on the purpose of experiment.</li>
		<li>After 1,800 s, the test finished. View the results in the UMT software. For reliable testing, repeat the tests under the same condition for at least three times.</li>
		<li>Use a surface profilometer to measure the depth of wear track from at least three different locations along the wear track for each sample. The scan direction is vertical to the scratch line and the scan length is larger than the width of wear track (see Figure 6). The radius of the profilometer stylus is 5 &#181;m, the stylus force is 3 mg, and the scan resolution is 0.028 &#181;m/sample.</li>
		<li>Export the profile measurement data. Use software to directly integrate the depth below the unworn surface (shaded area in Figure 7).</li>
		<li>Calculate the cross-sectional wear area as <img alt="Equation 2" src="/files/ftp_upload/58235/58235eq2.jpg" style="opacity: 0.9;" />, where h (x) is the surface height as a function of position x, and a is the wear track width. Using A, calculate the wear volume as <img alt="Equation 3" src="/files/ftp_upload/58235/58235eq3.jpg" style="opacity: 0.9;" />(A is the cross-sectional wear area, L is the wear track length = 5 mm).</li>
		<li>Finally, calculate the wear rate W0 as W0=V/Ltot, where Ltot is the total sliding distance.</li>
	</ol>
	</li>
	<li>Measurement of tribocorrosion rate T&#160;from tribocorrosion test at OCP
	<ol>
		<li>Following steps 2.4.1-2.4.8 except in step 2.4.6, set the applied potential during the test as the OCP.</li>
		<li>Once the test is finished, follow step 2.4.10 to calculate T, where T=V/Ltot.</li>
	</ol>
	</li>
	<li>Calculation of wear-corrosion synergy S
	<ol>
		<li>After performing all previous steps, calculate the wear-corrosion synergy as S=T-W0-C0, where T is the total material loss measured at OCP, W0 is the material loss measured at the cathodic potential primarily due to mechanical wear (where corrosion becomes negligible compared to wear), and C0 is the material loss due to pure corrosion estimated from PD tests14,15. Note, if C0 is measured in terms of depth loss/year from the PD test, it is important to convert it to an equivalent volume loss per time for correct calculation of S.</li>
	</ol>
	</li>
</ol>

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The authors declare no competing financial interests.

