Titanate nanotube thin films with enhanced thermal stability and high-transparency prepared from additive-free sols

Energy Technology Data Exchange (ETDEWEB)

Koroesi, Laszlo, E-mail: korosi@enviroinvest.hu [Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Sciences, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary); Department of Biotechnology, Nanophage Therapy Center, Enviroinvest Corporation, Kertvaros utca 2, H-7632 Pecs (Hungary); Papp, Szilvia [Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Sciences, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary); Department of Biotechnology, Nanophage Therapy Center, Enviroinvest Corporation, Kertvaros utca 2, H-7632 Pecs (Hungary); Hornok, Viktoria [Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Sciences, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary); Oszko, Albert [Department of Physical Chemistry and Materials Science, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary); Petrik, Peter; Patko, Daniel; Horvath, Robert [Institute for Technical Physics and Materials Science MFA, Research Center for Natural Sciences, Konkoly-Thege ut 29-33, H-1121 Budapest (Hungary); Dekany, Imre [Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Sciences, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary)

2012-08-15

Titanate nanotubes were synthesized from TiO{sub 2} in alkaline medium by a conventional hydrothermal method (150 Degree-Sign C, 4.7 bar). To obtain hydrogen titanates, the as-prepared sodium titanates were treated with either HCl or H{sub 3}PO{sub 4} aqueous solutions. A simple synthesis procedure was devised for stable titanate nanotube sols without using any additives. These highly stable ethanolic sols can readily be used to prepare transparent titanate nanotube thin films of high quality. The resulting samples were studied by X-ray diffraction, N{sub 2}-sorption measurements, Raman spectroscopy, transmission and scanning electron microscopy, X-ray photoelectron spectroscopy and spectroscopic ellipsometry. The comparative results of using two kinds of acids shed light on the superior thermal stability of the H{sub 3}PO{sub 4}-treated titanate nanotubes (P-TNTs). X-ray photoelectron spectroscopy revealed that P-TNTs contains P in the near-surface region and the thermal stability was enhanced even at a low ({approx}0.5 at%) concentration of P. After calcination at 500 Degree-Sign C, the specific surface areas of the HCl- and H{sub 3}PO{sub 4}-treated samples were 153 and 244 m{sup 2} g{sup -1}, respectively. The effects of H{sub 3}PO{sub 4} treatment on the structure, morphology and porosity of titanate nanotubes are discussed. - Graphical Abstract: TEM picture (left) shows P-TNTs with diameters about 5-6 nm. Inset shows a stable titanate nanotube sol illuminated by a 532 nm laser beam. Due to the presence of the nanoparticles the way of the light is visible in the sol. Cross sectional SEM picture (right) as well as ellipsometry revealed the formation of optical quality P-TNT films with thicknesses below 50 nm. Highlights: Black-Right-Pointing-Pointer H{sub 3}PO{sub 4} treatment led to TNTs with high surface area even after calcination at 500 Degree-Sign C. Black-Right-Pointing-Pointer H{sub 3}PO{sub 4}-treated TNTs preserved their nanotube morphology up to 500

Spectroscopic investigation on the interaction of titanate nanotubes with bovine serum albumin

International Nuclear Information System (INIS)

Zhao, L.Z.; Zhao, Y.S.; Teng, H.H.; Shi, S.Y.; Ren, B.X.

2014-01-01

In order to understand the transport mechanism and evaluate the biological safety of titanate nanotubes, the interactions of titanate nanotubes (TNTs) with bovine serum albumin (BSA) were investigated by applying spectroscopic methods under simulated physiological conditions. After taking into account the inner filter effect, the fluorescence intensity of BSA was found to be significantly enhanced by the presence of TNTs, indicating that the microenvironment of tryptophan and tyrosine residues in BSA became more hydrophobic. In addition, the absorption spectra of BSA showed a hyperchromic effect around 280 nm as the concentration of TNTs increased, suggesting that TNTs changed the microenvironment of the tryptophan and tyrosine residues. This is consistent with the results from fluorescence spectroscopy studies. However, circular dichroism spectroscopy revealed that no significant conformational change in BSA occurred during the interaction. We believe that Trp-213 was buried more compactly in the internal hydrophobic region, and hydrophobicity increased around Trp-134 with increasing TNTs concentration. From a spectroscopic point of view, this work elucidates the interaction mechanism of titanate nanotubes with BSA, and the methods used in this paper can also be applied to explore the molecular mechanism underlying toxicity of other nanomaterials. (authors)

Hydrothermal transformation of titanate nanotubes into single-crystalline TiO2 nanomaterials with controlled phase composition and morphology

International Nuclear Information System (INIS)

Xu, Yuanmei; Fang, Xiaoming; Xiong, Jian; Zhang, Zhengguo

2010-01-01

Single-crystalline TiO 2 nanomaterials were synthesized by hydrothermally treating suspensions of H-titanate nanotubes and characterized by XRD, TEM, and HRTEM. The effects of the pH values of the suspensions and the hydrothermal temperatures on the phase composition and morphology of the obtained TiO 2 nanomaterials were systematically investigated. The H-titanate nanotubes were predominately transformed into anatase nanoparticle with rhombic shape when the pH value was greater than or equal to 1.0, whereas primarily turned into rutile nanorod with two pyramidal ends at the pH value less than or equal to 0.5. We propose a possible mechanism for hydrothermal transformation of H-titanate nanotubes into single-crystalline TiO 2 nanomaterials. While the H-titanate nanotubes transform into tiny anatase nanocrystallites of ca. 3 nm in size, the formed nanocrystallites as an intermediate grow into the TiO 2 nanomaterials with controlled phase composition and morphology. This growth process involves the steps of protonation, oriented attachment, and Ostwald ripening.

Formation of layer-by-layer assembled titanate nanotubes filled coating on flexible polyurethane foam with improved flame retardant and smoke suppression properties.

Science.gov (United States)

Pan, Haifeng; Wang, Wei; Pan, Ying; Song, Lei; Hu, Yuan; Liew, Kim Meow

2015-01-14

A fire blocking coating made from chitosan, titanate nanotubes and alginate was deposited on a flexible polyurethane (FPU) foam surface by a layer-by-layer assembly technique in an effort to reduce its flammability. First, titanate nanotubes were prepared by a hydrothermal method. And then the coating growth was carried out by alternately submerging FPU foams into chitosan solution, titanate nanotubes suspension and alginate solution. The mass gain of coating on the surface of FPU foams showed dependency on the concentration of titanate nanotubes suspension and the trilayers's number. Scanning electron microscopy indicated that titanate nanotubes were distributed well on the entire surface of FPU foam and showed a randomly oriented and entangled network structure. The cone calorimeter result indicated that the coated FPU foams showed reduction in the peak heat release rate (peak HRR), peak smoke production rate (peak SPR), total smoke release (TSR) and peak carbon monoxide (CO) production compared with those of the control FPU foam. Especially for the FPU foam with only 5.65 wt % mass gain, great reduction in peak HRR (70.2%), peak SPR (62.8%), TSR (40.9%) and peak CO production (63.5%) could be observed. Such a significant improvement in flame retardancy and the smoke suppression property for FPU foam could be attributed to the protective effect of titanate nanotubes network structure formed, including insulating barrier effect and adsorption effect.

Halloysite nanotubes grafted hyperbranched (co)polymers via surface-initiated self-condensing vinyl (co)polymerization

International Nuclear Information System (INIS)

Mu Bin; Zhao Mingfei; Liu Peng

2008-01-01

Halloysite nanotubes (HNTs) grafted hyperbranched polymers were prepared by the self-condensing vinyl polymerization (SCVP) of 2-((bromoacetyl)oxy)ethyl acrylate (BAEA) and the self-condensing vinyl copolymerization of n-butyl acrylate (BA) and BAEA with BAEA as inimer (AB*) respectively, from the surfaces of the 2-bromoisobutyric acid modified halloysite nanotubes (HNTs-Br) via atom transfer radical polymerization (ATRP) technique. The halloysite nanotubes grafted hyperbranched polymer (HNTs-HP) and the halloysite nanotubes grafted hyperbranched copolymer (HNTs-HCP) were characterized by elemental analysis (EA), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscope (TEM). The grafted hyperbranched polymers were characterized with Nuclear magnetic resonance (NMR) and the molecular ratio between the inimer AB* and BA in the grafted hyperbranched copolymers was found to be 3:2, calculated from the TGA and EA results

Halloysite nanotubes grafted hyperbranched (co)polymers via surface-initiated self-condensing vinyl (co)polymerization

Energy Technology Data Exchange (ETDEWEB)

Mu Bin; Zhao Mingfei; Liu Peng [Lanzhou University, State Key Laboratory of Applied Organic Chemistry and Institute of Polymer Science and Engineering, College of Chemistry and Chemical Engineering (China)], E-mail: pliu@lzu.edu.cn

2008-05-15

Halloysite nanotubes (HNTs) grafted hyperbranched polymers were prepared by the self-condensing vinyl polymerization (SCVP) of 2-((bromoacetyl)oxy)ethyl acrylate (BAEA) and the self-condensing vinyl copolymerization of n-butyl acrylate (BA) and BAEA with BAEA as inimer (AB*) respectively, from the surfaces of the 2-bromoisobutyric acid modified halloysite nanotubes (HNTs-Br) via atom transfer radical polymerization (ATRP) technique. The halloysite nanotubes grafted hyperbranched polymer (HNTs-HP) and the halloysite nanotubes grafted hyperbranched copolymer (HNTs-HCP) were characterized by elemental analysis (EA), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscope (TEM). The grafted hyperbranched polymers were characterized with Nuclear magnetic resonance (NMR) and the molecular ratio between the inimer AB* and BA in the grafted hyperbranched copolymers was found to be 3:2, calculated from the TGA and EA results.

Nanocomposites of polypropylene/titanate nanotubes: morphology, nucleation effects of nanoparticles and properties

Czech Academy of Sciences Publication Activity Database

Mikešová, Jana; Šlouf, Miroslav; Gohs, U.; Popelková, Daniela; Vacková, Taťana; Vu, Ngoc Húng; Kratochvíl, Jaroslav; Zhigunov, Alexander

2014-01-01

Roč. 71, č. 4 (2014), s. 795-818 ISSN 0170-0839 R&D Projects: GA ČR GAP205/10/0348 Institutional support: RVO:61389013 Keywords : titanate nanotubes * polypropylene nanocomposites * nucleation effect Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.438, year: 2014

Self-grafting carbon nanotubes on polymers for stretchable electronics

Science.gov (United States)

Morales, Piero; Moyanova, Slavianka; Pavone, Luigi; Fazi, Laura; Mirabile Gattia, Daniele; Rapone, Bruno; Gaglione, Anderson; Senesi, Roberto

2018-06-01

Elementary bidimensional circuitry made of single-wall carbon-nanotube-based conductors, self-grafted on different polymer films, is accomplished in an attempt to develop a simple technology for flexible and stretchable electronic devices. Unlike in other studies of polymer-carbon nanotube composites, no chemical functionalization of single-wall carbon nanotubes is necessary for stable grafting onto several polymeric surfaces, suggesting viable and cheap fabrication technologies for stretchable microdevices. Electrical characterization of both unstretched and strongly stretched conductors is provided, while an insight on the mechanisms of strong adhesion to the polymer is obtained by scanning electron microscopy of the surface composite. As a first example of technological application, the electrical functionality of a carbon-nanotube-based 6-sensor (electrode) grid was demonstrated by recording of subdural electrocorticograms in freely moving rats over approximately three months. The results are very promising and may serve as a basis for future work targeting clinical applications.

The effect of different atmospheres on structural changes of titanate nanotubes during heating

Czech Academy of Sciences Publication Activity Database

Václavů, T.; Rudajevová, A.; Václavů, M.; Daniš, S.; Popelková, Daniela; Kužel, R.

2017-01-01

Roč. 128, č. 2 (2017), s. 779-785 ISSN 1388-6150 Institutional support: RVO:61389013 Keywords : titanate nanotubes * X-ray diffraction * thermal analysis Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 1.953, year: 2016

Efficient removal of Co(II) from aqueous solution by titanate sodium nanotubes

Institute of Scientific and Technical Information of China (English)

Dong-Mei Li; Ning Liu; Fei-Ze Li; Jia-Li Liao; Ji-Jun Yang; Bing Li; Yun-Ming Chen; Yuan-You Yang; Jin-Song Zhang; Jun Tang

2016-01-01

In this paper, a novel material for Co(II) adsorption, titanate sodium nanotubes (Na2Ti2O5-NTs) were synthesized and characterized, and then they were used to remove Co(II) from aqueous solution and compared with titanic acid nanotubes (H2Ti2O5-NTs) and potassium hexatitanate whiskers (K2Ti6O13). The results showed that the adsorption of Co(II) on the materials was dependent on pH values and was a spontaneous, endothermic process. Specifically, Na2Ti2O5-NTs exhibited much more efficient ability to adsorb Co(II) from aqueous solution, with the maximum adsorption capacity of 85.25 mg/g. Furthermore, Na2Ti2O5-NTs could selectively adsorb Co(II) from aque-ous solution containing coexisting ions (Na+, K+, Mg2+, and Ca2+). The results suggested that Na2Ti2O5-NTs were potential effective adsorbents for removal of Co(II) or cobalt-60 from wastewater.

Rapid Formation of 1D Titanate Nanotubes Using Alkaline Hydrothermal Treatment and Its Photocatalytic Performance

Directory of Open Access Journals (Sweden)

Chin Wei Lai

2015-01-01

Full Text Available One-dimensional (1D titanate nanotubes (TNT were successfully synthesized using alkaline hydrothermal treatment of commercial TiO2 nanopowders in a Teflon lined stainless steel autoclave at 150°C. The minimum time required for the formation of the titanate nanotubes was 9 h significantly. After the hydrothermal processing, the layered titanate was washed with acid and water in order to control the amount of Na+ ions remaining in the sample solutions. In this study, the effect of different reaction durations in a range of 3 h to 24 h on the formation of nanotubes was carried out. As the reaction duration is extended, the changes in structure from particle to tubular shapes of alkaline treated TiO2 were obtained via scanning electron microscope (SEM. Also, the significant impact on the phase transformation and crystal structure of TNT was characterized through XRD and Raman analysis. Indeed, the photocatalytic activity of TNT was investigated through the degradation of methyl orange aqueous solution under the ultraviolet light irradiation. As a result, TNT with reaction duration at 6 h has a better photocatalytic performance than other samples which was correlated to the higher crystallinity of the samples as shown in XRD patterns.

High-temperature hydrogenation of pure and silver-decorated titanate nanotubes to increase their solar absorbance for photocatalytic applications

Energy Technology Data Exchange (ETDEWEB)

Plodinec, Milivoj [Ruđer Bošković Institute, Bijenička 54, HR-1002 Zagreb (Croatia); Gajović, Andreja, E-mail: gajovic@irb.hr [Ruđer Bošković Institute, Bijenička 54, HR-1002 Zagreb (Croatia); Jakša, Gregor; Žagar, Kristina; Čeh, Miran [Institute Jožef Stefan, Jamova 39, 1000 Ljubljana (Slovenia)

2014-04-05

Graphical abstract: The aim of the work is to study how annealing in a reducing atmosphere of titanate nanotubes (TiNT) and Ag decorated titanate nanotubes (TiNT@Ag) influenced on their structure, morphology, phase transitions, UV–ViS-NIR absorbance and photocatalytic activity. An increase of photocatalytic activity after a heat treatment in a reducing atmosphere was observed in the TiNT and TiNT@Ag. We found that the hydrogenated TiNT@Ag samples (TiNT@Ag-HA) had a two-times higher photodegradation impact on the caffeine than the TiNT samples, which is a consequence of the increased absorption of visible light and the synergetic effects between the silver and the TiO{sub 2} nanoparticles that increase the efficiency of the formation of electron–hole pairs and the charge transfer to the surface of the nanoparticles. -- Highlights: • Titanate nanotubes with and without Ag nanoparticles were hydrogenated at 550 °C. • TiO{sub 2} nanostructures obtained by hydrogenation have core–shell structure. • Hydrogenated samples show absorption in the visible spectral region. • Hydrogenated Ag decorated sample show stronger absorption in visible than in UV. • Photocatalytic efficiency is improved by hydrogenation and by Ag nanoparticles. -- Abstract: Titanate nanotubes (TiNTs) and silver-decorated titanate nanotubes (TiNTs@Ag) were synthesized using the hydrothermal method. In the decorated nanotubes the silver particles were obtained by the photoreduction of AgNO{sub 3} under UV light. Pure and Ag-decorated nanotubes were high-temperature heat treated at 550 °C in a hydrogen atmosphere and the “core–shell”-structured TiO{sub 2} nanoparticles were formed. For the structural characterization of all the titanate nanostructures we used conventional and analytical transmission electron microscopy (TEM) techniques, X-ray diffraction (XRD) and Raman spectroscopy. The Ag-decorated titanate nanostructures were additionally studied by X-ray photo

Synthesis and properties of Co-doped titanate nanotubes and their optical sensitization with methylene blue

International Nuclear Information System (INIS)

Ferreira, V.C.; Nunes, M.R.; Silvestre, A.J.; Monteiro, O.C.

2013-01-01

Here we report on a novel chemical route to synthesize homogenous cobalt-doped titanate nanotubes (CoTNT), using an amorphous Co-doped precursor. The influence of the synthesis temperature, autoclave dwell time and metal doping on the structural and microstructural as well as on the optical properties of the synthesized titanate nanotubes is studied and discussed. The optical band gaps of the CoTNT samples are red shifted in comparison with the values determined for the undoped samples, such red shifts bringing the absorption edge of the CoTNT samples into the visible region. CoTNT materials also demonstrate particular high adsorption ability for methylene blue, the amount of the adsorbed dye being higher than the one predictable for a monolayer formation. This suggests the possibility of intercalation of the dye molecule between the TiO 6 layers of the TNT structure. It is also shown that the methylene blue sensitized Co-doped nanostructures are highly stable under UV radiation and present a strong and broad absorption in the visible region. - Highlights: • New hydrothermal chemical route to synthesize cobalt-doped titanate nanotubes. • The Co-doping stabilizes the TNTs morphology in a temperature range of 160–200 °C. • Optical band gaps of CoTNTs are red shifted compared to the TNT samples. • Methylene blue sensitized CoTNTs are highly stable under UV–vis irradiation

Synthesis and properties of Co-doped titanate nanotubes and their optical sensitization with methylene blue

Energy Technology Data Exchange (ETDEWEB)

Ferreira, V.C. [University of Lisbon, Faculty of Sciences, Department of Chemistry and Biochemistry and CQB, Campo Grande, 1749-016 Lisboa (Portugal); Nunes, M.R. [University of Lisbon, Faculty of Sciences, Department of Chemistry and Biochemistry and CCMM, Campo Grande, 1749-016 Lisboa (Portugal); Silvestre, A.J. [Instituto Superior de Engenharia de Lisboa, Department of Physics and ICEMS, R. Conselheiro Emídio Navarro 1, 1959-007 Lisboa (Portugal); Monteiro, O.C., E-mail: ocmonteiro@fc.ul.pt [University of Lisbon, Faculty of Sciences, Department of Chemistry and Biochemistry and CQB, Campo Grande, 1749-016 Lisboa (Portugal)

2013-10-01

Here we report on a novel chemical route to synthesize homogenous cobalt-doped titanate nanotubes (CoTNT), using an amorphous Co-doped precursor. The influence of the synthesis temperature, autoclave dwell time and metal doping on the structural and microstructural as well as on the optical properties of the synthesized titanate nanotubes is studied and discussed. The optical band gaps of the CoTNT samples are red shifted in comparison with the values determined for the undoped samples, such red shifts bringing the absorption edge of the CoTNT samples into the visible region. CoTNT materials also demonstrate particular high adsorption ability for methylene blue, the amount of the adsorbed dye being higher than the one predictable for a monolayer formation. This suggests the possibility of intercalation of the dye molecule between the TiO{sub 6} layers of the TNT structure. It is also shown that the methylene blue sensitized Co-doped nanostructures are highly stable under UV radiation and present a strong and broad absorption in the visible region. - Highlights: • New hydrothermal chemical route to synthesize cobalt-doped titanate nanotubes. • The Co-doping stabilizes the TNTs morphology in a temperature range of 160–200 °C. • Optical band gaps of CoTNTs are red shifted compared to the TNT samples. • Methylene blue sensitized CoTNTs are highly stable under UV–vis irradiation.

Taxane-Grafted Metal-Oxide Nanoparticles as a New Theranostic Tool against Cancer: The Promising Example of Docetaxel-Functionalized Titanate Nanotubes on Prostate Tumors.

Science.gov (United States)

Loiseau, Alexis; Boudon, Julien; Mirjolet, Céline; Créhange, Gilles; Millot, Nadine

2017-08-01

The combination of anticancer drugs and metal oxide nanoparticles is of great interest in cancer nanomedicine. Here, the development of a new nanohybrid, titanate nanotube-docetaxel (TiONts-DTX) is reported, the two parts of which are conjugated by covalent linkages. Unlike most nanoparticles currently being developed for biomedical purposes, TiONts present a needle-shaped morphology. The surface of TiONts is linked with 3-aminopropyl triethoxysilane and with a hetero-bifunctional polymer (polyethylene glycol) to create well-dispersed and biocompatible nanovectors. The prefunctionalized surface of this scaffold has valuable attachments to graft therapeutic agents (DTX in our case) as well as chelating agents (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) to monitor the nanohybrids. To evaluate drug efficacy, in vitro tests have demonstrated that the association between TiONts and DTX shows cytotoxic activity against a hormone-refractory prostate cancer cell line (22Rv1) whereas TiONts without DTX do not. Finally, the first in vivo tests with intratumoral injections show that more than 70% of TiONts nanovectors are retained within the tumor for at least 7 d. Moreover, tumor growth in mice receiving TiONts-DTX is significantly slower than that in mice receiving free DTX. This nanohybrid can thus become a promising new tool in biomedicine to fight against prostate cancer. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Impregnation of sodium titanate onto DMAPAA-grafted fiber under mild reaction conditions and its strontium removal performance from seawater

International Nuclear Information System (INIS)

Katagiri, Mizuki; Kono, Michitaka; Goto, Shun-ichi; Kawai-Noma, Shigeko; Umeno, Daisuke; Saito, Kyoichi; Fujiwara, Kunio; Sugo, Takanobu

2015-01-01

Sodium titanate was impregnated onto a commercially available 6-nylon fiber by means of radiation-induced graft polymerization of dimethyaminopropyl acrylamide (DMAPAA) and subsequent chemical modifications. A peroxo complex of titanium anions was bound onto the DMAPAA-grafted fiber before the bound titanium species was converted to sodium titanate through precipitation with sodium hydroxide. Impregnation percentage of sodium titanate of the fiber was constant at 20% in the range of sodium hydroxide concentration in a mixture of methanol and water at a volume fraction of methanol of 80% of 0.001 to 1 M, whereas the removal percentage of strontium from seawater leveled off at 80% above a sodium hydroxide concentration in water of 0.1 M. Determination of adsorption isotherms in seawater demonstrates that the sodium-titanate-impregnated fiber with an impregnation percentage of 10% exhibited 2.6-fold higher amount of strontium adsorbed in seawater per g of sodium titanate (8.8 mg-Sr/g) than a commercially available granular adsorbent for strontium, SrTreat ® (3.4 mg-Sr/g). (author)

Hydrothermal synthesis of sodium titanate nanotubes; Hydrotermalna synteza nanorurok titanatu sodneho

Energy Technology Data Exchange (ETDEWEB)

Miskoci, M.; Jesenak, K. [Univerzita Komenskeho, Prirodovedecka fakulta, Katedra anorganickej chemie, 84215 Bratislava (Slovakia); Caplovicova, M. [Univerzita Komenskeho, Prirodovedecka fakulta, Katedra loziskovej geologie, 84215 Bratislava (Slovakia)

2013-04-16

From suspension of nanoparticles TiO{sub 2} in concentrated water solution of NaOH were prepared by hydrothermal synthesis sodium titanates particles with different shapes. Influence of synthesis duration under temperature 180 grad C on the change of particles shapes was observed. The result of experiment showed that one day synthesis resulted to obtained product with high content of nanotubes, but the extension of this period led to the transformation of product's shape into stripes. From the results of experiment follows that as a precursor for TiO{sub 2} nanotubes preparation may be used only products of hydrothermal synthesis, which duration of pressure synthesis was not longer than 24 hours. (authors)

A study on the structure and thermal stability of titanate nano-tubes as a function of sodium content

Energy Technology Data Exchange (ETDEWEB)

Morgado, E.; Abreu, M.A.S. de; Pravia, O.R.C. [Petrobras S.A./Cenpes, Research and Development Centre, Cidade Univ., Rio de Janeiro, RJ (Brazil); Marinkovic, B.A.; Jardim, P.M.; Rizzo, F.C. [Pontifical Catholic Univ., Dept. of Materials Science and Metallurgy, Rio de Janeiro (Brazil); Araujo, A.S. [University of Rio Grande do Norte, Dept. of Chemistry, RN (Brazil)

2006-07-01

Titanate Nano-Tubes (TTNT) were synthesized by hydrothermal treatment of TiO{sub 2} anatase in 10 M NaOH at 120 C followed by repeated water washing, with and without ion exchanging by HCl 0.1 M. Samples with different contents of remnant sodium in nano-tubes were characterized, as synthesized and after heat-treatment, by X-ray diffraction, transmission electron microscopy, thermal analysis and N{sub 2} adsorption. It was demonstrated that TTNT consisted of a tri-titanate structure with general formula Na{sub x}H{sub 2}-xTi{sub 3}O{sub 7}.nH{sub 2}O, where 0{<=}x{<=}2 and n{<=}1.2, depending on the degree of proton exchange after washing. As-synthesized nano-tubes retained interlayer water in its multi-walled structure. The removal of sodium reduced the amount of this intercalated water and increased the specific surface area, while thermal stability was reduced. The mechanism through which TTNT dehydrated and converted into their condensed titanates and/or TiO{sub 2} polymorphs after thermal treatment as a function of the sodium content was discussed and a schematic picture of the thermal transformations was proposed. (authors)

A study on the structure and thermal stability of titanate nano-tubes as a function of sodium content

International Nuclear Information System (INIS)

Morgado, E.; Abreu, M.A.S. de; Pravia, O.R.C.; Marinkovic, B.A.; Jardim, P.M.; Rizzo, F.C.; Araujo, A.S.

2006-01-01

Titanate Nano-Tubes (TTNT) were synthesized by hydrothermal treatment of TiO 2 anatase in 10 M NaOH at 120 C followed by repeated water washing, with and without ion exchanging by HCl 0.1 M. Samples with different contents of remnant sodium in nano-tubes were characterized, as synthesized and after heat-treatment, by X-ray diffraction, transmission electron microscopy, thermal analysis and N 2 adsorption. It was demonstrated that TTNT consisted of a tri-titanate structure with general formula Na x H 2 -xTi 3 O 7 .nH 2 O, where 0≤x≤2 and n≤1.2, depending on the degree of proton exchange after washing. As-synthesized nano-tubes retained interlayer water in its multi-walled structure. The removal of sodium reduced the amount of this intercalated water and increased the specific surface area, while thermal stability was reduced. The mechanism through which TTNT dehydrated and converted into their condensed titanates and/or TiO 2 polymorphs after thermal treatment as a function of the sodium content was discussed and a schematic picture of the thermal transformations was proposed. (authors)

Effect of nitrogen doping on the microstructure and visible light photocatalysis of titanate nanotubes by a facile cohydrothermal synthesis via urea treatment

International Nuclear Information System (INIS)

Hu, Cheng-Ching; Hsu, Tzu-Chien; Lu, Shan-Yu

2013-01-01

A facile one-step cohydrothermal synthesis via urea treatment has been adopted to prepare a series of nitrogen-doped titanate nanotubes with highly efficient visible light photocatalysis of rhodamine B, in an effect to identify the effect of nitrogen doping on the photodegradation efficiency. The morphology and microstructure of the thus-prepared N-doped titanates were characterized by nitrogen adsorption/desorption isotherms, transmission electron microscopy, and scanning electron microscopy. With increasing urea loadings, the N-doped titanates change from a porous multi-layer and nanotube-shaped to a dense and aggregated particle-shaped structure, accompanied with reduced specific surface area and pore volume and enhanced pore diameter. Interstitial linkage to titanate via Ti-O-N and Ti-N-O is confirmed by X-ray photoelectron spectroscopy. Factors governing the photocatalytic degradation such as the specific surface area of the catalyst and the degradation pathway are analyzed, a mechanistic illustration on the photodegradation is provided, and a 3-stage degradation mechanism is identified. The synergistic contribution due to the enhanced deethylation and chromophore cleavage on rhodamine B molecules and the reduced band gap on the catalyst TiO 2 by interstitial nitrogen-doping has been accounted for the high photodegradation efficiency of the N-doped titanate nanotubes.

Titanate nanotubes sensitized with silver nanoparticles: Synthesis, characterization and in-situ pollutants photodegradation

Energy Technology Data Exchange (ETDEWEB)

Barrocas, B.; Nunes, C.D. [Centro de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa (Portugal); Carvalho, M.L. [LIBPhys-UNL, Laboratório de Instrumentação, Engenharia Biomédica e Física da Radiação and Departamento de Física da Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Monteiro, O.C., E-mail: ocmonteiro@ciencias.ulisboa.pt [Centro de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa (Portugal)

2016-11-01

Highlights: • Combination of titanate nanotubes with crystalline silver nanoparticles is described. • AgHTNT demonstrated high photocatalytic activity for hydroxyl radical production. • AgHTNT exhibits the best photocatalytic activity for phenol removal. • Recycling does not affect AgHTNT photocatalytic performance. • Silver nanoparticles growth continues during several irradiation cycles. - Abstract: In this work, titanate nanotubes were modified with silver nanoparticles to produce new nanocomposite materials with enhanced photocatalytic activity for phenol removal. The TNTs were produced using a hydrothermal approach and, after being submitted to an Ag{sup +} exchange process, metallic Ag nanoparticles were obtained over the nanotubes surface. The prepared materials were structural, morphological and optical characterized by X-ray powder diffraction, micro X-ray fluorescence, transmission electron microscopy, diffused reflectance spectroscopy and X-ray photoelectron spectroscopy. The characterization results indicate that Ag{sup +} was immobilized not only in the nanotubes external surface but mainly in the TiO{sub 6} interlayers space. The application of this new nanocomposite material on photocatalytic degradation of pollutants was investigated. First, the evaluation of hydroxyl radical formation, using the terephthalic acid as a probe was studied. The photocatalytic activity of the sensitized materials for phenol degradation was afterwards evaluated. The results show that the nanocomposite sample is the best catalyst, achieving 98.0% photodegradation efficiency of a 0.2 mM phenol solution within 20 min under UV–vis radiation. The reusability of the prepared samples as photocatalysts was evaluated in four successive degradation assays, using fresh phenol solutions. The sensitized sample demonstrated excellent catalytic reusability ability, without loss of photochemical stability. The structural and morphological characterization during these

Conjugation of cytochrome c with hydrogen titanate nanotubes: novel conformational state with implications for apoptosis

Energy Technology Data Exchange (ETDEWEB)

Ray, Moumita; Mazumdar, Shyamalava [Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Chatterjee, Sriparna; Das, Tanmay; Bhattacharyya, Somnath; Ayyub, Pushan, E-mail: somnath@tifr.res.in, E-mail: pushan@tifr.res.in, E-mail: shyamal@tifr.res.in [Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India)

2011-10-14

We show that hydrogen titanate (H{sub 2}Ti{sub 3}O{sub 7}) nanotubes form strongly associated reversible nano-bio-conjugates with the vital respiratory protein, cytochrome c. Resonance Raman spectroscopy along with direct electrochemical studies indicate that in this nano-bio-conjugate, cytochrome c exists in an equilibrium of two conformational states with distinctly different formal redox potentials and coordination geometries of the heme center. The nanotube-conjugated cytochrome c also showed enhanced peroxidase activity similar to the membrane-bound protein that is believed to be an apoptosis initiator. This suggests that such a nanotube-cytochrome c conjugate may be a good candidate for cancer therapy applications.

Influence of amine-grafted multi-walled carbon nanotubes on physical and rheological properties of PMMA-based nanocomposites

International Nuclear Information System (INIS)

Kim, Ki-Seok; Park, Soo-Jin

2011-01-01

In this work, poly(methyl methacrylate) (PMMA) was grafted onto amine treated multi-walled carbon nanotubes (NH-MWNTs) and the physical and rheological properties of the NH-MWNTs-g-PMMA nanocomposites were investigated. The graft reaction of NH-MWNTs and the PMMA matrix was confirmed from the change of the N 1S peaks, including those of amine oxygen and amide oxygen, by X-ray photoelectron spectroscopy (XPS). The thermal and mechanical properties of the NH-MWNT-g-PMMA nanocomposites were enhanced by the graft reaction between NH-MWNTs and PMMA matrix. In addition, the viscosity of the nanocomposites was increased with the addition of NH-MWNTs. Storage (G') and loss modulus (G'') were significantly increased by increase in the NH-MWNT content compared to acid-treated MWNTs/PMMA nanocomposites. This increase was attributed to the strong interaction by the grafting reaction between NH-MWNTs and the PMMA matrix. - Graphical abstract: This describes the increase of mechanical properties in NH-MWNTs-g-PMMA hybrid composites with different NH-MWNT contents. Highlights: → Aminized carbon nanotubes are used as reinforcement for poly(methylmethacrylate). → Poly(methylmethacrylate) is grafted on aminized carbon nanotubes by thermal reaction. → Grafting of carbon nanotubes and polymer provide enhanced physical properties. → It was due to the strong interaction between carbon nanotubes and polymer matrix.

[Studies on interaction of acid-treated nanotube titanic acid and amino acids].

Science.gov (United States)

Zhang, Huqin; Chen, Xuemei; Jin, Zhensheng; Liao, Guangxi; Wu, Xiaoming; Du, Jianqiang; Cao, Xiang

2010-06-01

Nanotube titanic acid (NTA) has distinct optical and electrical character, and has photocatalysis character. In accordance with these qualities, NTA was treated with acid so as to enhance its surface activity. Surface structures and surface groups of acid-treated NTA were characterized and analyzed by Transmission Electron Microscope (TEM) and Fourier Transform Infrared Spectrometry (FT-IR). The interaction between acid-treated NTA and amino acids was investigated. Analysis results showed that the lengths of acid-treated NTA became obviously shorter. The diameters of nanotube bundles did not change obviously with acid-treating. Meanwhile, the surface of acid-treated NTA was cross-linked with carboxyl or esterfunction. In addition, acid-treated NTA can catch amino acid residues easily, and then form close combination.

Effect of post treatments on the structure and thermal stability of titanate nanotubes

Energy Technology Data Exchange (ETDEWEB)

Qamar, M [Institute/Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Yoon, C R [Institute/Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Oh, H J [Institute/Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Kim, D H [Department of Advanced Materials Engineering, Hanyang University, Haendang-dong, Seondong-gu, Seoul 133-791 (Korea, Republic of); Jho, J H [Department of Advanced Materials Engineering, Hanyang University, Haendang-dong, Seondong-gu, Seoul 133-791 (Korea, Republic of); Lee, K S [Department of Advanced Materials Engineering, Hanyang University, Haendang-dong, Seondong-gu, Seoul 133-791 (Korea, Republic of); Lee, W J [Korea Electrotechnology Research Institute, 28-1 Sungju-Dong, Changwon, Gyeongnam 641-120 (Korea, Republic of); Lee, H G [Department of Advanced Materials Engineering, Korea Polytechnic University, Jeongwang 1-dong, Siheung-si, Gyeonggi-do 429-793 (Korea, Republic of); Kim, S J [Institute/Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of)

2006-12-28

TiO{sub 2} sol was prepared hydrothermally in an autoclave from aqueous TiOCl{sub 2} solutions as a starting precursor. Titanate nanotubes were obtained when the sol-gel-derived TiO{sub 2} sol was treated chemically with a 10 M NaOH solution and subsequently heated in the autoclave at 150 {sup 0}C for 48 h. The samples were characterized using XRD, TEM, SEM, EDX, Raman spectroscopy, and a BET surface area analyser. The effect of post treatments, such as washing with and without hydrochloric acid and calcination, on the phase structure, shape and morphology, pore structures, and BET surface area of the titanate nanotubes was investigated. When a sample containing 7.08 wt% Na (after washing only with water) was calcined at different temperatures from 300 to 900 {sup 0}C, it showed the formation of a mixture of sodium trititanates and sodium hexatitanates and was found to preserve the tubular morphology at higher temperatures. However, a sample containing 0.06 wt% Na obtained after prolonged washing with hydrochloric acid followed by heat treatment showed the formation of TiO{sub 2} anatase involving TiO{sub 2} (B) as an intermediate at lower temperatures and anatase was further transformed to the rutile phase when the temperature was raised. On the basis of different observations, a general formula Na{sub x}H{sub 2-x}Ti{sub 3}O{sub 7}{center_dot}nH{sub 2}O has been proposed for the trititanate nanotubes.

Titanate nanotubes for reinforcement of a poly(ethylene oxide)/chitosan polymer matrix

Science.gov (United States)

Porras, R.; Bavykin, D. V.; Zekonyte, J.; Walsh, F. C.; Wood, R. J.

2016-05-01

Soft polyethylene oxide (PEO)/chitosan mixtures, reinforced with hard titanate nanotubes (TiNTs) by co-precipitation from aqueous solution, have been used to produce compact coatings by the ‘drop-cast’ method, using water soluble PEO polymer and stable, aqueous colloidal solutions of TiNTs. The effects of the nanotube concentration and their length on the hardness and modulus of the prepared composite have been studied using nanoindentation and nanoscratch techniques. The uniformity of TiNT dispersion within the polymer matrix has been studied using transmission electron microscopy (TEM). A remarkable increase in hardness and reduced Young’s modulus of the composites, compared to pure polymer blends, has been observed at a TiNT concentration of 25 wt %. The short (up to 30 min) ultrasound treatment of aqueous solutions containing polymers and a colloidal TiNT mixture prior to drop casting has resulted in some improvements in both hardness and reduced Young’s modulus of dry composite films, probably due to a better dispersion of ceramic nanotubes within the matrix. However, further (more than 1 h) treatment of the mixture with ultrasound resulted in a deterioration of the mechanical properties of the composite accompanied by a shortening of the nanotubes, as observed by the TEM.

A simple and rapid method to graft hydroxyapatite on carbon nanotubes

International Nuclear Information System (INIS)

Neelgund, Gururaj M.; Olurode, Kehinde; Luo Zhiping; Oki, Aderemi

2011-01-01

Herein a simple and effective approach is introduced to functionalize single walled carbon nanotubes (SWCNTs) by in-situ grafting of hydroxyapatite (HA). The pristine SWCNTs were chemically activated through introduction of carboxylic groups on their surfaces by refluxing in the mixture of H 2 SO 4 and HNO 3 . The resulting carboxylated SWCNTs were further utilized for grafting of HA. The Fourier transform infrared and Raman spectroscopic studies demonstrated the formation of HA and its grafting over SWCNTs. The phase composition of HA and existence Ca 2+ and PO 4 3- ions were studied using X-ray diffraction and energy dispersive X-ray analyses, respectively. The surface morphology of functionalized SWCNTs was analyzed using scanning electron microscopy and transmission electron microscopy. Thermogravimetric analysis confirmed the existence of HA on SWCNTs by exhibiting different thermogram for pure HA and functionalized SWCNTs. Overall, this method produced uniform grafting of low crystalline HA on carboxylated SWCNTs with strong interfacial bonding. - Graphical abstract: A facile approach is demonstrated for effective functionalization of single walled carbon nanotubes (SWCNTs) by in-situ grafting of hydroxyapatite (HA) to improve hydrophilicity and biocompatibility of SWCNTs. This method produced uniform grafting of low crystalline HA on carboxylated SWCNTs with strong interfacial bonding. Research highlights: → This method is facile and effective to graft HA on SWCNTs. → As f-SWCNTs is a promising biomaterial to use without any further processing → This technique is economic, easy to repeat and can be optimized for mass production. → Ratio of Ca to P in f-SWCNTs was 1.65, which is near to ratio present in bone tissue.

A simple and rapid method to graft hydroxyapatite on carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Neelgund, Gururaj M.; Olurode, Kehinde [Department of Chemistry, Prairie View A and M University, Prairie View, TX 77446 (United States); Luo Zhiping [Microscopy and Imaging Center, Materials Science and Engineering, Texas A and M University, College Station TX 77843 (United States); Oki, Aderemi, E-mail: aroki@pvamu.edu [Department of Chemistry, Prairie View A and M University, Prairie View, TX 77446 (United States)

2011-10-10

Herein a simple and effective approach is introduced to functionalize single walled carbon nanotubes (SWCNTs) by in-situ grafting of hydroxyapatite (HA). The pristine SWCNTs were chemically activated through introduction of carboxylic groups on their surfaces by refluxing in the mixture of H{sub 2}SO{sub 4} and HNO{sub 3}. The resulting carboxylated SWCNTs were further utilized for grafting of HA. The Fourier transform infrared and Raman spectroscopic studies demonstrated the formation of HA and its grafting over SWCNTs. The phase composition of HA and existence Ca{sup 2+} and PO{sub 4}{sup 3-} ions were studied using X-ray diffraction and energy dispersive X-ray analyses, respectively. The surface morphology of functionalized SWCNTs was analyzed using scanning electron microscopy and transmission electron microscopy. Thermogravimetric analysis confirmed the existence of HA on SWCNTs by exhibiting different thermogram for pure HA and functionalized SWCNTs. Overall, this method produced uniform grafting of low crystalline HA on carboxylated SWCNTs with strong interfacial bonding. - Graphical abstract: A facile approach is demonstrated for effective functionalization of single walled carbon nanotubes (SWCNTs) by in-situ grafting of hydroxyapatite (HA) to improve hydrophilicity and biocompatibility of SWCNTs. This method produced uniform grafting of low crystalline HA on carboxylated SWCNTs with strong interfacial bonding. Research highlights: {yields} This method is facile and effective to graft HA on SWCNTs. {yields} As f-SWCNTs is a promising biomaterial to use without any further processing {yields} This technique is economic, easy to repeat and can be optimized for mass production. {yields} Ratio of Ca to P in f-SWCNTs was 1.65, which is near to ratio present in bone tissue.

Catalytic wet air oxidation of bisphenol A solution in a batch-recycle trickle-bed reactor over titanate nanotube-based catalysts.

Science.gov (United States)

Kaplan, Renata; Erjavec, Boštjan; Senila, Marin; Pintar, Albin

2014-10-01

Catalytic wet air oxidation (CWAO) is classified as an advanced oxidation process, which proved to be highly efficient for the removal of emerging organic pollutant bisphenol A (BPA) from water. In this study, BPA was successfully removed in a batch-recycle trickle-bed reactor over bare titanate nanotube-based catalysts at very short space time of 0.6 min gCAT g(-1). The as-prepared titanate nanotubes, which underwent heat treatment at 600 °C, showed high activity for the removal of aqueous BPA. Liquid-phase recycling (5- or 10-fold recycle) enabled complete BPA conversion already at 200 °C, together with high conversion of total organic carbon (TOC), i.e., 73 and 98 %, respectively. The catalyst was chemically stable in the given range of operating conditions for 189 h on stream.

Gas transport properties of polybenzimidazole and poly(phenylene oxide) mixed matrix membranes incorporated with PDA-functionalised titanate nanotubes

Czech Academy of Sciences Publication Activity Database

Giel, Verena; Perchacz, Magdalena; Kredatusová, Jana; Pientka, Zbyněk

2017-01-01

Roč. 12, č. 1 (2017), s. 1-15, č. článku 3. ISSN 1931-7573 R&D Projects: GA MŠk(CZ) LO1507 Institutional support: RVO:61389013 Keywords : polybenzimidazole * poly(phenylene oxide) * titanate nanotubes Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science

[Fusion of reconstructed titanic plate, vertebral pedical screws and autogenous granulated cancellous bone graft in posterior occipitocervical region].

Science.gov (United States)

Zhong, Dejun; Song, Yueming

2006-08-01

To explore the technique of fusing the reconstructed titanic plate, the C2 pedical screws, and the autogenous granulated cancellous bone graft in the occipitocervical region. From April 2002 to January 2005, 19 patients aged 31-67 years with occipitocervical instability underwent the occipitocervical fusion using the reconstructed plate, C2 pedical screws, and autogenous granulated cancellous bone graft. Of the patients, 8 had complex occipitocervical deformity, 8 had old atlantoaxial fracture and dislocation, 2 had rheumatoid arthritis and anterior dislocation of the atlantoaxial joint, and 1 had cancer of the deltoid process of the axis. No complication occurred during and after operation. The follow-up for an average of 16 months in 19 patients showed that all the patients achieved solid bony fusion in the occipitocervical region. There was no broken plate, broken screw, looseness of the internal fixation or neurovascular injury. The fixation of the C2 pedical screws with the reconstructed titanic plate is reliable, the insertion is easy, and the autogenous granulated cancellous bone graft has a high fusion rate, thus resulting in a satisfactory effect in the occipitocervical fusion.

Efficient Photocatalytic Degradation of Rhodamine B Dye by Aligned Arrays of Self-Assembled Hydrogen Titanate Nanotubes

Directory of Open Access Journals (Sweden)

Sriparna Chatterjee

2014-01-01

Full Text Available We show that an aligned array of hydrothermally grown, multiwalled hydrogen titanate (H2Ti3O7 nanotubes—anchored to both faces of a metallic Ti foil—acts as an efficient photocatalyst. We studied the degradation of rhodamine B dye in the presence of the nanostructured photocatalyst under UV irradiation, by monitoring the optical absorption of the dye. Rhodamine B was chosen as a representative—and particularly harmful—industrial pollutant dye. The inner and outer diameters of the H2Ti3O7 nanotubes were 5 nm and 10 nm, respectively. The nanotube array catalyst is recyclable and structurally stable. Most importantly, it shows comparable or higher photodecomposition rate constant than those of both H2Ti3O7 nanotube powder and P-25 (Degussa. The enhanced photocatalytic performance may be ascribed to the nanotube array having a superhydrophilic surface with a high accessible surface area.

Gas transport properties of novel mixed matrix membranes made of titanate nanotubes and PBI or PPO

Czech Academy of Sciences Publication Activity Database

Giel, Verena; Galajdová, Barbora; Popelková, Daniela; Kredatusová, Jana; Trchová, Miroslava; Pavlova, Ewa; Beneš, Hynek; Válek, R.; Peter, Jakub

2015-01-01

Roč. 56, č. 12 (2015), s. 3285-3293 ISSN 1944-3994. [International Conference on Membrane and Electromembrane Processes - MELPRO 2014. Prague, 18.05.2014-21.05.2014] R&D Projects: GA ČR(CZ) GPP106/12/P643 Institutional support: RVO:61389013 Keywords : polybenzimidazole * poly(phenylene oxide) * titanate nanotubes Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.272, year: 2015

The mechanochemical stability of hydrogen titanate nanostructures

International Nuclear Information System (INIS)

Plodinec, M.; Friscic, I.; Ivekovic, D.; Tomasic, N.; Su, D.S.; Zhang, J.; Gajovic, A.

2010-01-01

The structural stability of some nanostructured titanates was investigated in terms of their subsequent processing and possible applications. With the aim to investigate their mechanochemical stability, we applied high-energy ball milling and studied the resulting induced phase transitions. Hydrogen titanates with two different morphologies, microcrystals and nanotubes, were taken into consideration. The phase-transition sequence was studied by Raman spectroscopy and X-ray powder diffraction, while the morphology and crystal structure, on the nanoscale, were analyzed by high-resolution transmission electron microscopy. During the mechanochemical treatment of both morphologies, the phase transitions from hydrogen titanate to TiO 2 anatase and subsequently to TiO 2 rutile were observed. In the case of hydrogen trititanate crystals, the phase transition to anatase starts after a longer milling time than in the case of the titanate nanotubes, which is explained by the larger particle size of the crystalline powder. However, the phase transition from anatase to rutile occurred more quickly in the crystalline powder than in the case of the nanotubes.

Hydrothermal synthesis and processing of hydrogen titanate nanotubes for nicotine electrochemical sensing

Science.gov (United States)

Mersal, Gaber A. M.; Mostafa, Nasser Y.; Omar, Abd-Elkader H.

2017-08-01

Hydrogen titanate nanotubes (HTNT) were prepared via acid washing of hydrothermally synthesized sodium titantate nanotube. HTNTs with diameters in the range 7-9 nm and length of several hundred nanometers were annealed at different temperatures and used to modify carbon paste electrode (CPE). Cyclic and square wave voltammetric techniques were used to investigate the behavior of nicotine at HTNT modified carbon paste electrode (HTNTCPE). The nicotine-oxidation reaction over HTNTCPE was irreversible and adsorption process is the rate determining step. HTNTs annealed at 500 °C showed the best response to nicotine. The nicotine concentration was determined at the ideal conditions by square wave voltammetry (SWV). The calibration was linear from 0.1 to 500.0 µmol l-1 with a correlation coefficient of 0.995. The detection limits were found to be 0.005 µmol l-1. The present HTNTCPE was used to the determination of nicotine in two cigarette brands and it showed outstanding performance with respect to detection limit and sensitivity.

Poly(vinyl chloride-grafted multi-walled carbon nanotubes via Friedel-Crafts alkylation

Directory of Open Access Journals (Sweden)

2010-11-01

Full Text Available A novel approach was developed for the surface modification of the multi-walled carbon nanotubes (MWCNTs with high percentage of grafting (PG% by the grafting of polymer via the Friedel-Crafts alkylation. The graft reaction conditions, such as the amount of catalyst added, the reaction temperature, and the reaction time were optimized for the Friedel-Crafts alkylation of the MWCNTs with poly(vinyl chloride (PVC with anhydrous aluminum chloride (AlCl3 as catalyst in chloroform (CHCl3. The Fourier Transform Infrared (FT-IR, Raman, and thermogravimetric (TGA analysis showed that PVC had been successfully grafted onto MWCNTs both at the ends and on the sidewalls by the proposed Friedel-Crafts alkylation. The PVC grafted MWCNTs (PVC-MWCNTs could be dispersed well in organic solvent and the dispersion was more stable.

In situ polymerization and characterization of grafted poly (3,4-ethylenedioxythiophene)/multiwalled carbon nanotubes composite with high electrochemical performances

International Nuclear Information System (INIS)

Bai, Xiaoxia; Hu, Xiujie; Zhou, Shuyun; Yan, Jun; Sun, Chenghua; Chen, Ping; Li, Laifeng

2013-01-01

Graphical abstract: The homogeneously grafted PEDOT/MWCNTs containing numerous whorl fingerprint-like open ends endows with excellent electrochemical performances. Highlights: ► A ternary phase system with the surfactant AOT is utilized to efficiently solve the problem of the aggregation of MWCNTs. ► The homogenously grafted PEDOT/MWCNTs composite is synthesized by in situ chemical polymerization in the ternary phase system. ► The core–shell nanotubes contain many whorl fingerprint-like open ends that are greatly favorable for the transportation of the electrons and ions. ► The energy density of grafted PEDOT/MWCNTs has been enhanced by a factor of four comparing to that of native MWCNTs. ► The grafted PEDOT/MWCNTs composite manifests better cycle durability than both the constituents. - Abstract: The homogenously grafted composite of poly (3,4-ethylenedioxythiophene)/multiwalled carbon nanotubes (PEDOT/MWCNTs) is synthesized by in situ chemical polymerization in a ternary phase system. When carbon nanotubes are dispersed in this system containing sodium bis(2-ethylhexyl) sulfosuccinate (AOT), the surfactant AOT can efficiently hinter the aggregation of MWCNTs by absorbing and arranging regularly on the MWCNT surface. It is greatly advantageous to the stabilization of MWCNTs, which leads to the equally grafted composite. Its morphology was observed by scanning and transmission electron microscopes. Especially, the core–shell nanotubes contain many whorl fingerprint-like open ends that are efficiently favorable for the transportation of the electrons and ions. Such grafted PEDOT/MWCNTs composite nanotubes manifest enhanced electrochemical performances. We investigate the application of PEDOT/MWCNTs as a high-property supercapacitor and test its capacitive performance by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The energy density of grafted composite, 11.3 Wh kg −1 , has been enhanced by a factor

Enhancement of stiffness, strength, ductility and toughness of poly(ethylene oxide) using phenoxy-grafted multiwalled carbon nanotubes

International Nuclear Information System (INIS)

Yang Bingxing; Shi Jiahua; Pramoda, K P; Goh, Suat Hong

2007-01-01

Phenoxy (poly(hydroxyether of bisphenol-A), also known as poly(bisphenol-A-co-epichlorohydrin)) was grafted onto multiwalled carbon nanotubes (MWNTs) by a reactive blending process. Reactions between terminal glycidyl groups of phenoxy and carboxylic acid groups of acidified MWNTs resulted in the grafting of phenoxy chains onto MWNTs. The mechanical properties of composites of poly(ethylene oxide) (PEO) and phenoxy-grafted MWNTs were studied. The miscibility between PEO and phenoxy enabled the good dispersion of nanotubes in the PEO matrix as evidenced by polarized optical microscopy and transmission electron microscopy. The spherulite size of PEO progressively decreased with increasing amount of phenoxy-grafted MWNTs added. At an optimal MWNT content of 1.5 wt%, the addition of phenoxy-grafted MWNTs led to increases of storage modulus, Young's modulus, yield stress, tensile strength, ultimate strain, and toughness of PEO by 113, 228, 166, 442, 1240, and 4080%, respectively. Such simultaneous increases in stiffness, strength, ductility and toughness of a polymer by an additive are rather uncommon

[Treatment of thoracolumbar burst fracture with lateral anterior decompression, internal fixation with Ventrofix and bone graft with titanic mesh].

Science.gov (United States)

Zhang, Shi-min; Zhang, Zhao-jie; Liu, Yu-zhang; Zhang, Lu-tang; Li, Xing

2011-11-01

To discuss the efficacy of lateral anterior decompression, internal fixation with Ventrofix and bone graft with titanic mesh in the treatment of severe thoracolumbar burst fracture. From January 2008 to January 2010, 21 patients with severe thoracolumbar burst fracture were treated with lateral anterior decompression, internal fixation with Ventrofix, bone graft with titanic mesh. There were 15 males and 6 females, ranging in age from 21 to 46 years with an average of 32.2 years. Segment of fracture: 3 cases were in T11, 6 cases in T12, 7 cases in L1, 5 cases in L2. The mean kyphosis angle was 20.1 degrees and loading of fracture was 7.8 scores. Twenty-one cases accompany with incomplete paralysis. Nerves functions were observed according to Frankel grade; correction and maintain of kyphosis angle were observed by X-rays and CT. All the patients were followed up from 12 to 34 months with an average of 18.5 years. Postoperative complication including injury of pleura in 1 case, dynamic ileus in 2 cases, ilioinguinal nerve injury in 1 case, faulty union of wound in 1 case. All the above complications got recovery after symptomatic treatment. The mean kyphosis angle in fusional segment were 4.2 degrees and the rate of correction was 79%. Nerves functions of all patients got improvement and no internal fixation fail, kyphosis angle obviously lost, titanium mesh shifting, loosening and breakage of screw were found at final follow-up. Lateral anterior decompression, bone graft with titanic mesh, internal fixation with Ventrofix is an idea technique for severe thoracolumber burst fracture, but the method can not be used for patient with severity osteoporosis.

Hydroxyapatite grafted carbon nanotubes and graphene nanosheets: Promising bone implant materials

Science.gov (United States)

Oyefusi, Adebola; Olanipekun, Opeyemi; Neelgund, Gururaj M.; Peterson, Deforest; Stone, Julia M.; Williams, Ebonee; Carson, Laura; Regisford, Gloria; Oki, Aderemi

2014-11-01

In the present study, hydroxyapatite (HA) was successfully grafted to carboxylated carbon nanotubes (CNTs) and graphene nanosheets. The HA grafted CNTs and HA-graphene nanosheets were characterized using FT-IR, TGA, SEM and X-ray diffraction. The HA grafted CNTs and graphene nanosheets (CNTs-HA and Gr-HA) were further used to examine the proliferation and differentiation rate of temperature-sensitive human fetal osteoblastic cell line (hFOB 1.19). Total protein assays and western blot analysis of osteocalcin expression were used as indicators of cell proliferation and differentiation. Results indicated that hFOB 1.19 cells proliferate and differentiate well in treatment media containing CNTs-HA and graphene-HA. Both CNTs-HA and graphene-HA could be promising nanomaterials for use as scaffolds in bone tissue engineering.

Systematic studies of covalent functionalization of carbon nanotubes via argon plasma-assisted UV grafting

International Nuclear Information System (INIS)

Yan, Y H; Cui, J; Chan-Park, M B; Wang, X; Wu, Q Y

2007-01-01

Single-walled carbon nanotubes (SWNTs) with 1-vinylimidazole species covalently attached to their sidewalls and end caps have been prepared by ultraviolet (UV) irradiation in 1-vinylimidazole monomer. This process can be greatly assisted by argon (Ar) plasma pretreatment, which generates more defect sites at the tube ends and sidewalls acting as the active sites for the subsequent UV grafting of 1-vinylimidazole molecules. The effects of total deposited energy of Ar plasma treatment, either by change of treatment time or discharge power, on the functionalization degree and structural morphology of the resulting nanotubes are systematically studied. By control of the Ar plasma treatment time within 5 min at the discharge power of 200 W, no visible chopping of the functionalized SWNTs was observed. Under this advised optimum processing condition, the functionalization degree, estimated by x-ray photoelectron spectroscopy (XPS) measurement, is as high as around 26 wt% 1-vinylimidazole molecules grafted onto the nanotubes. This method may be extended to other reactive vinyl monomers and offers another diverse way of covalent functionalization of SWNTs

Hydroxyapatite grafted carbon nanotubes and graphene nanosheets: promising bone implant materials.

Science.gov (United States)

Oyefusi, Adebola; Olanipekun, Opeyemi; Neelgund, Gururaj M; Peterson, Deforest; Stone, Julia M; Williams, Ebonee; Carson, Laura; Regisford, Gloria; Oki, Aderemi

2014-11-11

In the present study, hydroxyapatite (HA) was successfully grafted to carboxylated carbon nanotubes (CNTs) and graphene nanosheets. The HA grafted CNTs and HA-graphene nanosheets were characterized using FT-IR, TGA, SEM and X-ray diffraction. The HA grafted CNTs and graphene nanosheets (CNTs-HA and Gr-HA) were further used to examine the proliferation and differentiation rate of temperature-sensitive human fetal osteoblastic cell line (hFOB 1.19). Total protein assays and western blot analysis of osteocalcin expression were used as indicators of cell proliferation and differentiation. Results indicated that hFOB 1.19 cells proliferate and differentiate well in treatment media containing CNTs-HA and graphene-HA. Both CNTs-HA and graphene-HA could be promising nanomaterials for use as scaffolds in bone tissue engineering. Copyright © 2014 Elsevier B.V. All rights reserved.

Visible-light induced photocatalysis of AgCl@Ag/titanate nanotubes/nitrogen-doped reduced graphite oxide composites

Science.gov (United States)

Pan, Hongfei; Zhao, Xiaona; Fu, Zhanming; Tu, Wenmao; Fang, Pengfei; Zhang, Haining

2018-06-01

High recombination rate of photogenerated electron-hole pairs and relatively narrow photoresponsive range of TiO2-based photocatalysts are the remaining challenges for their practical applications. To address such challenges, photocatalysts consisting of AgCl covered Ag nanoparticles (AgCl@Ag), titanate nanotubes (TiNT), and nitrogen-doped reduced graphite oxide (rGON) are fabricated through alkaline hydrothermal process, followed by deposition and in situ surface-oxidation of silver nanoparticles. In the synthesized photocatalysts, the titanate nanotubes have average length of about 100 nm with inner diameters of about 5 nm and the size of the formed silver nanoparticles is in the range of 50-100 nm. The synthesized photocatalyst degrades almost all the model organic pollutant Rhodamine B in 35 min and remains 90% of photocatalytic efficiency after 5 degradation cycles under visible light irradiation. Since the oxidant FeCl3 applied for oxidation of surface Ag to AgCl is difficult to be completely removed due to the high adsorption capacity of TiNT and rGON, the effect of reside Fe atoms on photocatalytic activity is evaluated and the results reveal that the residue Fe atom only affect the initial photodegradation performance. Nevertheless, the results demonstrate that the formed composite catalyst is a promising candidate for antibiosis and remediation in aquatic environmental contamination.

Enhancement of mechanical properties of poly(vinyl chloride with polymethyl methacrylate-grafted halloysite nanotube

Directory of Open Access Journals (Sweden)

2011-07-01

Full Text Available Halloysite nanotubes(HNTs grafted with Polymethyl methacrylate(PMMA were synthesized via radical polymerization. The properties of PMMA-grafted HNTs were characterized by transmission electron microscopy (TEM, fourier transform infrared spectroscopy (FTIR, thermogravimetric analysis (TGA and X-ray photoelectron spectroscopy (XPS. The results showed that PMMA grafted to the surfaces of HNTs successfully. Then, PVC/PMMA-grafted HNTs nanocomposites were prepared by melt compounding. The morphology, mechanical properties and thermal properties of the nanocomposites were investigated. PMMA-grafted HNTs can effectively improve the toughness, strength and modulus of PVC. The glass transition and thermal decomposition temperatures of PVC phase in PVC/PMMA-grafted HNTs nanocomposites are shifted toward slightly higher temperatures. The grafted HNTs were uniformly dispersed in PVC matrix as revealed by TEM photos. The fracture surfaces of the nanocomposites exhibited plastic deformation feature indicating ductile fracture behaviors. The improvement of toughness of PVC by PMMA-grafted HNTs was attributed to the improved interfacial bonding by grafting and the toughening mechanism was explained according to the cavitation mechanism.

A lactate electrochemical biosensor with a titanate nanotube as direct electron transfer promoter

International Nuclear Information System (INIS)

Yang Mingli; Wang Jin; Li Huaqing; Wu Nianqiang Nick; Zheng Jianguo

2008-01-01

Hydrogen titanate (H 2 Ti 3 O 7 ) nanotubes (TNTs) have been synthesized by a one-step hydrothermal processing. Lactate oxidase (LOx) enzyme has been immobilized on the three-dimensional porous TNT network to make an electrochemical biosensor for lactate detection. Cyclic voltammetry and amperometry tests reveal that the LOx enzyme, which is supported on TNTs, maintains their substrate-specific catalytic activity. The nanotubes offer the pathway for direct electron transfer between the electrode surface and the active redox centers of LOx, which enables the biosensor to operate at a low working potential and to avoid the influence of the presence of O 2 on the amperometric current response. The biosensor exhibits a sensitivity of 0.24 μA cm -2 mM -1 , a 90% response time of 5 s, and a linear response in the range from 0.5 to 14 mM and the redox center of enzyme obviates the need of redox mediators for electrochemical enzymatic sensors, which is attractive for the development of reagentless biosensors

A lactate electrochemical biosensor with a titanate nanotube as direct electron transfer promoter

Science.gov (United States)

Yang, Mingli; Wang, Jin; Li, Huaqing; Zheng, Jian-Guo; Wu, Nianqiang Nick

2008-02-01

Hydrogen titanate (H2Ti3O7) nanotubes (TNTs) have been synthesized by a one-step hydrothermal processing. Lactate oxidase (LOx) enzyme has been immobilized on the three-dimensional porous TNT network to make an electrochemical biosensor for lactate detection. Cyclic voltammetry and amperometry tests reveal that the LOx enzyme, which is supported on TNTs, maintains their substrate-specific catalytic activity. The nanotubes offer the pathway for direct electron transfer between the electrode surface and the active redox centers of LOx, which enables the biosensor to operate at a low working potential and to avoid the influence of the presence of O2 on the amperometric current response. The biosensor exhibits a sensitivity of 0.24 µA cm-2 mM-1, a 90% response time of 5 s, and a linear response in the range from 0.5 to 14 mM and the redox center of enzyme obviates the need of redox mediators for electrochemical enzymatic sensors, which is attractive for the development of reagentless biosensors.

Study on photocatalysis of TiO2 nanotubes prepared by methanol ...

Indian Academy of Sciences (India)

Titanate nanotubes were synthesized in methanol–water volume ratios of 10:90, 20:80 and 30:70 which still .... atmospheric pressure. .... pore volume of the largest titania nanotubes were observed ... affect phase structure and microstructure of titanate nanotubes .... Left inset in figure 7 is an enlarged picture of a tube wall.

Physicochemical characterisation and investigation of the bonding mechanisms of API-titanate nanotube composites as new drug carrier systems.

Science.gov (United States)

Sipos, Barbara; Pintye-Hódi, Klára; Kónya, Zoltán; Kelemen, András; Regdon, Géza; Sovány, Tamás

2017-02-25

Titanate nanotube (TNT) has recently been explored as a new carrier material for active pharmaceutical ingredients (API). The aim of the present work was to reveal the physicochemical properties of API-TNT composites, focusing on the interactions between the TNTs and the incorporated APIs. Drugs belonging to different Biopharmaceutical Classification System (BCS) classes were loaded into TNTs: diltiazem hydrochloride (BCS I.), diclofenac sodium (BCS II.), atenolol (BCS III.) and hydrochlorothiazide (BCS IV.). Experimental results demonstrated that it is feasible for spiral cross-sectioned titanate nanotubes to carry drugs and maintain their bioactivity. The structural properties of the composites were characterized by a range of analytical techniques, including FT-IR, DSC, TG-MS, etc. The interactions between APIs and TNTs were identified as electrostatic attractions, mainly dominated by hydrogen bonds. Based on the results, it can be stated that the strength of the association depends on the hydrogen donor strength of the API. The drug release of incorporated APIs was evaluated from compressed tablets and compared to that of pure APIs. Differences noticed in the dissolution profiles due to incorporation showed a correlation with the strength of interactions between the APIs and the TNTs observed in the above analytical studies. Copyright © 2016 Elsevier B.V. All rights reserved.

TiO{sub 2}-based nanotubes modified with nickel: synthesis, properties, and improved photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Qamar, M; Ganguli, A K [Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi 110016 (India); Kim, S J, E-mail: sjkim1@sejong.ac.k, E-mail: ashok@chemistry.iitd.ac.i [Department of Nano Science and Technology, Sejong Advanced Institute of Nano Technologies, Sejong University, 98, Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of)

2009-11-11

Titanate nanotubes containing 2.5 wt% Ni were synthesized from TiO{sub 2} sol using alkali hydrothermal treatment followed by a simple ion-exchange process. The changes in phase, shape and morphology, surface area, and photocatalytic activity of these nanotubes have been explored as a function of calcination temperature. The samples were characterized using standard techniques, including x-ray diffraction, transmission electron microscopy, scanning electron microscopy, inductively coupled plasma spectrometry, energy dispersive x-ray spectroscopy, and Brauner-Emmett-Teller surface area analysis. The study revealed that the titanate phase containing Ni ions can be converted to the anatase phase after certain heat treatments but, at the same time, the tubular morphology was partially lost. Investigation of photocatalytic properties demonstrated that the as-prepared Ni-titanate nanotubes were photocatalytically inactive, but when heated at temperatures below 500 {sup 0}C their activity was significantly enhanced with the change in phase. The calcined nanotube samples carrying nickel ion showed better photocatalytic activity than calcined nanotube samples containing protons. The hydrogen adsorption capacity of these titanates has also been measured, and it was found that Ni-titanate nanotubes can adsorb more hydrogen than its counterpart Na-titanate.

Facile graft polystyrene onto multi-walled carbon nanotubes via in situ thermo-induced radical polymerization

International Nuclear Information System (INIS)

Liu Peng

2009-01-01

A facile procedure was developed for the grafting of polystyrene onto the surfaces of multi-walled carbon nanotubes (MWNTs) via the in situ thermo-induced bulk radical polymerization of styrene at the different polymerizing temperatures, in the presence of MWNTs without any initiator added. The grafting products were validated by the dispersibility, TEM, TGA, FT-IR, and Raman analysis. The TGA results also showed the lower polymerizing temperature was propitious to the free radical addition reactions.

Synthesis and Properties of Carbon Nanotube-Grafted Silica Nanoarchitecture-Reinforced Poly(Lactic Acid

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Yao-Wen Hsu

2017-07-01

Full Text Available A novel nanoarchitecture-reinforced poly(lactic acid (PLA nanocomposite was prepared using multi-walled carbon nanotube (MWCNT-grafted silica nanohybrids as reinforcements. MWCNT-grafted silica nanohybrids were synthesized by the generation of silica nanoparticles on the MWCNT surface through the sol-gel technique. This synthetic method involves organo-modified MWCNTs that are dispersed in tetrahydrofuran, which incorporates tetraethoxysilane that undergoes an ultrasonic sol-gel process. Gelation yielded highly dispersed silica on the organo-modified MWCNTs. The structure and properties of the nanohybrids were established using 29Si nuclear magnetic resonance, Raman spectroscopy, wide-angle X-ray diffraction, thermogravimetric analysis, and transmission electron microscopy. The resulting MWCNT nanoarchitectures were covalently assembled into silica nanoparticles, which exhibited specific and controllable morphologies and were used to reinforce biodegradable PLA. The tensile strength and the heat deflection temperature (HDT of the PLA/MWCNT-grafted silica nanocomposites increased when the MWCNT-grafted silica was applied to the PLA matrix; by contrast, the surface resistivity of the PLA/MWCNT-grafted silica nanocomposites appeared to decline as the amount of MWCNT-grafted silica in the PLA matrix increased. Overall, the reinforcement of PLA using MWCNT-grafted silica nanoarchitectures was efficient and improved its mechanical properties, heat resistance, and electrical resistivity.

Structural dependence of the multi-functionalized carbon nanotubes to the substituents on the grafted diazo compounds

Science.gov (United States)

Amiri, Rahebeh; Rasouli, Sousan; Ghasemi, Alireza; Eghbali, Babak; Mohammadi, Soutodeh

2014-05-01

Systematic studies on the covalent functionalization of multi-walled carbon nanotubes were performed by a series of azo molecules with different substituents. For this investigation, 4-substituted diazonium reagents have been used in the reaction with the functionalized multi-walled carbon nanotubes. We analyzed the effect of the substituted groups on the diazo component affinity in the grafting. Also, the structural differences of the final products were evaluated by visual dispersion test, UV-Vis absorption. Fourier transforms infrared, Raman, and several complementary techniques (scanning electron microscopy, thermal gravimetric analysis, and colorimetry test). Nuclear magnetic resonance spectroscopy has been used to confirm the allylic protons attached to the surface of carbon nanotubes after functionalization.

