This work was financially supported in part by The Light Metal Educational Foundation, Inc., Osaka, Japan

1. Material preparation
<ol>
	<li>Use 1 mm thick plates made of an aluminum-magnesium-silicon alloy containing 1 mass% Mg and 0.8 mass% Si (Al-Mg-Si).</li>
	<li>Make test pieces from the Al-Mg-Si alloy plates having a gauge length of 10 mm and width of 5 mm.</li>
	<li>Anneal the test pieces at 520 &#730;C for 1 h using an air furnace. Quench in water as a solution heat treatment.</li>
	<li>Anneal the test pieces at 175 &#730;C for 18 h as a peak aging heat treatment (T6-temper).</li>
	<li>Polish the surface of the test pieces using silicon carbide emery paper (#2000) without water.</li>
	<li>Measure the weight of the polished specimens to a precision of 0.0001 g using an electric balance</li>
	<li>Measure the thickness and width of the gauge part of the specimens to a precision of 0.001 mm using an optical comparator.</li>
</ol>
2. FW procedure (Figure 1)
<ol>
	<li>Attach two Al-Mg-Si alloy specimens using glue to a triangular, prism-shaped stirrer made by a fluorocarbon polymer.</li>
	<li>Prepare a cylinder glass container with an empty top as a reaction vessel.</li>
	<li>Attach a round polishing paper made by silicon carbides, #2000 with a diameter of 10 mm, using double sided tape in the bottom inside of the container.</li>
	<li>Place the triangular, prism-shaped stirrer with two specimens on the polishing paper at the bottom surface of the glass container.</li>
	<li>Pour 100 mL of distilled water into the glass container from the top.</li>
	<li>Cover the glass container with a round rubber piece with three holes (for a gas inlet, for a gas outlet, and for a pH probe at the top of the glass container).</li>
	<li>Fill the glass container with high purity (99.999%) argon at a constant flow rate of 20 mL/min after closing the rubber cover.</li>
	<li>Connect the gas outlet to a gas chromatograph (GC) with a semiconductor hydrogen sensor (detection limit: 5 ppb).</li>
	<li>Wait until the gas in the container is replaced by argon.</li>
	<li>Rotate the triangular, prism-shaped stirrer with two specimens on a magnetic stirrer with a constant rotating speed at room temperature.</li>
	<li>Measure the hydrogen generation during the stirrer rotation using the GC, taking one measurement every 2 min.</li>
	<li>Measure the pH of the water in the container during the stirrer rotation.</li>
	<li>Remove the two specimens from the triangular, prism-shaped stirrer by immersion in acetone with an ultrasonic vibration for 5 min after the FW procedure.</li>
	<li>Measure the weight and thickness of the specimens again after the FW procedure using the electric balance and an optical comparator, respectively.</li>
</ol>
3. Hydrogen absorption by the FW procedure
<ol>
	<li>After the FW procedure, cut a specimen to a rectangular shape of 1 x 5 x 10 mm.</li>
	<li>Place the specimen inside a quartz tube with a diameter of 10 mm connected to a GC with a semiconductor hydrogen sensor.</li>
	<li>Flow high purity (99.999%) argon gas in a quartz tube with a constant flow rate of 20 mL/min.</li>
	<li>Heat the quartz tube with the specimen using a tubular furnace at a constant heating rate, 200 &#730;C/h.</li>
	<li>Measure the thermal hydrogen desorption of the specimen after the FW procedure using the GC.</li>
</ol>
4. Material evaluation after the FW procedure
<ol>
	<li>Carry out tensile tests (at least 3x, to ensure repeatability) in laboratory air with a crosshead speed of 2 mm/min using a specimen that has been treated by the FW procedure.</li>
	<li>Measure the tensile properties (e.g., tensile strength, fracture strain) obtained from the stress-strain curve in the tensile test.</li>
	<li>Observe the fracture behavior with a secondary electron microscope (SEM) after the tensile test.</li>
</ol>