There are several critical steps within this protocol. First, proper surface preparation of the samples prior to the tribocorrosion tests is critical to ensure good reliability of the performed test and enhance test repeatability. Different bulk alloys are to be prepared following different procedures to ensure a controlled surface roughness, and removal of any surface contaminants or scales. The procedure described here consists of solely mechanical grinding and polishing. This method generally applies to alloys with medium to high hardness such as Al, Ti, Ni, Cu alloys and steel. For softer alloys such as Mg alloys, electrochemical polishing or ion milling should be coupled with mechanical polishing to achieve the desired surface roughness. Secondly, for thin film sample sputtering, maintaining an ultra-low (&#60; 10-6 Torr) vacuum in the sputtering chamber is critical to ensure low defect concentration in the deposited film, which would otherwise affect the corrosion resistance significantly. Thirdly, when preparing either bulk or thin film samples into the working electrode, it is important to ensure a good electrical connection between the sample and the connecting (Cu) wire. In this protocol, conductive tape or conductive epoxy is used. Alternatively, soldering, spot welding or similar techniques may be used. However, the effect of heating during welding on the microstructure and eventually the tribocorrosion resistance of samples have to be evaluated carefully. This is especially important for metals and alloys with low melting point. Finally, since tribocorrosion involves a three-body interaction (including the two bodies in contact, and the third body in between), it is important to ensure that a new ball tip (or a new area of the ball tip) is used when performing repeated tribocorrosion test.
The current protocol evaluates tribocorrosion rate by measuring material loss. Modifications of this protocol can be easily made to evaluate the depassivation and repassivation kinetics of tribocorrosion. This is achieved by tracking the current, potential, and coefficient of friction (COF) evolution during the test. As an example, Figure&#160;10 and 11 show representative results of the evolution of corrosion potential and COF respectively, of Al thin film after tribocorrosion test at OCP. The arrows in Figure 10 represent the start and finish of scratching. It can be seen that for passive alloys such as Al, the mechanical disruption during tribocorrosion leads to local breakdown/removal of the passive film on the wear track and exposing a depassivated area which leads to a decrease in the corrosion potential by ~ 20 mV. Our earlier work16 showed that the magnitude of corrosion potential reduction is strongly related to the microstructure of the metal given the testing parameters (e.g., applied load, sliding speed, temperature) are the same. For Al with higher hardness and finer microstructure, the same applied load may lead to a smaller depassivated area, hence smaller change in corrosion potential. It is also noted that during the open circuit mode, the current is too low to be detected as the circuit is &#39;open&#39;. However, current evolution during tribocorrosion test at imposed cathodic or anodic potentials can be monitored. An example can be found in our previous work16. Figure 12 shows the current evolution of Al thin film during tribocorrosion at an imposed anodic potential of 200 mV more positive than OCP. This anodic potential was selected within the passive region yet well below the pitting potentials. This result can be used to quantify the wear accelerated corrosion. In this case, the total material loss can be evaluated as T = Vmech + Vchem, where Vmech and Vchem corresponds to the contribution of mechanical and electrochemical material loss, respectively. Specifically, Vchem can be regarded as resulting from metal oxidation under anodic applied potential. Thus it can be calculated by Faraday&#39;s law as 17,18,19 <img alt="Equation 4" src="/files/ftp_upload/58235/58235eq4.jpg" style="font-size: 14px;" />, where Q is the electrical charge (calculated by multiplying the difference between the average anodic current during and before sliding by the time), M is the molecular weight, n is the oxidation valence, F is Faraday&#39;s constant, and &#961; is the density of Al. Figure 13 shows the typical result of both terms for Al thin films. From the above discussion, it can be seen that an evaluation of the electrochemical parameters change, in addition to the weight loss, will thus offer critical insight to the depassivation kinetics during tribocorrosion.
The protocol presented here also bears several limitations. First, the corrosion cell is made from Teflon (polytetrafluoroethylene) or similar material. Thus, all tests were performed near room temperature. For applications that require higher temperature (e.g., above 400 &#176;C for nuclear reactor cores), a special corrosion cell and tip have to be manufactured that will withstand high temperature creep and corrosion. Additional safety is also needed for handling molten salt electrolyte and metallic samples at high temperatures. Secondly, the attachment of a reference electrode near the working electrode (sample) has limited the wear motion to be linear reciprocal. In applications where a rotational motion of the sample is required, a special tribocorrosion setup has to be designed. Thirdly, in the present setup, the wear scratch rate is much faster than the corrosion rate. Hence the contribution of C0 is negligible compared to all other terms. While corrosion itself did not lead to significant material loss during the limited testing time, its effect on S is significant. In real world applications where mechanical scratch occurs at much lower frequencies, this trend might change where C0 may become dominant. Finally, special care has to be paid to errors generated during testing. This is especially important for evaluating the wear-corrosion synergy (S), which is derived from tribocorrosion rate (T), wear rate (W0), and corrosion rate (C0). Thus errors can be accumulated. To minimize errors generated in T and W0, a non-contact 3D optical profilometer (instead of the contact 2D profilometer) can used to determine the total material loss volume. To minimize error in C0, PD tests can be coupled with non-destructive EIS (electrochemical impedance spectroscopy) test to evaluate corrosion rate20.
As a final note, tribocorrosion rate is not a material property, but rather a system&#39;s response that depends on the testing parameters (applied load, sliding speed, etc.), the environment (temperature, pH, salt concentration, etc.), and material properties (hardness, surface roughness, etc.). The protocol presented here is demonstrated using only one set of condition. The readers should consider the differences and adopt appropriate changes in sample preparation, testing setup, and data analysis when dealing with different systems. Alternative testing setup including pin on plate (reciprocating), microabrasion, cylinder on bar, et al. can be found in 21. Tribocorrosion is an emerging interdisciplinary subject. It is hoped that this protocol will facilitate both the evaluation of existing engineering materials as well as the design of new materials resistant to both wear damage and corrosion degradation. Such materials become increasingly demanded in future applications such as advanced implantable medical devices, next generation nuclear power plants, and high capacity fast charging batteries, etc., which all require not only a strong and tough material, but one that is robust and reliable when interacting with some very extreme environment.