Lithium storage study on MoO3-grafted TiO2 nanotube arrays

Directory of Open Access Journals (Sweden)

Tauseef Anwar

2016-03-01

Full Text Available Abstract Titanium dioxide nanotube arrays (TNAs were fabricated via anodic ionization. Porous MoO3 was grafted on TNAs with the help of hydrothermal method. Scanning electron microscopy and X-ray powder diffraction was utilized for the confirmation of one dimensional morphology and phase identification. The porous MoO3 nanoflake-grafted TNAs (MoO3/TNAs electrode was used as anode material in lithium ion battery (LIB and it was found that the areal specific capacity of MoO3/TNAs (~797 µAh cm−2 was three times higher than those of anatase TNAs (~287 µAh cm−2 and porous MoO3 (~234 µAh cm−2 at 50 µA cm−2.

Surface modification of commercial seawater reverse osmosis membranes by grafting of hydrophilic monomer blended with carboxylated multiwalled carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Vatanpour, Vahid, E-mail: vahidvatanpour@khu.ac.ir; Zoqi, Naser

2017-02-28

Highlights: • A commercial PA RO membrane was modified by grafting of hydrophilic acrylic acid. • COOH-MWCNTs were mixed in grafting layer to increase permeability and antifouling. • However, more increase of CNTs caused in reduction of flux of the membranes. • Effect of acrylic acid amount, contact time and curing time was optimized. - Abstract: In this study, modification of commercial seawater reverse osmosis membranes was carried out with simultaneous use of surface grafting and nanoparticle incorporation. Membrane grafting with a hydrophilic acrylic acid monomer and thermal initiator was used to increase membrane surface hydrophilicity. The used nanomaterial was carboxylated multiwalled carbon nanotubes (MWCNTs), which were dispersed in the grafting solution and deposited on membrane surface to reduce fouling by creating polymer brushes and hydrodynamic resistance. Effectiveness of the grafting process (formation of graft layer on membrane surface) was proved by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses. Increase of membrane surface hydrophilicity was approved with contact angle test. First, the grafting was performed on the membrane surfaces with different monomer concentrations, various contact times and several membrane curing times (three variables for optimization). The modified membranes were tested by a cross-flow setup using saline solution for permeability and rejection tests, and bovine serum albumin (BSA) solution for fouling test. The results showed that the modified membranes with 0.75 M of monomer, 3 min contact time and 80 min curing time in an oven at 50 °C presented the highest flux and lowest rejection decline related to the commercial reverse osmosis membrane. In the next step, the optimum grafting condition was selected and the nanotubes with different weight percentages were dispersed in the acrylic acid monomer solution. The membrane containing 0.25 wt% COOH-MWCNTs showed the

Surface modification of commercial seawater reverse osmosis membranes by grafting of hydrophilic monomer blended with carboxylated multiwalled carbon nanotubes

International Nuclear Information System (INIS)

Vatanpour, Vahid; Zoqi, Naser

2017-01-01

Highlights: • A commercial PA RO membrane was modified by grafting of hydrophilic acrylic acid. • COOH-MWCNTs were mixed in grafting layer to increase permeability and antifouling. • However, more increase of CNTs caused in reduction of flux of the membranes. • Effect of acrylic acid amount, contact time and curing time was optimized. - Abstract: In this study, modification of commercial seawater reverse osmosis membranes was carried out with simultaneous use of surface grafting and nanoparticle incorporation. Membrane grafting with a hydrophilic acrylic acid monomer and thermal initiator was used to increase membrane surface hydrophilicity. The used nanomaterial was carboxylated multiwalled carbon nanotubes (MWCNTs), which were dispersed in the grafting solution and deposited on membrane surface to reduce fouling by creating polymer brushes and hydrodynamic resistance. Effectiveness of the grafting process (formation of graft layer on membrane surface) was proved by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses. Increase of membrane surface hydrophilicity was approved with contact angle test. First, the grafting was performed on the membrane surfaces with different monomer concentrations, various contact times and several membrane curing times (three variables for optimization). The modified membranes were tested by a cross-flow setup using saline solution for permeability and rejection tests, and bovine serum albumin (BSA) solution for fouling test. The results showed that the modified membranes with 0.75 M of monomer, 3 min contact time and 80 min curing time in an oven at 50 °C presented the highest flux and lowest rejection decline related to the commercial reverse osmosis membrane. In the next step, the optimum grafting condition was selected and the nanotubes with different weight percentages were dispersed in the acrylic acid monomer solution. The membrane containing 0.25 wt% COOH-MWCNTs showed the

Influence of the electronic distribution of polymers in the spatial conformation of polymer grafted carbon nanotube composites

Energy Technology Data Exchange (ETDEWEB)

Garate, H. [Universidad de Buenos Aires, FCEyN, Depto. de Fisica IFIBA-CONICET LPyMC, Pabellon I, Buenos Aires 1428 (Argentina); Universidad de Buenos Aires, FCEyN, Depto. de Quimica Organica, (CIHIDECAR-CONICET) Buenos Aires 1428 (Argentina); De Falco, A. [Universidad de Buenos Aires, FCEyN, Depto. de Fisica IFIBA-CONICET LPyMC, Pabellon I, Buenos Aires 1428 (Argentina); Moreno, M.S. [Centro Atomico Bariloche, 8400 S.C. de Bariloche (Argentina); Fascio, M.L. [Universidad de Buenos Aires, FCEyN, Depto. de Quimica Organica, (CIHIDECAR-CONICET) Buenos Aires 1428 (Argentina); Goyanes, S. [Universidad de Buenos Aires, FCEyN, Depto. de Fisica IFIBA-CONICET LPyMC, Pabellon I, Buenos Aires 1428 (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina); D' Accorso, N.B., E-mail: norma@qo.fcen.uba.ar [Universidad de Buenos Aires, FCEyN, Depto. de Quimica Organica, (CIHIDECAR-CONICET) Buenos Aires 1428 (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina)

2012-08-15

In this work we report the covalent functionalization of multiwalled carbon nanotubes (MWCNTs) with polyacrylonitrile (PAN) and polyvinylpyridine (PVP) by the graft from method. Differences in the electronic distribution of both polymers resulted in different interaction between polymers and the nanotubes. It was found that PVP chains wrapped the nanotubes while nanotubes functionalized with PAN presented PAN chains forming amorphous entanglements on the nanoscale linked to the MWCNTs. Differences in the conformation between both polymers and the MWCNTs can be attributed to interactions between the aromatic groups in PVP and the MWCNTs through {pi}-{pi} stacking. The absence of aromatic groups in the case of the PAN chains favours the interaction between them. The functionalization efficiency was characterized using Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and UV-vis spectroscopy, while morphological changes were characterized by high resolution transmission electron microscopy.

Enhanced Efficiency of Polymer Light-Emitting Diodes by Dispersing Dehydrated Nanotube Titanic Acid in the Hole-buffer Layer

Energy Technology Data Exchange (ETDEWEB)

Qian, L., E-mail: qian_lei@126.com; Xu, Z.; Teng, F.; Duan, X.-X. [Beijing Jiaotong University, Institute of Optoelectronic Technology (China); Jin, Z.-S.; Du, Z.-L. [Henan University, Key Laboratory on special functional materials (China); Li, F.-S.; Zheng, M.-J. [State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Peking University, Department of Physics (China); Wang, Y.-S. [Beijing Jiaotong University, Institute of Optoelectronic Technology (China)

2007-06-15

Efficiency of polymer light-emitting diodes (PLEDs) with poly(2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene) (MEH-PPV) as an emitting layer was improved if a dehydrated nanotubed titanic acid (DNTA) doped hole-buffer layer polyethylene dioxythiophene (PEDOT) was used. Photoluminescence (PL) and Raman spectra indicated a stronger interaction between DNTA and sulfur atom in thiophene of PEDOT, which suppresses the chemical interaction between vinylene of MEH-PPV and thiophene of PEDOT. The interaction decreases the defect states in an interface region to result in enhancement in device efficiency, even though the hole transporting ability of PEDOT was decreased.

Enhanced Efficiency of Polymer Light-Emitting Diodes by Dispersing Dehydrated Nanotube Titanic Acid in the Hole-buffer Layer

Science.gov (United States)

Qian, L.; Xu, Z.; Teng, F.; Duan, X.-X.; Jin, Z.-S.; Du, Z.-L.; Li, F.-S.; Zheng, M.-J.; Wang, Y.-S.

2007-06-01

Efficiency of polymer light-emitting diodes (PLEDs) with poly(2-methoxy-5-(2-ethyl hexyloxy)- p-phenylene vinylene) (MEH-PPV) as an emitting layer was improved if a dehydrated nanotubed titanic acid (DNTA) doped hole-buffer layer polyethylene dioxythiophene (PEDOT) was used. Photoluminescence (PL) and Raman spectra indicated a stronger interaction between DNTA and sulfur atom in thiophene of PEDOT, which suppresses the chemical interaction between vinylene of MEH-PPV and thiophene of PEDOT. The interaction decreases the defect states in an interface region to result in enhancement in device efficiency, even though the hole transporting ability of PEDOT was decreased.

Polyethyleneimine grafted short halloysite nanotubes for gene delivery.

Science.gov (United States)

Long, Zheru; Zhang, Jun; Shen, Yan; Zhou, Changren; Liu, Mingxian

2017-12-01

Inorganic nanoparticles have attracted much attentions in gene delivery because of their desirable characteristics including low toxicity, well-controlled characteristics, high gene delivery efficiency, and multi-functionalities. Here, natural occurred halloysite nanotubes (HNTs) were developed as a novel non-viral gene vector. To increase the efficiency of endocytosis, HNTs were firstly shortened into an appropriate size (~200nm). Then polyethyleneimine (PEI) was grafted onto HNTs to bind green fluorescence protein (GFP) labeled pDNA. The structure and physical-chemical properties of PEI grafted HNTs (PEI-g-HNTs) were characterized by various methods. PEI-g-HNTs show lower cytotoxicity than PEI. PEI-g-HNTs are positively charged and can bind DNA tightly at designed N/P ratio from 5:1 to 40:1. PEI-g-HNTs/pDNA complexes show much higher transfection efficiency towards both 293T and HeLa cells compared with PEI/pDNA complexes at the equivalent N/P ratio. The transfection efficiencies of PEI-g-HNTs/pDNA complex towards HeLa cell can reach to 44.4% at N/P ratio of 20. PEI-g-HNTs/pDNA complexes possess a higher GFP protein expression than PEI/pDNA from simple western immunoblots. So, PEI-g-HNTs are potential gene vectors with good biocompatibility and high transfection efficiency, which have promising applications in cancer gene therapy. Copyright © 2017 Elsevier B.V. All rights reserved.

Antioxidant multi-walled carbon nanotubes by free radical grafting of gallic acid: new materials for biomedical applications.

Science.gov (United States)

Cirillo, Giuseppe; Hampel, Silke; Klingeler, Rüdiger; Puoci, Francesco; Iemma, Francesca; Curcio, Manuela; Parisi, Ortensia Ilaria; Spizzirri, Umile Gianfranco; Picci, Nevio; Leonhardt, Albrecht; Ritschel, Manfred; Büchner, Bernd

2011-02-01

To prove the possibility of covalently functionalizing multi-walled carbon nanotubes (CNTs) by free radical grafting of gallic acid on their surface with the subsequent synthesis of materials with improved biological properties evaluated by specific in-vitro assays. Antioxidant CNTs were synthesized by radical grafting of gallic acid onto pristine CNTs. The synthesis of carbon nanotubes was carried out in a fixed-bed reactor and, after the removal of the amorphous carbon, the grafting process was performed. The obtained materials were characterized by fluorescence and Fourier transform infrared spectroscopy (FT-IR) analyses. After assessment of the biocompatibility and determination of the disposable phenolic group content, the antioxidant properties were evaluated in terms of total antioxidant activity and scavenger ability against 2,2'-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl and peroxyl radicals. Finally the inhibition activity on acetylcholinesterase was evaluated.   The covalent functionalization of CNTs with gallic acid was confirmed and the amount of gallic acid bound per g of CNTs was found to be 2.1±0.2 mg. Good antioxidant and scavenging properties were recorded in the functionalized CNTs, which were found to be able to inhibit the acetylcholinesterase with potential improved activity for biomedical and pharmaceutical applications. For the first time, a free radical grafting procedure was proposed as a synthetic approach for the covalent functionalization of CNTs with an antioxidant polyphenol. © 2010 The Authors. JPP © 2010 Royal Pharmaceutical Society.

Moisture condensation behavior of hierarchically carbon nanotube-grafted carbon nanofibers.

Science.gov (United States)

Park, Kyu-Min; Lee, Byoung-Sun; Youk, Ji Ho; Lee, Jinyong; Yu, Woong-Reol

2013-11-13

Hierarchical micro/nanosurfaces with nanoscale roughness on microscale uneven substrates have been the subject of much recent research interest because of phenomena such as superhydrophobicity. However, an understanding of the effect of the difference in the scale of the hierarchical entities, i.e., nanoscale roughness on microscale uneven substrates as opposed to nanoscale roughness on (a larger) nanoscale uneven surface, is still lacking. In this study, we investigated the effect of the difference in scale between the nano- and microscale features. We fabricated carbon nanotube-grafted carbon nanofibers (CNFs) by dispersing a catalyst precursor in poly (acrylonitrile) (PAN) solution, electrospinning the PAN/catalyst precursor solution, carbonization of electrospun PAN nanofibers, and direct growth of carbon nanotubes (CNTs) on the CNFs. We investigated the relationships between the catalyst concentrations, the size of catalyst nanoparticles on CNFs, and the sizes of CNFs and CNTs. Interestingly, the hydrophobic behavior of micro/nano and nano/nano hierarchical surfaces with water droplets was similar; however a significant difference in the water condensation behavior was observed. Water condensed into smaller droplets on the nano/nano hierarchical surface, causing it to dry much faster.

Surface modification of TiO2 nanotubes by grafting with APTS coupling agents

Science.gov (United States)

Phan Duong, Hong; Le, Minh Duc; Dao, Hung Cuong; Chen, Chia-Yun

2017-10-01

Titanium dioxide nanotubes (TNTs) have been considered the promising nanostructures employed for many practical applications such as biomedical, photonic and optoelectronic devices. Nevertheless, strong aggregation of TNTs within various aqueous media significantly hindered their practical utilizations and the capability of dispersing TNTs in the desired solvents are urgent to be improved. Therefore, in this study, the methodic investigations have been performed on the grafted modification of 3-aminopropyl triethoxysilane (APTS) on the surfaces of synthesized TNTs. A preliminary study was carried out to evaluate the influences of key parameters, including the concentrations of coupling agents, temperatures and the reaction durations, on the grafting efficiency of the aminosilane using Statistical design of experiments (DoE) methodology. TNTs with approximately 10-20 nm in diameter were prepared with the controlled hydrothermal treatment of commercialized P25 particles. The obtained products were revealed by the modern physicochemical systems including x-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) analysis. The additions of silane agent, reaction temperature and time have been adjusted to reveal the influences of the grafting efficiency (from 2.5 to 7.8 wt %) by thermal gravimetric analysis (TGA). Analysis of Fourier transform infrared spectroscopy (FTIR) has confirmed the successful link of Ti-O-Si chemical bonds on the grafted TNTs.

Silver oxide nanocrystals anchored on titanate nanotubes and nanofibers: promising candidates for entrapment of radioactive iodine anions.

Science.gov (United States)

Yang, Dongjiang; Liu, Hongwei; Liu, Long; Sarina, Sarina; Zheng, Zhanfeng; Zhu, Huaiyong

2013-11-21

Iodine radioisotopes are released into the environment by the nuclear industry and medical research institutions using radioactive materials. The (129)I(-) anion is one of the more mobile radioactive species due to a long half-life, and it is a great challenge to design long-term management solutions for such radioactive waste. In this study, a new adsorbent structure with the potential to efficiently remove radioactive iodine anions (I(-)) from water is devised: silver oxide (Ag2O) nanocrystals firmly anchored on the surface of titanate nanotubes and nanofibers via coherent interfaces between Ag2O and titanate phases. I(-) anions in fluids can easily access the Ag2O nanocrystals and be efficiently trapped by forming AgI precipitate that firmly attaches to the adsorbent. Due to their one-dimensional morphology, the new adsorbents can be readily dispersed in liquids and easily separated after purification; and the adsorption beds loaded with the adsorbents can permit high flux. This significantly enhances the adsorption efficiency and reduces the separation costs. The proposed structure reveals a new direction in developing efficient adsorbents for the removal of radioactive anions from wastewater.

Formation of titanate nanostructures under different NaOH concentration and their application in wastewater treatment

International Nuclear Information System (INIS)

Huang Jiquan; Cao Yongge; Deng Zhonghua; Tong Hao

2011-01-01

The effects of the concentration of NaOH on the formation and transformation of various titanate nanostructures were studied. With increasing NaOH concentration, three different formation mechanisms were proposed. Nanotubes can only be obtained under moderate NaOH conditions, and should transform into nanowires with prolonged hydrothermal treatment, and their formation rate is accelerated by increasing NaOH concentration. Low concentration of NaOH results in the direct formation of nanowires, while extra high concentration of NaOH leads to the formation of amorphous nanoparticles. Adsorption and photocatalysis studies show that titanate nanowires and nanotubes might be potential adsorbents for the removal of both heavy metal ions and dyes and photocatalysts for the removal of dyes from wastewater. -- Graphical abstract: The morphologies of the titanates depend deeply on the concentration of NaOH. With increasing NaOH concentration, three different formation mechanisms were proposed. The application of these titanate nanostructures in the wastewater treatment was studied. Display Omitted Research highlights: → Effect of NaOH concentration on the structures of various titanates was reported. → Three different formation mechanisms were presented with increasing NaOH concentration. → Various titanates were used as adsorbents/photocatalysts in wastewater treatment.

Influence of dehydrated nanotubed titanic acid on charge transport and luminescent properties of polymer light-emitting diodes with fluorescent dye

Science.gov (United States)

Qian, Lei; Bera, Debasis; Jin, Zhen-Sheng; Du, Zu-Liang; Xu, Zheng; Teng, Feng; Liu, Wei

2007-09-01

In this paper, we discuss the influence of dehydrated nanotubed titanic acid (DNTA) on charge transport and luminescent properties of polymer light-emitting diodes (PLEDs) doped with fluorescent dye. Photoluminescence results confirm the efficient energy transfer from PVK to 4-(dicyanom-ethylene)-2- t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) and tris-(8-hydroxtquinoline) aluminum (Alq 3) in a DNTA-doped device. The device showed lower turn-on voltages and higher charge current by doping with DNTA, which also caused a shift in the exciton's recombination region.

Chemical Tuning of Adsorption Properties of Titanate Nanotubes

Directory of Open Access Journals (Sweden)

Anastasia V. Grigorieva

2012-01-01

Full Text Available A conventional hydrothermal method widely used for the preparation of titania-based nanotubes still generates many unsolved questions. One of them is definitely connected with the influence of a posthydrothermal treatment of titania nanotubes on their micromorphology, structure, and adsorption characteristics. Here, it was analyzed systematically by a group of methods including nitrogen adsorption and temperature-programmed desorption of ammonia and carbon dioxide. It is proved that adsorption characteristics and the surface state of titania nanotubes correlate with a sodium content, since sodium ions act as Lewis acid sites and shield Ti4+ acid sites of the nanotubes. To obey a balance between chemical and heat treatments of the nanotubes to design their functional properties has been suggested.

XNBR-grafted halloysite nanotube core-shell as a potential compatibilizer for immiscible polymer systems

Science.gov (United States)

Paran, S. M. R.; Naderi, G.; Ghoreishy, M. H. R.

2016-09-01

Halloysite nanotubes (HNTs) grafted with carboxylated nitrile byutadiene rubber (XNBR) were synthesized via a sol-gel method. The HNTs as an inorganic cores were pre-treated with 3-Glycidoxypropyl trimethoxysilane, then successfully coated with the XNBR as an organic shell. The properties of XNBR-grafted HNTs were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results suggested that the XNBR grafted to the surfaces of HNTs successfully. Then the TPE nanocomposites based on polyamide-6 (PA6) and nitrile butadiene rubber (NBR) containing various XNBR-grafted and pristine HNTs were prepared via a direct melt mixing method. The morphology, mechanical, dynamic mechanical and rheological properties of the prepared TPE nanocomposites were investigated. The results show that the XNBR-grafted HNTs can effectively improve the morphology and mechanical properties of the PA6/NBR TPEs. The morphology study of the prepared nanocomposites show that the effect of XNBR-grafted HNTs on the size reduction of NBR phase is markedly more effective than the pristine HNTs and rose by 50% in the same concentrations. Mechanical measurements show that the Young's modulus of the TPE nanocomposites rose by 60% in just 7 wt% of XNBR-grafted HNT loading. The results indicate that the introduction of HNT/XNBR core-shells into the PA6/NBR TPEs can enhances the interfacial interactions and provides a more fine rubber phase morphology and controlled mechanical properties in comparison with the accordingly TPE nanocomposites containing pristine HNTs.

Poly(lauryl acrylate) and poly(stearyl acrylate) grafted multiwalled carbon nanotubes for polypropylene composites

DEFF Research Database (Denmark)

Daugaard, Anders Egede; Jankova Atanasova, Katja; Hvilsted, Søren

2014-01-01

Two new polymer grafts on an industrial grade multiwalled carbon nanotube (MWCNT) were prepared through a non-oxidative pathway employing controlled free radical polymerization for surface initiated polymer grafting. After photochemical introduction of an ATRP initiator onto the MWCNT......, polymerizations of lauryl or stearyl acrylate were performed, resulting in two novel polymer modifications on the MWCNT (poly(lauryl acrylate) or poly(stearyl acrylate)). The method was found to give time dependent loading of polymers as a function of time (up to 38 wt% for both acrylates), and showed a plateau...... in loading after 12 h of polymerization. The modified nanomaterials were melt mixed into polypropylene composites with very low filler loading (0.3 wt%), whereafter both the thermal and electrical properties were investigated by DSC and dielectric resonance spectroscopy. The electrical properties were found...

Selective Grafting of Primary Amines onto Carbon Nanotubes via Free-Radical Treatment in Microwave Plasma Post-Discharge

Directory of Open Access Journals (Sweden)

Philippe Dubois

2012-01-01

Full Text Available A novel strategy to graft functional groups at the surface of carbon nanotubes (CNTs is discussed. Aiming at grafting nitrogen containing groups, and more specifically primary amine covalent functionalization, CNTs were exposed under atomic nitrogen flow arising from an Ar + N2 microwave plasma. The primary amine functions were identified and quantified through chemical derivatization with 4-(trifluoromethylbenzaldehyde and characterized through X-ray photoelectron spectroscopy. The increase of the selectivity in the primary amines grafting onto CNTs, up to 66.7% for treatment of CNT powder, was performed via the reduction of post-treatment oxygen contamination and the addition of hydrogen in the experimental set-up, more particularly in the plasma post-discharge chamber. The analyses of nitrogenated and primary amine functions grafting on the CNT surface suggest that atomic nitrogen (N• and reduced nitrogen species (NH• and NH2• react preferentially with defect sites of CNTs and, then, only atomic nitrogen continues to react on the CNT surface, creating defects.

Microwave-induced titanate nanotubes and the corresponding behaviour after thermal treatment

International Nuclear Information System (INIS)

Ou, H H; Lo, S L; Liou, Y H

2007-01-01

This study attempts to survey the influence of microwave irradiation on the characterizations of titanate nanotubes (TNTs) synthesized by microwave hydrothermal treatment (M-H treatment). Based on the performance of specific surface areas determined by the classic Brunauer-Emmett-Teller method (S BET ), TNTs synthesized at 130 deg. C for 1.5 h with and without 400 W irradiation presented S BET values of 256 and 76 m 2 g -1 , respectively. The result indicates that the formation kinetics of TNTs is significantly enhanced by M-H treatment. The microwave-induced TNTs are preferentially assigned for Na x H 2-x Ti 3 O 7 structure and the Na/H ratio appreciably increases with higher irradiation power. Regarding the behaviour of TNTs after thermal treatment, TNTs synthesized under 70 W presented anatase phase at 500 deg. C through rearrangement and restacking of [TiO 6 ]. Anatase-to-rutile transformation subsequently occurred at 700 deg. C. TNTs synthesized under 400 and 700 W presented a rod shape at 700 deg. C. The rod shape mainly comprise of Na 2 Ti 6 O 13 of which the (Ti 3 O 7 ) 2- layers with the topotactical connection proceed to form (Ti 6 O 13 ) 2- along the [110] direction during the thermal process

A study involving mordenite, titanate nanotubes, perfluoroalkoxy polymers, and ammonia borane

Science.gov (United States)

Nosheen, Shaneela

Zeolites and molecular sieves are finding applications in many areas of catalysis due to appreciable acid activity, shape selectivity, and ion-exchange capacity, as they possess an unbalanced framework charge. For catalytic applications, zeolites become more valuable as the ratio of SiO2/Al2O 3 increases. Acid resistance and thermal stability of zeolite are both improved with increasing SiO2/Al2O3. This part of the thesis deals with the control of morphology focused on decreasing the crystal diameter of mordenite zeolite and to increase the SiO2/Al 2O3 ratio by changing synthesis conditions. A high SiO 2/Al2O3 ratio (SAR15) of mordenite was prepared in a very short reaction time. We studied the role of hydroxide in the crystallization of the mordenite as a structure director, nucleation time modifier, and crystallite aggregate enhancer. The formation of nano-aggregates of mordenites was greatly enhanced using a combination of alcohol additives and conventional heating. Mordenite nucleation was also increased without using alcohols when microwave heating was employed, but the alcohols further accelerated the nucleation process. The different heating techniques affected the morphology; microwave heating produced crystallites of ˜40 nm, while the conventional hydrothermal method formed larger size crystallites of ˜88 nm. We controlled the size and shape of the mordenite crystals because they have important implications in hydrocarbon conversion and separation processes. Mordenite synthesized showed jellyfish, acicular, flower, and wheat grain like structures. In the second part of this thesis, a phase transition was successfully achieved from TiO2 particles to titanate nanotubes by the breakage of Ti-O bonds and the creation of oxygen vacancies without using expensive precursors, high temperatures, high chemical concentrations of alkaline solutions, and long synthesis times. A combination of anatase nano-particles/titanate nano-tubes was synthesized using TiO2

XNBR-grafted halloysite nanotube core-shell as a potential compatibilizer for immiscible polymer systems

Energy Technology Data Exchange (ETDEWEB)

Paran, S.M.R.; Naderi, G., E-mail: g.naderi@ippi.ac.ir; Ghoreishy, M.H.R.

2016-09-30

Highlights: • Attached an utilitarian silane coupling agent to the HNT via a sol-gel method. • Developed and analyzed the HNT/XNBR core-shell particles via sol-gel technique. • Enhanced the reactivity of the surface of HNT through XNBR grafting. • The act of HNT/XNBR as a compatibilizer in PA6/NBR TPEs. • Immiscible Polymer System with a good balanced physical and mechanical properties. - Abstract: Halloysite nanotubes (HNTs) grafted with carboxylated nitrile byutadiene rubber (XNBR) were synthesized via a sol-gel method. The HNTs as an inorganic cores were pre-treated with 3-Glycidoxypropyl trimethoxysilane, then successfully coated with the XNBR as an organic shell. The properties of XNBR-grafted HNTs were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results suggested that the XNBR grafted to the surfaces of HNTs successfully. Then the TPE nanocomposites based on polyamide-6 (PA6) and nitrile butadiene rubber (NBR) containing various XNBR-grafted and pristine HNTs were prepared via a direct melt mixing method. The morphology, mechanical, dynamic mechanical and rheological properties of the prepared TPE nanocomposites were investigated. The results show that the XNBR-grafted HNTs can effectively improve the morphology and mechanical properties of the PA6/NBR TPEs. The morphology study of the prepared nanocomposites show that the effect of XNBR-grafted HNTs on the size reduction of NBR phase is markedly more effective than the pristine HNTs and rose by 50% in the same concentrations. Mechanical measurements show that the Young’s modulus of the TPE nanocomposites rose by 60% in just 7 wt% of XNBR-grafted HNT loading. The results indicate that the introduction of HNT/XNBR core-shells into the PA6/NBR TPEs can enhances the interfacial interactions

XNBR-grafted halloysite nanotube core-shell as a potential compatibilizer for immiscible polymer systems

International Nuclear Information System (INIS)

Paran, S.M.R.; Naderi, G.; Ghoreishy, M.H.R.

2016-01-01

Highlights: • Attached an utilitarian silane coupling agent to the HNT via a sol-gel method. • Developed and analyzed the HNT/XNBR core-shell particles via sol-gel technique. • Enhanced the reactivity of the surface of HNT through XNBR grafting. • The act of HNT/XNBR as a compatibilizer in PA6/NBR TPEs. • Immiscible Polymer System with a good balanced physical and mechanical properties. - Abstract: Halloysite nanotubes (HNTs) grafted with carboxylated nitrile byutadiene rubber (XNBR) were synthesized via a sol-gel method. The HNTs as an inorganic cores were pre-treated with 3-Glycidoxypropyl trimethoxysilane, then successfully coated with the XNBR as an organic shell. The properties of XNBR-grafted HNTs were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results suggested that the XNBR grafted to the surfaces of HNTs successfully. Then the TPE nanocomposites based on polyamide-6 (PA6) and nitrile butadiene rubber (NBR) containing various XNBR-grafted and pristine HNTs were prepared via a direct melt mixing method. The morphology, mechanical, dynamic mechanical and rheological properties of the prepared TPE nanocomposites were investigated. The results show that the XNBR-grafted HNTs can effectively improve the morphology and mechanical properties of the PA6/NBR TPEs. The morphology study of the prepared nanocomposites show that the effect of XNBR-grafted HNTs on the size reduction of NBR phase is markedly more effective than the pristine HNTs and rose by 50% in the same concentrations. Mechanical measurements show that the Young’s modulus of the TPE nanocomposites rose by 60% in just 7 wt% of XNBR-grafted HNT loading. The results indicate that the introduction of HNT/XNBR core-shells into the PA6/NBR TPEs can enhances the interfacial interactions

ENHANCING DIRECT ELECTRON TRANSFER OF GLUCOSE OXIDASE USING A GOLD NANOPARTICLE |TITANATE NANOTUBE NANOCOMPOSITE ON A BIOSENSOR

International Nuclear Information System (INIS)

Zhao, Ruoxia; Liu, Xiaoqiang; Zhang, Jiamei; Zhu, Jie; Wong, Danny K.Y.

2015-01-01

ABSTRACT: In this paper, we have developed a gold nanoparticle (GNP) decorated titanate nanotubes (TNT) nanocomposite that aids in the direct electron transfer of a large enzyme, such as glucose oxidase (GOD), in which the electroactive site of flavin adenine dinucleotide is deeply buried within the enzyme. The ionic liquid, brominated 1-decyl-3-methyl imidazole, was used to immobilise the nanocomposite and the enzyme on a glassy carbon electrode to further aid in the electron transfer between GOD and the electrode surface. Nafion was also added to anchor the biosensor scaffold. Initially, the tubiform geometry of titanate nanomaterials and the GNP-TNT nanocomposite was confirmed by microscopic and spectroscopic techniques before glucose oxidase was entrapped in the nanocomposite. Based on voltammetric results, this biosensor showed a strong electrocatalytic capability towards glucose (with a heterogeneous electron transfer rate constant of 7.1 s −1 at 180 mV s −1 ) and the calibration for glucose exhibited a high sensitivity (5.1 μA mM −1 ) and a wide linear range (0.01–1.2 mM). These results demonstrated superior analytical performance of our biosensor over others fabricated using bulkier TiO 2 nanoparticles or nanobundles, which could be attributed to a high degree of biocompatibility to glucose oxidase and electrical conductivity of the nanocomposite

Carrier transport and luminescence properties of nanocomposites of poly[2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene] and dehydrated nanotubes titanic acid.

Science.gov (United States)

Zhang, Ting; Xu, Zheng; Liu, Ran; Teng, Feng; Wang, Yongsheng; Xu, Xurong

2007-12-01

The carrier transport capability and luminescence efficiency of poly(2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene) (MEH-PPV) films are enhanced by doping with dehydrated nanotubed titanic acid (DNTA). MEH-PPV molecules, either wrapped on the outer surface of or encapsulated into DNTA pores, have a more open, straighter conformation than undoped molecules, which induces a longer conjugated backbone and stronger interchain interactions, thereby, enhancing carrier mobility. MEH-PPV molecules within DNTA pores have higher exciton recombination efficiency owing to quantum confinement and the antenna effect.

Wear of carbon nanotubes grafted on carbon fibers and this influence on the properties of composites materials

Science.gov (United States)

Guignier, Claire; Bueno, Marie-Ange; Camillieri, Brigitte; Durand, Bernard

2017-10-01

Carbon nanotubes (CNTs) grafted on carbon surfaces can be used to reinforce composite materials. During an industrial process of CNTs production and composite processing, friction stresses will be applied on CNTs. This study showed that CNTs formed a transfer film under friction stresses and that the wear of the CNTs has no influence on the wettability of the surface, so we can predict no decrease in the properties of composites.

Thermal stability of titanate nanorods and titania nanowires formed from titanate nanotubes by heating

Czech Academy of Sciences Publication Activity Database

Brunátová, T.; Matěj, Z.; Oleynikov, P.; Vesely, J.; Danis, S.; Popelková, Daniela; Kuzel, R.

2014-01-01

Roč. 98, December (2014), s. 26-36 ISSN 1044-5803 Institutional support: RVO:61389013 Keywords : titania nanowires * titanate nanorods * X-ray diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.845, year: 2014

A Raman Study of Titanate Nanotubes

African Journals Online (AJOL)

NJD

HRTEM data are also consistent with the synthesis of ... The nano titania produced by the electrochemical and template methods, gave amorphous titania while titania nanotubes produced by 'soft' chemical processes gave materials with good.

Enhanced performance of light-emitting diodes based on a nanocomposite of dehydrated nanotube titanic acid and poly(vinylcarbazole) (PVK)

Energy Technology Data Exchange (ETDEWEB)

Qian, L. [Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China)]. E-mail: qian_lei@126.com; Yang, S.Y. [Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China); Jin, Z.S. [Key Laboratory on Special Functional Materials, Henan University, Kaifeng 475001 (China); Zhang, Z.J. [Key Laboratory on Special Functional Materials, Henan University, Kaifeng 475001 (China); Zhang, T. [Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China); Teng, F. [Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China); Xu, X.R. [Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China)

2005-01-31

Performance of light-emitting diodes (LEDs) based on a nanocomposite of dehydrated nanotube titanic acid (DNTA) and poly(vinylcarbazole) (PVK) as emissive layer, i.e., ITO/PVK:DNTA(2 wt%)(100 nm)/BCP(30 nm)/Alq{sub 3}(10 nm)/LiF(1 nm)/Al [device D{sub 2}], was reported. By investigation of the luminance and electric characteristics of the device, we found that the performance of device D{sub 2} was greatly improved. The recombination zone changed evidently due to the improvement of holes mobility. Compared with those devices without incorporating DNTA, both the maximum luminance and the electroluminescent efficiency of the device D{sub 2} can be improved by a factor of three. Furthermore, the turn-on voltage of the device decreased dramatically.

Carbon Nanotube Composite SHM Sensor using Additive Manufacturing

Data.gov (United States)

National Aeronautics and Space Administration — We propose to develop a piezoelectric sensors made of carbon nanotube and lead zirconium titanate (PZT) nanopower dispersed in a polymer matrix. These sensors will...

Estimation of degree of polymerization of poly-acrylonitrile-grafted carbon nanotubes using Guinier plot of small angle x-ray scattering.

Science.gov (United States)

Cho, Hyunjung; Jin, Kyeong Sik; Lee, Jaegeun; Lee, Kun-Hong

2018-07-06

Small angle x-ray scattering (SAXS) was used to estimate the degree of polymerization of polymer-grafted carbon nanotubes (CNTs) synthesized using a 'grafting from' method. This analysis characterizes the grafted polymer chains without cleaving them from CNTs, and provides reliable data that can complement conventional methods such as thermogravimetric analysis or transmittance electron microscopy. Acrylonitrile was polymerized from the surface of the CNTs by using redox initiation to produce poly-acrylonitrile-grafted CNTs (PAN-CNTs). Polymerization time and the initiation rate were varied to control the degree of polymerization. Radius of gyration (R g ) of PAN-CNTs was determined using the Guinier plot obtained from SAXS solution analysis. The results showed consistent values according to the polymerization condition, up to a maximum R g  = 125.70 Å whereas that of pristine CNTs was 99.23 Å. The dispersibility of PAN-CNTs in N,N-dimethylformamide was tested using ultraviolet-visible-near infrared spectroscopy and was confirmed to increase as the degree of polymerization increased. This analysis will be helpful to estimate the degree of polymerization of any polymer-grafted CNTs synthesized using the 'grafting from' method and to fabricate polymer/CNT composite materials.

Enhanced luminol electrochemiluminescence triggered by an electrode functionalized with dendrimers modified with titanate nanotubes

International Nuclear Information System (INIS)

Lin, Yanyu; Yang, Yusheng; Dai, Hong; Xu, Guifang; Yang, Ting; Tong, Yuejin; Yang, Caiping; Chen, Guonan

2013-01-01

We have constructed a novel electro chemiluminescence (ECL) platform by functionalizing a poly(amidoamine) dendrimer (PAAD) with titanate nanotubes (TiNTs). The PAAD has an open spherical structure that possesses a high density of active groups and thus favors mass transport, while the TiNTs possess excellent electronic conductivity and thus can promote electron transfer on the surface of a glassy carbon electrode (GCE). A study on the intensity and stability of the ECL of luminol on the modified GCE revealed a substantial improvement compared to that of a bare GCE. The effects of the concentration of TiNTs, the pH value of the solution, and of electrochemical parameters on the intensity of the ECL of luminol were studied and resulted in a sensitive ECL sensor for hydrogen peroxide (H 2 O 2 ) that works in the concentration range of 1 nM to 0.9 μM. The scavenging effect of superoxide dismutase (SOD) on the H 2 O 2 electrode ECL was then exploited to design a biosensor for the determination of SOD in concentrations between 50 and 500 nM. (author)

High photoactive and visible-light responsive graphene/titanate nanotubes photocatalysts: preparation and characterization.

Science.gov (United States)

Qianqian, Zhai; Tang, Bo; Guoxin, Hu

2011-12-30

A series of graphene/titanate nanotubes (TNTs) photocatalysts using graphene and nanoscale TiO(2) or P25 as original materials were fabricated by hydrothermal method. Both low hydrothermal temperature and proper amount of graphene are propitious to better photoactivity. The photocatalytic activities of these nanocomposites far exceed that of P25, pure TNTs and reported TiO(2)-based nanocomposites for the degradation of Rhodamine-B under visible-light irradiation. These prepared photocatalysts were characterized by TEM, XRD, XPS, BET, FTIR and UV-vis diffuse reflection spectra, and the results indicate that the outstanding photoactivities in visible-light region result from sensitization effect of graphene rather than impurity level in the band gap of TNTs. Furthermore, large BET surface areas of these photocatalysts (almost 10 times larger than that of previously reported graphene/TiO(2) nanoparticles) evidently enhance their absorption abilities and photocatalytic performances (the rate constants of degrading Rhodamine-B are at least 5 times higher than that of previously reported photocatalysts). These photocatalysts show good stability, and their photoactivities do not obviously decrease after four times of repeated uses. A detailed photocatalytic mechanism is suggested, as well. Copyright © 2011 Elsevier B.V. All rights reserved.

Boosted surface acidity in TiO{sub 2} and Al{sub 2}O{sub 3}-TiO{sub 2} nanotubes as catalytic supports

Energy Technology Data Exchange (ETDEWEB)

Camposeco, R. [Molecular Engineering Program, Mexican Institute of Petroleum, 07730, México, D.F. (Mexico); Department of Chemistry, UAM-A, 55534, México, D.F. (Mexico); Castillo, S., E-mail: scastill@imp.mx [Molecular Engineering Program, Mexican Institute of Petroleum, 07730, México, D.F. (Mexico); Department of Chemical Engineering, ESIQIE-IPN, 75876, México, D.F. (Mexico); Mejía-Centeno, Isidro; Navarrete, J.; Nava, N. [Molecular Engineering Program, Mexican Institute of Petroleum, 07730, México, D.F. (Mexico)

2015-11-30

Graphical abstract: - Highlights: • Surface acidity of NTs was modified by adding alumina. • Brönsted acid sites remain constant but Lewis acid sites are increased remarkably. • IR characterization by lutidine and pyridine confirms the surface acidity of NTs. • 98% of NO conversion was reached between 380 and 480 °C on NT-5Al. • The boosted surface acidity of NT-Al improves the catalytic activity for SCR-NO. - Abstract: In this study, titanate nanotubes (NT) and titanate nanotubes with alumina (NT-Al) were studied as solid acid catalytic supports to show the relationship between the kind of acidity and catalytic activity. The supports were characterized by XRD, TEM, FTIR, XPS, and tested in the SCR-NO with NH{sub 3}. It was found that the amount of Brönsted acid sites was maintained and the Lewis acid sites were significantly affected by the addition of alumina (1, 3, 5 and 10 wt.%); such acidity was higher than that of the titanate nanotubes (NT) by two-fold. To confirm the formation of titanate nanotubes and titanate nanotubes with alumina, transmission electron microscopy (TEM) was used. X-ray diffraction (XRD) revealed the formation of the H{sub 2}Ti{sub 4}O{sub 9}·H{sub 2}O phase. All NT and NT-Al supports presented catalytic activity to remove NO with NH{sub 3} under lean conditions, confirming the presence of an important amount of Brönsted and Lewis acid sites in both NT and NT-Al supports.

Electrospun carbon nanofibers surface-grafted with vapor-grown carbon nanotubes as hierarchical electrodes for supercapacitors

Science.gov (United States)

Zhou, Zhengping; Wu, Xiang-Fa; Fong, Hao

2012-01-01

This letter reports the fabrication and electrochemical properties of electrospun carbon nanofibers surface-grafted with vapor-grown carbon nanotubes (CNTs) as hierarchical electrodes for supercapacitors. The specific capacitance of the fabricated electrodes was measured up to 185 F/g at the low discharge current density of 625 mA/g; a decrease of 38% was detected at the high discharge current density of 2.5 A/g. The morphology and microstructure of the electrodes were examined by electron microscopy, and the unique connectivity of the hybrid nanomaterials was responsible for the high specific capacitance and low intrinsic contact electric resistance of the hierarchical electrodes.

Bioelectrocatalytic and biosensing properties of horseradish peroxidase covalently immobilized on (3-aminopropyl)trimethoxysilane-modified titanate nanotubes

International Nuclear Information System (INIS)

Sovic, David; Gajovic, Andreja; Ivekovic, Damir

2011-01-01

Titanate nanotubes (TiNT) surface modified with (3-aminopropyl)trimethoxysilane were employed as a support for covalent immobilization of horseradish peroxidase (HRP) by using 1,4-benzoquinone as a coupling agent. Composite film-electrodes consisting of HRP-modified TiNT embedded into the porous carbon powder/Nafion matrix were fabricated and their applicability in direct bioelectrocatalytic reduction of H 2 O 2 and H 2 O 2 biosensing were investigated. An efficient direct electron transfer between the immobilized HRP molecules and the electrode was observed in the presence of H 2 O 2 at potentials lower than 600 mV (vs. Hg/Hg 2 Cl 2 /3.5 M KCl). For the HRP-TiNT-modified electrodes polarized at 0 mV, a linear dependence of the bioelectrocatalytic current on the concentration of H 2 O 2 was observed up to the concentration of H 2 O 2 equal to 10 μM, with the sensitivity of (1.10 ± 0.01) AM -1 cm -2 and the detection limit of 35 nM.

Titania nanotube stabilized BiOCl nanoparticles in visible-light photocatalysis

KAUST Repository

Buchholcz, B.

2017-03-14

Photocatalysis is a green approach in environmental organic pollutant decomposition. Lately, considerable improvement in the activity of photocatalysts has been achieved with the realization of p–n heterostructures due to the lifetime extension of the photogenerated charge carriers. Herein, we report a facile synthesis approach for decorating n-type titanate nanotubes with p-type V–VI–VII compound semiconductor BiOCl nanoparticles. It is well-known that BiOX (X = Cl, Br, I) materials form nanometer-thick platelets, which can eventually assemble into micrometer size flower-like 3D structures. Here, we demonstrate that the tubular titanate support can stabilize BiOCl on its surface in the form of nanoparticles measuring a few nanometers in diameter, instead of forming the well-known bismuth-oxyhalide nanoflowers. Subsequent calcination at 400 °C transforms the pristine titanate structures into one-dimensional anatase nanotubes, along with the formation of a heterojunction at the interface of the emerging Bi2Ti2O7 and anatase phases. The resulting nanocomposite shows activity in visible-light photocatalytic test reactions.

Poly(ethylene-co-butylene) functionalized multi walled carbon nanotubes applied in polypropylene nanocomposites

DEFF Research Database (Denmark)

Daugaard, Anders Egede; Jankova Atanasova, Katja; Marín, Jose Manuel Roman

2012-01-01

A novel functionalized multi walled carbon nanotube (MWCNT) was prepared through grafting with α-azido-poly(ethylene-co-butylene) (PEB-N3). The PEB-N3 was prepared through a two step procedure and grafted onto an industrial grade multi walled carbon nanotube (MWCNT) through a highly efficient...

Synthesis and electrochemical probing of water-soluble poly(sodium 4-styrenesulfonate-co-acrylic acid)-grafted multiwalled carbon nanotubes

International Nuclear Information System (INIS)

Du Feipeng; Yang Yingkui; Xie Xiaolin; Wu Kangbing; Gan Tian; Liu Lang

2008-01-01

Water-soluble poly(sodium 4-styrenesulfonate-co-acrylic acid)-grafted multiwalled carbon nanotubes (MWNT-g-P(SSS-co-AA)) with core-shell nanostructure were successfully synthesized by in situ free radical copolymerization of sodium 4-strenesulfonate (SSS) and acrylic acid (AA) in the presence of MWNTs terminated with vinyl groups; their structure was characterized by FTIR, 1 H NMR, Raman, TGA and TEM. The results showed that the thickness and content of the copolymer layer grafted onto the MWNT surface are about 7-12 nm and 82.3%, respectively. The P(SSS-co-AA) covalently grafted on MWNTs provides MWNT-g-P(SSS-co-AA) with good hydrophilicity and solubility in water. Then a novel MWNT-g-P(SSS-co-AA)-modified glassy carbon electrode was fabricated by coating; its electrochemical properties were evaluated by electrochemical probe of K 3 [Fe(CN) 6 ], and its catalytic behaviors to the electrochemical oxidation processes of dopamine (DA) and serotonin (5-HT) were investigated. Since the MWNT-g-P(SSS-co-AA)-modified electrode possesses strong electron transfer capability, high electrochemical activity and catalytic ability, it can be used in sensitive, selective, rapid and simultaneous monitoring of biomolecules

Determination of X-Ray Diffraction on the Phase Transformation of Microwave-Assisted Titanate Nanotubes during Thermal Treatment

Directory of Open Access Journals (Sweden)

Hsin-Hung Ou

2010-01-01

Full Text Available Based on the determination of X-ray powder diffraction, this study aims to investigate the thermal effect on the phase transformation of microwave-assisted titanate nanotubes (MTNTs. The phase transformation is highly dependent on the intercalating amount of Na(I within MTNTs and on the heating atmosphere. In other words, the presence of Na(I favors the transformation of TNTs phase into Na2Ti6O13 whereas anatase phase selectively formed in the case of MTNTs with less Na(I amount. Furthermore, H2 versus O2 is able to form anatase phase and establish a newly transformation pathway. The photocatalytic ability of the calcined MTNTs was also evaluated based on the observed rate constant of trichloroethylene degradation. In addition to anatase phase, the newly phase including Na2Ti6O13 and Ti2O3 with calcined MTNTs is able to photocatalyze trichloroethylene. MTNTs calcined with the presence of H2 also exhibit a superior photocatalytic performance to P25 TiO2.

Template-based electrophoretic deposition of perovskite PZT nanotubes

Energy Technology Data Exchange (ETDEWEB)

Nourmohammadi, A. [Solid Surfaces Analysis and Electron Microscopy Group, Institute of Physics, Chemnitz University of Technology, D-09126 Chemnitz (Germany); Semiconductors Department, Materials and Energy Research Center (MERC), 31779-83634 Karaj (Iran, Islamic Republic of); Bahrevar, M.A. [Semiconductors Department, Materials and Energy Research Center (MERC), 31779-83634 Karaj (Iran, Islamic Republic of)], E-mail: ma.bahrevar@yahoo.com; Hietschold, M. [Solid Surfaces Analysis and Electron Microscopy Group, Institute of Physics, Chemnitz University of Technology, D-09126 Chemnitz (Germany)

2009-04-03

Template-based electrophoretic deposition of perovskite lead zirconate titanate (PZT) nanotubes was achieved using anodic alumina (AA) membranes and sols, containing lead, zirconium and titanium precursors. The effect of various anodizing voltages on the size of the channels in the anodic alumina template was investigated. The prepared sol was driven into the channels under the influence of various electric fields and subsequently sintered at about 700 deg. C. The effects of the initial heating rates and the burn-out temperature on the phase evolution of the samples were studied and a modified firing process was employed. The effects of the electrophoretic voltage and the deposition time on the average wall thickness of the tubes were investigated. Scanning and transmission electron microscopy (SEM and TEM) revealed the efficiency of electrophoresis in the growth of lead zirconate titanate nanotubes in a close-packed array. The X-ray diffraction analyses indicated the presence of perovskite as the principal phase after a modified firing schedule.

Enhanced CO2 Adsorption on Activated Carbon Fibers Grafted with Nitrogen-Doped Carbon Nanotubes

Directory of Open Access Journals (Sweden)

Yu-Chun Chiang

2017-05-01

Full Text Available In this paper, multiscale composites formed by grafting N-doped carbon nanotubes (CNs on the surface of polyamide (PAN-based activated carbon fibers (ACFs were investigated and their adsorption performance for CO2 was determined. The spaghetti-like and randomly oriented CNs were homogeneously grown onto ACFs. The pre-immersion of cobalt(II ions for ACFs made the CNs grow above with a large pore size distribution, decreased the oxidation resistance, and exhibited different predominant N-functionalities after chemical vapor deposition processes. Specifically, the CNs grafted on ACFs with or without pre-immersion of cobalt(II ions were characterized by the pyridine-like structures of six-member rings or pyrrolic/amine moieties, respectively. In addition, the loss of microporosity on the specific surface area and pore volume exceeded the gain from the generation of the defects from CNs. The adsorption capacity of CO2 decreased gradually with increasing temperature, implying that CO2 adsorption was exothermic. The adsorption capacities of CO2 at 25 °C and 1 atm were between 1.53 and 1.92 mmol/g and the Freundlich equation fit the adsorption data well. The isosteric enthalpy of adsorption, implying physical adsorption, indicated that the growth of CNTs on the ACFs benefit CO2 adsorption.

Platinum-doped titanate nanotubes/reduced graphene oxide: photocatalytic activity and flame retardancy

Science.gov (United States)

Liu, Guangya; Sang, Bin; Zhou, Zhiqi; Li, Zhiwei

2018-01-01

The ‘white pollution’ produced by wasted flexible polyvinyl chloride (PVC) with poor degradation ability and the potential fire hazard of PVC with high flammability not only restrict their application but also cause serious environmental problem. Thus platinum-doped titanate nanotubes/reduced graphene oxide (denoted as Pt-TNTs/rGO) nanocomposites were prepared by a facile method in order to improve the visible photodegradation and get rid of the ‘white pollution’ as well as flame retardancy of PVC. The photodegradation activity and flame retardancy effect of the as-prepared Pt-TNTs/rGO nanocomposites were investigated by ultraviolet and visible light irradiation as well as cone calorimetry. Results show that the Pt-TNTs/rGO-PVC nanocomposites exhibit enhanced visible light photodegradation performance (with mass loss being 6.5%) during 15 day exposure to solar irradiation, and good flame retardancy (providing a 44% reduction of total smoke release as compared with that of PVC matrix). Besides, Pt-TNTs/rGO-PVC nanocomposites show suppressed smoke and reduced CO production as compared with the PVC matrix. These results demonstrate that Pt-TNTs/rGO not only get rid of the ‘white pollution’ as the photocatalyst but also improve the fire safety of PVC as the flame retardant. This could be ascribed to the combination effect between Pt-TNTs and rGO. The present research, hopefully, is to pave a potential pathway to constructing polymer-matrix composites with desired photodegradation activity and flame retardancy, thereby shedding light on simultaneously dealing with the ‘white pollution’ and high flammability of polymer matrix like PVC.

Cryogel-supported titanate nanotubes for waste treatment: Impact on methane production and bio-fertilizer quality.

Science.gov (United States)

Önnby, Linda; Harald, Kirsebom; Nges, Ivo Achu

2015-08-10

By reducing the cadmium (Cd(2+)) content in biomass used for bio-based products such as biogas, a less toxic bio-based fertilizer can be obtained. In this work, we demonstrate how a macroporous polymer can support titanate nanotubes, and we take advantage of its known selective adsorption behavior towards Cd(2+) in an adsorption process from real nutrient-rich process water from hydrolysis of seaweed, a pollutant-rich biomass. We show that pretreatment steps involving alteration in area-to-volume ratio performed in aerated and acidic conditions release the most Cd(2+) from the solid material. By integrating an adsorption step between hydrolysis and the biomethane, we show that it was possible to obtain high Cd(2+) removal (ca. 94%) despite molar excess (between 100 and 500) of co-present ions (e.g., Mg(2+), Ca(2+), Na(+), K(+)) and with maintained total phosphorous content. The bio-methane potential did not significantly decrease as compared to a process without cadmium removal and the yielded bio-fertilizer followed Swedish guideline values. This study provides a sound and promising alternative for a novel remediation step, enabling higher use of otherwise tricky and to some extent overlooked biomass sources. Copyright © 2015. Published by Elsevier B.V.

Titan

Science.gov (United States)

Müller-Wodarg, Ingo; Griffith, Caitlin A.; Lellouch, Emmanuel; Cravens, Thomas E.

2014-03-01

Introduction I. C. F. Müller-Wodarg, C. A. Griffith, E. Lellouch and T. E. Cravens; Prologue 1: the genesis of Cassini-Huygens W.-H. Ip, T. Owen and D. Gautier; Prologue 2: building a space flight instrument: a P.I.'s perspective M. Tomasko; 1. The origin and evolution of Titan G. Tobie, J. I. Lunine, J. Monteux, O. Mousis and F. Nimmo; 2. Titan's surface geology O. Aharonson, A. G. Hayes, P. O. Hayne, R. M. Lopes, A. Lucas and J. T. Perron; 3. Thermal structure of Titan's troposphere and middle atmosphere F. M. Flasar, R. K. Achterberg and P. J. Schinder; 4. The general circulation of Titan's lower and middle atmosphere S. Lebonnois, F. M. Flasar, T. Tokano and C. E. Newman; 5. The composition of Titan's atmosphere B. Bézard, R. V. Yelle and C. A. Nixon; 6. Storms, clouds, and weather C. A. Griffith, S. Rafkin, P. Rannou and C. P. McKay; 7. Chemistry of Titan's atmosphere V. Vuitton, O. Dutuit, M. A. Smith and N. Balucani; 8. Titan's haze R. West, P. Lavvas, C. Anderson and H. Imanaka; 9. Titan's upper atmosphere: thermal structure, dynamics, and energetics R. V. Yelle and I. C. F. Müller-Wodarg; 10. Titan's upper atmosphere/exosphere, escape processes, and rates D. F. Strobel and J. Cui; 11. Titan's ionosphere M. Galand, A. J. Coates, T. E. Cravens and J.-E. Wahlund; 12. Titan's magnetospheric and plasma environment J.-E. Wahlund, R. Modolo, C. Bertucci and A. J. Coates.

Impaction grafting in the femur in cementless modular revision total hip arthroplasty: a descriptive outcome analysis of 243 cases with the MRP-TITAN revision implant

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Wimmer Matthias D

2013-01-01

Full Text Available Abstract Background We present a descriptive and retrospective analysis of revision total hip arthroplasties (THA using the MRP-TITAN stem (Peter Brehm, Weisendorf, GER with distal diaphyseal fixation and metaphyseal defect augmentation. Our hypothesis was that the metaphyseal defect augmentation (Impaction Bone Grafting improves the stem survival. Methods We retrospectively analyzed the aggregated and anonymized data of 243 femoral stem revisions. 68 patients with 70 implants (28.8% received an allograft augmentation for metaphyseal defects; 165 patients with 173 implants (71.2% did not, and served as controls. The mean follow-up was 4.4 ± 1.8 years (range, 2.1–9.6 years. There were no significant differences (p > 0.05 between the study and control group regarding age, body mass index (BMI, femoral defects (types I-III as described by Paprosky, and preoperative Harris Hip Score (HHS. Postoperative clinical function was evaluated using the HHS. Postoperative radiologic examination evaluated implant stability, axial implant migration, signs of implant loosening, periprosthetic radiolucencies, as well as bone regeneration and resorption. Results There were comparable rates of intraoperative and postoperative complications in the study and control groups (p > 0.05. Clinical function, expressed as the increase in the postoperative HHS over the preoperative score, showed significantly greater improvement in the group with Impaction Bone Grafting (35.6 ± 14.3 vs. 30.8 ± 15.8; p ≤ 0.05. The study group showed better outcome especially for larger defects (types II C and III as described by Paprosky and stem diameters ≥ 17 mm. The two groups did not show significant differences in the rate of aseptic loosening (1.4% vs. 2.9% and the rate of revisions (8.6% vs. 11%. The Kaplan-Meier survival for the MRP-TITAN stem in both groups together was 93.8% after 8.8 years. [Study group 95.7% after 8.54 years ; control group 93

Silver decorated titanate/titania nanostructures for efficient solar driven photocatalysis

International Nuclear Information System (INIS)

Gong, Dangguo; Ho, Weng Chye Jeffrey; Tang Yuxin; Tay Qiuling; Lai Yuekun; Highfield, James George; Chen Zhong

2012-01-01

Photocatalysis has attracted significant interest to solve both the energy crisis and effectively combat environmental contamination. However, as the most widely used photocatalyst, titania (TiO 2 ) suffers from inefficient utilization of solar energy due to its wide band gap. In the present paper, we describe a method to extend the absorption edge of photocatalyst to visible region by the surface plasmon effect of silver. Silver ions are photo-reduced onto the surface of titanate nanotubes, which are synthesized by a conventional hydrothermal method. The as-synthesized Ag/titanate composite is transformed into Ag/titania nanoparticles by annealing at different temperatures. It is found that the interaction of Ag nanoparticles with the supports (titanate/titania) plays a key role for the visible light activity. The samples annealed at low temperature (<350 °C) do not show significant activity under our conditions, while the one annealed at 450 °C shows fast-degradation of methyl orange (MO) under visible light irradiation. The detailed mechanisms are also discussed. - Graphical abstract: Silver nanoparticles decorated titanate/titania as visible light active photocatalysts: silver nanoparticles could be excited by visible light due to its surface plasmon effect and excited electrons could be transferred to the conduction band of the semiconductor, where the reduction process occurs. Highlights: ► Uniform Ag nanoparticles are photo-reduced onto titanate and titania nanostructures. ► Titania crystal is formed by annealing hydrogen titanate at different temperatures. ► Best visible-light activity is achieved by Ag-loaded titania annealed at 450 °C. ► The visible light activity is attributed to the surface plasmonic resonance effect.

In situ synthesis of CdS decorated titanate nanosheets with highly efficient visible-light-induced photoactivity

International Nuclear Information System (INIS)

Liu, Zhi; Fang, Pengfei; Liu, Fuwei; Zhang, Yupeng; Liu, Xinzhao; Lu, Dingze; Li, Delong; Wang, Shaojie

2014-01-01

Appropriately dispersed CdS nanoparticles were intimately embedded into titanate nanosheets (TNS) through ion-exchange and in situ sulfurization process. The sheet-like intermediates of titanate during the transforming process into nanotubes were firstly used as substrate for the decoration of CdS nanoparticles, and the synthesis route was achieved by ion-exchange process between titanate precursor and Cd 2+ ions solution, and the following sulfuration process by using Na 2 S solutions. The catalytic activity of the photocatalyst was investigated by photodegradation of Rhodamine B under visible light irradiation. With an optimal Cd/Ti molar ratio of 15%, the CdS/TNS composite exhibits the highest photocatalytic performance, which is approximately 5.4 times greater than that of pure TNS. The mechanism of the separation behavior of the photogenerated charges was also discussed.

Double polymer sheathed carbon nanotube supercapacitors show enhanced cycling stability

Science.gov (United States)

Zhao, Wenqi; Wang, Shanshan; Wang, Chunhui; Wu, Shiting; Xu, Wenjing; Zou, Mingchu; Ouyang, An; Cao, Anyuan; Li, Yibin

2015-12-01

Pseudo-materials are effective in boosting the specific capacitance of supercapacitors, but during service their degradation may also be very strong, causing reduced cycling stability. Here, we show that a carbon nanotube sponge grafted by two conventional pseudo-polymer layers in sequence can serve as a porous supercapacitor electrode with significantly enhanced cycling stability compared with single polymer grafting. Creating conformal polymer coatings on the nanotube surface and the resulting double-sheath configuration are important structural factors leading to the enhanced performance. Combining different polymers as double sheaths as reported here might be a potential route to circumvent the dilemma of pseudo-materials, and to simultaneously improve the capacitance and stability for various energy storage devices.Pseudo-materials are effective in boosting the specific capacitance of supercapacitors, but during service their degradation may also be very strong, causing reduced cycling stability. Here, we show that a carbon nanotube sponge grafted by two conventional pseudo-polymer layers in sequence can serve as a porous supercapacitor electrode with significantly enhanced cycling stability compared with single polymer grafting. Creating conformal polymer coatings on the nanotube surface and the resulting double-sheath configuration are important structural factors leading to the enhanced performance. Combining different polymers as double sheaths as reported here might be a potential route to circumvent the dilemma of pseudo-materials, and to simultaneously improve the capacitance and stability for various energy storage devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05978j

Effect of alkali and heat treatments for bioactivity of TiO{sub 2} nanotubes

Energy Technology Data Exchange (ETDEWEB)

Kim, Seo young, E-mail: mast6269@nate.com [Dept. of Dental Biomaterials and Institute of Bio degradable material, Institute of Oral Bioscience and BK21 plus project, School of Dentistry, Chonbuk National University, Jeonju, 561-756 (Korea, Republic of); Kim, Yu kyoung, E-mail: yk0830@naver.com [Dept. of Dental Biomaterials and Institute of Bio degradable material, Institute of Oral Bioscience and BK21 plus project, School of Dentistry, Chonbuk National University, Jeonju, 561-756 (Korea, Republic of); Park, Il song, E-mail: ilsong@jbnu.ac.kr [Division of Advanced Materials Engineering, Research Center for Advanced Materials Development and Institute of Biodegradable Materials, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Jin, Guang chun, E-mail: jingc88@126.com [Oral Medical College, Beihua University, Jilin City 132013 (China); Bae, Tae sung, E-mail: bts@jbnu.ac.kr [Dept. of Dental Biomaterials and Institute of Bio degradable material, Institute of Oral Bioscience and BK21 plus project, School of Dentistry, Chonbuk National University, Jeonju, 561-756 (Korea, Republic of); Lee, Min ho, E-mail: mh@jbnu.ac.kr [Dept. of Dental Biomaterials and Institute of Bio degradable material, Institute of Oral Bioscience and BK21 plus project, School of Dentistry, Chonbuk National University, Jeonju, 561-756 (Korea, Republic of)

2014-12-01

Highlights: • TiO{sub 2} nanotubes formed via anodization were treated by alkali and heat. • The surface roughness was increased after alkali treatment (p < 0.05). • After alkali and heat treatment, the wettability was better than before treatment. • Alkali treated TiO{sub 2} nanotubes were shown higher HAp formation in SBF. • Heat treatment affected on the attachment of cells for alkali treated nanotubes. - Abstract: In this study, for improving the bioactivity of titanium used as an implant material, alkali and heat treatments were carried out after formation of the nanotubes via anodization. Nanotubes with uniform length, diameter, and thickness were formed by anodization. The alkali and heat-treated TiO{sub 2} nanotubes were covered with the complex network structure, and the Na compound was generated on the surface of the specimens. In addition, after 5 and 10 days of immersion in the SBF, the crystallized OCP and HAp phase was significantly increased on the surface of the alkali-treated TiO{sub 2} nanotubes (PNA) and alkali and heat-treated TiO{sub 2} nanotubes (PNAH) groups. Cell proliferation was decreased due to the formation of amorphous sodium titanate (Na{sub 2}TiO{sub 3}) layer on the surface of the PNA group. However, anatase and crystalline sodium titanate were formed on the surface of the PNAH group after heat treatment at 550 °C, and cell proliferation was improved. Thus, PNA group had higher HAp forming ability in the simulated body fluid. Additional heat treatment affected on enhancement of the bioactivity and the attachment of osteoblasts for PNA group.

Plasma fluorination of vertically aligned carbon nanotubes: functionalization and thermal stability.

Science.gov (United States)

Struzzi, Claudia; Scardamaglia, Mattia; Hemberg, Axel; Petaccia, Luca; Colomer, Jean-François; Snyders, Rony; Bittencourt, Carla

2015-01-01

Grafting of fluorine species on carbon nanostructures has attracted interest due to the effective modification of physical and chemical properties of the starting materials. Various techniques have been employed to achieve a controlled fluorination yield; however, the effect of contaminants is rarely discussed, although they are often present. In the present work, the fluorination of vertically aligned multiwalled carbon nanotubes was performed using plasma treatment in a magnetron sputtering chamber with fluorine diluted in an argon atmosphere with an Ar/F2 ratio of 95:5. The effect of heavily diluted fluorine in the precursor gas mixture is investigated by evaluating the modifications in the nanotube structure and the electronic properties upon plasma treatment. The existence of oxygen-based grafted species is associated with background oxygen species present in the plasma chamber in addition to fluorine. The thermal stability and desorption process of the fluorine species grafted on the carbon nanotubes during the fluorine plasma treatment were evaluated by combining different spectroscopic techniques.

Plasma fluorination of vertically aligned carbon nanotubes: functionalization and thermal stability

Directory of Open Access Journals (Sweden)

Claudia Struzzi

2015-12-01

Full Text Available Grafting of fluorine species on carbon nanostructures has attracted interest due to the effective modification of physical and chemical properties of the starting materials. Various techniques have been employed to achieve a controlled fluorination yield; however, the effect of contaminants is rarely discussed, although they are often present. In the present work, the fluorination of vertically aligned multiwalled carbon nanotubes was performed using plasma treatment in a magnetron sputtering chamber with fluorine diluted in an argon atmosphere with an Ar/F2 ratio of 95:5. The effect of heavily diluted fluorine in the precursor gas mixture is investigated by evaluating the modifications in the nanotube structure and the electronic properties upon plasma treatment. The existence of oxygen-based grafted species is associated with background oxygen species present in the plasma chamber in addition to fluorine. The thermal stability and desorption process of the fluorine species grafted on the carbon nanotubes during the fluorine plasma treatment were evaluated by combining different spectroscopic techniques.

Integrated fast assembly of free-standing lithium titanate/carbon nanotube/cellulose nanofiber hybrid network film as flexible paper-electrode for lithium-ion batteries.

Science.gov (United States)

Cao, Shaomei; Feng, Xin; Song, Yuanyuan; Xue, Xin; Liu, Hongjiang; Miao, Miao; Fang, Jianhui; Shi, Liyi

2015-05-27

A free-standing lithium titanate (Li4Ti5O12)/carbon nanotube/cellulose nanofiber hybrid network film is successfully assembled by using a pressure-controlled aqueous extrusion process, which is highly efficient and easily to scale up from the perspective of disposable and recyclable device production. This hybrid network film used as a lithium-ion battery (LIB) electrode has a dual-layer structure consisting of Li4Ti5O12/carbon nanotube/cellulose nanofiber composites (hereinafter referred to as LTO/CNT/CNF), and carbon nanotube/cellulose nanofiber composites (hereinafter referred to as CNT/CNF). In the heterogeneous fibrous network of the hybrid film, CNF serves simultaneously as building skeleton and a biosourced binder, which substitutes traditional toxic solvents and synthetic polymer binders. Of importance here is that the CNT/CNF layer is used as a lightweight current collector to replace traditional heavy metal foils, which therefore reduces the total mass of the electrode while keeping the same areal loading of active materials. The free-standing network film with high flexibility is easy to handle, and has extremely good conductivity, up to 15.0 S cm(-1). The flexible paper-electrode for LIBs shows very good high rate cycling performance, and the specific charge/discharge capacity values are up to 142 mAh g(-1) even at a current rate of 10 C. On the basis of the mild condition and fast assembly process, a CNF template fulfills multiple functions in the fabrication of paper-electrode for LIBs, which would offer an ever increasing potential for high energy density, low cost, and environmentally friendly flexible electronics.

Pseudo and true visible light photocatalytic activity of nanotube titanic acid/graphene composites

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiaodong, E-mail: donguser@hotmail.com; Liu, Xiaogang; Xue, Xiaoxiao; Pan, Hui; Zhang, Min; Li, Qiuye; Yu, Laigui; Yang, Jianjun; Zhang, Zhijun [Henan University, Key Laboratory of Ministry of Education for Special Functional Materials (China)

2013-09-15

Nanotube titanic acid/graphene (NTA/Gr) composites were prepared by an easy hydrothermal treatment of graphene oxide (GO) and NTA in a mixed solvent of ethanol-water. As-prepared NTA/Gr composites and GO were characterized by means of Fourier transform infrared spectrometry, X-ray diffraction, diffuse-reflection spectrometry, thermal analysis, and transmission electron microscopy. Besides, the photocatalytic activities of as-prepared NTA/Gr composites were evaluated by monitoring the degradation of methyl orange (MO) under visible light irradiation. It has been found that extending hydrothermal reaction time (24 h instead of 3 h) leads to great changes in the morphology and crystal structure of as-prepared composites. Namely, the orthorhombic NTA (ca. 10 nm in diameter) in the composite transformed to anatase TiO{sub 2} particle (ca. 20-30 nm in diameter) while the Gr sheets (with micrometers-long wrinkles) in it transformed to a few Gr fragments (ca. 50 nm in diameter). Correspondingly, the NTA/Gr composite transformed to titanium dioxide/graphene (TiO{sub 2}/Gr) composite. In the meantime, pure GO only has adsorption effect but it has no photocatalytic activity in the visible light region. Nevertheless, increasing Gr ratio results in enhanced visible light absorption capability and photocatalytic activity of NTA/Gr composites as well as the TiO{sub 2}/Gr composites. This demonstrates that the true visible light photocatalytic activity of NTA/Gr composites as well as the TiO{sub 2}/Gr composites for the degradation of MO is not as excellent as expected, and their high apparent activity is attributed to the strong adsorption of MO on the composites.

