1,720,969 research outputs found
Fabrication and Characterization of Aging Resistant Carbon Molecular Sieve Membranes for C₃ Separation Using High Molecular Weight Crosslinkable Polyimide, 6FDA-DABA
No full textDue to copyright restrictions full text access from Treasures at UT Dallas is restricted to current UTD affiliates (use the provided Link to Article).Although propylene/propane separation remains a challenge for industrial processes, carbon molecular sieve membranes (CMSMs) have the potential to replace traditional separation methods. A high molecular weight crosslinkable polyimide was utilized to fabricate CMSMs, which showed pure gas permeabilities in excess of 400 barrers with propylene/propane selectivities as high as 25. Mixed gas (C₃H₈:C₃H₆ 50:50) measurements yielded a propylene permeability of 257 barrers and a selectivity of 20. CMSMs from thermally precrosslinked polymer precursors demonstrated a 98% propylene permeability retention after aging for 20 days under vacuum. Active gas flow conditions resulted in slightly lower permeability retention (92.5%) after 15 days of testing. ©2019 Elsevier B.V.NSF (CBET-1403950)School of Natural Sciences and Mathematic
Biphenyl-Bridged Wrinkled Mesoporous Silica Nanoparticles for Radioactive Iodine Capture
No full textDue to copyright restrictions and/or publisher's policy full text access from Treasures at UT Dallas is not available. UTD affiliates may be able to acquire a copy through Interlibrary Loan by using the link to UTD ILL.The capture of volatile radioactive iodine-129 is an important process for nuclear fission. Biphenyl-bridged wrinkled mesoporous silica shows similar performance for iodine sequestration to commercial Ag-mordenite and avoids the use of expensive silver The biphenyl-wrinkled mesoporous silica nanoparticles function as a scaffold for biphenyl groups and also as a fluorescent indicator for the loading of iodine. The nanoparticles have a surface area of 973 m²/g and the biphenyl molecules form an electron charge-transfer complex with iodine. Iodine was loaded into the biphenyl-bridged wrinkled mesoporous silica (BUMS) at 19 ± 0.2 % loading by mass.School of Natural Sciences and MathematicsErik Jonsson School of Engineering and Computer Scienc
Synthesis and Characterization of a Holmium 2,2′-bipyridine-5,5′-dicarboxylate MOF: Towards the Construction of a Suitable Holmium Carrier
No full textDue to copyright restrictions and/or publisher's policy full text access from Treasures at UT Dallas is limited to current UTD affiliates (use the provided Link to Article).Supplementary material is available on publisher's website. Use the DOI link below.Based on the 2,2′-bipyridine-5,5′-dicarboxylic acid ligand (H₂bpdc), a new metal-organic framework using holmium as the coordinating metal site was synthesized through a solvothermal reaction. The 3D compound {[Ho₂(bPdc)₃(DMF)₂] · 2(DMF)}ₙ (1) was characterized by single crystal X-ray diffraction, FTIR, TGA and PXRD. The coordination between H₂bpdc, the solvent, and holmium (CN = 7) allows for the construction of a MOF containing potentially free metal sites and uncoordinated N-donor sites. These features make this MOF an attractive holmium carrier for radiotherapeutic applications.Robert A. Welch foundation (Grant No. AT-1153)School of Natural Sciences and Mathematic
Nanocast Carbon Microsphere Flowers from a Lanthanum-Based Template
No full textDue to copyright restrictions and/or publisher's policy full text access from Treasures at UT Dallas is limited to current UTD affiliates (use the provided Link to Article).Supplementary material is available on publisher's website. Use the DOI link below.Hollow carbon microsphere flowers were nanocast from glucose, acrylamide, and acetylene sources. Carbon growth was catalyzed by a lanthanum graft copolymer template using wet acetylene. The resulting spherical shape is beneficial for 3-D porosity, and has a highly graphitic content as indicated by raman spectroscopy (I_{D} :I_{G} = 0.99). The carbon has a high surface area of 1000 m²/g, as well as strong π-π stacking of aromatic carbons.Robert A. Welch Foundation (AT-1153)School of Natural Sciences and MathematicsErik Jonsson School of Engineering and Computer Scienc
Metal Oxide–Carbon Nanocomposites for Energy Storage and Conversion
No full textIncreased energy demand with the exponential growth in population has become one of the major challenges that mankind has to face. To overcome the growing energy demand, there is a significant need to find either a sustainable and renewable energy source or efficient ways to store energy. Therefore, development of novel energy storage devices have attracted a great attention. Among different energy storage devices, batteries are the most convenient and accessible devices that are commercially available for a wide range of consumer devices. However, low power density of batteries greatly limits its use in applications requiring quick burst of energy. Thus, one of the overall goals of this study is to develop novel electrode nanostructures and compositions for the next generation of electrochemical devices that are capable of delivering high energy density, high power density and high capacitance.