Tribocorrosion is a material degradation process caused by the combined effect of wear and corrosion1,2. Tribocorrosion takes place both in nature and in industrial applications where mechanical contact and a corrosive environment are simultaneously present. The complexity of tribocorrosion lies in the fact that chemical and mechanical degradation mechanisms are not independent of each other. A combination of mechanical and chemical attack often leads to accelerated failure, due to synergetic effects. Thus, the total material loss can be calculated as T = C0 + W0 + S (eqn. 1), where C0 is the material loss resulted from corrosion in the absence of wear, W0 is the material loss due to mechanical wear in the absence of corrosion, and S is the material loss due to wear-corrosion synergy3,4. The synergetic effect is prominent for passive alloys such as aluminum, titanium, and stainless steels, which spontaneously form a protective thin (a few nanometer in thickness) oxide film (passive film) when in contact with oxygen or water5,6. During corrosion, and if this passive film is locally disturbed by mechanical wear, depassivation could lead to localized corrosion and unexpected failures1,3,7,8,9.
As an example of the economic impact of tribocorrosion in our society, wear and corrosion are estimated to cost nearly $300 billion per year in the United States10. In Florida, tribocorrosion phenomena of structural alloys in seawater is of interest given its ocean economy (fishing, marine transportation, and coastal construction), which contributes around 4% of Florida&#39;s total Gross Domestic Product11. Thus, a better understanding of tribocorrosion of metals and alloys will lead to better guidelines for application and usage of alloys in harsh environment service conditions. Such understanding will also serve to improve design principles for manufacturing new alloys and coatings against tribocorrosion and enhancing durability.
Tribocorrosion studies require integration of a tribometer and an electrochemical measurement system. The tribometer provides controlled mechanical loading and relative motion, and measures the friction force and sample surface height change. The electrochemical measurement system includes a potentiostat/galvanostat with a zero-resistance ammeter (optional) that determines open-circuit potential (OCP) and electrochemical polarization measurements. Such techniques provide a quick and inexpensive method to obtain the electrochemical properties of a material, where the corrosion rate of a metal can be measured by observing the response of the charge-transfer process to a controlled electrochemical disturbance. Here, we present a testing protocol for determining the tribocorrosion rate and wear-corrosion synergy of Al alloys, mostly following the ASTM standard G1192. This protocol includes sample preparation, machine setup, tribocorrosion testing, and post-testing calculation procedures. We hope this effort will benefit those new to the field to perform reliable and repeatable tribocorrosion tests to evaluate the deformation and degradation behavior of bulk as well as thin film metallic samples.

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			<td height="21" style="height:21px;width:315px;">UMT (universal mechanical testing) machine</td>
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			<td>Reference 600</td>
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			<td height="21" style="height:21px;">Surface profilometer&#160;</td>
			<td style="width:199px;">Veeco&#160;</td>
			<td style="width:239px;">Dektak150</td>
			<td></td>
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			<td height="22" style="height:22px;width:315px;">Al3003</td>
			<td style="width:199px;">Metal supermarkets</td>
			<td style="width:239px;">3003</td>
			<td></td>
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			<td height="21" style="height:21px;width:315px;">Sodium choloride</td>
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			<td style="width:239px;">S640-3</td>
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			<td height="21" style="height:21px;width:315px;">DI water</td>
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			<td height="134" style="height:134px;width:315px;">Grinding paper</td>
			<td style="width:199px;">LECO Corporation</td>
			<td style="width:239px;">810-221-300 (#180) 
			810-223-300 (#240) 
			810-227-300 (#400) 
			810-229-300 (#600) 
			810-036-100 (#1200)</td>
			<td></td>
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		<tr height="36">
			<td height="36" style="height:36px;width:315px;">Polishing Pad</td>
			<td style="width:199px;">Pace Technologies</td>
			<td style="width:239px;">NP. 7008</td>
			<td></td>
		</tr>
		<tr height="70">
			<td height="70" style="height:70px;width:315px;">Polishing suspension</td>
			<td style="width:199px;">Pace Technologies</td>
			<td style="width:239px;">NANO2-1010-06 (1 um) 
			NANO2-1003-06 (0.3 um) 
			NANO2-1005-06 (0.05 um)</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:315px;">Stop-off lacquer</td>
			<td style="width:199px;">Romanoff</td>
			<td style="width:239px;">210-1250</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:315px;">Ag/AgCl Reference electrode</td>
			<td style="width:199px;">SYC Technologies, Inc.</td>
			<td style="width:239px;">CHI111</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:315px;">Compressed air</td>
			<td style="width:199px;">Office depot</td>
			<td style="width:239px;">911-245</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:315px;">Ultrasonic cleaner</td>
			<td style="width:199px;">Cole Parmer</td>
			<td style="width:239px;">8890</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:315px;">Sputtering coater</td>
			<td style="width:199px;">Torr International</td>
			<td style="width:239px;">CRC-100</td>
			<td></td>
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determining tribocorrosion rate and wear-corrosion synergy of bulk and thin film aluminum alloys

The increasing complexity and severity of service conditions in areas, such as aerospace and marine industries, nuclear systems, microelectronics, batteries, and biomedical devices, etc., impose great challenges on the reliable performance of alloys exposed to extreme conditions where mechanical and electrochemical attack co-exist. Finding ways for alloys to mitigate the combined attack of wear and corrosion (i.e., tribocorrosion) under such extreme conditions is thus highly critical for improving their reliability and service lifetime when used in such conditions. The challenge lies in the fact that wear and corrosion are not independent of each other, but rather work synergistically to accelerate the total material loss. Thus, a reliable method to evaluate the tribocorrosion resistance of metals and alloys is needed. Here, a protocol for measuring the tribocorrosion rate and wear-corrosion synergy of Al-based bulk and thin film samples in a corrosive environment under room temperature is presented.