Pseudo and true visible light photocatalytic activity of nanotube titanic acid/graphene composites

Science.gov (United States)

Wang, Xiaodong; Liu, Xiaogang; Xue, Xiaoxiao; Pan, Hui; Zhang, Min; Li, Qiuye; Yu, Laigui; Yang, Jianjun; Zhang, Zhijun

2013-09-01

Nanotube titanic acid/graphene (NTA/Gr) composites were prepared by an easy hydrothermal treatment of graphene oxide (GO) and NTA in a mixed solvent of ethanol-water. As-prepared NTA/Gr composites and GO were characterized by means of Fourier transform infrared spectrometry, X-ray diffraction, diffuse-reflection spectrometry, thermal analysis, and transmission electron microscopy. Besides, the photocatalytic activities of as-prepared NTA/Gr composites were evaluated by monitoring the degradation of methyl orange (MO) under visible light irradiation. It has been found that extending hydrothermal reaction time (24 h instead of 3 h) leads to great changes in the morphology and crystal structure of as-prepared composites. Namely, the orthorhombic NTA (ca. 10 nm in diameter) in the composite transformed to anatase TiO2 particle (ca. 20-30 nm in diameter) while the Gr sheets (with micrometers-long wrinkles) in it transformed to a few Gr fragments (ca. 50 nm in diameter). Correspondingly, the NTA/Gr composite transformed to titanium dioxide/graphene (TiO2/Gr) composite. In the meantime, pure GO only has adsorption effect but it has no photocatalytic activity in the visible light region. Nevertheless, increasing Gr ratio results in enhanced visible light absorption capability and photocatalytic activity of NTA/Gr composites as well as the TiO2/Gr composites. This demonstrates that the true visible light photocatalytic activity of NTA/Gr composites as well as the TiO2/Gr composites for the degradation of MO is not as excellent as expected, and their high apparent activity is attributed to the strong adsorption of MO on the composites.

A promising lightweight multicomponent microwave absorber based on doped barium hexaferrite/calcium titanate/multiwalled carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Afghahi, Seyyed Salman Seyyed [Imam Hossein University, Department of Materials Science and Engineering (Iran, Islamic Republic of); Jafarian, Mojtaba, E-mail: m.jafarian@srbiau.ac.ir [Islamic Azad University, Young Researchers and Elite Club, Science and Research Branch (Iran, Islamic Republic of); Atassi, Yomen [Higher Institute for Applied Sciences and Technology, Department of Applied Physics (Syrian Arab Republic)

2016-07-15

We present the design of a microwave absorber in the X band based on ternary nanocomposite of doped barium hexaferrite (Ba-M)/calcium titanate (CTO)/multiwall carbon nanotubes (MWCNTs) in epoxy matrix. The hydrothermal method has been used to synthesize Ba-M and CTO nanopowder. The phase identification has been investigated using XRD patterns. Scanning electron microscope, transmission electron microscope, vibrating sample magnetometer, and vector network analyzer are used to analyze the morphology of the different components and the magnetic, electromagnetic, and microwave absorption properties of the final composite absorbers, respectively. As far as we know, the design of this type of multicomponent microwave absorber has not been investigated before. The results reveal that the combination of these three components with their different loss mechanisms has a synergistic effect that enhances the attenuation properties of the final composite. The absorber of only 2.5-mm thickness and 35 wt% of loading ratio exhibits a minimum reflection loss of −43 dB at 10.2 GHz with a bandwidth of 3.6 GHz, while the corresponding absorber based on pure (Ba-M) shows a minimum reflection loss of −34 dB at 9.8 GHz with a bandwidth of 0.256 GHz and a thickness of 4 mm.Graphical Abstract.

Titan!

Science.gov (United States)

Matson, Dennis L.

2010-05-01

Cassini-Huygens achieved Saturnian orbit on July 1, 2004. The first order of business was the safe delivery of the Huygens atmospheric probe to Titan that took place on January 14, 2005. Huygens descended under parachute obtaining observations all the way down to a safe landing. It revealed Titan for the first time. Stunning are the similarities between Titan and the Earth. Viewing the lakes and seas, the fluvial terrain, the sand dunes and other features through the hazy, nitrogen atmosphere, brings to mind the geological processes that created analogous features on the Earth. On Titan frozen water plays the geological role of rock; liquid methane takes the role of terrestrial water. The atmospheres of both Earth and Titan are predominately nitrogen gas. Titan's atmosphere contains 1.5% methane and no oxygen. The surface pressure on Titan is 1.5 times the Earth's. There are aerosol layers and clouds that come and go. Now, as Saturn proceeds along its solar orbit, the seasons are changing. The effects upon the transport of methane are starting to be seen. A large lake in the South Polar Region seems to be filling more as winter onsets. Will the size and number of the lakes in the South grow during winter? Will the northern lakes and seas diminish or dry up as northern summer progresses? How will the atmospheric circulation change? Much work remains not only for Cassini but also for future missions. Titan has many different environments to explore. These require more capable instruments and in situ probes. This work was conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration.

Tribological and mechanical investigation of acrylic-based nanocomposite coatings reinforced with PMMA-grafted-MWCNT

Energy Technology Data Exchange (ETDEWEB)

Al-Kawaz, A. [UPR22/CNRS, Institut Charles Sadron, Université de Strasbourg, 23 Rue du Loess, BP 84047, F-67034 Strasbourg Cedex 2 (France); Rubin, A., E-mail: anne.rubin@ics-cnrs.unistra.fr [UPR22/CNRS, Institut Charles Sadron, Université de Strasbourg, 23 Rue du Loess, BP 84047, F-67034 Strasbourg Cedex 2 (France); Badi, N.; Blanck, C.; Jacomine, L. [UPR22/CNRS, Institut Charles Sadron, Université de Strasbourg, 23 Rue du Loess, BP 84047, F-67034 Strasbourg Cedex 2 (France); Janowska, I.; Pham-Huu, C. [Institute of Chemistry and Processes for Energy, Environment and Health (UMR 7515) CNRS - University of Strasbourg, 25 Rue Becquerel Strasbourg, 67087 Cedex 08 (France); Gauthier, C. [UPR22/CNRS, Institut Charles Sadron, Université de Strasbourg, 23 Rue du Loess, BP 84047, F-67034 Strasbourg Cedex 2 (France)

2016-06-01

The chemical functionalization of carbon nanotubes (CNTs) could improve their chemical compatibility. Poly(methyl methacrylate) (PMMA)-functionalized multi-walled carbon nanotubes (MWCNTs) are prepared by in situ atom transfer radical polymerization (ATRP) using a “grafting from” approach. It allows the control of the thickness of the polymer layer grafted on MWCNTs from two parameters: the feed ratio of MMA to MWCNT, the volume fraction of solvent to MMA. This work compared the effect of several PMMA-grafted-MWNCT fillers embedded into a PMMA matrix, PMMA-grafted-MWCNT/PMMA, and obtained by solution mixing technique. We studied the tribological performances of 20 μm coatings of these nanocomposites deposited on neat PMMA. The percentage of embedded fillers is kept low to maintain the transparency of the PMMA. The coefficient of friction was found to relatively decrease with the increase of the weight fraction of polymer grafted to the surface of MWCNT. Moreover the elastic modulus also increased with increasing the weight fraction of PMMA coated MWCNT. - Highlights: • Synthesis of MWCNT-PMMA nanoparticles by ATRP “grafting from” approach. • PMMA-grafted-MWCNT/PMMA coatings with good mechanical properties. • High tribological performance of PMMA-grafted-MWCNT/PMMA coatings.

Application of Response Surface Methodology for Optimization of Urea Grafted Multiwalled Carbon Nanotubes in Enhancing Nitrogen Use Efficiency and Nitrogen Uptake by Paddy Plants

Directory of Open Access Journals (Sweden)

Norazlina Mohamad Yatim

2016-01-01

Full Text Available Efficient use of urea fertilizer (UF as important nitrogen (N source in the world’s rice production has been a concern. Carbon-based materials developed to improve UF performance still represent a great challenge to be formulated for plant nutrition. Advanced N nanocarrier is developed based on functionalized multiwall carbon nanotubes (f-MWCNTs grafted with UF to produce urea-multiwall carbon nanotubes (UF-MWCNTs for enhancing the nitrogen uptake (NU and use efficiency (NUE. The grafted N can be absorbed and utilized by rice efficiently to overcome the N loss from soil-plant systems. The individual and interaction effect between the specified factors of f-MWCNTs amount (0.10–0.60 wt% and functionalization reflux time (12–24 hrs with the corresponding responses (NUE, NU were structured via the Response Surface Methodology (RSM based on five-level CCD. The UF-MWCNTs with optimized 0.5 wt% f-MWCNTs treated at 21 hrs reflux time achieve tremendous NUE up to 96% and NU at 1180 mg/pot. Significant model terms (p value < 0.05 for NUE and NU responses were confirmed by the ANOVA. Homogeneous dispersion of UF-MWCNTs was observed via FESEM and TEM. The chemical changes were monitored by FT-IR and Raman spectroscopy. Hence, this UF-MWCNTs’ approach provides a promising strategy in enhancing plant nutrition for rice.

Photoelectrochemical Properties of FeO Supported on TiO2-Based Thin Films Converted from Self-Assembled Hydrogen Titanate Nanotube Powders

Directory of Open Access Journals (Sweden)

Kyung-Jong Noh

2012-01-01

Full Text Available A photoanode was fabricated using hematite (α-Fe2O3 nanoparticles which had been held in a thin film of hydrogen titanate nanotubes (H-TiNT, synthesized by repetitive self-assembling method on FTO (fluorine-doped tin oxide glass, which were incorporated via dipping process in aqueous Fe(NO33 solution. Current voltage (I-V electrochemical properties of the photoanode heat-treated at 500°C for 10 min in air were evaluated under ultraviolet-visible light irradiation. Microstructure and crystallinity changes were also investigated. The prepared Fe2O3/H-TiNT/FTO composite thin film exhibited about threefold as much photocurrent as the Fe2O3/FTO film. The improvement in photocurrent was considered to be caused by reduced recombination of electrons and holes, with an appropriate amount of Fe2O3 spherical nanoparticles supported on the H-TiNT/FTO film. Nanosized spherical Fe2O3 particles with about 65 wt% on the H-TiNT/FTO film showed best performance in our study.

Adsorption and desorption of Cd(II) onto titanate nanotubes and efficient regeneration of tubular structures

International Nuclear Information System (INIS)

Wang, Ting; Liu, Wen; Xu, Nan; Ni, Jinren

2013-01-01

Highlights: ► Satisfactory reuse of TNTs due to easy regeneration of tubular structures. ► TNTs regeneration using only 2% of NaOH needed for virgin TNTs preparation. ► Excellent regeneration attributed to steady TNTs skeleton and complex form of TNTs-OCd + OH − onto adsorbed TNTs. -- Abstract: Efficient regeneration of desorbed titanate nanotubes (TNTs) was investigated with cycled Cd(II) adsorption and desorption processes. After desorption of Cd (II) from TNTs using 0.1 M HNO 3 , regeneration could be simply achieved with only 0.2 M NaOH at ambient temperature, i.e. 2% of the NaOH needed for virgin TNTs preparation at 130 °C. The regenerated TNTs displayed similar adsorption capacity of Cd(II) even after six recycles, while significant reduction could be detected for desorbed TNTs without regeneration. The virgin TNTs, absorbed TNTs, desorbed TNTs and regenerated TNTs were systematically characterized. As results, the ion-exchange mechanism with Na + in TNTs was convinced with obvious change of -TiO(ONa) 2 by FTIR spectroscopy. The easy recovery of the damaged tubular structures proved by TEM and XRD was ascribed to asymmetric distribution of H + and Na + on the surface side and interlayer region of TNTs. More importantly, the cost-effective regeneration was found possibly related to complex form of TNTs-OCd + OH − onto the adsorbed TNTs, which was identified with help of X-ray photoelectron spectroscopy, and further indicated due to high relevance to an unexpected mole ratio of 1:1 between exchanged Na + and absorbed Cd(II)

BisGMA-polyvinylpyrrolidone blend based nanocomposites reinforced with chitosan grafted f-multiwalled carbon nanotubes

Directory of Open Access Journals (Sweden)

A. Praharaj

2015-01-01

Full Text Available In this work, initially a non-destroyable surface grafting of acid functionalized multiwalled carbon nanotubes (f-MWCNTs with biopolymer chitosan (CS was carried out using glutaraldehyde as a cross-linking agent via the controlled covalent deposition method which was characterized by Fourier transform infrared spectroscopy (FTIR and scanning electron microscopy (SEM. Then, BisGMA (bisphenol-A glycidyldimethacrylate-polyvinylpyrrolidone (PVP blend was prepared (50:50 wt% by a simple sonication method. The CS grafted f-MWCNTs (CS/f-MWCNTs were finally dispersed in BisGMA-PVP blend (BGP50 system in different compositions i.e. 0, 2, 5 and 7 wt% and pressed into molds for the fabrication of reinforced nanocomposites which were characterized by SEM. Nanocomposites reinforced with 2 wt% raw MWCNTs and acid f-MWCNTs were also fabricated and their properties were studied in detail. The results of comparative study report lower values of the investigated properties in nanocomposites with 2 wt% raw and f-MWCNTs than the one with 2 wt% CS/f-MWCNTs proving it to be a better reinforcing nanofiller. Further, the mechanical behavior of the nanocomposites with various CS/f-MWCNTs content showed a dramatic increase in Young’s Modulus, tensile strength, impact strength and hardness along with improved dynamic mechanical, thermal and electrical properties at 5 wt% content of CS/f-MWCNTs. The addition of CS/f-MWCNTs also resulted in reduced corrosion and swelling properties. Thus, the fabricated nanocomposites with optimum nanofiller content could serve as low cost and light weight structural, thermal and electrical materials compatible in various corrosive and solvent based environments.

Preparation of functionalized carbon nanotubes using radiation technique

International Nuclear Information System (INIS)

Chen Shimou; Wu Guozhong; Huang Shirong; Zhu Guanglai

2006-01-01

Carbon nanotubes (CNTs) have attracted great interest because of their unique structural, electronic, mechanical, and optical properties. However, the studies and applications of CNTs are hindered by processing and manipulation difficulties owing to their insolubility or poor dispersion in common solvents and polymeric matrixes. To facilitate their applications, many approaches were employed to functionalize CNTs with functional groups, either noncovalently or covalently. In our study, radiation technique was utilized to produce functionalized CNTs. In a typical experiment, multiwalled carbon nanotubes (MWNTs) were irradiated in potassium persulfate aqueous solution. Persulfnic group can react with hydrated electrons to produce sulfuric acid radicals, which can attack the c=c on the surface of tubes to form sulfonated MWNTs. On the other hand, grafting polymer (instead of low-molecular-weight compound) onto CNTs by an appropriate method is a possible strategy for preparing the nanotubes with little damage in structure and high solubility in solvent. A facile strategy to prepare water soluble MWNTs in large scale by two steps of gamma irradiation has been developed at SINAP. The first step is to irradiate MWNTs in ethanol. The radiolysis of ethanol produced many active species such as . CH 2 CH 2 OH, CH 3 . CHCH 2 OH, which react with C=C of MWNTs and attach onto the surface of MWNTs. Then, poly(acrylic acid) was covalently grafted to the surface of MWNTs by irradiating the samples in the presence of acrylic acid. The PAA-grafted MWNTs have good solubility in water and other polar solvents. This two-step grafting approach may also be of help for introducing other functional polymer chains onto MWNTs. (authors)

Synthesis of hydrophilic carbon nanotubes by grafting poly(methyl methacrylate) via click reaction and its effect on poly(vinylidene fluoride)-carbon nanotube composite membrane properties1

Science.gov (United States)

Ma, Wenzhong; Zhao, Yuchen; Li, Yuxue; Zhang, Peng; Cao, Zheng; Yang, Haicun; Liu, Chunlin; Tao, Guoliang; Gong, Fanghong; Matsuyama, Hideto

2018-03-01

Surface modification of azide-decorated multiwalled carbon nanotubes (MWCNTs) with well-defined alkyne-terminated poly(methyl methacrylate) (PMMA) chains was accomplished via the combination of reversible addition fragmentation chain transfer (RAFT) and "click" chemistry. Successful attachment of PMMA onto MWCNT was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), gel permeation chromatography, Raman spectroscopy, and transmission electron microscopy. The highest grafting percentage (GP) of the PMMA chains (GP = 23.3%) was calculated using TGA. The effect of the PMMA-grafted-MWCNTs (MWCNTs-g-PMMA) content on the performance of the poly(vinylidene fluoride) (PVDF)-MWCNTs-g-PMMA composite membrane was studied. The MWCNTs-g-PMMA was found to be well dispersed in the PVDF composite membrane matrix because of the excellent compatibility between the PMMA and PVDF chains. The composite membranes showed improved porosity, hydrophilicity, water flux, β-PVDF content, and mechanical properties at an optimal amount of 2 wt% MWCNTs-g-PMMA incorporated in the PVDF membrane matrix. In contrast, the hydroxyl functionalized MWCNTs (MWCNTs-OH) showed limited enhancement in the water flux and mechanical strength, which is mainly due to the poor dispersion of MWCNT because of the weak interaction between the MWCNT and PVDF chains. This study reveals the excellent prospect of the MWCNT-based ultrafiltration membrane with enhanced properties in water treatment applications.

Role of solution chemistry on the trapping of radionuclide Th(IV) using titanate nanotubes as an efficient adsorbent

International Nuclear Information System (INIS)

Guodong Sheng; Chinese Academy of Sciences, Hefei; Baowei Hu

2013-01-01

Titanate nanotubes (TNTs) have attracted great interest in multidisciplinary study since their discovery. The adsorption of thorium [Th(IV)] onto TNTs in the absence and presence of humic acid (HA)/fulvic acid (FA) was studied by batch technique. The influence of pH from 2.0 to 10.0, ionic strength from 0.001 to 0.1 mol L -1 NaClO 4 , and coexisting electrolyte cations (Li + , Na + , K + ) and anions (ClO 4 - , NO 3 - , Cl - ) on the adsorption of Th(IV) onto TNTs was tested. The adsorption isotherms of Th(IV) was determined at pH 3.0 and analyzed with Langmuir and Freundlich adsorption models, respectively. The results demonstrated that the adsorption of Th(IV) onto TNTs increases steeply with increasing pH from 2.0 to 4.0. Generally, HA/FA was showed to enhance Th(IV) adsorption onto TNTs at low pH values, but to reduce Th(IV) adsorption onto TNTs at high pH values. The adsorption of Th(IV) onto TNTs was also dependent on coexisting electrolyte ions in aqueous solution under our experimental conditions. The adsorption of Th(IV) onto TNTs is exothermic and spontaneous. The findings indicating that TNTs can be used as a promising candidate for the enrichment and solidification of Th(IV) or its analogue actinides from large volume solution in real work. (author)

Chemi- vs physisorption in the radical functionalization of single-walled carbon nanotubes under microwaves

Directory of Open Access Journals (Sweden)

Victor Mamane

2014-04-01

Full Text Available The effect of microwaves on the functionalization of single-walled carbon nanotubes (SWNTs by the diazonium method was studied. The usage of a new approach led to the identification of the strength of the interaction (physical or chemical between the functional groups and the carbon nanotube surface. Moreover, the nature (chemical formula of the adsorbed/grafted functional groups was determined. According to thermogravimetric analysis coupled with mass spectrometry and Raman spectroscopy, the optimal functionalization level was reached after 5 min of reaction. Prolonged reaction times can lead to undesired reactions such as defunctionalization, solvent addition and polymerization of the grafted functions. The strength (chemi- vs physisorption of the bonds between the grafted functional groups and the SWNTs is discussed showing the occurrence of physical adsorption as a consequence of defunctionalization after 15 min of reaction under microwaves. Several chemical mechanisms of grafting could be identified, and it was possible to distinguish conditions leading to the desired chemical grafting from those leading to undesired reactions such as physisorption and polymerization.

Enhanced durability of carbon nanotube grafted hierarchical ceramic microfiber-reinforced epoxy composites.

Science.gov (United States)

Krishnamurthy, Ajay; Hunston, Donald L; Forster, Amanda L; Natarajan, Bharath; Liotta, Andrew H; Wicks, Sunny S; Stutzman, Paul E; Wardle, Brian L; Liddle, J Alexander; Forster, Aaron M

2017-12-01

As carbon nanotube (CNT) infused hybrid composites are increasingly identified as next-generation aerospace materials, it is vital to evaluate their long-term structural performance under aging environments. In this work, the durability of hierarchical, aligned CNT grafted aluminoborosilicate microfiber-epoxy composites (CNT composites) are compared against baseline aluminoborosilicate composites (baseline composites), before and after immersion in water at 25 °C (hydro) and 60 °C (hydrothermal), for extended durations (90 d and 180 d). The addition of CNTs is found to reduce water diffusivities by approximately 1.5 times. The mechanical properties (bending strength and modulus) and the damage sensing capabilities (DC conductivity) of CNT composites remain intact regardless of exposure conditions. The baseline composites show significant loss of strength (44 %) after only 15 d of hydrothermal aging. This loss of mechanical strength is attributed to fiber-polymer interfacial debonding caused by accumulation of water at high temperatures. In situ acoustic and DC electrical measurements of hydrothermally aged CNT composites identify extensive stress-relieving micro-cracking and crack deflections that are absent in the aged baseline composites. These observations are supported by SEM images of the failed composite cross-sections that highlight secondary matrix toughening mechanisms in the form of CNT pullouts and fractures which enhance the service life of composites and maintain their properties under accelerated aging environments.

Direct chemical grafted curcumin on halloysite nanotubes as dual-responsive prodrug for pharmacological applications.

Science.gov (United States)

Massaro, M; Amorati, R; Cavallaro, G; Guernelli, S; Lazzara, G; Milioto, S; Noto, R; Poma, P; Riela, S

2016-04-01

Covalently functionalized halloysite nanotubes (HNTs) were successfully employed as dual-responsive nanocarriers for curcumin (Cur). Particularly, we synthesized HNT-Cur prodrug with a controlled curcumin release on dependence of both intracellular glutathione (GSH) and pH conditions. In order to obtain HNT-Cur produgs, halloysite was firstly functionalized with cysteamine through disulphide linkage. Afterwards, curcumin molecules were chemically conjugated to the amino end groups of halloysite via Schiff's base formation. The successful functionalization of halloysite was proved by thermogravimetric analysis, FT-IR spectroscopy, dynamic light scattering and scanning electron microscopy. Experimental data confirmed the presence of curcumin on HNT external surface. Moreover, we investigated the kinetics of curcumin release by UV-vis spectroscopy, which highlighted that HNT-Cur prodrug possesses dual stimuli-responsive ability upon exposure to GSH-rich or acidic environment. In vitro antiproliferative and antioxidant properties of HNT-Cur prodrug were studied with the aim to explore their potential applications in pharmaceutics. This work puts forward an efficient strategy to prepare halloysite based nanocarriers with controlled drug delivery capacity through direct chemical grafting with stimuli-responsive linkage. Copyright © 2016 Elsevier B.V. All rights reserved.

Functionalization of vertically aligned carbon nanotubes

Directory of Open Access Journals (Sweden)

Eloise Van Hooijdonk

2013-02-01

Full Text Available This review focuses and summarizes recent studies on the functionalization of carbon nanotubes oriented perpendicularly to their substrate, so-called vertically aligned carbon nanotubes (VA-CNTs. The intrinsic properties of individual nanotubes make the VA-CNTs ideal candidates for integration in a wide range of devices, and many potential applications have been envisaged. These applications can benefit from the unidirectional alignment of the nanotubes, the large surface area, the high carbon purity, the outstanding electrical conductivity, and the uniformly long length. However, practical uses of VA-CNTs are limited by their surface characteristics, which must be often modified in order to meet the specificity of each particular application. The proposed approaches are based on the chemical modifications of the surface by functionalization (grafting of functional chemical groups, decoration with metal particles or wrapping of polymers to bring new properties or to improve the interactions between the VA-CNTs and their environment while maintaining the alignment of CNTs.

Functionalization of vertically aligned carbon nanotubes.

Science.gov (United States)

Van Hooijdonk, Eloise; Bittencourt, Carla; Snyders, Rony; Colomer, Jean-François

2013-01-01

This review focuses and summarizes recent studies on the functionalization of carbon nanotubes oriented perpendicularly to their substrate, so-called vertically aligned carbon nanotubes (VA-CNTs). The intrinsic properties of individual nanotubes make the VA-CNTs ideal candidates for integration in a wide range of devices, and many potential applications have been envisaged. These applications can benefit from the unidirectional alignment of the nanotubes, the large surface area, the high carbon purity, the outstanding electrical conductivity, and the uniformly long length. However, practical uses of VA-CNTs are limited by their surface characteristics, which must be often modified in order to meet the specificity of each particular application. The proposed approaches are based on the chemical modifications of the surface by functionalization (grafting of functional chemical groups, decoration with metal particles or wrapping of polymers) to bring new properties or to improve the interactions between the VA-CNTs and their environment while maintaining the alignment of CNTs.

Water-soluble polyelectrolyte-grafted multiwalled carbon nanotube thin films for efficient counter electrode of dye-sensitized solar cells.

Science.gov (United States)

Han, Jinkyu; Kim, Hyunju; Kim, Dong Young; Jo, Seong Mu; Jang, Sung-Yeon

2010-06-22

Water-soluble, polyelectrolyte-grafted multiwalled carbon nanotubes (MWCNTs), MWCNT-g-PSSNa, were synthesized using a "grafting to" route. MWCNT-g-PSSNa thin films fabricated by an electrostatic spray (e-spray) technique were used as the counter electrode (CE) for dye-sensitized solar cells (DSSCs). The e-sprayed MWCNT-g-PSSNa thin-film-based CEs (MWCNT-CE) were uniform over a large area, and the well-exfoliated MWCNTs formed highly interconnected network structures. The electrochemical catalytic activity of the MWCNT-CE at different thicknesses was investigated. The MWCNT-g-PSSNa thin film showed high efficiency as a CE in DSSCs. The power conversion efficiency (PCE) of the DSSCs using the MWCNT-g-PSSNa thin-film-based CE (DSSC-MWCNT) was >6% at a CE film thickness of approximately 0.3 microm. The optimum PCE was >7% at a film thickness of approximately 1 microm, which is 20-50 times thinner than conventional carbon-based CE. The charge transfer resistance at the MWCNT-CE/electrolyte interface was 1.52 Omega cm(2) at a MWCNT-CE thickness of 0.31 microm, which is lower than that of a Pt-CE/electrolyte interface, 1.78 Omega cm(2). This highlights the potential for the low-cost CE fabrication of DSSCs using a facile deposition technique from an environmentally "friendly" solution at low temperatures.

Tailoring the Electrochemical Properties of Carbon Nanotube Modified Indium Tin Oxide via in Situ Grafting of Aryl Diazonium.

Science.gov (United States)

Hicks, Jacqueline M; Wong, Zhi Yi; Scurr, David J; Silman, Nigel; Jackson, Simon K; Mendes, Paula M; Aylott, Jonathan W; Rawson, Frankie J

2017-05-23

Our ability to tailor the electronic properties of surfaces by nanomodification is paramount for various applications, including development of sensing, fuel cell, and solar technologies. Moreover, in order to improve the rational design of conducting surfaces, an improved understanding of structure/function relationships of nanomodifications and effect they have on the underlying electronic properties is required. Herein, we report on the tuning and optimization of the electrochemical properties of indium tin oxide (ITO) functionalized with single-walled carbon nanotubes (SWCNTs). This was achieved by controlling in situ grafting of aryl amine diazonium films on the nanoscale which were used to covalently tether SWCNTs. The structure/function relationship of these nanomodifications on the electronic properties of ITO was elucidated via time-of-flight secondary ion mass spectrometry and electrochemical and physical characterization techniques which has led to new mechanistic insights into the in situ grafting of diazonium. We discovered that the connecting bond is a nitro group which is covalently linked to a carbon on the aryl amine. The increased understanding of the surface chemistry gained through these studies enabled us to fabricate surfaces with optimized electron transfer kinetics. The knowledge gained from these studies allows for the rational design and tuning of the electronic properties of ITO-based conducting surfaces important for development of various electronic applications.

A novel method of synthesizing cyclodextrin grafted multiwall carbon nanotubes/iron oxides and its adsorption of organic pollutant

Energy Technology Data Exchange (ETDEWEB)

Liu, Wei; Jiang, Xinyu [School of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Chen, Xiaoqing, E-mail: xqchen@csu.edu.cn [School of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Collaborative Innovation Center of Resource-conserving and Environment-friendly Society and Ecological Civilization (China)

2014-11-30

Highlights: • A cost-effective and one-step method for grafting cyclodextrin onto magnetic material. • Relatively good separation and regeneration properties as adsorbent. • The adsorption capacities are comparable with other adsorbents reported previously. - Abstract: A novel methodology for the synthesis of the multiwalled carbon nanotubes/iron oxides modified by β-cyclodextrin (denoted as MWCNTs/iron oxides/β-CD) was proposed using 1,6-diisocyanatohexane as cross-linker in N,N-dimethyl formamide, which avoided complex steps in the link of β-cyclodextrin and MWCNTs/iron oxides via conventional synthetic methods. The characteristic results of Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and thermogravimetric analysis (TGA) showed that β-CD was grafted onto the MWCNTs/iron oxides successfully. In addition, vibrating sample magnetometer (VSM) and magnetic separation experiment suggested that the prepared composite exhibited preferable magnetic property and good dispersion property in aqueous solution. The effects of contact time, initial adsorbent content, solution pH and temperature on the adsorption of p-nitrophenol (PNP) were studied systematically. The adsorption kinetics and equilibrium isotherms data fitted well with pseudo-second-order kinetic equation and Langmuir isotherm model, respectively. Furthermore, the adsorption-desorption experiment of PNP demonstrated that MWCNTs/iron oxides/β-CD is a cost-effective material with high regeneration efficiency.

Multiple functionalization of multi-walled carbon nanotubes with carboxyl and amino groups

Energy Technology Data Exchange (ETDEWEB)

Zhao, Zhiyuan [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Yang, Zhanhong, E-mail: zhongnan320@gmail.com [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Key Laboratory of Resource Chemistry of Nonferrous Metals, Ministry of Education, Central South University, Changsha 410083 (China); Hu, Youwang; Li, Jianping [College of Mechanical and Electrical Engineering, Central South University, Changsha 410083 (China); Fan, Xinming [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China)

2013-07-01

In this paper, carboxyl and amino groups have been introduced onto the surface of the multi-walled carbon nanotubes (MWCNTs) by the mixed acid treatment and the diazonium reaction, respectively. The presence of multifunctionality groups on the MWCNTs has been characterized by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric (TGA) analysis, Raman spectra, scanning electron microscopy (SEM) and energy dispersive X-ray spectrum (EDS). The multifunctionalized carbon nanotubes were further utilized to react with acetyl chloride and ethylenediamine (EDA). The formation of the amide bond in the grafting reaction has been confirmed by FT-IR spectroscopy. The result indicates that the further grafting is successful. The multifunctionalized MWCNTs can be a new versatile platform for many interesting applications.

Functionalization of Carbon Nanotubes via Electrophilic Substitution Reaction in Polyphosphoric Acid

National Research Council Canada - National Science Library

Baek, Jong-Beom

2006-01-01

.... Furthermore, on the basis of all supportive evidences, this work provides one of the most efficient methods to directly and uniformly grafting the surfaces of carbon nanotubes (CNT) and nanofibers (CNF...

Barium titanate coated with magnesium titanate via fused salt method and its dielectric property

International Nuclear Information System (INIS)

Chen Renzheng; Cui Aili; Wang Xiaohui; Li Longtu

2003-01-01

Barium titanate fine particles were coated homogeneously with magnesium titanate via the fused salt method. The thickness of the magnesium titanate film is 20 nm, as verified by TEM and XRD. The mechanism of the coating is that: when magnesium chloride is liquated in 800 deg. C, magnesium will replace barium in barium titanate, and form magnesium titanate film on the surface of barium titanate particles. Ceramics sintered from the coated particles show improved high frequency ability. The dielectric constant is about 130 at the frequency from 1 to 800 MHz

Schiff base-chitosan grafted multiwalled carbon nanotubes as a novel solid-phase extraction adsorbent for determination of heavy metal by ICP-MS

Energy Technology Data Exchange (ETDEWEB)

Dai, Bingye; Cao, Meirong; Fang, Guozhen; Liu, Bing; Dong, Xv; Pan, Mingfei [Key Laboratory of Food Nutrition and Safety, Ministry of Education, Tianjin Key Laboratory of Food Nutrition and Safety, Tianjin University of Science and Technology, Tianjin 300457 (China); Wang, Shuo, E-mail: elisasw2002@yahoo.com.cn [Key Laboratory of Food Nutrition and Safety, Ministry of Education, Tianjin Key Laboratory of Food Nutrition and Safety, Tianjin University of Science and Technology, Tianjin 300457 (China)

2012-06-15

Highlights: Black-Right-Pointing-Pointer Schiff base-chitosan grafted MWCNTs were synthesized via covalent modification. Black-Right-Pointing-Pointer The S-CS-MWCNTs were successfully characterized by FT-IR, TEM and TGA. Black-Right-Pointing-Pointer The S-CS-MWCNTs were used for solid-phase extraction of metal ions. Black-Right-Pointing-Pointer A method was developed detection of metal ions from samples coupled with ICP-MS. - Abstract: A novel Schiff base-chitosan-grafted multiwalled carbon nanotubes (S-CS-MWCNTs) solid-phase extraction adsorbent was synthesized by covalently grafting a Schiff base-chitosan (S-CS) onto the surfaces of oxidized MWCNTs. The adsorbent was characterized by Fourier-transform infrared spectroscopy, transmission electron microscopy, and thermal gravimetric analysis. The results showed that S-CS was successfully grafted onto the surfaces of MWCNTs. A method was developed for the determination of heavy metals, namely V(V), Cr(VI), Cu(II), As(V) and Pb(II) in biological and environmental samples by inductively coupled plasma mass spectrometry coupled with preconcentration with S-CS-MWCNTs. The parameters influencing preconcentration of target ions, such as the pH of the sample solution, the flow rate of sample loading, the eluent concentration, and eluent volume, were investigated and optimized. Under the optimal conditions, the enrichment factors of V(V), Cr(VI), Cu(II), As(V), and Pb(II) reached 111, 95, 60, 52, and 128, respectively, and the detection limits were as low as 1.3-3.8 ng L{sup -1}. The developed method was successfully applied to the determination of trace-metal ions in herring, spinach, river water, and tap water with good recoveries ranging from 91.0% to 105.0%.

Schiff base-chitosan grafted multiwalled carbon nanotubes as a novel solid-phase extraction adsorbent for determination of heavy metal by ICP-MS

International Nuclear Information System (INIS)

Dai, Bingye; Cao, Meirong; Fang, Guozhen; Liu, Bing; Dong, Xv; Pan, Mingfei; Wang, Shuo

2012-01-01

Highlights: ► Schiff base-chitosan grafted MWCNTs were synthesized via covalent modification. ► The S-CS-MWCNTs were successfully characterized by FT-IR, TEM and TGA. ► The S-CS-MWCNTs were used for solid-phase extraction of metal ions. ► A method was developed detection of metal ions from samples coupled with ICP-MS. - Abstract: A novel Schiff base-chitosan-grafted multiwalled carbon nanotubes (S-CS-MWCNTs) solid-phase extraction adsorbent was synthesized by covalently grafting a Schiff base-chitosan (S-CS) onto the surfaces of oxidized MWCNTs. The adsorbent was characterized by Fourier-transform infrared spectroscopy, transmission electron microscopy, and thermal gravimetric analysis. The results showed that S-CS was successfully grafted onto the surfaces of MWCNTs. A method was developed for the determination of heavy metals, namely V(V), Cr(VI), Cu(II), As(V) and Pb(II) in biological and environmental samples by inductively coupled plasma mass spectrometry coupled with preconcentration with S-CS-MWCNTs. The parameters influencing preconcentration of target ions, such as the pH of the sample solution, the flow rate of sample loading, the eluent concentration, and eluent volume, were investigated and optimized. Under the optimal conditions, the enrichment factors of V(V), Cr(VI), Cu(II), As(V), and Pb(II) reached 111, 95, 60, 52, and 128, respectively, and the detection limits were as low as 1.3–3.8 ng L −1 . The developed method was successfully applied to the determination of trace-metal ions in herring, spinach, river water, and tap water with good recoveries ranging from 91.0% to 105.0%.

Titan's Radioactive Haze : Production and Fate of Radiocarbon On Titan

Science.gov (United States)

Lorenz, R. D.; Jull, A. J. T.; Swindle, T. D.; Lunine, J. I.

Just as cosmic rays interact with nitrogen atoms in the atmosphere of Earth to gener- ate radiocarbon (14C), the same process should occur in Titan`s nitrogen-rich atmo- sphere. Titan`s atmosphere is thick enough that cosmic ray flux, rather than nitrogen column depth, limits the production of 14 C. Absence of a strong magnetic field and the increased distance from the sun suggest production rates of 9 atom/cm2/s, approx- imately 4 times higher than Earth. On Earth the carbon is rapidly oxidised into CO2. The fate and detectability of 14C on Titan depends on the chemical species into which it is incorporated in Titan's reducing atmosphere : as methane it would be hopelessly diluted even in only the atmosphere (ignoring the other, much more massive carbon reservoirs likely to be present on Titan, like hydrocarbon lakes.) However, in the more likely case that the 14C attaches to the haze that rains out onto the surface (as tholin, HCN or acetylene and their polymers - a much smaller carbon reservoir) , haze in the atmosphere or recently deposited on the surface would therefore be quite intrinsically radioactive. Such activity may modify the haze electrical charging and hence its coag- ulation. Measurements with compact instrumentation on future in-situ missions could place useful constraints on the mass deposition rates of photochemical material on the surface and identify locations where surface deposits of such material are `freshest`.

Study on isopropanol degradation by UV/TiO2 nanotube

Science.gov (United States)

Cheng, Hsiu-Yueh; Chang, Kai-Chau; Lin, Kae-Long; Ma, Chih-Ming

2018-04-01

When a semiconductor molecule absorbs photons with energy equal to or greater than its band-gap, electrons in the valence band can be excited and jump up into the conduction band and thus charge carriers are generated. When these charge carriers successfully migrate to the solid surface without recombining, the electrons and holes may undergo electron-transfer processes with adsorbates of suitable redox potentials. The photogenerated holes react with the water to produce hydroxyl radicals, while the photogenerated electrons react with molecular oxygen to give superoxide radical anions. These radicals so produced are highly reactive and they work together to completely oxidize the organic species. In this study, TiO2 nanotube has been prepared and was to be used to control acetone. In this work, mesoporous nanotubes by hydrothermal treatment in aqueous sodium hydroxide solution have been synthesized. Direct hydrothermal synthesis method is easy and efficient to synthesize titanate nanotubes. Using sodium hydroxide, the considerable decrease in reaction time and reaction temperature was achieved.

Non-damaging and scalable carbon nanotube synthesis on carbon fibres

OpenAIRE

De Luca, H; Anthony, DB; Qian, H; Greenhalgh, E; Bismarck, A; Shaffer, M

2016-01-01

The growth of carbon nanotubes (CNTs) on carbon fibres (CFs) to produce a hierarchical fibre with two differing reinforcement length scales, in this instance nanometre and micrometre respectively, is considered a route to improve current state-of-the-art fibre reinforced composites [1]. The scalable production of carbon nanotube-grafted-carbon fibres (CNT-g-CFs) has been limited due to high temperatures, the use of flammable gases and the requirement of inert conditions for CNT synthesis, whi...

Biofunctionalization of multiwalled carbon nanotubes by irradiation of electropolymerized poly(pyrrole-diazirine) films.

Science.gov (United States)

Papper, Vladislav; Gorgy, Karine; Elouarzaki, Kamal; Sukharaharja, Ayrine; Cosnier, Serge; Marks, Robert S

2013-07-15

A photoactivatable poly(pyrrole-diazirine) film was synthesized and electropolymerized as a versatile tool for covalent binding of laccase and glucose oxidase on multiwalled carbon nanotube coatings and Pt, respectively. Irradiation of the functionalized nanotubes allowed photochemical grafting of laccase and its subsequent direct electrical wiring, as illustrated by the electrocatalytic reduction of oxygen. Moreover, covalent binding of glucose oxidase as model enzyme, achieved by UV activation of electropolymerized pyrrole-diazirine, allowed a glucose biosensor to be realized. This original method to graft biomolecules combines electrochemical and photochemical techniques. The simplicity of this new method allows it to be extended easily to other biological systems. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Titan Casts Revealing Shadow

Science.gov (United States)

2004-05-01

A rare celestial event was captured by NASA's Chandra X-ray Observatory as Titan -- Saturn's largest moon and the only moon in the Solar System with a thick atmosphere -- crossed in front of the X-ray bright Crab Nebula. The X-ray shadow cast by Titan allowed astronomers to make the first X-ray measurement of the extent of its atmosphere. On January 5, 2003, Titan transited the Crab Nebula, the remnant of a supernova explosion that was observed to occur in the year 1054. Although Saturn and Titan pass within a few degrees of the Crab Nebula every 30 years, they rarely pass directly in front of it. "This may have been the first transit of the Crab Nebula by Titan since the birth of the Crab Nebula," said Koji Mori of Pennsylvania State University in University Park, and lead author on an Astrophysical Journal paper describing these results. "The next similar conjunction will take place in the year 2267, so this was truly a once in a lifetime event." Animation of Titan's Shadow on Crab Nebula Animation of Titan's Shadow on Crab Nebula Chandra's observation revealed that the diameter of the X-ray shadow cast by Titan was larger than the diameter of its solid surface. The difference in diameters gives a measurement of about 550 miles (880 kilometers) for the height of the X-ray absorbing region of Titan's atmosphere. The extent of the upper atmosphere is consistent with, or slightly (10-15%) larger, than that implied by Voyager I observations made at radio, infrared, and ultraviolet wavelengths in 1980. "Saturn was about 5% closer to the Sun in 2003, so increased solar heating of Titan may account for some of this atmospheric expansion," said Hiroshi Tsunemi of Osaka University in Japan, one of the coauthors on the paper. The X-ray brightness and extent of the Crab Nebula made it possible to study the tiny X-ray shadow cast by Titan during its transit. By using Chandra to precisely track Titan's position, astronomers were able to measure a shadow one arcsecond in

Enhanced Electro-Static Modulation of Ionic Diffusion through Carbon Nanotube Membranes by Diazonium Grafting Chemistry

Science.gov (United States)

Majumder, Mainak; Keis, Karin; Zhan, Xin; Meadows, Corey; Cole, Jeggan

2013-01-01

A membrane structure consisting of an aligned array of open ended carbon nanotubes (~ 7 nm i.d.) spanning across an inert polymer matrix allows the diffusive transport of aqueous ionic species through CNT cores. The plasma oxidation process that opens CNTs tips inherently introduces carboxylic acid groups at the CNT tips, which allows for a limited amount of chemical functional at the CNT pore entrance. However for numerous applications, it is important to increase the density of carboxylic acid groups at the pore entrance for effective separation processes. Aqueous diazonium based electro-chemistry significantly increases the functional density of carboxylic acid groups. pH dependent dye adsorption-desorption and interfacial capacitance measurements indicate ~ 5–6 times increase in functional density. To further control the spatial location of the functional chemistry, a fast flowing inert liquid column inside the CNT core is found to restrict the diazonium grafting to the CNT tips only. This is confirmed by the increased flux of positively charged Ru(bi-py)3+2 with anionic functionality. The electrostatic enhancement of ion diffusion is readily screened in 0.1(M) electrolyte solution consistent with the membrane pore geometry and increased functional density. PMID:25132719

The effect of TTNT nanotubes on hydrogen sorption using MgH2

Directory of Open Access Journals (Sweden)

Mariana Coutinho Brum

2013-06-01

Full Text Available Nanotubes are promising materials to be used with magnesium hydride, as catalysts, in order to enhance hydrogen sorption. A study was performed on the hydrogen absorption/desorption properties of MgH2 with the addition of TTNT (TiTanate NanoTubes. The MgH2-TTNT composite was prepared by ball milling and the influence of the TTNT amount (1.0 and 5.0 wt. (% on the hydrogen capacity was evaluated. The milling of pure MgH2 was performed for 24 hours and afterwards the MgH2-TTNT composite was milled for 20 minutes. Transmission Electronic Microscopy (TEM and Scanning Electron Microscopy (SEM were used to evaluate the nanotube synthesis and show the particle morphology of the MgH2-TTNT composite, respectively. The Differential Scanning Calorimetry (DSC examination provided some evidence with the shifting of the peaks obtained when the amount of TTNT is increased. The hydrogen absorption/desorption kinetics tests showed that the TTNT nanotubes can enhance hydrogen sorption effectively and the total hydrogen capacity obtained was 6.5 wt. (%.

The effect of TTNT nanotubes on hydrogen sorption using MgH2

International Nuclear Information System (INIS)

Brum, Mariana Coutinho; Jardim, Paula Mendes; Conceicao, Monique Osorio Talarico da; Santos, Dilson Silva dos

2013-01-01

Nanotubes are promising materials to be used with magnesium hydride, as catalysts, in order to enhance hydrogen sorption. A study was performed on the hydrogen absorption/desorption properties of MgH 2 with the addition of TTNT (TiTanate nanotubes). The MgH 2 -TTNT composite was prepared by ball milling and the influence of the TTNT amount (1.0 and 5.0 wt. (%)) on the hydrogen capacity was evaluated. The milling of pure MgH 2 was performed for 24 hours and afterwards the MgH 2 -TTNT composite was milled for 20 minutes. Transmission Electronic Microscopy (TEM) and Scanning Electron Microscopy (SEM) were used to evaluate the nanotube synthesis and show the particle morphology of the MgH 2 -TTNT composite, respectively. The Differential Scanning Calorimetry (DSC) examination provided some evidence with the shifting of the peaks obtained when the amount of TTNT is increased. The hydrogen absorption/desorption kinetics tests showed that the TTNT nanotubes can enhance hydrogen sorption effectively and the total hydrogen capacity obtained was 6.5 wt. (%). (author)

Poly(2-hydroxyethyl methacrylate) grafted halloysite nanotubes as a molecular host matrix for luminescent ions prepared by surface-initiated RAFT polymerization and coordination chemistry

Energy Technology Data Exchange (ETDEWEB)

Islam, Md. Rafiqul; Bach, Long Giang; Lim, Kwon Taek, E-mail: ktlim@pknu.ac.kr

2013-07-01

A fluorescent nanohybrid complex comprising of halloysite nanotubes (HNTs), poly(2-hydroxyethyl methacrylate) (PHEMA), and europium ions (Eu{sup 3+}) was synthesized by the combination of surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization and coordination chemistry. Initially, PHEMA was grafted from the HNTs by SI-RAFT and then reacted with succinic anhydride to provide carboxyl acid groups on the external layers of HNTs-g-PHEMA nanohybrids. The subsequent coordination of the nanohybrids with Eu{sup 3+} ions afforded photoluminescent Eu{sup 3+} tagged HNTs-g-PHEMA nanohybrid complexes (HNTs-g-PHEMA-Eu{sup 3+}). The structure, morphology, and fluorescence properties of the Eu{sup 3+} coordinated nanohybrid complexes were investigated by respective physical and spectral studies. FT-IR, XPS, and EDS analyses suggested the formation of the HNTs-g-PHEMA-Eu{sup 3+} nanohybrids. FE-SEM images indicated the immobilization of polymer layers on HNTs. TGA scans further demonstrated the grafting of PHEMA onto HNTs surface. The optical properties of HNTs-g-PHEMA-Eu{sup 3+} nanohybrid complexes were investigated by photoluminescence spectroscopy.

Platinum and palladium on carbon nanotubes : Experimental and theoretical studies

NARCIS (Netherlands)

Adjizian, J. J.; De Marco, P.; Suarez-Martinez, I.; El Mel, A. A.; Snyders, R.; Gengler, R. Y. N.; Rudolf, P.; Ke, X.; Van Tendeloo, G.; Bittencourt, C.; Ewels, C. P.

2013-01-01

Pristine and oxygen plasma functionalised carbon nanotubes (CNTs) were studied after the evaporation of Pt and Pd atoms. High resolution transmission electron microscopy shows the formation of metal nanoparticles at the CNT surface. Oxygen functional groups grafted by the plasma functionalization

Grafting the surface of carbon nanotubes and carbon black with the chemical properties of hyperbranched polyamines

Science.gov (United States)

Morales-Lara, Francisco; Domingo-García, María; López-Garzón, Rafael; Luz Godino-Salido, María; Peñas-Sanjuán, Antonio; López-Garzón, F. Javier; Pérez-Mendoza, Manuel; Melguizo, Manuel

2016-01-01

Controlling the chemistry on the surface of new carbon materials is a key factor to widen the range of their applicability. In this paper we show a grafting methodology of polyalkylamines to the surface of carbon nanomaterials, in particular, carbon nanotubes and a carbon black. The aim of this work is to reach large degrees of covalent functionalization with hyperbranched polyethyleneimines (HBPEIs) and to efficiently preserve the strong chelating properties of the HBPEIs when they are fixed to the surface of these carbon materials. This functionalization opens new possibilities of using these carbon nanotubes-based hybrids. The results show that the HBPEIs are covalently attached to the carbon materials, forming hybrids. These hybrids emerge from the reaction of amine functions of the HBPEIs with carbonyls and carboxylic anhydrides of the carbon surface which become imine and imide bonds. Thus, due to the nature of these bonds, the pre-oxidized samples with relevant number of C=O groups showed an increase in the degree of functionalization with the HBPEIs. Furthermore, both the acid-base properties and the coordination capacity for metal ions of the hybrids are equivalent to that of the free HBPEIs in solution. This means that the chemical characteristics of the HBPEIs have been efficiently transferred to the hybrids. To reach this conclusion we have developed a novel procedure to assess the acid-base and the coordination properties of the hybrids (solids) by means of potentiometric titration. The good agreement of the values obtained for the hybrids and for the free HBPEIs in aqueous solution supports the reliability of the procedure. Moreover, the high capacity of the hybrids to capture Ni2+ by complexation opens new possibilities of using these hybrids to capture high-value metal ions such as Pd2+ and Pt2+.

Fluorescence and Cytotoxicity of Cadmium Sulfide Quantum Dots Stabilized on Clay Nanotubes

Directory of Open Access Journals (Sweden)

Anna V. Stavitskaya

2018-05-01

Full Text Available Quantum dots (QD are widely used for cellular labeling due to enhanced brightness, resistance to photobleaching, and multicolor light emissions. CdS and CdxZn1−xS nanoparticles with sizes of 6–8 nm were synthesized via a ligand assisted technique inside and outside of 50 nm diameter halloysite clay nanotubes (QD were immobilized on the tube’s surface. The halloysite–QD composites were tested by labeling human skin fibroblasts and prostate cancer cells. In human cell cultures, halloysite–QD systems were internalized by living cells, and demonstrated intense and stable fluorescence combined with pronounced nanotube light scattering. The best signal stability was observed for QD that were synthesized externally on the amino-grafted halloysite. The best cell viability was observed for CdxZn1−xS QD immobilized onto the azine-grafted halloysite. The possibility to use QD clay nanotube core-shell nanoarchitectures for the intracellular labeling was demonstrated. A pronounced scattering and fluorescence by halloysite–QD systems allows for their promising usage as markers for biomedical applications.

Water-Dispersible Multi-Walled Carbon Nanotubes and Novel Hybrid Nanostructures

NARCIS (Netherlands)

Pham, Tuan Anh; Son, Se Mo; Jeong, Yeon Tae

2010-01-01

Water-dispersible multi-walled carbon nanotubes (MWNTs) were successfully prepared by the chemical grafting of acylated MWNTs with adenosine. The MWNTs were first purified and oxidized in order to obtain carboxylic acid funcionalized MWNTs, which was further acylated with thionyl chloride to give

A facile and scalable method to prepare carbon nanotube-grafted-graphene for high performance Li-S battery

Science.gov (United States)

Wang, Q. Q.; Huang, J. B.; Li, G. R.; Lin, Z.; Liu, B. H.; Li, Z. P.

2017-01-01

A carbon nanotube-grafted-graphene (CNT-g-Gr) is developed for enhancements of electrical conduction and polysulfide (PS) absorption to improve rate performance and cycleability of lithium-sulfur battery. The CNT-g-Gr is prepared through CNT growth on Ni-deposited graphene sheet which is fabricated via pyrolysis of glucose in a molten salt. The obtained CNT-g-Gr shows much higher specific surface area and PS adsorption capability than graphene. The in-situ formed Ni nanoparticles on graphene sheet not only serve as the catalytic sites for CNT growth, but also function as the anchor-sites for polar PS absorption. The CNT-g-Gr contributes a superb PS adsorption capability arising from graphene and CNT absorbing weakly-polar PS species, and Ni nanoparticles absorbing the species with stronger polarity. The resultant Li-S battery with the CNT-g-Gr shows excellent cycleability and rate performance. A stable discharge capacity of 900 mAh g-1 (with low capacity degradation rate) and a rate capacity of 260 mAh g-1 at 30 C discharge rate have been achieved.

Titan Aerial Daughtercraft

Data.gov (United States)

National Aeronautics and Space Administration — Saturn's giant moon Titan has become one of the most fascinating bodies in the Solar System. Titan is the richest laboratory in the solar system for studying...

The effect of TTNT nanotubes on hydrogen sorption using MgH{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Brum, Mariana Coutinho; Jardim, Paula Mendes; Conceicao, Monique Osorio Talarico da; Santos, Dilson Silva dos, E-mail: monique@metalmat.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (PEMM/COPPEP/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Metalurgica e de Materiais

2013-11-01

Nanotubes are promising materials to be used with magnesium hydride, as catalysts, in order to enhance hydrogen sorption. A study was performed on the hydrogen absorption/desorption properties of MgH{sub 2} with the addition of TTNT (TiTanate nanotubes). The MgH{sub 2} -TTNT composite was prepared by ball milling and the influence of the TTNT amount (1.0 and 5.0 wt. (%)) on the hydrogen capacity was evaluated. The milling of pure MgH{sub 2} was performed for 24 hours and afterwards the MgH{sub 2} -TTNT composite was milled for 20 minutes. Transmission Electronic Microscopy (TEM) and Scanning Electron Microscopy (SEM) were used to evaluate the nanotube synthesis and show the particle morphology of the MgH{sub 2} -TTNT composite, respectively. The Differential Scanning Calorimetry (DSC) examination provided some evidence with the shifting of the peaks obtained when the amount of TTNT is increased. The hydrogen absorption/desorption kinetics tests showed that the TTNT nanotubes can enhance hydrogen sorption effectively and the total hydrogen capacity obtained was 6.5 wt. (%). (author)

Synthesis of benzimidazole-grafted graphene oxide/multi-walled carbon nanotubes composite for supercapacitance application

International Nuclear Information System (INIS)

Srivastava, Rajesh Kr.; Xingjue, Wang; Kumar, Vinod; Srivastava, Anchal; Singh, Vidya Nand

2014-01-01

Highlights: • We are reporting supercapacitance performance of BI-GO/MWCNTs composite. • The specific capacitance of BI-GO/MWCNTs is 275 and 460 F/g at 200 and 5 mV/s scan rate. • This composite has shown 224 F/g capacitance after 1300 cycles at 200 mV/s scan rate. - Abstract: We are reporting the fabrication, characterizations and supercapacitance performance of benzimidazole-grafted graphene oxide/multi-walled carbon nanotubes (BI-GO/MWCNTs) composite. The synthesis of BI-GO materials involves cyclization reaction of carboxylic groups on GO among the hydroxyl and amino groups on o-phenylenediamine. The BI-GO/MWCNTs composite has been fabricated via in situ reduction of BI-GO using hydrazine in presence of MWCNTs. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) have been used to characterize its surface and elemental composition. The uniform dispersion of MWCNTs with BI-GO helps to improve the charge transfer reaction during electrochemical process. The specific capacitance of BI-GO/MWCNTs composite is 275 and 460 F/g at 200 and 5 mV/s scan rate in 1 mol/L aqueous solution of H 2 SO 4 . This BI-GO/MWCNTs composite has shown 224 F/g capacitance after 1300 cycles at 200 mV/s scan rate, which represents its good electrochemical stability

Synthesis of stable TiO2 nanotubes: effect of hydrothermal treatment, acid washing and annealing temperature.

Science.gov (United States)

López Zavala, Miguel Ángel; Lozano Morales, Samuel Alejandro; Ávila-Santos, Manuel

2017-11-01

Effect of hydrothermal treatment, acid washing and annealing temperature on the structure and morphology of TiO 2 nanotubes during the formation process was assessed. X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy analysis were conducted to describe the formation and characterization of the structure and morphology of nanotubes. Hydrothermal treatment of TiO 2 precursor nanoparticles and acid washing are fundamental to form and define the nanotubes structure. Hydrothermal treatment causes a change in the crystallinity of the precursor nanoparticles from anatase phase to a monoclinic phase, which characterizes the TiO 2 nanosheets structure. The acid washing promotes the formation of high purity nanotubes due to Na + is exchanged from the titanate structure to the hydrochloric acid (HCl) solution. The annealing temperature affects the dimensions, structure and the morphology of the nanotubes. Annealing temperatures in the range of 400 °C and 600 °C are optimum to maintain a highly stable tubular morphology of nanotubes. Additionally, nanotubes conserve the physicochemical properties of the precursor Degussa P25 nanoparticles. Temperatures greater than 600 °C alter the morphology of nanotubes from tubular to an irregular structure of nanoparticles, which are bigger than those of the precursor material, i.e., the crystallinity turn from anatase phase to rutile phase inducing the collapse of the nanotubes.

Novel Polyvinyl Alcohol/Styrene Butadiene Rubber Latex/Carboxymethyl Cellulose Nanocomposites Reinforced with Modified Halloysite Nanotubes

Directory of Open Access Journals (Sweden)

Yanjun Tang

2013-01-01

Full Text Available Novel polyvinyl alcohol (PVA/styrene butadiene rubber (SBR latex/carboxymethyl cellulose (CMC/halloysite nanotubes (HNTs nanocomposites were successfully prepared through physical blending. The as-obtained PVA/SBR/CMC/HNTs nanocomposites were coated on the surface of old corrugated container (OCC-based paper in an effort to improve the mechanical properties of paper. To improve the dispersion of HNTs and enhance the compatibility between HNTs and polymer matrix, HNTs were modified with titanate coupling agent (TCA. FT-IR, together with TGA, confirmed that TCA was grafted onto the surface of HNTs successfully. XRD demonstrated that the crystal structures of HNTs remained almost unchanged. TEM showed that modified HNTs exhibited good dispersion and possessed nanotubular structures with an outer diameter of around 50 nm and an inner diameter of about 20 nm. SEM gave an indication that modified HNTs were dispersed more uniformly than unmodified HNTs within PVA/SBR/CMC matrix. Rheological measurement exhibited that surface modification process enhanced the compatibility between HNTs and polymer matrix, thus resulting in the decreased viscosity of nanocomposites. In comparison with unmodified HNTs, modified HNTs were found to contribute more to the enhancement in mechanical properties, which might be attributed to the better dispersion and compatibility of modified HNTs evidenced by TEM, SEM, and rheological measurement.

Surface functionalization of aluminosilicate nanotubes with organic molecules

Directory of Open Access Journals (Sweden)

Wei Ma

2012-02-01

Full Text Available The surface functionalization of inorganic nanostructures is an effective approach for enriching the potential applications of existing nanomaterials. Inorganic nanotubes attract great research interest due to their one-dimensional structure and reactive surfaces. In this review paper, recent developments in surface functionalization of an aluminosilicate nanotube, “imogolite”, are introduced. The functionalization processes are based on the robust affinity between phosphate groups of organic molecules and the aluminol (AlOH surface of imogolite nanotubes. An aqueous modification process employing a water soluble ammonium salt of alkyl phosphate led to chemisorption of molecules on imogolite at the nanotube level. Polymer-chain-grafted imogolite nanotubes were prepared through surface-initiated polymerization. In addition, the assembly of conjugated molecules, 2-(5’’-hexyl-2,2’:5’,2’’-terthiophen-5-ylethylphosphonic acid (HT3P and 2-(5’’-hexyl-2,2’:5’,2’’-terthiophen-5-ylethylphosphonic acid 1,1-dioxide (HT3OP, on the imogolite nanotube surface was achieved by introducing a phosphonic acid group to the corresponding molecules. The optical and photophysical properties of these conjugated-molecule-decorated imogolite nanotubes were characterized. Moreover, poly(3-hexylthiophene (P3HT chains were further hybridized with HT3P modified imogolite to form a nanofiber hybrid.

Thermal treatment of the carbon nanotubes and their functionalization with styrene

International Nuclear Information System (INIS)

De Falco, Alejandro; Fascio, Mirta L.; Lamanna, Melisa E.; Corcuera, Maria A.; Mondragon, Inaki; Rubiolo, Gerardo H.; D'Accorso, Norma B.; Goyanes, Silvia

2009-01-01

In this work we studied the functionalization of commercially available multiwalled carbon nanotubes (MWCNT) (Nanocyl 3100) with polystyrene by the method so called 'grafting from'. The nanotubes were used as received and oxidized in air at 400 deg. C. The functionalization was started using thionyl chloride under reflux, followed by a reaction with ethylene glycol which allowed the inclusion of hydroxyl groups. The reaction of those with 2-chloropropionyl chloride led to the generation of the polymerization initiator. Last, the radical polymerization of the functionalized nanotubes, using styrene as the monomer, led to new materials which were studied with thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and ultraviolet-visible (UV-vis) spectroscopy.

Chemically immobilised carbon nanotubes on silicon: Stable surfaces for aqueous electrochemistry

Energy Technology Data Exchange (ETDEWEB)

Flavel, Benjamin S., E-mail: ben.flavel@flinders.edu.a [Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch 8140 (New Zealand); School of Chemistry, Physics and Earth Sciences, Flinders University, Sturt Road, Bedford Park, Adelaide, South Australia 5001 (Australia); Garrett, David J.; Lehr, Joshua [Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch 8140 (New Zealand); MacDiarmid Institute for Advanced Materials and Nanotechnology, Private Bag 4800, Christchurch 8140 (New Zealand); Shapter, Joseph G. [School of Chemistry, Physics and Earth Sciences, Flinders University, Sturt Road, Bedford Park, Adelaide, South Australia 5001 (Australia); Downard, Alison J., E-mail: alison.downard@canterbury.ac.n [Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch 8140 (New Zealand); MacDiarmid Institute for Advanced Materials and Nanotechnology, Private Bag 4800, Christchurch 8140 (New Zealand)

2010-04-30

Diazonium ion chemistry has been used to electrochemically graft aminophenyl layers onto p-type silicon (1 0 0) substrates. A condensation reaction was used to immobilise single-walled carbon nanotubes with high carboxylic acid functionality directly to this layer. Electrochemical monitoring of the aminophenyl groups confirmed the formation of an amide linkage between the single-walled carbon nanotubes and the aminophenyl layer. The carbon nanotube electrode showed high stability and good electrochemical performance in aqueous solution. At moderate scan rates the Ru(NH{sub 3}){sub 6}{sup +3/+2} couple exhibited quasi-reversible electron transfer kinetics with a standard heterogenous rate constant of 1.2 x 10{sup -3} cm s{sup -1} at the covalently-linked carbon nanotube surface. The electrode thus combines the advantages of a silicon substrate for easy integration into sophisticated electrical and electronic devices, carbon nanotubes for desirable electrochemical properties, and stability in aqueous medium for future applications in environmental sensing.

Chemically immobilised carbon nanotubes on silicon: Stable surfaces for aqueous electrochemistry

International Nuclear Information System (INIS)

Flavel, Benjamin S.; Garrett, David J.; Lehr, Joshua; Shapter, Joseph G.; Downard, Alison J.

2010-01-01

Diazonium ion chemistry has been used to electrochemically graft aminophenyl layers onto p-type silicon (1 0 0) substrates. A condensation reaction was used to immobilise single-walled carbon nanotubes with high carboxylic acid functionality directly to this layer. Electrochemical monitoring of the aminophenyl groups confirmed the formation of an amide linkage between the single-walled carbon nanotubes and the aminophenyl layer. The carbon nanotube electrode showed high stability and good electrochemical performance in aqueous solution. At moderate scan rates the Ru(NH 3 ) 6 +3/+2 couple exhibited quasi-reversible electron transfer kinetics with a standard heterogenous rate constant of 1.2 x 10 -3 cm s -1 at the covalently-linked carbon nanotube surface. The electrode thus combines the advantages of a silicon substrate for easy integration into sophisticated electrical and electronic devices, carbon nanotubes for desirable electrochemical properties, and stability in aqueous medium for future applications in environmental sensing.

Uniformly active phase loaded selective catalytic reduction catalysts (V_2O_5/TNTs) with superior alkaline resistance performance

International Nuclear Information System (INIS)

Wang, Haiqiang; Wang, Penglu; Chen, Xiongbo; Wu, Zhongbiao

2017-01-01

Highlights: • VOSO_4 exhibited better synergistic effect with titanate nanotubes than NH_4VO_3. • Ion-exchange reaction occurs between VOSO_4 and titanate nanotubes. • Ion-exchange resulting in uniformly vanadium distribution on titanate nanotubes. • VOSO_4-based catalyst exhibited impressive SCR activity and alkaline resistance. - Abstract: In this work, protonated titanate nanotubes was performed as a potential useful support and different vanadium precursors (NH_4VO_3 and VOSO_4) were used to synthesize deNO_x catalysts. The results showed that VOSO_4 exhibited better synergistic effect with titanate nanotubes than NH_4VO_3, which was caused by the ion-exchange reaction. Then high loading content of vanadium, uniformly active phase distribution, better dispersion of vanadium, more acid sites, better V"5"+/V"4"+ redox cycles and superior oxygen mobility were achieved. Besides, VOSO_4-based titanate nanotubes catalysts also showed enhanced alkaline resistance than particles (P25) based catalysts. It was strongly associated with its abundant acid sites, large surface area, flexible redox cycles and oxygen transfer ability. For the loading on protonated titanate nanotubes, active metal with cation groups was better precursors than anion ones. V_2O_5/TNTs catalyst was a promising substitute for the commercial vanadium catalysts and the work conducted herein provided a useful idea to design uniformly active phase loaded catalyst.

Grafting 3-mercaptopropyl trimethoxysilane on multi-walled carbon nanotubes surface for improving on-line cadmium(II) preconcentration from water samples

Energy Technology Data Exchange (ETDEWEB)

Corazza, Marcela Zanetti; Somera, Bruna Fabrin; Segatelli, Mariana Gava [Departamento de Quimica, Universidade Estadual de Londrina, Rodovia Celso Garcia Cid, PR 445, Km 380, Campus Universitario, Londrina-PR, CEP 86051-990 (Brazil); Tarley, Cesar Ricardo Teixeira, E-mail: tarley@uel.br [Departamento de Quimica, Universidade Estadual de Londrina, Rodovia Celso Garcia Cid, PR 445, Km 380, Campus Universitario, Londrina-PR, CEP 86051-990 (Brazil); Instituto Nacional de Ciencia e Tecnologia (INCT) de Bioanalitica, Universidade Estadual de Campinas (UNICAMP), Instituto de Quimica, Departamento de Quimica Analitica, Cidade Universitaria Zeferino, Vaz, s/n, CEP 13083-970, Campinas-SP (Brazil)

2012-12-15

Highlights: Black-Right-Pointing-Pointer 3-Mercaptopropyl trimethoxysilane grafted on MWCNT surface was prepared. Black-Right-Pointing-Pointer The material promoted an increase on performance of MWCNT for Cd{sup 2+} adsorption. Black-Right-Pointing-Pointer The life time of adsorbent was very high. Black-Right-Pointing-Pointer An improvement of 84% on the sensitivity was achieved. - Abstract: In the present study, the performance of multi-walled carbon nanotubes (MWCNTs) grafted with 3-mercaptopropyltrimethoxysilane (3-MPTMS), used as a solid phase extractor for Cd{sup 2+} preconcentration in a flow injection system coupled to flame atomic absorption spectrometry (FAAS), was evaluated. The procedure involved the preconcentration of 20.0 mL of Cd{sup 2+} solution at pH 7.5 (0.1 mol L{sup -1} buffer phosphate) through 70 mg of 3-MPTMS-grafted MWCNTs packed into a minicolumn at 6.0 mL min{sup -1}. The elution step was carried out with 1.0 mol L{sup -1} HCl. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to estimate the extent of the MWCNT chemical modification. The 3-MPTMS-grafted MWCNTs provided a 1.68 times improvement in the sensitivity of the Cd{sup 2+} FAAS determination compared to the unsilanized oxidized MWCNTs. The following parameters were obtained: preconcentration factor of 31.5, consumptive index of 0.635 mL, sample throughput of 14 h{sup -1}, and concentration efficiency of 9.46 min{sup -1}. The analytical curve was constructed in the range of 1.0-60.0 {mu}g L{sup -1} (r = 0.9988), and the detection and quantification limits were found to be 0.15 {mu}g L{sup -1} and 0.62 {mu}g L{sup -1}, respectively. Different types of water samples and cigarette sample were successfully analyzed, and the results were compared using electrothermal atomic absorption spectrometry (ETAAS) as reference technique. In addition, the accuracy of proposed method was also checked by analysis of

The TITAN reversed-field-pinch fusion reactor study

International Nuclear Information System (INIS)

1990-01-01

This report discusses the following topics: overview of titan-2 design; titan-2 fusion-power-core engineering; titan-2 divertor engineering; titan-2 tritium systems; titan-2 safety design and radioactive-waste disposal; and titan-2 maintenance procedures

The TITAN reversed-field-pinch fusion reactor study

Energy Technology Data Exchange (ETDEWEB)

1990-01-01

This report discusses the following topics: overview of titan-2 design; titan-2 fusion-power-core engineering; titan-2 divertor engineering; titan-2 tritium systems; titan-2 safety design and radioactive-waste disposal; and titan-2 maintenance procedures.