<ol>
	<li>Horikawa, K., Matsubara, T., Kobayashi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogen+charging+of+Al-Mg-Si-based+alloys+by+friction+in+water+and+its+effect+on+tensile+properties.">Hydrogen charging of Al-Mg-Si-based alloys by friction in water and its effect on tensile properties.</a> Materials Science and Engineering A. 764, 138199 (2019).</li><li>Horikawa, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Current+research+trends+in+aluminum+alloys+for+a+high-pressure+hydrogen+gas+container.">Current research trends in aluminum alloys for a high-pressure hydrogen gas container.</a> Journal of Japan Institute of Light Metals. 60, 542-547 (2010).</li><li>Kuramoto, S., Hsieh, M. C., Kanno, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Environmental+embrittlement+of+Al-Mg-Si+base+alloys+deformed+at+low+strain+rates+in+laboratory+air.">Environmental embrittlement of Al-Mg-Si base alloys deformed at low strain rates in laboratory air.</a> Journal of Japan Institute of Light Metals. 52, 250-255 (2002).</li><li>Horikawa, K., Yoshida, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualization+of+Hydrogen+in+Tensile-Deformed+Al-5%Mg+Alloy+by+means+of+Hydrogen+Microprint+Technique+with+EBSP+Analysis.">Visualization of Hydrogen in Tensile-Deformed Al-5%Mg Alloy by means of Hydrogen Microprint Technique with EBSP Analysis.</a> Materials Transactions. 45, 315-318 (2004).</li><li>Ueda, K., Horikawa, K., Kanno, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Suppression+of+high+temperature+embrittlement+of+Al-5%Mg+alloys+containing+a+trace+of+sodium+caused+by+antimony+addition.">Suppression of high temperature embrittlement of Al-5%Mg alloys containing a trace of sodium caused by antimony addition.</a> Scripta Materialia. 37, 1105-1110 (1996).</li><li>Horikawa, K., Ando, N., Kobayashi, H., Urushihara, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualization+of+hydrogen+gas+evolution+during+deformation+and+fracture+in+SCM+440+steel+with+different+tempering+conditions.">Visualization of hydrogen gas evolution during deformation and fracture in SCM 440 steel with different tempering conditions.</a> Materials Science and Engineering A. 534, 495-503 (2012).</li><li>Horikawa, K., Yamada, H., Kobayashi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+strain+rate+on+hydrogen+gas+evolution+behavior+during+tensile+deformation+in+6061+and+7075+aluminum+alloys.">Effect of strain rate on hydrogen gas evolution behavior during tensile deformation in 6061 and 7075 aluminum alloys.</a> Journal of Japan Institute of Light Metals. 62, 306-312 (2012).</li><li>Horikawa, K., Okada, H., Kobayashi, H., Urushihara, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualization+of+diffusive+hydrogen+in+low+alloy+steel+by+means+of+hydrogen+microprint+technique+at+elevated+temperatures.">Visualization of diffusive hydrogen in low alloy steel by means of hydrogen microprint technique at elevated temperatures.</a> Materials Transactions. 50, 759-764 (2009).</li><li>Horikawa, K., Okada, H., Kobayashi, H., Urushihara, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualization+of+hydrogen+during+fatigue+fracture+in+an+Al-Mg-Si+alloy.">Visualization of hydrogen during fatigue fracture in an Al-Mg-Si alloy.</a> Journal of Japan Institute of Light Metals. 56, 210-213 (2006).</li><li>Horikawa, K., Okada, H., Kobayashi, H., Urushihara, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualization+of+hydrogen+distribution+in+tensile-deformed+Al-5%Mg+alloy+investigated+by+means+of+hydrogen+microprint+technique+with+EBSP.">Visualization of hydrogen distribution in tensile-deformed Al-5%Mg alloy investigated by means of hydrogen microprint technique with EBSP.</a> Journal of the Japan Institute of Metals. 68, 1043-1046 (2004).</li><li>Yamada, H., Tsurudome, M., Miura, N., Horikawa, K., Ogasawara, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ductility+loss+of+7075+aluminum+alloys+affected+by+interaction+of+hydrogen,+fatigue+deformation,+and+strain+rate.">Ductility loss of 7075 aluminum alloys affected by interaction of hydrogen, fatigue deformation, and strain rate.</a> Materials Science and Engineering A. 642, 194-203 (2015).</li><li>Toda, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+hydrogen+micro+pores+on+mechanical+properties+in+a+2024+aluminum+alloys.">Effects of hydrogen micro pores on mechanical properties in a 2024 aluminum alloys.</a> Materials Transactions. 54, 2195-2201 (2013).</li><li>Yamada, H., Horikawa, K., Matsumoto, T., Kobayashi, H., Ogasawara, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogen+evolution+behavior+of+tensile+deformation+process+in+6061+and+7075+aluminum+alloys.">Hydrogen evolution behavior of tensile deformation process in 6061 and 7075 aluminum alloys.</a> Journal of Japan Institute of Light Metals. 61, 297-302 (2011).</li><li>Horikawa, K., Kobayashi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogen+absorption+of+pure+aluminum+by+friction+of+the+surface+in+water+and+its+effect+on+tensile+properties.">Hydrogen absorption of pure aluminum by friction of the surface in water and its effect on tensile properties.</a> Journal of the Japan Institute of Metals. 84, (2020).</li><li>Suzuki, H., Kobayashi, D., Hanada, N., Takai, K., Hagihara, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Existing+state+of+hydrogen+in+electrochemically+charged+commercial-purity+aluminum+and+its+effects+on+tensile+properties.">Existing state of hydrogen in electrochemically charged commercial-purity aluminum and its effects on tensile properties.</a> Materials Transactions. 52, 1741-1747 (2011).</li><li>Horikawa, K., Hokazono, S., Kobayashi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synchronized+monitoring+between+hydrogen+gas+release+and+progress+of+atmospheric+hydrogen+embrittlement+in+7075+aluminum+alloy.">Synchronized monitoring between hydrogen gas release and progress of atmospheric hydrogen embrittlement in 7075 aluminum alloy.</a> Journal of Japan Institute of Light Metals. 66, 77-83 (2016).</li><li>Manaka, T., Aoki, M., Itoh, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+desorption+spectroscopy+study+on+the+hydrogen+behavior+in+a+plasma-charged+aluminum.">Thermal desorption spectroscopy study on the hydrogen behavior in a plasma-charged aluminum.</a> Materials Science Forum. 879, 1220-1225 (2016).</li><li>Ellingham, H. J. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reducibility+of+oxides+and+sulphides+in+metallurgical+processes.">Reducibility of oxides and sulphides in metallurgical processes.</a> Journal of the Society of Chemical Industry. 63, 125-133 (1944).</li><li>Pourbaix, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Atlas of electrochemical equilibria in aqueous solutions, Ist ed. , 168-176 (1966).</li><li>Young, G. A., Scully, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+diffusion+and+trapping+of+hydrogen+in+high+purity+aluminum.">The diffusion and trapping of hydrogen in high purity aluminum.</a> Acta Materialia. 46, 6337-6349 (1998).</li><li>Smith, S. W., Scully, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+identification+of+hydrogen+trapping+states+in+an+Al-Li-Cu-Zr+alloy+using+thermal+desorption+spectroscopy.">The identification of hydrogen trapping states in an Al-Li-Cu-Zr alloy using thermal desorption spectroscopy.</a> Metallurgical and Materials Transactions A. 31, 179-193 (2000).</li></ol>