Following the testing protocol described above, the tribocorrosion rate (T) is measured at various potentials. Figure 8 represents the material loss obtained for the Al thin film sample after tribocorrosion at the cathodic (350 mV below OCP), open circuit, and anodic (200 mV above OCP) potential. The test was performed in 3.5 wt.% NaCl aqueous solution for 5 min under 0.5 N normal load, at a 1 Hz sliding frequency and 5 mm stroke length. Prior to each test, the OCP was stabilized for 20 min. Figure 9 shows the summary of all components of eqn. 1, including the tribocorrosion rate (T), wear rate (W0), corrosion rate (C0), and wear-corrosion synergy (S) of Al thin film.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58235/58235fig1.jpg" /> 
Figure 1. Photo of (a) unpolished and polished Al bulk sample, (b) wired and painted bulk, and (c) thin film Al sample for tribocorrosion testing. <a href="https://www.jove.com/files/ftp_upload/58235/58235fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58235/58235fig2.jpg" /> 
Figure 2. (a) Photo of the front of the Bruker UMT machine without custom-made tribocorrosion cell. (b) schematic of tribocorrosion testing setup. <a href="https://www.jove.com/files/ftp_upload/58235/58235fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58235/58235fig3.jpg" /> 
Figure 3. Photo of custom-made tribocorrosion cell installed on the UMT rotary stage. The cell is made from Teflon with an O-ring at the bottom surface to prevent liquid leakage during tribocorrosion test. <a href="https://www.jove.com/files/ftp_upload/58235/58235fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58235/58235fig4.jpg" /> 
Figure 4. Representative potentiodynamic polarization curves of Al bulk and thin film after 1 hour immersion in 0.6 M NaCl solution. <a href="https://www.jove.com/files/ftp_upload/58235/58235fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/58235/58235fig5.jpg" /> 
Figure 5. Photo of tribocorrosion machine during testing where the indentor probe is moving on the sample surface in reciprocal motion. <a href="https://www.jove.com/files/ftp_upload/58235/58235fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/58235/58235fig6.jpg" /> 
Figure 6. Scanning electron microscopy image of the wear track after tribocorrosion test. The dashed lines represent the boundaries of the wear track. <a href="https://www.jove.com/files/ftp_upload/58235/58235fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/58235/58235fig7.jpg" /> 
Figure 7. Typical wear track profile of Al thin film after tribocorrosion test obtained by profilometer. <a href="https://www.jove.com/files/ftp_upload/58235/58235fig7large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 8" class="xfigimg" src="/files/ftp_upload/58235/58235fig8.jpg" /> 
Figure 8. Summary of tribocorrosion rate (T) of Al thin films at different applied potential. The arrow bar represents one standard deviation from all repeated test results. <a href="https://www.jove.com/files/ftp_upload/58235/58235fig8large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 9" class="xfigimg" src="/files/ftp_upload/58235/58235fig9.jpg" /> 
Figure 9. Summary of tribocorrosion rate (T), wear rate (W0), corrosion rate (C0), and wear-corrosion synergy (S) of Al thin films. The arrow bar represents one standard deviation from all repeated test results. <a href="https://www.jove.com/files/ftp_upload/58235/58235fig9large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 10" class="xfigimg" src="/files/ftp_upload/58235/58235fig10.jpg" /> 
Figure 10. Evolution of corrosion potential during tribocorrosion test of Al thin film at OCP. <a href="https://www.jove.com/files/ftp_upload/58235/58235fig10large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 11" class="xfigimg" src="/files/ftp_upload/58235/58235fig11.jpg" /> 
Figure 11. Evolution of coefficient of friction (COF) during tribocorrosion test of Al thin film at OCP. <a href="https://www.jove.com/files/ftp_upload/58235/58235fig11large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 12" class="xfigimg" src="/files/ftp_upload/58235/58235fig12.jpg" /> 
Figure 12. Evolution of corrosion current during tribocorrosion test of Al thin film at 200 mV above OCP. <a href="https://www.jove.com/files/ftp_upload/58235/58235fig12large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 13" class="xfigimg" src="/files/ftp_upload/58235/58235fig13.jpg" /> 
Figure 13. Summary of mechanical and chemical wear of Al thin film during tribocorrosion test at 200 mV above OCP.&#160;<a href="https://www.jove.com/files/ftp_upload/58235/58235fig13large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

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Determining Tribocorrosion Rate and Wear-Corrosion Synergy of Bulk and Thin Film Aluminum Alloys

Here, we present a protocol to measure the tribocorrosion rate and wear-corrosion synergy of thin film and bulk Al alloys in simulated sea water at room temperature.