Titan's organic chemistry

Science.gov (United States)

Sagan, C.; Thompson, W. R.; Khare, B. N.

1985-01-01

Voyager discovered nine simple organic molecules in the atmosphere of Titan. Complex organic solids, called tholins, produced by irradiation of the simulated Titanian atmosphere, are consistent with measured properties of Titan from ultraviolet to microwave frequencies and are the likely main constituents of the observed red aerosols. The tholins contain many of the organic building blocks central to life on earth. At least 100-m, and possibly kms thicknesses of complex organics have been produced on Titan during the age of the solar system, and may exist today as submarine deposits beneath an extensive ocean of simple hydrocarbons.

A green synthesis of a layered titanate, potassium lithium titanate; lower temperature solid-state reaction and improved materials performance

International Nuclear Information System (INIS)

Ogawa, Makoto; Morita, Masashi; Igarashi, Shota; Sato, Soh

2013-01-01

A layered titanate, potassium lithium titanate, with the size range from 0.1 to 30 µm was prepared to show the effects of the particle size on the materials performance. The potassium lithium titanate was prepared by solid-state reaction as reported previously, where the reaction temperature was varied. The reported temperature for the titanate preparation was higher than 800 °C, though 600 °C is good enough to obtain single-phase potassium lithium titanate. The lower temperature synthesis is cost effective and the product exhibit better performance as photocatalysts due to surface reactivity. - Graphical abstract: Finite particle of a layered titanate, potassium lithium titanate, was prepared by solid-state reaction at lower temperature to show modified materials performance. Display Omitted - Highlights: • Potassium lithium titanate was prepared by solid-state reaction. • Lower temperature reaction resulted in smaller sized particles of titanate. • 600 °C was good enough to obtain single phased potassium lithium titanate. • The product exhibited better performance as photocatalyst

Multifunctional Electroactive Nanocomposites Based on Piezoelectric Boron Nitride Nanotubes

Science.gov (United States)

Kang, Jin Ho; Sauti, Godfrey; Park, Cheol; Yamakov, Vesselin I.; Wise, Kristopher E.; Lowther, Sharon E.; Fay, Catharine C.; Thibeault, Sheila A.; Bryant, Robert G.

2015-01-01

Space exploration missions require sensors and devices capable of stable operation in harsh environments such as those that include high thermal fluctuation, atomic oxygen, and high-energy ionizing radiation. However, conventional or state-of-the-art electroactive materials like lead zirconate titanate, poly(vinylidene fluoride), and carbon nanotube (CNT)-doped polyimides have limitations on use in those extreme applications. Theoretical studies have shown that boron nitride nanotubes (BNNTs) have strength-to-weight ratios comparable to those of CNTs, excellent high-temperature stability (to 800 C in air), large electroactive characteristics, and excellent neutron radiation shielding capability. In this study, we demonstrated the experimental electroactive characteristics of BNNTs in novel multifunctional electroactive nanocomposites. Upon application of an external electric field, the 2 wt % BNNT/polyimide composite was found to exhibit electroactive strain composed of a superposition of linear piezoelectric and nonlinear electrostrictive components. When the BNNTs were aligned by stretching the 2 wt % BNNT/polyimide composite, electroactive characteristics increased by about 460% compared to the nonstretched sample. An all-nanotube actuator consisting of a BNNT buckypaper layer between two single-walled carbon nanotube buck-paper electrode layers was found to have much larger electroactive properties. The additional neutron radiation shielding properties and ultraviolet/visible/near-infrared optical properties of the BNNT composites make them excellent candidates for use in the extreme environments of space missions. utilizing the unique characteristics of BNNTs.

The TITAN reversed-field-pinch fusion reactor study

International Nuclear Information System (INIS)

1990-01-01

This report discusses research on the titan-1 fusion power core. The major topics covered are: titan-1 fusion-power-core engineering; titan-1 divertor engineering; titan-1 tritium systems; titan-1 safety design and radioactive-waste disposal; and titan-1 maintenance procedures

The TITAN reversed-field-pinch fusion reactor study

Energy Technology Data Exchange (ETDEWEB)

1990-01-01

This report discusses research on the titan-1 fusion power core. The major topics covered are: titan-1 fusion-power-core engineering; titan-1 divertor engineering; titan-1 tritium systems; titan-1 safety design and radioactive-waste disposal; and titan-1 maintenance procedures.

Titan's Methane Cycle is Closed

Science.gov (United States)

Hofgartner, J. D.; Lunine, J. I.

2013-12-01

Doppler tracking of the Cassini spacecraft determined a polar moment of inertia for Titan of 0.34 (Iess et al., 2010, Science, 327, 1367). Assuming hydrostatic equilibrium, one interpretation is that Titan's silicate core is partially hydrated (Castillo-Rogez and Lunine, 2010, Geophys. Res. Lett., 37, L20205). These authors point out that for the core to have avoided complete thermal dehydration to the present day, at least 30% of the potassium content of Titan must have leached into an overlying water ocean by the end of the core overturn. We calculate that for probable ammonia compositions of Titan's ocean (compositions with greater than 1% ammonia by weight), that this amount of potassium leaching is achievable via the substitution of ammonium for potassium during the hydration epoch. Formation of a hydrous core early in Titan's history by serpentinization results in the loss of one hydrogen molecule for every hydrating water molecule. We calculate that complete serpentinization of Titan's core corresponds to the release of more than enough hydrogen to reconstitute all of the methane atoms photolyzed throughout Titan's history. Insertion of molecular hydrogen by double occupancy into crustal clathrates provides a storage medium and an opportunity for ethane to be converted back to methane slowly over time--potentially completing a cycle that extends the lifetime of methane in Titan's surface atmosphere system by factors of several to an order of magnitude over the photochemically-calculated lifetime.

Bienzymatic Acetylcholinesterase and Choline Oxidase Immobilized Biosensor Based on a Phenyl Carboxylic Acid-Grafted Multiwalled Carbon Nanotube

Directory of Open Access Journals (Sweden)

So-Ra Lee

2014-01-01

Full Text Available Bienzymatic acetylcholinesterase (AChE and choline oxidase (ChOx immobilized biosensor based on a phenyl carboxylic acid-grafted multiwalled carbon nanotube (MWNT modified glass carbon electrode (GCE and carbon-screen printed electrode (SPE was fabricated for acetylcholine detection in human blood samples. Phenyl carboxylic acid-modified MWNT supports were prepared by electrochemical polymerization of 4-carboxyphenyl diazonium salts, which were synthesized by an amine group and sodium nitrite, on the surface of the MWNT-modified GCE and SPE in 0.1 M PBS. The successful fabrication of the AChE-ChOx-immobilized biosensor was confirmed via scanning electron microscopy (SEM, X-ray photoelectron spectroscopy (XPS, electrochemical impedance spectroscopy (EIS, and cyclic voltammetry (CV. The sensing range of the biosensor based on a GCE and SPE was 1.0~10 μM and 10~100 μM, respectively. The interfering effect of 0.1 M L-ascorbic acid, 0.1 M L-cysteine, and 0.1 M uric acid to 0.1 M acetylcholine was 3.00%, 9.00%, and 3.00%, respectively. Acetylcholine in a human blood sample was detected by the AChE-ChOx-immobilized biosensor.

Chemistry and evolution of Titan's atmosphere

International Nuclear Information System (INIS)

Strobel, D.F.

1982-01-01

The chemistry and evolution of Titan's atmosphere is reviewed in the light of the scientific findings from the Voyager mission. It is argued that the present N 2 atmosphere may be Titan's initial atmosphere rather than photochemically derived from an original NH 3 atmosphere. The escape rate of hydrogen from Titan is controlled by photochemical production from hydrocarbons. CH 4 is irreversibly converted to less hydrogen rich hydrocarbons, which over geologic time accumulate on the surface to a layer thickness of approximately 0.5 km. Magnetospheric electrons interacting with Titan's exosphere may dissociate enough N 2 into hot, escaping N atoms to remove approximately 0.2 of Titan's present atmosphere over geologic time. The energy dissipation of magnetospheric electrons exceeds solar e.u.v. energy deposition in Titan's atmosphere by an order of magnitude and is the principal driver of nitrogen photochemistry. The environmental conditions in Titan's upper atmosphere are favorable to building up complex molecules, particularly in the north polar cap region. (author)

Titan Polar Landscape Evolution

Science.gov (United States)

Moore, Jeffrey M.

2016-01-01

With the ongoing Cassini-era observations and studies of Titan it is clear that the intensity and distribution of surface processes (particularly fluvial erosion by methane and Aeolian transport) has changed through time. Currently however, alternate hypotheses substantially differ among specific scenarios with respect to the effects of atmospheric evolution, seasonal changes, and endogenic processes. We have studied the evolution of Titan's polar region through a combination of analysis of imaging, elevation data, and geomorphic mapping, spatially explicit simulations of landform evolution, and quantitative comparison of the simulated landscapes with corresponding Titan morphology. We have quantitatively evaluated alternate scenarios for the landform evolution of Titan's polar terrain. The investigations have been guided by recent geomorphic mapping and topographic characterization of the polar regions that are used to frame hypotheses of process interactions, which have been evaluated using simulation modeling. Topographic information about Titan's polar region is be based on SAR-Topography and altimetry archived on PDS, SAR-based stereo radar-grammetry, radar-sounding lake depth measurements, and superposition relationships between geomorphologic map units, which we will use to create a generalized topographic map.

Uniformly active phase loaded selective catalytic reduction catalysts (V{sub 2}O{sub 5}/TNTs) with superior alkaline resistance performance

Energy Technology Data Exchange (ETDEWEB)

Wang, Haiqiang; Wang, Penglu [Key Laboratory of Environment Remediation and Ecological Health, Ministry of Education, College of Environmental & Resources Science, Zhejiang University, 310058 Hangzhou (China); Zhejiang Provincial Engineering Research Center of Industrial Boiler & Furnace Flue Gas Pollution Control, Hangzhou 310027 (China); Chen, Xiongbo [South China Institute of Environmental Sciences, Ministry of Environmental Protection, Guangzhou 510655 (China); Wu, Zhongbiao, E-mail: zbwu@zju.edu.cn [Key Laboratory of Environment Remediation and Ecological Health, Ministry of Education, College of Environmental & Resources Science, Zhejiang University, 310058 Hangzhou (China); Zhejiang Provincial Engineering Research Center of Industrial Boiler & Furnace Flue Gas Pollution Control, Hangzhou 310027 (China)

2017-02-15

Highlights: • VOSO{sub 4} exhibited better synergistic effect with titanate nanotubes than NH{sub 4}VO{sub 3}. • Ion-exchange reaction occurs between VOSO{sub 4} and titanate nanotubes. • Ion-exchange resulting in uniformly vanadium distribution on titanate nanotubes. • VOSO{sub 4}-based catalyst exhibited impressive SCR activity and alkaline resistance. - Abstract: In this work, protonated titanate nanotubes was performed as a potential useful support and different vanadium precursors (NH{sub 4}VO{sub 3} and VOSO{sub 4}) were used to synthesize deNO{sub x} catalysts. The results showed that VOSO{sub 4} exhibited better synergistic effect with titanate nanotubes than NH{sub 4}VO{sub 3}, which was caused by the ion-exchange reaction. Then high loading content of vanadium, uniformly active phase distribution, better dispersion of vanadium, more acid sites, better V{sup 5+}/V{sup 4+} redox cycles and superior oxygen mobility were achieved. Besides, VOSO{sub 4}-based titanate nanotubes catalysts also showed enhanced alkaline resistance than particles (P25) based catalysts. It was strongly associated with its abundant acid sites, large surface area, flexible redox cycles and oxygen transfer ability. For the loading on protonated titanate nanotubes, active metal with cation groups was better precursors than anion ones. V{sub 2}O{sub 5}/TNTs catalyst was a promising substitute for the commercial vanadium catalysts and the work conducted herein provided a useful idea to design uniformly active phase loaded catalyst.

Synthesis of benzimidazole-grafted graphene oxide/multi-walled carbon nanotubes composite for supercapacitance application

Energy Technology Data Exchange (ETDEWEB)

Srivastava, Rajesh Kr., E-mail: r05bhu@gmail.com [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore (Singapore); Xingjue, Wang [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore (Singapore); Kumar, Vinod [Department of Zoology, Banaras Hindu University, Varanasi (India); Srivastava, Anchal [Department of Physics, Banaras Hindu University, Varanasi (India); Singh, Vidya Nand [CSIR-National Physical Laboratory, New Delhi (India)

2014-11-05

Highlights: • We are reporting supercapacitance performance of BI-GO/MWCNTs composite. • The specific capacitance of BI-GO/MWCNTs is 275 and 460 F/g at 200 and 5 mV/s scan rate. • This composite has shown 224 F/g capacitance after 1300 cycles at 200 mV/s scan rate. - Abstract: We are reporting the fabrication, characterizations and supercapacitance performance of benzimidazole-grafted graphene oxide/multi-walled carbon nanotubes (BI-GO/MWCNTs) composite. The synthesis of BI-GO materials involves cyclization reaction of carboxylic groups on GO among the hydroxyl and amino groups on o-phenylenediamine. The BI-GO/MWCNTs composite has been fabricated via in situ reduction of BI-GO using hydrazine in presence of MWCNTs. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) have been used to characterize its surface and elemental composition. The uniform dispersion of MWCNTs with BI-GO helps to improve the charge transfer reaction during electrochemical process. The specific capacitance of BI-GO/MWCNTs composite is 275 and 460 F/g at 200 and 5 mV/s scan rate in 1 mol/L aqueous solution of H{sub 2}SO{sub 4}. This BI-GO/MWCNTs composite has shown 224 F/g capacitance after 1300 cycles at 200 mV/s scan rate, which represents its good electrochemical stability.

Interaction of Titan's atmosphere with Saturn's magnetosphere

International Nuclear Information System (INIS)

Hartle, R.E.

1985-01-01

The Voyager 1 measurements made during the Titan flyby reveal that Saturn's rotating magnetospheric plasma interacts directly with Titan's neutral atmosphere and ionosphere. This results from the lack of an intrinsic magnetic field at Titan. The interaction induces a magnetosphere which deflects the flowing plasma around Titan and forms a plasma wake downstream. Within the tail of the induced magnetosphere, ions of ionospheric origin flow away from Titan. Just outside Titan's magnetosphere, a substantial ion-exosphere forms from an extensive hydrogen-nitrogen exosphere. The exospheric ions are picked up and carried downstream into the wake by the plasma flowing around Titan. Mass loading produced by the addition of exospheric ions slows the wake plasma down considerably in the vicinity of the magnetopause. 36 references

Titanic: A Statistical Exploration.

Science.gov (United States)

Takis, Sandra L.

1999-01-01

Uses the available data about the Titanic's passengers to interest students in exploring categorical data and the chi-square distribution. Describes activities incorporated into a statistics class and gives additional resources for collecting information about the Titanic. (ASK)

The age of Titan's surface

Science.gov (United States)

Neish, C. D.; Lorenz, R. D.

2010-04-01

High-resolution images of the surface of Titan taken by the Cassini spacecraft reveal a world with an extreme paucity of impact craters. Planetary surfaces are commonly dated by dividing the number of impact craters by the estimated impactor flux, but this approach has been confounded at Titan by several difficulties. First, high-resolution imaging of the surface of Titan is far from complete (in the near-infrared as well as radar). As of December 2007, Cassini RADAR images covered only 22% of its surface. However, we can use Monte-Carlo models to explore how many craters of a given size (with large or very large craters being of particular interest) may be present in the unobserved areas. Second, literature descriptions of the crater formation rate (e.g. Korycansky and Zahnle 2005 and Artemieva and Lunine 2005) are apparently not in agreement. We discuss possible resolutions. Third, since surface modification processes are ongoing, the actual number of craters on Titan's surface remains uncertain, as craters may be eroded beyond recognition, or obscured by lakes or sand seas. In this connection, we use the Earth as an analogue. The Earth is in many ways the most "Titan-like" world in the solar system, with extensive modification by erosion, burial, tectonism, and volcanism. We compare the observed number of terrestrial craters to the expected terrestrial impactor flux to determine the crater reduction factor for a world similar to Titan. From this information, we can back out the actual number of craters on Titan's surface and estimate its crater retention age. An accurate age estimate will be critical for constraining models of Titan's formation and evolution.

The Titan Sky Simulator ™ - Testing Prototype Balloons in Conditions Approximating those in Titan's Atmosphere

Science.gov (United States)

Nott, Julian

This paper will describe practical work flying prototype balloons in the "The Titan Sky Simulator TM " in conditions approximating those found in Titan's atmosphere. Saturn's moon, Titan, is attracting intense scientific interest. This has led to wide interest in exploring it with Aerobots, balloons or airships. Their function would be similar to the Rovers exploring Mars, but instead of moving laboriously across the rough terrain on wheels, they would float freely from location to location. To design any balloon or airship it is essential to know the temperature of the lifting gas as this influences the volume of the gas, which in turn influences the lift. To determine this temperature it is necessary to know how heat is transferred between the craft and its surroundings. Heat transfer for existing balloons is well understood. However, Titan conditions are utterly different from those in which balloons have ever been flown, so heat transfer rates cannot currently be calculated. In particular, thermal radiation accounts for most heat transfer for existing balloons but over Titan heat transfer will be dominated by convection. To be able to make these fundamental calculations, it is necessary to get fundamental experimental data. This is being obtained by flying balloons in a Simulator filled with nitrogen gas at very low temperature, about 95° K / minus 180° C, typical of Titan's temperatures. Because the gas in the Simulator is so cold, operating at atmospheric pressure the density is close to that of Titan's atmosphere. "The Titan Sky Simulator TM " has an open interior approximately 4.5 meter tall and 2.5 meters square. It has already been operated at 95° K/-180° C. By the time of the Conference it is fully expected to have data to present from actual balloons flying at this temperature. Perhaps the most important purpose of this testing is to validate numerical [computational fluid dynamics] models being developed by Tim Colonius of Caltech. These numerical

Carbon nanotube/paraffin/montmorillonite composite phase change material for thermal energy storage.

Science.gov (United States)

Li, Min; Guo, Qiangang; Nutt, Steven

2017-04-01

A composite phase change material (PCM) comprised of organic montmorillonite (OMMT)/paraffin/grafted multi-walled nanotube (MWNT) is synthesized via ultrasonic dispersion and liquid intercalation. The microstructure of the composite PCM has been characterized to determine the phase distribution, and thermal properties (latent heat and thermal conductivity) have been measured by differential scanning calorimetry (DSC) and a thermal constant analyzer. The results show that paraffin molecules are intercalated in the montmorillonite layers and the grafted MWNTs are dispersed in the montmorillonite layers. The latent heat is 47.1 J/g, and the thermal conductivity of the OMMT/paraffin/grafted MWNT composites is 34% higher than that of the OMMT/paraffin composites and 65% higher than that of paraffin.

The atmospheric temperature structure of Titan

Science.gov (United States)

Mckay, Christopher P.; Pollack, J. B.; Courtin, Regis; Lunine, Jonathan I.

1992-01-01

The contribution of various factors to the thermal structure of Titan's past and present atmosphere are discussed. A one dimensional model of Titan's thermal structure is summarized. The greenhouse effect of Titan's atmosphere, caused primarily by pressure induced opacity of N2, CH4, and H2, is discussed together with the antigreenhouse effect dominated by the haze which absorbs incident sunlight. The implications for the atmosphere of the presence of an ocean on Titan are also discussed.

Influence of functional group on the electrical transport properties of polyvinyl alcohol grafted multiwall carbon nanotube composite thick film

Science.gov (United States)

Kumar Das, Amit; Dharmana, Reuben; Mukherjee, Ayan; Baba, Koumei; Hatada, Ruriko; Kumar Meikap, Ajit

2018-04-01

We present a novel technique to obtain a higher or lower value of dielectric constant due to the variation of a functional group on the surface of multiwall carbon nanotube (MWCNTs) for a polyvinyl alcohol (PVA) grafted MWCNT system. We have prepared PVA grafted pristine and different types of functionalized (-COOH, -OH, and -NH2) MWCNT nanocomposite films. The strong interfacial interaction between the host PVA matrix and nanofiller is characterized by different experimental techniques. The frequency variation of the electrical transport properties of the composite films is investigated in a wide temperature range (303 ≤ T ≤ 413 K) and frequency range (20 Hz ≤ f ≤ 1 MHz). The dielectric constant of the amine (-NH2) functionalized MWCNT incorporated PVA film is about 2 times higher than that of the pristine MWCNT embedded PVA film. The temperature variation of the dielectric constant shows an anomalous behaviour. The modified Cole-Cole equation simulated the experimentally observed dielectric spectroscopy at high temperature. The ac conductivity of the composite films obeys the correlated barrier hopping model. The imaginary part of the electric modulus study shows the ideal Debye-type behaviour at low frequency and deviation of that at high frequency. To illustrate the impedance spectroscopy of the nanocomposite films, we have proposed an impedance based battery equivalent circuit model. The current-voltage characteristic shows hysteresis behaviour of the nanocomposite films. The trap state height for all composite films is evaluated by simulating the current density-electric field data with the Poole-Frenkel emission model. This investigation opens a new avenue for designing electronic devices with a suitable combination of cost effective soft materials.

Molecular structures of (3-aminopropyl)trialkoxysilane on hydroxylated barium titanate nanoparticle surfaces induced by different solvents and their effect on electrical properties of barium titanate based polymer nanocomposites

International Nuclear Information System (INIS)

Fan, Yanyan; Wang, Guanyao; Huang, Xingyi; Bu, Jing; Sun, Xiaojin; Jiang, Pingkai

2016-01-01

Graphical abstract: - Highlights: • The silanization on the surface of hydroxylated barium titanate nanoparticles was introduced by using two kinds of trialkoxysilanes with different solvents (toluene and ethanol), respectively. • Solvents have more remarkable impact on the dielectric properties of the subsequent BT/PVDF nanocomposites than the types of silanes. • The solvents used for BT nanoparticle surface modification exhibit a significant effect on the breakdown strength of the nanocomposites. - Abstract: Surface modification of nanoparticles by grafting silane coupling agents has proven to be a significant approach to improve the interfacial compatibility between inorganic filler and polymer matrix. However, the impact of grafted silane molecular structure after the nanoparticle surface modification, induced by the utilized solvents and the silane alkoxy groups, on the electrical properties of the corresponding nanocomposites, has been seldom investigated. Herein, the silanization on the surface of hydroxylated barium titanate (BT-OH) nanoparticles was introduced by using two kinds of trialkoxysilane, 3-aminopropyltriethoxysilane (AMEO) and 3-aminopropyltrimethoxysilane (AMMO), with different solvents (toluene and ethanol), respectively. Solid-state 13 C, 29 Si nuclear magnetic resonance (NMR) spectroscopy and high-resolution X-ray photoelectron spectroscopy (XPS) were employed to validate the structure differences of alkoxysilane attachment to the nanoparticles. The effect of alkoxysilane structure attached to the nanoparticle surface on the dielectric properties of the BT based poly(vinylidene fluoride) (PVDF) nanocomposites were investigated. The results reveal that the solvents used for BT nanoparticle surface modification exhibit a significant effect on the breakdown strength of the nanocomposites. Nevertheless, the alkoxy groups of silane show a marginal influence on the dielectric properties of the nanocomposites. These research results provide

Titan Orbiter Aerorover Mission

Science.gov (United States)

Sittler Jr., E. C.; Acuna, M.; Burchell, M. J.; Coates, A.; Farrell, W.; Flasar, M.; Goldstein, B. E.; Gorevan, S.; Hartle, R. E.; Johnson, W. T. K.

2001-01-01

We propose a combined Titan orbiter and Titan Aerorover mission with an emphasis on both in situ and remote sensing measurements of Titan's surface, atmosphere, ionosphere, and magnetospheric interaction. The biological aspect of the Titan environment will be emphasized by the mission (i.e., search for organic materials which may include simple organics to 'amono' analogues of amino acids and possibly more complex, lightening detection and infrared, ultraviolet, and charged particle interactions with Titan's surface and atmosphere). An international mission is assumed to control costs. NASA will provide the orbiter, launch vehicle, DSN coverage and operations, while international partners will provide the Aerorover and up to 30% of the cost for the scientific instruments through collaborative efforts. To further reduce costs we propose a single PI for orbiter science instruments and a single PI for Aerorover science instruments. This approach will provide single command/data and power interface between spacecraft and orbiter instruments that will have redundant central DPU and power converter for their instruments. A similar approach could be used for the Aerorover. The mission profile will be constructed to minimize conflicts between Aerorover science, orbiter radar science, orbiter radio science, orbiter imaging science, and orbiter fields and particles (FP) science. Additional information is contained in the original extended abstract.

Titan AVIATR - Aerial Vehicle for In Situ and Airborne Titan Reconnaissance

Science.gov (United States)

Kattenhorn, Simon A.; Barnes, J. W.; McKay, C. P.; Lemke, L.; Beyer, R. A.; Radebaugh, J.; Adamkovics, M.; Atkinson, D. H.; Burr, D. M.; Colaprete, T.; Foch, R.; Le Mouélic, S.; Merrison, J.; Mitchell, J.; Rodriguez, S.; Schaller, E.

2010-10-01

Titan AVIATR - Aerial Vehicle for In Situ and Airborne Titan Reconnaissance - is a small (120 kg), nuclear-powered Titan airplane in the Discovery/New Frontiers class based on the concept of Lemke (2008 IPPW). The scientific goals of the mission are designed around the unique flexibility offered by an airborne platform: to explore Titan's diversity of surface landforms, processes, and compositions, as well as to study and measure the atmospheric circulation, aerosols, and humidity. AVIATR would address and surpass many of the science goals of hot-air balloons in Titan flagship studies. The strawman instrument payload is narrowly focused on the stated scientific objectives. The optical remote sensing suite comprises three instruments - an off-nadir high-resolution 2-micron camera, a horizon-looking 5-micron imager, and a 1-6 micron pushbroom near-infrared spectrometer. The in situ instruments include atmospheric structure, a methane humidity sensor, and a raindrop detector. An airplane has operational advantages over a balloon. Its piloted nature allows a go-to capability to image locations of interest in real time, thereby allowing for directed exploration of many features of primary geologic interest: Titan's sand dunes, mountains, craters, channels, and lakes. Subsequent imaging can capture changes in these features during the primary mission. AVIATR can fly predesigned routes, building up large context mosaics of areas of interest before swooping down to low altitude to acquire high-resolution images at 30-cm spatial sampling, similar to that of HiRISE at Mars. The elevation flexibility of the airplane allows us to acquire atmospheric profiles as a function of altitude at any desired location. Although limited by the direct-to-Earth downlink bandwidth, the total scientific data return from AVIATR will be >40 times that returned from Huygens. To maximize the science per bit, novel data storage and downlink techniques will be employed, including lossy compression

Titan's greenhouse and antigreenhouse effects

Science.gov (United States)

Mckay, Christopher P.; Pollack, James B.; Courtin, Regis

1992-01-01

Thermal mechanisms active in Titan's atmosphere are discussed in a brief review of data obtained during the Voyager I flyby in 1980. Particular attention is given to the greenhouse effect (GHE) produced by atmospheric H2, N2, and CH4; this GHE is stronger than that on earth, with CH4 and H2 playing roles similar to those of H2O and CO2 on earth. Also active on Titan is an antigreenhouse effect, in which dark-brown and orange organic aerosols block incoming solar light while allowing IR radiation from the Titan surface to escape. The combination of GHE and anti-GHE leads to a surface temperature about 12 C higher than it would be if Titan had no atmosphere.

Titan Orbiter with Aerorover Mission (TOAM)

Science.gov (United States)

Sittler, Edward C.; Cooper, J. F.; Mahaffey, P.; Esper, J.; Fairbrother, D.; Farley, R.; Pitman, J.; Kojiro, D. R.; TOAM Team

2006-12-01

We propose to develop a new mission to Titan called Titan Orbiter with Aerorover Mission (TOAM). This mission is motivated by the recent discoveries of Titan, its atmosphere and its surface by the Huygens Probe, and a combination of in situ, remote sensing and radar mapping measurements of Titan by the Cassini orbiter. Titan is a body for which Astrobiology (i.e., prebiotic chemistry) will be the primary science goal of any future missions to it. TOAM is planned to use an orbiter and balloon technology (i.e., aerorover). Aerobraking will be used to put payload into orbit around Titan. The Aerorover will probably use a hot air balloon concept using the waste heat from the MMRTG 500 watts. Orbiter support for the Aerorover is unique to our approach for Titan. Our strategy to use an orbiter is contrary to some studies using just a single probe with balloon. Autonomous operation and navigation of the Aerorover around Titan will be required, which will include descent near to the surface to collect surface samples for analysis (i.e., touch and go technique). The orbiter can provide both relay station and GPS roles for the Aerorover. The Aerorover will have all the instruments needed to sample Titan’s atmosphere, surface, possible methane lakes-rivers, use multi-spectral imagers for surface reconnaissance; to take close up surface images; take core samples and deploy seismometers during landing phase. Both active and passive broadband remote sensing techniques will be used for surface topography, winds and composition measurements.

Titan's Ammonia Feature

Science.gov (United States)

Smythe, W.; Nelson, R.; Boryta, M.; Choukroun, M.

2011-01-01

NH3 has long been considered an important component in the formation and evolution of the outer planet satellites. NH3 is particularly important for Titan, since it may serve as the reservoir for atmospheric nitrogen. A brightening seen on Titan starting in 2004 may arise from a transient low-lying fog or surface coating of ammonia. The spectral shape suggests the ammonia is anhydrous, a molecule that hydrates quickly in the presence of water.

Organic chemistry on Titan: Surface interactions

Science.gov (United States)

Thompson, W. Reid; Sagan, Carl

1992-01-01

The interaction of Titan's organic sediments with the surface (solubility in nonpolar fluids) is discussed. How Titan's sediments can be exposed to an aqueous medium for short, but perhaps significant, periods of time is also discussed. Interactions with hydrocarbons and with volcanic magmas are considered. The alteration of Titan's organic sediments over geologic time by the impacts of meteorites and comets is discussed.

AVIATR - Aerial Vehicle for In-situ and Airborne Titan Reconnaissance A Titan Airplane Mission Concept

Science.gov (United States)

Barnes, Jason W.; Lemke, Lawrence; Foch, Rick; McKay, Christopher P.; Beyer, Ross A.; Radebaugh, Jani; Atkinson, David H.; Lorenz, Ralph D.; LeMouelic, Stephane; Rodriguez, Sebastien;

TSSM: The in situ exploration of Titan

Science.gov (United States)

Coustenis, A.; Lunine, J. I.; Lebreton, J. P.; Matson, D.; Reh, K.; Beauchamp, P.; Erd, C.

2008-09-01

The Titan Saturn System Mission (TSSM) mission was born when NASA and ESA decided to collaborate on two missions independently selected by each agency: the Titan and Enceladus mission (TandEM), and Titan Explorer, a 2007 Flagship study. TandEM, the Titan and Enceladus mission, was proposed as an L-class (large) mission in response to ESA's Cosmic Vision 2015-2025 Call. The mission concept is to perform remote and in situ investigations of Titan primarily, but also of Enceladus and Saturn's magentosphere. The two satellites are tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini-Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TSSM will study Titan as a system, including its upper atmosphere, the interactions with the magnetosphere, the neutral atmosphere, surface, interior, origin and evolution, as well as the astrobiological potential of Titan. It is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini- Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time for Titan, several close flybys of Enceladus). One overarching goal of the TSSM mission is to explore in situ the atmosphere and surface of Titan. In the current mission architecture, TSSM consists of an orbiter (under NASA's responsibility) with a large host of instruments which would perform several Enceladus and Titan flybys before stabilizing in an orbit around Titan alone, therein delivering in situ elements (a Montgolfière, or hot air balloon, and a probe/lander). The latter are being studied by ESA. The balloon will circumnavigate Titan above the equator at an altitude of about 10 km for several months. The

Benzothiazole sulfide compatibilized polypropylene/halloysite nanotubes composites

Energy Technology Data Exchange (ETDEWEB)

Liu Mingxian [Department of Polymer Materials and Engineering, South China University of Technology, Guangzhou 510640 (China); Guo Baochun, E-mail: psbcguo@scut.edu.cn [Department of Polymer Materials and Engineering, South China University of Technology, Guangzhou 510640 (China); Lei Yanda; Du Mingliang; Jia Demin [Department of Polymer Materials and Engineering, South China University of Technology, Guangzhou 510640 (China)

2009-02-15

Clay-philic benzothiazole sulfide, capable of donating electrons, is grafted onto polypropylene (PP) backbones when N-cyclohexyl-2-benzothiazole sulfonamide (CBS), a commonly used accelerator in the tire industry, is included in the processing of PP/halloysite nanotubes (HNTs) composites. CBS decomposes at elevated temperature and yields benzothiazole sulfide radicals, which react with the PP polymeric free radicals generated during the processing of the composites. On the other hand, the benzothiazole group of CBS is reactive to HNTs via electron transferring. The compatibilization between HNTs and PP is thus realized via interfacial grafting and electron transferring mechanism. The interfacial interactions in the compatibilized systems were fully characterized. Compared with the control sample, the dispersion of HNTs and the interfacial bonding are enhanced substantially in the compatibilized composites. The significantly improved mechanical properties and thermal properties of benzothiazole sulfide compatibilized PP/HNTs composites are correlated to the enhanced interfacial property. The present work demonstrates a novel interfacial design via interfacial grafting/electron transferring for the compatibilization of PP/clay composites.

Diurnal variations of Titan

Science.gov (United States)

Cui, J.; Galand, M.; Yelle, R. V.; Vuitton, V.; Wahlund, J.-E.; Lavvas, P. P.; Mueller-Wodarg, I. C. F.; Kasprzak, W. T.; Waite, J. H.

2009-04-01

We present our analysis of the diurnal variations of Titan's ionosphere (between 1,000 and 1,400 km) based on a sample of Ion Neutral Mass Spectrometer (INMS) measurements in the Open Source Ion (OSI) mode obtained from 8 close encounters of the Cassini spacecraft with Titan. Though there is an overall ion depletion well beyond the terminator, the ion content on Titan's nightside is still appreciable, with a density plateau of ~700 cm-3 below ~1,300 km. Such a plateau is associated with the combination of distinct diurnal variations of light and heavy ions. Light ions (e.g. CH5+, HCNH+, C2H5+) show strong diurnal variation, with clear bite-outs in their nightside distributions. In contrast, heavy ions (e.g. c-C3H3+, C2H3CNH+, C6H7+) present modest diurnal variation, with significant densities observed on the nightside. We propose that the distinctions between light and heavy ions are associated with their different chemical loss pathways, with the former primarily through "fast" ion-neutral chemistry and the latter through "slow" electron dissociative recombination. The INMS data suggest day-to-night transport as an important source of ions on Titan's nightside, to be distinguished from the conventional scenario of auroral ionization by magnetospheric particles as the only ionizing source on the nightside. This is supported by the strong correlation between the observed night-to-day ion density ratios and the associated ion lifetimes. We construct a time-dependent ion chemistry model to investigate the effects of day-to-night transport on the ionospheric structures of Titan. The predicted diurnal variation has similar general characteristics to those observed, with some apparent discrepancies which could be reconciled by imposing fast horizontal thermal winds in Titan's upper atmosphere.

Amino acidis derived from Titan tholins

Science.gov (United States)

Khare, Bishun N.; Sagan, Carl; Ogino, Hiroshi; Nagy, Bartholomew; Er, Cevat

1986-01-01

The production of amino acids by acid treatment of Titan tholin is experimentally investigated. The synthesis of Titan tholin and the derivatization of amino acids to N-trifluoroacetyl isopropyl esters are described. The gas chromatography/mass spectroscopy analysis of the Titan tholins reveals the presence of glycine, alpha and beta alainine, and aspartic acid, and the total yield of amino acids is about 0.01.

Bismuth titanate nanorods and their visible light photocatalytic properties

International Nuclear Information System (INIS)

Pei, L.Z.; Liu, H.D.; Lin, N.; Yu, H.Y.

2015-01-01

Highlights: • Bismuth titanate nanorods have been synthesized by a simple hydrothermal process. • The size of bismuth titanate nanorods can be controlled by growth conditions. • Bismuth titanate nanorods show good photocatalytic activities of methylene blue and Rhodamine B. - Abstract: Bismuth titanate nanorods have been prepared using a facile hydrothermal process without additives. The bismuth titanate products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and UV-vis diffusion reflectance spectrum. XRD pattern shows that the bismuth titanate nanorods are composed of cubic Bi 2 Ti 2 O 7 phase. Electron microscopy images show that the length and diameter of the bismuth titanate nanorods are 50-200 nm and 2 μm, respectively. Hydrothermal temperature and reaction time play important roles on the formation and size of the bismuth titanate nanorods. UV-vis diffusion reflectance spectrum indicates that bismuth titanate nanorods have a band gap of 2.58 eV. The bismuth titanate nanorods exhibit good photocatalytic activities in the photocatalytic degradation of methylene blue (MB) and Rhodamine B (RB) under visible light irradiation. The bismuth titanate nanorods with cubic Bi 2 Ti 2 O 7 phase are a promising candidate as a visible light photocatalyst

Hubble Observes Surface of Titan

Science.gov (United States)

1994-01-01

Scientists for the first time have made images of the surface of Saturn's giant, haze-shrouded moon, Titan. They mapped light and dark features over the surface of the satellite during nearly a complete 16-day rotation. One prominent bright area they discovered is a surface feature 2,500 miles across, about the size of the continent of Australia.Titan, larger than Mercury and slightly smaller than Mars, is the only body in the solar system, other than Earth, that may have oceans and rainfall on its surface, albeit oceans and rain of ethane-methane rather than water. Scientists suspect that Titan's present environment -- although colder than minus 289 degrees Fahrenheit, so cold that water ice would be as hard as granite -- might be similar to that on Earth billions of years ago, before life began pumping oxygen into the atmosphere.Peter H. Smith of the University of Arizona Lunar and Planetary Laboratory and his team took the images with the Hubble Space Telescope during 14 observing runs between Oct. 4 - 18. Smith announced the team's first results last week at the 26th annual meeting of the American Astronomical Society Division for Planetary Sciences in Bethesda, Md. Co-investigators on the team are Mark Lemmon, a doctoral candidate with the UA Lunar and Planetary Laboratory; John Caldwell of York University, Canada; Larry Sromovsky of the University of Wisconsin; and Michael Allison of the Goddard Institute for Space Studies, New York City.Titan's atmosphere, about four times as dense as Earth's atmosphere, is primarily nitrogen laced with such poisonous substances as methane and ethane. This thick, orange, hydrocarbon haze was impenetrable to cameras aboard the Pioneer and Voyager spacecraft that flew by the Saturn system in the late 1970s and early 1980s. The haze is formed as methane in the atmosphere is destroyed by sunlight. The hydrocarbons produced by this methane destruction form a smog similar to that found over large cities, but is much thicker

A Dual Role of Graphene Oxide Sheet Deposition on Titanate Nanowire Scaffolds for Osteo-implantation: Mechanical Hardener and Surface Activity Regulator

Science.gov (United States)

Dong, Wenjun; Hou, Lijuan; Li, Tingting; Gong, Ziqiang; Huang, Huandi; Wang, Ge; Chen, Xiaobo; Li, Xiaoyun

2015-12-01

Scaffold biomaterials with open pores and channels are favourable for cell growth and tissue regeneration, however the inherent poor mechanical strength and low surface activity limit their applications as load-bearing bone grafts with satisfactory osseointegration. In this study, macro-porous graphene oxide (GO) modified titanate nanowire scaffolds with desirable surface chemistry and tunable mechanical properties were prepared through a simple hydrothermal process followed by electrochemical deposition of GO nanosheets. The interconnected and porous structure of the GO/titanate nanowire scaffolds provides a large surface area for cellular attachment and migration and displays a high compressive strength of approximately 81.1 MPa and a tunable Young’s modulus over the range of 12.4-41.0 GPa, which satisfies site-specific requirements for implantation. Surface chemistry of the scaffolds was modulated by the introduction of GO, which endows the scaffolds flexibility in attaching and patterning bioactive groups (such as -OH, -COOH and -NH2). In vitro cell culture tests suggest that the GO/titanate nanowire scaffolds act as a promising biomaterial candidate, in particular the one terminated with -OH groups, which demonstrates improved cell viability, and proliferation, differentiation and osteogenic activities.

The rotation of Titan and Ganymede

Science.gov (United States)

Van Hoolst, Tim; Coyette, Alexis; Baland, Rose-Marie; Trinh, Antony

2016-10-01

The rotation rates of Titan and Ganymede, the largest satellites of Saturn and Jupiter, are on average equal to their orbital mean motion. Here we discuss small deviations from the average rotation for both satellites and evaluate the polar motion of Titan induced by its surface fluid layers. We examine different causes at various time scales and assess possible consequences and the potential of using librations and polar motion as probes of the interior structure of the satellites.The rotation rate of Titan and Ganymede cannot be constant on the orbital time scale as a result of the gravitational torque of the central planet acting on the satellites. Titan is moreover expected to show significant polar motion and additional variations in the rotation rate due to angular momentum exchange with the atmosphere, mainly at seasonal periods. Observational evidence for deviations from the synchronous state has been reported several times for Titan but is unfortunately inconclusive. The measurements of the rotation variations are based on determinations of the shift in position of Cassini radar images taken during different flybys. The ESA JUICE (JUpiter ICy moons Explorer) mission will measure the rotation variations of Ganymede during its orbital phase around the satellite starting in 2032.We report on different theoretical aspects of the librations and polar motion. We consider the influence of the rheology of the ice shell and take into account Cassini measurements of the external gravitational field and of the topography of Titan and similar Galileo data about Ganymede. We also evaluate the librations and polar motion induced by Titan's hydrocarbon seas and use the most recent results of Titan's atmosphere dynamics. We finally evaluate the potential of rotation variations to constrain the satellite's interior structure, in particular its ice shell and ocean.

Future Exploration of Titan and Enceladus

Science.gov (United States)

Matson, D. L.; Coustenis, A.; Lunine, J.; Lebreton, J.; Reh, K.; Beauchamp, P.

2009-05-01

The future exploration of Titan and Enceladus has become very important for the planetary community. The study conducted last year of the Titan Saturn System Mission (TSSM) led to an announcement in which ESA and NASA prioritized future OPF missions, stating that TSSM is planned after EJSM (for details see http://www.lpi.usra.edu/opag/). TSSM consists of a TSSM Orbiter that would carry two in situ elements: the Titan Montgolfiere hot air balloon and the Titan Lake Lander. The mission could launch in the 2023-2025 timeframe on a trajectory to arrive ~9 years later for a 4-year mission in the Saturn system. Soon after arrival at Saturn, the montgolfiere would be delivered to Titan to begin its mission of airborne, scientific observations of Titan from an altitude of about 10 km. The montgolfiere would have a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) power system and would be designed to last at least 6-12 months in Titan's atmosphere. With the predicted winds and weather, that would be sufficient to circumnavigate the globe! On a subsequent fly-by, the TSSM orbiter would release the Lake Lander on a trajectory toward Titan for a targeted entry. It would descend through the atmosphere making scientific measurements, much like Huygens did, and then land and float on one of Titan's seas. This would be its oceanographic phase, making a physical and chemical assessment of the sea. The Lake Lander would operate 8-10 hours until its batteries become depleted. Following the delivery of the in situ elements, the TSSM orbiter would explore the Saturn system via a 2-year tour that includes in situ sampling of Enceladus' plumes as well as Titan flybys. After the Saturn system tour, the TSSM orbiter would enter orbit around Titan for a global survey phase. Synergistic and coordinated observations would be carried out between the TSSM orbiter and the in situ elements. The scientific requirements were developed by the international TSSM Joint Science Definition

Clash of the Titans

Science.gov (United States)

Subramaniam, Karthigeyan

2010-01-01

WebQuests and the 5E learning cycle are titans of the science classroom. These popular inquiry-based strategies are most often used as separate entities, but the author has discovered that using a combined WebQuest and 5E learning cycle format taps into the inherent power and potential of both strategies. In the lesson, "Clash of the Titans,"…

The electrochemical signature of functionalized single-walled carbon nanotubes bearing electroactive groups

International Nuclear Information System (INIS)

Le Floch, Fabien; Thuaire, Aurelie; Simonato, Jean-Pierre; Bidan, Gerard

2009-01-01

We report the modification and characterization of single-walled carbon nanotubes (SWCNTs) in view of molecular sensing applications. We found that ultrasonicated SWCNTs present sticking properties that make them adhere on electrode surfaces. This allows excellent characterization of SWCNTs by cyclic voltammetry (CV) before and after chemical functionalization with diazonium salts bearing electroactive groups. Bare SWCNTs presented distinct invariant shapes in CV, used as control curves, in comparison with functionalized SWCNTs for which specific signatures corresponding to the presence of grafted molecules were identified. According to the electronic substituents in the para position of the diazonium salts, divergent behaviours were observed for the grafting reactions. Diazonium salts having electrowithdrawing groups could be grafted without electrochemical induction whereas those bearing electron donating groups required a cathodic potential to generate the formation of the radical species.

The electrochemical signature of functionalized single-walled carbon nanotubes bearing electroactive groups

Energy Technology Data Exchange (ETDEWEB)

Le Floch, Fabien; Thuaire, Aurelie; Simonato, Jean-Pierre [LITEN/DTNM/LCRE, CEA-Grenoble 17 rue des Martyrs, 38054 Grenoble cedex 9 (France); Bidan, Gerard [INAC/DIR, CEA-Grenoble 17 rue des Martyrs, 38054 Grenoble cedex 9 (France)], E-mail: jean-pierre.simonato@cea.fr

2009-04-08

We report the modification and characterization of single-walled carbon nanotubes (SWCNTs) in view of molecular sensing applications. We found that ultrasonicated SWCNTs present sticking properties that make them adhere on electrode surfaces. This allows excellent characterization of SWCNTs by cyclic voltammetry (CV) before and after chemical functionalization with diazonium salts bearing electroactive groups. Bare SWCNTs presented distinct invariant shapes in CV, used as control curves, in comparison with functionalized SWCNTs for which specific signatures corresponding to the presence of grafted molecules were identified. According to the electronic substituents in the para position of the diazonium salts, divergent behaviours were observed for the grafting reactions. Diazonium salts having electrowithdrawing groups could be grafted without electrochemical induction whereas those bearing electron donating groups required a cathodic potential to generate the formation of the radical species.

Fabrication of 3D interconnected porous TiO{sub 2} nanotubes templated by poly(vinyl chloride-g-4-vinyl pyridine) for dye-sensitized solar cells

Energy Technology Data Exchange (ETDEWEB)

Koh, Joo Hwan; Koh, Jong Kwan; Seo, Jin Ah; Kim, Jong Hak [Department of Chemical and Biomolecular Engineering, Yonsei University, 262 Seongsanno, Seodaemun-gu, Seoul 120-749 (Korea, Republic of); Shin, Jong-Shik, E-mail: jonghak@yonsei.ac.kr [Department of Biotechnology, Yonsei University, 262 Seongsanno, Seodaemun-gu, Seoul 120-749 (Korea, Republic of)

2011-09-07

Porous TiO{sub 2} nanotube arrays with three-dimensional (3D) interconnectivity were prepared using a sol-gel process assisted by poly(vinyl chloride-graft-4-vinyl pyridine), PVC-g-P4VP graft copolymer and a ZnO nanorod template. A 7 {mu}m long ZnO nanorod array was grown from the fluorine-doped tin oxide (FTO) glass via a liquid phase deposition method. The TiO{sub 2} sol-gel solution templated by the PVC-g-P4VP graft copolymer produced a random 3D interconnection between the adjacent ZnO nanorods during spin coating. Upon etching of ZnO, TiO{sub 2} nanotubes consisting of 10-15 nm nanoparticles were generated, as confirmed by wide-angle x-ray scattering (WAXS), energy-filtering transmission electron microscopy (EF-TEM) and field-emission scanning electron microscopy (FE-SEM). The ordered and interconnected nanotube architecture showed an enhanced light scattering effect and increased penetration of polymer electrolytes in dye-sensitized solar cells (DSSC). The energy conversion efficiency reached 1.82% for liquid electrolyte, and 1.46% for low molecular weight (M{sub w}) and 0.74% for high M{sub w} polymer electrolytes.

TITAN'S TRANSPORT-DRIVEN METHANE CYCLE

International Nuclear Information System (INIS)

Mitchell, Jonathan L.

2012-01-01

The mechanisms behind the occurrence of large cloud outbursts and precipitation on Titan have been disputed. A global- and annual-mean estimate of surface fluxes indicated only 1% of the insolation, or ∼0.04 W m –2 , is exchanged as sensible and/or latent fluxes. Since these fluxes are responsible for driving atmospheric convection, it has been argued that moist convection should be quite rare and precipitation even rarer, even if evaporation globally dominates the surface-atmosphere energy exchange. In contrast, climate simulations indicate substantial cloud formation and/or precipitation. We argue that the top-of-atmosphere (TOA) radiative imbalance is diagnostic of horizontal heat transport by Titan's atmosphere, and thus constrains the strength of the methane cycle. Simple calculations show the TOA radiative imbalance is ∼0.5-1 W m –2 in Titan's equatorial region, which implies 2-3 MW of latitudinal heat transport by the atmosphere. Our simulation of Titan's climate suggests this transport may occur primarily as latent heat, with net evaporation at the equator and net accumulation at higher latitudes. Thus, the methane cycle could be 10-20 times previous estimates. Opposing seasonal transport at solstices, compensation by sensible heat transport, and focusing of precipitation by large-scale dynamics could further enhance the local, instantaneous strength of Titan's methane cycle by a factor of several. A limited supply of surface liquids in regions of large surface radiative imbalance may throttle the methane cycle, and if so, we predict more frequent large storms over the lakes district during Titan's northern summer.

Radiation stability of sodium titanate ion exchange materials

International Nuclear Information System (INIS)

Kenna, B.T.

1980-02-01

Sodium titanate and sodium titanate loaded macroreticular resin are being considered as ion exchangers to remove 90 Sr and actinides from the large volume of defense waste stored at Hanford Site in Washington. Preliminary studies to determine the radiation effect on Sr +2 and I - capacity of these ion-exchange materials were conducted. Samples of sodium titanate powder, sodium titanate loaded macroreticular resin, as well as the nitrate form of macroreticular anion resin were irradiated with up to 2 x 10 9 Rads of 60 Co gamma rays. Sodium titanate cation capacity decreased about 50% while the sodium titanate loaded macroeticular resin displayed a dramatic decrease in cation capacity when irradiated with 10 8 -10 9 Rad. The latter decrease is tentatively ascribed to radiation damage to the organic portion which subsequently inhibits interaction with the contained sodium titanate. The anion capacity of both macroreticular resin and sodium titanate loaded macroreticular resin exhibited significant decreases with increasing radiation exposure. These results suggest that consideration should be given to the potential effects of radiation degradation if column regeneration is to be used. 5 figures, 2 tables

Synthesis of photoactuating acrylic thermoplastic elastomers containing diblock copolymer-grafted carbon nanotubes

Czech Academy of Sciences Publication Activity Database

Ilčíková, M.; Mrlík, M.; Sedláček, T.; Šlouf, Miroslav; Zhigunov, Alexander; Koynov, K.; Mosnáček, J.

2014-01-01

Roč. 3, č. 10 (2014), s. 999-1003 ISSN 2161-1653 R&D Projects: GA TA ČR TE01020118 Institutional support: RVO:61389013 Keywords : photoactuating nanocomposite * carbon nanotubes * copolymer Subject RIV: CD - Macromolecular Chemistry Impact factor: 5.764, year: 2014

Chemical investigation of Titan and Triton tholins

Science.gov (United States)

Mcdonald, Gene D.; Thompson, W. R.; Heinrich, Michael; Khare, Bishun N.; Sagan, Carl

1994-01-01

We report chromatographic and spectroscopic analyses of both Titan and Triton tholins, organic solids made from the plasma irradiation of 0.9:0.1 and 0.999:0.001 N2/CH4 gas mixtures, respectively. The lower CH4 mixing ratio leads to a nitrogen-richer tholin (N/C greater than 1), probably including nitrogen heterocyclic compounds. Unlike Titan tholin, bulk Triton tholin is poor in nitriles. From high-pressure liquid chromatography, ultraviolet and infrared spectroscopy, and molecular weight estimation by gel filtration chromatography, we conclude that (1) several H2O-soluble fractions, each with distinct UV and IR spectral signatures, are present, (2) these fractions are not identical in the two tholins, (3) the H2O-soluble fractions of Titan tholins do not contain significant amounts of nitriles, despite the major role of nitriles in bulk Titan tholin, and (4) the H2O-soluble fractions of both tholins are mainly molcules containing about 10 to 50 (C + N) atoms. We report yields of amino acids upon hydrolysis of Titan and Triton tholins. Titan tholin is largely insoluble in the putative hydrocarbon lakes or oceans on Titan, but can yield the H2O-soluble species investigated here upon contact with transient (e.g., impact-generated) liquid water.

The synthesis and characterization of tributyl phosphate grafted carbon nano-tubes by the floating catalytic chemical vapor deposition method and their sorption behavior towards uranium

International Nuclear Information System (INIS)

Shruti Mishra; Jaya Dwivedi; Amar Kumar; Nalini Sankararamakrishnan

2016-01-01

Carbon nano-tubes (CNTs) were synthesized by the floating catalytic chemical vapor deposition technique using ferrocene in benzene as the hydrocarbon source. The functionalization of CNTs was carried out by oxidation (CNT-OX) and grafting with a tributyl phosphate (TBP) ligand (CNT-TBP). Various spectroscopic techniques including scanning electron microscopy (SEM), Fourier Transform Infra Red Spectroscopy (FTIR), BET surface area and X-ray photoelectron spectroscopy (XPS) were used to characterize the adsorbents. FTIR and XPS studies revealed the efficient grafting of the TBP ligand on the CNT surface. The effect of the initial pH and the contact time for the maximum adsorption of U(VI) with CNT-plain, CNT-OX and CNT-TBP was studied. The spontaneity of the sorption was confirmed by thermodynamic data. A pseudo second order model with a regression coefficient of ≥0.978 was obtained for CNT-TBP and equilibrium was reached within 3 h. The Langmuir maximum adsorption capacity of U(VI) at pH 5 for CNT, CNT-OX and CNT-TBP was found to be 66.6, 100.0 and 166.6 mg.g -1 respectively. Using 0.1 M HCl as a de-sorbent, recyclability studies were carried out for three cycles. The probable mechanism of adsorption between U(VI) and CNT-TBP could be understood through FTIR and XPS techniques. (authors)

The Exploration of Titan and the Saturnian System

Science.gov (United States)

Coustenis, Athena

The exploration of the outer solar system and in particular of the giant planets and their environments is an on-going process with the Cassini spacecraft currently around Saturn, the Juno mission to Jupiter preparing to depart and two large future space missions planned to launch in the 2020-2025 time frame for the Jupiter system and its satellites (Europa and Ganymede) on the one hand, and the Saturnian system and Titan on the other hand [1,2]. Titan, Saturn's largest satellite, is the only other object in our Solar system to possess an extensive nitrogen atmosphere, host to an active organic chemistry, based on the interaction of N2 with methane (CH4). Following the Voyager flyby in 1980, Titan has been intensely studied from the ground-based large telescopes (such as the Keck or the VLT) and by artificial satellites (such as the Infrared Space Observatory and the Hubble Space Telescope) for the past three decades. Prior to Cassini-Huygens, Titan's atmospheric composition was thus known to us from the Voyager missions and also through the explorations by the ISO. Our perception of Titan had thus greatly been enhanced accordingly, but many questions remained as to the nature of the haze surrounding the satellite and the composition of the surface. The recent revelations by the Cassini-Huygens mission have managed to surprise us with many discoveries [3-8] and have yet to reveal more of the interesting aspects of the satellite. The Cassini-Huygens mission to the Saturnian system has been an extraordinary success for the planetary community since the Saturn-Orbit-Insertion (SOI) in July 2004 and again the very successful probe descent and landing of Huygens on January 14, 2005. One of its main targets was Titan. Titan was revealed to be a complex world more like the Earth than any other: it has a dense mostly nitrogen atmosphere and active climate and meteorological cycles where the working fluid, methane, behaves under Titan conditions the way that water does on

Seasonal Changes in Titan's Meteorology

Science.gov (United States)

Turtle, E. P.; DelGenio, A. D.; Barbara, J. M.; Perry, J. E.; Schaller, E. L.; McEwen, A. S.; West, R. A.; Ray, T. L.

2011-01-01

The Cassini Imaging Science Subsystem has observed Titan for 1/4 Titan year, and we report here the first evidence of seasonal shifts in preferred locations of tropospheric methane clouds. South \\polar convective cloud activity, common in late southern summer, has become rare. North \\polar and northern mid \\latitude clouds appeared during the approach to the northern spring equinox in August 2009. Recent observations have shown extensive cloud systems at low latitudes. In contrast, southern mid \\latitude and subtropical clouds have appeared sporadically throughout the mission, exhibiting little seasonality to date. These differences in behavior suggest that Titan s clouds, and thus its general circulation, are influenced by both the rapid temperature response of a low \\thermal \\inertia surface and the much longer radiative timescale of Titan s cold thick troposphere. North \\polar clouds are often seen near lakes and seas, suggesting that local increases in methane concentration and/or lifting generated by surface roughness gradients may promote cloud formation. Citation

Maintenance procedures for the TITAN-I and TITAN-II reversed field pinch reactors

International Nuclear Information System (INIS)

Grotz, S.P.; Duggan, W.; Krakowski, R.; Najmabadi, F.; Wong, C.P.C.

1989-01-01

The TITAN reactor is a compact, high-power-density (neutron wall loading 18 MW/m 2 ) machine, based on the reversed-field-pinch (RFP) confinement concept. Two designs for the fusion power core have been examined: TITAN-I is based on a self-cooled lithium loop with a vanadium-alloy structure for the first wall, blanket and shield; and TITAN-II is based on an aqueous loop-in-pool design with a LiNO 3 solution as the coolant and breeder. The compact design of the TITAN fusion power core, (FPC) reduces the system to a few small and relatively low mass components, making toroidal segmentation of the FPC unnecessary. A single-piece maintenance procedure is possible. The potential advantages of single-piece maintenance procedures are: (1) Short period of down time; (2) improved reliability; (3) no adverse effects resulting from unequal levels of irradiation; and (4) ability to continually modify the FPC design. Increased availability can be expected from a fully pre-tested, single-piece FPC. Pre-testing of the FPC throughout the assembly process and prior to installation into the reactor vault is discussed. (orig.)

The tides of Titan.

Science.gov (United States)

Iess, Luciano; Jacobson, Robert A; Ducci, Marco; Stevenson, David J; Lunine, Jonathan I; Armstrong, John W; Asmar, Sami W; Racioppa, Paolo; Rappaport, Nicole J; Tortora, Paolo

2012-07-27

We have detected in Cassini spacecraft data the signature of the periodic tidal stresses within Titan, driven by the eccentricity (e = 0.028) of its 16-day orbit around Saturn. Precise measurements of the acceleration of Cassini during six close flybys between 2006 and 2011 have revealed that Titan responds to the variable tidal field exerted by Saturn with periodic changes of its quadrupole gravity, at about 4% of the static value. Two independent determinations of the corresponding degree-2 Love number yield k(2) = 0.589 ± 0.150 and k(2) = 0.637 ± 0.224 (2σ). Such a large response to the tidal field requires that Titan's interior be deformable over time scales of the orbital period, in a way that is consistent with a global ocean at depth.

Titan through Time: Evolution of Titan's Atmosphere and its Hydrocarbon Cycle on the Surface

Science.gov (United States)

Gilliam, Ashley E.

The Introduction and Appendix i-A outline briefly the history of Titan exploration since its discovery by Christiaan Huygens in 1675 through the recent International Mission of Cassini-Huygens.. Chapter 1: This chapter discusses two possible pathways of loss of the two main gases from Titan's post-accretional atmosphere, methane (CH 4) and ammonia (NH3), by the mechanisms of thermal escape and emission from the interior coupled with thermal escape. Chapter 2: In this chapter, a simple photolysis model is created, where the second most abundant component of the present-day Titan atmosphere, methane (CH4), can either escape the atmosphere or undergo photolytic conversion to ethane (C2H6). Chapter 3: This chapter examines different fluvial features on Titan, identified by the Cassini spacecraft, and evaluates the possibilities of channel formation by two mechanisms: dissolution of ice by a concentrated solution of ammonium sulfate, and by mechanical erosion by flow of liquid ammonia and liquid ethane. Chapter 4: This chapter presents: (1) new explicit mathematical solutions of mixed 1st and 2nd order chemical reactions, represented by ordinary differential first-degree and Riccati equations; (2) the computed present-day concentrations of the three gases in Titan's scale atmosphere, treated as at near-steady state; and (3) an analysis of the reported and computed atmospheric concentrations of CH4, CH 3, and C2H6 on Titan, based on the reaction rate parameters of the species, the rate parameters taken as constants representative of their mean values. Chapter 5: This chapter examines the possible reactions of methane formation in terms of the thermodynamic relationships of the reactions that include pure carbon as graphite, the gases H2, CO2, H2 O, and serpentinization and magnetite formation from olivine fayalite. (Abstract shortened by ProQuest.).

Interfacially enhancement of PBO/epoxy composites by grafting MWCNTs onto PBO surface through melamine as molecular bridge

Science.gov (United States)

Lv, Junwei; Wang, Bin; Ma, Qi; Wang, Wenjing; Xiang, Dong; Li, Mengyao; Zeng, Lan; Li, Hui; Li, Yuntao; Zhao, Chunxia

2018-06-01

Melamine and multi-walled carbon nanotubes (MWCNTs) were grafted onto Poly-p-phenylene benzobisoxazole (PBO) fiber surface effectively via layer-by-layer method. Both of them have been chemically bonded as fourier transform infrared spectroscopy (FTIR) confirmed. Grafting melamine overcame the inertness of PBO surface. Ammoniation was processed on PBO surface through grafting melamine so that the MWCNTs could be grafted onto PBO surface. Scanning electron microscopy (SEM) images indicated that melamine used as molecular bridge could increase MWCNTs’ quantity on PBO surface. X-ray photoelectron spectroscopy (XPS) results revealed the variation of chemical composition of PBO surface. Test of interfacial shear strength (IFSS) and tensile strength indicated the great mechanical properties of modified PBO fibers when combining with epoxy resin. Furthermore, whole reaction was processed under a simple condition. Results in this research also promised a potential method to modify PBO surface.

Recent advances in molecular electronics based on carbon nanotubes.

Science.gov (United States)

Bourgoin, Jean-Philippe; Campidelli, Stéphane; Chenevier, Pascale; Derycke, Vincent; Filoramo, Arianna; Goffman, Marcelo F

2010-01-01

Carbon nanotubes (CNTs) have exceptional physical properties that make them one of the most promising building blocks for future nanotechnologies. They may in particular play an important role in the development of innovative electronic devices in the fields of flexible electronics, ultra-high sensitivity sensors, high frequency electronics, opto-electronics, energy sources and nano-electromechanical systems (NEMS). Proofs of concept of several high performance devices already exist, usually at the single device level, but there remain many serious scientific issues to be solved before the viability of such routes can be evaluated. In particular, the main concern regards the controlled synthesis and positioning of nanotubes. In our opinion, truly innovative use of these nano-objects will come from: (i) the combination of some of their complementary physical properties, such as combining their electrical and mechanical properties, (ii) the combination of their properties with additional benefits coming from other molecules grafted on the nanotubes, and (iii) the use of chemically- or bio-directed self-assembly processes to allow the efficient combination of several devices into functional arrays or circuits. In this article, we outline the main issues concerning the development of carbon nanotubes based electronics applications and review our recent results in the field.

Titan LEAF: A Sky Rover Granting Targeted Access to Titan's Lakes and Plains

Science.gov (United States)

Ross, Floyd; Lee, Greg; Sokol, Daniel; Goldman, Benjamin; Bolisay, Linden

2016-10-01

Northrop Grumman, in collaboration with L'Garde Inc. and Global Aerospace Corporation (GAC), has been developing the Titan Lifting Entry Atmospheric Flight (T-LEAF) sky rover to roam the atmosphere and observe at close quarters the lakes and plains of Titan. T-LEAF also supports surface exploration and science by providing precision delivery of in situ instruments to the surface.T-LEAF is a maneuverable, buoyant air vehicle. Its aerodynamic shape provides its maneuverability, and its internal helium envelope reduces propulsion power requirements and also the risk of crashing. Because of these features, T-LEAF is not restricted to following prevailing wind patterns. This freedom of mobility allows it be commanded to follow the shorelines of Titan's methane lakes, for example, or to target very specific surface locations.T-LEAF utilizes a variable power propulsion system, from high power at ~200W to low power at ~50W. High power mode uses the propellers and control surfaces for additional mobility and maneuverability. It also allows the vehicle to hover over specific locations for long duration surface observations. Low power mode utilizes GAC's Titan Winged Aerobot (TWA) concept, currently being developed with NASA funding, which achieves guided flight without the use of propellers or control surfaces. Although slower than high powered flight, this mode grants increased power to science instruments while still maintaining control over direction of travel.Additionally, T-LEAF is its own entry vehicle, with its leading edges protected by flexible thermal protection system (f-TPS) materials already being tested by NASA's Hypersonic Inflatable Aerodynamic Decelerator (HIAD) group. This f-TPS technology allows T-LEAF to inflate in space, like HIAD, and then enter the atmosphere fully deployed. This approach accommodates entry velocities from as low as ~1.8 km/s if entering from Titan orbit, up to ~6 km/s if entering directly from Saturn orbit, like the Huygens probe

Characterizing the Upper Atmosphere of Titan using the Titan Global Ionosphere- Thermosphere Model: Nitrogen and Methane.

Science.gov (United States)

Bell, J. M.; Waite, J. H.; Bar-Nun, A.; Bougher, S. W.; Ridley, A. J.; Magee, B.

2008-12-01

Recently, a great deal of effort has been put forth to explain the Cassini Ion-Neutral Mass Spectrometer (Waite et al [2004]) in-situ measurements of Titan's upper atmosphere (e.g. Muller-Wodarg [2008], Strobel [2008], Yelle et al [2008]). Currently, the community seems to agree that large amounts of CH4 are escaping from Titan's upper atmosphere at a rate of roughly 2.0 x 1027 molecules of CH4/s (3.33 x 1028 amu/s), representing a significant mass source to the Kronian Magnetosphere. However, such large escape fluxes from Titan are currently not corroborated by measurements onboard the Cassini Spacecraft. Thus, we posit another potential scenario: Aerosol depletion of atmospheric methane. Using the three-dimensional Titan Global Ionosphere-Thermosphere Model (T-GITM) (Bell et al [2008]), we explore the possible removal mechanisms of atmospheric gaseous constituents by these aerosols. Titan simulations are directly compared against Cassini Ion-Neutral Mass Spectrometer in-situ densities of N2 and CH4. From this work, we can then compare and contrast this aerosol depletion scenario against the currently posited hydrodynamic escape scenario, illustrating the merits and shortcomings of both.

Diurnal variations of Titan's ionosphere

Science.gov (United States)

Cui, J.; Galand, M.; Yelle, R. V.; Vuitton, V.; Wahlund, J.-E.; Lavvas, P. P.; Müller-Wodarg, I. C. F.; Cravens, T. E.; Kasprzak, W. T.; Waite, J. H.

2009-06-01

We present our analysis of the diurnal variations of Titan's ionosphere (between 1000 and 1300 km) based on a sample of Ion Neutral Mass Spectrometer (INMS) measurements in the Open Source Ion (OSI) mode obtained from eight close encounters of the Cassini spacecraft with Titan. Although there is an overall ion depletion well beyond the terminator, the ion content on Titan's nightside is still appreciable, with a density plateau of ˜700 cm-3 below ˜1300 km. Such a plateau is a combined result of significant depletion of light ions and modest depletion of heavy ones on Titan's nightside. We propose that the distinctions between the diurnal variations of light and heavy ions are associated with their different chemical loss pathways, with the former primarily through “fast” ion-neutral chemistry and the latter through “slow” electron dissociative recombination. The strong correlation between the observed night-to-day ion density ratios and the associated ion lifetimes suggests a scenario in which the ions created on Titan's dayside may survive well to the nightside. The observed asymmetry between the dawn and dusk ion density profiles also supports such an interpretation. We construct a time-dependent ion chemistry model to investigate the effect of ion survival associated with solid body rotation alone as well as superrotating horizontal winds. For long-lived ions, the predicted diurnal variations have similar general characteristics to those observed. However, for short-lived ions, the model densities on the nightside are significantly lower than the observed values. This implies that electron precipitation from Saturn's magnetosphere may be an additional and important contributor to the densities of the short-lived ions observed on Titan's nightside.

Titan the earth-like moon

CERN Document Server

Coustenis, Athena

1999-01-01

This is the first book to deal with Titan, one of the most mysterious bodies in the solar system. The largest satellite of the giant planet Saturn, Titan is itself larger than the planet Mercury, and is unique in being the only known moon with a thick atmosphere. In addition, its atmosphere bears a startling resemblance to the Earth's, but is much colder.The American and European space agencies, NASA and ESA, have recently combined efforts to send a huge robot spacecraft to orbit Saturn and land on Titan. This book provides the background to this, the greatest deep space venture of our time, a

Titan and habitable planets around M-dwarfs.

