Ethylene is the petrochemical compound with the highest production worldwide. Whether reactors are heated by direct fired heating or indirect heating via steam, manufacturers rely on economies of scale to overcome inherent thermodynamic inefficiencies while burning fossil fuels. New approaches to supply energy to chemical reactor systems can reduce energy waste created by traditional techniques while enabling large scale facilities to use other sources of raw materials and energy. Electromagnetic (EM) induction heating is one potential solution for providing energy efficiently to reactor systems. By taking advantage of the nature of radio frequency (RF) waves, heterogeneous-catalyst can be precisely targeted for heating inside the reactors. Site-selective heating can significantly reduce the energy requirements of the process by providing heat at reaction sites and reducing unnecessary heat transfer elsewhere. Other advantages to an EM enhanced system include rapid volumetric heating, broader turn-down capacity, and reduced process footprint. The purpose of this work is to establish a multiscale computational fluid dynamics (CFD) model that can be used to emulate the proposed process mechanics at the macroscale and microscale. At the macroscale, coil geometry (coil diameter, gap between coils, distance between coil and susceptors) is investigated to elucidate coil design and effects on heating rates. In the microscale, the oxidative (CO 2 ) dehydrogenation (ODH) of ethane is explored using different catalysts and possible catalyst/susceptor configurations with heat supplied by an EM susceptor. This multiscale method can also be applied to electrochemical systems.

We have developed a novel green synthetic method to covalently graft fluorographite (FGi) nanoplatelets, with quaternary ammonium polyelectrolyte chains under mild reaction conditions in water. Radical centers on the fluorographite layers react with the radical chain end on short strands of anion-exchange resins. While fluorographite is superhydrophobic, we show that the polymer radical chain end is necessary to initiate defluorination and delamination of the FGi in neutral pH water, without any pretreatment or caustic reagents. Scanning electron microscopy of thin films shows continuous and organized stacking of ellipsoidal nanoplatelets across large defect-free areas. We show that these new materials are highly effective at removing known and emerging contaminants to below environmentally relevant concentrations. Electron microscopy, vibrational spectroscopy, elemental analysis, and thermal analysis data are presented, and they are consistent with defluorination, partial exfoliation, and graphitization during the aqueous polymer grafting reaction. A radical-initiated mechanism is proposed that is consistent with the observed defluorination and oxidation of FGi nanoplatelets. The physicochemical properties, water flux, and morphology of these thin-film assemblies are described in detail. Thin membranes of polymerfunctionalized fluorographite removed 99% of perfluorooctanoic acid to below 100 parts per trillion while maintaining a very high water flux over 1100 L h(-1)m(-2) bar(-1). Percent removal of perfluorinated alkyl substances and heavy metal oxyanions versus polyelectrolyte-fimctionalized fluorographite membrane areal density is reported. The methodology presented in this study is a facile approach toward developing high-performance materials for sustainable and green applications.

This paper focuses on the utilization of carbon nanotubes for the fabrication of thin-film transistors (TFTs) using a direct-write inkjet process. Single-walled carbon nanotubes (SWNTs) are well regarded for their superior electrical, magnetic, and thermal properties. The development of TFTs requires high carrier mobility comparable to that of SWNTs (100,000 cm(2)/V.s) which can be doped as both n- and p-types. We have enriched semiconducting SWNTs (s-SWNTs) into specific chiralities to provide a consistent band gap required for the fabrication of transistors with reproducible electrical properties. In this research, we investigate the use of direct-write inkjet to deposit enriched s-SWNTs on Kapton substrates to fabricate flexible thin-film transistors (fTFTs). The direct writing technique provides accurate deposition control and reproducibility to print s-SWNTs over large areas. Optical and atomic force microscopy images identify threshold of nanotube bundle connectivity for different deposition configurations. We demonstrate the fabrication of SWNT traces with varying conductivity and transport characteristics towards large-scale fTFTs.

Freestanding few layer graphene platelet/polyvinylidene fluoride composites have been synthesized, resulting in flexible, light weight, and durable electrically conducting films. These composites exhibit reasonable thermoelectric properties including a maximum electrical conductivity of 2005 S m(-1), Seebeck coefficient of 18.3 mu V K-1, and power factor of 0.52 mu W m(-1) K-2. The temperature dependent behavior of these properties is also investigated. The electrical conductivity of the composites exhibits thermal fluctuation-assisted tunneling behavior coupled with a high energy phonon scattering term, while the thermoelectric power is characterized by electron-phonon enhanced metallic diffusion thermopower plus a phonon drag term. This results in a characteristic change in majority charge carrier type from hole to electron as the temperature decreases below 60 K. These composites have the potential to be used in low power applications where sufficient waste heat is available. (c) 2013 Published by Elsevier B.V.

Multiwalled carbon nanotubes (MWNTs) have been grown using a standard chemical vapor deposition method, except for varying the growth temperature. Nanotubes grown below 770 °C exhibit typical positive thermoelectric powers, while those grown above have negative values. This behavior is attributed to the larger nanotube diameters observed at higher growth temperatures. Below 770 °C, the average nanotube diameter is about 50 nm, while above, nanotubes reach diameters of 300 nm. This increase in diameter and number of inner shells leads to the intrinsic negative thermoelectric power of the inner nanotube shells becoming larger than the positive thermoelectric power due to oxygen doping on the outer surface of the nanotube. The overall negative thermopower (about −6 μV/K, compared to +7 μV/K for smaller diameter nanotubes) can be understood in terms of a parallel conduction model. Our large-diameter multiwalled carbon nanotubes allow the intrinsic negative thermopower of MWNTs to be accessed without requiring specific deoxygenation treatment.

Thermoelectrics are materials capable of the solid-state conversion between thermal and electrical energy. Carbon nanotube/polymer composite thin films are known to exhibit thermoelectric effects, however, have a low figure of merit (ZT) of 0.02. In this work, we demonstrate individual composite films of multiwalled carbon nanotubes (MWNT)/polyvinylidene fluoride (PVDF) that are layered into multiple element modules that resemble a felt fabric. The thermoelectric voltage generated by these fabrics is the sum of contributions from each layer, resulting in increased power output. Since these fabrics have the potential to be cheaper, lighter, and more easily processed than the commonly used thermoelectric bismuth telluride, the overall performance of the fabric shows promise as a realistic alternative in a number of applications such as portable lightweight electronics.

Resistivity and thermoelectric power (TEP) measurements were conducted on single walled carbon nanotube (SWNT), polyvinylidene fluoride composite thin films of varying SWNT concentrations. This heterogeneous material was used in order to utilize the good electrical conductance of the nanotubes and the poor thermal conductance of the polymer to increase the figure of merit (ZT). As the nanotube weight percent decreased from 100% to 5%, the beneficial effects of the TEP increase and thermal conductivity decrease outweighed the negative effect of decreased electrical conductivity, resulting in an increase in ZT by a factor of 100.

An electron donor/acceptor pi-conjugated polymer composed of a bi-EDOT and benzobis(thiadiazole) repeat unit exhibits two reductions with a band gap ranging from approximately 0.5 to 0.8 eV depending on the method of band gap determination.

Crosslinked gels (hylans) containing long-chain (MW>1×106Da) hyaluronan (HA), a connective tissue GAG, show exceptional biocompatibility for vascular implantation but poorly interact with vascular endothelial cells (ECs). Previous studies showed in situ fragmentation of HA by UV light to bioactivate hylan gels and elicit enhanced EC responses. Since fragmented HA can be pro-inflammatory, it is important to define an optimal size distribution of HA fragments on the hylan surface that will recruit and support normally functional ECs and limit ulterior responses. Related studies have shown that exogenous models of HA do not necessarily replicate cell responses to HA scaffolds. Since scaffolds cannot be created based on fragmented HA alone, we sought to determine size-specific responses of ECs to HA substrates of defined fragment sizes by creation of HA-tethered culture surfaces. HA (1000, 200, 20kDa) and an oligomer mixture were tethered onto an aminosilane (APTMS)-treated glass surfaces using a carbodiimide reaction. MALDI–TOF showed the HA digests to contain HA 4–8mers with a 75±0.4% w/w of 4mers. Immuno-fluorescence, SEM, AFM and XPS analysis revealed homogeneous amine and HA surfaces. An amine s-SDTB assay and HA fluorophore-assisted carbohydrate electrophoresis (FACE) indicated surface densities of 9±3 amine groups/nm2 and 0.57±0.44μg/cm2, respectively. HA/HA fragments/oligomers were stable over 21 days of incubation in serum-free culture media. EC proliferation on these surfaces resulted was limited, a possible effect of smooth surface topography, high anionicity, and in case of 4mers, non-interaction with primary HA cell–surface receptors (CD44). This work is significant in that it allows testing of cell responses to substrates composed of single-sized fragments of HA that cannot by themselves be cross-linked into a gel. Future work in our lab will use this model to assess the effects of other HA oligomer sizes on EC behavior.