The authors have nothing to disclose.

One important aspect of the FW procedure is the attachment of the two specimens to the magnetic stirrer. Because the center of the stirrer bar becomes the non-friction zone, it is best to avoid the attachment of the specimens at the center of the stirrer bar.
Control of the rotation speed of the stirrer bar is also important. When the speed is more than 240 rpm, it becomes difficult to maintain the reaction vessel on the stage of the magnetic stirrer. When the FW procedure is carried out at high speed, fixing the reaction vessel to the stage of the magnetic stirrer is needed.
Because the hydrogen charging by the FW procedure is based on the chemical reaction between water and a non-oxide coated aluminum surface, this is a simple method when compared to conventional hydrogen charging methods, such as cathodic charging15, pre-strain under a humid air atmosphere16. A theoretical volume of generated hydrogen is calculated based on the change of weight in the sample before and after the FW procedure. Also, the FW procedure can introduce high amounts of hydrogen into aluminum. However, when the time of the FW procedure is longer, the pH value of water increases. When the pH value of water becomes &#62;10, a corrosive reaction between aluminum and water may happen16. To prevent the corrosive reaction of the specimen, the time of the FW procedure should be limited so the pH value of the water solution ranges from 4&#8211;10.
In the FW procedure, the hydrogen charging is applicable basically to the plate shaped aluminum and aluminum alloys. The hydrogen charging in the FW procedure is based on hydrogen entry from one surface of the plate specimen.

