This research was performed at the Pacific Northwest National Laboratory (PNNL), which is operated by Battelle Memorial Institute for the Department of Energy (DOE) under Contract No. DE-AC05-76RL01830.

The experiment described here requires the use of hydrogen gas which is odorless, colorless, and thus undetectable by human senses. Hydrogen is highly flammable and burns with a nearly invisible blue flame and can form explosive mixtures in the presence of oxygen. High pressures in excess of 6.9 MPa add additional explosion hazards that must be appropriately planned for in preparation for any testing. This amount of stored energy represents a serious safety hazard and therefore due diligence, planning, and a safety evaluation must be performed before performing such an experiment to ensure that these hazards are mitigated. The experiment presented here is performed in accordance with appropriate safety precautions in an American Society of Mechanical Engineers (ASME) certified pressure vessel with a burst disk set to 34.5 MPa with proper ventilation.
1. Preparing Polymer Sheet Stock
<ol>
	<li>Apply detergent to the EDPM polymer sheet stock using a non-abrasive sponge and rinse under water for approximately 3 min to remove oils and talc powder applied during the manufacturing and shipping process.</li>
	<li>Dry polymer sheet in a drying oven at 85% of the material&#39;s working temperature, about 75 &#176;C for EPDM, for approximately 72 hours to drive of any water remaining from washing.</li>
	<li>Turn off the oven and allow polymer sheet stock material to cool to room temperature inside the oven.</li>
	<li>Mark one corner of the sheet stock with an arrow pointing to the top of the polymer sheet. This arrow will assist with identifying orientation of the sheet during the sample coupon generation, ensuring that samples cut from the polymer sheet will be consistently of the same orientation.</li>
	<li>Store the polymer stock sheet in a room temperature, humidity-controlled environment near 25% relative humidity prior to tribological testing.</li>
</ol>
2. Generating and Mounting Sample Coupons
<ol>
	<li>While wearing powder free gloves, mark the polymer sheet stock with an arrow in the intended coupon area near the arrow marked during preparation of the polymer sheet stock such that both arrows have the same orientation.</li>
	<li>Using a 2.222 cm diameter circular die and a mallet, stamp out a sample coupon around the arrow mark.</li>
	<li>Loosen the hex cap screws securing the sample clamp on the in situ tribometer, remove the hex cap screw and precision spring from the most easily accessible corner of the sample clamp.</li>
	<li>Slide sample coupon into sample clamp, taking care to make sure the sample is oriented with the arrow pointed face down and towards the back of the clamp which is the side closest to the back-plate of the tribometer.</li>
	<li>Replace the precision spring and hex cap screw in the empty corner of the sample clamp and proceed to hand tighten all four of the hex cap screws of the clamp until snug such that the elastomer sample is compressed by 10% of its original height. Assuming a 0.318 cm sample height, 10% compression can be achieved by using a 0.287 cm gauge block between the two plates of the clamp.</li>
</ol>
3. Preparing the In Situ Tribometer
<ol>
	<li>Place a 2.413 cm gauge block between the wall of the tribometer and the sample sled, directly below the drive screw. Make sure the data collection box is turned off, then turn the drive chain in a clockwise motion to back the sample sled such that the edge of the sled is 2.413 cm from the tribometer wall.</li>
	<li>Gently wipe the steel ball of the counter surface with a soft cloth or lint-less paper towel and an appropriate solvent such as acetone for approximately 30 seconds until the surface of the counter surface appears free of any debris.</li>
	<li>Slide the bronze counter surface carrier and bronze weight, a total normal load of 7.5 N, onto the rail perpendicular to the sample sled, allowing the counter ball to slide between into the keyhole and rest on the polymer sample.</li>
