Publications

Journal Publications

Key: * indicates undergraduate student co-author; ** indicates MSME student co-author; § indicates high-school student co-author.

Posada*, LF, Carroll, MK, Anderson, AM & Bruno, BA (2019). “Inclusion of Ceria in Alumina- and Silica-Based Aerogels for Catalytic Applications.” Supercritical Fluids 152, 104536.

Ceria-alumina (CeAl) and ceria-silica (CeSi) catalytic aerogels were prepared. Cerium undergoes rapid changes in oxidation state, which makes it a good oxygen-storage component for automotive catalysis applications. The high surface area and thermal stability of alumina- and silica-based aerogels render them attractive catalyst platforms. Co-precursor (for CeAl and CeSi) and impregnation (for CeSi) synthetic approaches were employed, followed by rapid supercritical extraction (RSCE) to yield aerogels. Physical characterization (bulk density, surface area, FTIR, XRD, and SEM/EDX) was performed on the as-prepared aerogels, after heat treatment (calcining), and after catalytic testing in a testbed that simulates aspects of catalytic converter conditions. The aerogels have low densities (≤0.1 g/cm³) and relatively high surface areas (ca. 100 m²/g for CeAl, ≥400 m²/g for CeSi). Microcrystalline CeO₂is observed in heat-treated and catalytically tested aerogels. CeSi aerogels show catalytic activity toward CO and NO; at high temperature, CeAl aerogels act as three-way catalysts.

Merli, F, Anderson, AM, Carroll, MK, & Buratti, C (2018). Acoustic measurements on monolithic aerogel samples and application of the selected solutions to standard window systems. Applied Acoustics, 142, 123-131.

Silica aerogels are thermally and acoustically insulating and can offer advantages in building thermal applications. They come in granular (multiple small pieces) and monolithic (single piece) form. Granular aerogels are relatively easy to produce and can be incorporated into large window systems. Large monolithic aerogels are more difficult to produce, but they offer superior optical and thermal performance. The aim of this paper is to experimentally investigate the acoustic properties of monolithic aerogel samples fabricated using a rapid supercritical extraction method. The acoustic absorption coefficient (α) and the transmission loss (TL) were measured at normal incidence in a traditional impedance tube in the 100–5000 Hz frequency range, for three thicknesses, from 12.7 to 25.4 mm. Good acoustic performance was achieved: 12.7-mm-thick cylindrical monoliths have a peak acoustic absorption coefficient of 0.88 at ∼1500 Hz. When the thickness increases, α decreases (to 0.78 and 0.54 for 19-mm and 25.4-mm thick samples, respectively), with peaks at lower frequencies (1300 and 1100 Hz). The transmission loss increases with aerogel thickness with values as high as 10–15 dB in the 100- to 1600-Hz range. When compared to granular aerogels, the monoliths have TLs that are 5–7 dB larger in the 100- to 1600-Hz range. To further compare performance, small glazing packages were fabricated from glass panels with air, granular, or monolithic aerogel in the interspace. The TL was evaluated and found to be in the 35- to 45-dB range for all samples. The monolithic aerogel glazing had the highest TL, particularly in the 200- to 1000-Hz range. Based on these results, we estimated a 3-dB increase in the sound insulation index for the glazing system with a monolith when compared to the glazing system with air, and a 1- to 2-dB increase when compared to the granular aerogel glazing. This study demonstrates that the use of transparent monolithic silica aerogel in the interspace of conventional glazing systems would result in significant improvement in noise insulation.

Anderson, AM, Bruno, BA, Donlon*, EA, Posada*, LF, & Carroll, MK (2018). Fabrication and Testing of Catalytic Aerogels Prepared Via Rapid Supercritical Extraction. of Visualized Experiments, (138), e57075.

