This work was supported by the Wake Forest Chemistry Department and the Wake Forest Center for Energy, Environment, and Sustainability (CEES). We thank Charles Mooney and the Analytical Instrumentation Facility of the North Carolina State University for assistance with SEM imaging.

1. Preparing Xerogel Pellets
<ol>
	<li>Gel Synthesis
	<ol>
		<li>Add a 25 mm magnetic stir bar and 113 mL of deionized water to a 500 mL beaker. Magnetically stir the deionized water at the highest rate that does not form a vortex.</li>
		<li>Slowly add 13.05 g (0.056 mol) of anhydrous zirconium chloride to the deionized water in small increments. After all of the anhydrous zirconium chloride has dissolved, add 53.29 g (0.296 mol) of glucose to the solution.</li>
		<li>After all of the glucose has dissolved in the solu...

<ol>
	<li>Badwal, S. P. S., Giddey, S. S., Munnings, C., Bhatt, A. I., Hollenkamp, A. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Emerging+electrochemical+energy+conversion+and+storage+technologies.">Emerging electrochemical energy conversion and storage technologies.</a> Front. Chem. 2 (79), 1-28 (2014).</li><li>Gross, M. D., Vohs, J. M., Gorte, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+examination+of+SOFC+anode+functional+layers+based+on+ceria+in+YSZ.">An examination of SOFC anode functional layers based on ceria in YSZ.</a> J. Electrochem. Soc. 154 (7), B694-B699 (2007).</li><li>Smith, B. H., Gross, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+highly+conductive+oxide+anode+for+solid+oxide+fuel+cells.">A highly conductive oxide anode for solid oxide fuel cells.</a> Electrochem. Solid-State Lett. 14 (1), B1-B5 (2011).</li><li>Vo, N. M., Gross, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+vanadium+deficiency+on+the+stability+of+Pd+and+Pt+catalysts+in+lanthanum+strontium+vanadate+solid+oxide+fuel+cell+anodes.">The effect of vanadium deficiency on the stability of Pd and Pt catalysts in lanthanum strontium vanadate solid oxide fuel cell anodes.</a> J. Electrochem. Soc. 159 (5), B641-B646 (2012).</li><li>Sholklapper, T. Z., Jacobson, C. P., Visco, S. J., De Jonghe, L. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+dispersed+and+contiguous+nanoparticles+in+solid+oxide+fuel+cell+electrodes.">Synthesis of dispersed and contiguous nanoparticles in solid oxide fuel cell electrodes.</a> Fuel Cells. 8 (5), 303-312 (2008).</li><li>Jiang, Z., Xia, C., Chen, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nano-structured+composite+cathodes+for+intermediate-temperature+solid+oxide+fuel+cells+via+an+infiltration/impregnation+technique.">Nano-structured composite cathodes for intermediate-temperature solid oxide fuel cells via an infiltration/impregnation technique.</a> Electrochim. Acta. 55 (11), 3595-3605 (2010).</li><li>Zhan, Z., Bierschenk, D. M., Cronin, J. S., Barnett, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+reduced+temperature+solid+oxide+fuel+cell+with+nanostructured+anodes.">A reduced temperature solid oxide fuel cell with nanostructured anodes.</a> Energy Environ. Sci. 4, 3951-3954 (2011).</li><li>Gross, M. D., Vohs, J. M., Gorte, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+progress+in+SOFC+anodes+for+direct+utilization+of+hydrocarbons.">Recent progress in SOFC anodes for direct utilization of hydrocarbons.</a> J. Mater. Chem. 17, 3071-3077 (2007).</li><li>Gross, M. D., Carver, K. M., Deighan, M. A., Schenkel, A., Smith, B. M., Yee, A. Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Redox+stability+of+SrNbxTi1-xO3-YSZ+for+use+in+SOFC+anodes.">Redox stability of SrNbxTi1-xO3-YSZ for use in SOFC anodes.