The increasing complexity and severity of service conditions in areas, such as aerospace and marine industries, nuclear systems, microelectronics, ...

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11.2K Views.  University of South Florida. Here, we present a protocol to measure the tribocorrosion rate and wear-corrosion synergy of thin film and bulk Al alloys in simulated sea water at room temperature.

Video: Determining Tribocorrosion Rate and Wear-Corrosion Synergy of Bulk and Thin Film Aluminum Alloys

Polycrystalline Silicon Thin-film Solar cells with Plasmonic-enhanced Light-trapping

One of major approaches to cheaper solar cells is reducing the amount of semiconductor material used for their fabrication and making cells thinner. To compensate for lower light absorption such physically thin devices have to incorporate light-trapping which increases their optical thickness. Light scattering by textured surfaces is a common technique but it cannot be universally applied to all solar cell technologies. Some cells, for example those made of evaporated silicon, are planar as produced and they require an alternative light-trapping means suitable for planar devices. Metal nanoparticles formed on planar silicon cell surface and capable of light scattering due to surface plasmon resonance is an effective approach.
The paper presents a fabrication procedure of evaporated polycrystalline silicon solar cells with plasmonic light-trapping and demonstrates how the cell quantum efficiency improves due to presence of metal nanoparticles.
To fabricate the cells a film consisting of alternative boron and phosphorous doped silicon layers is deposited on glass substrate by electron beam evaporation. An Initially amorphous film is crystallised and electronic defects are mitigated by annealing and hydrogen passivation. Metal grid contacts are applied to the layers of opposite polarity to extract electricity generated by the cell. Typically, such a ~2 &mu;m thick cell has a short-circuit current density (Jsc) of 14-16 mA/cm2, which can be increased up to 17-18 mA/cm2 (~25% higher) after application of a simple diffuse back reflector made of a white paint.
To implement plasmonic light-trapping a silver nanoparticle array is formed on the metallised cell silicon surface. A precursor silver film is deposited on the cell by thermal evaporation and annealed at 23&deg;C to form silver nanoparticles. Nanoparticle size and coverage, which affect plasmonic light-scattering, can be tuned for enhanced cell performance by varying the precursor film thickness and its annealing conditions. An optimised nanoparticle array alone results in cell Jsc enhancement of about 28%, similar to the effect of the diffuse reflector. The photocurrent can be further increased by coating the nanoparticles by a low refractive index dielectric, like MgF2, and applying the diffused reflector. The complete plasmonic cell structure comprises the polycrystalline silicon film, a silver nanoparticle array, a layer of MgF2, and a diffuse reflector. The Jsc for such cell is 21-23 mA/cm2, up to 45% higher than Jsc of the original cell without light-trapping or ~25% higher than Jsc for the cell with the diffuse reflector only.
Introduction
Light-trapping in silicon solar cells is commonly achieved via light scattering at textured interfaces. Scattered light travels through a cell at oblique angles for a longer distance and when such angles exceed the critical angle at the cell interfaces the light is permanently trapped in the cell by total internal reflection (Animation 1: Light-trapping). Although this scheme works well for most solar cells, there are developing technologies where ultra-thin Si layers are produced planar (e.g. layer-transfer technologies and epitaxial c-Si layers) 1 and or when such layers are not compatible with textures substrates (e.g. evaporated silicon) 2. For such originally planar Si layer alternative light trapping approaches, such as diffuse white paint reflector 3, silicon plasma texturing 4 or high refractive index nanoparticle reflector 5 have been suggested.
Metal nanoparticles can effectively scatter incident light into a higher refractive index material, like silicon, due to the surface plasmon resonance effect 6. They also can be easily formed on the planar silicon cell surface thus offering a light-trapping approach alternative to texturing. For a nanoparticle located at the air-silicon interface the scattered light fraction coupled into silicon exceeds 95% and a large faction of that light is scattered at angles above critical providing nearly ideal light-trapping condition (Animation 2: Plasmons on NP). The resonance can be tuned to the wavelength region, which is most important for a particular cell material and design, by varying the nanoparticle average size, surface coverage and local dielectric environment 6,7. Theoretical design principles of plasmonic nanoparticle solar cells have been suggested 8. In practice, Ag nanoparticle array is an ideal light-trapping partner for poly-Si thin-film solar cells because most of these design principle are naturally met. The simplest way of forming nanoparticles by thermal annealing of a thin precursor Ag film results in a random array with a relatively wide size and shape distribution, which is particularly suitable for light-trapping because such an array has a wide resonance peak, covering the wavelength range of 700-900 nm, important for poly-Si solar cell performance. The nanoparticle array can only be located on the rear poly-Si cell surface thus avoiding destructive interference between incident and scattered light which occurs for front-located nanoparticles 9. Moreover, poly-Si thin-film cells do not requires a passivating layer and the flat base-shaped nanoparticles (that naturally result from thermal annealing of a metal film) can be directly placed on silicon further increases plasmonic scattering efficiency due to surface plasmon-polariton resonance 10.
The cell with the plasmonic nanoparticle array as described above can have a photocurrent about 28% higher than the original cell. However, the array still transmits a significant amount of light which escapes through the rear of the cell and does not contribute into the current. This loss can be mitigated by adding a rear reflector to allow catching transmitted light and re-directing it back to the cell. Providing sufficient distance between the reflector and the nanoparticles (a few hundred nanometers) the reflected light will then experience one more plasmonic scattering event while passing through the nanoparticle array on re-entering the cell and the reflector itself can be made diffuse - both effects further facilitating light scattering and hence light-trapping. Importantly, the Ag nanoparticles have to be encapsulated with an inert and low refractive index dielectric, like MgF2 or SiO2, from the rear reflector to avoid mechanical and chemical damage 7. Low refractive index for this cladding layer is required to maintain a high coupling fraction into silicon and larger scattering angles, which are ensured by the high optical contrast between the media on both sides of the nanoparticle, silicon and dielectric 6. The photocurrent of the plasmonic cell with the diffuse rear reflector can be up to 45% higher than the current of the original cell or up to 25% higher than the current of an equivalent cell with the diffuse reflector only.

