Synthesis, Characterization, Modeling and Applications of Functional Porous Materials: Porous Materials II
Sponsored by: ACerS Basic Science Division
Program Organizers: Lan Li, Boise State University; Winnie Wong-Ng, National Institute of Standards and Technology; Kevin Huang, University of South Carolina
Monday 2:00 PM
October 10, 2022
Room: 325
Location: David L. Lawrence Convention Center
Session Chair: Winnie Wong-Ng, National Institute of Standards and Technology (NIST)
2:00 PM Invited
Crystal Packing and Porosity in Molecular Co-crystals Based on C60 Fullerene: Lawrence Cook1; Greg Brewer1; Winnie Wong-Ng2; 1Catholic University of America; 2National Institute of Standards and Technology
Relative to framework structures, which must conform to the topological requirements imposed by ionic or covalent bonding, a greater range of crystal packing arrangements is possible in molecular compounds, due to the less restrictive nature of their cohesive forces. A large number of three-dimensional molecular motifs is available for crystal packing to form molecular crystals, which however must satisfy the underlying thermodynamic requirements for chemical stability. Since porosity is closely related to crystal packing, there are extended possibilities for formation of molecular structures with technologically significant porosity. In this study we examine the crystal packing and porosity in relatively simple molecular co-crystals based on pristine C60 fullerene in combination with other molecules having various dimensional attributes.
2:30 PM
Mesoscopic Simulations of Tension and Compression of Cross-Linked Carbon Nanotube Films: Effects of the Nanotube Chirality: Kevin Kayang1; Abu Banna1; Alexey Volkov1; 1The University of Alabama
The effect of the carbon nanotube (CNT) chirality on the mechanical properties of thin films composed of single-walled CNTs with covalent cross-links is studied based on a multiscale approach that involves atomistic and mesoscopic models. The atomistic simulations are performed to study the shear load transfer in bundles of cross-linked CNTs of various chirality and parameterize a mesoscopic model of cross-links in CNT materials. Large-scale simulations of in-plane tension and compression of CNT films composed of thousands of nanotubes are performed based on a coarse-grained model of CNT network materials. The simulations show that the elastic and inelastic mechanical properties of cross-linked CNT films strongly depend on the CNT radius. It is found that the film modulus increases with increasing CNT radius, while the tensile strength decreases. The obtained results suggest that the optimization of mechanical properties of CNT materials can be achieved by tuning the nanotube chirality distribution.
2:50 PM Invited
Porous Solids with Nanostructured Surfaces for Environmental Applications: Sharmila Mukhopadhyay1; Wenhu Wang1; Mallikarjuna Nadagouda2; 1University of Maine; 2USEPA
This talk will focus on the multi-scale structural and functional aspects of porous three-dimensional carbon solids, where the pore surfaces are enhanced with covalently bonded carpet-like arrays of carbon nanotubes. This fractal surface geometry shows multiple advantages such as increased adsorption, improved mechanical interlocking with surrounding matrix, and increased thermal/electrical exchange with the surrounding. When the CNT arrays are further functionalized with catalytic nanoparticles, these materials act as highly active catalysts and sensors. One of the applications discussed will be catalytic degradation of environmental pollutants, where such materials have been activated with palladium nanoparticles and used to degrade halogenated pollutants such as atrazine, triclosan and carbon tetrachloride in water. Rapid and complete dechlorination is observed at ambient temperature. Moreover, repeatability tests show no evidence of material deterioration or catalyst degradation with multiple use. These materials therefore provide an ecofriendly, reusable, and cost-effective solution for pollutant control.
3:10 PM
Carbon Fibers Loaded Epoxy Foam: From Dielectric Characterization to Electromagnetic Absorption Application: Ratiba Benzerga1; Chloé Méjean1; Laura Pometcu1; Philippe Pouliguen2; Ala Sharaiha1; 1University of Rennes, IETR; 2DGA/DS
The form and composition of electromagnetic absorbers are various and depend on the targeted application. Pyramidal absorbers made of flexible polyurethane foam impregnated with a carbon solution are currently used for anechoic chambers. This paper presents an alternative absorbing material developed from epoxy foam and carbon fibers. The rigid foam was chosen because it can be machined with a complex geometry which enhances absorption performance. Furthermore, our process enables the complete embedding of the fibers which prevents any leak. Here, composites loaded with carbon fibers of different lengths (0.1 to 12mm) were achieved and their dielectric properties (permittivity and dielectric losses) were measured in the 2–18GHz frequency range. Therefore, simulations were performed to estimate the absorption performances of a pyramidal absorber and also a newly designed geometry. The simulation and measurement results of prototypes showed excellent performance with an equivalent even better absorption than the most used commercial absorber
3:30 PM Break
3:50 PM Invited
New Ceramic-Carbonate Membranes for Direct and Selective Capture of Low Concentration CO2: Kevin Huang1; Shichen Sun1; Kangkang Zhang1; 1University of South Carolina
The molten carbonate based multiphase membranes for CO2 capture/separation/conversion have been researched for nearly fifteen years. The major advantages of this class of CO2 transport membranes (CTMs) are that the capture process is purely chemical potential driven and thus electricity free and they are not subject to “Robeson Upper Bound “ rule due to their electrochemical transport nature. Early laboratory studies with 15%CO2 in the feedstock have shown these CTMs with high CO2 flux at very high selectivity. Recently, efficiently capturing low-concentration (4-5%) of CO2 from natural gas flue gas has become urgent. Here in this presentation, we show a new class of CTMs well suited for this purpose.