In the first part of the dissertation, the preparation of metal oxide-carbon nanocomposites using different methodologies and the evaluation of their performance will be discussed. Currently, RuO2 is considered as the best metal oxide that possesses the highest pseudocapacitive properties.
In the second chapter, the use of RuO2 as the pseudocapacitive metal oxide and carbon nanotubes as the electrical double layer capacitive (EDLC) material will be discussed. Moreover, a novel method was introduced to prepare RuO2 nanoribbons. Since RuO2 is an expensive material, incorporating it with a cheaper alternative, i.e. vanadium oxide (V2O5) will be discussed in the third chapter. To achieve this, RuO2 nanodots were deposited on V2O5 nanorods. The use of V2O5 significantly decreased the material cost. Since this novel method used RuO2 quantum dots in low compositions, harvesting the great electrochemical performance of RuO2 without increasing the material cost was successfully achieved. In the fourth chapter, graphene oxide mediated sodium niobate nanotubes were prepared and used as the supercapacitor electrode material. Recently, the use of high surface area carbon nanomaterials for electrochemical energy storage devices has gained more attention. In the fifth chapter, the incorporation of high surface area wrinkled mesoporous carbon to supercapacitor electrodes will be presented. Different amounts of RuO2 nanoparticles were deposited on to the wrinkled mesoporous carbon and the electrochemical performance of supercapacitors were evaluated.
Another major challenge associated with the increasing population is rapid industrialization. With the development of new industries, more waste are generated and released to the environment. Most of these industrial waste contain organic pollutants and eventually they are collected in free water bodies such as oceans and water streams ultimately resulting in the accumulation of toxic organic components in the biomass.
The second part of the dissertation will be focused on the development of novel TiO2 nanotube/ RuO2 nanoribbons/graphene oxide composites for photocatalytic degradation of organic pollutants. This novel photocatalyst significantly increased the photocatalytic remediation of organic dye due to reduced rate of electron-hole recombination. These results suggest that TiO2 nanotube/ RuO2 nanoribbons/graphene oxide composite is capable of efficiently degrading toxic organic components present in industrial waste
Nanostructured and Nanoporous Materials for Heterogeneous Catalysis
No full textNanostrucutured and nanoporous materials are the materials with at least one dimension and a pore size in nanoscale, respectively. The nanomaterials have been intensively studied for various applications ranging from energy storage to catalysis due to their unique physical and chemical properties. Nanoporous materials also plays a key role in a broad range of applications where high surface area and specific pore structures are important. Heterogeneous catalysis has been developed for over 100 years with numerous applications in the petroleum and chemical industries, where zeolites and porous materials are widely used. The development of novel nanostructured and nanoporous materials with specific properties and morphologies is of great interest for application in heterogeneous catalysis. In this work, various types of nanostructured and nanoporous materials were synthesized and characterized. Some of these materials were employed as heterogeneous catalysts for several different reactions
Transition from a 1D Coordination Polymer to a Mixed-Linker Layered MOF
No full textDue to copyright restrictions full text access from Treasures at UT Dallas is restricted to current UTD affiliates (use the provided Link to Article).A novel copper(II) metal-organic framework (MOF) has been synthesized by modifying the reaction conditions of a 1D coordination polymer. The 1D polymer is built by the coordination between copper and 2,2′-(1H-imidazole-4,5-diyl)di-1,4,5,6-tetrahydropyrimidine (H-L1). The geometry of H-L1 precludes its ability to form extended 3D framework structures. By adding 1,4-benzenedicarboxylic acid (H 2 BDC), a well-studied linker in MOF synthesis, we achieved the transition from a 1D polymer chain into porous 2D layered structures. Hydrogen bonding between L1 and BDC directs the parallel stacking of these layers, resulting in a 3D structure with one-dimensional channels accessible by two different pore windows. The preferred growth orientation of the crystal produces prolonged channels and a disparity in pore size distribution. This in turn results in slow diffusion processes in the material. Furthermore, an isoreticular MOF was prepared by substituting the BDC linker by 2,6-naphthalenedicarboxylic acid (H₂NDC). © 2019 American Chemical Society.Robert A. Welch foundation (Grant No. AT-1153).School of Natural Sciences and Mathematic
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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