In general, aluminum base alloys have higher resistance to environmental hydrogen embrittlement than steel. The high resistance to hydrogen embrittlement of aluminum alloys is due to oxide films on the alloy surface blocking hydrogen entry. To evaluate and compare the high embrittlement sensitivity between aluminum alloys, hydrogen charging is usually performed prior to mechanical testing1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17. However, it is known that hydrogen charging aluminum is not easy, even when utilizing hydrogen charging methods such as cathodic charging15, slow strain rate deformation under humid air16, or hydrogen plasma gas charging17. The difficulty of hydrogen charging aluminum alloys is also due to the oxide films on the aluminum alloy surface. We postulated that higher amounts of hydrogen could be introduced into aluminum alloys if we could remove the oxide film continuously in water. Thermodynamically18, pure aluminum without oxide film reacts easily with water and generates hydrogen. Based on this, we have developed a new method of hydrogen charging of aluminum alloys based on the chemical reaction between water and non-oxide aluminum. This method is able to add high amounts of hydrogen into aluminum alloys in a simple way.

<table><tbody><tr><td>Air furnace</td><td>GC</td><td>QC-1</td><td></td></tr><tr><td>Aluminum alloy plates</td><td>Kobe Steel</td><td></td><td>Al/1.0 mass% Mg/0.8 mass% Si</td></tr><tr><td>Electric balance</td><td>A&amp;amp;D</td><td>HR-200</td><td></td></tr><tr><td>Glass container</td><td></td><td></td><td>Custom made</td></tr><tr><td>Magnetic stirrer</td><td>CORNING</td><td>PC-410D</td><td></td></tr><tr><td>Optical Comparator</td><td>NIKON</td><td>V-12B</td><td></td></tr><tr><td>pH meter</td><td>Sato Tech</td><td>PH-230SDJ</td><td></td></tr><tr><td>Quartz tube</td><td></td><td></td><td>Custom made</td></tr><tr><td>Rotary polishing machine</td><td>IMT</td><td>IM-P2</td><td></td></tr><tr><td>Secondary electrom microscope</td><td>JOEL</td><td>JSM-5310LV</td><td></td></tr><tr><td>Sensor gas chromatograph</td><td>FIS Inc.</td><td>SGHA</td><td></td></tr><tr><td>Silicon carbide emery paper</td><td>IMT</td><td>531SR</td><td></td></tr><tr><td>Tensile testing machine</td><td>Toshin Kogyo</td><td>SERT-5000-C</td><td></td></tr><tr><td>Tubular furnace</td><td>Honma Riken</td><td></td><td>Custom made</td></tr></tbody></table>

hydrogen charging of aluminum using friction in water

A new method of hydrogen charging of aluminum was developed by means of a friction in water (FW) procedure. This procedure can easily introduce high amounts of hydrogen into aluminum based on the chemical reaction between water and non-oxide coated aluminum.