	<li>Using a hex key and two bronze screws, reattach the linear variable differential transformer (LVDT) measurement arm to the bronze counter surface holder such that the freely floating cylinder of the LVDT rests on the arm.</li>
	<li>Adjust the clamp holding the LVDT in place up or down such that the LVDT is measuring near it&#39;s zero point then tighten the clamp to secure the LVDT in place.</li>
	<li>Lower the tribometer assembly into the pressure vessel, ensuring that the thermowell in the top flange of the vessel will lower into the gap between the tribometer and the wall of the vessel.</li>
	<li>Wrap the sealing o-ring with a total of two and a half layers of PTFE tape. This is accomplished by wrapping the PTFE tape such that each additional wrap overlaps approximately half of the proceeding lap until going around the diameter of the o-ring twice. Then wrap the diameter of the o-ring a final time without any overlap. Once the o-ring is wrapped, place it in the groove in the lip of the pressure vessel.</li>
	<li>Taking into account the wiring labels, reconnect the five power wires for the tribometer motor, four data wires for the load cell, and five data wires for the LVDT.</li>
</ol>
4. Sealing the Pressure Vessel
<ol>
	<li>Lower the top flange of the pressure vessel to close it, taking care to lower the top flange gently onto the PTFE wrapped sealing o-ring.</li>
	<li>Insert the bolts into the numbered holes on the top flange indicated by the manufacturer in ascending order until they are finger tight.</li>
	<li>Using a manual hex key, torque the flange bolts in ascending order to hand tight and repeat until the bolts can no longer be tightened.</li>
	<li>Starting at 120 Nm and increasing in ~40 Nm increments, use a torque wrench to torque the flange bolts in ascending order for each ~40 Nm increment until they are torqued to 280 Nm.</li>
</ol>
5. Filling the Pressure Vessel
<ol>
	<li>Now that the pressure vessel is sealed, connect the gas fittings to the autoclave lid and flush the pressure vessel with low pressure (~0.55 MPa) argon gas for approximately 1 h until the oxygen content of the vessel drops below 10 ppm using an oxygen sensor plumbed into the output of the pressure vessel.</li>
	<li>Slowly (&#60;0.25 MPa/s) flush the vessel with hydrogen gas up to 6.9 MPa, then slowly vent the gas to atmospheric pressure. Repeat the flushing process two more times.</li>
	<li>After flushing the pressure vessel, slowly (&#60;0.25 MPa/s) fill the pressure vessel with hydrogen gas up to 13.75 MPa and allow the vessel to rest for 10 min such that the temperature of the gas within the vessel equilibrates to room temperature.</li>
	<li>Fill the vessel to 20.7 MPa and wait another 10 min.</li>
	<li>Bring the vessel up to the target 27.6 MPa and close off all valves.</li>
	<li>Allow the polymer sample to soak for at least 12 h in the hydrogen gas before starting the experiment to allow for complete permeation.</li>
</ol>
6. Running Experiment
<ol>
	<li>Double check that all the pass-through wires exiting the pressure vessel are correctly connected to the labelled wiring harness attached to the tribometer control box, and then turn on the tribometer.</li>
	<li>In the tribometer software set the experiment time to 1 hour at 0.1 cm/s velocity with a path length of 0.140 cm. This corresponds to a distance of approximately 3.5 m.</li>
	<li>Tare the load cell, and ensure that the LVDT is reporting an appropriate depth in the tribometer software which should be near 0 mm.</li>
	<li>Start the experiment.</li>
</ol>
7. Post-Experiment
<ol>
	<li>Once the experiment has completed, slowly vent the pressure vessel of hydrogen gas at approximately 0.35 MPa/s, ensuring that the pressure vessel temperature does not drop below 0 &#176;C.</li>
	<li>Finally, flush the pressure vessel volume with argon gas at atmospheric pressure for 10 minutes to ensure that there is no remaining hydrogen within the vessel.</li>
</ol>