4:20 PM Invited
Integrated Multi-characterization Approach to Understand Pore Size Distributions in Ceramic Composite Membranes: V. V. Rohit Bukka1; Christine Brockman1; Pankaj Sarin1; 1Oklahoma State University
Composites made from porous materials have the advantage of tunable pore size distributions which can determine the overall permeability. This study focuses on low-cost micro/ultra-filtration membranes made with natural zeolite (clinoptilolite) particles (<45 microns) in ceramic geopolymer matrix. The membranes were processed as a thin layer of the composite coated on a perforated aluminum sheet and cured under pressure at 60°C at 80% relative humidity. The porosity was tailored by varying the clinoptilolite content. The membrane microstructure, spatial distribution of zeolite particles, and macroporosity were evaluated using SEM and X-ray micro-CT. Gas adsorption and mercury intrusion porosimetry were used to characterize micro and mesoporosity, pore-size distributions and permeability. In this presentation, an integrated approach to understanding porosity, pore distribution, and permeability in these ceramic membranes will be discussed. In addition, results from both dead-end and continuous cross-flow filtration studies on produced water will be presented to compare membrane performance.
4:50 PM
Modeling Transport Characteristics of RO Membranes Using Macrovoid Resolved Simulations: Vimal Ramanuj1; Ramanan Sankaran1; Luka Malenica1; Kyle Cole1; Marc Day2; Jeffrey McCutcheon3; 1Oak Ridge National Laboratory; 2National Renewable Energy Laboratory; 3University of Connecticut
The transport characteristics of a reverse osmosis (RO) membrane are known to be highly dependent on the microstructures specifically, the topology of macrovoids resulting from specific manufacturing methods or changes due to compaction in High Pressure Reverse Osmosis (HPRO). The presentation will focus on high resolution computational studies of HPRO relevant membrane geometries with emphasis on flow characteristics including channeling effects due to the presence of macrovoids. Flow channeling is observed when the heterogeneity in the porous structure leads to locally high permeability paths. Synthetic microstructures are constructed to statistically capture the geometric features of a two-scale porous membrane based on published experimental visualizations. Simulations are conducted over a range of parameters to capture transition of flow characteristics from material governed to macrovoid governed. Computed tortuosity and permeability are analyzed, and an enhanced model based on flux-weighted porosity is proposed and compared with existing correlations from literature.
5:10 PM
Optimizing Surfactant Templating of Yttria-Stabilized Zirconia Aerogels for High-temperature Applications: Effect of Anionic, Nonionic Surfactants: Rebecca Walker1; Jamesa Stokes2; Frances Hurwitz2; Haiquan Guo3; James Ferri1; 1Virginia Commonwealth University; 2NASA Glenn Research Center; 3Universities Space Research Association
Aerogels are useful thermal insulators due to low density, low thermal conductivity, and a tortuous path for solid conduction. However, the formulation must be optimized to increase thermal stability as drastic densification and surface area decrease is often exhibited after high-temperature exposure. Current research investigates yttria-stabilized zirconia (YSZ) aerogels for expected use between 600°C and 1000°C. We anticipate that new sol-gel chemistries will yield YSZ aerogels with retained mesoporous structure, increased surface area, and minimized shrinkage upon high-temperature exposure. This work investigates the anionic surfactant, sodium dodecyl sulfate (SDS), and the nonionic surfactant, Pluronic® P-123, as templating agents to prevent the collapse of the aerogel pore structure upon gelation and drying. To determine the effect of surfactant, characterization techniques such as nitrogen physisorption, x-ray diffraction, and scanning electron microscopy are used. By optimizing surfactant concentration, the thermal stability of YSZ aerogels can be enhanced, producing more efficient thermal insulators.