Polycrystalline silicon thin-film solar cells on glass are fabricated by deposition of boron and phosphorous doped silicon layers followed by crystallisation, defect passivation and metallisation. Plasmonic light-trapping is introduced by forming Ag nanoparticles on the silicon cell surface capped with a diffused reflector resulting in ~45% photocurrent enhancement.

One of major approaches to cheaper solar cells is reducing the amount of semiconductor material used for their fabrication and making cells thinner. To ...

Nanomoulding of Functional Materials, a Versatile Complementary Pattern Replication Method to Nanoimprinting

We describe a nanomoulding technique which allows low-cost nanoscale patterning of functional materials, materials stacks and full devices. Nanomoulding combined with layer transfer enables the replication of arbitrary surface patterns from a master structure onto the functional material. Nanomoulding can be performed on any nanoimprinting setup and can be applied to a wide range of materials and deposition processes. In particular we demonstrate the fabrication of patterned transparent zinc oxide electrodes for light trapping applications in solar cells.

We describe a nanomoulding technique which allows low-cost nanoscale patterning of functional materials, materials stacks and full devices. Nanomoulding can be performed on any nanoimprinting setup and can be applied to a wide range of materials and deposition processes.

We describe a nanomoulding technique which  allows low-cost nanoscale patterning of functional materials, materials stacks  and full devices. Nanomoulding ...

Synthesis and Characterization of High c-axis ZnO Thin Film by Plasma Enhanced Chemical Vapor Deposition System and its UV Photodetector Application

In this study, zinc oxide (ZnO) thin films with high c-axis (0002) preferential orientation have been successfully and effectively synthesized onto silicon (Si) substrates via different synthesized temperatures by using plasma enhanced chemical vapor deposition (PECVD) system. The effects of different synthesized temperatures on the crystal structure, surface morphologies and optical properties have been investigated. The X-ray diffraction (XRD) patterns indicated that the intensity of (0002) diffraction peak became stronger with increasing synthesized temperature until 400 oC. The diffraction intensity of (0002) peak gradually became weaker accompanying with appearance of (10-10) diffraction peak as the synthesized temperature up to excess of 400 oC. The RT photoluminescence (PL) spectra exhibited a strong near-band-edge (NBE) emission observed at around 375 nm and a negligible deep-level (DL) emission located at around 575 nm under high c-axis ZnO thin films. Field emission scanning electron microscopy (FE-SEM) images revealed the homogeneous surface and with small grain size distribution. The ZnO thin films have also been synthesized onto glass substrates under the same parameters for measuring the transmittance.
For the purpose of ultraviolet (UV) photodetector application, the interdigitated platinum (Pt) thin film (thickness ~100 nm) fabricated via conventional optical lithography process and radio frequency (RF) magnetron sputtering. In order to reach Ohmic contact, the device was annealed in argon circumstances at 450 oC by rapid thermal annealing (RTA) system for 10 min. After the systematic measurements, the current-voltage (I-V) curve of photo and dark current and time-dependent photocurrent response results exhibited a good responsivity and reliability, indicating that the high c-axis ZnO thin film is a suitable sensing layer for UV photodetector application.