Hydrogen generation/absorption by the FW procedure 
Figure 2 shows the hydrogen generation behavior during the FW procedure of Al-Mg-Si alloys containing different amounts of iron from 0.1 mass % to 0.7 mass %. The specimen continuously emitted a high amount of hydrogen when the stirrer started to rotate. This suggests that hydrogen was generated by a chemical reaction caused by the friction between the alloy surface and water. In addition, the pH value of the water during the FW procedure increased slightly from 6.5&#8211;7.5 as shown in Figure 3. The change in pH by the FW procedure would not affect the corrosive reaction based on the electrochemical diagram proposed by Pourbaix19.
Figure 4 shows the TDA results in samples with and without hydrogen charging by the FW procedure of the Al-Mg-Si alloys. Regardless of the alloy composition of the specimen, the total hydrogen concentration after the FW procedure increased compared to the original uncharged state. In all samples after the FW procedure, hydrogen evolution occurred at above 400 &#176;C. A small peak of hydrogen evolution was also visible around 300 &#176;C&#8211;400 &#176;C in the hydrogen-charged samples. The hydrogen evolution peak around 300 &#176;C&#8211;400 &#176;C would be related to hydrogen trapping by lattice defects, such as dislocations and grain boundaries20,21. The hydrogen concentration calculated by integrating the hydrogen release rate and the temperature from 25 &#730;C&#8211;625 &#730;C is shown in Figure 5. It is obvious that the hydrogen concentration after the FW procedure increased about 4x from the original state.
Figure 6 shows the comparison of hydrogen concentration between the FW procedure and the hydrogen charging by pre-strain of 0.1 under a humid air atmosphere with a relative humidity of 90% in a 0.1% iron specimen. It is also clear that the hydrogen charging by the FW procedure allowed the introduction of large amounts of hydrogen compared to the charging by pre-strain under humid air.
Mechanical performance after the FW procedure 
Figure 7 shows the tensile test results of both the hydrogen-uncharged samples and hydrogen-charged samples. A decrease in ductility was observed in the Al-Mg-Si alloy with 0.1% iron just after the FW procedure. This indicates that the Al-Mg-Si alloy with 0.1% iron shows hydrogen embrittlement caused by the high amount of hydrogen charging by the FW procedure.
The fracture morphology of the Al-Mg-Si alloy with 0.1% iron changed to a grain boundary fracture after the hydrogen charging by the FW procedure, particularly adjacent to the hydrogen entry side as shown in Figure 8. This indicates that hydrogen atoms introduced by the FW procedure enhance the decohesion of grain boundaries, which leads to hydrogen embrittlement, in the Al-Mg-Si alloy with 0.1% iron.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/60711/60711fig01.jpg" /> 
Figure 1: Schematic of the apparatus used in the FW procedure. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/60711/60711fig1large.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/60711/60711fig02.jpg" /> 
Figure 2: Hydrogen generation during the FW procedure. (A) 0.1% Fe, (B) 0.2% Fe, (C) 0.7% Fe. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/60711/60711fig2large.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/60711/60711fig03.jpg" /> 
Figure 3: Change of pH during the FW procedure. (A) 0.1% Fe, (B) 0.2% Fe, (C) 0.7% Fe. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/60711/60711fig3large.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/60711/60711fig04.jpg" /> 
Figure 4: Thermal hydrogen desorption analysis of Al-Mg-Si alloys with iron. (A) 0.1 Fe, (B) 0.2% Fe, (C) 0.7% Fe. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/60711/60711fig4large.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/60711/60711fig05.jpg" /> 
Figure 5: Hydrogen concentration with and without the FW procedure. (A) 0.1% Fe, (B) 0.2% Fe, (C) 0.7% Fe. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/60711/60711fig5large.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/60711/60711fig06.jpg" /> 
Figure 6: Comparison of thermal desorption analysis and hydrogen concentration of Al-Mg-Si alloys with 0.1% Fe in different hydrogen charging conditions. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/60711/60711fig6large.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/60711/60711fig07.jpg" /> 
Figure 7: Stress-strain curves of the Al-Mg-Si alloy with 0.1% Fe, before and just after the FW procedure. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/60711/60711fig7large.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/60711/60711fig08.jpg" /> 
Figure 8: Fracture surfaces of an Al-Mg-Si alloy with 0.1% Fe. (A) Before and (B) after the FW procedure, adjacent to the hydrogen entry side. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/60711/60711fig8large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Hydrogen Charging of Aluminum using Friction in Water at JoVE.com

Hydrogen Charging of Aluminum using Friction in Water

In order to introduce high amounts of hydrogen in aluminum and aluminum alloys, a new method of hydrogen charging was developed, called the friction in water procedure.

A new method of hydrogen charging of aluminum was developed by means of a friction in water (FW) procedure. This procedure can easily introduce high ...

hydrogen-charging-of-aluminum-using-friction-in-water

Nanyang Technological University

Research

JoVE Journal

Engineering

5.9K Views.  Osaka University. Bij het opladen van aluminiumlegeringen met waterstof is de aanwezigheid van oxidefolie op het oppervlak een uitdaging. Om dit probleem op te lossen, hebben we een methode ontwikkeld die een grote hoeveelheid waterstof kan introduceren in aluminiumlegeringen met behulp van wrijving in water. De methode is het gemakkelijkst te begrijpen wanneer de rotatie van de roerstaaf en het monster op het polijstpapier kunnen worden gevisualiseerd.Succes hangt af van het stabiliseren van de rotatie...

Video: Hydrogen Charging of Aluminum using Friction in Water

A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where interfacial tension is a dominant force. A variety of methods exist for controlling the interfacial tension of aqueous and organic liquids on this scale; however, these techniques have limited utility for liquid metals due to their large interfacial tension.
Liquid metals can form soft, stretchable, and shape-reconfigurable components in electronic and electromagnetic devices. Although it is possible to manipulate these fluids via mechanical methods (e.g., pumping), electrical methods are easier to miniaturize, control, and implement. However, most electrical techniques have their own constraints: electrowetting-on-dielectric requires large (kV) potentials for modest actuation, electrocapillarity can affect relatively small changes in the interfacial tension, and continuous electrowetting is limited to plugs of the liquid metal in capillaries.
Here, we present a method for actuating gallium and gallium-based liquid metal alloys via an electrochemical surface reaction. Controlling the electrochemical potential on the surface of the liquid metal in electrolyte rapidly and reversibly changes the interfacial tension by over two orders of magnitude ( &#820;500 mN/m to near zero). Furthermore, this method requires only a very modest potential (&#60; 1 V) applied relative to a counter electrode. The resulting change in tension is due primarily to the electrochemical deposition of a surface oxide layer, which acts as a surfactant; removal of the oxide increases the interfacial tension, and vice versa. This technique can be applied in a wide variety of electrolytes and is independent of the substrate on which it rests.