<ol>
	<li>Schlapbach, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Technology:+Hydrogen-fuelled+vehicles.">Technology: Hydrogen-fuelled vehicles.</a> Nature. 460 (7257), 809-811 (2009).</li><li>Jones, R., Thomas, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Materials for the Hydrogen Economy. , (2007).</li><li>Barth, R., Simons, K. L., San Marchi, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Polymers for Hydrogen Infrastructure and Vehicle Fuel Systems: Applications, Properties, and Gap Analysis. , 23-34 (2013).</li><li>Marchi, C., Somerday, B. P., Ref, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Technical Reference on Hydrogen Compatibility of Materials. , (2008).</li><li>Welch, A., 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=.">.</a> Challenges in developing hydrogen direct injection technology for internal combustion engines. , (2008).</li><li>Fukai, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Metal-Hydrogen System. , (2005).</li><li>Lu, G., Kaxiras, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogen+embrittlement+of+aluminum:+The+crucial+role+of+vacancies.">Hydrogen embrittlement of aluminum: The crucial role of vacancies.</a> Phys. Rev. Lett. 94 (15), 155501 (2005).</li><li>Zhao, Z., Carpenter, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Annealing+enhanced+hydrogen+absorption+in+nanocrystalline+Pd&#8725;AuPd&#8725;Au+sensing+films.">Annealing enhanced hydrogen absorption in nanocrystalline Pd&#8725;AuPd&#8725;Au sensing films.</a> J. Appl. Phys. 97 (12), 124301 (2005).</li><li>Alvine, K. J., 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=High-pressure+hydrogen+materials+compatibility+of+piezoelectric+films.">High-pressure hydrogen materials compatibility of piezoelectric films.</a> Appl. Phys. Lett. 97 (22), 221911 (2010).</li><li>Alvine, K. J., 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=Hydrogen+species+motion+in+piezoelectrics:+A+quasi-elastic+neutron+scattering+study.">Hydrogen species motion in piezoelectrics: A quasi-elastic neutron scattering study.</a> J. Appl. Phys. 111 (5), 53505 (2012).</li><li>Aggarwal, S., 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=Effect+of+hydrogen+on+Pb(Zr,Ti)O3Pb(Zr,Ti)O3-based+ferroelectric+capacitors.">Effect of hydrogen on Pb(Zr,Ti)O3Pb(Zr,Ti)O3-based ferroelectric capacitors.</a> Appl. Phys. Lett. 73 (14), (1998).</li><li>Ikarashi, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analytical+transmission+electron+microscopy+of+hydrogen-induced+degradation+in+ferroelectric+Pb(Zr,+Ti)O3Pb(Zr,+Ti)O3+on+a+Pt+electrod.">Analytical transmission electron microscopy of hydrogen-induced degradation in ferroelectric Pb(Zr, Ti)O3Pb(Zr, Ti)O3 on a Pt electrod.</a> Appl. Phys. Lett. 73 (14), (1998).</li><li>Castagnet, S., Grandidier, J., Comyn, M., Beno&#305;, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogen+influence+on+the+tensile+properties+of+mono+and+multi-layer+polymers+for+gas+distribution.">Hydrogen influence on the tensile properties of mono and multi-layer polymers for gas distribution.</a> Int. J. Hydrog. Energy. 35, 7633-7640 (2010).</li><li>Theiler, G., Gradt, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tribological+characteristics+of+polyimide+composites+in+Hydrogen+environment.">Tribological characteristics of polyimide composites in Hydrogen environment.</a> Tribol. Int. 92, 162-171 (2015).</li><li>Sawae, Y., 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=Friction+and+wear+of+bronze+filled+PTFE+and+graphite+filled+PTFE+in+40+MPA+hydrogen+gas.">Friction and wear of bronze filled PTFE and graphite filled PTFE in 40 MPA hydrogen gas.</a> Proceed. , 249-251 (2011).</li><li>Fujiwara, H., Ono, H., Nishimura, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Degradation+behavior+of+acrylonitrile+butadiene+rubber+after+cyclic+high-pressure+hydrogen+exposure.">Degradation behavior of acrylonitrile butadiene rubber after cyclic high-pressure hydrogen exposure.</a> Int. J. Hydrogen Energy. 40 (4), 2025-2034 (2015).</li><li>Zhang, L., 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=Influence+of+low+temperature+prestrain+on+hydrogen+gas+embrittlement+of+metastable+austenitic+stainless+steels.">Influence of low temperature prestrain on hydrogen gas embrittlement of metastable austenitic stainless steels.</a> Int. J. Hydrogen Energy. 38 (25), 11181-11187 (2013).</li><li>Weber, S., Theisen, W., Mart&#305;, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+stable+high-aluminum+austenitic+stainless+steel+for+hydrogen+applications.">Development of a stable high-aluminum austenitic stainless steel for hydrogen applications.</a> Int. J. Hydrogen Energy. 38 (14), 5989-6001 (2013).</li><li>Papavinasam, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Corrosion control in the oil and gas industry. , (2013).</li><li>Yamamoto, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogen+Embrittlement+of+Nuclear+Power+Plant+Materials.">Hydrogen Embrittlement of Nuclear Power Plant Materials.</a> Mat. Trans. 45 (8), 2647-2649 (2004).</li><li>Rymuza, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tribology+of+polymers.">Tribology of polymers.</a> Arch. Civ. Mech. Eng. 7 (4), 177-184 (2007).</li><li>Mckeen, L. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 1 Introduction to Fatigue and Tribology of Plastics and Elastomers. , (2010).</li><li>Lorge, O., Briscoe, B. J., Dang, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gas+induced+damage+in+poly(vinylidene+fluoride)+exposed+to+decompression.">Gas induced damage in poly(vinylidene fluoride) exposed to decompression.</a> Polymer. 40, 2981-2991 (1999).</li><li>Sawae, Y., Yamaguchi, A., Nakashima, K., Murakami, T., Sugimura, J. <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+Atmosphere+on+Wear+Behavior+of+PTFE+Sliding+Against+Austenitic+Stainless+Steel.">Effects of Hydrogen Atmosphere on Wear Behavior of PTFE Sliding Against Austenitic Stainless Steel.</a> Proceed. , 1-3 (2008).</li><li>Sawae, Y., Nakashima, K., Doi, S., Murakami, T., Sugimura, J. <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+high+pressure+hydrogen+on+wear+of+PTFE+and+PTFE+composite.">Effects of high pressure hydrogen on wear of PTFE and PTFE composite.</a> Proceed. , 233-235 (2010).</li><li>Duranty, E., 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=An+in+situ+tribometer+for+measuring+friction+and+wear+of+polymers+in+a+high+pressure+hydrogen+environment.">An in situ tribometer for measuring friction and wear of polymers in a high pressure hydrogen environment.</a> Rev. Sci. Instrum. 88 (9), (2017).</li></ol>