</a> J. Electrochem. Soc. 156 (4), B540-B545 (2009).</li><li>Savaniu, C. D., Irvine, J. T. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=La-doped+SrTiO3+as+anode+material+for+IT-SOFC.">La-doped SrTiO3 as anode material for IT-SOFC.</a> Solid State Ionics. 192 (1), 491-493 (2011).</li><li>Choi, S., Shin, J., Kim, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+electrochemical+and+thermodynamic+characterization+of+PrBaCo2-xFexO5+&#948;+(x=0,0.5,1)+infiltrated+into+yttria-stabilized+zirconia+scaffold+as+cathodes+for+solid+oxide+fuel+cells.">The electrochemical and thermodynamic characterization of PrBaCo2-xFexO5+&#948; (x=0,0.5,1) infiltrated into yttria-stabilized zirconia scaffold as cathodes for solid oxide fuel cells.</a> J. Power Sources. 201, 10-17 (2012).</li><li>Kungas, R., Kim, J. S., Vohs, J. M., Gorte, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Restructuring+porous+YSZ+by+treatment+in+hydrofluoric+acid+for+use+in+SOFC+cathodes.">Restructuring porous YSZ by treatment in hydrofluoric acid for use in SOFC cathodes.</a> J. Am. Ceram. Soc. 94 (7), 2220-2224 (2011).</li><li>Jung, W., Dereux, J. O., Chueh, W. C., Hao, Y., Haile, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+electrode+activity+of+nanostructured,+columnar+ceria+films+for+solid+oxide+fuel+cells.">High electrode activity of nanostructured, columnar ceria films for solid oxide fuel cells.</a> Energy Environ. Sci. 5, 8682-8689 (2012).</li><li>Cottam, M., Muhoza, S., Gross, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preserving+nanomorphology+in+YSZ+scaffolds+at+high+temperatures+via+in+situ+carbon+templating+of+hybrid+materials.">Preserving nanomorphology in YSZ scaffolds at high temperatures via in situ carbon templating of hybrid materials.</a> J. Amer. Ceram. Soc. 99 (8), 2625-2631 (2016).</li><li>Alves, L. A., Silva, J. B. A., Giulietti, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solubility+of+D-Glucose+in+Water+and+Ethanol/Water+Mixtures.">Solubility of D-Glucose in Water and Ethanol/Water Mixtures.</a> J. Chem. Eng. Data. 52, 2166-2170 (2007).</li><li>Thommes, M., Smarsly, B., Groenewolt, M., Ravikovitch, P. I., Neimark, A. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adsorption+hysteresis+of+nitrogen+and+argon+in+pore+networks+and+characterization+of+novel+micro-+and+mesoporous+silicas.">Adsorption hysteresis of nitrogen and argon in pore networks and characterization of novel micro- and mesoporous silicas.</a> Langmuir. 22, 756-764 (2006).</li><li>Chervin, C. N., 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+non-alkoxide+sol-gel+method+for+the+preparation+of+homogeneous+nanocrystalline+powders+of+La0.85Sr0.15MnO3.">A non-alkoxide sol-gel method for the preparation of homogeneous nanocrystalline powders of La0.85Sr0.15MnO3.</a> Chem. Mater. 18, 1928-1937 (2006).</li><li>Clapsaddle, B. J., Sprehn, D. W., Gash, A. E., Satcher, J. H., Simpson, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+versatile+sol-gel+synthesis+route+to+metal-silicon+mixed+oxide+nanocomposites+that+contain+metal+oxides+as+a+major+phase.">A versatile sol-gel synthesis route to metal-silicon mixed oxide nanocomposites that contain metal oxides as a major phase.</a> J. Non-Crystalline Solids. 350, 173-181 (2004).</li><li>Gash, A. 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=Use+of+epoxides+in+the+sol-gel+synthesis+of+porous+iron+(III)+oxide+monoliths+from+Fe(III)+salts.">Use of epoxides in the sol-gel synthesis of porous iron (III) oxide monoliths from Fe(III) salts.</a> Chem. Mater. 13, 999-1007 (2001).</li></ol>