We present a method to control the interfacial energy of a liquid metal in an electrolyte via electrochemical deposition (or removal) of a surface oxide layer. This simple method can control the capillary behavior of gallium-based liquid metals by tuning the interfacial energy rapidly, significantly, and reversibly using modest voltages.

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where ...

Chemistry

A Simple, Low-cost, and Robust System to Measure the Volume of Hydrogen Evolved by Chemical Reactions with Aqueous Solutions

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) hydrogen fuel cells. Researchers seeking to develop such systems require a method of measuring the generated hydrogen. Herein, we describe a simple, low-cost, and robust method to measure the hydrogen generated from the reaction of solids with aqueous solutions. The reactions are conducted in a conventional one-necked round-bottomed flask placed in a temperature controlled water bath. The hydrogen generated from the reaction in the flask is channeled through tubing into a water-filled inverted measuring cylinder. The water displaced from the measuring cylinder by the incoming gas is diverted into a beaker on a balance. The balance is connected to a computer, and the change in the mass reading of the balance over time is recorded using data collection and spreadsheet software programs. The data can then be approximately corrected for water vapor using the method described herein, and parameters such as the total hydrogen yield, the hydrogen generation rate, and the induction period can also be deduced. The size of the measuring cylinder and the resolution of the balance can be changed to adapt the setup to different hydrogen volumes and flow rates.

The study of methods to generate on-demand hydrogen for fuel cells continues to grow in importance. However, systems to measure hydrogen evolution from the reaction of chemicals with water can be complicated and expensive. This article details a simple, low-cost, and robust method to measure the evolution of hydrogen gas.

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) ...

Facile Preparation of Ultrafine Aluminum Hydroxide Particles with or without Mesoporous MCM-41 in Ambient Environments

An aqueous suspension of nanogibbsite was synthesized via the titration of aluminum aqua acid [Al(H2O)6]3+ with L-arginine to pH 4.6. Since the hydrolysis of aqueous aluminum salts is known to produce a wide array of products with a wide range of size distributions, a variety of state-of-the-art instruments (i.e., 27Al/1H NMR, FTIR, ICP-OES, TEM-EDX, XPS, XRD, and BET) were used to characterize the synthesis products and identification of byproducts. The product, which was comprised of nanoparticles (10-30 nm), was isolated using gel permeation chromatography (GPC) column technique. Fourier transform infrared (FTIR) spectroscopy and powder X-ray diffraction (PXRD) identified the purified material as the gibbsite polymorph of aluminum hydroxide. The addition of inorganic salts (e.g., NaCl) induced electrostatic destabilization of the suspension, thereby agglomerating the nanoparticles to yield Al(OH)3 precipitate with large particle sizes. By utilizing the novel synthetic method described here, Al(OH)3 was partially loaded inside the highly ordered mesoporous framework of MCM-41, with average pore dimensions of 2.7 nm, producing an aluminosilicate material with both octahedral and tetrahedral Al (Oh/Td = 1.4). The total Al content, measured using energy-dispersive X-ray spectrometry (EDX), was 11% w/w with a Si/Al molar ratio of 2.9. A comparison of bulk EDX with surface X-ray photoelectron spectroscopy (XPS) elemental analysis provided insight into the distribution of Al within the aluminosilicate material. Furthermore, a higher ratio of Si/Al was observed on the external surface (3.6) as compared to the bulk (2.9). Approximations of O/Al ratios suggest a higher concentration of Al(O)3 and Al(O)4 groups near the core and external surface, respectively. The newly developed synthesis of Al-MCM-41 yields a relatively high Al content while maintaining the integrity of the ordered silica framework and can be used for applications where hydrated or anhydrous Al2O3 nanoparticles are advantageous.

An ultrafine aluminum hydroxide nanoparticle suspension was prepared via the controlled titration of [Al(H2O)]3+ with L-arginine to pH 4.6 with and without cage-effect confinement within mesoporous channels of MCM-41.