We offered a method to directly synthesize high c-axis (0002) ZnO thin film by plasma enhanced chemical vapor deposition. The as-synthesized ZnO thin film combined with Pt interdigitated electrode was used as sensing layer for ultraviolet photodetector, showing a high performance through a combination of its good responsivity and reliability.

In this study, zinc oxide (ZnO) thin films with high c-axis (0002) preferential orientation have been successfully and effectively synthesized onto ...

Iridium Oxide-reduced Graphene Oxide Nanohybrid Thin Film Modified Screen-printed Electrodes as Disposable Electrochemical Paper Microfluidic pH Sensors

A facile, controllable, inexpensive and green electrochemical synthesis of IrO2-graphene nanohybrid thin films is developed to fabricate an easy-to-use integrated paper microfluidic electrochemical pH sensor for resource-limited settings. Taking advantages from both pH meters and strips, the pH sensing platform is composed of hydrophobic barrier-patterned paper micropad (&#181;PAD) using polydimethylsiloxane (PDMS), screen-printed electrode (SPE) modified with IrO2-graphene films and molded acrylonitrile butadiene styrene (ABS) plastic holder. Repetitive cathodic potential cycling was employed for graphene oxide (GO) reduction which can completely remove electrochemically unstable oxygenated groups and generate a 2D defect-free homogeneous graphene thin film with excellent stability and electronic properties. A uniform and smooth IrO2 film in nanoscale grain size is anodically electrodeposited onto the graphene film, without any observable cracks. The resulting IrO2-RGO electrode showed slightly super-Nernstian responses from pH 2-12 in Britton-Robinson (B-R) buffers with good linearity, small hysteresis, low response time and reproducibility in different buffers, as well as low sensitivities to different interfering ionic species and dissolved oxygen. A simple portable digital pH meter is fabricated, whose signal is measured with a multimeter, using high input-impedance operational amplifier and consumer batteries. The pH values measured with the portable electrochemical paper-microfluidic pH sensors were consistent with those measured using a commercial laboratory pH meter with a glass electrode.

The study demonstrates the growth of iridium oxide-reduced graphene oxide (IrO2-RGO) nanohybrid thin films on irregular and rough screen-printed carbon substrate through a green electrochemical synthesis, and their implementation as a pH sensor with a patterned paper-fluidic platform.

A facile, controllable, inexpensive and green electrochemical synthesis of IrO2-graphene nanohybrid thin films is developed to fabricate an easy-to-use ...

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices have used devices prepared by spin coating, a process that is not amenable to large-scale fabrication. This mismatch in device fabrication makes it difficult to translate quantitative results obtained in the laboratory to the commercial level, making optimization difficult. Using a mini-slot die coater, this mismatch can be resolved by translating the commercial process to the laboratory and characterizing the structure formation in the active layer of the device in real time and in situ as films are coated onto a substrate. The evolution of the morphology was characterized under different conditions, allowing us to propose a mechanism by which the structures form and grow. This mini-slot die coater offers a simple, convenient, material efficient route by which the morphology in the active layer can be optimized under industrially relevant conditions. The goal of this protocol is to show experimental details of how a solar cell device is fabricated using a mini-slot die coater and technical details of running in situ structure characterization using the mini-slot die coater.

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Here, we present a protocol to fabricate organic thin film solar cells using a mini-slot die coater and related in-line structure characterizations using synchrotron scattering techniques.

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices ...

Reaction Kinetics and Combustion Dynamics of I4O9 and Aluminum Mixtures

Tetraiodine nonoxide (I4O9) has been synthesized using a dry approach that combines elemental oxygen and iodine without the introduction of hydrated species. The synthesis approach inhibits the topochemical effect promoting rapid hydration when exposed to the relative humidity of ambient air. This stable, amorphous, nano-particle material was analyzed using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) and showed an exothermic energy release at low temperature (i.e., 180 &#176;C) for the transformation of I4O9 into I2O5. This additional exothermic energy release contributes to an increase in overall reactivity of I4O9 when dry mixed with nano-aluminum (Al) powder, resulting in a minimum of 150% increase in flame speed compared to Al + I2O5. This study shows that as an oxidizer, I4O9 has more reactive potential than other forms of iodine(V) oxide when combined with Al, especially if I4O9 can be passivated to inhibit absorption of water from its surrounding environment.

Reaction Kinetics and Combustion Dynamics of I4O9 and Aluminum Mixtures

A protocol for measuring flame speeds of a reactive mixture composed of tetraiodine nonoxide (I4O9) and aluminum (Al) is presented. A method for resolving reaction kinetics using differential scanning calorimetry (DSC) is also presented. It was found that I4O9 is 150% more reactive than other iodine(V) oxides.