Science.gov (United States)

Lunine, Jonathan I

2010-01-01

The Cassini-Huygens mission discovered an active "hydrologic cycle" on Saturn's giant moon Titan, in which methane takes the place of water. Shrouded by a dense nitrogen-methane atmosphere, Titan's surface is blanketed in the equatorial regions by dunes composed of solid organics, sculpted by wind and fluvial erosion, and dotted at the poles with lakes and seas of liquid methane and ethane. The underlying crust is almost certainly water ice, possibly in the form of gas hydrates (clathrate hydrates) dominated by methane as the included species. The processes that work the surface of Titan resemble in their overall balance no other moon in the solar system; instead, they are most like that of the Earth. The presence of methane in place of water, however, means that in any particular planetary system, a body like Titan will always be outside the orbit of an Earth-type planet. Around M-dwarfs, planets with a Titan-like climate will sit at 1 AU--a far more stable environment than the approximately 0.1 AU where Earth-like planets sit. However, an observable Titan-like exoplanet might have to be much larger than Titan itself to be observable, increasing the ratio of heat contributed to the surface atmosphere system from internal (geologic) processes versus photons from the parent star.

PEROXOTITANATE- AND MONOSODIUM METAL-TITANATE COMPOUNDS AS INHIBITORS OF BACTERIAL GROWTH

Energy Technology Data Exchange (ETDEWEB)

Hobbs, D.

2011-01-19

Sodium titanates are ion-exchange materials that effectively bind a variety of metal ions over a wide pH range. Sodium titanates alone have no known adverse biological effects but metal-exchanged titanates (or metal titanates) can deliver metal ions to mammalian cells to alter cell processes in vitro. In this work, we test a hypothesis that metal-titanate compounds inhibit bacterial growth; demonstration of this principle is one prerequisite to developing metal-based, titanate-delivered antibacterial agents. Focusing initially on oral diseases, we exposed five species of oral bacteria to titanates for 24 h, with or without loading of Au(III), Pd(II), Pt(II), and Pt(IV), and measuring bacterial growth in planktonic assays through increases in optical density. In each experiment, bacterial growth was compared with control cultures of titanates or bacteria alone. We observed no suppression of bacterial growth by the sodium titanates alone, but significant (p < 0.05, two-sided t-tests) suppression was observed with metal-titanate compounds, particularly Au(III)-titanates, but with other metal titanates as well. Growth inhibition ranged from 15 to 100% depending on the metal ion and bacterial species involved. Furthermore, in specific cases, the titanates inhibited bacterial growth 5- to 375-fold versus metal ions alone, suggesting that titanates enhanced metal-bacteria interactions. This work supports further development of metal titanates as a novel class of antibacterials.

Titan's geoid and hydrology: implications for Titan's geological evolution

Science.gov (United States)

Sotin, Christophe; Seignovert, Benoit; Lawrence, Kenneth; MacKenzie, Shannon; Barnes, Jason; Brown, Robert

2014-05-01

A 1x1 degree altitude map of Titan is constructed from the degree 4 gravity potential [1] and Titan's shape [2] determined by the Radio Science measurements and RADAR observations of the Cassini mission. The amplitude of the latitudinal altitude variations is equal to 300 m compared to 600 m for the amplitude of the latitudinal shape variations. The two polar caps form marked depressions with an abrupt change in topography at exactly 60 degrees at both caps. Three models are envisaged to explain the low altitude of the polar caps: (i) thinner ice crust due to higher heat flux at the poles, (ii) fossil shape acquired if Titan had higher spin rate in the past, and (iii) subsidence of the crust following the formation of a denser layer of clathrates as ethane rain reacts with the H2O ice crust [3]. The later model is favored because of the strong correlation between the location of the cloud system during the winter season and the latitude of the abrupt change in altitude. Low altitude polar caps would be the place where liquids would run to and eventually form large seas. Indeed, the large seas of Titan are found at the deepest locations at the North Pole. However, the lakes and terrains considered to be evaporite candidates due to their spectral characteristics in the infrared [4,5] seem to be perched. Lakes may have been filled during Titan's winter and then slowly evaporated leaving material on the surface. Interestingly, the largest evaporite deposits are located at the equator in a deep depression 150 m below the altitude of the northern seas. This observation seems to rule out the presence of a global subsurface hydrocarbon reservoir unless the evaporation rate at the equator is faster than the transport of fluids from the North Pole to the equator. This work has been performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. [1] Iess L. et al. (2012) Science, doi 10.1126/science.1219631. [2] Lorenz R.D. (2013

Single-Molecule Luminescence and High Efficiency Photovoltaic Cells Based on Percolated Conducting Carbon Nanotubes Scaffolds Templated with Light-Harvesting Conjugated Polymers and Nanohybrids

National Research Council Canada - National Science Library

Yang, Arnold C

2009-01-01

.... Nanocomposites constructed by surface-grafted multiwall carbon nanotubes (CNTs) with conjugated polymers dispersed in a polymer matrix were synthesized to form novel optoelectronic materials that exploit single-molecule effects...

Nonthermal atmospheric escape from Mars and Titan

International Nuclear Information System (INIS)

Lammer, H.; Bauer, S.J.

1991-01-01

Energy flux spectra and particle concentrations of the hot O and N coronae from Mars and Titan, respectively, resulting primarily from dissociative recombination of molecular ions, have been calculated by means of a Monte Carlo method. The calculated energy flux spectra lead to an escape flux null esc ∼ 6 x 10 6 cm -2 s -1 for Mars and null esc ∼ 2 x 10 6 cm -2 s -1 for Titan, corresponding to a mass loss of about 0.14 kg/s for Mars and about 0.3 kg/s for Titan. (The contribution of electron impact ionization on N 2 amounts to only about 25% of Titan's mass loss.) Mass loss via solar and magnetospheric wind is also estimated using newly calculated mass loading limits. The mass loss via ion pickup from the extended hot atom corona for Mars amounts to about 0.25 kg/s (O + ) and for Titan to about 50 g/s (N 2 + or H 2 CN + ). Thus, the total mass loss rate from Mars and Titan is about the same, i.e., 0.4 kg/s

A whiff of nebular gas in Titan's atmosphere - Potential implications for the conditions and timing of Titan's formation

Science.gov (United States)

Glein, Christopher R.

2017-09-01

In situ data from the GCMS instrument on the Huygens probe indicate that Titan's atmosphere contains small amounts of the primordial noble gases 36Ar and 22Ne (tentative detection), but it is unknown how they were obtained by the satellite. Based on the apparent similarity in the 22Ne/36Ar (atom) ratio between Titan's atmosphere and the solar composition, a previously neglected hypothesis for the origin of primordial noble gases in Titan's atmosphere is suggested - these species may have been acquired near the end of Titan's formation, when the moon could have gravitationally captured some nebular gas that would have been present in its formation environment (the Saturnian subnebula). These noble gases may be remnants of a primary atmosphere. This could be considered the simplest hypothesis to explain the 22Ne/36Ar ratio observed at Titan. However, the 22Ne/36Ar ratio may not be exactly solar if these species can be fractionated by external photoevaporation in the solar nebula, atmospheric escape from Titan, or sequestration on the surface of Titan. While the GCMS data are consistent with a 22Ne/36Ar ratio of 0.05 to 2.5 times solar (1σ range), simple estimates that attempt to account for some of the effects of these evolutionary processes suggest a sub-solar ratio, which may be depleted by approximately one order of magnitude. Models based on capture of nebular gas can explain why the GCMS did not detect any other primordial noble gas isotopes, as their predicted abundances are below the detection limits (especially for 84Kr and 132Xe). It is also predicted that atmospheric Xe on Titan should be dominated by radiogenic 129Xe if the source of primordial Xe is nebular gas. Of order 10-2-10-1 bar of primordial H2 may have been captured along with the noble gases from a gas-starved disk, but this H2 would have quickly escaped from the initial atmosphere. To have the opportunity to capture nebular gas, Titan should have formed within ∼10 Myr of the formation of the

Coupled atmosphere-ocean models of Titan's past

Science.gov (United States)

Mckay, Christopher P.; Pollack, James B.; Lunine, Jonathan I.; Courtin, Regis

1993-01-01

The behavior and possible past evolution of fully coupled atmosphere and ocean model of Titan are investigated. It is found that Titan's surface temperature was about 20 K cooler at 4 Gyr ago and will be about 5 K warmer 0.5 Gyr in the future. The change in solar luminosity and the conversion of oceanic CH4 to C2H6 drive the evolution of the ocean and atmosphere over time. Titan appears to have experienced a frozen epoch about 3 Gyr ago independent of whether an ocean is present or not. This finding may have important implications for understanding the inventory of Titan's volatile compounds.

Effects of Titanium Mesh Surfaces-Coated with Hydroxyapatite/β-Tricalcium Phosphate Nanotubes on Acetabular Bone Defects in Rabbits

Directory of Open Access Journals (Sweden)

Thuy-Duong Thi Nguyen

2017-07-01

Full Text Available The management of severe acetabular bone defects in revision reconstructive orthopedic surgery is challenging. In this study, cyclic precalcification (CP treatment was used on both nanotube-surface Ti-mesh and a bone graft substitute for the acetabular defect model, and its effects were assessed in vitro and in vivo. Nanotube-Ti mesh coated with hydroxyapatite/β-tricalcium phosphate (HA/β-TCP was manufactured by an anodizing and a sintering method, respectively. An 8 mm diameter defect was created on each acetabulum of eight rabbits, then treated by grafting materials and covered by Ti meshes. At four and eight weeks, postoperatively, biopsies were performed for histomorphometric analyses. The newly-formed bone layers under cyclic precalcified anodized Ti (CP-AT meshes were superior with regard to the mineralized area at both four and eight weeks, as compared with that under untreated Ti meshes. Active bone regeneration at 2–4 weeks was stronger than at 6–8 weeks, particularly with treated biphasic ceramic (p < 0.05. CP improved the bioactivity of Ti meshes and biphasic grafting materials. Moreover, the precalcified nanotubular Ti meshes could enhance early contact bone formation on the mesh and, therefore, may reduce the collapse of Ti meshes into the defect, increasing the sufficiency of acetabular reconstruction. Finally, cyclic precalcification did not affect bone regeneration by biphasic grafting materials in vivo.

Dispersing surface-modified imogolite nanotubes in polar and non-polar solvents

Science.gov (United States)

Li, Ming; Brant, Jonathan A.

2018-02-01

Furthering the development of nanocomposite structures, namely membranes for water treatment applications, requires that methods be developed to ensure nanoparticle dispersion in polar and non-polar solvents, as both are widely used in associated synthesis techniques. Here, we report on a two-step method to graft polyvinylpyrrolidone (PVP), and a one-step method for octadecylphosphonic acid (OPA), onto the outer surfaces of imogolite nanotubes. The goal of these approaches was to improve and maintain nanotube dispersion in polymer compatible polar and non-polar solvents. The PVP coating modified the imogolite surface charge from positive to weakly negative at pH ≤ 9; the OPA made it weakly positive at acidic pH values to negative at pH ≥ 7. The PVP surface coating stabilized the nanotubes through steric hindrance in polar protic, dipolar aprotic, and chloroform. In difference to the PVP, the OPA surface coating allowed the nanotubes to be dispersed in n-hexane and chloroform, but not in the polar solvents. The lack of miscibility in the polar solvents, as well as the better dispersion in n-hexane, was attributed to the stronger hydrophobicity of the OPA polymer relative to the PVP. [Figure not available: see fulltext.

Control of Polymer Nanostructure and Functionality via Radiation Grafting

International Nuclear Information System (INIS)

Palmese, G.R.

2006-01-01

Radiation grafting provides a useful means for controlling polymer structure and performance. Particularly, it is appropriate for combining materials with distinct thermodynamic characteristics chemically at interfaces. Therefore polymeric materials that generally will not mix - i.e hydrophilic and hydrophobic polymers - can be combined efficiently using radiation based methods. This is of particular importance when attempting to form polymer-polymer nanocomposites where the thermodynamic penalty associated with high specific interfacial surface area is very large. Generally, the combination at small scales of such distinct materials is appropriate when specific functionality is desired while maintaining structural performance characteristics. In such cases the hydrophilic polymer lends functional characteristics such as ionic conductivity, self-healing, and actuation, while the hydrophobic polymer component provides structural stability. In this communication a summary of our recent work concerning the use of radiation grafting for the synthesis of nanostructured functional materials is given. Examples to be discussed include toughing of polymeric systems, the synthesis polymeric and inorganic nanotubes, and the design of permeation selective membranes. These examples will be used to demonstrate the effectiveness of radiation grafting techniques for controlling polymer properties and small-scale structure

Titan atmospheric composition by hypervelocity shock layer analysis

International Nuclear Information System (INIS)

Nelson, H.F.; Park, C.; Whiting, E.E.

1989-01-01

The Cassini Mission, a NASA/ESA cooperative project which includes a deployment of probe into the atmosphere of Titan, is described, with particular attention given to the shock radiometer experiment planned for the Titan probe for the analysis of Titan's atmosphere. Results from a shock layer analysis are presented, demonstrating that the mole fractions of the major species (N2, CH4, and, possibly Ar) in the Titan atmosphere can be successfully determined by the Titan-probe radiometer, by measuring the intensity of the CN(violet) radiation emitted in the shock layer during the high velocity portion of the probe entry between 200 and 400 km altitude. It is shown that the sensitivity of the CN(violet) radiation makes it possible to determine the mole fractions of N2, CH4, and Ar to about 0.015, 0.003, and 0.01, respectively, i.e., much better than the present uncertainties in the composition of Titan atmosphere. 29 refs

Ceria and strontium titanate based electrodes

DEFF Research Database (Denmark)

2010-01-01

A ceramic anode structure obtainable by a process comprising the steps of: (a) providing a slurry by dispersing a powder of an electronically conductive phase and by adding a binder to the dispersion, in which said powder is selected from the group consisting of niobium-doped strontium titanate......, vanadium-doped strontium titanate, tantalum-doped strontium titanate, and mixtures thereof, (b) sintering the slurry of step (a), (c) providing a precursor solution of ceria, said solution containing a solvent and a surfactant, (d) impregnating the resulting sintered structure of step (b...

Hybrid membrane using polyethersulfone-modification of multiwalled carbon nanotubes with silane agent to enhance high performance oxygen separation

Directory of Open Access Journals (Sweden)

Tutuk Djoko Kusworo

2014-04-01

Full Text Available Mixed matrix membrane comprising carbon nanotubes embedded in polymer matrix have become one of the emerging technologies. This study was investigated in order to study the effect of silane agent modification towards carbon nanotubes (CNT surface at different concentration on oxygen enrichment performances of asymmetric mixed matrix membrane. The modified carbon nanotubes were prepared by treating the carbon nanotubes with chemical modification using Dynasylan Ameo (DA silane agent to allow PES chains to be grafted on carbon nanotubes surface. The results from the FESEM, DSC and FTIR analysis confirmed that chemical modification on carbon nanotubes surface had taken place. Sieve-in-a-cage’ morphology observed shows the poor adhesion between polymer and unmodified CNT. The gas separation performance of the asymmetric flat sheet mixed matrix membranes with modified CNT were relatively higher compared to the unmodified CNT. Hence, coated hollow fiber mixed matrix membrane with chemical modification on CNT surface using (3-aminopropyl-triethoxy methyl silane agent can potentially enhance the gas separation performance of O2 and N2.

Molecular structures of (3-aminopropyl)trialkoxysilane on hydroxylated barium titanate nanoparticle surfaces induced by different solvents and their effect on electrical properties of barium titanate based polymer nanocomposites

Science.gov (United States)

Fan, Yanyan; Wang, Guanyao; Huang, Xingyi; Bu, Jing; Sun, Xiaojin; Jiang, Pingkai

2016-02-01

Surface modification of nanoparticles by grafting silane coupling agents has proven to be a significant approach to improve the interfacial compatibility between inorganic filler and polymer matrix. However, the impact of grafted silane molecular structure after the nanoparticle surface modification, induced by the utilized solvents and the silane alkoxy groups, on the electrical properties of the corresponding nanocomposites, has been seldom investigated. Herein, the silanization on the surface of hydroxylated barium titanate (BT-OH) nanoparticles was introduced by using two kinds of trialkoxysilane, 3-aminopropyltriethoxysilane (AMEO) and 3-aminopropyltrimethoxysilane (AMMO), with different solvents (toluene and ethanol), respectively. Solid-state 13C, 29Si nuclear magnetic resonance (NMR) spectroscopy and high-resolution X-ray photoelectron spectroscopy (XPS) were employed to validate the structure differences of alkoxysilane attachment to the nanoparticles. The effect of alkoxysilane structure attached to the nanoparticle surface on the dielectric properties of the BT based poly(vinylidene fluoride) (PVDF) nanocomposites were investigated. The results reveal that the solvents used for BT nanoparticle surface modification exhibit a significant effect on the breakdown strength of the nanocomposites. Nevertheless, the alkoxy groups of silane show a marginal influence on the dielectric properties of the nanocomposites. These research results provide important insights into the fabrication of advanced polymer nanocomposites for dielectric applications.

Anion and cation diffusion in barium titanate and strontium titanate

International Nuclear Information System (INIS)

Kessel, Markus Franz

2012-01-01

Perovskite oxides show various interesting properties providing several technical applications. In many cases the defect chemistry is the key to understand and influence the material's properties. In this work the defect chemistry of barium titanate and strontium titanate is analysed by anion and cation diffusion experiments and subsequent time-of-flight secondary ion mass spectrometry (ToF-SIMS). The reoxidation equation for barium titanate used in multi-layer ceramic capacitors (MLCCs) is found out by a combination of different isotope exchange experiments and the analysis of the resulting tracer diffusion profiles. It is shown that the incorporation of oxygen from water vapour is faster by orders of magnitude than from molecular oxygen. Chemical analysis shows the samples contain various dopants leading to a complex defect chemistry. Dysprosium is the most important dopant, acting partially as a donor and partially as an acceptor in this effectively acceptor-doped material. TEM and EELS analysis show the inhomogeneous distribution of Dy in a core-shell microstructure. The oxygen partial pressure and temperature dependence of the oxygen tracer diffusion coefficients is analysed and explained by the complex defect chemistry of Dy-doped barium titanate. Additional fast diffusion profiles are attributed to fast diffusion along grain boundaries. In addition to the barium titanate ceramics from an important technical application, oxygen diffusion in cubic, nominally undoped BaTiO 3 single crystals has been studied by means of 18 O 2 / 16 O 2 isotope exchange annealing and subsequent determination of the isotope profiles in the solid by ToF-SIMS. It is shown that a correct description of the diffusion profiles requires the analysis of the diffusion through the surface space-charge into the material's bulk. Surface exchange coefficients, space-charge potentials and bulk diffusion coefficients are analysed as a function of oxygen partial pressure and temperature. The

Functionalization of super-aligned carbon nanotube film using hydrogen peroxide solution and its application in copper electrodeposition.

Science.gov (United States)

Xiong, Lunqiao; Shuai, Jing; Hou, Zecheng; Zhu, Lin; Li, Wenzhen

2017-07-15

In order to make super-aligned carbon nanotubes (SACNT) homogeneously spread in electrolytes, a swift and effective method was devised for surface functionalization of SACNT film by ohmic heating using hydrogen peroxide solution. Controllable generation of defects and notable graft of oxygen functional groups on the sidewall of SACNTs were induced as proven by X-ray photoelectron spectroscopy and Raman spectroscopy. Differently from the harsh wet chemical oxidation, the super-aligned morphology and structural integrity of carbon nanotubes in the SACNT film were found to be well preserved by electron microscopy analysis. The functionalized treatment can remove extraneous material contaminating SACNT film and improve its conductivity. The grafting of polar ionizable groups has been proved to effectively eliminate the agglomeration of SACNTs. When the oxidized SACNT film was used as host material for electrodeposition of copper, the composite film of well-bonded SACNTs and Cu was successfully prepared. Copyright © 2017 Elsevier Inc. All rights reserved.

Titan's methane clock

Science.gov (United States)

Nixon, C. A.; Jennings, D. E.; Romani, P. N.; Teanby, N. A.; Irwin, P. G. J.; Flasar, F. M.

2010-04-01

Measurements of the 12C/13C and D/H isotopic ratios in Titan's methane show intriguing differences from the values recorded in the giant planets. This implies that either (1) the atmosphere was differently endowed with material at the time of formation, or (2) evolutionary processes are at work in the moon's atmosphere - or some combination of the two. The Huygens Gas Chromatograph Mass Spectrometer Instrument (GCMS) found 12CH4/13CH4 = 82 +/- 1 (Niemann et al. 2005), some 7% lower than the giant planets' value of 88 +/- 7 (Sada et al. 1996), which closely matches the terrestrial inorganic standard of 89. The Cassini Composite Infrared Spectrometer (CIRS) has previously reported 12CH4/13CH4 of 77 +/-3 based on nadir sounding, which we now revise upwards to 80 +/- 4 based on more accurate limb sounding. The CIRS and GCMS results are therefore in agreement about an overall enrichment in 13CH4 of ~10%. The value of D/H in Titan's CH4 has long been controversial: historical measurements have ranged from about 8-15 x 10-5 (e.g. Coustenis et al. 1989, Coustenis et al. 2003). A recent measurement based on CIRS limb data by Bezard et al. (2007) puts the D/H in CH4 at (13 +/- 1) x 10-5, very much greater than in Jupiter and Saturn, ~2 x 10-5 (Mahaffy et al. 1998, Fletcher et al. 2009). To add complexity, the 12C/13C and D/H vary among molecules in Titan atmosphere, typically showing enhancement in D but depletion in 13C in the daughter species (H2, C2H2, C2H6), relative to the photochemical progenitor, methane. Jennings et al. (2009) have sought to interpret the variance in carbon isotopes as a Kinetic Isotope Effect (KIE), whilst an explanation for the D/H in all molecules remains elusive (Cordier et al. 2008). In this presentation we argue that evolution of isotopic ratios in Titan's methane over time forms a ticking 'clock', somewhat analogous to isotopic ratios in geochronology. Under plausible assumptions about the initial values and subsequent replenishment, various

Titan Orbiter Aerorover Mission with Enceladus Science (TOAMES)

Science.gov (United States)

Sittler, E.; Cooper, J.; Mahaffy, P.; Fairbrother, D.; de Pater, I.; Schulze-Makuch, D.; Pitman, J.

2007-08-01

same time made us aware of how little we understand about these bodies. For example, the source, and/or recycling mechanism, of methane in Titan's atmosphere is still puzzling. Indeed, river beds (mostly dry) and lakes have been spotted, and occasional clouds have been seen, but the physics to explain the observations is still mostly lacking, since our "image" of Titan is still sketchy and quite incomplete. Enceladus, only 500 km in extent, is even more puzzling, with its fiery plumes of vapor, dust and ice emanating from its south polar region, "feeding" Saturn's E ring. Long term variability of magnetospheric plasma, neutral gas, E-ring ice grain density, radio emissions, and corotation of Saturn's planetary magnetic field in response to Enceladus plume activity are of great interest for Saturn system science. Both Titan and Enceladus are bodies of considerable astrobiological interest in view of high organic abundances at Titan and potential subsurface liquid water at Enceladus. We propose to develop a new mission to Titan and Enceladus, the Titan Orbiter Aerorover Mission with Enceladus Science (TOAMES), to address these questions using novel new technologies. TOAMES is a multi-faceted mission that starts with orbit insertion around Saturn using aerobraking with Titan's extended atmosphere. We then have an orbital tour around Saturn (for 1-2 years) and close encounters with Enceladus, before it goes into orbit around Titan (via aerocapture). During the early reconnaissance phase around Titan, perhaps 6 months long, the orbiter will use altimetry, radio science and remote sensing instruments to measure Titan's global topography, subsurface structure and atmospheric winds. This information will be used to determine where and when to release the Aerorover, so that it can navigate safely around Titan and identify prime sites for surface sampling and analysis. In situ instruments will sample the upper atmosphere which may provide the seed population for the complex

Spacecraft Exploration of Titan and Enceladus

Science.gov (United States)

Matson, D.; Coustenis, A.; Lunine, J. I.; Lebreton, J.; Reh, K.; Beauchamp, P.; Erd, C.

2009-12-01

The future exploration of Titan and Enceladus is very important for planetary science. The study titled Titan Saturn System Mission (TSSM) led to an announcement in which ESA and NASA prioritized future OPF missions, stating that TSSM is planned after EJSM (for details see http://www.lpi.usra.edu/opag/). The TSSM concept consists of an Orbiter that would carry two in situ elements: the Titan Montgolfiere hot air balloon and the Titan Lake Lander. This mission could launch in the 2023-2025 timeframe on a trajectory to arrive ~9 years later and begin a 4-year mission in the Saturnian system. At an appropriate time after arrival at Saturn, the montgolfiere would be delivered to Titan to begin its mission of airborne, scientific observations of Titan from an altitude of about 10 km above the surface. The montgolfiere would have a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) power system whose waste heat would warm the gas in the balloon, providing buoyancy. It would be designed to survive at least 6-12 months in Titan’s atmosphere. With the predicted winds and weather, it should be possible to circumnavigate the globe! Later, on a subsequent fly-by, the TSSM orbiter would send the Lake Lander to Titan. It would descend through the atmosphere making scientific measurements, much like Huygens did, and then land and float on one of Titan’s seas. This would be its oceanographic phase of making a physical and chemical assessment of the sea. The Lake Lander would operate for 8-10 hours until its batteries become depleted. Following the delivery of the in situ elements, the TSSM orbiter would then explore the Saturn system for two years on a tour that includes in situ sampling of Enceladus’ plumes as well as flybys of Titan. After the Saturn tour, the TSSM orbiter would go into orbit around Titan and carry out a global survey phase. Synergistic observations would be carried out by the TSSM orbiter and the in situ elements. The scientific requirements for

Strategically functionalized carbon nanotubes as the ultrasensitive electrochemical probe for picomolar detection of sildenafil citrate (Viagra).

Science.gov (United States)

Gopalan, Anantha Iyengar; Lee, Kwang Pill; Komathi, Shanmugasundaram

2011-02-15

The present work demonstrates the utility of the functionalized carbon nanotubes, poly(4-aminobenzene sulfonic acid) (PABS) grafted multiwalled carbon nanotubes, MWNT-g-PABS, as an electrode modifier towards achieving ultrasensitive detection of a model drug, sildenafil citrate (SC). PABS units in MWNT-g-PABS interact with SC, pre-concentrate and accumulate at the surface. The electron transduction from SC to electrode is augmented via MWNT-g-PABS. As a result, the MWNT-g-PABS modified electrode exhibited ultrasensitive (57.7 μA/nM) and selective detection of SC with a detection limit of 4.7 pM. The present work provides scope towards targeting ultrasensitivity for the detection of biomolecules/drug through rational design and incorporation of appropriate chemical components to carbon nanotubes. Copyright © 2010 Elsevier B.V. All rights reserved.

Multistep structural transition of hydrogen trititanate nanotubes into TiO2-B nanotubes: a comparison study between nanostructured and bulk materials

International Nuclear Information System (INIS)

Morgado, Edisson Jr; Jardim, P M; Marinkovic, Bojan A; Rizzo, Fernando C; Abreu, Marco A S de; Zotin, Jose L; Araujo, Antonio S

2007-01-01

H-trititanate nanotubes obtained by alkali hydrothermal treatment of TiO 2 followed by proton exchange were compared to their bulk H 2 Ti 3 O 7 counterpart with respect to their thermally induced structural transformation paths. As-synthesized and heat-treated samples were characterized by XRD, TEM/SAED, DSC and spectroscopy techniques, indicating that H 2 Ti 3 O 7 nanotubes showed the same sequence of structural transformations as their bulk counterpart obtained by conventional solid state reaction. Nanostructured H 2 Ti 3 O 7 converts into TiO 2 (B) via multistep transformation without losing its nanotubular morphology. The transformation occurs between 120 and 400 deg. C through topotactic mechanisms with the intermediate formation of nanostructured H 2 Ti 6 O 13 and H 2 Ti 12 O 25 , which are more condensed layered titanates eventually rearranging to TiO 2 (B). Our results suggest that the intermediate tunnel structure H 2 Ti 12 O 25 is the final layered intermediate phase, on which TiO 2 (B) nucleates and grows. The conversion of nanostructured TiO 2 (B) into anatase is completed at a much lower temperature than its bulk counterpart and is accompanied by loss of the nanotubular morphology

Multistep structural transition of hydrogen trititanate nanotubes into TiO2-B nanotubes: a comparison study between nanostructured and bulk materials.

Science.gov (United States)

Morgado, Edisson; Jardim, P M; Marinkovic, Bojan A; Rizzo, Fernando C; de Abreu, Marco A S; Zotin, José L; Araújo, Antonio S

2007-12-12

H-trititanate nanotubes obtained by alkali hydrothermal treatment of TiO(2) followed by proton exchange were compared to their bulk H(2)Ti(3)O(7) counterpart with respect to their thermally induced structural transformation paths. As-synthesized and heat-treated samples were characterized by XRD, TEM/SAED, DSC and spectroscopy techniques, indicating that H(2)Ti(3)O(7) nanotubes showed the same sequence of structural transformations as their bulk counterpart obtained by conventional solid state reaction. Nanostructured H(2)Ti(3)O(7) converts into TiO(2)(B) via multistep transformation without losing its nanotubular morphology. The transformation occurs between 120 and 400 degrees C through topotactic mechanisms with the intermediate formation of nanostructured H(2)Ti(6)O(13) and H(2)Ti(12)O(25), which are more condensed layered titanates eventually rearranging to TiO(2)(B). Our results suggest that the intermediate tunnel structure H(2)Ti(12)O(25) is the final layered intermediate phase, on which TiO(2)(B) nucleates and grows. The conversion of nanostructured TiO(2)(B) into anatase is completed at a much lower temperature than its bulk counterpart and is accompanied by loss of the nanotubular morphology.

Multistep structural transition of hydrogen trititanate nanotubes into TiO2-B nanotubes: a comparison study between nanostructured and bulk materials

Science.gov (United States)

Morgado, Edisson, Jr.; Jardim, P. M.; Marinkovic, Bojan A.; Rizzo, Fernando C.; de Abreu, Marco A. S.; Zotin, José L.; Araújo, Antonio S.

2007-12-01

H-trititanate nanotubes obtained by alkali hydrothermal treatment of TiO2 followed by proton exchange were compared to their bulk H2Ti3O7 counterpart with respect to their thermally induced structural transformation paths. As-synthesized and heat-treated samples were characterized by XRD, TEM/SAED, DSC and spectroscopy techniques, indicating that H2Ti3O7 nanotubes showed the same sequence of structural transformations as their bulk counterpart obtained by conventional solid state reaction. Nanostructured H2Ti3O7 converts into TiO2(B) via multistep transformation without losing its nanotubular morphology. The transformation occurs between 120 and 400 °C through topotactic mechanisms with the intermediate formation of nanostructured H2Ti6O13 and H2Ti12O25, which are more condensed layered titanates eventually rearranging to TiO2(B). Our results suggest that the intermediate tunnel structure H2Ti12O25 is the final layered intermediate phase, on which TiO2(B) nucleates and grows. The conversion of nanostructured TiO2(B) into anatase is completed at a much lower temperature than its bulk counterpart and is accompanied by loss of the nanotubular morphology.

Morphology and Properties of Aminosilane Grafted MWCNT/Polyimide Nanocomposites

Directory of Open Access Journals (Sweden)

Siu-Ming Yuen

2008-01-01

Full Text Available This investigation presents a novel method for modifying multiwalled carbon nanotubes (MWCNTs. The morphology, electrical resistivity, and percolation threshold of MWCNT/Polyimide nanocomposites were studied. Acid-modified MWCNTs reacted with (3-aminopropyltriethoxysilane by ionic bonding, and were then mixed with polyamic acid via imidization. TEM microphotographs reveal that silane-grafted MWCNTs were connected to each other. The electrical resistivity of silane-grafted MWCNT/polyimide decreased substantially below than that of acid-treated MWCNTs when the silane-modified MWCNT content was lower than 2.4 wt%. The percolation threshold of the MWCNT/polyimide composites is 1.0 wt% for silane-modified MWCNT and exceeds 7.0 wt% for acid-modified MWCNT. The acid-modified MWCNT/polyimide composites possess slightly higher glass transition temperatures than that of pure polyimide. The glass transition temperature of the polyimide increased significantly with silane-modified MWCNT content. Tensile properties of the polyimide have been improved with the MWCNTs content.

Meniscal allograft transplantation. Part 1: systematic review of graft biology, graft shrinkage, graft extrusion, graft sizing, and graft fixation.

Science.gov (United States)

Samitier, Gonzalo; Alentorn-Geli, Eduard; Taylor, Dean C; Rill, Brian; Lock, Terrence; Moutzouros, Vasilius; Kolowich, Patricia

2015-01-01

To provide a systematic review of the literature regarding five topics in meniscal allograft transplantation: graft biology, shrinkage, extrusion, sizing, and fixation. A systematic literature search was conducted using the PubMed (MEDLINE), ScienceDirect, and EBSCO-CINAHL databases. Articles were classified only in one topic, but information contained could be reported into other topics. Information was classified according to type of study (animal, in vitro human, and in vivo human) and level of evidence (for in vivo human studies). Sixty-two studies were finally included: 30 biology, 3 graft shrinkage, 11 graft extrusion, 17 graft size, and 6 graft fixation (some studies were categorized in more than one topic). These studies corresponded to 22 animal studies, 22 in vitro human studies, and 23 in vivo human studies (7 level II, 10 level III, and 6 level IV). The principal conclusions were as follows: (a) Donor cells decrease after MAT and grafts are repopulated with host cells form synovium; (b) graft preservation alters collagen network (deep freezing) and causes cell apoptosis with loss of viable cells (cryopreservation); (c) graft shrinkage occurs mainly in lyophilized and gamma-irradiated grafts (less with cryopreservation); (d) graft extrusion is common but has no clinical/functional implications; (e) overall, MRI is not superior to plain radiograph for graft sizing; (f) graft width size matching is more important than length size matching; (g) height appears to be the most important factor influencing meniscal size; (h) bone fixation better restores contact mechanics than suture fixation, but there are no differences for pullout strength or functional results; and (i) suture fixation has more risk of graft extrusion compared to bone fixation. Systematic review of level II-IV studies, Level IV.

Surface modification of halloysite nanotubes by vulcanization accelerator and properties of styrene-butadiene rubber nanocomposites with modified halloysite nanotubes

Energy Technology Data Exchange (ETDEWEB)

Zhong, Bangchao; Jia, Zhixin, E-mail: zxjia@scut.edu.cn; Hu, Dechao; Luo, Yuanfang; Guo, Baochun; Jia, Demin

2016-03-15

Graphical abstract: - Highlights: • Vulcanization accelerant was used to modify halloysite nanotubes (HNTs). • The modified HNTs reduced the activation energy of vulcanization. • Strong filler–rubber interaction was achieved in rubber/modified HNTs composites. • The modified HNTs exhibited excellent reinforcement effect on rubber. - Abstract: Vulcanization accelerant N-cyclohexyl-2-benzothiazole sulfenamide (CZ) was used as a surface modifier and chemically grafted on the surface of halloysite nanotubes (HNTs) to obtain CZ-functionalized HNTs (HNTs-s-CZ). It was found that HNTs-s-CZ could be homogeneously dispersed into styrene-butadiene rubber (SBR). The grafted CZ molecules, exactly located at the filler-rubber interface, reduced the activation energy of vulcanization of SBR/HNTs-s-CZ compounds. Besides, the density of chain segments introduced by the interfacial phase of SBR/HNTs-s-CZ nanocomposites was higher than the other nanocomposites with silane-modified HNTs (m-HNTs) or pristine HNTs, manifesting an indication of enhanced filler-rubber interfacial interaction in SBR/HNTs-s-CZ nanocomposites. Consequently, SBR/HNTs-s-CZ nanocomposites showed excellent mechanical properties. The tensile strength could be enhanced by as much as 38.6% and 102.5% compared to those of SBR/m-HNTs and SBR/HNTs nanocomposites, respectively, though containing equivalent accelerant component. The value of this work lies in the fact that apparent properties improvement of elastomer composites has been achieved by the incorporation of vulcanization accelerant-functionalized HNTs, which may be fruitful for the rational design of filler surface treatment and offer new scientific and technological opportunities for the preparation of high performance elastomer composites.

Surface modification of halloysite nanotubes by vulcanization accelerator and properties of styrene-butadiene rubber nanocomposites with modified halloysite nanotubes

International Nuclear Information System (INIS)

Zhong, Bangchao; Jia, Zhixin; Hu, Dechao; Luo, Yuanfang; Guo, Baochun; Jia, Demin

2016-01-01

Graphical abstract: - Highlights: • Vulcanization accelerant was used to modify halloysite nanotubes (HNTs). • The modified HNTs reduced the activation energy of vulcanization. • Strong filler–rubber interaction was achieved in rubber/modified HNTs composites. • The modified HNTs exhibited excellent reinforcement effect on rubber. - Abstract: Vulcanization accelerant N-cyclohexyl-2-benzothiazole sulfenamide (CZ) was used as a surface modifier and chemically grafted on the surface of halloysite nanotubes (HNTs) to obtain CZ-functionalized HNTs (HNTs-s-CZ). It was found that HNTs-s-CZ could be homogeneously dispersed into styrene-butadiene rubber (SBR). The grafted CZ molecules, exactly located at the filler-rubber interface, reduced the activation energy of vulcanization of SBR/HNTs-s-CZ compounds. Besides, the density of chain segments introduced by the interfacial phase of SBR/HNTs-s-CZ nanocomposites was higher than the other nanocomposites with silane-modified HNTs (m-HNTs) or pristine HNTs, manifesting an indication of enhanced filler-rubber interfacial interaction in SBR/HNTs-s-CZ nanocomposites. Consequently, SBR/HNTs-s-CZ nanocomposites showed excellent mechanical properties. The tensile strength could be enhanced by as much as 38.6% and 102.5% compared to those of SBR/m-HNTs and SBR/HNTs nanocomposites, respectively, though containing equivalent accelerant component. The value of this work lies in the fact that apparent properties improvement of elastomer composites has been achieved by the incorporation of vulcanization accelerant-functionalized HNTs, which may be fruitful for the rational design of filler surface treatment and offer new scientific and technological opportunities for the preparation of high performance elastomer composites.

Titan Montgolfiere Terrestrial Test Bed, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — With the Titan Saturn System Mission, NASA is proposing to send a Montgolfiere balloon to probe the atmosphere of Titan. To better plan this mission and create a...

Titan Montgolfiere Terrestrial Test Bed, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — With the Titan Saturn System Mission, NASA is proposing to send a Montgolfiere balloon to probe the atmosphere of Titan. In order to better plan this mission and...

AVIATR—Aerial Vehicle for In-situ and Airborne Titan Reconnaissance

DEFF Research Database (Denmark)

Barnes, Jason W.; Lemke, Lawrence; Foch, Rick

2012-01-01

We describe a mission concept for a stand-alone Titan airplane mission: Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR). With independent delivery and direct-to-Earth communications, AVIATR could contribute to Titan science either alone or as part of a sustained Titan...... Exploration Program. As a focused mission, AVIATR as we have envisioned it would concentrate on the science that an airplane can do best: exploration of Titan's global diversity. We focus on surface geology/hydrology and lower-atmospheric structure and dynamics. With a carefully chosen set of seven...... of a Space Vehicle (SV) for cruise, an Entry Vehicle (EV) for entry and descent, and the Air Vehicle (AV) to fly in Titan's atmosphere. Using an Earth-Jupiter gravity assist trajectory delivers the spacecraft to Titan in 7.5 years, after which the AVIATR AV would operate for a 1-Earth-year nominal mission...

Preparation of magnetic carbon nanotubes (Mag-CNTs) for biomedical and biotechnological applications.

Science.gov (United States)

Masotti, Andrea; Caporali, Andrea

2013-12-18

Carbon nanotubes (CNTs) have been widely studied for their potential applications in many fields from nanotechnology to biomedicine. The preparation of magnetic CNTs (Mag-CNTs) opens new avenues in nanobiotechnology and biomedical applications as a consequence of their multiple properties embedded within the same moiety. Several preparation techniques have been developed during the last few years to obtain magnetic CNTs: grafting or filling nanotubes with magnetic ferrofluids or attachment of magnetic nanoparticles to CNTs or their polymeric coating. These strategies allow the generation of novel versatile systems that can be employed in many biotechnological or biomedical fields. Here, we review and discuss the most recent papers dealing with the preparation of magnetic CNTs and their application in biomedical and biotechnological fields.

HST observations of the limb polarization of Titan

Science.gov (United States)

Bazzon, A.; Schmid, H. M.; Buenzli, E.

2014-12-01

Context. Titan is an excellent test case for detailed studies of the scattering polarization from thick hazy atmospheres. Accurate scattering and polarization parameters have been provided by the in situ measurements of the Cassini-Huygens landing probe. For Earth-bound observations Titan can only be observed at a backscattering situation, where the disk-integrated polarization is close to zero. However, with resolved imaging polarimetry a second order polarization signal along the entire limb of Titan can be measured. Aims: We present the first limb polarization measurements of Titan, which are compared as a test to our limb polarization models. Methods: Previously unpublished imaging polarimetry from the HST archive is presented, which resolves the disk of Titan. We determine flux-weighted averages of the limb polarization and radial limb polarization profiles, and investigate the degradation and cancelation effects in the polarization signal due to the limited spatial resolution of our observations. Taking this into account we derive corrected values for the limb polarization in Titan. The results are compared with limb polarization models, using atmosphere and haze scattering parameters from the literature. Results: In the wavelength bands between 250 nm and 2 μm a strong limb polarization of about 2 - 7% is detected with a position angle perpendicular to the limb. The fractional polarization is highest around 1 μm. As a first approximation, the polarization seems to be equally strong along the entire limb. The comparison of our data with model calculations and the literature shows that the detected polarization is compatible with expectations from previous polarimetric observations taken with Voyager 2, Pioneer 11, and the Huygens probe. Conclusions: Our results indicate that ground-based monitoring measurements of the limb-polarization of Titan could be useful for investigating local haze properties and the impact of short-term and seasonal variations of

The effect of synthesis conditions on the formation of titanate nanotubes

Energy Technology Data Exchange (ETDEWEB)

Qamar, M.; Yoon, C. R.; Oh, H. J.; Kim, S. J. [Sejong University, Seoul (Korea, Republic of); Kim, D. H.; Lee, K. S. [Hanyang University, Seoul (Korea, Republic of); Lee, H. G. [Korea Polytechnic University, Siheung (Korea, Republic of)

2006-10-15

The TiO{sub 2} sol was prepared hydrothermally in an autoclave from aqueous TiOCl{sub 2} solutions as a starting precursor. Hollow fibers were obtained when the sol-gel-derived TiO{sub 2} sol was treated chemically with a NaOH solution and subsequently heated in the autoclave under various conditions. A systematic analysis of the influence of different NaOH concentrations on the formation of nanotubes was carried out. The details of the nanotubular structure were investigated by using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Brauner-Emmett-Teller (BET) surface area, and photoluminescence (PL) measurements. From the TEM images, the outer and the inner diameters of the tubes were measured to be about 8 and 4 nm, respectively, the lengths were measured to be several hundreds of nanometers.

Experimental basis for a Titan probe organic analysis

International Nuclear Information System (INIS)

Mckay, C.P.; Scattergood, T.W.; Borucki, W.J.; Kasting, J.F.; Miller, S.L.; California Univ., San Diego, La Jolla)

1986-01-01

The recent Voyager flyby of Titan produced evidence for at least nine organic compounds in that atmosphere that are heavier than methane. Several models of Titan's atmosphere, as well as laboratory simulations, suggest the presence of organics considerably more complex that those observed. To ensure that the in situ measurements are definitive with respect to Titan's atmosphere, experiment concepts, and the related instrumentation, must be carefully developed specifically for such a mission. To this end, the possible composition of the environment to be analyzed must be bracketed and model samples must be provided for instrumentation development studies. Laboratory studies to define the optimum flight experiment and sampling strategy for a Titan entry probe are currently being conducted. Titan mixtures are being subjected to a variety of energy sources including high voltage electron from a DC discharge, high current electric shock, and laser detonation. Gaseous and solid products are produced which are then analyzed. Samples from these experiements are also provided to candidate flight experiments as models for instrument development studies. Preliminary results show that existing theoretical models for chemistry in Titan's atmosphere cannot adequetely explain the presence and abundance of all trace gases observed in these experiments

Supercapacitance of Single-Walled Carbon Nanotubes-Polypyrrole Composites

Directory of Open Access Journals (Sweden)

Matei Raicopol

2013-01-01

Full Text Available The composites based on carbon nanotubes (CNTs and conducting polymers (CPs are promising materials for supercapacitor devices due to their unique nanostructure that combines the large pseudocapacitance of the CPs with the fast charging/discharging double-layer capacitance and excellent mechanical properties of the CNTs. Here, we report a new electrochemical method to obtain polypyrrole (PPY/single-walled carbon nanotube (SWCNT composites. In the first step, the SWCNTs are covalently functionalized with monomeric units of pyrrole by esterification of acyl chloride functionalized SWCNTs and N-(6-hydroxyhexylpyrrole. In the second step, the PPY/SWCNTs composites are obtained by copolymerizing the pyrrole monomer with the pyrrole units grafted on SWCNTs surface using controlled potential electrolysis. The composites were further characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The results showed good electrochemical charge storage properties for the synthesized composites based on PPY and SWCNTs covalently functionalized with pyrrole units making them promising electrode materials for high power supercapacitors.

History and challenges of barium titanate: Part I

Directory of Open Access Journals (Sweden)

Vijatović M.M.

2008-01-01

Full Text Available Barium titanate is the first ferroelectric ceramics and a good candidate for a variety of applications due to its excellent dielectric, ferroelectric and piezoelectric properties. Barium titanate is a member of a large family of compounds with the general formula ABO3 called perovskites. Barium titanate can be prepared using different methods. The synthesis method depends on the desired characteristics for the end application. The used method has a significant influence on the structure and properties of barium titanate materials. In this review paper, Part I contains a study of the BaTiO3 structure and frequently used synthesis methods.

Titan's organic chemistry: Results of simulation experiments

Science.gov (United States)

Sagan, Carl; Thompson, W. Reid; Khare, Bishun N.

1992-01-01

Recent low pressure continuous low plasma discharge simulations of the auroral electron driven organic chemistry in Titan's mesosphere are reviewed. These simulations yielded results in good accord with Voyager observations of gas phase organic species. Optical constants of the brownish solid tholins produced in similar experiments are in good accord with Voyager observations of the Titan haze. Titan tholins are rich in prebiotic organic constituents; the Huygens entry probe may shed light on some of the processes that led to the origin of life on Earth.

The commercial evolution of the Titan program

Science.gov (United States)

Isakowitz, Steven

1988-07-01

The present status evaluation of proprietary efforts to turn the once exclusively government-requirements-oriented Titan launch vehicle into a successful commercial competitor is divided into three phases. The first phase notes recent changes in U.S. space transportation policy and the Titan configurations evaluated for commercial feasibility. The second phase is a development history for the current vehicle's marketing organization and the right-to-use agreement for a launch site. Phase three projects the prospective marketing climate for a commercial Titan vehicle and its planned improvements.

Conductance of functionalized nanotubes, graphene and nanowires: from ab initio to mesoscopic physics

Energy Technology Data Exchange (ETDEWEB)

Blase, X. [Institut Neel, CNRS/UJF, 25 rue des Martyrs, 38042 Grenoble (France); LPMCN, CNRS/Universite Lyon I, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne (France); Adessi, C. [LPMCN, CNRS/Universite Lyon I, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne (France); Biel, B. [Dpto. Electronica y Tecnologia de Computadores, Universidad de Granada Facultad de Ciencias, Campus de Fuente Nueva, 18071 Granada (Spain); Lopez-Bezanilla, A.; Roche, S. [CEA, Institut of Nanosciences and Cryogenics, INAC/SPSMS/GT, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Fernandez-Serra, M.V. [LPMCN, CNRS/Universite Lyon I, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne (France); Physics and Astronomy department, Stony Brooks University, NY 11794 (United States); Margine, E.R. [LPMCN, CNRS/Universite Lyon I, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne (France); Department of Materials, Oxford University, Oxford OX1 3PH (United Kingdom); Triozon, F. [CEA, LETI-Minatec, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)

2010-12-15

We review recent theoretical results aiming at understanding the impact of doping and functionalization on the electronic transport properties of nanotubes, nanowires and graphene ribbons. On the basis of ab initio calculations, the conductance of micrometer long tubes or ribbons randomly doped or grafted can be studied, allowing to extract quantities at mesoscopic length scales such as the elastic mean free path and localization length. While the random modification of a 1D conducting channel leads generally to a significant loss of conductance, strategies can be found to either exploit or limitate such a detrimental effect. Spin-filtering in transition metal doped nanotubes, the opening of a mobility gap in graphene ribbons, and the choice of molecules to limitate backscattering in covalently functionalized tubes are examples that will be discussed. Symbolic representation of a nanotube filled with Cobalt atoms or clusters with subsequent optimal spinvalve effect (see text). (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Selections from 2017: Discoveries in Titan's Atmosphere

Science.gov (United States)

Kohler, Susanna

2017-12-01

Editors note:In these last two weeks of 2017, well be looking at a few selections that we havent yet discussed on AAS Nova from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume in January.Carbon Chain Anions and the Growth of Complex Organic Molecules in Titans IonospherePublished July2017Main takeaway:Graphic depicting some of the chemical reactions taking place in Titans atmosphere, leading to the generation of organic haze particles. [ESA]In a recently published study led by Ravi Desai (University College London), scientists used data from the Cassini mission to identify negatively charged molecules known as carbon chain anions in the atmosphere of Saturns largest moon, Titan.Why its interesting:Carbon chain anions are the building blocks ofmore complex molecules, and Titans thick nitrogen and methane atmosphere mightmimic the atmosphere of earlyEarth. This first unambiguous detection of carbon chain anions in a planet-like atmosphere might therefore teach us about the conditions and chemical reactions that eventually led to the development of life on Earth. And ifwe can use Titan to learn about how complex molecules grow from these anion chains, we may be able to identify auniversal pathway towards the ingredients for life.What weve learned so far:Cassini measured fewer and fewer lower-mass anions the deeper in Titans ionosphere that it looked and at the same time,an increase in the number of precursors to larger aerosol molecules further down. This tradeoff strongly suggests that the anions are indeed involved in building up the more complex molecules, seeding their eventual growth into the complex organic haze of Titans lower atmosphere.CitationR. T. Desai et al 2017 ApJL 844 L18. doi:10.3847/2041-8213/aa7851

Niobium-doped strontium titanates as SOFC anodes

DEFF Research Database (Denmark)

Blennow Tullmar, Peter; Kammer Hansen, Kent; Wallenberg, L. Reine

2008-01-01

been synthesized with a recently developed modified glycine-nitrate process. The synthesized powders have been calcined and sintered in air or in 9% H(2) / N(2) between 800 - 1400 degrees C. After calcination the samples were single phase Nb-doped strontium titanate with grain sizes of less than 100 nm...... in diameter on average. The phase purity, defect structure, and microstructure of the materials have been analyzed with SEM, XRD, and TGA. The electrical conductivity of the Nb-doped titanate decreased with increasing temperature and showed a phonon scattering conduction mechanism with sigma > 120 S...... ability of the Nb-doped titanates to be used as a part of a SOFC anode. However, the catalytic activity of the materials was not sufficient and it needs to be improved if titanate based materials are to be realized as constituents in SOFC anodes....

Volatile products controlling Titan's tholins production

KAUST Repository

Carrasco, Nathalie

2012-05-01

A quantitative agreement between nitrile relative abundances and Titan\\'s atmospheric composition was recently shown with a reactor simulating the global chemistry occurring in Titan\\'s atmosphere (Gautier et al. [2011]. Icarus, 213, 625-635). Here we present a complementary study on the same reactor using an in situ diagnostic of the gas phase composition. Various initial N 2/CH 4 gas mixtures (methane varying from 1% to 10%) are studied, with a monitoring of the methane consumption and of the stable gas neutrals by in situ mass spectrometry. Atomic hydrogen is also measured by optical emission spectroscopy. A positive correlation is found between atomic hydrogen abundance and the inhibition function for aerosol production. This confirms the suspected role of hydrogen as an inhibitor of heterogeneous organic growth processes, as found in Sciamma-O\\'Brien et al. (Sciamma-O\\'Brien et al. [2010]. Icarus, 209, 704-714). The study of the gas phase organic products is focussed on its evolution with the initial methane amount [CH 4] 0 and its comparison with the aerosol production efficiency. We identify a change in the stationary gas phase composition for intermediate methane amounts: below [CH 4] 0=5%, the gas phase composition is mainly dominated by nitrogen-containing species, whereas hydrocarbons are massively produced for [CH 4] 0>5%. This predominance of N-containing species at lower initial methane amount, compared with the maximum gas-to solid conversion observed in Sciamma-O\\'Brien et al. (2010) for identical methane amounts confirms the central role played by N-containing gas-phase compounds to produce tholins. Moreover, two protonated imines (methanimine CH 2NH and ethanamine CH 3CHNH) are detected in the ion composition in agreement with Titan\\'s INMS measurements, and reinforcing the suspected role of these chemical species on aerosol production. © 2012 Elsevier Inc.

Selective adsorption and ion exchange of metal cations and anions with silico-titanates and layered titanates

International Nuclear Information System (INIS)

Anthony, R.G.; Philip, C.V.

1993-01-01

Metal ions may be removed from aqueous wastes from metal processing plants and from refineries. They may also be used in concentrating radioactive elements found in dilute, aqueous, nuclear wastes. A new series of silico-titanates and alkali titanates are shown to have specific selectivity for cations of lead, mercury, and cadmium and the dichromate anion in solutions with low and high pH. Furthermore, one particular silico-titanate, TAM-5, was found to be highly selective for Cs + and Sr 2+ in solutions of 5.7 M Na + and 0.6 M Oh - . A high potential exists for these materials for removing Cs + and Sr 2+ from radioactive aqueous wastes containing high concentrations of Na + at high and low pH

Radiation effects in uranium-niobium titanates

International Nuclear Information System (INIS)

Lian, J.; Wang, S.X.; Wang, L.M.; Ewing, R.C.

2000-01-01

Pyrochlore is an important actinide host phase proposed for the immobilization of high level nuclear wastes and excess weapon plutonium.[1] Synthetic pyrochlore has a great variety of chemical compositions due to the possibility of extensive substitutions in the pyrochlore structure.[2] During the synthesis of pyrochlore, additional complex titanate phases may form in small quantities. The response of these phases to radiation damage must be evaluated because volume expansion of minor phases may cause micro-fracturing. In this work, two complex uranium-niobium titanates, U 3 NbO 9.8 (U-rich titanate) and Nb 3 UO 10 (Nb-rich titanate) were synthesized by the alkoxide/nitrate route at 1300 deg. C under an argon atmosphere. The phase composition and structure were analyzed by EDS, BSE, XRD, EMPA and TEM techniques. An 800 KeVKr 2+ irradiation was performed using the IVEM-Tandem Facility at Argonne National Laboratory in a temperature range from 30 K to 973 K. The radiation effects were observed by in situ TEM

The TITAN Reversed-Field Pinch fusion reactor study

International Nuclear Information System (INIS)

1988-03-01

The TITAN Reversed-Field Pinch (RFP) fusion reactor study is a multi-institutional research effort to determine the technical feasibility and key developmental issues of an RFP fusion reactor, especially at high power density, and to determine the potential economics, operations, safety, and environmental features of high-mass-power-density fusion systems. The TITAN conceptual designs are DT burning, 1000 MWe power reactors based on the RFP confinement concept. The designs are compact, have a high neutron wall loading of 18 MW/m 2 and a mass power density of 700 kWe/tonne. The inherent characteristics of the RFP confinement concept make fusion reactors with such a high mass power density possible. Two different detailed designs have emerged: the TITAN-I lithium-vanadium design, incorporating the integrated-blanket-coil concept; and the TITAN-II aqueous loop-in-pool design with ferritic steel structure. This report contains a collection of 16 papers on the results of the TITAN study which were presented at the International Symposium on Fusion Nuclear Technology. This collection describes the TITAN research effort, and specifically the TITAN-I and TITAN-II designs, summarizing the major results, the key technical issues, and the central conclusions and recommendations. Overall, the basic conclusions are that high-mass power-density fusion reactors appear to be technically feasible even with neutron wall loadings up to 20 MW/m 2 ; that single-piece maintenance of the FPC is possible and advantageous; that the economics of the reactor is enhanced by its compactness; and the safety and environmental features need not to be sacrificed in high-power-density designs. The fact that two design approaches have emerged, and others may also be possible, in some sense indicates the robustness of the general findings

A composite of polyelectrolyte-grafted multi-walled carbon nanotubes and in situ polymerized polyaniline for the detection of low concentration triethylamine vapor

International Nuclear Information System (INIS)

Li Yang; Wang Huicai; Cao Xiehong; Yuan Minyong; Yang Mujie

2008-01-01

Multi-walled carbon nanotubes (MWNTs) grafted with sodium polystyrenesulfonate (NaPSS) were deposited on an interdigitated gold electrode decorated with a layer of positively charged poly(diallyldimethylammonium chloride) by a self-assembly method. Then polyaniline (PANI) was in situ polymerized on the surface of the MWNTs to prepare a composite. The structure and morphology of the composite were investigated by Raman spectroscopy and scanning electron microscopy. The electrical responses of the composite to triethylamine vapor of low concentrations were measured at room temperature. It was found that the composite exhibited a linear response to the vapor in the range of 0.5-8 ppm with the highest sensitivity of ∼80%, which is much higher than that of MWNTs and PANI separately, and an obvious synergetic effect was observed. In addition, the detection limit was as low as the ppb level, and reversible and relatively fast responses (t 90% ∼200 s and ∼10 min for sensing and recovery, respectively) were observed. The sensing characteristics are highly related to the gas responses of PANI, and a sensing mechanism considering the interaction of MWNTs and PANI was proposed

Fabrication of titanate nanotubes/iron oxide magnetic composite for the high efficient capture of radionuclides: a case investigation of 109Cd(II)

International Nuclear Information System (INIS)

Lei Dai; Jun Zheng; Lijie Wang

2013-01-01

In this paper, the capture of radiocadmium (Cd(II)) by adsorption onto the titanate nanotube/iron oxide (TNT/IOM) magnetic composite as a function of contact time, pH, ionic strength, foreign cation and anion ions, humic acid (HA) and fulvic acid (FA) was studied using batch technique. The results indicated that the adsorption of Cd(II) onto the TNT/IOM magnetic composite was dependent on ionic strength at pH 9.0. Outer-sphere surface complexation were the main mechanism of Cd(II) adsorption onto the TNT/IOM magnetic composite at low pH values, whereas the adsorption was mainly dominated via inner-sphere surface complexation at high pH values. The adsorption of Cd(II) onto the TNT/IOM magnetic composite was dependent on foreign cation and anion ions at low pH values, but was independent of foreign cation and anion ions at high pH values. A positive effect of HA/FA on Cd(II) adsorption onto the TNT/IOM magnetic composite was found at low pH values, while a negative effect was observed at high pH values. From the results of Cd(II) removal by the TNT/IOM magnetic composite, the optimum reaction conditions can be obtained for the maximum removal of Cd(II) from water. It is clear that the best pH values of the system to remove Cd(II) from solution by using the TNT/IOM magnetic composite are 7.0-8.0. Considering the low cost and effective disposal of Cd(II)-contaminated wastewaters, the best condition for Cd(II) capture by the TNT/IOM magnetic composite is at room temperature and solid content of 0.5 g L -1 . These results are quite important for estimating and optimizing the removal of Cd(II) and related metal ions by the TNT-based magnetic composite. (author)

Enhanced visible-light-responsive photodegradation of bisphenol A by Cu, N-codoped titanate nanotubes prepared by microwave-assisted hydrothermal method

International Nuclear Information System (INIS)

Doong, Ruey-an; Liao, Chun-Yi

2017-01-01

Highlights: • The Cu, N-codoped TNTs were prepared by microwave assisted hydrothermal method. • The Cu(0) in codoped TNTs can serve as electron donors as well as electron meditors. • The surface normalized rate constants for BPA removal by Cu, N-TNT were 1.5–4.3 times higher than that of P25 TiO_2. • The Cu, N-codoped TNTs prolonged the generation of radicals for at least 5 min. - Abstract: In this study, a rapid and effective microwave-assisted hydrothermal method was developed for the synthesis of Cu, N-codoped titanate nanotubes (Cu, N-TNTs) to enhance the photocatalytic degradation efficiency and rate of bisphenol A (BPA) under UV and visible light irradiations. The TNTs were first synthesized at 150 °C for 3 h under microwave heating conditions followed by the calcination at 450 °C in the presence of 6 wt% Cu ions and N_2/NH_3 to fabricate Cu, N-TNTs composites. The Cu, N-TNTs exhibited excellent photocatalytic activity toward BPA degradation under UV and visible light irradiations. The X-ray photoelectron spectra indicated that Cu species in Cu, N-TNTs were mainly in zerovalent form and could serve as the electron donors as well as shuttling species to accelerate the photodegradation of BPA. In addition, the nitrogen atoms were incorporated into the anatase lattices to increase the visible-light-responsive capability. The surface normalized reaction rate constants for BPA degradation were 4.3 and 1.5 times higher than those of Degussa P25 TiO_2 under UV and visible light irradiations, respectively. The electron spin resonance spectra showed that Cu, N-codoped TNTs prolonged the generation of oxygen-containing radicals for at least 5 min, resulting in the significant enhancement of photodegradation efficiency and rate of BPA. Results obtained in this study open a new avenue by using simple and effective microwave-assisted hydrothermal method to fabricate low dimensional codoped TNTs which can be potentially applied in a wide variety of fields of

Advances in Architectural Elements For Future Missions to Titan

Science.gov (United States)

Reh, Kim; Coustenis, Athena; Lunine, Jonathan; Matson, Dennis; Lebreton, Jean-Pierre; Vargas, Andre; Beauchamp, Pat; Spilker, Tom; Strange, Nathan; Elliott, John

2010-05-01

The future exploration of Titan is of high priority for the solar system exploration community as recommended by the 2003 National Research Council (NRC) Decadal Survey [1] and ESA's Cosmic Vision Program themes. Recent Cassini-Huygens discoveries continue to emphasize that Titan is a complex world with very many Earth-like features. Titan has a dense, nitrogen atmosphere, an active climate and meteorological cycles where conditions are such that the working fluid, methane, plays the role that water does on Earth. Titan's surface, with lakes and seas, broad river valleys, sand dunes and mountains was formed by processes like those that have shaped the Earth. Supporting this panoply of Earth-like processes is an ice crust that floats atop what might be a liquid water ocean. Furthermore, Titan is rich in very many different organic compounds—more so than any place in the solar system, except Earth. The Titan Saturn System Mission (TSSM) concept that followed the 2007 TandEM ESA CV proposal [2] and the 2007 Titan Explorer NASA Flagship study [3], was examined [4,5] and prioritized by NASA and ESA in February 2009 as a mission to follow the Europa Jupiter System Mission. The TSSM study, like others before it, again concluded that an orbiter, a montgolfiere hot-air balloon and a surface package (e.g. lake lander, Geosaucer (instrumented heat shield), …) are very high priority elements for any future mission to Titan. Such missions could be conceived as Flagship/Cosmic Vision L-Class or as individual smaller missions that could possibly fit into NASA New Frontiers or ESA Cosmic Vision M-Class budgets. As a result of a multitude of Titan mission studies, a clear blueprint has been laid out for the work needed to reduce the risks inherent in such missions and the areas where advances would be beneficial for elements critical to future Titan missions have been identified. The purpose of this paper is to provide a brief overview of the flagship mission architecture and

Cosmic-rays induced Titan tholins and their astrobiological significances

Science.gov (United States)

Kobayashi, Kensei; Taniuchi, Toshinori; Hosogai, Tomohiro; Kaneko, Takeo; Takano, Yoshinori; Khare, Bishun; McKay, Chris

Titan is the largest satellite of Saturn. It is quite unique satellite since it has a dense atmosphere composed of nitrogen and methane, and has been sometimes considered as a model of primitive Earth. In Titan atmosphere, a wide variety of organic compounds and mists made of complex organics. Such solid complex organics are often referred to as tholins. A number of laboratory experiments simulating reactions in Titan atmosphere have been conducted. In most of them, ultraviolet light and discharges (simulating actions of electrons in Saturn magnetosphere) were used, which were simulation of the reactions in upper dilute atmosphere of Titan. We examined possible formation of organic compounds in the lower dense atmosphere of Titan, where cosmic rays are major energies. A Mixture of 35 Torr of methane and 665 Torr of nitrogen was irradiated with high-energy protons (3 MeV) from a van de Graaff accelerator (TIT, Japan) or from a Tandem accelerator (TIARA, QUBS, JAEA, Japan). In some experiments, 13 C-labelled methane was used. We also performed plasma discharges in a mixture of methane (10 %) and nitrogen (90 %) to simulate the reactions in the upper atmosphere of Titan. Solid products by proton irradiation and those by plasma discharges are hereafter referred to as PI-tholins and PD-tholins, respectively. The resulting PI-tholins were observed with SEM and AFM. They were characterized by pyrolysis-GC/MS, gel permeation chromatography, FT-IR, etc. Amino acids in PI-and PD-tholins were analyzed by HPLC, GC/MS and MALDI-TOF-MS after acid hydrolysis. 18 O-Labelled water was used in some cases during hydrolysis. Filamentary and/or globular-like structures were observed by SEM and AFM. By pyrolysis-GC/MS of PI-tholins, ammonia and hydrogen cyanide were detected, which was the same as the results obtained in Titan atmosphere during the Huygens mission. A wide variety of amino acids were detected after hydrolysis of both tholins. It was proved that oxygen atoms in the amino

Air Pump-Assisted Graft Centration, Graft Edge Unfolding, and Graft Uncreasing in Young Donor Graft Pre-Descemet Endothelial Keratoplasty.

Science.gov (United States)

Jacob, Soosan; Narasimhan, Smita; Agarwal, Amar; Agarwal, Athiya; A I, Saijimol

2017-08-01

To assess an air pump-assisted technique for graft centration, graft edge unfolding, and graft uncreasing while performing pre-Descemet endothelial keratoplasty (PDEK) using young donor grafts. Continuous pressurized air infusion was used for graft centration, graft edge unfolding, and graft unwrinkling. Ten eyes of 10 patients underwent PDEK with donors aged below 40 years. In all eyes, the donor scrolled into tight scrolls. In all cases, the air pump-assisted technique was effective in positioning and centering the graft accurately and in straightening infolded graft edges and smoothing out graft creases and wrinkles. Endothelial cell loss was 38.6%. Postoperative best-corrected visual acuity at 6 months was 0.66 ± 0.25 in decimal equivalent. Continuous pressurized air infusion acted as a third hand providing a continuous pressure head that supported the graft and prevented graft dislocation as well as anterior chamber collapse during intraocular maneuvering. Adequate maneuvering space was available in all cases, and bleeding, if any, was tamponaded successfully in all cases. Although very young donor grafts may be used for PDEK, they are difficult to center and unroll completely before floating against host stroma. An air pump-assisted technique using continuous pressurized air infusion allows successful final graft positioning even with very young donor corneas. It thus makes surgery easier as several key steps are made easier to handle. It additionally helps in tamponading hemorrhage during peripheral iridectomy, increasing surgical space, preventing fluctuations in the anterior chamber depth, and promoting graft adherence.

Robust forests of vertically aligned carbon nanotubes chemically assembled on carbon substrates.

Science.gov (United States)

Garrett, David J; Flavel, Benjamin S; Shapter, Joseph G; Baronian, Keith H R; Downard, Alison J

2010-02-02

Forests of vertically aligned carbon nanotubes (VACNTs) have been chemically assembled on carbon surfaces. The structures show excellent stability over a wide potential range and are resistant to degradation from sonication in acid, base, and organic solvent. Acid-treated single-walled carbon nanotubes (SWCNTs) were assembled on amine-terminated tether layers covalently attached to pyrolyzed photoresist films. Tether layers were electrografted to the carbon substrate by reduction of the p-aminobenzenediazonium cation and oxidation of ethylenediamine. The amine-modified surfaces were incubated with cut SWCNTs in the presence of N,N'-dicyclohexylcarbodiimide (DCC), giving forests of vertically aligned carbon nanotubes (VACNTs). The SWCNT assemblies were characterized by scanning electron microscopy, atomic force microscopy, and electrochemistry. Under conditions where the tether layers slow electron transfer between solution-based redox probes and the underlying electrode, the assembly of VACNTs on the tether layer dramatically increases the electron-transfer rate at the surface. The grafting procedure, and hence the preparation of VACNTs, is applicable to a wide range of materials including metals and semiconductors.

PVC/carbon nanotubes nanocomposites: evaluation of electrical resistivity and the residual solvent effect over the thermal properties of nanocomposites

International Nuclear Information System (INIS)

Araujo, Rogerio Gomes; Pires, Alfredo T.N.

2013-01-01

The procedure for obtaining nanocomposite by dispersing the nanoparticles in matrix polymer in solution with subsequent elimination of the solvent has been widely used, considering better efficiency in obtaining homogeneity of the final product. However, the presence of residual solvent may affect the nanocomposites in micro-and macroscopic properties of the product. The aim of this study was to evaluate the thermal properties of nanocomposites of poly(vinylchloride)/multi-walled carbon nanotube obtained from the polymer solution and dispersion of carbon nanotubes in tetrahydrofuran (THF), as well as the electrical resistivity of nanocomposites and the influence of residual solvent. The presence of residual tetrahydrofuran reduces the glass transition temperature (Tg) up to 26 °C, being independent of the amount of carbon nanotubes. The total elimination of the solvent is an important factor that does not induce changes in the properties of the polymeric matrix. The graft-COOH groups in the structure of the nanotubes leads to a considerable reduction of the electrical resistivity in ten orders of magnitude, from 0.4 %wt of nanotubes in the nanocomposite composition. (author)

Infrared characterization of strontium titanate thin films

International Nuclear Information System (INIS)

Almeida, B.G.; Pietka, A.; Mendes, J.A.

2004-01-01

Strontium titanate thin films have been prepared at different oxygen pressures with various post-deposition annealing treatments. The films were deposited by pulsed laser ablation at room temperature on Si(0 0 1) substrates with a silica buffer layer. Infrared reflectance measurements were performed in order to determine relevant film parameters such as layer thicknesses and chemical composition. The infrared reflectance spectra were fitted by using adequate dielectric function forms for each layer. The fitting procedure provided the extraction of the dielectric functions of the strontium titanate film, the silica layer and the substrate. The as-deposited films are found to be amorphous, and their infrared spectra present peaks corresponding to modes with high damping constants. As the annealing time and temperature increases the strontium titanate layer becomes more ordered so that it can be described by its SrTiO 3 bulk mode parameters. Also, the silica layer grows along with the ordering of the strontium titanate film, due to oxidation during annealing

Titan after Cassini Huygens

Science.gov (United States)

Beauchamp, P. M.; Lunine, J.; Lebreton, J.; Coustenis, A.; Matson, D.; Reh, K.; Erd, C.