An aqueous suspension of nanogibbsite was synthesized via the titration of aluminum aqua acid [Al(H2O)6]3+ with L-arginine to pH 4.6. Since the hydrolysis ...

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 ...

In Situ High Pressure Hydrogen Tribological Testing of Common Polymer Materials Used in the Hydrogen Delivery Infrastructure

High pressure hydrogen gas is known to adversely affect metallic components of compressors, valves, hoses, and actuators. However, relatively little is known about the effects of high pressure hydrogen on the polymer sealing and barrier materials also found within these components. More study is required in order to determine the compatibility of common polymer materials found in the components of the hydrogen fuel delivery infrastructure with high pressure hydrogen. As a result, it is important to consider the changes in physical properties such as friction and wear in situ while the polymer is exposed to high pressure hydrogen. In this protocol, we present a method for testing the friction and wear properties of ethylene propylene diene monomer (EPDM) elastomer samples in a 28 MPa high pressure hydrogen environment using a custom-built in situ pin-on-flat linear reciprocating tribometer. Representative results from this testing are presented which indicate that the coefficient of friction between the EPDM sample coupon and steel counter surface is increased in high pressure hydrogen as compared to the coefficient of friction similarly measured in ambient air.

In Situ High Pressure Hydrogen Tribological Testing of Common Polymer Materials Used in the Hydrogen Delivery Infrastructure

A test methodology for quantifying tribological properties of polymers used in hydrogen infrastructure service is demonstrated and characteristic results for a common elastomer are discussed.

High pressure hydrogen gas is known to adversely affect metallic components of compressors, valves, hoses, and actuators. However, relatively little is ...

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.

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, ...

Experimental Methods for Efficient Solar Hydrogen Production in Microgravity Environment

Long-term space flights and cis-lunar research platforms require a sustainable and light life-support hardware which can be reliably employed outside the Earth's atmosphere. So-called 'solar fuel' devices, currently developed for terrestrial applications in the quest for realizing a sustainable energy economy on Earth, provide promising alternative systems to existing air-revitalization units employed on the International Space Station (ISS) through photoelectrochemical water-splitting and hydrogen production. One obstacle for water (photo-) electrolysis in reduced gravity environments is the absence of buoyancy and the consequential, hindered gas bubble release from the electrode surface. This causes the formation of gas bubble froth layers in proximity to the electrode surface, leading to an increase in ohmic resistance and cell-efficiency loss due to reduced mass transfer of substrates and products to and from the electrode. Recently, we have demonstrated efficient solar hydrogen production in microgravity environment, using an integrated semiconductor-electrocatalyst system with p-type indium phosphide as the light-absorber and a rhodium electrocatalyst. By nanostructuring the electrocatalyst using shadow nanosphere lithography and thereby creating catalytic 'hot spots' on the photoelectrode surface, we could overcome gas bubble coalescence and mass transfer limitations and demonstrated efficient hydrogen production at high current densities in reduced gravitation. Here, the experimental details are described for the preparations of these nanostructured devices and further on, the procedure for their testing in microgravity environment, realized at the Bremen Drop Tower during 9.3 s of free fall.

Efficient solar-hydrogen production has recently been realized on functionalized semiconductor-electrocatalyst systems in a photoelectrochemical half-cell in microgravity environment at the Bremen Drop Tower. Here, we report the experimental procedures for manufacturing the semiconductor-electrocatalyst device, details of the experimental set-up in the drop capsule and the experimental sequence during free fall.

Long-term space flights and cis-lunar research platforms require a sustainable and light life-support hardware which can be reliably employed outside the ...

Hydrogen Production and Utilization in a Membrane Reactor

Industrial hydrogenation consumes ~11 Mt of fossil-derived H2 gas yearly. Our group invented a membrane reactor to bypass the need to use H2 gas for hydrogenation chemistry. The membrane reactor sources hydrogen from water and drives reactions using renewable electricity. In this reactor, a thin piece of Pd separates an electrochemical hydrogen production compartment from a chemical hydrogenation compartment. The Pd in the membrane reactor acts as (i) a hydrogen-selective membrane, (ii) a cathode, and (iii) a catalyst for hydrogenation. Herein, we report the use of atmospheric mass spectrometry (atm-MS) and gas chromatography mass spectrometry (GC-MS) to demonstrate that an applied electrochemical bias across a Pd membrane enables efficient hydrogenation without direct H2 input in a membrane reactor. With atm-MS, we measured a hydrogen permeation of 73%, which enabled the hydrogenation of propiophenone to propylbenzene with 100% selectivity, as measured by GC-MS. In contrast to conventional electrochemical hydrogenation, which is limited to low concentrations of starting material dissolved in a protic electrolyte, the physical separation of hydrogen production from utilization in the membrane reactor enables hydrogenation in any solvent or at any concentration. The use of high concentrations and a wide range of solvents is particularly important for reactor scalability and future commercialization.