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three preparation methods are described: (a) the incorporation of metal salts into silica or alumina wet gels using an impregnation method; (b) the incorporation of metal salts into alumina wet gels using a co-precursor method; and (c) the addition of metal nanoparticles directly into a silica aerogel precursor mixture. The methods utilize a hydraulic hot press, which allows for rapid (<6 h) supercritical extraction and results in aerogels of low density (0.10 g/mL) and high surface area (200-800 m2/g). While the work presented here focuses on the use of copper salts and copper nanoparticles, the approach can be implemented using other metal salts and nanoparticles. A protocol for testing the three-way catalytic ability of these aerogels for automotive pollution mitigation is also presented. This technique uses custom-built equipment, the Union Catalytic Testbed (UCAT), in which a simulated exhaust mixture is passed over an aerogel sample at a controlled temperature and flow rate. The system is capable of measuring the ability of the catalytic aerogels, under both oxidizing and reducing conditions, to convert CO, NO and unburned hydrocarbons (HCs) to less harmful species (CO2, H2O and N2). Example catalytic results are presented for the aerogels described.

Karatum, O, Bhuiya, MMH, Carroll, MK, Anderson, AM, & Plata, DL (2018). Life Cycle Assessment of Aerogel Manufacture on Small and Large Scales: Weighing the Use of Advanced Materials in Oil Spill Remediation. of Industrial Ecology. https://doi.org/10.1111/jiec.12720

Recent studies demonstrated that advanced aerogel composites (Aspen Aerogels^® Spaceloft^® [SL]) have the potential to transform oil remediation via high oil uptake capacity and selectivity, excellent reusability, and high mechanical strength. Understanding the life cycle environmental impacts of advanced aerogels can enable a more holistic decision‐making process when considering oil recovery technologies following a spill. Here, we perform a cradle‐to‐grave streamlined life cycle assessment (LCA) following International Organization for Standardization (ISO) 14040 2006 for SL weighed against the conventional oil sorbent material, polyurethane foam. The model included alternative use and disposal scenarios, such as single or multiple uses, and landfill, incinerator, and waste‐to‐energy (WTE) approaches for cleaning 1 cubic meter (m³) of light crude oil. Results showed that the ideal case for SL application was comprised of multiple use and WTE incineration (68% reduction in material use, approximately 7 × 10³ megajoules [MJ] of energy recovery from WTE), but SL offered energy and materials savings even when used once and disposed of via traditional means (i.e., landfill). In addition to evaluating these already‐scaled processes, we performed an anticipatory LCA for the laboratory‐scaled aerogel fabrication process that might inform the sustainable design of next‐generation aerogels. In particular, the model compared rapid supercritical extraction (RSCE) with two conventional supercritical extraction methods—alcohol and carbon dioxide supercritical extraction (ASCE and CSCE, respectively)—for silica aerogel monoliths. Our results showed that RSCE yielded a cumulative energy savings of more than 76 × 10³ and 100 × 10³ MJ for 1 m³ of monolithic silica aerogel manufacturing compared to ASCE and CSCE, respectively.

Tobin* ZM, Posada* LF, Bechu* AM, Carroll MK, Bouck* RM, Anderson AM, Bruno BA. Preparation and characterization of copper-containing alumina and silica aerogels for catalytic applications. Journal of Sol-Gel Science and Technology. 2017:1-4.

Catalytic, copper-impregnated alumina and silica aerogels were prepared. Alumina gels were prepared from a solution of aluminum chloride via an epoxide-assisted synthesis. Silica gels were fabricated from tetramethyl orthosilicate using a base-catalyzed approach to the hydrolysis and polycondensation reactions. Copper was introduced into the alumina and silica gels through exposure of the wet gel to a solution of copper(II) nitrate during a solvent-exchange step prior to aerogel formation via rapid supercritical extraction. Undoped silica and alumina aerogels were fabricated for comparison. A barrage of physical characterization methods were employed to analyze the aerogels as-prepared, following heat-treatment and following catalytic testing. These include bulk density, Brunauer-Emmett-Teller surface area, Barrett-Joyner-Halenda pore distribution, infrared spectroscopy, X-ray diffraction, and scanning electron microscopy with energy-dispersive X-ray spectroscopy. As-prepared copper-silica aerogels have density 0.11 g/cm³, surface area 780 m²/g, and 9-nm average pore diameter. As-prepared copper-alumina aerogels have density 0.09–0.11 g/cm³, surface area 430 m²/g, and 23-nm average pore diameter. Calcining to 800 °C results in 10% lower surface area and average pore size 22 nm for copper-silica aerogels, 70% lower surface area for copper–alumina aerogels and, in both types of materials, yields microcrystalline CuO. A catalytic testbed was employed to assess the suitability of the copper–alumina and copper–silica aerogels as three-way catalysts for eventual application in automotive pollution mitigation. Both copper–silica and copper–alumina aerogels performed as three-way catalysts.