2008-12-01

In 2005, the Huygens Probe gave us a snapshot of a world tantalizingly like our own, yet frozen in its evolution on the threshold of life. The descent under parachute, like that of Huygens in 2005, is happening again, but this time in the Saturn-cast twilight of winter in Titan's northern reaches. With a pop, the parachute is released, and then a muffled splash signals the beginning of the first floating exploration of an extraterrestrial sea-this one not of water but of liquid hydrocarbons. Meanwhile, thousands of miles away, a hot air balloon, a "montgolfiere," cruises 6 miles above sunnier terrain, imaging vistas of dunes, river channels, mountains and valleys carved in water ice, and probing the subsurface for vast quantities of "missing" methane and ethane that might be hidden within a porous icy crust. Balloon and floater return their data to a Titan Orbiter equipped to strip away Titan's mysteries with imaging, radar profiling, and atmospheric sampling, much more powerful and more complete than Cassini was capable of. This spacecraft, preparing to enter a circular orbit around Saturn's cloud-shrouded giant moon, has just completed a series of flybys of Enceladus, a tiny but active world with plumes that blow water and organics from the interior into space. Specialized instruments on the orbiter were able to analyze these plumes directly during the flybys. Titan and Enceladus could hardly seem more different, and yet they are linked by their origin in the Saturn system, by a magnetosphere that sweeps up mass and delivers energy, and by the possibility that one or both worlds harbor life. It is the goal of the NASA/ESA Titan Saturn System Mission (TSSM) to explore and investigate these exotic and inviting worlds, to understand their natures and assess the possibilities of habitability in this system so distant from our home world. Orbiting, landing, and ballooning at Titan represent a new and exciting approach to planetary exploration. The TSSM mission

Low-Latitude Ethane Rain on Titan

Science.gov (United States)

Dalba, Paul A.; Buratti, Bonnie J.; Brown, R. H.; Barnes, J. W.; Baines, K. H.; Sotin, C.; Clark, R. N.; Lawrence, K. J.; Nicholson, P. D.

2012-01-01

Cassini ISS observed multiple widespread changes in surface brightness in Titan's equatorial regions over the past three years. These brightness variations are attributed to rainfall from cloud systems that appear to form seasonally. Determining the composition of this rainfall is an important step in understanding the "methanological" cycle on Titan. I use data from Cassini VIMS to complete a spectroscopic investigation of multiple rain-wetted areas. I compute "before-and-after" spectral ratios of any areas that show either deposition or evaporation of rain. By comparing these spectral ratios to a model of liquid ethane, I find that the rain is most likely composed of liquid ethane. The spectrum of liquid ethane contains multiple absorption features that fall within the 2-micron and 5-micron spectral windows in Titan's atmosphere. I show that these features are visible in the spectra taken of Titan's surface and that they are characteristically different than those in the spectrum of liquid methane. Furthermore, just as ISS saw the surface brightness reverting to its original state after a period of time, I show that VIMS observations of later flybys show the surface composition in different stages of returning to its initial form.

Reduced-graphene-oxide-and-strontium-titanate-based double ...

Indian Academy of Sciences (India)

GO)/strontium titanate were pre- ... R-GO and strontium titanate were synthesized and characterized before ... Microwave absorption capabilities of the composite absorbers were investigated using a .... was backed with a conducting metal sheet.

Stent graft placement for dysfunctional arteriovenous grafts

Energy Technology Data Exchange (ETDEWEB)

Jeon, Gyeong Sik [Dept. of Radiology, CHA Bundang Medical Center, College of Medicine, CHA University, Seongnam (Korea, Republic of); Shin, Byung Seok; Ohm, Joon Young; Ahn, Moon Sang [Chungnam National University Hospital, Daejeon (Korea, Republic of)

2015-07-15

This study aimed to evaluate the usefulness and outcomes of stent graft use in dysfunctional arteriovenous grafts. Eleven patients who underwent stent graft placement for a dysfunctional hemodialysis graft were included in this retrospective study. Expanded polytetrafluoroethylene covered stent grafts were placed at the venous anastomosis site in case of pseudoaneurysm, venous laceration, elastic recoil or residual restenosis despite the repeated angioplasty. The patency of the arteriovenous graft was evaluated using Kaplan-Meier analysis. Primary and secondary mean patency was 363 days and 741 days. Primary patency at 3, 6, and 12 months was 82%, 73%, and 32%, respectively. Secondary patency at the 3, 6, 12, 24, and 36 months was improved to 91%, 82%, 82%, 50%, and 25%, respectively. Fractures of the stent graft were observed in 2 patients, but had no effect on the patency. Stent graft placement in dysfunctional arteriovenous graft is useful and effective in prolonging graft patency.

Cryovolcanism on Titan

Science.gov (United States)

Mitri, G.; Showman, A. P.; Lunine, J. I.; Lopes, R. M.

2008-12-01

Remote sensing observations yield evidence for cryovolcanism on Titan, and evolutionary models support (but do not require) the presence of an ammonia-water subsurface ocean. The impetus for invoking ammonia as a constituent in an internal ocean and cryovolcanic magma comes from two factors. First, ammonia-water liquid has a lower freezing temperature than pure liquid water, enabling cryovolcanism under the low- temperature conditions prevalent in the outer Solar System. Second, pure water is negatively buoyant with respect to pure water ice, which discourages eruption from the subsurface ocean to the surface. In contrast, the addition of ammonia to the water decreases its density, hence lessening this problem of negative buoyancy. A marginally positive buoyant ammonia-water mixture might allow effusive eruptions from a subsurface ocean. If the subsurface ocean were positively buoyant, all the ammonia would have been erupted very early in Titan's history. Contrary to this scenario, Cassini-Huygens has so far observed neither a global abundance nor a complete dearth of cryovolcanic features. Further, an ancient cryovolcanic epoch cannot explain the relative youth of Titan's surface. Crucial to invoking ammonia-water resurfacing as the source of the apparently recent geological activity is not how to make ammonia-water volcanism work (because the near neutral buoyancy of the ammonia-water mixture encourages an explanation), but rather how to prevent eruption from occurring so easily that cryovolcanic activity is over early on. Although cryovolcanism by ammonia-water has been proposed as a resurfacing process on Titan, few models have specifically dealt with the problem of how to transport ammonia-water liquid onto the surface. We proposed a model of cryovolcanism that involve cracking at the base of the ice shell and formation of ammonia-water pockets in the ice. While the ammonia-water pockets cannot easily become neutral buoyant and promote effusive eruptions

The greenhouse and antigreenhouse effects on Titan

Science.gov (United States)

Mckay, Christopher P.; Pollack, James B.; Courtin, Regis

1991-01-01

The parallels between the atmospheric thermal structure of the Saturnian satellite Titan and the hypothesized terrestrial greenhouse effect can serve as bases for the evaluation of competing greenhouse theories. Attention is presently drawn to the similarity between the roles of H2 and CH4 on Titan and CO2 and H2O on earth. Titan also has an antigreenhouse effect due to a high-altitude haze layer which absorbs at solar wavelengths, while remaining transparent in the thermal IR; if this haze layer were removed, the antigreenhouse effect would be greatly reduced, exacerbating the greenhouse effect and raising surface temperature by over 20 K.

Raising the Titanic.

Science.gov (United States)

Baker, Romona

1990-01-01

Described is an activity in which groups of students investigate engineering principles by writing a feasibility study to raise the luxury liner, Titanic. The problem statement and directions, and suggestions for problem solutions are included. (CW)

Controlled synthesis and photocatalytic investigation of different-shaped one-dimensional titanic acid nanomaterials

Energy Technology Data Exchange (ETDEWEB)

Li, Qiuye [State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); The Graduate School of the Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 10080 (China); Key Laboratory of Special Functional Materials, Henan University, KaiFeng 475001 (China); Lu, Gongxuan [State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

2008-10-15

Different-shaped one-dimensional (1D) titanic acid nanomaterials (TANs) were prepared by hydrothermal synthesis. By changing the reaction temperature (120, 170 and 200 C), three kinds of 1D TAN, short-nanotubes (SNT), long-nanotubes (LNT), and nanorods (NR), were obtained. The obtained TANs were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), and solid-stated diffuse reflectance UV-vis spectra (UV-vis DRS) techniques. Based on these 1D TAN, Eosin Y-sensitized Pt-loaded TAN were prepared by the in situ impregnation and photo-reduction method. Their photocatalytic activity for hydrogen generation was evaluated in triethanolamine (TEOA) aqueous solution under visible light irradiation ({lambda} {>=} 420 nm). The results indicated that the morphology difference led to a significant variation of photocatalytic performance for hydrogen generation, with the activity order as follows: Eosin Y-sensitized Pt-loaded LNT > Eosin Y-sensitized Pt-loaded NR > Eosin Y-sensitized Pt-loaded SNT. The experimental conditions for photocatalytic hydrogen generation such as Pt loading content, the mass ratio of Eosin Y to TAN, and so on, were optimized. As a result, the highest apparent quantum yields of hydrogen generation for Eosin Y-sensitized Pt-loaded SNT, LNT, and NR were 6.65, 17.36, and 15.04%, respectively. The stability of these photocatalysts and the reaction mechanism of the photocatalytic hydrogen generation are also discussed in detail. (author)

Controlled synthesis and photocatalytic investigation of different-shaped one-dimensional titanic acid nanomaterials

Science.gov (United States)

Li, Qiuye; Lu, Gongxuan

Different-shaped one-dimensional (1D) titanic acid nanomaterials (TANs) were prepared by hydrothermal synthesis. By changing the reaction temperature (120, 170 and 200 °C), three kinds of 1D TAN, short-nanotubes (SNT), long-nanotubes (LNT), and nanorods (NR), were obtained. The obtained TANs were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), and solid-stated diffuse reflectance UV-vis spectra (UV-vis DRS) techniques. Based on these 1D TAN, Eosin Y-sensitized Pt-loaded TAN were prepared by the in situ impregnation and photo-reduction method. Their photocatalytic activity for hydrogen generation was evaluated in triethanolamine (TEOA) aqueous solution under visible light irradiation (λ ≥ 420 nm). The results indicated that the morphology difference led to a significant variation of photocatalytic performance for hydrogen generation, with the activity order as follows: Eosin Y-sensitized Pt-loaded LNT > Eosin Y-sensitized Pt-loaded NR > Eosin Y-sensitized Pt-loaded SNT. The experimental conditions for photocatalytic hydrogen generation such as Pt loading content, the mass ratio of Eosin Y to TAN, and so on, were optimized. As a result, the highest apparent quantum yields of hydrogen generation for Eosin Y-sensitized Pt-loaded SNT, LNT, and NR were 6.65, 17.36, and 15.04%, respectively. The stability of these photocatalysts and the reaction mechanism of the photocatalytic hydrogen generation are also discussed in detail.

Elaboration de plateformes biomimétiques à base de dopamine pour la fonctionnalisation du titane Elaboration of biomimetic dopamine platforms for the functionalization of titanium surfaces

Directory of Open Access Journals (Sweden)

Laure William

2013-11-01

Full Text Available L'étude concerne la fonctionnalisation de surfaces à base de titane à partir d'une ancre chimique biomimétique modifiable chimiquement, la dopamine, dans le but de concevoir des biomatériaux utilisables en tant que dispositifs implantables. Deux approches différentes de greffage par la stratégie «graft to» sont proposées. La première consiste en la synthèse et l'immobilisation sur les surfaces de titane de polymères parfaitement définis et stimulables fonctionnalisés par un motif catéchol en extrémité de chaîne. La seconde propose de modifier préalablement la surface par une ancre chimique spécifique intégrant un motif catéchol d'une part et un motif furane ou maléimide d'autre part permettant d'engager sur demande une réaction réversible de cycloaddition de type Diels Alder (DA avec une large gamme de molécules ou polymères fonctionnalisés par l'entité complémentaire. The aim of this study concerns the functionalization of titanium surfaces by using versatile dopamine based on biomimetic anchors. This general concept was exploited to design new biomaterials which might be used as medical implants. In this context, two different grafting strategies based onto the “grafting to” approach were developed. The first one consisted on the synthesis and the immobilization of well-defined catechol end-functionalized polymers onto titanium surfaces. The second strategy was based on the functionalization of titanium surfaces by using dopamine derivates containing, on the one hand, a catechol unit for surface attachment and, on the other hand, a furan or a maleimide moiety able to react, on demand, through reversible Diels Alder (DA reaction.

Isotherms of ion exchange on titanates of alkaline metals

International Nuclear Information System (INIS)

Fillina, L.P.; Belinskaya, F.A.

1986-01-01

Present article is devoted to isotherms of ion exchange on titanates of alkaline metals. Therefore, finely dispersed hydrated titanates of alkaline metals (lithium, sodium, potassium) with ion exchange properties are obtained by means of alkaline hydrolysis of titanium chloride at high ph rates. Sorption of cations from salts solution of Li 2 SO 4 , NaNO 3 , Ca(NO 3 ) 2 , AgNO 3 by titanates is studied.

Titan Lifting Entry & Atmospheric Flight (T-LEAF) Science Mission

Science.gov (United States)

Lee, G.; Sen, B.; Ross, F.; Sokol, D.

2016-12-01

Northrop Grumman has been developing the Titan Lifting Entry & Atmospheric Flight (T-LEAF) sky rover to roam the lower atmosphere and observe at close quarters the lakes and plains of Saturn's ocean moon, Titan. T-LEAF also supports surface exploration and science by providing precision delivery of in-situ instruments to the surface of Titan. T-LEAF is a highly maneuverable sky rover and its aerodynamic shape (i.e., a flying wing) does not restrict it to following prevailing wind patterns on Titan, but allows mission operators to chart its course. This freedom of mobility allows T-LEAF to follow the shorelines of Titan's methane lakes, for example, or to target very specific surface locations. We will present a straw man concept of T-LEAF, including size, mass, power, on-board science payloads and measurement, and surface science dropsonde deployment CONOPS. We will discuss the various science instruments and their vehicle level impacts, such as meteorological and electric field sensors, acoustic sensors for measuring shallow depths, multi-spectral imagers, high definition cameras and surface science dropsondes. The stability of T-LEAF and its long residence time on Titan will provide for time to perform a large aerial survey of select prime surface targets deployment of dropsondes at selected locations surface measurements that are coordinated with on-board remote measurements communication relay capabilities to orbiter (or Earth). In this context, we will specifically focus upon key factors impacting the design and performance of T-LEAF science: science payload accommodation, constraints and opportunities characteristics of flight, payload deployment and measurement CONOPS in the Titan atmosphere. This presentation will show how these factors provide constraints as well as enable opportunities for novel long duration scientific studies of Titan's surface.

Facile and large-scale synthesis and characterization of carbon nanotube/silver nanocrystal nanohybrids

International Nuclear Information System (INIS)

Gao Chao; Li Wenwen; Jin Yizheng; Kong Hao

2006-01-01

A facile and efficient aqueous phase-based strategy to synthesize carbon nanotube (CNT)/silver nanocrystal nanohybrids at room temperature is reported. In the presence of carboxyl group functionalized or poly(acrylic acid)- (PAA-) grafted CNTs, silver nanoparticles were in situ generated from AgNO 3 aqueous solution, without any additional reducing agent or irradiation treatment, and readily attached to the CNT convex surfaces, leading to the CNT/Ag nanohybrids. The produced silver nanoparticles were determined to be face-centred cubic silver nanocrystals by scanning transmission electron microscopy (STEM), electron diffraction (ED) and x-ray powder diffraction (XRD) analyses. Detailed experiments showed that this strategy can also be applied to different CNTs, including single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs), multiwalled carbon nanotubes (MWNTs), and polymer-functionalized CNTs. The nanoparticle sizes can be controlled from 2 nm to 10-20 nm and the amount of metal deposited on CNT surfaces can be as high as 82 wt%. Furthermore, large-scale (10 g or more) CNT/Ag nanohybrids can be prepared via this approach without the decrease of efficiency and quality. This approach can also be extended to prepare Au single crystals by CNTs. The facile, efficient and large-scale availability of the nanohybrids makes their tremendous potential realizable and developable

Experimental simulations of ethylene evaporites on Titan

Science.gov (United States)

Czaplinski, E.; Farnsworth, K.; Singh, S.; Chevrier, V.

2017-12-01

Titan has an abundance of lakes and seas, as identified by the Cassini spacecraft. Major components of these liquid bodies include methane (CH4) and ethane (C2H6), however minor constituents are also thought to exist (e.g. ethylene (C2H4)). As the lakes and seas evaporate, 5-μm-bright deposits, resembling evaporite deposits on Earth, are left behind in a "bathtub ring" fashion. Previous studies include models of evaporites, and observations of the 5-μm-bright regions, but the community is still lacking a complete suite of experimental evaporite studies. In this study, we experimentally investigate evaporites in order to determine their composition and how they affect infrared spectra during the evaporation process. The University of Arkansas owns a specialized chamber that simulates the surface conditions of Titan ( 90 K and 1.5 bar). Gaseous hydrocarbons are condensed within the chamber and analyzed with Fourier Transform Infrared (FTIR) Spectroscopy and band depth calculations. In this study, three types of experiments were performed: ethane/ethylene, methane/ethylene, and methane/ethane/ethylene. For these experiments, methane was the only species that readily evaporated at Titan conditions (due to its high volatility), while ethane, being the more stable solvent, did not readily evaporate. Therefore, we will present spectral results of ethylene evaporite formation within these mixtures. Our results imply that evaporite formation is strongly dependent on the composition of the solvent. The north polar lakes of Titan are predicted to be methane-rich, indicating that they may be more likely to form evaporites. Alternatively, Ontario Lacus, a south polar lake, is predominately composed of ethane, which may make it more difficult to form evaporites. As we continue to study Titan's mysterious lakes and seas, we hope to draw insights on their exact composition, conditions for evaporite formation, habitability potential, and comparing Titan to prebiotic Earth.

Titan's Topography and Shape at the End of the Cassini Mission

Science.gov (United States)

Corlies, P.; Hayes, A. G.; Birch, S. P. D.; Lorenz, R.; Stiles, B. W.; Kirk, R.; Poggiali, V.; Zebker, H.; Iess, L.

2017-12-01

With the conclusion of the Cassini mission, we present an updated topographic map of Titan, including all the available altimetry, SARtopo, and stereophotogrammetry topographic data sets available from the mission. We use radial basis functions to interpolate the sparse data set, which covers only ˜9% of Titan's global area. The most notable updates to the topography include higher coverage of the poles of Titan, improved fits to the global shape, and a finer resolution of the global interpolation. We also present a statistical analysis of the error in the derived products and perform a global minimization on a profile-by-profile basis to account for observed biases in the input data set. We find a greater flattening of Titan than measured, additional topographic rises in Titan's southern hemisphere and better constrain the possible locations of past and present liquids on Titan's surface.

Application of TITAN for Simulation of Particle Streaming in a Duct

Directory of Open Access Journals (Sweden)

Royston Katherine

2016-01-01

Full Text Available The TITAN hybrid deterministic transport code is applied to the simulation of particle streaming in a nuclear power plant duct. A simple model is used consisting of a concrete duct emerging from the pressure vessel with an isotropic surface source with a U-235 fission spectrum located at the pressure vessel end. Multiple methods of simulating the duct using the TITAN code are considered to demonstrate the flexibility of the code and the advantages of TITAN's algorithms. These methods include a discrete ordinates (SN calculation, a characteristics method calculation, and the use of a fictitious quadrature set with simplified ray-tracing. The TITAN code's results are compared with MCNP5 solutions. While all TITAN solutions are obtained in a shorter computation time than the MCNP5 solution, the TITAN solution with the fictitious quadrature set shows the largest speedup.

Tritium systems for the TITAN reversed-field pinch fusion reactor design

International Nuclear Information System (INIS)

Martin, R.C.; Sze, D.K.; Bartlit, J.R.; Gierszewski, P.J.

1987-01-01

Tritium systems for the TITAN reversed-field pinch (RFP) fusion reactor study have been designed for two blanket concepts. The TITAN-1 design uses a self-cooled liquid-lithium blanket. The TITAN-2 design uses a self-cooled aqueous-solution blanket, with lithium nitrate dissolved in the water for tritium breeding. Tritium inventory, release, and safety margins are within regulatory limits, at acceptable costs. Major issues for TITAN-1 are plasma-driven permeation, the need for a secondary coolant loop, tritium storage requirements, redundancy in the plasma exhaust system, and minimal isotopic distillation of the exhaust. TITAN-1 fuel cleanup, reprocessing, and air detritiation systems are described in detail

The seasonal cycle of Titan's detached haze

Science.gov (United States)

West, Robert A.; Seignovert, Benoît; Rannou, Pascal; Dumont, Philip; Turtle, Elizabeth P.; Perry, Jason; Roy, Mou; Ovanessian, Aida

2018-04-01

Titan's `detached' haze, seen in Voyager images in 1980 and 1981 and monitored by the Cassini Imaging Science Subsystem (ISS) during the period 2004-2017, provides a measure of seasonal activity in Titan's mesosphere with observations over almost half of Saturn's seasonal cycle. Here we report on retrieved haze extinction profiles that reveal a depleted layer (having a diminished aerosol content), visually manifested as a gap between the main haze and a thin, detached upper layer. Our measurements show the disappearance of the feature in 2012 and its reappearance in 2016, as well as details after the reappearance. These observations highlight the dynamical nature of the detached haze. The reappearance seems congruent with earlier descriptions by climate models but more complex than previously described. It occurs in two steps, first as haze reappearing at 450 ± 20 km and one year later at 510 ± 20 km. These observations provide additional tight and valuable constraints about the underlying mechanisms, especially for Titan's mesosphere, that control Titan's haze cycle.

Multistep structural transition of hydrogen trititanate nanotubes into TiO{sub 2}-B nanotubes: a comparison study between nanostructured and bulk materials

Energy Technology Data Exchange (ETDEWEB)

Morgado, Edisson Jr [PETROBRAS S.A./CENPES, Research and Development Centre, Avenida Horacio Macedo, 950, Cidade Universitaria, Quadra 7, 21941-598 Rio de Janeiro-RJ (Brazil); Jardim, P M [Department of Materials Science and Metallurgy, Pontifical Catholic University, CP 38008, 22453-900 Rio de Janeiro-RJ (Brazil); Marinkovic, Bojan A [Department of Materials Science and Metallurgy, Pontifical Catholic University, CP 38008, 22453-900 Rio de Janeiro-RJ (Brazil); Rizzo, Fernando C [Department of Materials Science and Metallurgy, Pontifical Catholic University, CP 38008, 22453-900 Rio de Janeiro-RJ (Brazil); Abreu, Marco A S de [PETROBRAS S.A./CENPES, Research and Development Centre, Avenida Horacio Macedo, 950, Cidade Universitaria, Quadra 7, 21941-598 Rio de Janeiro-RJ (Brazil); Zotin, Jose L [PETROBRAS S.A./CENPES, Research and Development Centre, Avenida Horacio Macedo, 950, Cidade Universitaria, Quadra 7, 21941-598 Rio de Janeiro-RJ (Brazil); Araujo, Antonio S [Department of Chemistry, Federal University of Rio Grande do Norte, CP 1662, 59078-970 Natal-RN (Brazil)

2007-12-12

H-trititanate nanotubes obtained by alkali hydrothermal treatment of TiO{sub 2} followed by proton exchange were compared to their bulk H{sub 2}Ti{sub 3}O{sub 7} counterpart with respect to their thermally induced structural transformation paths. As-synthesized and heat-treated samples were characterized by XRD, TEM/SAED, DSC and spectroscopy techniques, indicating that H{sub 2}Ti{sub 3}O{sub 7} nanotubes showed the same sequence of structural transformations as their bulk counterpart obtained by conventional solid state reaction. Nanostructured H{sub 2}Ti{sub 3}O{sub 7} converts into TiO{sub 2}(B) via multistep transformation without losing its nanotubular morphology. The transformation occurs between 120 and 400 deg. C through topotactic mechanisms with the intermediate formation of nanostructured H{sub 2}Ti{sub 6}O{sub 13} and H{sub 2}Ti{sub 12}O{sub 25}, which are more condensed layered titanates eventually rearranging to TiO{sub 2}(B). Our results suggest that the intermediate tunnel structure H{sub 2}Ti{sub 12}O{sub 25} is the final layered intermediate phase, on which TiO{sub 2}(B) nucleates and grows. The conversion of nanostructured TiO{sub 2}(B) into anatase is completed at a much lower temperature than its bulk counterpart and is accompanied by loss of the nanotubular morphology.

The tide in the seas of Titan

International Nuclear Information System (INIS)

Sagan, C.; Dermott, S.F.

1982-01-01

It is argued that, if Titan has oceans consisting of liquid methane, then the present high eccentricity of the satellite necessitates that the depth would be greater than 400 m. Such an ocean should be detectable by radar. The effects of tidal dissipation due to the possible existence of an ocean on Titan are considered. (author)

Landscape Evolution of Titan

Science.gov (United States)

Moore, Jeffrey

2012-01-01

Titan may have acquired its massive atmosphere relatively recently in solar system history. The warming sun may have been key to generating Titan's atmosphere over time, starting from a thin atmosphere with condensed surface volatiles like Triton, with increased luminosity releasing methane, and then large amounts of nitrogen (perhaps suddenly), into the atmosphere. This thick atmosphere, initially with much more methane than at present, resulted in global fluvial erosion that has over time retreated towards the poles with the removal of methane from the atmosphere. Basement rock, as manifested by bright, rough, ridges, scarps, crenulated blocks, or aligned massifs, mostly appears within 30 degrees of the equator. This landscape was intensely eroded by fluvial processes as evidenced by numerous valley systems, fan-like depositional features and regularly-spaced ridges (crenulated terrain). Much of this bedrock landscape, however, is mantled by dunes, suggesting that fluvial erosion no longer dominates in equatorial regions. High midlatitude regions on Titan exhibit dissected sedimentary plains at a number of localities, suggesting deposition (perhaps by sediment eroded from equatorial regions) followed by erosion. The polar regions are mainly dominated by deposits of fluvial and lacustrine sediment. Fluvial processes are active in polar areas as evidenced by alkane lakes and occasional cloud cover.

Reduced-graphene-oxide-and-strontium-titanate-based double

Indian Academy of Sciences (India)

Microwave-absorbing materials based on reduced graphene oxide (r-GO)/ strontium titanate were prepared by embedding in epoxy matrix. R-GO and strontium titanate were synthesized and characterized before composite fabrication. Microstructures of the constituent elements were studied by scanning electron ...

Cation interdiffusion in polycrystalline calcium and strontium titanate

International Nuclear Information System (INIS)

Butler, E.P.; Jain, H.; Smyth, D.M.

1991-01-01

This paper discusses a method that has been developed to study bulk lattice interdiffusion between calcium and strontium titanate by fabrication of a diffusion couple using cosintering. The measured interdiffusion coefficients, D(C), indicate that strontium impurity diffusion in calcium titanate occurs at a faster rate than calcium impurity diffusion in strontium titanate. These interdiffusion coefficients are composition independent when the concentration of the calcium cation exceeds that of the strontium cation; otherwise D(C) is strongly composition dependent. Investigations into the effect of cation nonstoichiometry give results that are consistent with a defect incorporation reaction in which excess TiO 2 , within the solid solubility limit, produces A-site cation vacancies as compensating defects. The interdiffusion coefficients increase with increasing concentrations of TiO 2 , so it is concluded that interdiffusion of these alkaline-earth cations in their titanates occurs via a vacancy mechanism

Mission Techniques for Exploring Saturn's icy moons Titan and Enceladus

Science.gov (United States)

Reh, Kim; Coustenis, Athena; Lunine, Jonathan; Matson, Dennis; Lebreton, Jean-Pierre; Vargas, Andre; Beauchamp, Pat; Spilker, Tom; Strange, Nathan; Elliott, John

2010-05-01

The future exploration of Titan is of high priority for the solar system exploration community as recommended by the 2003 National Research Council (NRC) Decadal Survey [1] and ESA's Cosmic Vision Program themes. Cassini-Huygens discoveries continue to emphasize that Titan is a complex world with very many Earth-like features. Titan has a dense, nitrogen atmosphere, an active climate and meteorological cycles where conditions are such that the working fluid, methane, plays the role that water does on Earth. Titan's surface, with lakes and seas, broad river valleys, sand dunes and mountains was formed by processes like those that have shaped the Earth. Supporting this panoply of Earth-like processes is an ice crust that floats atop what might be a liquid water ocean. Furthermore, Titan is rich in very many different organic compounds—more so than any place in the solar system, except Earth. The Titan Saturn System Mission (TSSM) concept that followed the 2007 TandEM ESA CV proposal [2] and the 2007 Titan Explorer NASA Flagship study [3], was examined [4,5] and prioritized by NASA and ESA in February 2009 as a mission to follow the Europa Jupiter System Mission. The TSSM study, like others before it, again concluded that an orbiter, a montgolfiѐre hot-air balloon and a surface package (e.g. lake lander, Geosaucer (instrumented heat shield), …) are very high priority elements for any future mission to Titan. Such missions could be conceived as Flagship/Cosmic Vision L-Class or as individual smaller missions that could possibly fit within NASA's New Frontiers or ESA's Cosmic Vision M-Class budgets. As a result of a multitude of Titan mission studies, several mission concepts have been developed that potentially fit within various cost classes. Also, a clear blueprint has been laid out for early efforts critical toward reducing the risks inherent in such missions. The purpose of this paper is to provide a brief overview of potential Titan (and Enceladus) mission

Detailed exploration of Titan with a Montgolfiere aerobot

Science.gov (United States)

Spilker, T.; Tipex Team

The International Cassini/Huygens (CH) mission has verified the expectation that Saturn's moon Titan offers many opportunities for studying high-priority planetary and astrobiology science objectives. CH results to date show that this world, though entirely alien in its frigid environment, presents an Earth-like and diverse appearance due to the relative balance of competing forces such as geology/tectonics, meteorology, aeronomy, and cosmic impacts. But with the limitations of a single Huygens probe, and a finite number of Cassini flybys limited in proximity and remote sensing resolution by Titan's thick atmosphere and hazes, there is much science to be done there after the CH mission has ended. Detailed exploration of Titan's surface and lower atmosphere, especially for astrobiological objectives, is best addressed by in situ investigations. The atmosphere and its hazes severely restrict orbital remote sensing: Titan cannot be mapped from orbit in the same manner as Mars, at (essentially) arbitrarily high resolution, and limited infrared (IR) windows allow only gross compositional interpretations. After CH indeed there will be further orbital investigations to be carried out, notably completion of the global mapping by Synthetic Aperture Radar and IR mapping spectrometry begun by CH, at the best resolutions practical from orbit. But to fully understand Titan as an evolving, planetary-scale body and an abode of preserved protobiological chemistry will require a platform that has access to, and mobility at, the surface and the lowest few kilometers of the atmosphere. The TiPEx study team weighed the options for Titan in situ exploration, and finds that a mission based on a Montgolfiere (a type of hot-air balloon) aerobot is the best candidate for post-CH exploration. Ground-based platforms of the type used to date on Mars are far too limited in range to sample the diversity of Titan, and do not adequately investigate the lower atmosphere. Titan's cold, dense

Surface-Atmosphere Connections on Titan: A New Window into Terrestrial Hydroclimate

Science.gov (United States)

Faulk, Sean

This dissertation investigates the coupling between the large-scale atmospheric circulation and surface processes on Titan, with a particular focus on methane precipitation and its influence on surface geomorphology and hydrology. As the only body in the Solar System with an active hydrologic cycle other than Earth, Titan presents a valuable laboratory for studying principles of hydroclimate on terrestrial planets. Idealized general circulation models (GCMs) are used here to test hypotheses regarding Titan's surface-atmosphere connections. First, an Earth-like GCM simulated over a range of rotation rates is used to evaluate the effect of rotation rate on seasonal monsoon behavior. Slower rotation rates result in poleward migration of summer rain, indicating a large-scale atmospheric control on Titan's observed dichotomy of dry low latitudes and moist high latitudes. Second, a Titan GCM benchmarked against observations is used to analyze the magnitudes and frequencies of extreme methane rainstorms as simulated by the model. Regional patterns in these extreme events correlate well with observed geomorphic features, with the most extreme rainstorms occurring in mid-latitude regions associated with high alluvial fan concentrations. Finally, a planetary surface hydrology scheme is developed and incorporated into a Titan GCM to evaluate the roles of surface flow, subsurface flow, infiltration, and groundmethane evaporation in Titan's climate. The model reproduces Titan's observed surface liquid and cloud distributions, and reaches an equilibrium state with limited interhemispheric transport where atmospheric transport is approximately balanced by subsurface transport. The equilibrium state suggests that Titan's current hemispheric surface liquid asymmetry, favoring methane accumulation in the north, is stable in the modern climate.

Enhancement in thermal property and mechanical property of phase change microcapsule with modified carbon nanotube

International Nuclear Information System (INIS)

Li, Min; Chen, Meirong; Wu, Zhishen

2014-01-01

Highlights: • Carbon nanotubes was grafted and used to enhance the thermal conductivities of the microcapsules. • The average particle size of the prepared MicroPCMs/CNTs-SA is 0.1 μm. • The thermal conductivity of MicroPCMs/CNTs-SA with 4% of CNTs increased by 79.2% compared with MicroPCMs. • MicroPCMs/CNTs-SA has better durability and thermal stability compared to the original MicroPCMs. - Abstract: Carbon nanotubes grafted with stearyl alcohol (CNTs-SA) was used in synthesizing phase change microcapsules (MicroPCMs) in order to enhance the thermal conductivities of the microcapsules. Urea–formaldehyde resin (UFR) was used as wall material. Scanning Electron Microscope (SEM), laser particle size analyzer, Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimeter (DSC) are employed to characterize the prepared MicroPCMs containing the grafted CNTs (MicroPCMs/CNTs-SA). The results indicated that CNTs improved the performance of microcapsules. The average particle diameter of MicroPCMs/CNTs-SA is much smaller than that of MicroPCMs. There was no chemical reaction among paraffin, CNTs and UFR. The phase change temperature and latent heat of MicroPCMs/CNTs-SA was 26.2 °C and 47.7 J/g, respectively. The thermal conductivity of MicroPCMs/CNTs-SA with 4% of CNTs increased by 79.2% compared with MicroPCMs. The initial decomposition temperature of MicroPCMs/CNTs-SA is 38 °C higher than that of MicroPCMs. After 100 heating and cooling cycles, MicroPCMs/CNTs-SA still has good durability and thermal stability

Radiolytic Synthesis of Pt-Ru Catalysts Based on Functional Polymer-Grafted MWNT and Their Catalytic Efficiency for CO and MeOH

Directory of Open Access Journals (Sweden)

Dae-Soo Yang

2011-01-01

Full Text Available Pt-Ru catalysts based on functional polymer-grafted MWNT (Pt-Ru@FP-MWNT were prepared by radiolytic deposition of Pt-Ru nanoparticles on functional polymer-grafted multiwalled carbon nanotube (FP-MWNT. Three different types of functional polymers, poly(acrylic acid (PAAc, poly(methacrylic acid (PMAc, and poly(vinylphenyl boronic acid (PVPBAc, were grafted on the MWNT surface by radiation-induced graft polymerization (RIGP. Then, Pt-Ru nanoparticles were deposited onto the FP-MWNT supports by the reduction of metal ions using γ-irradiation to obtain Pt-Ru@FP-MWNT catalysts. The Pt-Ru@FP-MWNT catalysts were then characterized by XRD, XPS, TEM ,and elemental analysis. The catalytic efficiency of Pt-Ru@FP-MWNT catalyst was examined for CO stripping and MeOH oxidation for use in a direct methanol fuel cell (DMFC. The Pt-Ru@PVPBAc-MWNT catalyst shows enhanced activity for electro-oxidation of CO and MeOH oxidation over that of the commercial E-TEK catalyst.

Progressive Climate Change on Titan: Implications for Habitability

Science.gov (United States)

Moore, J. M.; A. D. Howard

2014-01-01

Titan's landscape is profoundly shaped by its atmosphere and comparable in magnitude perhaps with only the Earth and Mars amongst the worlds of the Solar System. Like the Earth, climate dictates the intensity and relative roles of fluvial and aeolian activity from place to place and over geologic time. Thus Titan's landscape is the record of climate change. We have investigated three broad classes of Titan climate evolution hypotheses (Steady State, Progressive, and Cyclic), regulated by the role, sources, and availability of methane. We favor the Progressive hypotheses, which we will outline here, then discuss their implication for habitability.

Decontamination of 2-chloroethyl ethylsulfide using titanate nanoscrolls

Science.gov (United States)

Kleinhammes, Alfred; Wagner, George W.; Kulkarni, Harsha; Jia, Yuanyuan; Zhang, Qi; Qin, Lu-Chang; Wu, Yue

2005-08-01

Titanate nanoscrolls, a recently discovered variant of TiO 2 nanocrystals, are tested as reactive sorbent for chemical warfare agent (CWA) decontamination. The large surface area of the uncapped tubules provides the desired rapid absorption of the contaminant while water molecules, intrinsic constituents of titanate nanoscrolls, provide the necessary chemistry for hydrolytic reaction. In this study the decomposition of 2-chloroethyl ethylsulfide (CEES), a simulant for the CWA mustard, was monitored using 13C NMR. The NMR spectra reveal reaction products as expected from the hydrolysis of CEES. This demonstrates that titanate nanoscrolls could potentially be employed as a decontaminant for CWAs.

Crater Topography on Titan: Implications for Landscape Evolution

Science.gov (United States)

Neish, Catherine D.; Kirk, R.L.; Lorenz, R. D.; Bray, V. J.; Schenk, P.; Stiles, B. W.; Turtle, E.; Mitchell, K.; Hayes, A.

2013-01-01

We present a comprehensive review of available crater topography measurements for Saturn's moon Titan. In general, the depths of Titan's craters are within the range of depths observed for similarly sized fresh craters on Ganymede, but several hundreds of meters shallower than Ganymede's average depth vs. diameter trend. Depth-to-diameter ratios are between 0.0012 +/- 0.0003 (for the largest crater studied, Menrva, D approximately 425 km) and 0.017 +/- 0.004 (for the smallest crater studied, Ksa, D approximately 39 km). When we evaluate the Anderson-Darling goodness-of-fit parameter, we find that there is less than a 10% probability that Titan's craters have a current depth distribution that is consistent with the depth distribution of fresh craters on Ganymede. There is, however, a much higher probability that the relative depths are uniformly distributed between 0 (fresh) and 1 (completely infilled). This distribution is consistent with an infilling process that is relatively constant with time, such as aeolian deposition. Assuming that Ganymede represents a close 'airless' analogue to Titan, the difference in depths represents the first quantitative measure of the amount of modification that has shaped Titan's surface, the only body in the outer Solar System with extensive surface-atmosphere exchange.

Synthesis and structural characterization of Ce-doped bismuth titanate

International Nuclear Information System (INIS)

Pavlovic, Nikolina; Srdic, Vladimir V.

2009-01-01

Ce-modified bismuth titanate nanopowders Bi 4-x Ce x Ti 3 O 12 (x ≤ 1) have been synthesized using a coprecipitation method. DTA/TG, FTIR, XRD, SEM/EDS and BET methods were used in order to investigate the effect of Ce-substitution on the structure, morphology and sinterability of the obtained powders. The phase structure investigation revealed that after calcinations at 600 deg. C powder without Ce addition exhibited pure bismuth titanate phase; however, powders with Ce (x = 0.25, 0.5 and 0.75) had bismuth titanate pyrochlore phase as the second phase. The strongest effect of Ce addition on the structure was noted for the powder with the highest amount of Ce (x = 1) having a cubic pyrochlore structure. The presence of pure pyrochlore phase was explained by its stabilization due to the incorporation of cerium ions in titanate structure. Ce-modified bismuth titanate ceramic had a density over 95% of theoretical density and the fracture in transgranular manner most probably due to preferable distribution of Ce in boundary region

Grafting polymer coatings onto the surfaces of carbon nanotube forests and yarns via a photon irradiation process

Energy Technology Data Exchange (ETDEWEB)

Deng Fei; Rujisamphan, N.; Liu Chang; Ismat Shah, S.; Ni Chaoying [Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716 (United States); Maezono, Yoshinari [Department of Project Promotion, USHIO INC., 1194, Sazuchi, Bessho-cho, Himeji Hyogo 671-0224 (Japan); Hawkins, Stephen C.; Huynh, Chi P. [Materials Science and Engineering, CSIRO, Bayview Avenue, Clayton, Victoria 3168 (Australia)

2012-05-21

Surface activation of carbon nanotubes (CNTs) as forests and yarns, depolytmerization of candidate polymers, and uniform deposition and re-polymerization onto the activated CNTs are simultaneously achieved by exposing CNTs and polymer targets to light with a narrow wavelength distribution from a vacuum ultraviolet lamp. Both polystyrene and poly (methyl methacrylate) are deposited onto the surface of CNTs in the CNT-forest and yarn in a N{sub 2} environment for 30 min during which the polymer uniformly coats the carbon nanotubes. X-ray photoelectron spectroscopy data reveal that covalent bonding occurs at the CNT-polymer interface.

Grafting polymer coatings onto the surfaces of carbon nanotube forests and yarns via a photon irradiation process

International Nuclear Information System (INIS)

Deng Fei; Rujisamphan, N.; Liu Chang; Ismat Shah, S.; Ni Chaoying; Maezono, Yoshinari; Hawkins, Stephen C.; Huynh, Chi P.

2012-01-01

Surface activation of carbon nanotubes (CNTs) as forests and yarns, depolytmerization of candidate polymers, and uniform deposition and re-polymerization onto the activated CNTs are simultaneously achieved by exposing CNTs and polymer targets to light with a narrow wavelength distribution from a vacuum ultraviolet lamp. Both polystyrene and poly (methyl methacrylate) are deposited onto the surface of CNTs in the CNT-forest and yarn in a N 2 environment for 30 min during which the polymer uniformly coats the carbon nanotubes. X-ray photoelectron spectroscopy data reveal that covalent bonding occurs at the CNT-polymer interface.

Heavy Ion Formation in Titan's Ionosphere: Magnetospheric Introduction of Free Oxygen and a Source of Titan's Aerosols?

Science.gov (United States)

Sittler, E. C., Jr.; Ali, A.; Cooper, J. F.; Hartle, R. E.; Johnson, R. E.; Coates, A. J.; Young, D. T.

2009-01-01

Discovery by Cassini's plasma instrument of heavy positive and negative ions within Titan's upper atmosphere and ionosphere has advanced our understanding of ion neutral chemistry within Titan's upper atmosphere, primarily composed of molecular nitrogen, with approx.2.5% methane. The external energy flux transforms Titan's upper atmosphere and ionosphere into a medium rich in complex hydrocarbons, nitriles and haze particles extending from the surface to 1200 km altitudes. The energy sources are solar UV, solar X-rays, Saturn's magnetospheric ions and electrons, solar wind and shocked magnetosheath ions and electrons, galactic cosmic rays (CCR) and the ablation of incident meteoritic dust from Enceladus' E-ring and interplanetary medium. Here it is proposed that the heavy atmospheric ions detected in situ by Cassini for heights >950 km, are the likely seed particles for aerosols detected by the Huygens probe for altitudes <100km. These seed particles may be in the form of polycyclic aromatic hydrocarbons (PAH) containing both carbon and hydrogen atoms CnHx. There could also be hollow shells of carbon atoms, such as C60, called fullerenes which contain no hydrogen. The fullerenes may compose a significant fraction of the seed particles with PAHs contributing the rest. As shown by Cassini, the upper atmosphere is bombarded by magnetospheric plasma composed of protons, H(2+) and water group ions. The latter provide keV oxygen, hydroxyl and water ions to Titan's upper atmosphere and can become trapped within the fullerene molecules and ions. Pickup keV N(2+), N(+) and CH(4+) can also be implanted inside of fullerenes. Attachment of oxygen ions to PAH molecules is uncertain, but following thermalization O(+) can interact with abundant CH4 contributing to the CO and CO2 observed in Titan's atmosphere. If an exogenic keV O(+) ion is implanted into the haze particles, it could become free oxygen within those aerosols that eventually fall onto Titan's surface. The process

Optimization of single-walled carbon nanotube solubility by noncovalent PEGylation using experimental design methods

Directory of Open Access Journals (Sweden)

Hadidi N

2011-04-01

Full Text Available Naghmeh Hadidi1, Farzad Kobarfard2, Nastaran Nafissi-Varcheh3, Reza Aboofazeli11Department of Pharmaceutics, 2Department of Pharmaceutical Chemistry, 3Department of Pharmaceutical Biotechnology, School of Pharmacy, Shaheed Beheshti University of Medical Sciences, Tehran, IranAbstract: In this study, noncovalent functionalization of single-walled carbon nanotubes (SWCNTs with phospholipid-polyethylene glycols (Pl-PEGs was performed to improve the solubility of SWCNTs in aqueous solution. Two kinds of PEG derivatives, ie, Pl-PEG 2000 and Pl-PEG 5000, were used for the PEGylation process. An experimental design technique (D-optimal design and second-order polynomial equations was applied to investigate the effect of variables on PEGylation and the solubility of SWCNTs. The type of PEG derivative was selected as a qualitative parameter, and the PEG/SWCNT weight ratio and sonication time were applied as quantitative variables for the experimental design. Optimization was performed for two responses, aqueous solubility and loading efficiency. The grafting of PEG to the carbon nanostructure was determined by thermogravimetric analysis, Raman spectroscopy, and scanning electron microscopy. Aqueous solubility and loading efficiency were determined by ultraviolet-visible spectrophotometry and measurement of free amine groups, respectively. Results showed that Pl-PEGs were grafted onto SWCNTs. Aqueous solubility of 0.84 mg/mL and loading efficiency of nearly 98% were achieved for the prepared Pl-PEG 5000-SWCNT conjugates. Evaluation of functionalized SWCNTs showed that our noncovalent functionalization protocol could considerably increase aqueous solubility, which is an essential criterion in the design of a carbon nanotube-based drug delivery system and its biodistribution.Keywords: phospholipid-PEG, D-optimal design, loading efficiency, Raman spectroscopy, scanning electron microscopy, theromogravimetric analysis, carbon nanotubes

Graft-Sparing Strategy for Thoracic Prosthetic Graft Infection.

Science.gov (United States)

Uchino, Gaku; Yoshida, Takeshi; Kakii, Bunpachi; Furui, Masato

2018-04-01

 Thoracic prosthetic graft infection is a rare but serious complication with no standard management. We reported our surgical experience on graft-sparing strategy for thoracic prosthetic graft infection.  This study included patients who underwent graft-sparing surgery for thoracic prosthetic graft infection at Matsubara Tokushukai Hospital in Japan from January 2000 to October 2017.  There were 17 patients included in the analyses, with a mean age at surgery of 71.0 ± 10.5 years; 11 were men. In-hospital mortality was observed in five patients (29.4%).  Graft-sparing surgery for thoracic prosthetic graft infection is an alternative option particularly for early graft infection after hemiarch replacement. Georg Thieme Verlag KG Stuttgart · New York.

Titan's Stratospheric Condensibles at High Northern Latitudes During Northern Winter

Science.gov (United States)

Anderson, Carrie; Samuelson, R.; Achterberg, R.

2012-01-01

The Infrared Interferometer Spectrometer (IRIS) instrument on board Voyager 1 caught the first glimpse of an unidentified particulate feature in Titan's stratosphere that spectrally peaks at 221 per centimeter. Until recently, this feature that we have termed 'the haystack,' has been seen persistently at high northern latitudes with the Composite Infrared Spectrometer (CIRS) instrument onboard Cassini, The strength of the haystack emission feature diminishes rapidly with season, becoming drastically reduced at high northern latitudes, as Titan transitions from northern winter into spring, In contrast to IRIS whose shortest wavenumber was 200 per centimeter, CIRS extends down to 10 per centimeter, thus revealing an entirely unexplored spectral region in which nitrile ices have numerous broad lattice vibration features, Unlike the haystack, which is only found at high northern latitudes during northern winter/early northern spring, this geometrically thin nitrile cloud pervades Titan's lower stratosphere, spectrally peaking at 160 per centimeter, and is almost global in extent spanning latitudes 85 N to 600 S, The inference of nitrile ices are consistent with the highly restricted altitude ranges over which these features are observed, and appear to be dominated by a mixture of HCN and HC3N, The narrow range in altitude over which the nitrile ices extend is unlike the haystack, whose vertical distribution is significantly broader, spanning roughly 70 kilometers in altitude in Titan's lower stratosphere, The nitrile clouds that CIRS observes are located in a dynamically stable region of Titan's atmosphere, whereas CH4 clouds, which ordinarily form in the troposphere, form in a more dynamically unstable region, where convective cloud systems tend to occur. In the unusual situation where Titan's tropopause cools significantly from the HASI 70.5K temperature minimum, CH4 should condense in Titan's lower stratosphere, just like the aforementioned nitrile clouds, although

Thermogravimetric study of the kinetics of lithium titanate reduction by hydrogen

International Nuclear Information System (INIS)

Sonak, Sagar; Rakesh, R.; Jain, Uttam; Mukherjee, Abhishek; Kumar, Sanjay; Krishnamurthy, Nagaiyar

2014-01-01

Highlights: • Li 2 TiO 3 powder is synthesized by the gel combustion route. • Activation energy of reduction of Li 2 TiO 3 by H 2 found out to be 27.45 kJ/mol H 2 . • Non-stoichiometric phase of Li 2 TiO 3 is formed in hydrogen atmosphere. • One-dimensional diffusion appears to be the most probable mechanism of reduction. - Abstract: The lithium titanate powder was synthesized by gel-combustion route. The mechanism and the kinetics of hydrogen interaction with lithium titanate powder were studied using non-isothermal thermogravimetric technique. Lithium titanate underwent reduction in hydrogen atmosphere which led to the formation of oxygen deficient non-stoichiometric compound in lithium titanate. One-dimensional diffusion appeared to be the most probable reaction mechanism. The activation energy for reduction of lithium titanate under hydrogen atmosphere was found to be 27.4 kJ/mol/K. Structural changes after hydrogen reduction in lithium titanate were observed in X-ray diffraction analysis

Screening of spontaneous polarization in lead titanate crystals

International Nuclear Information System (INIS)

Gavrilyachenko, V.G.; Semenchev, A.F.; Fesenko, E.G.

1996-01-01

Results of experimental investigations into electric conductivity of lead titanate crystals with different domain structure including single-domain are reported. The data obtained give grounds to believe that spontaneous titanate polarization is realized by the surface level and charge volumetric of free carriers and ionized impurity

Fabrication and properties of yttrium doped barium titanate film by RF sputtering

International Nuclear Information System (INIS)

Igarashi, H.; Yuasa, M.; Okazaki, K.

1985-01-01

Semiconductive barium titanate films were fabricated by RF sputtering on fused quartz, alumina and barium titanate ceramic substrates using barium titanate ceramic with a small amount of yttria as a target. The films on the barium titanate substrates turned blue color and showed a small PTC effect by heat-treating at 1000 0 C in the air after deposition at the substrate temperature of 600 0 C

Titanic exploration with GIS

Science.gov (United States)

Kerski, J.J.

2004-01-01

To help teachers and students investigate one of the world's most famous historical events using the geographic perspective and GIS tools and methods, the U.S. Geological Survey (USGS) created a set of educational lessons based on the RMS Titanic's April 1912 sailing. With these lessons, student researchers can learn about latitude and longitude, map projections, ocean currents, databases, maps, and images through the analysis of the route, warnings, sinking, rescue, and eventual discovery of the submerged ocean liner in 1985. They can also consider the human and physical aspects of the maiden voyage in the North Atlantic Ocean at a variety of scales, from global to regional to local. Likewise, their investigations can reveal how the sinking of the Titanic affected future shipping routes.

Exfoliation and thermal transformations of Nb-substituted layered titanates

DEFF Research Database (Denmark)

Song, H.; Sjåstad, Anja O.; Fjellvåg, Helmer

2011-01-01

Single-layer Nb-substituted titanate nanosheets of ca. 1 nm thickness were obtained by exfoliating tetrabutylammonium (TBA)-intercalated Nb-substituted titanates in water. AFM images and turbidity measurements reveal that the exfoliated nanosheets crack and corrugate when sonicated. Upon heating...... factors for increasing the transformation temperatures for conversion of the nanosheets to anatase and finally into rutile. It is further tempting to link the delay in crystallization to morphology limitations originating from the nanosheets. The present work shows that layered Nb-titanates...

Polymer functionalized single-walled carbon nanotube composites and semi-fluorinated quaternary ammonium polymer colloids and coatings

Science.gov (United States)

Paul, Abhijit

Scope and Method of Study: Current study focused on understanding of "wetting" and "dewetting" phenomena between surfaces of single-walled carbon nanotubes (SWCNT) which are lightly grafted with polymer chains by reversible-deactivation radical polymerization, when they are mixed with matrix chains of the same architecture as grafts. Effects of grafts to matrix chain lengths on SWCNT dispersion in matrix polymers were studied by measuring electrical conductivity, glass transition temperature, and storage and loss moduli of nanocomposites. Another area of work was to design semi-fluorinated copolymers with core-shell morphology by emulsion polymerization, study their catalytic activities for hydrolyses of Paraoxon, a toxic insecticide, in the forms of both colloidal dispersions and films, and to characterize the surfaces of the films by atomic force microscopy and by dynamic contact angle measurements. Findings and Conclusions: The glass transition temperature ( Tg) of polystyrene (PS) filled with SWCNT grafted with PS of different lengths increased from 99 to 109 °C at 6 wt% of SWCNT followed by a plateau. The heat capacity (DeltaCp ) at Tg continued to decrease only for the smallest chain length grafted PS nanocomposites. SWCNT/PS nanocomposites had low electrical conductivity and showed no percolation threshold due to the thick polymer coatings. A key finding was that the SWCNT surface can accommodate only a fixed numbers of styrene units. Similar results on change in Tg were obtained for SWCNT/PMMA nanocomposites when molecular weight of matrix (Mmatrix) ≥ molecular weight of grafts (Mgraft). No change in DeltaCp was observed for SWCNT/PMMA nanocomposites. "Wetting" to "dewetting" occurred Mmatrix/ Mgraft ≈ 1. For Mmatrix > Mgraft, electrical conductivity of nanocomposites reached the value of 10-9 S cm-1 at 1.0 wt% nanotube loading and had percolation threshold of electrical conductivity at ˜0.25 wt% SWCNT. Raman and UV-vis-NIR data confirmed that

TandEM: Titan and Enceladus mission

Science.gov (United States)

Coustenis, A.; Atreya, S.K.; Balint, T.; Brown, R.H.; Dougherty, M.K.; Ferri, F.; Fulchignoni, M.; Gautier, D.; Gowen, R.A.; Griffith, C.A.; Gurvits, L.I.; Jaumann, R.; Langevin, Y.; Leese, M.R.; Lunine, J.I.; McKay, C.P.; Moussas, X.; Muller-Wodarg, I.; Neubauer, F.; Owen, T.C.; Raulin, F.; Sittler, E.C.; Sohl, F.; Sotin, Christophe; Tobie, G.; Tokano, T.; Turtle, E.P.; Wahlund, J.-E.; Waite, J.H.; Baines, K.H.; Blamont, J.; Coates, A.J.; Dandouras, I.; Krimigis, T.; Lellouch, E.; Lorenz, R.D.; Morse, A.; Porco, C.C.; Hirtzig, M.; Saur, J.; Spilker, T.; Zarnecki, J.C.; Choi, E.; Achilleos, N.; Amils, R.; Annan, P.; Atkinson, D.H.; Benilan, Y.; Bertucci, C.; Bezard, B.; Bjoraker, G.L.; Blanc, M.; Boireau, L.; Bouman, J.; Cabane, M.; Capria, M.T.; Chassefiere, E.; Coll, P.; Combes, M.; Cooper, J.F.; Coradini, A.; Crary, F.; Cravens, T.; Daglis, I.A.; de Angelis, E.; De Bergh, C.; de Pater, I.; Dunford, C.; Durry, G.; Dutuit, O.; Fairbrother, D.; Flasar, F.M.; Fortes, A.D.; Frampton, R.; Fujimoto, M.; Galand, M.; Grasset, O.; Grott, M.; Haltigin, T.; Herique, A.; Hersant, F.; Hussmann, H.; Ip, W.; Johnson, R.; Kallio, E.; Kempf, S.; Knapmeyer, M.; Kofman, W.; Koop, R.; Kostiuk, T.; Krupp, N.; Kuppers, M.; Lammer, H.; Lara, L.-M.; Lavvas, P.; Le, Mouelic S.; Lebonnois, S.; Ledvina, S.; Li, Ji; Livengood, T.A.; Lopes, R.M.; Lopez-Moreno, J. -J.; Luz, D.; Mahaffy, P.R.; Mall, U.; Martinez-Frias, J.; Marty, B.; McCord, T.; Salvan, C.M.; Milillo, A.; Mitchell, D.G.; Modolo, R.; Mousis, O.; Nakamura, M.; Neish, Catherine D.; Nixon, C.A.; Mvondo, D.N.; Orton, G.; Paetzold, M.; Pitman, J.; Pogrebenko, S.; Pollard, W.; Prieto-Ballesteros, O.; Rannou, P.; Reh, K.; Richter, L.; Robb, F.T.; Rodrigo, R.; Rodriguez, S.; Romani, P.; Bermejo, M.R.; Sarris, E.T.; Schenk, P.; Schmitt, B.; Schmitz, N.; Schulze-Makuch, D.; Schwingenschuh, K.; Selig, A.; Sicardy, B.; Soderblom, L.; Spilker, L.J.; Stam, D.; Steele, A.; Stephan, K.; Strobel, D.F.; Szego, K.; Szopa,

2009-01-01

TandEM was proposed as an L-class (large) mission in response to ESA’s Cosmic Vision 2015–2025 Call, and accepted for further studies, with the goal of exploring Titan and Enceladus. The mission concept is to perform in situ investigations of two worlds tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini–Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TandEM is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini–Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time). In the current mission architecture, TandEM proposes to deliver two medium-sized spacecraft to the Saturnian system. One spacecraft would be an orbiter with a large host of instruments which would perform several Enceladus flybys and deliver penetrators to its surface before going into a dedicated orbit around Titan alone, while the other spacecraft would carry the Titan in situ investigation components, i.e. a hot-air balloon (Montgolfière) and possibly several landing probes to be delivered through the atmosphere.

Organic matter in the Titan lakes, and comparison with primitive Earth

Science.gov (United States)

Khare, Bishun N.; McKay, C.; Wilhite, P.; Beeler, D.; Carter, M.; Schurmeier, L.; Jagota, S.; Kawai, J.; Nna-Mvondo, D.; Cruikshank, D.; Embaye, T.

2013-06-01

Titan is the only world in the solar system besides the Earth that has liquid on its surface. The liquid in the lakes is thought to be composed primarily of ethane with methane and nitrogen in solution. The clouds are thought to be composed of liquid methane drops. Surface liquid is present in polar lakes and in surface materials at equatorial sites. Studying the chemical processing that potentially results from organic material interacting with this liquid is one of the main goals of proposed missions to Titan. We have been engaged in producing tholin under Titan-like conditions for more than three decades, first at the Laboratory for Planetary Studies at Cornell University in collaboration with Late Dr. Carl Sagan and for over a decade at Laboratory for Planetary Studies at NASA Ames Research Center and Carl Sagan Center for the Study of Life in the Universe, SETI Institute. Our focus is to understand the capabilities for analysis of tholin solubility in liquid methane and ethane for flight instruments. Our results are expected to contribute to an understanding of the organic chemistry on Titan and to the development of an explicit and targeted scientific strategy for near term analysis of the products of organic-liquid interactions on Titan. Organics are produced as a haze in Titan's high atmosphere due to photolysis of methane with the Sun's extreme ultraviolet light and subsequent reaction with N. Also tholins are formed at a much higher level on Titan by charged particles of Saturn magnetosphere. However, the presence of organics is not the sole feature, which makes Titan significant to astrobiology; organics are widely present in the outer solar system. The reason Titan is a prime target for future outer solar system missions is the combination of organic material and liquid on the surface; liquid that could over a medium for further organic synthesis. NASA recently selected for further study a Discovery proposal TiME to investigate the chemistry of the

Mussel inspired polymerized P(TA-TETA) for facile functionalization of carbon nanotube

Science.gov (United States)

Si, Shuxian; Gao, Tingting; Wang, Junhao; Liu, Qinze; Zhou, Guowei

2018-03-01

This article describes a novel and effective approach for non-covalent modification of carbon nanotube (CNT) via the mussel inspired polymerization of tannic acid (TA) and triethylenetetramine (TETA) and subsequent surface initiated atom transfer radical polymerization (SI-ATRP). Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and photograph were used to study the successful preparation of polymer brush grafted CNT (CNT-P(TA-TETA)-PDMAEMA) composite as well as the pH-responsive behavior of the composite. Furthermore, by amine protonation and in situ reduction, gold nanoparticles were successfully uploaded and the catalytic property of CNT-P(TA-TETA)-PDMAEMA/Au was investigated. We believe that the surface functionalization strategy can be extended to graphene and other substrates, and the surface properties can be regulated by grafting polymer brushes with different functionalities.

Simulating the 3-D Structure of Titan's Upper Atmosphere

Science.gov (United States)

Bell, J. M.; Waite, H.; Westlake, J.; Magee, B.

2009-05-01

We present results from the 3-D Titan Global Ionosphere-Thermosphere Model (Bell et al [2009], PSS, in review). We show comparisons between simulated N2, CH4, and H2 density fields and the in-situ data from the Cassini Ion Neutral Mass Spectrometer (INMS). We describe the temperature and wind fields consistent with these density calculations. Variations with local time, longitude, and latitude will be addressed. Potential plasma heating sources can be estimated using the 1-D model of De La Haye et al [2007, 2008] and the impacts on the thermosphere of Titan can be assessed in a global sense in Titan-GITM. Lastly, we will place these findings within the context of recent work in modeling the 2-D structure of Titan's upper atmosphere (Mueller-Wodarg et al [2008]).

METHANE GAS STABILIZES SUPERCOOLED ETHANE DROPLETS IN TITAN'S CLOUDS

International Nuclear Information System (INIS)

Wang, Chia C.; Lang, E. Kathrin; Signorell, Ruth

2010-01-01

Strong evidence for ethane clouds in various regions of Titan's atmosphere has recently been found. Ethane is usually assumed to exist as ice particles in these clouds, although the possible role of liquid and supercooled liquid ethane droplets has been recognized. Here, we report on infrared spectroscopic measurements of ethane aerosols performed in the laboratory under conditions mimicking Titan's lower atmosphere. The results clearly show that liquid ethane droplets are significantly stabilized by methane gas which is ubiquitous in Titan's nitrogen atmosphere-a phenomenon that does not have a counterpart for water droplets in Earth's atmosphere. Our data imply that supercooled ethane droplets are much more abundant in Titan's clouds than previously anticipated. Possibly, these liquid droplets are even more important for cloud processes and the formation of lakes than ethane ice particles.

Crater relaxation on Titan aided by low thermal conductivity sand infill

Science.gov (United States)

Schurmeier, Lauren R.; Dombard, Andrew J.

2018-05-01

Titan's few impact craters are currently many hundreds of meters shallower than the depths expected. Assuming these craters initially had depths equal to that of similar-size fresh craters on Ganymede and Callisto (moons of similar size, composition, and target lithology), then some process has shallowed them over time. Since nearly all of Titan's recognized craters are located within the arid equatorial sand seas of organic-rich dunes, where rain is infrequent, and atmospheric sedimentation is expected to be low, it has been suggested that aeolian infill plays a major role in shallowing the craters. Topographic relaxation at Titan's current heat flow was previously assumed to be an unimportant process on Titan due to its low surface temperature (94 K). However, our estimate of the thermal conductivity of Titan's organic-rich sand is remarkably low (0.025 W m-1 K-1), and when in thick deposits, will result in a thermal blanketing effect that can aid relaxation. Here, we simulate the relaxation of Titan's craters Afekan, Soi, and Sinlap including thermal effects of various amounts of sand inside and around Titan's craters. We find that the combination of aeolian infill and subsequent relaxation can produce the current crater depths in a geologically reasonable period of time using Titan's current heat flow. Instead of needing to fill completely the missing volume with 100% sand, only ∼62%, ∼71%, and ∼97%, of the volume need be sand at the current basal heat flux for Afekan, Soi, and Sinlap, respectively. We conclude that both processes are likely at work shallowing these craters, and this finding contributes to why Titan overall lacks impact craters in the arid equatorial regions.

Freeze cast porous barium titanate for enhanced piezoelectric energy harvesting

Science.gov (United States)

Roscow, J. I.; Zhang, Y.; Kraśny, M. J.; Lewis, R. W. C.; Taylor, J.; Bowen, C. R.

2018-06-01

Energy harvesting is an important developing technology for a new generation of self-powered sensor networks. This paper demonstrates the significant improvement in the piezoelectric energy harvesting performance of barium titanate by forming highly aligned porosity using freeze casting. Firstly, a finite element model demonstrating the effect of pore morphology and angle with respect to poling field on the poling behaviour of porous ferroelectrics was developed. A second model was then developed to understand the influence of microstructure-property relationships on the poling behaviour of porous freeze cast ferroelectric materials and their resultant piezoelectric and energy harvesting properties. To compare with model predictions, porous barium titanate was fabricated using freeze casting to form highly aligned microstructures with excellent longitudinal piezoelectric strain coefficients, d 33. The freeze cast barium titanate with 45 vol.% porosity had a d 33  =  134.5 pC N‑1 compared to d 33  =  144.5 pC N‑1 for dense barium titanate. The d 33 coefficients of the freeze cast materials were also higher than materials with uniformly distributed spherical porosity due to improved poling of the aligned microstructures, as predicted by the models. Both model and experimental data indicated that introducing porosity provides a large reduction in the permittivity () of barium titanate, which leads to a substantial increase in energy harvesting figure of merit, , with a maximum of 3.79 pm2 N‑1 for barium titanate with 45 vol.% porosity, compared to only 1.40 pm2 N‑1 for dense barium titanate. Dense and porous barium titanate materials were then used to harvest energy from a mechanical excitation by rectification and storage of the piezoelectric charge on a capacitor. The porous barium titanate charged the capacitor to a voltage of 234 mV compared to 96 mV for the dense material, indicating a 2.4-fold increase that was similar to that

Thermal conductivity reduction in oxygen-deficient strontium titanates

NARCIS (Netherlands)

Yu, Choongho; Scullin, Matthew L.; Huijben, Mark; Ramesh, Ramamoorthy; Majumdar, Arun

2008-01-01

We report significant thermal conductivity reduction in oxygen-deficient lanthanum-doped strontium titanate (Sr1−xLaxTiO3−δ) films as compared to unreduced strontium titanates. Our experimental results suggest that the oxygen vacancies could have played an important role in the reduction. This could

Styrene-butadiene rubber/halloysite nanotubes nanocomposites modified by methacrylic acid

International Nuclear Information System (INIS)

Guo Baochun; Lei Yanda; Chen Feng; Liu Xiaoliang; Du Mingliang; Jia Demin

2008-01-01

Methacrylic acid (MAA) was used to improve the performance of styrene-butadiene rubber (SBR)/halloysite nanotubes (HNTs) nanocomposites by direct blending. The detailed interaction mechanisms of MAA and the in situ formed zinc methacrylate (ZDMA) were revealed by X-ray diffraction (XRD), surface area and porosity analysis, X-ray photoelectron spectroscopy (XPS) together with crosslink density determination. The strong interfacial bonding between HNTs and rubber matrix is resulted through ZDMA and MAA intermediated linkages. ZDMA connects SBR and HNTs via grafting/complexation mechanism. MAA bonds SBR and HNTs through grafting/hydrogen bonding mechanism. Significantly improved dispersion of HNTs in virtue of the interactions between HNTs and MAA or ZDMA was achieved. Effects of MAA content on the vulcanization behavior, morphology and mechanical properties of the nanocomposites were investigated. Promising mechanical properties of MAA modified SBR/HNTs nanocomposites were obtained. The changes in vulcanization behavior, mechanical properties and morphology were correlated with the interactions between HNTs and MAA or ZDMA and the largely improved dispersion of HNTs

Styrene-butadiene rubber/halloysite nanotubes nanocomposites modified by methacrylic acid

Energy Technology Data Exchange (ETDEWEB)

Guo Baochun [Department of Polymer Materials and Engineering, South China University of Technology, Guangzhou 510640 (China)], E-mail: psbcguo@scut.edu.cn; Lei Yanda; Chen Feng; Liu Xiaoliang; Du Mingliang; Jia Demin [Department of Polymer Materials and Engineering, South China University of Technology, Guangzhou 510640 (China)

2008-12-30

Methacrylic acid (MAA) was used to improve the performance of styrene-butadiene rubber (SBR)/halloysite nanotubes (HNTs) nanocomposites by direct blending. The detailed interaction mechanisms of MAA and the in situ formed zinc methacrylate (ZDMA) were revealed by X-ray diffraction (XRD), surface area and porosity analysis, X-ray photoelectron spectroscopy (XPS) together with crosslink density determination. The strong interfacial bonding between HNTs and rubber matrix is resulted through ZDMA and MAA intermediated linkages. ZDMA connects SBR and HNTs via grafting/complexation mechanism. MAA bonds SBR and HNTs through grafting/hydrogen bonding mechanism. Significantly improved dispersion of HNTs in virtue of the interactions between HNTs and MAA or ZDMA was achieved. Effects of MAA content on the vulcanization behavior, morphology and mechanical properties of the nanocomposites were investigated. Promising mechanical properties of MAA modified SBR/HNTs nanocomposites were obtained. The changes in vulcanization behavior, mechanical properties and morphology were correlated with the interactions between HNTs and MAA or ZDMA and the largely improved dispersion of HNTs.