The authors have nothing to disclose.

Current ex situ techniques for tribological testing of polymer materials require samples to be exposed to high pressure hydrogen which are then depressurized before being tested using a commercial tribometer.15,24,25 The test methodology in this protocol was designed to permit testing of the tribological properties of polymer samples in a high pressure environment in situ. By testing polymer materials such as t...

In the recent years, there has been great interest in hydrogen as a potential zero emission or near-zero emission fuel in vehicles and stationary power sources. Since hydrogen exists as a low density gas at room temperature, most applications use some form of compressed hydrogen for fuel.1,2 A potential drawback of using compressed, high pressure hydrogen gas is incompatibility with many materials found within infrastructure2,3,4 and vehicular applications5 where compatibility issues are combined with repeated pressure and temperature cycling. A pure hydrogen environment is known to damage metal components including certain steels and titanium through different mechanisms including hydride formation, swelling, surface blistering, and embrittlement.2,6,7,8 Non-metallic components such as lead zirconate titanate (PZT) used in piezoelectric ceramics have also proven susceptible to degradation due to hydrogen incompatibility effect such as surface blistering and lead migration.9,10,11,12 While these examples of damage due to hydrogen exposure have been previously studied, the compatibility of polymer components within hydrogen environments has only recently become of interest.13,14,15,16 This is largely a result of metallic components providing structural integrity in nuclear and oil and gas applications whereas the polymer components usually act as barriers or seals.17,18,19,20 As a result, the friction and wear properties of polymer materials within components such as polytetrafluoroethylene (PTFE) valve seats and nitrile butadiene rubber (NBR) O-rings become important factors in their ability to function.
In the case of the hydrogen infrastructure, components such as valves, compressors, and storage tanks contain polymer materials that are in contact with metallic surfaces. The frictional interaction between the polymer and metallic surfaces results in wear of each of the surfaces. The science of the relationship between the friction and wear of two interacting surfaces is known as tribology. Polymers tend to have lower elastic moduli and strength than metallic, therefore the tribological properties of polymer materials differ greatly from metallic materials. As a result, polymer surfaces tend to exhibit greater wear and damage after frictional contact with a metallic surface.21,22 In a hydrogen infrastructure application, rapid pressure and temperature cycling causes repeated interaction between the polymer and metallic surfaces, increasing the likelihood of friction and wear on the polymer component. Quantifying this damage can be challenging ex situ due to possible explosive decompression of the polymer sample after depressurization which may cause non-tribological damage.23 Additionally, many commercial polymer products contain many fillers and additives such as magnesium oxide (MgO) that may interact negatively with hydrogen gas through hydriding, further complicating ex situ analysis of wear in these materials.24,25
Due to the complexity of differentiating between damage to the polymer material caused during depressurization and damage due to tribological wear ex situ, there is a need to directly study the frictional properties of non-metallic materials in situ within a high-pressure hydrogen environment that is likely to exist within the hydrogen delivery infrastructure. In this protocol, we demonstrate a test methodology developed to quantify the friction and wear properties of polymer materials in a high-pressure hydrogen environment utilizing a purpose-built in situ tribometer.26 We also present representative data acquired using the in situ tribometer and ethylene propylene diene monomer (EPDM) rubber, a common polymer sealing and barrier material. The EPDM material for which representative data was generated using the protocol below was purchased in 60.96 cm square sheets with a 0.3175 cm thickness and was reported by the vendor to have a 60A hardness rating.