Tetraiodine nonoxide (I4O9) has been synthesized using a dry approach that combines elemental oxygen and iodine without the introduction of hydrated ...

Experimental Procedure for Warm Spinning of Cast Aluminum Components

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to improve material properties. With a wide array of processing parameters which can affect both the shape attained and resulting material properties, this type of processing is notoriously difficult to commission. A simplified, light-duty version of the process has been designed and implemented for full-size automotive wheels. The apparatus is intended to assist in understanding the deformation mechanisms and the material response to this type of processing. An experimental protocol has been developed to prepare for, and subsequently perform forming trials and is described for as-cast A356 wheel blanks. The thermal profile attained, along with instrumentation details are provided. Similitude with full-scale forming operations which impart significantly more deformation at faster rates is discussed.

An experimental protocol for instrumented warm rotary forming of cast aluminum alloys employing a bespoke industrially scaled apparatus is presented. Experimental considerations including thermal and mechanical effects are discussed, as well as similitude with full-scale processing of automotive wheels.

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to ...

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 ...

In Situ Monitoring of the Accelerated Performance Degradation of Solar Cells and Modules: A Case Study for Cu(In,Ga)Se2 Solar Cells

The levelized cost of electricity (LCOE) of photovoltaic (PV) systems is determined by, among other factors, the PV module reliability. Better prediction of degradation mechanisms and prevention of module field failure can consequently decrease investment risks as well as increase the electricity yield. An improved knowledge level can for these reasons significantly decrease the total costs of PV electricity. 
In order to better understand and minimize the degradation of PV modules, the occurring degradation mechanisms and conditions should be identified. This should preferably happen under combined stresses, since modules in the field are also simultaneously exposed to multiple stress factors. Therefore, two 'Combined Stress test with in situ measurement' setups have been designed and constructed. These setups allow the simultaneous use of humidity, temperature, illumination, and electrical biases as independently controlled stress factors on solar cells and minimodules. The setups also allow real-time monitoring of the electrical properties of these samples. This protocol presents these setups and describes the experimental possibilities. Moreover, results obtained with these setups are also presented: various examples about the influence of both deposition and degradation conditions on the stability of thin film Cu(In,Ga)Se2 (CIGS) as well as Cu2ZnSnSe4 (CZTS) solar cells are described. Results on the temperature dependency of CIGS solar cells are also presented.

In Situ Monitoring of the Accelerated Performance Degradation of Solar Cells and Modules: A Case Study for CuIn,GaSe2 Solar Cells

Two &#39;Combined Stress test with in situ measurement&#39; setups, which allow real-time monitoring of accelerated degradation of solar cells and modules, were designed and constructed. These setups allow the simultaneous use of humidity, temperature, electrical biases, and illumination as independently controlled stress factors. The setups and various experiments executed are presented.

The levelized cost of electricity (LCOE) of photovoltaic (PV) systems is determined by, among other factors, the PV module reliability. Better prediction ...

Simultaneous Multi-surface Anodizations and Stair-like Reverse Biases Detachment of Anodic Aluminum Oxides in Sulfuric and Oxalic Acid Electrolyte

After reporting on the two-step anodization, nanoporous anodic aluminum oxides (AAOs) have been widely utilized in the versatile fields of fundamental sciences and industrial applications owing to their periodic arrangement of nanopores with relatively high aspect ratio. However, the techniques reported so far, which could be only valid for mono-surface anodization, show critical disadvantages, i.e., time-consuming as well as complicated procedures, requiring toxic chemicals, and wasting valuable natural resources. In this paper, we demonstrate a facile, efficient, and environmentally clean method to fabricate nanoporous AAOs in sulfuric and oxalic acid electrolytes, which can overcome the limitations that result from conventional AAO fabricating methods. First, plural AAOs are produced at one time through simultaneous multi-surfaces anodization (SMSA), indicating mass-producibility of the AAOs with comparable qualities. Second, those AAOs can be separated from the aluminum (Al) substrate by applying stair-like reverse biases (SRBs) in the same electrolyte used for the SMSAs, implying simplicity and green technological characteristics. Finally, a unit sequence consisting of the SMSAs sequentially combined with SRBs-based detachment can be applied repeatedly to the same Al substrate, which reinforces the advantages of this strategy and also guarantees the efficient usage of natural resources.

A protocol for fabricating nanoporous anodic aluminum oxides via simultaneous multi-surfaces anodization followed by stair-like reverse biases detachments is presented. It can be applied repeatedly to the same aluminum substrate, exhibiting a facile, high-yield, and environmentally clean strategy.

After reporting on the two-step anodization, nanoporous anodic aluminum oxides (AAOs) have been widely utilized in the versatile fields of fundamental ...