Anderson AM, Donlon* EA, Forti* AA, Silva§ VP, Bruno BA, Carroll MK. 2017 “Synthesis and Characterization of Copper-Nanoparticle-Containing Silica Aerogel Prepared via Rapid Supercritical Extraction for Applications in Three-Way Catalysis,” MRS Advances. May:1-6.

Copper-alumina and copper-silica aerogels formed by impregnation of a copper(II) salt into an alumina or silica wet gel before supercritical extraction have been found to contain copper in multiple oxidation states: Cu0, Cu+1 and Cu+2. These aerogels are effective at catalyzing the reduction of NO and the oxidation of HCs and CO under conditions similar to those found in automotive three way catalysts. In this work we have developed a preparation method incorporating Cu0, Cu+1 and Cu+2 nanoparticles directly into silica aerogels. Nanoparticles in the form of (a) Cu0nanorods (100 nm diameter, 10-20 μm length); (b) Cu+1 nanoparticles (350 nm diameter); and (c) Cu+2 nanoparticles (25-55 nm diameter) were added (0.5-15% by weight) to separate precursor mixtures consisting of tetramethyl orthosilicate, methanol, water and ammonia. These precursor mixtures were then processed using a rapid supercritical extraction (RSCE) method to form aerogels. The resulting aerogels show evidence of nanoparticles dispersed throughout the silica aerogel structure. Addition of Cu+1 and Cu+2 nanoparticles decreases the surface area of the aerogels significantly. X-Ray diffraction shows that regardless of initial oxidation state of the nanoparticles, crystalline Cu0 is detected after RSCE processing to 290 °C. Following heat treatment at 700 °C, crystalline Cu+2 is detected. The copper containing silica aerogels are found to be catalytically active with light-off temperatures (50% conversion) for NO and CO at 400 °C in three-way catalytic applications.

Bouck* RM, Anderson AM, Prasad* C, Hagerman ME, Carroll MK. 2016 “Cobalt-alumina sol gels: Effects of heat treatment on structure and catalytic ability,” J Non Cryst Sol. 453: 94-102.

Cobalt-alumina (Co-Al) aerogel catalysts show potential as less expensive, sustainable alternatives to the platinum-group-metal catalysts used in three-way catalytic converters. Effects of heat treatment on the structure of Co-Al xerogels and aerogels and catalytic performance of Co-Al aerogels were investigated. Alumina gels were prepared by epoxide-assisted sol-gel synthesis, impregnated with ~ 3% cobalt, and either processed via rapid supercritical extraction to yield aerogels, or dried under ambient conditions to form xerogels. These materials were calcined at temperatures ranging from 400 °C to 1100 °C and characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, powder X-ray diffraction, thermogravimetric analysis and Brunauer-Emmett-Teller gas adsorption. When the aerogels and xerogels were heated to ~ 500 °C, crystalline portions of the alumina support underwent the expected phase transformation from boehmite to γ-alumina. Aerogels resisted further changes in samples heated to 1100 °C, whereas γ-alumina in the xerogels converted to α-alumina by 1100 °C. Heat-treated aerogels had high thermal stability, evidenced by their maintaining a surface area of 400 (± 30) m²/g after significant heating and resisting catalytically inhibiting θ/α-alumina phase changes. Color changes observed following heating are consistent with changes in cobalt-containing species within the materials. Preliminary catalytic tests showed that pre-heating Co-Al aerogels to 750 °C improves catalytic performance.