<table border="0" cellpadding="0" cellspacing="0" width="597">
	<tbody>
		<tr height="79">
			<td height="79" style="height:79px;width:201px;">EPDM Polymer Stock Sheet</td>
			<td style="width:123px;">McMaster-Carr</td>
			<td style="width:117px;">8525T68</td>
			<td style="width:156px;">24&#34; x 24&#34;, 1/8&#34; Thick</td>
		</tr>
		<tr height="49">
			<td height="49" style="height:49px;width:201px;">Pressure Vessel, Autoclave</td>
			<td style="width:123px;">Fluitron Inc.</td>
			<td style="width:117px;">8308-1788-U</td>
			<td style="width:156px;">5&#34; diameter, 1&#39; height</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:201px;">High Purity Hydrogen Gas</td>
			<td style="width:123px;">Praxair</td>
			<td style="width:117px;">HY4.5</td>
			<td style="width:156px;">Grade 4.5, 5ppm O2, 5 ppm H20</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:201px;">O2 Sensor</td>
			<td style="width:123px;">Advanced Micro Instruments</td>
			<td style="width:117px;">T2</td>
			<td style="width:156px;">0-5ppm min. range, 10,0000ppm max.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:201px;">Pre-purified Argon Gas</td>
			<td style="width:123px;">Oxarc</td>
			<td style="width:117px;">LCCO-HP818</td>
			<td style="width:156px;">High-purity, 99.998%</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:201px;">Liquid Dishwashing Detergent</td>
			<td style="width:123px;">McMaster-Carr</td>
			<td style="width:117px;">98365T89</td>
			<td style="width:156px;">32 oz pour bottle, lemon scented</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:201px;">Mildew Resistant Sponge</td>
			<td style="width:123px;">McMaster-Carr</td>
			<td style="width:117px;">7309T1</td>
			<td style="width:156px;">6&#34; long x 3 -1/2&#34; Wide x 1&#34; High, yellow</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:201px;">PTFE Pipe Thread Sealant Tape</td>
			<td style="width:123px;">McMaster-Carr</td>
			<td style="width:117px;">4591K12</td>
			<td style="width:156px;">1/2&#34; wide, white color</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:201px;">Gas Tube Fittings</td>
			<td style="width:123px;">Swagelok</td>
			<td style="width:117px;">SS-400-1-4</td>
			<td style="width:156px;">1/4&#34; OD, stainless steel, male NPT threading</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:201px;">Hammer Driven Die</td>
			<td style="width:123px;">McMaster-Carr</td>
			<td style="width:117px;">3427A22</td>
			<td style="width:156px;">7/8&#34; Hammer driven hole punch</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:201px;">Linear Variable Differential Transformer</td>
			<td style="width:123px;">Omega</td>
			<td style="width:117px;">LD320-2.5&#160;</td>
			<td style="width:156px;">2.5mm, AC output, guided w/spring</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:201px;">Autoclave O-ring Seal</td>
			<td style="width:123px;">Fluitron Inc.</td>
			<td style="width:117px;">A-4511</td>
			<td style="width:156px;">Hastelloy C-276, 5-3/4&#34; OD x 5&#34; ID x 3/8&#34;</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:201px;">Torque Wrench</td>
			<td style="width:123px;">McMaster-Carr</td>
			<td style="width:117px;">85555A422</td>
			<td style="width:156px;">Adjustable Torque-Limiting Wrench, Quick-Release, 1/2&#34; Square Drive, 50-250 ft.-lbs. Torque</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:201px;">Mallet</td>
			<td style="width:123px;">McMaster-Carr</td>
			<td style="width:117px;">5939A11</td>
			<td style="width:156px;">Hard and Extra-Hard Rubber Hammer, 2-1/4 lbs.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:201px;">iLoad Mini Capacitive Load Sensor</td>
			<td style="width:123px;">Loadstar Sensors</td>
			<td style="width:117px;">MFM-050-050-S*C03</td>
			<td style="width:156px;">50 lb, U Calibration, 0.5% Accuracy, Steel</td>
		</tr>
	</tbody>
</table>