We have nothing to disclose.

With this in situ carbon templating approach, one can create and preserve nanomorphology in mixed-metal-oxides at traditional ceramic scaffold sintering temperatures. The resulting surface areas are up to 80 times higher than traditionally sintered scaffolds and up to 4 times higher than scaffolds fabricated by complex deposition techniques.14 The propylene oxide-glucose gel system is highly flexible for tuning the concentration of the carbon template, allowing one to systematically contr...

The solid oxide fuel cell (SOFC) holds great promise as an alternative energy conversion technology for the efficient generation of clean electrical power.1 Considerable progress has been made in the research and development of this technology; however, improvements in electrode performance are still needed to achieve reliable commercialization. The electrode often comprises a porous ceramic scaffold with electrocatalytic particles decorated on the scaffold surface. A large body of research has focused on increasing the surface area of the electrocatalytic particles to increase performance,2,3,4,5,6,7,8 but there is very little research on increasing the scaffold surface area. Increasing the scaffold surface area is challenging because they are sintered at high temperatures, 1,100 &#176;C to 1,500 &#176;C.
Scaffolds processed by traditional sintering typically have a specific surface area of 0.1-1 m2&#183;g-1.8,9,10,11 There are a few reports on increasing the scaffold surface area. In one case, the surface area of a traditionally sintered scaffold was enhanced by dissolution and precipitation of the scaffold surface using hydrofluoric acid, achieving a specific surface area of 2 m2&#183;g-1.12 In another, high temperatures were avoided altogether by using pulsed laser deposition, achieving a specific surface area of 20 m2&#183;g-1.13 The rationale behind the development of our technique was to create a low cost fabrication process that provides unprecedented scaffold surface areas and uses traditional sintering temperatures so that the process can be adopted easily. With the technique reported here, scaffold surface areas up to 80 m2&#183;g-1 have been demonstrated while being processed at traditional sintering temperatures.14
Our research is primarily motivated by SOFC electrode engineering, but the technique is more broadly applicable to other fields and applications. Generally, the in situ carbon templating method is a flexible approach that can produce nanostructured, high surface area mixed-metal ceramic materials in the powder or porous scaffold form. It is flexible in that the mixed-metal ceramic composition, surface area, porosity, and pore size can all be tuned systematically. High temperatures are often needed to form the desired phase in mixed-metal ceramics, and this approach preserves ceramic nanomorphology while allowing one to choose essentially any processing temperature.
This method involves the synthesis of a hybrid inorganic-organic propylene-oxide-based gel, with a well define stoichiometry of metal ions and ratio of inorganic to organic content. The gel is dried under ambient conditions to form a xerogel. The xerogel is sintered in an argon atmosphere at the desired temperature. Upon heating, the organic component decomposes leaving behind a carbon template in situ, which remains for the duration of sintering. The carbon template is subsequently removed by low temperature oxidation in air, resulting in a nanostructured, high surface area ceramic.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Zirconium (IV) chloride, 99.5+%</td>
			<td>Alfa Aesar</td>
			<td>12104</td>
			<td>Air sensitive</td>
		</tr>
		<tr>
			<td>Yttium (III) nitrate hexadydrate, 99.9%</td>
			<td>Alfa Aesar</td>
			<td>12898</td>
			<td>Oxidizer</td>
		</tr>
		<tr>
			<td>D+ Glucose Anhydrous, &#8805; 99.5%</td>
			<td>US Biological Life Sciences</td>
			<td>G3050</td>
			<td></td>
		</tr>
		<tr>
			<td>(&#177;)-Propylene Oxide, &#8805; 99%</td>
			<td>Sigma Aldrich</td>
			<td>110205</td>
			<td>Extremely flammable</td>
		</tr>
		<tr>
			<td>Ethanol 200 Proof</td>
			<td>Decon Laboratories, Inc.</td>
			<td>2716GEA</td>
			<td></td>
		</tr>
		<tr>
			<td>Argon, (99.997%)</td>
			<td>Airgas</td>
			<td>AR 300</td>
			<td>Industrial grade</td>
		</tr>
	</tbody>
</table>

high temperature fabrication of nanostructured yttria-stabilized-zirconia (ysz) scaffolds by in situ carbon templating xerogels

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

Phase purity was confirmed by X-ray diffraction (XRD) as previously reported by Cottam et al.14 YSZ scaffold specific surface area as a function of carbon template concentration is shown in Figure 1. The concentration is shown as the volume percent of total solids in the sintered xerogel pellet. The carbon template concentration systematically increases with increasing glucose concentration in the gel formulation. As shown in Figur...

Watch this Scientific Journal Video about High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels at JoVE.com