 

Bhuiya MM, Anderson AM, Carroll MK, Bruno BA, Ventrella* JL, Silberman* B, Keramati B, 2016, “Preparation of Monolithic Silica Aerogel for Fenestration Applications: Scaling up, Reducing Cycle Time, and Improving Performance,” Industrial & Engineering Chemistry Research. 55, 6971-6981. DOI: 10.1021/acs.iecr.6b00769

The ability of a rapid supercritical extraction (RSCE) process implemented in an industrial hot press to produce silica aerogel monoliths (AMs) with properties suitable for use in fenestration products was investigated. The effects of hot-press processing parameters such as press force and heat-up and cool-down rates on the size (area) and quality (presence of cracks and optical flaws) of the AMs produced, and on the manufacturing cycle times required to produce them, were studied. AMs of 14 × 14 × 1.27 cm were produced in a 6.5 h RSCE process using a laboratory scale (267 kN) hot press. Evacuated window prototypes were prepared by packaging aerogels in the interspaces of a double-glazing system under vacuum. The aerogels were found to have high translucency (>80% transmittance) in the red portion of the visible spectrum. The double-glazing evacuated aerogel windows were found to have thermal resistivity of 1.21–1.55 K·m²/W.

 

Bruno BA, Anderson AM, Carroll MK, Swanton* T, Brockmann* P, Palace* T & Ramphal IA, 2016, “Benchtop Scale Testing of Aerogel Catalysts: Preliminary Results,” SAE Technical Paper No. 2016-01-0920.

Aerogels are nanoporous structures with physical characteristics that make them promising for use in automotive exhaust catalysis systems: highly porous with low densities (<0.1 g/mL) and high surface area per unit mass (>300 m2/g) – features that provide favorable characteristics for catalysis of gaseous pollutants. Ceramic aerogels are also highly thermally insulating (∼0.015 W/mK) and able to withstand high temperatures. Aerogels can be made of a wide variety of ceramics (e.g. alumina, silica, titania) with other catalytically active metals (e.g. copper, cobalt, nickel) incorporated into their structures. This paper provides a brief overview of the rapid supercritical extraction (RSCE) method employed in this work for aerogel preparation, describes in detail the benchtop scale testbed and methods used to assess the catalytic activity of RSCE fabricated aerogels, and presents data on the catalytic ability of some promising aerogel chemistries. Catalyst performance in simulated gasoline engine exhaust was examined over temperatures ranging from 200 – 750°C, and space velocities of 15-30 s-1. Alumina aerogels fabricated via RSCE processing and incorporating non-precious metals such as copper and cobalt catalyze the oxidation of CO and UHCs, and the reduction of NO under conditions similar to those involved in automotive exhaust after-treatment applications. Copper-alumina aerogels show particular promise, yielding conversion percentages of NO and CO in excess of 90% over a wide range of experimental conditions, and appear to manifest potentially valuable oxygen storage capability.

 

Smith* LC, Anderson AM & Carroll MK, 2016, “Preparation of Vanadia Containing Aerogels by Rapid Supercritical Extraction for Applications in Catalysis.” Sol-Gel Sci. Technol, 77:160-171.

We have developed a variety of vanadia-containing aerogels using a rapid supercritical extraction method that employs a contained mold held within a hydraulic hot press. Sol–gels were prepared with silica, silica–titania, titania and alumina backbones using a variety of precursor chemicals: tetramethyl orthosilicate, tetraethyl orthosilicate, vanadyl acetylacetonate, titanium (IV) butoxide and titanium (IV) isopropoxide. Total fabrication time (including processing) was ca. 9 h for sol–gels prepared without solvent exchange. When sol–gel aging and solvent exchange steps are employed, the overall fabrication time was on the order of several days. The aerogels were characterized by physical appearance (color), bulk density, Brunauer–Emmett–Teller surface area, Barrett–Joyner–Halenda pore distribution, scanning electron microscopy and Fourier transform infrared spectroscopy. All of the resulting aerogels have average bulk densities below 0.12 g/cm³ and surface areas ranging from 500 to 770 m²/g, with the exception of the vanadia–titania materials, which have surface areas of 140 m²/g. Variation in speciation and complexation of vanadia in the resulting aerogels is evidenced by significant differences in color observed for various precursor recipes and processing conditions. Preliminary catalytic testing under conditions that mimic automotive exhaust gas indicates that the aerogels are catalytically active for the oxidation of hydrocarbons and carbon monoxide and the reduction of nitrogen oxides.