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.

Using the methodology presented, the coefficient of kinetic friction and wear factor for an elastomeric sample can be measured while in a high-pressure hydrogen environment. The representative data presented in Figure 1 show that in a high-pressure hydrogen environment greater force is required to move EPDM polymer samples under the steel counter surface. Using the relationship between the normal force FN and the frictional force FK the ...

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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.

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 ...

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Research

JoVE Journal

Engineering

7.5K Views.  Pacific Northwest National Laboratory. 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.

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

Synthesis and Microdiffraction at Extreme Pressures and Temperatures

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary interiors, design materials with novel properties, understand the mechanical behavior of materials exposed to very high stresses as in explosions or impacts. Synthesis and structural analysis of materials at extreme conditions of pressure and temperature entails remarkable technical challenges. In the laser heated diamond anvil cell (LH-DAC), very high pressure is generated between the tips of two opposing diamond anvils forced against each other; focused infrared laser beams, shined through the diamonds, allow to reach very high temperatures on samples absorbing the laser radiation. When the LH-DAC is installed in a synchrotron beamline that provides extremely brilliant x-ray radiation, the structure of materials under extreme conditions can be probed in situ. LH-DAC samples, although very small, can show highly variable grain size, phase and chemical composition. In order to obtain the high resolution structural analysis and the most comprehensive characterization of a sample, we collect diffraction data in 2D grids and combine powder, single crystal and multigrain diffraction techniques. Representative results obtained in the synthesis of a new iron oxide, Fe4O5 1 will be shown.

The laser heated diamond anvil cell combined with synchrotron micro-diffraction techniques allows researchers to explore the nature and properties of new phases of matter at extreme pressure and temperature (PT) conditions. Heterogeneous samples can be characterized in situ under high pressure by 2D mapping and combined powder, single-crystal and multigrain diffraction approaches.

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary ...

Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and non-destructively reveals the hydrogen density distribution at surfaces, at interfaces, and in the volume of solid materials with high depth resolution. The technique applies a 15N ion beam of 6.385 MeV provided by an electrostatic accelerator and specifically detects the 1H isotope in depths up to about 2 &#956;m from the target surface. Surface H coverages are measured with a sensitivity in the order of ~1013 cm-2 (~1% of a typical atomic monolayer density) and H volume concentrations with a detection limit of ~1018 cm-3 (~100 at. ppm). The near-surface depth resolution is 2-5 nm for surface-normal 15N ion incidence onto the target and can be enhanced to values below 1 nm for very flat targets by adopting a surface-grazing incidence geometry. The method is versatile and readily applied to any high vacuum compatible homogeneous material with a smooth surface (no pores). Electrically conductive targets usually tolerate the ion beam irradiation with negligible degradation. Hydrogen quantitation and correct depth analysis require knowledge of the elementary composition (besides hydrogen) and mass density of the target material. Especially in combination with ultra-high vacuum methods for in-situ target preparation and characterization, 1H(15N,&#945;&#947;)12C NRA is ideally suited for hydrogen analysis at atomically controlled surfaces and nanostructured interfaces. We exemplarily demonstrate here the application of 15N NRA at the MALT Tandem accelerator facility of the University of Tokyo to (1) quantitatively measure the surface coverage and the bulk concentration of hydrogen in the near-surface region of a H2 exposed Pd(110) single crystal, and (2) to determine the depth location and layer density of hydrogen near the interfaces of thin SiO2 films on Si(100).