Membrane reactors enable hydrogenation in ambient conditions without direct H2 input. We can track the hydrogen production and utilization in these systems using atmospheric mass spectrometry (atm-MS) and gas chromatography mass spectrometry (GC-MS).

Industrial hydrogenation consumes ~11 Mt of fossil-derived H2 gas yearly. Our group invented a membrane reactor to bypass the need to use H2 gas for ...

Exploring Innovative 3D Electrodes for Hydrogen Peroxide Fuel Cells

Membraneless Hydrogen Peroxide Fuel Cells as a Promising Clean Energy Source

In an in-depth investigation of membraneless hydrogen peroxide-based fuel cells (H2O2 FCs), hydrogen peroxide (H2O2), a carbon-neutral compound, is demonstrated to undergo electrochemical decomposition to produce H2O, O2, and electrical energy. The unique redox properties of H2O2 position it as a viable candidate for sustainable energy applications. The proposed membraneless design addresses the limitations of conventional fuel cells, including fabrication complexities and design challenges. A novel three-dimensional electrode, synthesized via electroplating techniques, is introduced. Constructed from Au-electroplated carbon fiber cloth combined with Ni-foam, this electrode showcases enhanced electrochemical reaction kinetics, leading to an increased power density for H2O2 FCs. The performance of fuel cells is intricately linked to the pH levels of the electrolyte solution. Beyond FC applications, such electrodes hold potential in portable energy systems and as high surface area catalysts. This study emphasizes the significance of electrode engineering in optimizing the potential of H2O2 as an environmentally friendly energy source.

Author Spotlight: Design and Evaluation of Au-Electroplated Carbon Fiber Cloth Electrodes for Hydrogen Peroxide Fuel Cells 

This protocol introduces the design and evaluation of innovative three-dimensional electrodes for hydrogen peroxide fuel cells, utilizing Au-electroplated carbon fiber cloth and Ni-foam electrodes. The research findings highlight hydrogen peroxide's potential as a promising candidate for sustainable energy technologies.

In an in-depth investigation of membraneless hydrogen peroxide-based fuel cells (H2O2 FCs), hydrogen peroxide (H2O2), a carbon-neutral compound, is ...

Proton Exchange Membrane Fuel Cells

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University
The United States consumes a large amount of energy &#8211; the current rate is around 97.5 quadrillion BTUs annually. The vast majority (90%) of this energy comes from non-renewable fuel sources. This energy is used for electricity (39%), transportation (28%), industry (22%), and residential/commercial use (11%). As the world has a limited supply of these non-renewable sources, the United States (among others) is expanding the use of renewable energy sources to meet future energy needs. One of these sources is hydrogen.
Hydrogen is considered a potential renewable fuel source, because it meets many important criteria: it&#8217;s available domestically, it has few harmful pollutants, it&#8217;s energy efficient, and it&#8217;s easy to harness. While hydrogen is the most abundant element in the universe, it is only found in compound form on Earth. For example, it is combined with oxygen in water as H2O. To be useful as a fuel, it needs to be in the form of H2 gas. Therefore, if hydrogen is to be used as a fuel for cars or other electronics, H2 needs to be made first. Thusly, hydrogen is often called an &#8220;energy carrier&#8221; rather than a &#8220;fuel.&#8221;
Currently, the most popular way to make H2 gas is from fossil fuels, through steam reforming of hydrocarbons or coal gasification. This does not reduce dependence on fossil fuels and is energy intensive. A less-used method is by electrolysis of water. This also requires an energy source, but it can be a renewable source, like wind or solar power. In electrolysis, water (H2O) is split into its component parts, hydrogen gas (H2) and oxygen gas (O2), through an electrochemical reaction. The hydrogen gas made through the process of electrolysis can then be used in a Proton Exchange Membrane (PEM) fuel cell, generating an electric current. This electric current can be used to power motors, lights, and other electrical devices.

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University
The United States consumes a large amount of energy &#8211; the current ...

Hydrogen Charging of Aluminum using Friction in Water

Samenvatting

Meer video's verkennen