 

Juhl* SJ, Dunn* NJH, Carroll MK, Anderson AM, Bruno BA, Madero* JE, & Bono* MS, 2015 “Epoxide-Assisted Alumina Aerogels by Rapid Supercritical Extraction.” J Non Cryst Sol, 426:141–149.

Aerogels offer a potential alternative to noble metals that could reduce both the cost and environmental impact associated with catalytic converter production. The environmental impact of the production of aerogel catalysts could be further reduced by using a rapid supercritical extraction (RSCE) technique, which reduces the time and solvent waste associated with aerogel preparation. Alumina aerogels, which have shown activity in catalyzing exhaust processing reactions, were prepared using an epoxide-assisted gelation technique with RSCE processing in a contained mold in a hydraulic hot press. Samples were characterized by FTIR, XRD, SEM, EDX, nitrogen adsorption porosimetry and pycnometry. Solvent characterization by GC–MS headspace analysis shows that excess propylene oxide and chloropropanol products of an irreversible epoxide ring-opening reaction are present in the alumina gel following gelation, but can be removed via solvent exchange. Alumina aerogels with surface areas as high as 790 m²/g and bulk densities as low as 0.05 g/mL were prepared. Preliminary characterization of these aerogels, utilizing a catalytic test bed and a simulated emission gas blend, demonstrates that they have moderate ability for removal of hydrocarbons, carbon monoxide and nitrogen oxide.

Justin E. Rodriguez**, Ann M. Anderson, and Mary K. Carroll  “Hydrophobicity and Drag Reduction Properties of Surfaces Coated with Silica Aerogels and Xerogels” Journal of Sol-Gel Science and Technology, 2014, 71, 490-500.

 

Suzanne K. Estok*, Thomas A. Hughes IV§, Mary K. Carroll and Ann M. Anderson  “Fabrication and Characterization of TEOS-Based Silica Aerogels Prepared using Rapid Supercritical Extraction.”  Journal of Sol-Gel Science and Technology, 2014, 70(3), 371-377.

 

Mary K. Carroll, Ann M. Anderson and Caroline A. Gorka*  “Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method.”  Journal of Visualized Experiments, 2014, 84, DOI:  10.3791/51421.

 

Lauren B. Brown*, Ann M. Anderson and Mary K. Carroll,  “Fabrication of Titania and Titania-Silica Aerogels using Rapid Supercritical Extraction.”  Journal of Sol-Gel Science and Technology, 2012, 62(3), 404-413.

 

Ondrej Nikel**, Ann M. Anderson, Mary K. Carroll and William D. Keat  “Effect of Uni-axial Loading on the Nanostructure of Silica Aerogels.”  Journal of Non-Crystalline Solids, 2011, 357(16-17), 3176-3183.

 

Michael S. Bono, Jr.*, Ann M. Anderson, and Mary K. Carroll  “Alumina Aerogels Prepared via Rapid Supercritical Extraction.”  J. Sol-Gel Sci. Technol., 2010, 53(2), 216-226.

 

Ann M. Anderson, Mary K. Carroll, Emily C. Green*, Jason T. Melville*, and Michael S. Bono*, “Hydrophobic Silica Aerogels Prepared via Rapid Supercritical Extraction.”   J. Sol-Gel Sci. Technol., 2010, 53(2), 199-207.

 

Ann M. Anderson, Caleb W. Wattley* and Mary K. Carroll, “Silica Aerogels Prepared via Rapid Supercritical Extraction:  Effect of Process Variables on Aerogel Properties.” J. Non-Cryst. Solids, 2009, 355(2), 101-108.