We illustrate the application of 1H(15N,&#945;&#947;)12C resonant nuclear reaction analysis (NRA) to quantitatively evaluate the density of hydrogen atoms on the surface, in the volume, and at an interfacial layer of solid materials. The near-surface hydrogen depth profiling of a Pd(110) single crystal and of SiO2/Si(100) stacks is described.

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and ...

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 ...

Spark Plasma Sintering Apparatus Used for the Formation of Strontium Titanate Bicrystals

A spark plasma sintering apparatus was used as a novel method for diffusion bonding of two single crystals of strontium titanate to form bicrystals with one twist grain boundary. This apparatus utilizes high uniaxial pressure and a pulsed direct current for rapid consolidation of material. Diffusion bonding of strontium titanate bicrystals without fracture, in a spark plasma sintering apparatus, is possible at high pressures due to the unusual temperature dependent plasticity behavior of strontium titanate. We demonstrate a method for the successful formation of bicrystals at accelerated time scales and lower temperatures in a spark plasma sintering apparatus compared to bicrystals formed by conventional diffusion bonding parameters. Bond quality was verified by scanning electron microscopy. A clean and atomically abrupt interface containing no secondary phases was observed using transmission electron microscopy techniques. Local changes in bonding across the boundary was characterized by simultaneous scanning transmission electron microscopy and spatially resolved electron energy-loss spectroscopy.

A viable technique for the formation of strontium titanate bicrystals at high pressure and fast heating rate via the spark plasma sintering apparatus is developed.

A spark plasma sintering apparatus was used as a novel method for diffusion bonding of two single crystals of strontium titanate to form bicrystals with ...

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, ...

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

Solid-state electrolytes are a promising replacement for current organic liquid electrolytes, enabling higher energy densities and improved safety of lithium-ion (Li-ion) batteries. However, a number of setbacks prevent their integration into commercial devices. The main limiting factor is due to nanoscale phenomena occurring at the electrode/electrolyte interfaces, ultimately leading to degradation of battery operation. These key problems are highly challenging to observe and characterize as these batteries contain multiple buried interfaces. One approach for direct observation of interfacial phenomena in thin film batteries is through the fabrication of electrochemically active nanobatteries by a focused ion beam (FIB). As such, a reliable technique to fabricate nanobatteries was developed and demonstrated in recent work. Herein, a detailed protocol with a step-by-step process is presented to enable the reproduction of this nanobattery fabrication process. In particular, this technique was applied to a thin film battery consisting of LiCoO2/LiPON/a-Si, and has further been previously demonstrated by in situ cycling within a transmission electron microscope.

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

A protocol for the fabrication of electrochemically active LiPON-based solid-state lithium-ion nanobatteries using a focused ion beam is presented.

Solid-state electrolytes are a promising replacement for current organic liquid electrolytes, enabling higher energy densities and improved safety of ...

Detecting the Water-soluble Chloride Distribution of Cement Paste in a High-precision Way

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a high-precision chloride profile. Firstly, paste specimens are molded, cured, and exposed to cyclic wet-dry conditions. Then, powder samples at different specimen depths are grinded when the exposure age is reached. Finally, the water-soluble chloride content is detected using a silver nitrate titration method, and chloride profiles are plotted. The key to improving the accuracy of the chloride distribution along the depth is to exclude the error in the powderization, which is the most critical step for testing the distribution of chloride. Based on the above concept, the grinding method in this protocol can be used to grind powder samples automatically layer by layer from the surface inward, and it should be noted that a very thin grinding thickness (less than 0.5 mm) with a minimum error less than 0.04 mm can be obtained. The chloride profile obtained by this method better reflects the chloride distribution in specimens, which helps researchers to capture the distribution features that are often overlooked. Furthermore, this method can be applied to studies in the field of cement-based materials, which require high chloride distribution accuracy.