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

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

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

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

The overall goal of this materials processing method is to create and preserve nanostructured ceramics at typical centering temperatures by carbon templating hybrid materials in situ. This method can help answer key questions in the materials engineering, and processing fields, such as how to control ceramic nanostructures at conditions far from equilibrium. The main advantage of this technique is that it generates ceramic materials with 80 times more surface area than traditional techniques.Though this method can provide insight into Yttria stabilized Zirconia nanostructures, it can also be applied to essentially any mixed metal oxide material. First, add a 25 millimeter magnetic stir bar and 113 milliliters of deionized water to a 500 milliliter beaker. Stir the deionized water at the highest rate that does not form a vortex.Slowly add 13.05 grams of anhydrous Zirconium Chloride to the deionized water in small increments. After all of the Zirconium Chloride has dissolved, add 53.29 grams of glucose to the solution. After all of the glucose has dissolved, add 3.73 grams of Yttrium nitrate hexahydrate to the solution.Increase the rate of stirring to approximately 700 RPM and wait for all of the solid to dissolve in solution. Following this, add 42 milliliters of propylene oxide to the solution. Once the solution is sufficiently mixed, decrease the stirring to approximately 150 RPM.Continue stirring until the magnetic stir bar has stopped moving due to gel formation. Then tightly cover the beaker containing the gel with parafilm. After allowing the gel to age for 24 hours, remove the parafilm from the beaker and decant the liquid on top of the gel.Next, add 300 milliliters of absolute ethanol to the beaker containing the gel. Tightly cover the beaker with parafilm and leave the covered beaker at room temperature for 24 hours. After repeating the previous step twice, remove the gel from the beaker and place it in a two liter porcelain evaporating dish using a laboratory spatula.Break the gel into pieces with the spatula and spread the pieces over the surface of the evaporating dish. After allowing the gel pieces to dry under ambient conditions, grind the resulting xerogel into a fine powder with an agate mortar and pestle. Now, place one gram of xerogel powder into a 13 millimeter cylindrical pellet press die.Using a hydraulic press, apply 22 kilo Newtons of force for 90 seconds to press the xerogel gel into a pellet. Slowly release the force applied by the press. Then, carefully remove the pellet out of the pellet die.Place the xerogel pellet onto a YSZ plate and load the plate into the center of a tube furnace. Blow Argon at a rate of one third the volume of the working tube per minute for at least 15 minutes, venting the gas outlet to a fume hood. While continuously flowing Argon at a constant rate, program the tube furnace temperature controller to the appropriate heating schedule.Start the program and double check that the tube furnace is heating up following the schedule. After the heating program has completed, remove the pellet from the tube furnace. Using a utility knife, cut a 50 milligram piece out of the centered xerogel pellet.Then grind the xerogel into a fine powder with an agate mortar and pestle. Place approximately 50 milligrams of the fine powder into an Alumina sample cup for thermal gravimetric analysis. Using a thermo gravimetric analyzer, heat the sample at a rate of 10 degrees Celsius per minute from ambient temperature to 1200 degrees Celsius while flowing air over the sample at a rate of 100 milliliters per minute.Calculate the percent change in weight that occurs between 350 and 700 degrees Celsius which corresponds to the total carbon content in the sample. At this point, place the centered xerogel pellet in an Alumina crucible. Place the crucible into a box furnace at 700 degrees Celsius for two hours.Carefully remove the hot crucible from the box furnace with stainless steel crucible tongs. After cooling to room temperature for one hour, remove the porous white YSZ scaffold from the crucible. YSZ scaffold specific surface area as a function of carbon template concentration is shown here.The carbon template concentration and specific surface area systematically increase with increasing glucose concentration and increasing glucose metals molar ratio respectively. The carbon template concentration as quantified by thermo gravimetric analysis was four weight percent and 64 weight percent of total solids for the glucose metals molar ratios of zero to one and 4.5 to one respectively. SEM images show that the particles of YSZ xerogel with glucose additive are several times smaller than those without glucose additive.The formation of smaller particles by adding glucose to the gel in consistent with their high carbon content and surface area. XRD patterns of the strongest YSZ peak for YSZ scaffold as a function of glucose metals molar ratio is shown here. The crystallite size decreased as the molar ratio increased and the crystallite size progression is consistent with the observed increase in surface area with increasing molar ratio.The YSZ scaffold pore size distribution as a function of glucose metals molar ratio shows both the number and size of pores increase with an increase in molar ratio. While attempting this procedure, it's important to remember to maintain a leak tight flow of inert gas through the tube furnace. Following this procedure, other ceramic structures can be created such as here our structures prepared by infiltration of hybrids into traditional progress scaffolds.After watching this video, you should have a good understanding of how to create, preserve, and control ceramic nano morphology at high temperatures.

high-temperature-fabrication-nanostructured-yttria-stabilized

Research

JoVE Journal

Engineering

10.5K Görüntüleme.  Wake Forest University. The overall goal of this materials processing method is to create and preserve nanostructured ceramics at typical centering temperatures by carbon templating hybrid materials in situ. This method can help answer key questions in the materials engineering, and processing fields, such as how to control ceramic nanostructures at conditions far from equilibrium. The main advantage of this technique is that it generates ceramic materials with 80 times more surface area than traditional techniques....