 

Timothy B. Roth*, Ann M. Anderson and Mary K. Carroll, “Analysis of a Rapid Supercritical Extraction Aerogel Fabrication Process:  Prediction of Thermodynamic Conditions during Processing.” Journal of Non-Crystalline Solids, 2008, 354, 3685-3693.

 

Ann M. Anderson, Timothy B. Roth*, Matthew R. Ernst*, and Mary K. Carroll, “Saturated Liquid Densities and Vapor Pressures of Tetramethylorthosilicate Measured Using a Constant Volume Apparatus.”  Journal of Chemical & Engineering Data, 2008, 53, 1015-1020.

 

Desiree L. Plata*, Yadira J. Briones*, Rebecca L. Wolfe*, Mary K. Carroll, Smitesh D. Bakrania*, Shira G. Mandel*, and Ann M. Anderson, “Aerogel-Platform Optical Sensors for Oxygen Gas.” Journal of Non-Crystalline Solids, 2004, 350, 326-335.

 

Ann M. Anderson, Smitesh D. Bakrania*, Jan Konecny*, Ben M. Gauthier*, and Mary K. Carroll, “Detecting Sol-Gel Transition using Light Transmission.” Journal of Non-Crystalline Solids, 2004, 350, 259-265.

 

Ben M. Gauthier*, Smitesh D. Bakrania*, Ann M. Anderson, and Mary K. Carroll, “A Fast Supercritical Extraction Technique for Aerogel Fabrication.” Journal of Non-Crystalline Solids, 2004, 350, 238-243.

 

 

Conference Publications

 

Key: * indicates undergraduate student co-author; ** indicates MSME student co-author; § indicates high-school student co-author.

2. A. Bruno, J. E. Madero*, S. J. Juhl*, J. Rodriguez**, N. J. H. Dunn*, M. K. Carroll and A. M. Anderson, “Alumina-Based Aerogels as Three-Way Catalysts.”  Conference proceedings of the Ninth International Congress on Catalysis and Automotive Pollution Control (CAPoC9), August 2012.

 

Nicholas J. H. Dunn*, Mary K. Carroll and Ann M. Anderson, “Characterization of Alumina and Nickel-Alumina Aerogels Prepared via Rapid Supercritical Extraction.”  Polymer Preprints, 2011, 52(1), 250-251.

 

Mary K. Carroll and Ann M. Anderson, “Use of a Rapid Supercritical Extraction Method to Prepare Aerogels from Various Precursor Chemistries.”  Polymer Preprints, 2011, 52(1), 31-32.

 

Ondrej Nikel*, Ann M. Anderson and Mary K. Carroll, “Optical Investigation of Gelation During Rapid Supercritical Extraction Processing of Silica Aerogels.”  Polymer Preprints, 2008, 49(2), 560-561.

 

 

Patents

 

Ben M. Gauthier, Ann M. Anderson, Smitesh Bakrania, Mary K. Mahony (Carroll), and Ronald B. Bucinell  “Method And Device For Fabricating Aerogels And Aerogel Monoliths Obtained Thereby”  US 7,384,988 B2.   June 10, 2008.

 

Ben M. Gauthier, Ann M. Anderson, Smitesh Bakrania, Mary K. Mahony (Carroll), and Ronald B. Bucinell  “Method And Device For Fabricating Aerogels And Aerogel Monoliths Obtained Thereby”  US 8,080,591.  December 20, 2011.

 

 

Book Chapters

 

Ann M. Anderson and Mary K. Carroll, “Hydrophobic silica aerogels:  Review of synthesis, properties and applications.”  Ch. 3 in the Aerogels Handbook, M.A. Aegerter, N. Leventis, Nicholas and M. Koebel (Eds.), Springer, June 2011.

 

Mary K. Carroll and Ann M. Anderson, “Aerogels as Platforms for Chemical Sensors.”  Ch. 27 in the Aerogels Handbook, M.A. Aegerter, N. Leventis, Nicholas and M. Koebel (Eds.), Springer, June 2011.