A protocol for obtaining a water-soluble chloride profile by using a high precision milling method is presented.

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a ...

Ultrasonic Fatigue Testing in the Tension-Compression Mode

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on exposing the specimen to longitudinal vibrations on its resonance frequency close to 20 kHz. With use of this method, it is possible to significantly decrease the time required for the test, when compared to conventional testing devices usually working at frequencies under 200 Hz. It is also used to simulate loading of material during operation in high speed conditions, such as those experienced by components of jet engines or car turbo pumps. It is necessary to operate only in the high and ultra-high cycle region, due to the possibility of extremely high deformation rates, which can have a significant influence on the test results. Specimen shape and dimensions have to be carefully selected and calculated to fulfill the resonance condition of the ultrasonic system; thus, it is not possible to test the full components or specimens of arbitrary shape. Before each test, it is necessary to harmonize the specimen with the frequency of the ultrasonic system to compensate for deviations of the real shape from the ideal one. It is not possible to run a test until a total fracture of the specimen, since the test is automatically terminated after initiation and propagation of the crack to a certain length, when the stiffness of the system changes enough to shift the system out of the resonance frequency. This manuscript describes the process of evaluation of materials' fatigue properties at high-frequency ultrasonic fatigue loading with use of mechanical resonance at a frequency close to 20 kHz. The protocol includes a detailed description of all steps required for a correct test, including specimen design, stress calculation, harmonizing with the resonance frequency, performing the test, and final static fracture.

A protocol for ultrasonic fatigue testing in the high and ultra-high cycle region in axial tension-compression loading mode.

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on ...

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic glasses (MGs). Despite their amorphous nature, the identification of hyperfine interactions unveils faint structural modifications. For this purpose, we have employed two techniques that utilize nuclear resonance among nuclear levels of a stable 57Fe isotope, namely M&#246;ssbauer spectrometry and nuclear forward scattering (NFS) of synchrotron radiation. The effects of heat treatment upon (Fe2.85Co1)77Mo8Cu1B14 MG are discussed using the results of ex situ and in situ experiments, respectively. As both methods are sensitive to hyperfine interactions, information on structural arrangement as well as on magnetic microstructure is readily available. M&#246;ssbauer spectrometry performed ex situ describes how the structural arrangement and magnetic microstructure appears at room temperature after the annealing under certain conditions (temperature, time), and thus this technique inspects steady states. On the other hand, NFS data are recorded in situ during dynamically changing temperature and NFS examines transient states. The use of both techniques provides complementary information. In general, they can be applied to any suitable system in which it is important to know its steady state but also transient states.

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Here, we present a protocol to describe ex situ and in situ investigations of structural transformations in metallic glasses. We employed nuclear-based analytical methods which inspect hyperfine interactions. We demonstrate the applicability of M&#246;ssbauer spectrometry and nuclear forward scattering of synchrotron radiation during temperature-driven experiments.

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic ...

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone (ITZ)

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect of aggregate surface morphology on the formation of ITZ. First, a model concrete sample is prepared with a spherical ceramic particle in roughly the central part of the cement matrix, acting as a coarse aggregate used in common concrete/mortar. After curing until the designed age, the sample is scanned by X-ray computed tomography to determine the relative location of the ceramic particle inside the cement matrix. Three locations of the ITZ are chosen: above the aggregate, on the side of the aggregate, and below the aggregate. After a series of treatments, the samples are scanned with a SEM-BSE detector. The resultant images were further processed using a digital image processing method (DIP) to obtain quantitative characteristics of the ITZ. The surface morphology is characterized at the pixel level based on the digital image. Thereafter, K-means clustering method is used to illustrate the effect of surface roughness on ITZ formation.

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone ITZ

Hereby, we proposed a protocol to illustrate the effect of aggregate surface morphology on the ITZ microstructure. The SEM-BSE image were quantitatively analyzed to obtain ITZ's porosity gradient via digital image processing and a K-means clustering algorithm was further employed to establish a relationship between porosity gradient and surface roughness.

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect ...