Zapata J.A.H.,University of Oklahoma |
Silvy R.P.,SouthWest NanoTechnologies (SWeNT) |
Grady B.P.,University of Oklahoma
Annual Technical Conference - ANTEC, Conference Proceedings | Year: 2015
The effect of nanotube preparation method (freeze drying (FD) vs. oven drying (OD) during synthesis) and length of three multi-walled carbon nanotubes (MWCNTs) on the dispersion and further on the percolation and mechanical behavior of polycarbonate (PC)/ MWCNTs composites was investigated. Nanocomposites were melt mixed in a twin-screw micro-compounder at concentration of 0.1-3.0 wt% MWCNTs. Tensile strength was independent of MWCNT concentration while the Young's modulus slightly increases and strain at break appreciable decreases when compare with pure PC. Scanning electron microscopy (SEM) and light microscopy (LM) micrographs revealed that at sub-micron scale shorter MWCNTs were found to be better dispersed than longer tubes, while at the macro scale the dispersion of long and short MWCNTs was comparable. Also, MWCNTs prepared by oven drying methods were found to be better dispersed at the submicron scale. Nanotubes with longer lengths (or aspect ratio (AR)) exhibited higher percolation thresholds (pcS) irrespective of differences in dispersion.
Godwin H.,University of California at Los Angeles |
Nameth C.,University of California at Los Angeles |
Avery D.,University of California at Los Angeles |
Bergeson L.L.,Bergeson and Campbell |
And 28 more authors.
ACS Nano | Year: 2015
For nanotechnology to meet its potential as a game-changing and sustainable technology, it is important to ensure that the engineered nanomaterials and nanoenabled products that gain entry to the marketplace are safe and effective. Tools and methods are needed for regulatory purposes to allow rapid material categorization according to human health and environmental risk potential, so that materials of high concern can be targeted for additional scrutiny, while material categories that pose the least risk can receive expedited review. Using carbon nanotubes as an example, we discuss how data from alternative testing strategies can be used to facilitate engineered nanomaterial categorization according to risk potential and how such an approach could facilitate regulatory decision-making in the future. © 2015 American Chemical Society.
Arthur D.,SouthWest NanoTechnologies (SWeNT) |
Silvy R.P.,SouthWest NanoTechnologies (SWeNT) |
Wallis P.,SouthWest NanoTechnologies (SWeNT) |
Tan Y.,SouthWest NanoTechnologies (SWeNT) |
And 5 more authors.
MRS Bulletin | Year: 2012
Whereas efforts toward graphene commercialization are still in their early stages, lessons from the commercialization of carbon nanotubes (CNTs) might be applicable, given the similarities between the two materials (specifically, a single-walled CNT can be thought of as a monolayer of graphene wrapped into a cylinder). This article reviews the commercialization of CNT materials (with a special emphasis on single-walled CNTs) in selected electronics applications, including specific examples of successes, failures, and promising opportunities. Two application areas are reviewed: (1) alternatives to silicon for fabricating transistors used in display backplanes, radio-frequency identification, and smart cards, for example, and (2) alternatives to indium tin oxide for transparent conductive films used in displays, electronic paper for e-readers, touch sensors, light-emitting diode lighting, photovoltaics, and electrochromic windows. Some important lessons learned from these commercialization experiences can potentially help accelerate the commercialization of other exciting nanomaterials such as graphene. © Copyright 2012 Materials Research Society.
PubMed | German Federal Institute for Risk Assessment, SouthWest NanoTechnologies (SWeNT), Lockheed Martin, Brown University and 15 more.
Type: Journal Article | Journal: ACS nano | Year: 2015
For nanotechnology to meet its potential as a game-changing and sustainable technology, it is important to ensure that the engineered nanomaterials and nanoenabled products that gain entry to the marketplace are safe and effective. Tools and methods are needed for regulatory purposes to allow rapid material categorization according to human health and environmental risk potential, so that materials of high concern can be targeted for additional scrutiny, while material categories that pose the least risk can receive expedited review. Using carbon nanotubes as an example, we discuss how data from alternative testing strategies can be used to facilitate engineered nanomaterial categorization according to risk potential and how such an approach could facilitate regulatory decision-making in the future.
Castillo F.Y.,University of Oklahoma |
Socher R.,Leibniz Institute of Polymer Research |
Krause B.,Leibniz Institute of Polymer Research |
Headrick R.,SouthWest NanoTechnologies (SWeNT) |
And 3 more authors.
Polymer | Year: 2011
Five commercially available multi-walled carbon nanotubes (MWNTs), with different characteristics, were melt mixed with polycarbonate (PC) in a twin-screw micro compounder to obtain nanocomposites containing 0.25-3.0 wt.% MWNT. The electrical properties of the composites were assessed using bulk electrical conductivity measurements, the mechanical properties of the composites were evaluated using tensile tests and dynamic mechanical analysis (DMA), and the thermal properties of the composites were investigated using differential scanning calorimetry (DSC). Electrical percolation thresholds (pcs) were observed between 0.28 wt.% and 0.60 wt.%, which are comparable with other well-dispersed melt mixed materials. Based on measurements of diameter and length distributions of unprocessed tubes it was found that nanotubes with high aspect ratios exhibited lower pcs, although one sample did show higher pc than expected (based on aspect ratio) which was attributed to poorer dispersion achieved during mixing. The stress-strain behavior of the composites is only slightly altered with CNT addition; however, the strain at break is decreased even at low loadings. DMA tests suggest the formation of a combined polymer-CNT continuous network evidenced by measurable storage moduli at temperatures above the glass transition temperature (T g), consistent with a mild reinforcement effect. The composites showed lower glass transition temperatures than that of pure PC. Lowering of the height of the tanδ peak from DMA and reductions in the heat capacity change at the glass transition from DSC indicate that MWNTs reduced the amount of polymer material that participates in the glass transition of the composites, consistent with immobilization of polymer at the nanotube interface. © 2011 Elsevier Ltd. All rights reserved.
Silvy R.P.,SouthWest NanoTechnologies (SWeNT)
Oil and Gas Journal | Year: 2010
The global refining catalyst market 2010-13 shows signs of recovering, based on an analysis of the world's oil refining operations 1999-2009 that established future trends in catalyst spending. World crude distillation capacity will rise to 90.8 million b/d in 2013 from 87.2 million b/d in 2009, a rate of 1.03%/year. Hydrotreating, catalytic cracking, hydrocracking, and naphtha reforming process capacities will increase to 49.24 million b/d, 14.99 million b/d, 6.73 million b/d. Expansion of current refineries and construction of new hydrotreaters, hydrocrackers, FCCUs, and naphtha reformers units will add about 2,084 million b/d, 607,000 b/d, 122,000 b/d, and 240,000 b/d, respectively, to global refining capacity by 2013. Oil production recovered after 2002, increasing to 72.5 million b/d in 2006, growing at 1.63 million b/d/year. Asia Pacific and North American regions experienced the largest average refinery capacity growth during 1999-2009.
Guo J.,University of Oklahoma |
Liu Y.,University of Oklahoma |
Prada-Silvy R.,SouthWest NanoTechnologies (SWeNT) |
Tan Y.,SouthWest NanoTechnologies (SWeNT) |
And 4 more authors.
Journal of Polymer Science, Part B: Polymer Physics | Year: 2014
Two multi-walled carbon nanotubes (MWCNTs) having relatively high aspect ratios of 313 and 474 with approximately the same diameter were melt mixed with polycarbonate (PC) in a twin-screw conical micro compounder. The effects of aspect ratio on the electrical, mechanical, and thermal properties of the PC/MWCNT composites were investigated. Electrical conductivities and storage moduli of the filled samples are found to be independent of the starting aspect ratio for these high aspect ratio tubes; although the conductivities and storage moduli are still significantly higher than values of composites made with nanotubes having more commercially common aspect ratios of ∼100. Transmission electron microscopy results suggest that melt-mixing reduces these longer nanotubes to the same length, but still approximately two times longer than the length of commercially common aspect ratio tubes after melt-mixing. Molecular weight measurements show that during melt-mixing the longer nanotubes significantly degrade the molecular weight of the polymer as compared to very similar nanotubes with aspect ratio ∼100. Because of the molecular weight reduction glass transition temperatures predictably show a large decrease with increasing nanotube concentration. © 2013 Wiley Periodicals, Inc.
SouthWest NanoTechnologies (SWeNT) | Date: 2015-06-16
The present invention provides a catalyst precursor and a catalyst suitable for preparing multi-wall carbon nanotubes. The resulting multi-wall carbon nanotubes have a narrow distribution as to the number of walls forming the tubes and a narrow distribution in the range of diameters for the tubes. Additionally, the present invention provides methods for producing multi-wall carbon nanotubes having narrow distributions in the number of walls and diameters. Further, the present invention provides a composition of spent catalyst carrying multi-wall nanotubes having narrow distribution ranges of walls and diameters.
Agency: Department of Commerce | Branch: National Institute of Standards and Technology | Program: SBIR | Phase: Phase I | Award Amount: 89.96K | Year: 2014
Single-walled carbon nanotubes (SWCNTs) have unique material properties making them very attractive for use in a variety of electronic applications. However, as-grown SWCNTs contain a mixture of tubes with heterogeneous optical and electronic properties. The chiral species must be separated in order to maximize the desired properties. To date, no large scale separation process has been accomplished. This Phase I project seeks to extend the promising technique developed at NIST to demonstrate single-chirality CNT separation, at laboratory scale.