The Greenhouse and Anti-Greenhouse Effects on Titan

Science.gov (United States)

McKay, C. P.; Cuzzi, Jeffrey N. (Technical Monitor)

1994-01-01

Titan is the largest moon of Saturn and is the only moon in the solar system with a substantial atmosphere. Its atmosphere is mostly made of nitrogen, with a few percent CH4, 0.1% H2 and an uncertain level of Ar (less than 10%). The surface pressure is 1.5 atms and the surface temperature is 95 K, decreasing to 71 at the tropopause before rising to stratospheric temperatures of 180 K. In pressure and composition Titan's atmosphere is the closest twin to Earth's. The surface of Titan remains unknown, hidden by the thick smog layer, but it may be an ocean of liquid methane and ethane. Titan's atmosphere has a greenhouse effect which is much stronger than the Earth's - 92% of the surface warming is due to greenhouse radiation. However an organic smog layer in the upper atmosphere produces an anti-greenhouse effect that cuts the greenhouse warming in half - removing 35% of the incoming solar radiation. Models suggest that during its formation Titan's atmosphere was heated to high temperatures due to accretional energy. This was followed by a cold Triton-like period which gradually warmed to the present conditions. The coupled greenhouse and haze anti-greenhouse may be relevant to recent suggestions for haze shielding of a CH4 - NH3 early atmosphere on Earth or Mars. When the NASA/ESA mission to the Saturn System, Cassini, launches in a few years it will carry a probe that will be sent to the surface of Titan and show us this world that is strange and yet in many ways similar to our own.

Synthesis and characterization of novel lanthanide- and actinide-containing titanates and zircono-titanates; relevance to nuclear waste disposal

International Nuclear Information System (INIS)

Shoup, S.L.S.

1995-08-01

Before experiments using actinide elements are performed, synthetic routes are tested using lanthanides of comparable ionic radii as surrogates. Compound and solid solution formation in several lanthanide-containing titanate and zircono-titanate systems have been established using X-ray diffraction (XRD) analysis, which helped to define interesting and novel experiments, some of which have been performed and are discussed, for selected actinide elements. The aqueous solubilities of several lanthanide- and actinide-containing compounds, representative of the systems studied, were tested in several leachants, including the WIPP open-quotes Aclose quotes brine, following modified Materials Characterization Center procedures (MCC-3). The WIPP open-quotes Aclose quotes brine is a synthetic substitute for that found in nature at the Waste Isolation Pilot Plant (WIPP) in New Mexico. The concentrations of cerium, used as a surrogate for plutonium, leached by the WIPP open-quotes Aclose quotes brine from all the cerium-containing compounds and solid solutions tested were below the Inductively Coupled Plasma (ICP) atomic emission spectrometry limit of detection (10 ppm) established for cerium in this brine. The concentrations of plutonium leached from the two plutonium-containing solid solutions were less than 1 ppm as determined by gross alpha counting and alpha pulse height analysis. Concentrations of strontium leached by the WIPP brine from stable strontium containing titanate compounds, studied as possible immobilizers of both 90 Sr and actinide elements, were also quite low. These compound and solid solution formation investigations and the aqueous solubility studies suggest that the types of titanate and zircono-titanate compounds and solid solutions studied in this work appear to be useful as host matrices for nuclear waste immobilization

Barium Titanate Nanoparticles for Biomarker Applications

International Nuclear Information System (INIS)

Matar, O; Hondow, N S; Brydson, R M D; Milne, S J; Brown, A P; Posada, O M; Wälti, C; Saunders, M; Murray, C A

2015-01-01

A tetragonal crystal structure is required for barium titanate nanoparticles to exhibit the nonlinear optical effect of second harmonic light generation (SHG) for use as a biomarker when illuminated by a near-infrared source. Here we use synchrotron XRD to elucidate the tetragonal phase of commercially purchased tetragonal, cubic and hydrothermally prepared barium titanate (BaTiO 3 ) nanoparticles by peak fitting with reference patterns. The local phase of individual nanoparticles is determined by STEM electron energy loss spectroscopy (EELS), measuring the core-loss O K-edge and the Ti L 3 -edge energy separation of the t 2g , e g peaks. The results show a change in energy separation between the t 2g and e g peak from the surface and core of the particles, suggesting an intraparticle phase mixture of the barium titanate nanoparticles. HAADF-STEM and bright field TEM-EDX show cellular uptake of the hydrothermally prepared BaTiO 3 nanoparticles, highlighting the potential for application as biomarkers. (paper)

Enhanced visible-light-responsive photodegradation of bisphenol A by Cu, N-codoped titanate nanotubes prepared by microwave-assisted hydrothermal method

Energy Technology Data Exchange (ETDEWEB)

Doong, Ruey-an, E-mail: radoong@nctu.edu.tw [Institute of Environmental Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Liao, Chun-Yi [Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

2017-01-15

Highlights: • The Cu, N-codoped TNTs were prepared by microwave assisted hydrothermal method. • The Cu(0) in codoped TNTs can serve as electron donors as well as electron meditors. • The surface normalized rate constants for BPA removal by Cu, N-TNT were 1.5–4.3 times higher than that of P25 TiO{sub 2}. • The Cu, N-codoped TNTs prolonged the generation of radicals for at least 5 min. - Abstract: In this study, a rapid and effective microwave-assisted hydrothermal method was developed for the synthesis of Cu, N-codoped titanate nanotubes (Cu, N-TNTs) to enhance the photocatalytic degradation efficiency and rate of bisphenol A (BPA) under UV and visible light irradiations. The TNTs were first synthesized at 150 °C for 3 h under microwave heating conditions followed by the calcination at 450 °C in the presence of 6 wt% Cu ions and N{sub 2}/NH{sub 3} to fabricate Cu, N-TNTs composites. The Cu, N-TNTs exhibited excellent photocatalytic activity toward BPA degradation under UV and visible light irradiations. The X-ray photoelectron spectra indicated that Cu species in Cu, N-TNTs were mainly in zerovalent form and could serve as the electron donors as well as shuttling species to accelerate the photodegradation of BPA. In addition, the nitrogen atoms were incorporated into the anatase lattices to increase the visible-light-responsive capability. The surface normalized reaction rate constants for BPA degradation were 4.3 and 1.5 times higher than those of Degussa P25 TiO{sub 2} under UV and visible light irradiations, respectively. The electron spin resonance spectra showed that Cu, N-codoped TNTs prolonged the generation of oxygen-containing radicals for at least 5 min, resulting in the significant enhancement of photodegradation efficiency and rate of BPA. Results obtained in this study open a new avenue by using simple and effective microwave-assisted hydrothermal method to fabricate low dimensional codoped TNTs which can be potentially applied in a wide

Tritium breeding experiments with lithium titanate in thermal-type mockups

International Nuclear Information System (INIS)

Klix, Axel; Takahashi, Akito; Ochiai, Kentaro; Nishitani, Takeo

2004-01-01

Lithium titanate, an advanced tritium breeding material, is currently investigated in integral mock-up experiments at FNS. A method was developed which allows to measure low tritium concentrations directly in this material. The local tritium production rate was obtained by small lithium titanate pellet detectors inserted into the breeding layers which are dissolved after irradiation of the assemblies, and the accumulated tritium was counted by liquid scintillation techniques. The measurement method was applied in mock0-up experiments with candidate materials for the future DEMO reactor breeding blanket. Experimental assemblies consisted of sheets of low activation ferritic steel F82H, lithium titanate, and berylium. Tritium production rate profiles were obtained and compared with results from calculations with the Monte Carlo neutron transport code MCNP-4C. In case of the mock-ups with 95% enriched lithium titanate, the C/E ratios were within the error estimate while larger discrepancies were observed in case of 40% enriched lithium titanate. (author)

Development of partitioning method: adsorption behavior of Sr on titanic acid pelletized with binder

Energy Technology Data Exchange (ETDEWEB)

Mizoguchi, Kenichi; Yamaguchi, Isoo; Morita, Yasuji; Yamagishi, Isao; Fujiwara, Takeshi; Kubota, Masumitsu [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

1998-05-01

The adsorption behavior of Sr was examined with the titanic acid with the binder and with binderless titanic acid. Then the effect of the difference of the neutralizer was also examined. When the initial concentration of Sr was constant, distribution coefficient (Kd) increased with pH after adsorption. At pH 4, Kd decreased in order of the titanic acid neutralized with NH{sub 4}OH solution without the binder > the titanic acid neutralized with NH{sub 4}OH solution and pelletized with the binder > the titanic acid neutralized with KOH solution and pelletized with the binder. At pH 6, Kd decreased with increasing the concentration of Sr in the solution, but the decreasing tendency of Kd for each titanic acid was the same. Adsorption kinetics was examined with titanic acids neutralized with NH{sub 4}OH solution, keeping the initial concentration of Sr and the initial pH constant. It took about one hour to reach Kd of 100mL/g for the titanic acid without the binder but over 10 hours for the titanic acid pelletized with the binder. It was confirmed that by pelletizing titanic acid with the binder, Kd of Sr became small and it took very long time to reach the adsorption equilibrium. However, by sufficient conditioning with water of the titanic acid pelletized with the binder, 1) it took about half time of titanic acid without conditioning to reach Kd of 100mL/g, 2) after 24 hours mixing, Kd for the titanic acid pelletized with the binder was almost equal to that for the titanic acid without the binder, 3) apparent ion exchange capacity obtained through a column test became over about 1meq/g. (J.P.N.)

Development of partitioning method: adsorption behavior of Sr on titanic acid pelletized with binder

International Nuclear Information System (INIS)

Mizoguchi, Kenichi; Yamaguchi, Isoo; Morita, Yasuji; Yamagishi, Isao; Fujiwara, Takeshi; Kubota, Masumitsu

1998-05-01

The adsorption behavior of Sr was examined with the titanic acid with the binder and with binderless titanic acid. Then the effect of the difference of the neutralizer was also examined. When the initial concentration of Sr was constant, distribution coefficient (Kd) increased with pH after adsorption. At pH 4, Kd decreased in order of the titanic acid neutralized with NH 4 OH solution without the binder > the titanic acid neutralized with NH 4 OH solution and pelletized with the binder > the titanic acid neutralized with KOH solution and pelletized with the binder. At pH 6, Kd decreased with increasing the concentration of Sr in the solution, but the decreasing tendency of Kd for each titanic acid was the same. Adsorption kinetics was examined with titanic acids neutralized with NH 4 OH solution, keeping the initial concentration of Sr and the initial pH constant. It took about one hour to reach Kd of 100mL/g for the titanic acid without the binder but over 10 hours for the titanic acid pelletized with the binder. It was confirmed that by pelletizing titanic acid with the binder, Kd of Sr became small and it took very long time to reach the adsorption equilibrium. However, by sufficient conditioning with water of the titanic acid pelletized with the binder, 1) it took about half time of titanic acid without conditioning to reach Kd of 100mL/g, 2) after 24 hours mixing, Kd for the titanic acid pelletized with the binder was almost equal to that for the titanic acid without the binder, 3) apparent ion exchange capacity obtained through a column test became over about 1meq/g. (J.P.N.)

Plasma environment of Titan: a 3-D hybrid simulation study

Directory of Open Access Journals (Sweden)

S. Simon

2006-05-01

Full Text Available Titan possesses a dense atmosphere, consisting mainly of molecular nitrogen. Titan's orbit is located within the Saturnian magnetosphere most of the time, where the corotating plasma flow is super-Alfvénic, yet subsonic and submagnetosonic. Since Titan does not possess a significant intrinsic magnetic field, the incident plasma interacts directly with the atmosphere and ionosphere. Due to the characteristic length scales of the interaction region being comparable to the ion gyroradii in the vicinity of Titan, magnetohydrodynamic models can only offer a rough description of Titan's interaction with the corotating magnetospheric plasma flow. For this reason, Titan's plasma environment has been studied by using a 3-D hybrid simulation code, treating the electrons as a massless, charge-neutralizing fluid, whereas a completely kinetic approach is used to cover ion dynamics. The calculations are performed on a curvilinear simulation grid which is adapted to the spherical geometry of the obstacle. In the model, Titan's dayside ionosphere is mainly generated by solar UV radiation; hence, the local ion production rate depends on the solar zenith angle. Because the Titan interaction features the possibility of having the densest ionosphere located on a face not aligned with the ram flow of the magnetospheric plasma, a variety of different scenarios can be studied. The simulations show the formation of a strong magnetic draping pattern and an extended pick-up region, being highly asymmetric with respect to the direction of the convective electric field. In general, the mechanism giving rise to these structures exhibits similarities to the interaction of the ionospheres of Mars and Venus with the supersonic solar wind. The simulation results are in agreement with data from recent Cassini flybys.

Aerosol chemistry in Titan's ionosphere: simultaneous growth and etching processes

Science.gov (United States)

Carrasco, Nathalie; Cernogora, Guy; Jomard, François; Etcheberry, Arnaud; Vigneron, Jackie

2016-10-01

Since the Cassini-CAPS measurements, organic aerosols are known to be present and formed at high altitudes in the diluted and partially ionized medium that is Titan's ionosphere [1]. This unexpected chemistry can be further investigated in the laboratory with plasma experiments simulating the complex ion-neutral chemistry starting from N2-CH4 [2]. Two sorts of solid organic samples can be produced in laboratory experiments simulating Titan's atmospheric reactivity: grains in the volume and thin films on the reactor walls. We expect that grains are more representative of Titan's atmospheric aerosols, but films are used to provide optical indices for radiative models of Titan's atmosphere.The aim of the present study is to address if these two sorts of analogues are chemically equivalent or not, when produced in the same N2-CH4 plasma discharge. The chemical compositions of both these materials are measured by using elemental analysis, XPS analysis and Secondary Ion Mass Spectrometry. We find that films are homogeneous but significantly less rich in nitrogen and hydrogen than grains produced in the same experimental conditions. This surprising difference in their chemical compositions is explained by the efficient etching occurring on the films, which stay in the discharge during the whole plasma duration, whereas the grains are ejected after a few minutes [3]. The impact for our understanding of Titan's aerosols chemical composition is important. Our study shows that chemical growth and etching process are simultaneously at stake in Titan's ionosphere. The more the aerosols stay in the ionosphere, the more graphitized they get through etching process. In order to infer Titan's aerosols composition, our work highlights a need for constraints on the residence time of aerosols in Titan's ionosphere. [1] Waite et al. (2009) Science , 316, p. 870[2] Szopa et al. (2006) PSS, 54, p. 394[3] Carrasco et al. (2016) PSS, 128, p. 52

Plasma environment of Titan: a 3-D hybrid simulation study

Directory of Open Access Journals (Sweden)

S. Simon

2006-05-01

Full Text Available Titan possesses a dense atmosphere, consisting mainly of molecular nitrogen. Titan's orbit is located within the Saturnian magnetosphere most of the time, where the corotating plasma flow is super-Alfvénic, yet subsonic and submagnetosonic. Since Titan does not possess a significant intrinsic magnetic field, the incident plasma interacts directly with the atmosphere and ionosphere. Due to the characteristic length scales of the interaction region being comparable to the ion gyroradii in the vicinity of Titan, magnetohydrodynamic models can only offer a rough description of Titan's interaction with the corotating magnetospheric plasma flow. For this reason, Titan's plasma environment has been studied by using a 3-D hybrid simulation code, treating the electrons as a massless, charge-neutralizing fluid, whereas a completely kinetic approach is used to cover ion dynamics. The calculations are performed on a curvilinear simulation grid which is adapted to the spherical geometry of the obstacle. In the model, Titan's dayside ionosphere is mainly generated by solar UV radiation; hence, the local ion production rate depends on the solar zenith angle. Because the Titan interaction features the possibility of having the densest ionosphere located on a face not aligned with the ram flow of the magnetospheric plasma, a variety of different scenarios can be studied. The simulations show the formation of a strong magnetic draping pattern and an extended pick-up region, being highly asymmetric with respect to the direction of the convective electric field. In general, the mechanism giving rise to these structures exhibits similarities to the interaction of the ionospheres of Mars and Venus with the supersonic solar wind. The simulation results are in agreement with data from recent Cassini flybys.

Effects of hydrothermal post-treatment on microstructures and morphology of titanate nanoribbons

International Nuclear Information System (INIS)

Yu Huogen; Yu Jiaguo; Cheng Bei; Zhou Minghua

2006-01-01

Titanate nanoribbons were prepared via a hydrothermal treatment of rutile-type TiO 2 powders in a 10 M NaOH solution at 200 deg. C for 48 h. The as-prepared titanate nanoribbons were then hydrothermally post-treated at 150 deg. C for 12-36 h. The titanate nanoribbons before and after hydrothermal post-treatment were characterized with FESEM, XRD, TEM, UV-VIS and nitrogen adsorption-desorption isotherms. The results showed that the hydrothermal post-treatment not only promoted the phase transformation from titanate to anatase TiO 2 , but also was beneficial to the removal of Na + ions remained in the titanate nanoribbons. After hydrothermal post-treatment, the TiO 2 samples retained the one-dimensional structure feature of the titanate nanoribbons and showed an obvious increase in the specific surface area and the pore volume

Use of titanates in decontamination of defense waste

International Nuclear Information System (INIS)

Dosch, R.G.

1978-06-01

Sodium titanate, an inorganic ion exchange material, has been evaluated for use in a process to remove strontium from Defense Waste or other high-sodium, caustic solutions. Distribution coefficients on the order of 10 5 were observed at sub part per million concentrations of Sr, and the effects of other cation impurities and complexants in the waste were investigated. The preparation and general chemical properties of the exchange material are discussed. This information was used in developing a commercial source which has since supplied a 200 kg batch of the material for evaluation. In column ion exchange experiments with 85 Sr-doped simulated waste, decontamination factors of 500 or greater were observed in the first 2000 to 3500 bed volumes of effluent, depending on the impurities in the simulant. A -40 to +130 mesh range of sodium titanate powder was used as the baseline material, but a study to produce alternate forms of the titanate was carried in parallel. This has resulted in two materials which appear promising with respect to both simplification of handling and chemical properties. One of the materials is an agglomerated form of the titanate formed by extrusion pelletizing using water as a binder, and the second is a macroreticular organic anion resin which was loaded with 30 to 40% (by weight) of sodium titanate. The results of initial testing of these materials are discussed

Multi-wavelength search for complex molecules in Titan's Atmosphere

Science.gov (United States)

Nixon, C. A.; Cordiner, M. A.; Greathouse, T. K.; Richter, M.; Kisiel, Z.; Irwin, P. G.; Teanby, N. A.; Kuan, Y. J.; Charnley, S. B.

2017-12-01

Titan's atmosphere is one of the most complex astrochemical environments known: the photochemistry of methane and nitrogen, induced by solar UV and Saturn magnetospheric electron impacts, creates a bonanza of organic molecules like no other place in the solar system. Cassini has unveiled the first glimpses of Titan's chemical wonderland, but many gaps remain. In particular, interpreting the mass spectra of Titan's upper atmosphere requires external knowledge, to disentangle the signature of molecules from their identical-mass brethren. Cassini infrared spectroscopy with CIRS has helped to some extent, but is also limited by low spectral resolution. Potentially to the rescue, comes high-resolution spectroscopy from the Earth at infrared and sub-millimeter wavelengths, where molecules exhibit vibrational and rotational transitions respectively. In this presentation, we describe the quest to make new, unique identifications of large molecules in Titan's atmosphere, focusing specifically on cyclic molecules including N-heterocycles. This molecular family is of high astrobiological significance, forming the basic ring structure for DNA nucleobases. We present the latest spectroscopic observations of Titan from ALMA and NASA's IRTF telescope, discussing present findings and directions for future work.

Calorimetric measurements on hafnium titanate

International Nuclear Information System (INIS)

Kandan, R.; Prabhakara Reddy, B.; Panneerselvam, G.; Nagarajan, K.

2012-01-01

Owing to its desirable nuclear and mechanical properties such as good absorption cross-section for thermal neutrons (105 barns), hafnium titanate (HfTiO 4 ) finds application as control rods for nuclear reactors. An accurate knowledge of the thermo physical properties of this material is necessary for design of control rod and for modeling its performance. Heat capacity is an important thermodynamic property that determines the temperature dependent variation of all other thermodynamic properties. Hence enthalpy increments of hafnium titanate (HfTiO 4 ) were measured in the temperature range 803-1663 K by employing the method of inverse drop calorimetry using high temperature differential calorimeter

Antibacterial Properties of Titanate Nano fiber Thin Films Formed on a Titanium Plate

International Nuclear Information System (INIS)

Yada, M.; Inoue, Y.; Morita, T.; Torikai, T.; Watari, T.; Noda, I.; Hotokebuchi, T.

2013-01-01

A sodium titanate nano fiber thin film and a silver nanoparticle/silver titanate nano fiber thin film formed on the surface of a titanium plate exhibited strong antibacterial activities against methicillin-resistant Staphylococcus aureus, which is one of the major bacteria causing in-hospital infections. Exposure of the sodium titanate nano fiber thin film to ultraviolet rays generated a high antibacterial activity due to photo catalysis and the sodium titanate nano fiber thin film immediately after its synthesis possessed a high antibacterial activity even without exposure to ultraviolet rays. Elution of silver from the silver nanoparticle/silver titanate nano fiber thin film caused by the silver ion exchange reaction was considered to contribute substantially to the strong antibacterial activity. The titanate nano fiber thin films adhered firmly to titanium. Therefore, these titanate nano fiber thin film/titanium composites will be extremely useful as implant materials that have excellent antibacterial activities.

Acetylene on Titan

Science.gov (United States)

Singh, Sandeep; McCord, Thomas B.; Combe, Jean-Philippe; Rodriguez, Sebastien; Cornet, Thomas; Le Mouélic, Stéphane; Clark, Roger Nelson; Maltagliati, Luca; Chevrier, Vincent

2016-10-01

Saturn's moon Titan possesses a thick atmosphere that is mainly composed of N2 (98%), CH4 (2 % overall, but 4.9% close to the surface) and less than 1% of minor species, mostly hydrocarbons [1]. A dissociation of N2 and CH4 forms complex hydrocarbons in the atmsophere and acetylene (C2H2) and ethane (C2H6) are produced most abundently. Since years, C2H2 has been speculated to exist on the surface of Titan based on its high production rate in the stratosphere predicted by photochemical models [2,3] and from its detection as trace gas sublimated/evaporated from the surface after the landing of the Huygens probe by the Gas Chromatograph Mass Spectrometer (GCMS) [1]. Here we show evidence of acetylene (C2H2) on the surface of Titan by detecting absorption bands at 1.55 µm and 4.93 µm using Cassini Visual and Infrared Mapping Spectrometer (VIMS) [4] at equatorial areas of eastern Shangri-La, and Fensal-Aztlan/Quivira.An anti-correlation of absorption band strength with albedo indicates greater concentrations of C2H2 in the dark terrains, such as sand dunes and near the Huygens landing site. The specific location of the C2H2 detections suggests that C2H2 is mobilized by surface processes, such as surface weathering by liquids through dissolution/evaporation processes.References:[1]Niemann et al., Nature 438, 779-784 (2005).[2]Lavvas et al., Planetary and Space Science 56, 67 - 99 (2008).[3]Lavvas et al., Planetary and Space Science 56, 27 - 66 (2008).[4] Brown et al., The Cassini-Huygens Mission 111-168 (Springer, 2004).

Epoxy elastomers reinforced with functionalized multi-walled carbon nanotubes as stimuli-responsive shape memory materials

International Nuclear Information System (INIS)

Lama, G. C.; Nasti, G.; Cerruti, P.; Gentile, G.; Carfagna, C.; Ambrogi, V.

2014-01-01

In this work, the incorporation of multiwalled carbon nanotubes (MWCNT) into epoxy-based elastomers was carried out in order to obtain nanocomposite systems with shape memory effect. For the preparation of elastomeric matrices, p-bis(2,3-epoxypropoxy)-α-methylstilbene (DOMS) was cured with sebacic acid. DOMS was synthesized in our laboratory and it is characterized by a rigid-rod, potentially liquid crystalline structure. A lightly cross-linked liquid crystalline elastomer was obtained. As for nanocomposites, variable amounts (0.75, 1.50, 3.0, 6.0, 12.0 wt.%) of COOH-MWCNTs were employed. In order to improve the nanotubes dispersibility and the interfacial adhesion with the epoxy matrix, an optimized two-step procedure was developed, which consisted in grafting the epoxy monomer onto the nanotube surface and then curing it in presence of crosslinking agent. DOMS-functionalized MWCNT were characterized through solvent dispersion experiments, FTIR spectroscopy and TGA analysis, which demonstrated the occurred covalent functionalization of the nanotubes with the epoxy monomers. The morphological analysis through electron microscopy demonstrated that this was an efficient strategy to improve the dispersion of nanotubes within the matrix. The second part of the work was devoted to the structural, thermal, mechanical and electric characterization of elastomeric nanocomposites. The results indicated a general improvement of properties of nanocomposites. Also, independently of the nanotube content, a smectic phase formed. Shape memory features of LC systems were also evaluated. It was demonstrated the shape could be recovered through heating, solvent immersion, as well as upon the application of an electrical field

Activation and waste disposal of the TITAN RFP [reversed-field-pinch] reactors

International Nuclear Information System (INIS)

Cheng, E.T.; Conn, R.W.

1988-01-01

The TITAN-I lithium self-cooled and TITAN-II aqueous lithium nitrate solution-cooled fusion reactors are based on the reversed-field-pinch (RFP) toroidal confinement concept and operate at high power density with an 18.1 MW/m 2 neutron wall loading. These designs were analyzed to study the activation and waste disposal aspects of such high-power density reactors. It was found that because of the use of V-3Ti-1Si (TITAN-I) and reduced activation ferritic steel (TITAN-II) as structural alloys for the first wall, blanket, reflector, and shield components, all the TITAN components except the divertor collector plates can be classified as shallow-land burial (10CFR61 Class C or better) nuclear waste for disposal, provided that the impurity elements, niobium and molybdenum, can be controlled below about 1 and 0.3 appm levels, respectively. The average annual disposal masses were estimated to be 150 and 96 tonnes, respectively, for the 1,000 MW TITAN-I and TITAN-II reactors. This corresponds to about 11% of the total mass in the fusion power core of both reactors. The divertor collector plates are fabricated with tungsten because of its low particle sputtering properties. These divertor collector plates in the TITAN-I reactor will be qualified as Class C waste after 18.1 MW-y/m 2 operation. The waste disposal rating of the divertor collector plates in the TITAN-II reactor, however, is estimated to be a factor of 4 higher than allowed for Class C disposal, because of the soft neutron spectrum in the beryllium environment. The annual disposal mass of this non-Class C waste is 0.35 tons, about 0.04% of the average annual discharge mass for the TITAN-II reactor. An additional 74 m 3 annual discharge of Class C waste containing 14 C may be needed for the TITAN-II reactor because of the use of nitrate salt in the aqueous coolant as the tritium breeder. 13 refs., 6 tabs

Skin graft

Science.gov (United States)

Skin transplant; Skin autografting; FTSG; STSG; Split thickness skin graft; Full thickness skin graft ... donor site. Most people who are having a skin graft have a split-thickness skin graft. This takes ...

Production and global transport of Titan's sand particles

Science.gov (United States)

Barnes, Jason W.; Lorenz, Ralph D.; Radebaugh, Jani; Hayes, Alexander G.; Arnold, Karl; Chandler, Clayton

2015-06-01

Previous authors have suggested that Titan's individual sand particles form by either sintering or by lithification and erosion. We suggest two new mechanisms for the production of Titan's organic sand particles that would occur within bodies of liquid: flocculation and evaporitic precipitation. Such production mechanisms would suggest discrete sand sources in dry lakebeds. We search for such sources, but find no convincing candidates with the present Cassini Visual and Infrared Mapping Spectrometer coverage. As a result we propose that Titan's equatorial dunes may represent a single, global sand sea with west-to-east transport providing sources and sinks for sand in each interconnected basin. The sand might then be transported around Xanadu by fast-moving Barchan dune chains and/or fluvial transport in transient riverbeds. A river at the Xanadu/Shangri-La border could explain the sharp edge of the sand sea there, much like the Kuiseb River stops the Namib Sand Sea in southwest Africa on Earth. Future missions could use the composition of Titan's sands to constrain the global hydrocarbon cycle.

Exploring inner structure of Titan's dunes from Cassini Radar observations

Science.gov (United States)

Sharma, P.; Heggy, E.; Farr, T. G.

2013-12-01

Linear dunes discovered in the equatorial regions of Titan by the Cassini-Huygens mission are morphologically very similar to many terrestrial linear dune fields. These features have been compared with terrestrial longitudinal dune fields like the ones in Namib desert in western Africa. This comparison is based on the overall parallel orientation of Titan's dunes to the predominant wind direction on Titan, their superposition on other geomorphological features and the way they wrap around topographic obstacles. Studying the internal layering of dunes has strong implications in understanding the hypothesis for their origin and evolution. In Titan's case, although the morphology of the dunes has been studied from Cassini Synthetic Aperture Radar (SAR) images, it has not been possible to investigate their internal structure in detail as of yet. Since no radar sounding data is available for studying Titan's subsurface yet, we have developed another technique to examine the inner layering of the dunes. In this study, we utilize multiple complementary radar datasets, including radar imaging data for Titan's and Earth's dunes and Ground Penetrating Radar (GPR)/radar sounding data for terrestrial dunes. Based on dielectric mixing models, we suggest that the Cassini Ku-band microwaves should be able to penetrate up to ~ 3 m through Titan's dunes, indicating that the returned radar backscatter signal would include contributions from both surface and shallow subsurface echoes. This implies that the shallow subsurface properties can be retrieved from the observed radar backscatter (σ0). In our analysis, the variation of the radar backscatter as a function of dune height is used to provide an insight into the layering in Titan's dunes. We compare the variation of radar backscatter with elevation over individual dunes on Titan and analogous terrestrial dunes in three sites (Great Sand Sea, Siwa dunes and Qattaniya dunes) in the Egyptian Sahara. We observe a strong, positive

Evolution of skin grafting for treatment of burns: Reverdin pinch grafting to Tanner mesh grafting and beyond.

Science.gov (United States)

Singh, Mansher; Nuutila, Kristo; Collins, K C; Huang, Anne

2017-09-01

Skin grafting is the current standard care in the treatment of full thickness burns. It was first described around 1500 BC but the vast majority of advancements have been achieved over the past 200 years. An extensive literature review was conducted on Pubmed, Medline and Google Scholar researching the evolution of skin grafting techniques. The authors concentrated on the major landmarks of skin grafting and also provide an overview of ongoing research efforts in this field. The major innovations of skin grafting include Reverdin pinch grafting, Ollier grafting, Thiersch grafting, Wolfe grafting, Padgett dermatome and modifications, Meek-wall microdermatome and Tanner mesh grafting. A brief description of the usage, advantages and limitations of each technique is included in the manuscript. Skin grafting technique have evolved significantly over past 200 years from Reverdin pinch grafting to modern day meshed skin grafts using powered dermatome. Increasing the expansion ratio and improving the cosmetic and functional outcome are the main focus of ongoing skin grafting research and emerging techniques (such as Integra ® , Recell ® , Xpansion ® ) are showing promise. Copyright © 2017 Elsevier Ltd and ISBI. All rights reserved.

ATOMIC CARBON IN THE UPPER ATMOSPHERE OF TITAN

International Nuclear Information System (INIS)

Zhang, X.; Yung, Y. L.; Ajello, J. M.

2010-01-01

The atomic carbon emission C I line feature at 1657 A ( 3 P 0 J - 3 P J ) in the upper atmosphere of Titan is first identified from the airglow spectra obtained by the Cassini Ultra-violet Imaging Spectrograph. A one-dimensional photochemical model of Titan is used to study the photochemistry of atomic carbon on Titan. Reaction between CH and atomic hydrogen is the major source of atomic carbon, and reactions with hydrocarbons (C 2 H 2 and C 2 H 4 ) are the most important loss processes. Resonance scattering of sunlight by atomic carbon is the dominant emission mechanism. The emission intensity calculations based on model results show good agreement with the observations.

Titan's icy scar

Science.gov (United States)

Griffith, C. A.; Penteado, P. F.; Turner, J. D.; Neish, C. D.; Mitri, G.; Montiel, M. J.; Schoenfeld, A.; Lopes, R. M. C.

2017-09-01

We conduct a Principal Components Analysis (PCA) of Cassini/VIMS [1] infrared spectral windows to identify and quantify weak surface features, with no assumptions on the haze and surface characteris- tics. This study maps the organic sediments, supplied by past atmospheres, as well as ice-rich regions that constitute Titan's bedrock.

Ion Irradiation Damage in Zirconate and Titanate Ceramics for Pu Disposition

International Nuclear Information System (INIS)

Stewart, Martin W.; Begg, Bruce D.; Finnie, K.; Colella, Michael; Li, H.; McLeod, Terry; Smith, Katherine L.; Zhang, Zhaoming; Weber, William J.; Thevuthasan, Suntharampillai

2004-01-01

In this paper, we discuss the effect of ion irradiation on pyrochlore-rich titanate and defect-fluorite zirconate ceramics designed for plutonium immobilization. Samples, with Ce as an analogue for Pu, were made via oxide routes and consolidated by cold-pressing and sintering. Ion irradiation damage was carried out with 2 MeV Au2+ ions to a fluence of 5 ions nm-2 in the accelerator facilities within the Environmental Molecular Sciences Laboratory at Pacific Northwest National Laboratory. Irradiated and non-irradiated samples were examined by x-ray diffraction, scanning and transmission electron microscopy, x-ray photoelectron and infrared spectroscopy, and spectroscopic ellipsometry. Samples underwent accelerated leach testing at pH 1.75 (nitric acid) at 90 C for 28 days. The zirconate samples were more ion-irradiation damage resistant than the titanate samples, showing little change after ion-irradiation whereas the titanate samples formed an amorphous surface layer ∼ 500 nm thick. While all samples had high aqueous durability, the titanate leach rate was ∼ 5 times that of the zirconate. The ion-irradiation increased the leach rate of the titanate without impurities by ∼ 5 times. The difference in the leach rates between irradiated and unirradiated zirconate samples is small. However, the zirconates were less able to incorporate impurities than the titanate ceramics and required higher sintering temperatures, ∼ 1500 C compared to 1350 C for the titanates.

Description of tritium release from lithium titanate at constant temperature

Energy Technology Data Exchange (ETDEWEB)

Pena, L; Lagos, S; Jimenez, J; Saravia, E [Comision Chilena de Energia Nuclear, Santiago (Chile)

1998-03-01

Lithium Titanate Ceramics have been prepared by the solid-state route, pebbles and pellets were fabricated by extrusion and their microstructure was characterized in our laboratories. The ceramic material was irradiated in the La Reina Reactor, RECH-1. A study of post-irradiation annealing test, was performed measuring Tritium release from the Lithium Titanate at constant temperature. The Bertone`s method modified by R. Verrall is used to determine the parameters of Tritium release from Lithium Titanate. (author)

Titan's cold case files - Outstanding questions after Cassini-Huygens

Science.gov (United States)

Nixon, C. A.; Lorenz, R. D.; Achterberg, R. K.; Buch, A.; Coll, P.; Clark, R. N.; Courtin, R.; Hayes, A.; Iess, L.; Johnson, R. E.; Lopes, R. M. C.; Mastrogiuseppe, M.; Mandt, K.; Mitchell, D. G.; Raulin, F.; Rymer, A. M.; Todd Smith, H.; Solomonidou, A.; Sotin, C.; Strobel, D.; Turtle, E. P.; Vuitton, V.; West, R. A.; Yelle, R. V.

2018-06-01

The entry of the Cassini-Huygens spacecraft into orbit around Saturn in July 2004 marked the start of a golden era in the exploration of Titan, Saturn's giant moon. During the Prime Mission (2004-2008), ground-breaking discoveries were made by the Cassini orbiter including the equatorial dune fields (flyby T3, 2005), northern lakes and seas (T16, 2006), and the large positive and negative ions (T16 & T18, 2006), to name a few. In 2005 the Huygens probe descended through Titan's atmosphere, taking the first close-up pictures of the surface, including large networks of dendritic channels leading to a dried-up seabed, and also obtaining detailed profiles of temperature and gas composition during the atmospheric descent. The discoveries continued through the Equinox Mission (2008-2010) and Solstice Mission (2010-2017) totaling 127 targeted flybys of Titan in all. Now at the end of the mission, we are able to look back on the high-level scientific questions from the start of the mission, and assess the progress that has been made towards answering these. At the same time, new scientific questions regarding Titan have emerged from the discoveries that have been made. In this paper we review a cross-section of important scientific questions that remain partially or completely unanswered, ranging from Titan's deep interior to the exosphere. Our intention is to help formulate the science goals for the next generation of planetary missions to Titan, and to stimulate new experimental, observational and theoretical investigations in the interim.

Latitudinal and altitudinal controls of Titan's dune field morphometry

Science.gov (United States)

Le Gall, A.; Hayes, A. G.; Ewing, R.; Janssen, M. A.; Radebaugh, J.; Savage, C.; Encrenaz, P.; the Cassini Radar Team

2012-01-01

Dune fields dominate ˜13% of Titan's surface and represent an important sink of carbon in the methane cycle. Herein, we discuss correlations in dune morphometry with altitude and latitude. These correlations, which have important implications in terms of geological processes and climate on Titan, are investigated through the microwave electromagnetic signatures of dune fields using Cassini radar and radiometry observations. The backscatter and emissivity from Titan's dune terrains are primarily controlled by the amount of interdune area within the radar footprint and are also expected to vary with the degree of the interdunal sand cover. Using SAR-derived topography, we find that Titan's main dune fields (Shangri-La, Fensal, Belet and Aztlan) tend to occupy the lowest elevation areas in Equatorial regions occurring at mean elevations between ˜-400 and ˜0 m (relative to the geoid). In elevated dune terrains, we show a definite trend towards a smaller dune to interdune ratio and possibly a thinner sand cover in the interdune areas. A similar correlation is observed with latitude, suggesting that the quantity of windblown sand in the dune fields tends to decrease as one moves farther north. The altitudinal trend among Titan's sand seas is consistent with the idea that sediment source zones most probably occur in lowlands, which would reduce the sand supply toward elevated regions. The latitudinal preference could result from a gradual increase in dampness with latitude due to the asymmetric seasonal forcing associated with Titan's current orbital configuration unless it is indicative of a latitudinal preference in the sand source distribution or wind transport capacity.

ALMA observations of Titan's atmospheric chemistry and seasonal variation

Science.gov (United States)

Cordiner, Martin

2017-04-01

Titan is the largest moon of Saturn, with a thick (1.45 bar) atmosphere composed primarily of molecular nitrogen and methane. Photochemistry in Titan's upper atmosphere results in the production of a wide range of organic molecules, including hydrocarbons, nitriles and aromatics, some of which could be of pre-biotic relevance. Thus, we obtain insights into the possible molecular inventories of primitive (reducing) planetary atmospheres. Titan's atmosphere also provides a unique laboratory for testing our understanding of fundamental processes involving the chemistry and spectroscopy of complex organic molecules. In this talk, results will be presented from our studies using the Atacama Large Millimeter/submillimeter Array (ALMA) during the period 2012-2015, focussing in particular on the detection and mapping of emission from various nitrile species. By combining data from multiple ALMA observations, our spectra have reached an unprecedented sensitivity level, enabling the first spectroscopic detection and mapping of C2H3CN (vinyl cyanide) on Titan. Liquid-phase simulations of Titan's seas indicate that vinyl cyanide molecules could combine to form vesicle membranes (similar to the cells of terrestrial biology), and the astrobiological implications of this discovery will be discussed. Furthermore, ALMA observations provide instantaneous snapshot mapping of Titan's entire Earth-facing hemisphere, for gases inaccessible to previous instruments. Combined with complementary data obtained from the Cassini Saturn orbiter, as well as theoretical models and laboratory studies, our observed, seasonally variable, spatially resolved abundance patterns are capable of providing new insights into photochemical production and transport in primitive planetary atmospheres in the Solar System and beyond.

Covalent Surface Functionalization of Boron Nitride Nanotubes Fabricated with Diazonium Salt

Directory of Open Access Journals (Sweden)

Zhujun Wang

2018-01-01

Full Text Available The chemical inertness and poor wetting properties of boron nitride nanotubes (BNNTs hindered their applications. In this work, BNNTs have been functionalized with aniline groups by reacting with diazonium salt and the graft content of aniline component was calculated as high as 71.4 wt.%. The chemical structure, composition, and morphology of functionalized BNNTs were carefully characterized to illustrate the modification. The anilinocarbocation generated by decomposition of diazonium salt reacted not only with NH2 sites, but also with B-OH sites on the surface of BNNTs. Meanwhile, the reaction applied a hot strong acid environment, which would help to open parts of B-N bonds to produce more reactive sites and enrich the functional groups grafted on the surface of BNNTs. Consequently, the functionalized BNNTs exhibited significantly improved dispersion stability in chloroform compared with pristine BNNTs. Amino surface functionalization of BNNTs offered more possibilities for surface chemical design of boron nitride and its practical application.

Crater topography on Titan: Implications for landscape evolution

Science.gov (United States)

Neish, C.; Kirk, R.; Lorenz, R.; Bray, V.; Schenk, P.; Stiles, B.; Turtle, E.; Cassini Radar Team

2012-04-01

Unique among the icy satellites, Titan’s surface shows evidence for extensive modification by fluvial and aeolian erosion, which act to change the topography of its surface over time. Quantifying the extent of this landscape evolution is difficult, since the original, ‘non-eroded’ surface topography is generally unknown. However, fresh craters on icy satellites have a well-known shape and morphology, which has been determined from extensive studies on the airless worlds of the outer solar system (Schenk et al., 2004). By comparing the topography of craters on Titan to similarly sized, pristine analogues on airless bodies, we can obtain one of the few direct measures of the amount of erosion that has occurred on Titan. Cassini RADAR has imaged >30% of the surface of Titan, and more than 60 potential craters have been identified in this data set (Wood et al., 2010; Neish and Lorenz, 2012). Topographic information for these craters can be obtained from a technique known as ‘SARTopo’, which estimates surface heights by comparing the calibration of overlapping synthetic aperture radar (SAR) beams (Stiles et al., 2009). We present topography data for several craters on Titan, and compare the data to similarly sized craters on Ganymede, for which topography has been extracted from stereo-derived digital elevation models (Bray et al., 2012). We find that the depths of craters on Titan are generally within the range of depths observed on Ganymede, but several hundreds of meters shallower than the average (Fig. 1). A statistical comparison between the two data sets suggests that it is extremely unlikely that Titan’s craters were selected from the depth distribution of fresh craters on Ganymede, and that is it much more probable that the relative depths of Titan are uniformly distributed between ‘fresh’ and ‘completely infilled’. This is consistent with an infilling process that varies linearly with time, such as aeolian infilling. Figure 1: Depth of

Graft intolerance syndrome requiring graft nephrectomy after late kidney graft failure: can it be predicted? A retrospective cohort study.

Science.gov (United States)

Bunthof, Kim L W; Verhoeks, Carmen M; van den Brand, Jan A J G; Hilbrands, Luuk B

2018-02-01

Graft nephrectomy is recommended in case of early graft failure. When the graft fails more than 3-6 months after transplantation, it is current practice to follow a wait-and-see policy. A common indication for graft removal is the graft intolerance syndrome. We aimed to create a risk prediction model for the occurrence of graft intolerance resulting in graft nephrectomy. We collected data of kidney transplantations performed in our center between 1980 and 2010 that failed at least 6 months after transplantation. We evaluated the association between baseline characteristics and the occurrence of graft nephrectomy because of graft intolerance using a competing risk regression model. Prognostic factors were included in a multivariate prediction model. In- and exclusion criteria were met in 288 cases. In 48 patients, the graft was removed because of graft intolerance. Donor age, the number of rejections, and shorter graft survival were predictive factors for graft nephrectomy because of the graft intolerance syndrome. These factors were included in a prediction rule. Using donor age, graft survival, and the number of rejections, clinicians can predict the need for graft nephrectomy with a reasonable accuracy. © 2017 Steunstichting ESOT.

Investigation on corrosion resistance of metal superficially modified with alkoxy titanates

International Nuclear Information System (INIS)

Yao Kangde; Song Shizhe; Shen Ningxiang

1991-01-01

A study has been made in order to determine corrosion protection performance of alkoxy titanate modified iron in a 3% NaCl solution. The effectiveness of alkoxy titanates as corrosion retarders for chloride environments is confirmed by both stepped potential sweep technique and electrochemical impedance spectroscopy (EIS). Ion microanalysis (IMA) depth profiles are used to elucidate the corrosion inhibitive action of different alkoxy titanate. (orig.)

A Direct Simulation Monte Carlo Model Of Thermal Escape From Titan

Science.gov (United States)

Johnson, Robert E.; Tucker, O. J.

2008-09-01

Recent analysis of density profiles vs. altitude from the Ion Neutral Mass Spectrometer (INMS) on Cassini (Waite et al. 2005) suggest Titan could have loss a significant amount of atmosphere in 4 Gyr at present escape rates (e.g., Johnson 2008). Strobel 2008 applied a slow hydrodynamic escape model to Titan's atmosphere using solar heating below the exobase to drive upward thermal conduction and power escape. However, near the exobase continuum models become problematic as a result of the increasing rarefaction in the atmosphere. The microscopic nature of DSMC is directly suitable to model atmosphere flow in nominal exobase region (e.g., Michael et. al. 2005). Our Preliminary DSMC models have shown no evidence for slow hydrodynamic escape of N2 and CH4 from Titan's atmosphere using boundary conditions normalized to the atmospheric properties in Strobel (2008). In this paper we use a 1D radial Direct Simulation Monte Carlo (DSMC) model of heating in Titan's upper atmosphere to estimate the escape rate as a function of the Jean's parameter. In this way we can test under what conditions the suggested deviations from Jeans escape would occur. In addition, we will be able to extract the necessary energy deposition to power the heavy molecule loss rates suggested in recent models (Strobel 2008; Yelle et. al. 2008). Michael, M. Johnson, R.E. 2005 Energy Deposition of pickup ions and heating of Titan's atmosphere. Planat. Sp. Sci. 53, 1510-1514 Johnson, R.E., "Sputtering and Heating of Titan's Upper Atmosphere", Proc Royal Soc. (London) (2008) Strobel, D.F. 2008 Titan's hydrodynamically escaping atmosphere. Icarus 193, 588-594 Yelle, R.V., J. Cui and I. C.F. Muller-Wodarg 2008 Methane Escape from Titan's Atmosphere. J. Geophys. Res in press Waite, J.H., Jr., Niemann, H.B., Yelle, R.V. et al. 2005 Ion Neutral Mass Spectrometer Results from the First Flyby of Titan. Science 308, 982-986

Effect of RGD Peptide-Coated TiO2 Nanotubes on the Attachment, Proliferation, and Functionality of Bone-Related Cells

Directory of Open Access Journals (Sweden)

Seunghan Oh

2013-01-01

Full Text Available The purpose of this research was to characterize an Arg-Gly-Asp (RGD peptide immobilized on TiO2 nanotubes. In addition, we investigated the effects of the RGD peptide-coated TiO2 nanotubes on the cellular response, proliferation, and functionality of osteogenic-induced human mesenchymal stem cells (hMSCs, which are osteoclasts that have been induced by bone marrow macrophages. The RGD peptide was grafted covalently onto the surface of TiO2 nanotubes based on the results of SEM, FT-IR, and XPS. Furthermore, the RGD peptide promoted the initial attachment and proliferation of the hMSCs, regardless of the size of the TiO2 nanotubes. However, the RGD peptide did not prominently affect the osteogenic functionality of the hMSCs because the peptide suppressed hMSC motility associated with osteogenic differentiation. The result of an in vitro osteoclast test showed that the RGD peptide accelerated the initial attachment of preosteoclasts and the formation of mature osteoclasts, which could resorb the bone matrix. Therefore, we believe that an RGD coating on TiO2 nanotubes synthesized on Ti implants might not offer significant acceleration of bone formation in vivo because osteoblasts and osteoclasts reside in the same compartment.

3D scaffolds from vertically aligned carbon nanotubes/poly(methyl methacrylate) composites via atom transfer radical polymerization

Energy Technology Data Exchange (ETDEWEB)

Tebikachew, Behabtu; Magina, Sandra [CICECO, Department of Chemistry, University of Aveiro (Portugal); Mata, Diogo; Oliveira, Filipe J.; Silva, Rui F. [CICECO, Department of Materials and Ceramic Engineering, University of Aveiro (Portugal); Barros-Timmons, Ana, E-mail: anabarros@ua.pt [CICECO, Department of Chemistry, University of Aveiro (Portugal)

2015-01-15

Vertically aligned carbon nanotubes (VACNTs) synthesized by Thermal Chemical Vapour Deposition (TCVD) were modified using an Ar:O{sub 2} (97:3) plasma to generate oxygen-containing functional groups on the surface for subsequent modification. X-ray photo-emission spectroscopy (XPS) and micro-Raman analyses confirmed the grafting of those functional groups onto the surface of the nanotubes as well as the removal of amorphous carbon produced and deposited on the VACNT forests during the CVD process. The plasma treated VACNT forests were further modified with 2-bromo-2-methylpropionyl bromide, an atom transfer radical polymerization (ATRP) initiator, to grow poly(methyl methacrylate) (PMMA) chains from the forests via ATRP. Scanning transmission electron microscopy (STEM) of the ensuing VACNT/PMMA composites confirmed the coating of the nanotube forests with the PMMA polymer. 3D scaffolds of polymeric composites with honeycomb like structure were then obtained. Compressive tests have shown that the VACNT/PMMA composite has higher compressive strength than the pristine forest. - Highlights: • Vertically aligned carbon nanotubes (VACNTs) were synthesized and plasma modified. • X-ray photo-emission and Raman spectroscopies confirmed the VACNTs modification. • Poly(methyl methacrylate) chains were grown via ATRP from the VACNTs. • STEM of the VACNT/PMMA composites confirmed that PMMA surrounds the nanotubes. • VACNT/PMMA composite has higher compressive strength compared to the pristine forest.

3D scaffolds from vertically aligned carbon nanotubes/poly(methyl methacrylate) composites via atom transfer radical polymerization

International Nuclear Information System (INIS)

Tebikachew, Behabtu; Magina, Sandra; Mata, Diogo; Oliveira, Filipe J.; Silva, Rui F.; Barros-Timmons, Ana

2015-01-01

Vertically aligned carbon nanotubes (VACNTs) synthesized by Thermal Chemical Vapour Deposition (TCVD) were modified using an Ar:O 2 (97:3) plasma to generate oxygen-containing functional groups on the surface for subsequent modification. X-ray photo-emission spectroscopy (XPS) and micro-Raman analyses confirmed the grafting of those functional groups onto the surface of the nanotubes as well as the removal of amorphous carbon produced and deposited on the VACNT forests during the CVD process. The plasma treated VACNT forests were further modified with 2-bromo-2-methylpropionyl bromide, an atom transfer radical polymerization (ATRP) initiator, to grow poly(methyl methacrylate) (PMMA) chains from the forests via ATRP. Scanning transmission electron microscopy (STEM) of the ensuing VACNT/PMMA composites confirmed the coating of the nanotube forests with the PMMA polymer. 3D scaffolds of polymeric composites with honeycomb like structure were then obtained. Compressive tests have shown that the VACNT/PMMA composite has higher compressive strength than the pristine forest. - Highlights: • Vertically aligned carbon nanotubes (VACNTs) were synthesized and plasma modified. • X-ray photo-emission and Raman spectroscopies confirmed the VACNTs modification. • Poly(methyl methacrylate) chains were grown via ATRP from the VACNTs. • STEM of the VACNT/PMMA composites confirmed that PMMA surrounds the nanotubes. • VACNT/PMMA composite has higher compressive strength compared to the pristine forest

Decorating Mg/Fe oxide nanotubes with nitrogen-doped carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Cao Yong, E-mail: caoyangel@126.com [Institute of Environment and Municipal Engineering, North China Institute of Water Conservancy and Hydroelectric Power, Zhengzhou 450011 (China); Jiao Qingze, E-mail: jiaoqz@bit.edu.cn [School of Chemical Engineering and the Environment, Beijing Institute of Technology, Beijing 100081 (China); Zhao Yun [School of Chemical Engineering and the Environment, Beijing Institute of Technology, Beijing 100081 (China); Dong Yingchao [Materials and Surface Science Institute (MSSI), University of Limerick, Limerick (Ireland)

2011-09-22

Graphical abstract: Highlights: > Mg/Fe oxide nanotubes arrayed parallel to each other were prepared by an AAO template method. > The Mg/Fe oxide nanotubes decorated with CN{sub x} were realized by CVD of ethylenediamine on the outer surface of oxide nanotubes. > The magnetic properties of Mg/Fe oxide nanotubes were highly improved after being decorated. - Abstract: Mg/Fe oxide nanotubes decorated with nitrogen-doped carbon nanotubes (CN{sub x}) were fabricated by catalytic chemical vapor deposition of ethylenediamine on the outer surface of oxide nanotubes. Mg/Fe oxide nanotubes were prepared using a 3:1 molar precursor solution of Mg(NO{sub 3}){sub 2} and Fe(NO{sub 3}){sub 3} and anodic aluminum oxide as the substrate. The obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). The XRD pattern shows that the oxide nanotubes are made up of MgO and Fe{sub 2}O{sub 3}. TEM and SEM observations indicate the oxide nanotubes are arrayed roughly parallel to each other, and the outer surface of oxide nanotubes are decorated with CN{sub x}. XPS results show the nitrogen-doped level in CN{sub x} is about 7.3 at.%. Magnetic measurements with VSM demonstrate the saturated magnetization, remanence and coercivity of oxide nanotubes are obvious improved after being decorated with CN{sub x}.

Cassini/CIRS Observations of Water Vapor in Titan's Stratosphere

Science.gov (United States)

Bjoraker, Gordon L.; Achterberg, R. K.; Anderson, C. M.; Samuelson, R. E.; Carlson, R. C.; Jennings, D. E.

2008-01-01

The Composite Infrared Spectrometer (CIRS) on the Cassini spacecraft has obtained spectra of Titan during most of the 44 flybys of the Cassini prime mission. Water vapor on Titan was first detected using whole-disk observations from the Infrared Space Observatory (Coustenis et al 1998, Astron. Astrophys. 336, L85-L89). CIRS data permlt the retrieval of the latitudinal variation of water on Titan and some limited information on its vertical profile. Emission lines of H2O on Titan are very weak in the CIRS data. Thus, large spectral averages as well as improvements in calibration are necessary to detect water vapor. Water abundances were retrieved in nadir spectra at 55 South, the Equator, and at 19 North. Limb spectra of the Equator were also modeled to constrain the vertical distribution of water. Stratospheric temperatures in the 0.5 - 4.0 mbar range were obtained by inverting spectra of CH4 in the v4 band centered at 1304/cm. The temperature in the lower stratosphere (4 - 20 mbar) was derived from fitting pure rotation lines of CH4 between 80 and 160/cm. The origin of H2O and CO2 is believed to be from the ablation of micrometeorites containing water ice, followed by photochemistry. This external source of water originates either within the Saturn system or from the interplanetary medium. Recently, Horst et al (J. Geophys. Res. 2008, in press) developed a photochemical model of Titan in which there are two external sources of oxygen. Oxygen ions (probably from Enceladus) precipitate into Titan's atmosphere to form CO at very high altitudes (1100 km). Water ice ablation at lower altitudes (700 km) forms H2O and subsequent chemistry produces CO2. CIRS measurements of CO, CO2, and now of H2O will provide valuable constraints to these photochemical models and - improve our understanding of oxygen chemistry on Titan.

Stability and catalytic performance of vanadia supported on nanostructured titania catalyst in oxidative dehydrogenation of propane

International Nuclear Information System (INIS)

Kootenaei, A.H. Shahbazi; Towfighi, J.; Khodadadi, A.; Mortazavi, Y.

2014-01-01

Highlights: • Vanadia supported on titanate nanotube shows enhanced dispersion of vanadia. • Deactivatoin during propane ODH related to the rutile development. • Titanate nanotube transfers to anatase due to calcinations and presence of vanadia. - Abstract: Titanate nanotubes with a high specific surface area were synthesized by the simple hydrothermal method and investigated as support for V 2 O 5 catalyst in oxidative dehydrogenation of propane (ODP). The structures of pristine nanotubes as well as the prepared catalysts were investigated by XRD, Raman, FTIR, HRTEM, SEM, EDS, BET, and XPS techniques. The characterization of the as-synthesized nanotubes showed the synthesis of hydrogen titanate nanotube. The incipient wetness impregnation method was utilized to prepare VTNT-x (x = 5, 10, and 15 wt.% vanadia supported on nanotube) together with VTi5 (5 wt.% vanadia supported on Degussa P25). The anatase phase was developed in VTNT-x catalysts upon calcination along with specific surface area loss. Higher vanadia loading resulted in the lowering of support capacity in maintaining vanadia in dispersed state such that eventually crystalline vanadia appeared. The measured catalyst activity demonstrates that in spite of major support surface area loss in VTNT-5 catalyst, the propylene yield is superior in comparison with VTi5 catalyst. The catalyst activity can be correlated with maximum reduction temperature. Deactivation of VTi5 and VTNT-5 as well as VTNT-15 were studied for 3,000 min time-on-stream. It was found that the activity of VTNT-5 catalyst remain unchanged while a decline in catalytic activity observed in VTi5 and VTNT-15 catalysts. The development of rutile was considered as being a major element in the deactivation of the investigated catalysts which is influenced by the presence of vanadium and reaction atmosphere

Stability and catalytic performance of vanadia supported on nanostructured titania catalyst in oxidative dehydrogenation of propane

Energy Technology Data Exchange (ETDEWEB)

Kootenaei, A.H. Shahbazi [Department of Chemical Engineering, College of Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Towfighi, J., E-mail: towfighi@modares.ac.ir [Department of Chemical Engineering, College of Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Khodadadi, A.; Mortazavi, Y. [Catalysis and Nanostructured Materials Laboratory, Oil and Gas Processing Center of Excellence, Department of Chemical Engineering, College of Engineering, University of Tehran, P.O. Box 11365-4563, Tehran (Iran, Islamic Republic of)

2014-04-01

Highlights: • Vanadia supported on titanate nanotube shows enhanced dispersion of vanadia. • Deactivatoin during propane ODH related to the rutile development. • Titanate nanotube transfers to anatase due to calcinations and presence of vanadia. - Abstract: Titanate nanotubes with a high specific surface area were synthesized by the simple hydrothermal method and investigated as support for V{sub 2}O{sub 5} catalyst in oxidative dehydrogenation of propane (ODP). The structures of pristine nanotubes as well as the prepared catalysts were investigated by XRD, Raman, FTIR, HRTEM, SEM, EDS, BET, and XPS techniques. The characterization of the as-synthesized nanotubes showed the synthesis of hydrogen titanate nanotube. The incipient wetness impregnation method was utilized to prepare VTNT-x (x = 5, 10, and 15 wt.% vanadia supported on nanotube) together with VTi5 (5 wt.% vanadia supported on Degussa P25). The anatase phase was developed in VTNT-x catalysts upon calcination along with specific surface area loss. Higher vanadia loading resulted in the lowering of support capacity in maintaining vanadia in dispersed state such that eventually crystalline vanadia appeared. The measured catalyst activity demonstrates that in spite of major support surface area loss in VTNT-5 catalyst, the propylene yield is superior in comparison with VTi5 catalyst. The catalyst activity can be correlated with maximum reduction temperature. Deactivation of VTi5 and VTNT-5 as well as VTNT-15 were studied for 3,000 min time-on-stream. It was found that the activity of VTNT-5 catalyst remain unchanged while a decline in catalytic activity observed in VTi5 and VTNT-15 catalysts. The development of rutile was considered as being a major element in the deactivation of the investigated catalysts which is influenced by the presence of vanadium and reaction atmosphere.

Lightning generation in Titan due to the electrical self-polarization properties of Methane

Science.gov (United States)

Quintero, A.; Falcón, N.

2009-05-01

We describe an electrical charge process in Titan's thunderclouds, due to the self-polarization properties or pyroelectricity of methane, which increases the internal electric field in thunderclouds and facilitates the charge generation and separation processes. Microphysics that generates lightning flashes is associated with the physical and chemical properties of the local atmosphere, so methane could be the principal agent of the electrical activity because of its great concentration in Titan's atmosphere. Besides, Titan's electrical activity should not be very influenced by Saturn's magnetosphere because lightning occurs at very low altitude above Titan's surface, compared with the greater distance of Saturn's magnetosphere and Titan's troposphere. Using an electrostatic treatment, we calculate the internal electric field of Titan's thunderclouds due to methane's pyroelectrical properties, 7.05×10^11 Vm^-1; and using the telluric capacitor approximation for thunderclouds, we calculate the total charge obtained for a typical Titan thundercloud, 2.67×10^9 C. However, it is not right to use an electrostatic treatment because charge times are very fast due to the large methane concentration in Titan's clouds and the life time of thunderclouds is very low (around 2 hours). We consider a time dependent mechanism, employing common Earth atmospheric approaches, because of the similitude in chemical composition of both atmospheres (mainly nitrogen), so the typical charge of a thundercloud in Titan should reach between 20 C to 40 C, like on Earth. We obtain that lightning occurs with a frequency between 2 and 6 KHz. In Titan's atmosphere, methane concentration is higher than on Earth, and atmospheric electrical activity is stronger, so this model could be consistent with the observed phenomenology.

Enhancement of the solubility, thermal stability, and electronic properties of carbon nanotubes functionalized with MEH-PPV: A combined experimental and computational study

International Nuclear Information System (INIS)

Prajongtat, P.; Suramitr, S.; Hannongbua, S.; Gleeson, M.P.; Mitsuke, K.

2013-01-01

Multi-walled carbon nanotubes (MWCNTs) functionalized with poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MWCNT-f-MEH-PPV) nanocomposites were successfully prepared by employing a “grafting from” approach. The content of the functionalizing MEH-PPV in the composites was observed as 76 wt.%. Compared with pristine MWCNTs (p-MWCNT), the aqueous solubility and thermal stability of the former are significantly enhanced. The effect of covalently and non-covalently functionalized nanotubes on dye-sensitized solar cell performance was also studied. Solar cells were successfully fabricated from isolated MEH-PPV, p-MWCNT/MEH-PPV, and MWCNT-f-MEH-PPV/MEH-PPV counter electrodes. The devices based on a MWCNT-f-MEH-PPV/MEH-PPV counter electrode demonstrated the best photovoltaic performance as observed by higher J SC, V OC, and fill factor (FF) values. The experimental phenomena can be explained by quantum-chemical calculations: Charge transfer from MEH-PPV oligomers to nanotubes is greater when covalently functionalized compared with non-covalently functionalized. This suggests that the improvement in the photovoltaic parameters of the cells containing covalently functionalized nanotubes results not only from the higher concentration present in the nanotube films of the counter electrode, but also from the greater electron delocalization between the oligomers and nanotubes. (author)

Titan: a laboratory for prebiological organic chemistry

Science.gov (United States)

Sagan, C.; Thompson, W. R.; Khare, B. N.

1992-01-01

When we examine the atmospheres of the Jovian planets (Jupiter, Saturn, Uranus, and Neptune), the satellites in the outer solar system, comets, and even--through microwave and infrared spectroscopy--the cold dilute gas and grains between the stars, we find a rich organic chemistry, presumably abiological, not only in most of the solar system but throughout the Milky Way galaxy. In part because the composition and surface pressure of the Earth's atmosphere 4 x 10(9) years ago are unknown, laboratory experiments on prebiological organic chemistry are at best suggestive; but we can test our understanding by looking more closely at the observed extraterrestrial organic chemistry. The present Account is restricted to atmospheric organic chemistry, primarily on the large moon of Saturn. Titan is a test of our understanding of the organic chemistry of planetary atmospheres. Its atmospheric bulk composition (N2/CH4) is intermediate between the highly reducing (H2/He/CH4/NH3/H2O) atmospheres of the Jovian planets and the more oxidized (N2/CO2/H2O) atmospheres of the terrestrial planets Mars and Venus. It has long been recognized that Titan's organic chemistry may have some relevance to the events that led to the origin of life on Earth. But with Titan surface temperatures approximately equal to 94 K and pressures approximately equal to 1.6 bar, the oceans of the early Earth have no ready analogue on Titan. Nevertheless, tectonic events in the water ice-rich interior or impact melting and slow re-freezing may lead to an episodic availability of liquid water. Indeed, the latter process is the equivalent of a approximately 10(3)-year-duration shallow aqueous sea over the entire surface of Titan.

Aortic Graft Infection Secondary to Iatrogenic Transcolonic Graft Malposition.

Science.gov (United States)

Blank, Jacqueline J; Rothstein, Abby E; Lee, Cheong Jun; Malinowski, Michael J; Lewis, Brian D; Ridolfi, Timothy J; Otterson, Mary F

2018-01-01

Aortic graft infections are a rare but devastating complication of aortic revascularization. Often infections occur due to contamination at the time of surgery. Iatrogenic misplacement of the limbs of an aortobifemoral graft is exceedingly rare, and principles of evaluation and treatment are not well defined. We report 2 cases of aortobifemoral bypass graft malposition through the colon. Case 1 is a 54-year-old male who underwent aortobifemoral bypass grafting for acute limb ischemia. He had previously undergone a partial sigmoid colectomy for diverticulitis. Approximately 6 months after vascular surgery, he presented with an occult graft infection. Preoperative imaging and intraoperative findings were consistent with graft placement through the sigmoid colon. Case 2 is a 60-year-old male who underwent aortobifemoral bypass grafting due to a nonhealing wound after toe amputation. His postoperative course was complicated by pneumonia, bacteremia thought to be secondary to the pneumonia, general malaise, and persistent fevers. Approximately 10 weeks after the vascular surgery, he presented with imaging and intraoperative findings of graft malposition through the cecum. Aortic graft infection is usually caused by surgical contamination and presents as an indolent infection. Case 1 presented as such; Case 2 presented more acutely. Both grafts were iatrogenically misplaced through the colon at the index operation. The patients underwent extra-anatomic bypass and graft explantation and subsequently recovered.

Theoretical Calculations on Sediment Transport on Titan, and the Possible Production of Streamlined Forms

Science.gov (United States)

Burr, D. M.; Emery, J. P.; Lorenz, R. D.

2005-01-01

The Cassini Imaging Science System (ISS) has been returning images of Titan, along with other Saturnian satellites. Images taken through the 938 nm methane window see down to Titan's surface. One of the purposes of the Cassini mission is to investigate possible fluid cycling on Titan. Lemniscate features shown recently and radar evidence of surface flow prompted us to consider theoretically the creation by methane fluid flow of streamlined forms on Titan. This follows work by other groups in theoretical consideration of fluid motion on Titan's surface.

Radiation-Induced Graft Polymerization of Vinyl Monomers with Anion Groups onto MWNT Supports and Their Application as Electrogenerated Chemiluminescence (ECL Biosensors

Directory of Open Access Journals (Sweden)

Ji-Hye Park

2014-01-01

Full Text Available Vinyl polymer-grafted multiwalled carbon nanotube (MWNT supports with anion groups were prepared for use as biosensor supports by radiation-induced graft polymerization (RIGP of the vinyl monomers acryloyl diphosphoric acid (ADPA, acrylic acid (AA, sodium styrenesulfonate (NaSS, and methacrylic acid (MA onto the surface of MWNTs. The electrogenerated chemiluminescence sensors based on a glass carbon electrode (ECL-GCE and a screen printed electrode (ECL-SPE were fabricated by immobilization of Ru(bpy3 2+ complex after coating of vinyl polymer-grafted MWNT inks on the surface of the GCE and SPE without any polymer binders in order to obtain high electrogenerated chemiluminescence intensity. For detection of alcohol concentration, alcohol dehydrogenase (ADH was immobilized onto an ECL-GCE sensor prepared by poly(NaSS-g-MWNT supports. The prepared biosensor based on ADH is suitable for the detection of ethanol concentration in commercial drinks.

Preparation of Pd-loaded La-doped TiO{sub 2} nanotubes and investigation of their photocatalytic activity under visible light

Energy Technology Data Exchange (ETDEWEB)

Zong, Lanlan; Li, Qiuye, E-mail: qiuyeli@henu.edu.cn; Zhang, Jiwei; Wang, Xiaodong; Yang, Jianjun [Henan University, Key Laboratory for Special Functional Materials (China)

2013-11-15

Orthorhombic titanic acid nanotubes (TAN) have large BET surface area and small-diameter one-dimensional nanotubular morphology, so they can work as a good supporter and a precursor of TiO{sub 2}. However, in our former research, we found that calcination of TAN to anatase TiO{sub 2} would destroy the nanotubular structure and decrease the BET surface area sharply. In this work, we utilized the pillar effect of the foreign nanoparticles (La{sub 2}O{sub 3}) to keep the nanotubular morphology of TiO{sub 2}, and obtained the anatase TiO{sub 2} nanotubes with large BET surface area. For improving the photocatalytic activity, Pd nanoparticles were loaded as the electron traps on the surface of La-doped TiO{sub 2} by photo-deposition method. The photocatalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, diffuse reflectance spectra, and N{sub 2} adsorption–desorption isotherms measurement. Their photocatalytic activities were evaluated by the removal of propylene under visible light irradiation (λ ≥ 420 nm). The results showed that the photocatalytic activity of Pd-loaded La-doped TiO{sub 2} nanotubes improved effectively compared with that of La-doped TiO{sub 2} and pure TiO{sub 2}.

The safety designs for the TITAN reversed-field pinch reactor study

International Nuclear Information System (INIS)

Wong, C.P.C.; Cheng, E.T.; Creedon, R.L.; Hoot, C.G.; Schultz, K.R.; Grotz, S.P.; Blanchard, J.; Sharafat, S.; Najmabadi, F.

1989-01-01

TITAN is a study to investigate the potential of the reversed-field pinch concept as a compact, high-power density energy system. Two reactor concepts were developed, a self-cooled lithium design with vanadium structure and an aqueous solution loop-in-pool design, both operating at 18 MW/m 2 . The key safety features of the TITAN-I lithium-vanadium blanket design are in material selection, fusion power core configuration selection, lithium piping connections, and passive lithium drain tank system. Based on these safety features and results from accident evaluation, TITAN-I can at least be rated at a level 3 of safety assurance. For the TITAN-II aqueous loop-in-pool design, the key passive feature is the complete submersion of the fusion power core and the corresponding primary coolant loop system into a pool of low temperature water. Based on this key safety design feature, the TITAN-II design can be rated at a level 2 of safety assurance. (orig.)

The safety designs for the TITAN reversed-field pinch reactor study

International Nuclear Information System (INIS)

Wong, C.P.C.; Cheng, E.T.; Creedon, R.L.; Hoot, C.G.; Schultz, K.R.; Grotz, S.P.; Blanchard, J.P.; Sharafat, S.; Najmabadi, F.

1988-01-01

TITAN is a study to investigate the potential of the reversed-field pinch concept as a compact, high-power density energy system. Two reactor concepts were developed, a self-cooled lithium design with vanadium structure and an aqueous solution loop-in-pool design, both operating at 18 MW/m 2 . The key safety features of the TITAN-I lithium-vanadium blanket design are in material selection, fusion power core configuration selection, lithium piping connections and passive lithium drain tank system. Based on these safety features and results from accident evaluation, TITAN-I can at least be rated as level 3 of safety assurance. For the TITAN-II aqueous loop-in-pool design, the key passive feature is the complete submersion of the fusion power core and the corresponding primary coolant loop system into a pool of low temperature water. Based on this key safety design feature, the TITAN-II design can be rated as level 2 of safety assurance. 7 refs., 2 figs

Tritium release from lithium titanate, a low-activation tritium breeding material

International Nuclear Information System (INIS)

Kopasz, J.P.; Miller, J.M.; Johnson, C.E.

1994-01-01

The goals for fusion power are to produce energy in as safe, economical, and environmentally benign a manner as possible. To ensure environmentally sound operation low-activation materials should be used where feasible. The ARIES Tokamak Reactor Study has based reactor designs on the concept of using low-activation materials throughout the fusion reactor. For the tritium breeding blanket, the choices for low activation tritium breeding materials are limited. Lithium titanate is an alternative low-activation ceramic material for use in the tritium breeding blanket. To date, very little work has been done on characterizing the tritium release for lithium titanate. We have thus performed laboratory studies of tritium release from irradiated lithium titanate. The results indicate that tritium is easily removed from lithium titanate at temperatures as low as 600 K. The method of titanate preparation was found to affect the tritium release, and the addition of 0.1% H 2 to the helium purge gas did not improve tritium recovery. ((orig.))

Synthesis and Photocatalytic Activity of Anatase TiO2 Nanoparticles-coated Carbon Nanotubes

Directory of Open Access Journals (Sweden)

Xie Yi

2009-01-01

Full Text Available Abstract A simple and straightforward approach to prepare TiO2-coated carbon nanotubes (CNTs is presented. Anatase TiO2 nanoparticles (NPs with the average size ~8 nm were coated on CNTs from peroxo titanic acid (PTA precursor even at low temperature of 100 °C. We demonstrate the effects of CNTs/TiO2 molar ratio on the adsorption capability and photocatalytic efficiency under UV–visible irradiation. The samples showed not only good optical absorption in visible range, but also great adsorption capacity for methyl orange (MO dye molecules. These properties facilitated the great enhancement of photocatalytic activity of TiO2 NPs-coated CNTs photocatalysts. The TiO2 NPs-coated CNTs exhibited 2.45 times higher photocatalytic activity for MO degradation than that of pure TiO2.

Detection and mapping of organic molecules in Titan's atmosphere using ALMA

Science.gov (United States)

Cordiner, Martin

2016-06-01

Titan's atmospheric photochemistry results in the production of a wide range of organic molecules, including hydrocarbons, nitriles, aromatics and other complex species of possible pre-biotic relevance. Studies of Titan's atmospheric chemistry thus provide a unique opportunity to explore the origin and evolution of organic matter in primitive (terrestrial) planetary atmospheres. The Atacama Large Millimeter/submillimeter Array (ALMA) is a powerful new facility, well suited to the study of molecular emission from Titan's upper and middle-atmosphere. Results will be presented from our ongoing studies of Titan using ALMA data obtained during the period 2012-2014 [1,2], including detection and mapping of emission from C2H5CN, HNC, HC3N, CH3CN and CH3CCH. In addition, combining data from multiple ALMA Band 6 observations, we obtained high-resolution spectra with unprecedented sensitivity, enabling the first detection of C2H3CN (vinyl cyanide) on Titan, and derived a mean C2H3CN C2H5CN abundance ratio above 300 km of 0.3. Vinyl cyanide has recently been investigated as a possible constituent of (pre-biotic) vesicle membranes in Titan's liquid CH4 oceans [3]. Radiative transfer models and possible chemical formation pathways for the detected molecules will be discussed. ALMA observations provide instantaneous snapshot mapping of Titan's entire Earth-facing hemisphere for gases inaccessible to previous studies, and therefore provide new insights into photochemical production and transport, particularly at higher altitudes. Our maps show spatially resolved peaks in Titan's northern and southern hemispheres, consistent with the molecular distributions found in previous studies at infrared wavelengths by Voyager and Cassini, but high-altitude longitudinal asymmetries in our nitrile data indicate that the mesosphere may be more spatially variable than previously thought.

The Influence of Runoff and Surface Hydrology on Titan's Weather and Climate

Science.gov (United States)

Faulk, S.; Lora, J. M.; Mitchell, J.; Moon, S.

2017-12-01

Titan's surface liquid distribution has been shown by general circulation models (GCMs) to greatly influence the hydrological cycle, producing characteristic weather and seasonal climate patterns. Simulations from the Titan Atmospheric Model (TAM) with imposed polar methane "wetlands" reservoirs realistically produce observed cloud features and temperature profiles of Titan's atmosphere, whereas "aquaplanet" simulations with a global methane ocean are not as successful. In addition, wetlands simulations, unlike aquaplanet simulations, demonstrate strong correlations between extreme rainfall behavior and observed geomorphic features, indicating the influential role of precipitation in shaping Titan's surface. The wetlands configuration is, in part, motivated by Titan's large-scale topography featuring low-latitude highlands and high-latitude lowlands, with the implication being that methane may concentrate in the high-latitude lowlands by way of runoff and subsurface flow of a global or regional methane table. However, the extent to which topography controls the surface liquid distribution and thus impacts the global hydrological cycle by driving surface and subsurface flow is unclear. Here we present TAM simulations wherein the imposed wetlands reservoirs are replaced by a surface runoff scheme that allows surface liquid to self-consistently redistribute under the influence of topography. We discuss the impact of surface runoff on the surface liquid distribution over seasonal timescales and compare the resulting hydrological cycle to observed cloud and surface features, as well as to the hydrological cycles of the TAM wetlands and aquaplanet simulations. While still idealized, this more realistic representation of Titan's hydrology provides new insight into the complex interaction between Titan's atmosphere and surface, demonstrates the influence of surface runoff on Titan's global climate, and lays the groundwork for further surface hydrology developments in Titan

A FAMILY OF PEROXO-TITANATE MATERIALS TAILORED FOR OPTIMAL STRONTIUM ANDACTINIDE SORPTION

International Nuclear Information System (INIS)

Hobbs, D

2006-01-01

Achieving global optimization of inorganic sorbent efficacy, as well as tailoring sorbent specificity for target sorbates would facilitate increased wide-spread use of these materials in applications such as producing potable water or nuclear waste treatment. Sodium titanates have long been known as sorbents for radionuclides; 90 Sr and transuranic elements in particular. We have developed a related class of materials, which we refer to as peroxo-titanates: these are sodium titanates or hydrous titanates synthesized in the presence of or treated post-synthesis with hydrogen peroxide. Peroxo-titanates show remarkable and universal improved sorption behavior with respect to separation of actinides and strontium from Savannah River Site (SRS) nuclear waste simulants. Enhancement in sorption kinetics can potentially result in as much as an order of magnitude increase in batch processing throughput. Peroxo-titanates have been produced by three different synthetic routes: post-synthesis peroxide-treatment of a commercially produced monosodium titanate, an aqueous-peroxide synthetic route, and an isopropanol-peroxide synthetic route. The peroxo-titanate materials are characteristically yellow to orange, indicating the presence of protonated or hydrated Ti-peroxo species; and the chemical formula can be generally written as H v Na w Ti 2 O 5 -(xH 2 O)[yH z O 2 ] where (v+w) = 2, z = 0-2, and total volatile species accounts for 25-50 wt % of the solid. Further enhancement of sorption performance is achieved by processing, storing and utilizing the peroxo-titanate as an aqueous slurry rather than a dry powder, and post-synthesis acidification. All three synthesis modifications; addition of hydrogen peroxide, use of a slurry form and acidification can be applied more broadly to the optimization of other metal oxide sorbents and other ion separations processes

IN SITU MEASUREMENTS OF THE SIZE AND DENSITY OF TITAN AEROSOL ANALOGS

Energy Technology Data Exchange (ETDEWEB)

Hoerst, S. M.; Tolbert, M. A, E-mail: sarah.horst@colorado.edu [Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO (United States)

2013-06-10

The organic haze produced from complex CH{sub 4}/N{sub 2} chemistry in the atmosphere of Titan plays an important role in processes that occur in the atmosphere and on its surface. The haze particles act as condensation nuclei and are therefore involved in Titan's methane hydrological cycle. They also may behave like sediment on Titan's surface and participate in both fluvial and aeolian processes. Models that seek to understand these processes require information about the physical properties of the particles including their size and density. Although measurements obtained by Cassini-Huygens have placed constraints on the size of the haze particles, their densities remain unknown. We have conducted a series of Titan atmosphere simulation experiments and measured the size, number density, and particle density of Titan aerosol analogs, or tholins, for CH{sub 4} concentrations from 0.01% to 10% using two different energy sources, spark discharge and UV. We find that the densities currently in use by many Titan models are higher than the measured densities of our tholins.

Infrared Spectra and Optical Constants of Nitrile Ices Relevant to Titan's Atmosphere

Science.gov (United States)

Anderson, Carrie; Ferrante, Robert F.; Moore, W. James; Hudson, Reggie; Moore, Marla H.

2011-01-01

Spectra and optical constants of nitrile ices known or suspected to be in Titan?s atmosphere have been determined from 2.0 to 333.3 microns (approx.5000 to 30/cm). These results are relevant to the ongoing modeling of Cassini CIRS observations of Titan?s winter pole. Ices studied were: HCN, hydrogen cyanide; C2N2, cyanogen; CH3CN, acetonitrile; C2H5CN, propionitrile; and HC3N, cyanoacetylene. Optical constants were calculated, using Kramers-Kronig analysis, for each nitrile ice?s spectrum measured at a variety of temperatures, in both the amorphous- and crystalline phases. Spectra were also measured for many of the nitriles after quenching at the annealing temperature and compared with those of annealed ices. For each of these molecules we also measured the real component, n, of the refractive index for amorphous and crystalline phases at 670 nm. Several examples of the information contained in these new data sets and their usefulness in modeling Titan?s observed features will be presented (e.g., the broad emission feature at 160/cm; Anderson and Samuelson, 2011).

IN SITU MEASUREMENTS OF THE SIZE AND DENSITY OF TITAN AEROSOL ANALOGS

International Nuclear Information System (INIS)

Hörst, S. M.; Tolbert, M. A

2013-01-01

The organic haze produced from complex CH 4 /N 2 chemistry in the atmosphere of Titan plays an important role in processes that occur in the atmosphere and on its surface. The haze particles act as condensation nuclei and are therefore involved in Titan's methane hydrological cycle. They also may behave like sediment on Titan's surface and participate in both fluvial and aeolian processes. Models that seek to understand these processes require information about the physical properties of the particles including their size and density. Although measurements obtained by Cassini-Huygens have placed constraints on the size of the haze particles, their densities remain unknown. We have conducted a series of Titan atmosphere simulation experiments and measured the size, number density, and particle density of Titan aerosol analogs, or tholins, for CH 4 concentrations from 0.01% to 10% using two different energy sources, spark discharge and UV. We find that the densities currently in use by many Titan models are higher than the measured densities of our tholins.

Synthesis and characterization of polyacrylic acid- grafted-carboxylic graphene/titanium nanotube composite for the effective removal of enrofloxacin from aqueous solutions: Adsorption and photocatalytic degradation studies.

Science.gov (United States)

Anirudhan, Thayyath S; Shainy, F; Christa, J

2017-02-15

Polyacrylic acid-grafted-carboxylic graphene/titanium nanotube (PAA-g-CGR/TNT) composite was synthesized. It was effectively used as adsorbent as well as photocatalyst. The composite was characterized by FTIR, XRD, SEM, TEM, Surface Area Analyzer, XPS and DRS. The photocatalytic activity of PAA-g-CGR/TNT composite was evaluated on the basis of the degradation of pollutants by using sunlight. The band gap of the prepared photocatalyst was found to be 2.6eV. The removal of the antibiotic enrofloxacin (ENR) was achieved by two step mechanism based on adsorption and photodegradation. The maximum adsorption was observed at pH 5.0. The best fitted kinetic model was found to be pseudo-second-order. The maximum adsorption was observed at 30°C. The maximum adsorption capacity was found to be 13.40mg/g. The kinetics of photodegradation of ENR onto PAA-g-CGR/TNT composite follow first-order kinetics and optimum pH was found to be 5.0. The regeneration and reuse of the adsorbent-cum-photocatalyst were also examined upto five cycles. Copyright © 2016 Elsevier B.V. All rights reserved.

Technological properties and structure of titanate melts

International Nuclear Information System (INIS)

Morozov, A.A.

2002-01-01

Power substantiation of existence of tough stream of complex anion ([TiO 6 ] 8- ) as a prevalent unit in titanate melts is given on the base of up-to-date knowledge about structure of metallurgical slags and results of investigations of thermophysical properties of these melts. It is shown that high crystallization ability of titanate melts at technological temperatures is determined by heterogeneity of liquid state - by presence up to 30 % of dispersed particles of solid phase solutions in matrix liquid [ru

Observations of CO in Titan's Atmosphere Using ALMA

Science.gov (United States)

Serigano, Joseph; Nixon, Conor A.; Cordiner, Martin; Irwin, Patrick G. J.; Teanby, Nicholas; Charnley, Steven B.; Lindberg, Johan E.; Remijan, Anthony J.

2015-11-01

The advent of the Atacama Large Millimeter/submillimeter Array (ALMA) has provided a powerful facility for probing the atmospheres of solar system targets at long wavelengths (84-720 GHz) where the rotational lines of small, polar molecules are prominent. In the dense, nitrogen-dominated atmosphere of Titan, photodissociation of molecular nitrogen and methane leads to a wealth of complex hydrocarbons and nitriles in small abundances. Past millimeter/submillimeter observations, including ground-based observations as well as those by the Composite Infrared Spectrometer (CIRS) aboard the Cassini spacecraft, have proven the significance of this wavelength region for the derivation of vertical mixing profiles, latitudinal and seasonal variations, and molecular detections. Previous ALMA studies of Titan have presented mapping and vertical column densities of hydrogen isocyanide (HNC) and cyanoacetylene (HC3N) (Cordiner et al. 2014) as well as the first spectroscopic detection of ethyl cyanide (C2H5CN) in Titan’s atmosphere (Cordiner et al. 2015).Here, we report several submillimetric observations of carbon monoxide (CO) and its isotopologues 13CO, C18O, and C17O in Titan’s atmosphere obtained with flux calibration data from the ALMA Science Archive. We employ NEMESIS, a line-by-line radiative transfer code, to determine the stratospheric abundances of these molecules. The abundance of CO in Titan's atmosphere is determined to be approximately 50±1 ppm, constant with altitude, and isotopic ratios are determined to be approximately 12C/13C = 90, 16O/18O = 470, and 16O/17O = 2800. This report presents the first spectroscopic detection of C17O in the outer solar system, detected at >11σ confidence. This talk will focus on isotopic ratios in CO in Titan's atmosphere and will compare our results to previously measured values for Titan and other bodies in the Solar System. General implications for the history of Titan from measurements of CO and its isotopologues will be

Functional materials based on carbon nanotubes: Carbon nanotube actuators and noncovalent carbon nanotube modification

Science.gov (United States)

Fifield, Leonard S.

Carbon nanotubes have attractive inherent properties that encourage the development of new functional materials and devices based on them. The use of single wall carbon nanotubes as electromechanical actuators takes advantage of the high mechanical strength, surface area and electrical conductivity intrinsic to these molecules. The work presented here investigates the mechanisms that have been discovered for actuation of carbon nanotube paper: electrostatic, quantum chemical charge injection, pneumatic and viscoelastic. A home-built apparatus for the measurement of actuation strain is developed and utilized in the investigation. An optical fiber switch, the first demonstrated macro-scale device based on the actuation of carbon nanotubes, is described and its performance evaluated. Also presented here is a new general process designed to modify the surface of carbon nanotubes in a non-covalent, non-destructive way. This method can be used to impart new functionalities to carbon nanotube samples for a variety of applications including sensing, solar energy conversion and chemical separation. The process described involves the achievement of large degrees of graphitic surface coverage with polycyclic aromatic hydrocarbons through the use of supercritical fluids. These molecules are bifunctional agents that anchor a desired chemical group to the aromatic surface of the carbon nanotubes without adversely disrupting the conjugated backbone that gives rise the attractive electronic and physical properties of the nanotubes. Both the nanotube functionalization work and the actuator work presented here emphasize how an understanding and control of nanoscale structure and phenomena can be of vital importance in achieving desired performance for active materials. Opportunities for new devices with improved function over current state-of-the-art can be envisioned and anticipated based on this understanding and control.

Titan's Primordial Soup: Formation of Amino Acids via Low Temperature Hydrolysis of Tholins

Science.gov (United States)

Neish, Catherine; Somogyi, Á.; Smith, M. A.

2009-09-01

Titan, Saturn's largest moon, is a world rich in the "stuff of life". Reactions occurring in its dense nitrogen-methane atmosphere produce a wide variety of organic molecules, which subsequently rain down onto its surface. Water - thought to be another important ingredient for life - is likewise abundant on Titan. Theoretical models of Titan's formation predict that its interior consists of an ice I layer several tens of kilometers thick overlying a liquid ammonia-rich water layer several hundred kilometers thick (Tobie et al., 2005). Though its surface temperature of 94K dictates that Titan is on average too cold for liquid water to persist at its surface, melting caused by impacts and/or cryovolcanism may lead to its episodic availability. Impact melt pools on Titan would likely remain liquid for 102 - 104 years before freezing (O'Brien et al., 2005). The combination of complex organic molecules and transient locales of liquid water make Titan an interesting natural laboratory for studying prebiotic chemistry. In this work, we sought to determine what biomolecules might be formed under conditions analogous to those found in transient liquid water environments on Titan. We hydrolyzed Titan organic haze analogues, or "tholins", in 13 wt. % ammonia-water at 253K and 293K for a year. Using a combination of high resolution mass spectroscopy and tandem mass spectroscopy fragmentation techniques, four amino acids were identified in the hydrolyzed tholin sample. These four species have been assigned as the amino acids asparagine, aspartic acid, glutamine, and glutamic acid. This represents the first detection of biologically relevant molecules created under conditions similar to those found in impact melt pools and cryolavas on Titan. Future missions to Titan should therefore carry instrumentation capable of detecting amino acids and other prebiotically relevant molecules on its surface This work was supported by the NASA Exobiology Program.

Nanotube cathodes.

Energy Technology Data Exchange (ETDEWEB)

Overmyer, Donald L.; Lockner, Thomas Ramsbeck; Siegal, Michael P.; Miller, Paul Albert

2006-11-01

Carbon nanotubes have shown promise for applications in many diverse areas of technology. In this report we describe our efforts to develop high-current cathodes from a variety of nanotubes deposited under a variety of conditions. Our goal was to develop a one-inch-diameter cathode capable of emitting 10 amperes of electron current for one second with an applied potential of 50 kV. This combination of current and pulse duration significantly exceeds previously reported nanotube-cathode performance. This project was planned for two years duration. In the first year, we tested the electron-emission characteristics of nanotube arrays fabricated under a variety of conditions. In the second year, we planned to select the best processing conditions, to fabricate larger cathode samples, and to test them on a high-power relativistic electron beam generator. In the first year, much effort was made to control nanotube arrays in terms of nanotube diameter and average spacing apart. When the project began, we believed that nanotubes approximately 10 nm in diameter would yield sufficient electron emission properties, based on the work of others in the field. Therefore, much of our focus was placed on measured field emission from such nanotubes grown on a variety of metallized surfaces and with varying average spacing between individual nanotubes. We easily reproduced the field emission properties typically measured by others from multi-wall carbon nanotube arrays. Interestingly, we did this without having the helpful vertical alignment to enhance emission; our nanotubes were randomly oriented. The good emission was most likely possible due to the improved crystallinity, and therefore, electrical conductivity, of our nanotubes compared to those in the literature. However, toward the end of the project, we learned that while these 10-nm-diameter CNTs had superior crystalline structure to the work of others studying field emission from multi-wall CNT arrays, these nanotubes still

Nanotube cathodes

International Nuclear Information System (INIS)

Overmyer, Donald L.; Lockner, Thomas Ramsbeck; Siegal, Michael P.; Miller, Paul Albert

2006-01-01

Carbon nanotubes have shown promise for applications in many diverse areas of technology. In this report we describe our efforts to develop high-current cathodes from a variety of nanotubes deposited under a variety of conditions. Our goal was to develop a one-inch-diameter cathode capable of emitting 10 amperes of electron current for one second with an applied potential of 50 kV. This combination of current and pulse duration significantly exceeds previously reported nanotube-cathode performance. This project was planned for two years duration. In the first year, we tested the electron-emission characteristics of nanotube arrays fabricated under a variety of conditions. In the second year, we planned to select the best processing conditions, to fabricate larger cathode samples, and to test them on a high-power relativistic electron beam generator. In the first year, much effort was made to control nanotube arrays in terms of nanotube diameter and average spacing apart. When the project began, we believed that nanotubes approximately 10 nm in diameter would yield sufficient electron emission properties, based on the work of others in the field. Therefore, much of our focus was placed on measured field emission from such nanotubes grown on a variety of metallized surfaces and with varying average spacing between individual nanotubes. We easily reproduced the field emission properties typically measured by others from multi-wall carbon nanotube arrays. Interestingly, we did this without having the helpful vertical alignment to enhance emission; our nanotubes were randomly oriented. The good emission was most likely possible due to the improved crystallinity, and therefore, electrical conductivity, of our nanotubes compared to those in the literature. However, toward the end of the project, we learned that while these 10-nm-diameter CNTs had superior crystalline structure to the work of others studying field emission from multi-wall CNT arrays, these nanotubes still

Grafting

Energy Technology Data Exchange (ETDEWEB)

Garnett, J L [New South Wales Univ., Kensington (Australia). School of Chemistry

1979-01-01

The unique value of ionizing radiation for the initiation of grafting to backbone polymers is discussed. The principles of the technique are briefly reviewed. The conditions under which free radicals and ions participate in these reactions are examined. Examples of representative grafting processes are considered to illustrate where the technique can be of potential commercial value to a wide range of industries. The general principles of these grafting reactions are shown to be applicable to radiation induced rapid cure technology such as is provided by electron beam processing facilities. Grafting reactions initiated by UV are also treated and shown to be of importance because of the many similarities in properties of the ionizing radiation and UV systems, also the rapid industrial exploitation of EB and sensitized UV processing technology. Possible future trends in radiation grafting are outlined.

MICROSTRUCTURE CHARACTERISTIC OF ALUMINUM TITANATE SYNTHESIED BY BOTH SOLID- STATE AND SOL-GEL PROCESSES

Directory of Open Access Journals (Sweden)

M. Khosravi Saghezchi

2015-12-01

Full Text Available A comparing study on formation and microstructure features of aluminum titanate is investigated through both solid-state and sol-gel processes. Aluminum titanate formed by firing at 1350ºC and 1450ºC for 4h in solid-state process. In the sol-gel process formation of submicron sized particles is followed by addition of sucrose into the transparent sol. XRD analysis was confirmed the formation of aluminum titanate at 1400ºC  in lower duration of calcination (3h without any additives in the sol-gel process. In this work 2wt% MgO is added to the samples as the additive for forming acceleration of aluminum titanate. The influence of MgO addition and heat treatment are studied on phase formation and microstructure development of aluminum titanate in both procedures. Additive optimizes aluminum titanate formation at lower temperatures (1300-1350ºC. Phase and microstructure studies of Mg containing samples optimally show significance in aluminum titanate formation.

Large catchment area recharges Titan's Ontario Lacus

Science.gov (United States)

Dhingra, Rajani D.; Barnes, Jason W.; Yanites, Brian J.; Kirk, Randolph L.

2018-01-01

We seek to address the question of what processes are at work to fill Ontario Lacus while other, deeper south polar basins remain empty. Our hydrological analysis indicates that Ontario Lacus has a catchment area spanning 5.5% of Titan's surface and a large catchment area to lake surface area ratio. This large catchment area translates into large volumes of liquid making their way to Ontario Lacus after rainfall. The areal extent of the catchment extends to at least southern mid-latitudes (40°S). Mass conservation calculations indicate that runoff alone might completely fill Ontario Lacus within less than half a Titan year (1 Titan year = 29.5 Earth years) assuming no infiltration. Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations of clouds over the southern mid and high-latitudes are consistent with precipitation feeding Ontario's large catchment area. This far-flung rain may be keeping Ontario Lacus filled, making it a liquid hydrocarbon oasis in the relatively dry south polar region.

Light scattering measurements with Titan's aerosols analogues produced by dusty plasma

Science.gov (United States)

Hadamcik, E.; Renard, J.-B.; Szopa, C.; Cernogora, G.; Levasseur-Regourd, A. C.

The Titan s atmosphere contains solid aerosols produced by the photochemistry of nitrogen and methane These aerosols are at the origin of the characteristic brown yellow colour of Titan During the descent of the Huygens probe the 14 th January 2005 optical measurements of the Titan s haze and Titan s surface have been done In order to explain the obtained results laboratory simulations are necessary We produce analogues of the Titan s aerosols in a RF capacitively coupled low-pressure plasma in a N 2 --CH 4 mixture representative of the Titan s atmosphere Szopa et al 2006 Szopa et al this conference The morphology of the produced solid aerosols is observed by SEM analyses They are quasi spherical and their mean size is function of the plasma conditions Moreover their colour changes from yellow to brown as a function of CH 4 ratio in the plasma In order to have information on the optical properties of the produced aerosols measurements have been performed with the PROGRA2 experiment Renard et al 2002 The PROGRA2 experiment measures the phase dependence of the linear polarization of the light scattered by dust particles for two wavelengths 543 5 nm and 632 8 nm The particles are lifted either in microgravity in the CNES ESA dedicated airplane or by an air-draught in ground-based conditions The aim of this work is to build a database for further modelling of the optical properties of Titan s in connection with the Huygens data These particles have also an astrophysical interest as organic compounds Hadamcik et

Coexistence of Dunes and Humid Conditions at Titan's Tropics

Science.gov (United States)

Radebaugh, Jani; Lorenz, R. D.; Lunine, J. I.; Kirk, R. L.; Ori, G. G.; Farr, T. G.; Malaska, M.; Le Gall, A.; Liu, Z. Y. C.; Encrenaz, P. J.; Paillou, P.; Hayes, A.; Lopes, R. M. C.; Turtle, E. P.; Wall, S. D.; Stofan, E. R.; Wood, C. A.; Cassini RADAR Team

2012-10-01

At Titan's equatorial latitudes there are tens of thousands of dunes, a landform typical of desert environments where sand does not become anchored by vegetation or fluids. Model climate simulations predict generally dry conditions at the equator and humid conditions near the poles of Titan, where lakes of methane/ethane are found. However, moderate relative methane humidity was observed at the Huygens landing site, recent rainfall was seen by Cassini ISS near the Belet Sand Sea, and a putative transient lake in Shangri-La was observed by Cassini VIMS, all of which indicate abundant fluids may be present, at least periodically, at Titan's equatorial latitudes. Terrestrial observations and studies demonstrate dunes can exist and migrate in conditions of high humidity. Active dunes are found in humid climates, indicating the movement of sand is not always prohibited by the presence of fluids. Sand mobility is related to precipitation, evaporation and wind speed and direction. If dune surfaces become wetted by rainfall or rising subsurface fluids, they can become immobilized. However, winds can act to dry the uppermost layers, freeing sands for saltation and enabling dune migration in wet conditions. Active dunes are found in tropical NE Brazil and NE Australia, where there are alternating dry and wet periods, a condition possible for Titan's tropics. Rising and falling water levels lead to the alteration of dune forms, mainly from being anchored by vegetation, but also from cementation by carbonates or clays. Studies of Titan's dunes, which could undergo anchoring of organic sediments by hydrocarbon fluids, could inform the relative strength of vegetation vs. cementation at humid dune regions on Earth. Furthermore, a comprehensive survey of dune morphologies near regions deemed low by SARTopo and stereo, where liquids may collect in wet conditions, could reveal if bodies of liquid have recently existed at Titan's tropics.

Crystal structure of red lead titanate thin films

International Nuclear Information System (INIS)

Bursill, L.A.; Peng, J.L.; Jiang, B.; Li, X.

1998-01-01

Orange-red lead titanate thin films are examined by high-resolution transmission electron microscopy and diffraction. It is remarkable that the structure is based on that of tetragonal-tungsten-bronze (TTB) rather than perovskite-type. The chemical basis for this result is examined. It is deduced that the TTB structure is stabilized by inclusion of hydroxyl ions during synthesis by a sol-gel route involving hydrolysis of n-Butyl titanate

Predicting Passenger Survival Rates on the Titanic

OpenAIRE

Prateek Chanda

2017-01-01

The sinking of the RMS Titanic is one of the most infamous shipwrecks in history. On April 15, 1912, during her maiden voyage, the Titanic sank after colliding with an iceberg, killing 1502 out of 2224 passengers and crew. This sensational tragedy shocked the international community and led to better safety regulations for ships. One of the reasons that the shipwreck led to such loss of life was that there were not enough lifeboats for the passengers and crew. Although there was some el...

Behavior under Extreme Conditions: The Titanic Disaster

OpenAIRE

Bruno S. Frey; David A. Savage; Benno Torgler

2011-01-01

During the night of April 14, 1912, the RMS Titanic collided with an iceberg on her maiden voyage. Two hours and 40 minutes later she sank, resulting in the loss of 1,501 lives—more than two-thirds of her 2,207 passengers and crew. This remains one of the deadliest peacetime maritime disasters in history and by far the most famous. For social scientists, evidence about how people behaved as the Titanic sunk offers a quasi-natural field experiment to explore behavior under extreme conditions o...

Spectroscopy of carbonated chains: experimental investigation and observation of Titan's atmosphere

International Nuclear Information System (INIS)

Jolly, Antoine

2012-01-01

In this report for an Accreditation to Supervise Research (HDR), the author proposes an overview of his research works. These works first addressed quantitative spectroscopy and more particularly the measurement of absolute absorption coefficients which are necessary parameters for the quantification of molecules which are remotely sensed through their spectroscopic signature. Secondly, the author addresses the adjustment of line lists in the infrared for a better investigation of recent observations of Titan's atmosphere made by the Cassini mission. Thirdly, he reports the use of this line list for the processing of observations of Titan. The last part addresses an experimental atmospheric simulation which aims at reproducing Titan's atmosphere by submitting its main components (nitrogen and methane) to an energetic flow representative of what is present on Titan

In situ preparation of composite from conjugated polyschiff bases and multiwalled carbon nanotube: Synthesis, electrochromic, acidochromic properties

International Nuclear Information System (INIS)

Ma Lina; Cai Jiwei; Zhao Ping; Niu Haijun; Wang Cheng; Bai Xuduo; Wang Wen

2012-01-01

Graphical abstract: The introduction of carbon nanotubes greatly improves the photochromic property of the composites. Highlights: ► MWNTs/PSB composite was prepared by in situ polymerization with a new type of PSB. ► The introduction of carbon nanotubes greatly improves the photochromic property of the composites. ► The composites exhibited excellent thermal stability and reversible electrochemical behavior. - Abstract: Polyschiff base (PSB) which has the structure of C=N double bond is well known as conducting material with high thermal resistance, chemical and electrical properties. Recently, it was used as hole transporting material in organic light emitting diode (OLED), chemical sensor and electrochromic materials. Carbon nanotubes (CNTs) with excellent properties such as unique electrical, mechanical, optical and chemical properties are promising reinforcing materials for polymer composites which improve the comprehensive properties of polymers. In this paper, conjugated PSB-grafted multiwalled carbon nanotubes (MWNTs) composite was prepared by in situ polymerization. The resultant composites were characterized by thermogravimetric (TGA), scanning electron microscopy (SEM), UV–vis absorption, photoluminescence (PL), cyclic voltammograms (CV), infrared spectroscopy (IR) and Raman spectroscopy. The composites exhibited high thermal stability and excellent reversibilities of electrochromic, photochromic, acidochromic characteristics, with the color change from the light yellow to blue.

Titan's Surface Composition from Cassini VIMS Solar Occultation Observations

Science.gov (United States)

McCord, Thomas; Hayne, Paul; Sotin, Christophe

2013-04-01

Titan's surface is obscured by a thick absorbing and scattering atmosphere, allowing direct observation of the surface within only a few spectral win-dows in the near-infrared, complicating efforts to identify and map geologi-cally important materials using remote sensing IR spectroscopy. We there-fore investigate the atmosphere's infrared transmission with direct measure-ments using Titan's occultation of the Sun as well as Titan's reflectance measured at differing illumination and observation angles observed by Cas-sini's Visual and Infrared Mapping Spectrometer (VIMS). We use two im-portant spectral windows: the 2.7-2.8-mm "double window" and the broad 5-mm window. By estimating atmospheric attenuation within these windows, we seek an empirical correction factor that can be applied to VIMS meas-urements to estimate the true surface reflectance and map inferred composi-tional variations. Applying the empirical corrections, we correct the VIMS data for the viewing geometry-dependent atmospheric effects to derive the 5-µm reflectance and 2.8/2.7-µm reflectance ratio. We then compare the cor-rected reflectances to compounds proposed to exist on Titan's surface. We propose a simple correction to VIMS Titan data to account for atmospheric attenuation and diffuse scattering in the 5-mm and 2.7-2.8 mm windows, generally applicable for airmass water ice for the majority of the low-to-mid latitude area covered by VIMS measurements. Four compositional units are defined and mapped on Titan's surface based on the positions of data clusters in 5-mm vs. 2.8/2.7-mm scatter plots; a simple ternary mixture of H2O, hydrocarbons and CO2 might explain the reflectance properties of these surface units. The vast equatorial "dune seas" are compositionally very homogeneous, perhaps suggesting transport and mixing of particles over very large distances and/or and very consistent formation process and source material. The composi-tional branch characterizing Tui Regio and Hotei Regio is

Nanomolecular gas sensor architectures based on functionalized carbon nanotubes for vapor detection

Science.gov (United States)

Hines, Deon; Zhang, Henan; Rümmeli, Mark H.; Adebimpe, David; Akins, Daniel L.

2015-05-01

There is enormous interest in detection of simple & complex odors by mean of electronic instrumentation. Specifically, our work focuses on creating derivatized-nanotube-based "electronic noses" for the detection and identification of gases, and other materials. We have grafted single-walled carbon nanotubes (SWNTs) with an array of electron-donating and electron withdrawing moieties and have characterized some of the physicochemical properties of the modified nanotubes. Gas sensing elements have been fabricated by spin coating the functionalized nanotubes onto interdigitated electrodes (IDE's), creating an array of sensors. Each element in the sensor array can contain a different functionalized matrix. This facilitates the construction of chemical sensor arrays with high selectivity and sensitivity; a methodology that mimics the mammalian olfactory system. Exposure of these coated IDEs to organic vapors and the successful classification of the data obtained under DC monitoring, indicate that the system can function as gas sensors of high repeatability and selectivity for a wide range of common analytes. Since the detection of explosive materials is also of concern in this research, our next phase focuses on explosives such as, TNT, RDX, and Triacetone Triperoxide (TATP). Sensor data from individual detection are assessed on their own individual merits, after which they are amalgamated and reclassified to present each vapor as unique data point on a 2-dimensional map and with minimum loss of information. This approach can assist the nation's need for a technology to defeat IEDs through the use of methods that detect unique chemical signatures associated with explosive molecules and byproducts.

Ethane ocean on Titan

Science.gov (United States)

Lunine, J. I.; Stevenson, D. J.; Yung, Y.L.

1983-01-01

Voyager I radio occultation data is employed to develop a qualitative model of an ethane ocean on Titan. It is suggested that the ocean contains 25 percent CH4 and that the ocean is in dynamic equilibrium with an N2 atmosphere. Previous models of a CH4 ocean are discounted due to photolysis rates of CH4 gas. Tidal damping of Titan's orbital eccentricity is taken as evidence for an ocean layer approximately 1 km deep, with the ocean floor being covered with a solid C2H2 layer 100 to 200 m thick. The photolytic process disrupting the CH4, if the estimates of the oceanic content of CH4 are correct, could continue for at least one billion years. Verification of the model is dependent on detecting CH4 clouds in the lower atmosphere, finding C2H6 saturation in the lower troposphere, or obtaining evidence of a global ocean.

Organic chemistry on Titan

Science.gov (United States)

Chang, S.; Scattergood, T.; Aronowitz, S.; Flores, J.

1979-01-01

Features taken from various models of Titan's atmosphere are combined in a working composite model that provides environmental constraints within which different pathways for organic chemical synthesis are determined. Experimental results and theoretical modeling suggest that the organic chemistry of the satellite is dominated by two processes: photochemistry and energetic particle bombardment. Photochemical reactions of CH4 in the upper atmosphere can account for the presence of C2 hydrocarbons. Reactions initiated at various levels of the atmosphere by cosmic rays, Saturn 'wind', and solar wind particle bombardment of a CH4-N2 atmospheric mixture can account for the UV-visible absorbing stratospheric haze, the reddish appearance of the satellite, and some of the C2 hydrocarbons. In the lower atmosphere photochemical processes will be important if surface temperatures are sufficiently high for gaseous NH3 to exist. It is concluded that the surface of Titan may contain ancient or recent organic matter (or both) produced in the atmosphere.

Equinoctial Activity Over Titan Dune Fields Revealed by Cassini/vims

Science.gov (United States)

Rodriguez, S.; Le Mouelic, S.; Barnes, J. W.; Hirtzig, M.; Rannou, P.; Sotin, C.; Brown, R. H.; Bow, J.; Vixie, G.; Cornet, T.; Bourgeois, O.; Narteau, C.; Courrech Du Pont, S.; Le Gall, A.; Reffet, E.; Griffith, C. A.; Jaumann, R.; Stephan, K.; Buratti, B. J.; Clark, R. N.; Baines, K. H.; Nicholson, P. D.; Coustenis, A.

2012-12-01

Titan, the largest satellite of Saturn, is the only satellite in the solar system with a dense atmosphere. The close and continuous observations of Titan by the Cassini spacecraft, in orbit around Saturn since July 2004, bring us evidences that Titan troposphere and low stratosphere experience an exotic, but complete meteorological cycle similar to the Earth hydrological cycle, with hydrocarbons evaporation, condensation in clouds, and rainfall. Cassini monitoring campaigns also demonstrate that Titan's cloud coverage and climate vary with latitude. Titan's tropics, with globally weak meteorological activity and widespread dune fields, seem to be slightly more arid than the poles, where extensive and numerous liquid reservoirs and sustained cloud activity have been discovered. Only a few tropo-spheric clouds have been observed at Titan's tropics during the southern summer. As equinox was approaching (in August 2009), they occurred more frequently and appeared to grow in strength and size. We present here the observation of intense brightening at Titan's tropics, very close to the equinox. These detections were conducted with the Visual and Infrared Mapping Spectrometer (VIMS) onboard Cassini. We will discuss the VIMS images of the three individual events detected so far, observed during the Titan's flybys T56 (22 May 2009), T65 (13 January 2010) and T70 (21 June 2010). T56, T65 and T70 observations show an intense and transient brighten-ing of large regions very close to the equator, right over the extensive dune fields of Senkyo, Belet and Shangri-La. They all appear spectrally and morphologically different from all transient surface features or atmospheric phenomena previously reported. Indeed, these events share in particular a strong brightening at wavelengths greater than 2 μm (especially at 5 μm), making them spectrally distinct from the small tropical clouds observed before the equinox and the large storms observed near the equator in September and October

Descent imager/spectral radiometer (DISR) instrument aboard the Huygens probe of Titan

Science.gov (United States)

Tomasko, Martin G.; Doose, Lyn R.; Smith, Peter H.; Fellows, C.; Rizk, B.; See, C.; Bushroe, M.; McFarlane, E.; Wegryn, E.; Frans, E.; Clark, R.; Prout, M.; Clapp, S.

1996-10-01

The Huygen's probe of the atmosphere of Saturn's moon Titan includes one optical instrument sensitive to the wavelengths of solar radiation. The goals of this investigation fall into four broad areas: 1) the measurement of the profile of solar heating to support an improved understanding of the thermal balance of Titan and the role of the greenhouse effect in maintaining Titan's temperature structure; 2) the measurement of the size, vertical distribution, and optical properties of the aerosol and cloud particles in Titan's atmosphere to support studies of the origin, chemistry, life cycles, and role in the radiation balance of Titan played by these particles; 3) the composition of the atmosphere, particularly the vertical profile of the mixing ratio of methane, a condensable constituent in Titan's atmosphere; and 4) the physical state, composition, topography, and physical processes at work in determining the nature of the surface of Titan and its interaction with Titan's atmosphere. In order to accomplish these objectives, the Descent Imager/Spectral Radiometer (DISR) instrument makes extensive use of fiber optics to bring the light from several different sets of foreoptics to a silicon CCD detector, to a pair of InGaAs linear array detectors, and to three silicon photometers. Together these detectors permit DISR to make panoramic images of the clouds and surface of Titan, to measure the spectrum of upward and downward streaming sunlight from 350 to 1700 nm at a resolving power of about 200, to measure the reflection spectrum of >= 3000 locations on the surface, to measure the brightness and polarization of the solar aureole between 4 and 30 degrees from the sun at 500 and 935 nm, to separate the direct and diffuse downward solar flux at each wavelength measured, and to measure the continuous reflection spectrum of the ground between 850 and 1600 nm using an onboard lamp in the last 100 m of the descent.

Grafting and curing

International Nuclear Information System (INIS)

Garnett, J.L.; Loo-Teck Ng; Visay Viengkhou

1998-01-01

Progress in radiation grafting and curing is briefly reviewed. The two processes are shown to be mechanistically related. The parameters influencing yields are examined particularly for grafting. For ionising radiation grafting systems (EB and gamma ray) these include solvents, substrate and monomer structure, dose and dose-rate, temperature and more recently role of additives. In addition, for UV grafting, the significance of photoinitiators is discussed. Current applications of radiation grafting and curing are outlined. The recent development of photoinitiator free grafting and curing is examined as well as the potential for the new excimer laser sources. The future application of both grafting and curing is considered, especially the significance of the occurrence of concurrent grafting during cure and its relevance in environmental considerations

One-step synthesis of continuous free-standing Carbon Nanotubes-Titanium oxide composite films as anodes for lithium-ion batteries

International Nuclear Information System (INIS)

Gao, Hongxu; Hou, Feng; Wan, Zhipeng; Zhao, Sha; Yang, Deming; Liu, Jiachen; Guo, Anran; Gong, Yuxuan

2015-01-01

Highlights: • CNTs/TiO 2 compoiste films synthesized are continuous and free-standing. • The film can be directly used as flexible, binder-free Lithium-Ion Battery electrode. • The CNTs/TiO 2 electrodes exhibit excellent rate capacity and cyclic stability. • Our strategy is readily applicable to fabricate other CNTs-based composite films. - Abstract: Continuous free-standing Carbon Nanotubes (CNTs)/Titanium oxide (TiO 2 ) composite films were fabricated in a vertical CVD gas flow reactor with water sealing by the One-Step Chemical Vapor Deposition (CVD) approach. The composite films consist of multiple layers of conductive carbon nanotube networks with titanium oxide nanoparticles decorating on carbon nanotube surface. The as-synthesized flexible and transferrable composite films show excellent electrochemical properties, when the content of tetrabutyl titanate is 19.0 wt.%, which can be promising as binder-free anodes for Lithium-Ion Battery (LIB) applications. It demonstrates remarkably high rate capacity of 150 mAh g −1 , as well as excellent high rate cyclic stability over 500 cycles (current density of 3000 mA g −1 ). Such observations can be attributed to the relatively larger surface area and pore volume comparing with pristine CNT films. Great potentials of CNTs/TiO 2 composite films for large-scale production and application in energy devices were shown

Polycyclic aromatic hydrocarbons in the atmospheres of Titan and Jupiter

Science.gov (United States)

Sagan, Carl; Khare, B. N.; Thompson, W. R.; Mcdonald, G. D.; Wing, Michael R.; Bada, Jeffrey L.; Vo-Dinh, Tuan; Arakawa, E. T.

1993-01-01

PAHs are important components of the interstellar medium and carbonaceous chondrites, but have never been identified in the reducing atmospheres of the outer solar system. Incompletely characterized complex organic solids (tholins) produced by irradiating simulated Titan atmospheres reproduce well the observed UV/visible/IR optical constants of the Titan stratospheric haze. Titan tholin and a tholin generated in a crude simulation of the atmosphere of Jupiter are examined by two-step laser desorption/multiphoton ionization mass spectrometry. A range of two- to four-ring PAHs, some with one to four alkylation sites, are identified, with a net abundance of about 0.0001 g/g (grams per gram) of tholins produced. Synchronous fluorescence techniques confirm this detection. Titan tholins have proportionately more one- and two-ring PAHs than do Jupiter tholins, which in turn have more four-ring and larger PAHs. The four-ringed PAH chrysene, prominent in some discussions of interstellar grains, is found in Jupiter tholins.

The Titan haze revisted: Magnetospheric energy sorces quantitative tholin yields

Science.gov (United States)

Thompson, W. Reid; Mcdonald, Gene D.; Sagan, Carl

1994-01-01

We present laboratory measurements of the radiation yields of complex organic solids produced from N2/CH4 gas mixtures containing 10 or 0.1% CH4. These tholins are thought to resemble organic aerosols produced in the atmospheres of Titan, Pluto, and Triton. The tholin yields are large compared to the total yield of gaseous products: nominally, 13 (C + N)/100 eV for Titan tholin and 2.1 (C + N)/100 eV for Triton tholin. High-energy magnetospheric electrons responsible for tholin production represents a class distinct from the plasma electrons considered in models of Titan's aiglow. Electrons with E greater than 20 keV provide an energy flux approximately 1 x 10(exp -2) erg/cm/sec, implying from our measured tholin yields a mass flux of 0.5 to 4.0 x 10(exp -14) g/sq cm/sec of tholin. (The corresponding thickness of the tholin sedimentary column accumulated over 4 Gyr on Titan's surface is 4 to 30 m). This figure is in agreement with required mass fluxes computed from recent radiative transfer and sedimentation models. If, however, theses results, derived from experiments at approximately 2 mb, are applied to lower pressure levels toward peak auroral electron energy deposition and scaled with pressure as the gas-phase organic yields, the derived tholin mass flux is at least an order of magnitude less. We attrribute this difference to the fact that tholin synthesis occurs well below the level of maximum electron energy depositon and to possible contributions to tholis from UV-derived C2-hydrocarbons. We conclude that Tita tholin, produced by magnetospheric electrons, is alone sufficient to supply at least a significant fraction of Titan's haze-a result consistent with the fact that the optical properties of Titan tholin, among all proposed material, are best at reproducing Titan's geometric albedo spectrum from near UV to mid-IR in light-scattering models.

Are Titan's radial Labyrinth terrains surface expressions of large laccoliths?

Science.gov (United States)

Schurmeier, L.; Dombard, A. J.; Malaska, M.; Radebaugh, J.

2017-12-01

The Labyrinth terrain unit may be the one of the best examples of the surface expression of Titan's complicated history. They are characterized as highly eroded, dissected, and elevated plateaus and remnant ridges, with an assumed composition that is likely organic-rich based on radar emissivity. How these features accumulated organic-rich sediments and formed topographic highs by either locally uplifting or surviving pervasive regional deflation or erosion is an important question for understanding the history of Titan. There are several subsets of Labyrinth terrains, presumably with differing evolutionary histories and formation processes. We aim to explain the formation of a subset of Labyrinth terrain units informally referred to as "radial Labyrinth terrains." They are elevated and appear dome-like, circular in planform, have a strong radial dissection pattern, are bordered by Undifferentiated Plains units, and are found in the mid-latitudes. Based on their shape, clustering, and dimensions, we suggest that they may be the surface expression of large subsurface laccoliths. A recent study by Manga and Michaut (Icarus, 2017) explained Europa's lenticulae (pits, domes, spots) with the formation of saucer-shaped sills that form laccoliths around the brittle-ductile transition depth within the ice shell (1-5 km). Here, we apply the same scaling relationships and find that the larger size of radial labyrinth terrains with Titan's higher gravity implies deeper intrusion depths of around 20-40 km. This intrusion depth matches the expected brittle-ductile transition on Titan based on our finite element simulations and yield strength envelope analyses. We hypothesize that Titan's radial labyrinth terrains formed as cryovolcanic (water) intrusions that rose to the brittle-ductile transition within the ice shell where they spread horizontally, and uplifted the overlying ice. The organic-rich sedimentary cover also uplifted, becoming more susceptible to pluvial and fluvial

The key to Mars, Titan and beyond?

International Nuclear Information System (INIS)

Zubrin, R.M.

1990-01-01

This paper discusses the use of nuclear rockets using indigenous Mars propellants for future missions to Mars and Titan, which would drastically reduce the mass and cost of the mission while increasing its capability. Special attention is given to the CO2-powered nuclear rocket using indigenous Martian fuel (NIMF) vehicle for hopping around on Mars. If water is available on Mars, it could make a NIMF propellant yielding an exhaust velocity of 3.4 km/sec, good enough to allow a piloted NIMF spacecraft to ascent from the surface of Mars and propel itself directly to LEO; if water is available on Phobos, a NIMF spacecraft could travel to earth orbit and then back to Phobos or Mars without any additional propellant from earth. One of the many exciting missions beyond Mars that will be made possible by NIMF technology is the exploration of Saturn's moon Titan. A small automated NIMF Titan explorer, with foldout wings and a NERVA (Nuclear Engine for Rocket Vehicle Applications) engine, is proposed

Modified titanate perovskites in photocatalytic water splitting

Energy Technology Data Exchange (ETDEWEB)

Wlodarczak, M.; Ludwiczak, M.; Laniecki, M. [A. Mickiewicz Univ. (Poland)

2010-07-01

Received materials have structure of perovskite, what was shown by XRD diffraction patterns. Perovskite structure is present in all samples with strontium, barium and one sample with calcium. Moreover, received barium and strontium titanate are very similar to pattern materials. XRD results show, that temperature 500 C is too low to create perovskite structure in CaTiO{sub 3}. However, it is high enough in case of SrTiO{sub 3} and BaTiO{sub 3}. One regularity is obvious, surface area increases for samples calcined in lower temperature. There is a connection between surface area and dispersion of platinum. Both of them reach the greatest value to the calcium titanate. Catalytic activity was shown by all of received samples. Measurable values were received to samples calcined in 700 C. Calcium titanate had the best catalytic activity, both an amount of hydrogen and a ratio of hydrogen to platinum. There is one regularity to all samples, the ration of hydrogen to platinum increase when amount of platinum decrease. (orig.)

Crystal structure of red lead titanate thin films

Energy Technology Data Exchange (ETDEWEB)

Bursill, L.A.; Peng, J.L.; Jiang, B. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Li, X. [Jilin Univ., Changchun, JL (China). Dept of Chemistry

1998-09-01

Orange-red lead titanate thin films are examined by high-resolution transmission electron microscopy and diffraction. It is remarkable that the structure is based on that of tetragonal-tungsten-bronze (TTB) rather than perovskite-type. The chemical basis for this result is examined. It is deduced that the TTB structure is stabilized by inclusion of hydroxyl ions during synthesis by a sol-gel route involving hydrolysis of n-Butyl titanate 7 refs., 1 tab., 4 figs.

Titan's interior from its rotation axis orientation and its Love number

Science.gov (United States)

Baland, Rose-Marie; Gabriel, Tobie; Axel, Lefèvre

2013-04-01

The tidal Love number k2 of Titan has been recently estimated from Cassini flybys radio-tracking and is consistent with the presence of a global ocean in Titan's interior, located between two ice layers (Iess et al. 2012), in accordance with prediction from interior and evolutionary models for Titan. Previously, the orientation of the rotation axis of Titan has been measured on the basis of radar images from Cassini (Stiles et al. 2008). Titan's obliquity, is about 0.3. The measured orientation is more consistent with the presence of a global internal liquid ocean than with an entirely solid Titan (Baland et al. 2011). The global topography data of Titan seem to indicate some departure from the hydrostatic shape expected for a synchronous satellite under the influence of its rotation and the static tides raised by the central planet (Zebker et al. 2009). This may be explained by a differential tidal heating in the ice shell which flattens the poles (Nimmo and Bills 2010). A surface more flattened than expected implies compensation in depth to explain the measured gravity coefficients C20 and C22 of Iess et al. (2012). Here, all layers are assumed to have a tri-axial ellipsoid shape, but with polar and equatorial flattenings that differ from the hydrostatic expected ones. We assess the influence of this non-hydrostatic shape on the conclusions of Baland et al. (2011), which developped a Cassini state model for the orientation of the rotation axis of a synchronous satellite having an internal liquid layer. We assess the possibility to constrain Titan's interior (and particularly the structure of the water/ice layer) from both the rotation axis orientation and the Love number. We consider a range of internal structure models consistent with the mean density and the mean radius of Titan, and made of a shell, an ocean, a mantle, and a core, from the surface to the center, with various possible compositions (e.g. ammonia mixed with water for the ocean). The internal

Rheological and mechanical properties of polypropylene prepared with multi-walled carbon nanotube masterbatch.

Science.gov (United States)

Shim, Young-Sun; Park, Soo-Jin

2012-07-01

In this study, the effects of polypropylene-grafted maleic-anhydride-treated multi-walled carbon nanotubes (PP-MWNTs) on the viscoelastic behaviors and mechanical properties of a polypropylene-(PP)-based composite system were examined. The PP-MWNT/PP composites were prepared via melt mixing with a 3:1 ratio of PP-g-MA and acid-treated MWNTs at 220 degrees C. The surface characteristics of the PP-MWNTs were confirmed via Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). The viscoelastic behavior and mechanical properties of the PP-MWNT/PP composites were confirmed using a rheometer and an ultimate testing machine (UTM). The storage and loss moduli increased with increasing PP-MWNT content. The critical intensity stress factor (K(IC)) of the PP-MWNT/PP composites at high filler loading was also higher than that of the MWNT/PP composites. In conclusion, the viscoelastic behavior and mechanical properties of MWNT/PP can be improved by grafting MWNTs to PP-g-MA.

Improvement of conditions for ceramics sintering on the base of lead zirconate-titanate

International Nuclear Information System (INIS)

Glinchuk, M.D.; Kim, P.V.; Bykov, I.P.; Lyashchenko, A.B.

1989-01-01

Lead zirconate-titanate powders of different graininess are studied for their phase composition. The finest grains of the powder consist of lead zirconate-titanate with the rhombohedral structure. Grains of 3-5 μm size are a mixture of lead zirconate-titanate and lead titanate, the latter exceeding 50% (by weight) causes the effect of anomalous expansion in the process of sintering. Control of the technological parameters of the synthesis permits producing powder with favourable correlation of the above phases and grain sizes. Sintering of such a powder induces no effect of the anomalous expansion with an increased density of the product attained

Amino-Functionalized Multiwalled Carbon Nanotubes Lead to Successful Ring-Opening Polymerization of Poly(ε-caprolactone): Enhanced Interfacial Bonding and Optimized Mechanical Properties.

Science.gov (United States)

Roumeli, Eleftheria; Papageorgiou, Dimitrios G; Tsanaktsis, Vasilios; Terzopoulou, Zoe; Chrissafis, Konstantinos; Avgeropoulos, Apostolos; Bikiaris, Dimitrios N

2015-06-03

In this work, the synthesis, structural characteristics, interfacial bonding, and mechanical properties of poly(ε-caprolactone) (PCL) nanocomposites with small amounts (0.5, 1.0, and 2.5 wt %) of amino-functionalized multiwalled carbon nanotubes (f-MWCNTs) prepared by ring-opening polymerization (ROP) are reported. This method allows the creation of a covalent-bonding zone on the surface of nanotubes, which leads to efficient debundling and therefore satisfactory dispersion and effective load transfer in the nanocomposites. The high covalent grafting extent combined with the higher crystallinity provide the basis for a significant enhancement of the mechanical properties, which was detected in the composites with up to 1 wt % f-MWCNTs. Increasing filler concentration encourages intrinsic aggregation forces, which allow only minor grafting efficiency and poorer dispersion and hence inferior mechanical performance. f-MWCNTs also cause a significant improvement on the polymerization reaction of PCL. Indeed, the in situ polymerization kinetics studies reveal a significant decrease in the reaction temperature, by a factor of 30-40 °C, combined with accelerated the reaction kinetics during initiation and propagation and a drastically reduced effective activation energy.

Anion and cation diffusion in barium titanate and strontium titanate; Anionen- und Kationendiffusion in Barium- und Strontiumtitanat

Energy Technology Data Exchange (ETDEWEB)

Kessel, Markus Franz

2012-12-19

Perovskite oxides show various interesting properties providing several technical applications. In many cases the defect chemistry is the key to understand and influence the material's properties. In this work the defect chemistry of barium titanate and strontium titanate is analysed by anion and cation diffusion experiments and subsequent time-of-flight secondary ion mass spectrometry (ToF-SIMS). The reoxidation equation for barium titanate used in multi-layer ceramic capacitors (MLCCs) is found out by a combination of different isotope exchange experiments and the analysis of the resulting tracer diffusion profiles. It is shown that the incorporation of oxygen from water vapour is faster by orders of magnitude than from molecular oxygen. Chemical analysis shows the samples contain various dopants leading to a complex defect chemistry. Dysprosium is the most important dopant, acting partially as a donor and partially as an acceptor in this effectively acceptor-doped material. TEM and EELS analysis show the inhomogeneous distribution of Dy in a core-shell microstructure. The oxygen partial pressure and temperature dependence of the oxygen tracer diffusion coefficients is analysed and explained by the complex defect chemistry of Dy-doped barium titanate. Additional fast diffusion profiles are attributed to fast diffusion along grain boundaries. In addition to the barium titanate ceramics from an important technical application, oxygen diffusion in cubic, nominally undoped BaTiO{sub 3} single crystals has been studied by means of {sup 18}O{sub 2}/{sup 16}O{sub 2} isotope exchange annealing and subsequent determination of the isotope profiles in the solid by ToF-SIMS. It is shown that a correct description of the diffusion profiles requires the analysis of the diffusion through the surface space-charge into the material's bulk. Surface exchange coefficients, space-charge potentials and bulk diffusion coefficients are analysed as a function of oxygen partial

Landform Evolution Modeling of Specific Fluvially Eroded Physiographic Units on Titan

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Moore, J. M.; Howard, A. D.; Schenk, P. M.

2015-01-01

Several recent studies have proposed certain terrain types (i.e., physiographic units) on Titan thought to be formed by fluvial processes acting on local uplands of bedrock or in some cases sediment. We have earlier used our landform evolution models to make general comparisons between Titan and other ice world landscapes (principally those of the Galilean satellites) that we have modeled the action of fluvial processes. Here we give examples of specific landscapes that, subsequent to modeled fluvial work acting on the surfaces, produce landscapes which resemble mapped terrain types on Titan.

Titan Density Reconstruction Using Radiometric and Cassini Attitude Control Flight Data

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Andrade, Luis G., Jr.; Burk, Thomas A.

2015-01-01

This paper compares three different methods of Titan atmospheric density reconstruction for the Titan 87 Cassini flyby. T87 was a unique flyby that provided independent Doppler radiometric measurements on the ground throughout the flyby including at Titan closest approach. At the same time, the onboard accelerometer provided an independent estimate of atmospheric drag force and density during the flyby. These results are compared with the normal method of reconstructing atmospheric density using thruster on-time and angular momentum accumulation. Differences between the estimates are analyzed and a possible explanation for the differences is evaluated.

Grafting the alar rim: application as anatomical graft.

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Gruber, Ronald P; Fox, Paige; Peled, Anne; Belek, Kyle A

2014-12-01

Alar rim contour and alar rim grafts have become essential components of rhinoplasty. Ideally, grafts of the nose should be anatomical in shape. So doing might make grafts of the alar rim more robust. The authors considered doing that by applying the graft as a continuous extension of the lateral crus. Twelve patients (two men and 10 women) constituted the study group (seven primary and five secondary cases). Of those, there were five concave rims, two concave rims with rim retraction, two boxy tips, and three cephalically oriented lateral crura. Surgical technique included the following: (1) an open approach was used; (2) a marginal incision that ignored the caudal margin of the lateral crus (the incision went straight posteriorly to a point 5 to 6 mm from the rim margin) was used; (3) a triangular graft was made to cover the exposed vestibular skin; (4) it was secured end to end to the caudal border of the lateral crus; and (5) the poster end was allowed to sit in a small subcutaneous pocket. Follow-up was 11 to 19 months. All 12 patients exhibited good rims as judged by a blinded panel. Rim retraction was not fully corrected in one patient, but no further treatment was required. One patient did require a secondary small rim graft for residual rim concavity. The concept of grafting the alar rim is strongly supported by the authors' results. The modifications the authors applied by designing the graft to be anatomical in shape has been a technical help.

Fabrication of crystal-oriented barium-bismuth titanate ceramics in high magnetic field and subsequent reaction sintering

International Nuclear Information System (INIS)

Tanaka, Satoshi; Tomita, Yusuke; Furushima, Ryoichi; Uematsu, Keizo; Shimizu, Hiroyuki; Doshida, Yutaka

2009-01-01

High magnetic field was applied to fabricate novel lead-free piezoelectric ceramics with a textured structure. A compact of crystallographically oriented grains was prepared by dry forming in a high magnetic field from a mixed slurry of bismuth titanate and barium titanate powders. Bismuth titanate particles with a size of about 1 μ m were used as the host material. In the forming process, the slurry was poured into a mold and set in a magnetic field of 10 T until completely dried. Bismuth titanate particles were highly oriented in the slurry under the magnetic field. The dried powder compact consisted of highly oriented bismuth titanate particles and randomly oriented barium titanate particles. Barium bismuth titanate ceramics with a- and b-axis orientations were successfully produced from the dried compact by sintering at temperatures above 1100 deg. C.

Printed Barium Strontium Titanate capacitors on silicon

Energy Technology Data Exchange (ETDEWEB)

Sette, Daniele [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Luxembourg Institute of Science and Technology LIST, Materials Research and Technology Department, L-4422 Belvaux (Luxembourg); Kovacova, Veronika [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Defay, Emmanuel, E-mail: emmanuel.defay@list.lu [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Luxembourg Institute of Science and Technology LIST, Materials Research and Technology Department, L-4422 Belvaux (Luxembourg)

2015-08-31

In this paper, we show that Barium Strontium Titanate (BST) films can be prepared by inkjet printing of sol–gel precursors on platinized silicon substrate. Moreover, a functional variable capacitor working in the GHz range has been made without any lithography or etching steps. Finally, this technology requires 40 times less precursors than the standard sol–gel spin-coating technique. - Highlights: • Inkjet printing of Barium Strontium Titanate films • Deposition on silicon substrate • Inkjet printed silver top electrode • First ever BST films thinner than 1 μm RF functional variable capacitor that has required no lithography.

Proficiency feasibility of multi-walled carbon nanotubes in the presence of polymeric surfactant on enhanced oil recovery

Science.gov (United States)

Nezhad, Javad Razavi; Jafari, Arezou; Abdollahi, Mahdi

2018-01-01

Enhanced heavy oil recovery methods are widely utilized to increase oil recovery. For this purpose, polymer and surfactant flooding have been used extensively. Recently, polymeric surfactant flooding has become an attractive alternative to sole polymer flooding due to their capability of providing an increase in solution viscosity and a decrease in interfacial tension, which are both beneficial for efficiency of the process. Applying nanoparticles as an additive to polymer solutions is a method to improve viscosity and alter rock wettability. Therefore, in this research, multi-walled carbon nanotube (MWCNT) was mixed with a polymeric surfactant of polyacrylamide-graft-lignin copolymer (PAM-g-L) synthesized via radical grafting reaction. Moreover, several solutions with different concentrations of nanoparticles with PAM-g-L were prepared. The solutions were injected into a micromodel to evaluate the PAM-g-L flooding efficiency in presence of the multi-walled carbon nanotubes. The results of micromodel flooding showed that increasing MWCNT concentration results in lower sweep efficiencies; and consequently, oil production will decrease. Therefore, MWCNT along with PAM-g-L has an unacceptable performance in enhanced heavy oil recovery. But data of wettability tests revealed that MWCNT can change the wettability from oil-wet to water-wet. In addition, the combination of the PAM-g-L and MWCNT in a solution will cause more water-wet condition.

Titan: a distant but enticing destination for human visitors.

Science.gov (United States)

Nott, Julian

2009-10-01

Until recently, very little was known about Saturn's largest satellite, Titan. But that has changed dramatically since the Cassini spacecraft started orbiting in the Saturn system in 2004. Larger than Mercury and with a dense atmosphere, Titan has many of the characteristics of a planet. Indeed, many scientists now see it as the most interesting place in the Solar System for robotic exploration, with many unique features and even the possibility of exotic forms of life. This paper points out that Titan is also a potential destination for humans. With its predominantly nitrogen atmosphere, moderate gravity, and available water and oxygen, it also appears that, once it becomes possible to travel there, it will prove to be much more hospitable for human visitors than any other destination in the Solar System.

Barium titanate thick films prepared by screen printing technique

Directory of Open Access Journals (Sweden)

Mirjana M. Vijatović

2010-06-01

Full Text Available The barium titanate (BaTiO3 thick films were prepared by screen printing technique using powders obtained by soft chemical route, modified Pechini process. Three different barium titanate powders were prepared: i pure, ii doped with lanthanum and iii doped with antimony. Pastes for screen printing were prepared using previously obtained powders. The thick films were deposited onto Al2O3 substrates and fired at 850°C together with electrode material (silver/palladium in the moving belt furnace in the air atmosphere. Measurements of thickness and roughness of barium titanate thick films were performed. The electrical properties of thick films such as dielectric constant, dielectric losses, Curie temperature, hysteresis loop were reported. The influence of different factors on electrical properties values was analyzed.

Implications of Wind-Assisted Aerial Navigation for Titan Mission Planning and Science Exploration

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Elfes, A.; Reh, K.; Beauchamp, P.; Fathpour, N.; Blackmore, L.; Newman, C.; Kuwata, Y.; Wolf, M.; Assad, C.

2010-01-01

The recent Titan Saturn System Mission (TSSM) proposal incorporates a montgolfiere (hot air balloon) as part of its architecture. Standard montgolfiere balloons generate lift through heating of the atmospheric gases inside the envelope, and use a vent valve for altitude control. A Titan aerobot (robotic aerial vehicle) would have to use radioisotope thermoelectric generators (RTGs) for electric power, and the excess heat generated can be used to provide thermal lift for a montgolfiere. A hybrid montgolfiere design could have propellers mounted on the gondola to generate horizontal thrust; in spite of the unfavorable aerodynamic drag caused by the shape of the balloon, a limited amount of lateral controllability could be achieved. In planning an aerial mission at Titan, it is extremely important to assess how the moon-wide wind field can be used to extend the navigation capabilities of an aerobot and thereby enhance the scientific return of the mission. In this paper we explore what guidance, navigation and control capabilities can be achieved by a vehicle that uses the Titan wind field. The control planning approach is based on passive wind field riding. The aerobot would use vertical control to select wind layers that would lead it towards a predefined science target, adding horizontal propulsion if available. The work presented in this paper is based on aerodynamic models that characterize balloon performance at Titan, and on TitanWRF (Weather Research and Forecasting), a model that incorporates heat convection, circulation, radiation, Titan haze properties, Saturn's tidal forcing, and other planetary phenomena. Our results show that a simple unpropelled montgolfiere without horizontal actuation will be able to reach a broad array of science targets within the constraints of the wind field. The study also indicates that even a small amount of horizontal thrust allows the balloon to reach any area of interest on Titan, and to do so in a fraction of the time needed

NIAC Phase 1 Final Study Report on Titan Aerial Daughtercraft

Science.gov (United States)

Matthies, Larry

2017-01-01

Saturns giant moon Titan has become one of the most fascinating bodies in the Solar System. Even though it is a billion miles from Earth, data from the Cassini mission reveals that Titan has a very diverse, Earth-like surface, with mountains, fluvial channels, lakes, evaporite basins, plains, dunes, and seas [Lopes 2010] (Figure 1). But unlike Earth, Titans surface likely is composed of organic chemistry products derived from complex atmospheric photochemistry [Lorenz 2008]. In addition, Titan has an active meteorological system with observed storms and precipitation-induced surface darkening suggesting a hydrocarbon cycle analogous to Earths water cycle [Turtle 2011].Titan is the richest laboratory in the solar system for studying prebiotic chemistry, which makes studying its chemistry from the surface and in the atmosphere one of the most important objectives in planetary science [Decadal 2011]. The diversity of surface features on Titan related to organic solids and liquids makes long-range mobility with surface access important [Decadal 2011]. This has not been possible to date, because mission concepts have had either no mobility (landers), no surface access (balloons and airplanes), or low maturity, high risk, and/or high development costs for this environment (e,g. large, self-sufficient, long-duration helicopters). Enabling in situ mobility could revolutionize Titan exploration, similarly to the way rovers revolutionized Mars exploration. Recent progress on several fronts has suggested that small-scale rotorcraft deployed as daughtercraft from a lander or balloon mothercraft may be an effective, affordable approach to expanding Titan surface access. This includes rapid progress on autonomous navigation capabilities of such aircraft for terrestrial applications and on miniaturization, driven by the consumer mobile electronics market, of high performance of sensors, processors, and other avionics components needed for such aircraft. Chemical analysis, for

Experimental studies on 3D printing of barium titanate ceramics for medical applications

Directory of Open Access Journals (Sweden)

Schult Mark

2016-09-01

Full Text Available The present work deals with the 3D printing of porous barium titanate ceramics. Barium titanate is a biocompatible material with piezoelectric properties. Due to insufficient flowability of the starting material for 3D printing, the barium titanate raw material has been modified in three different ways. Firstly, barium titanate powder has been calcined. Secondly, flow additives have been added to the powder. And thirdly, flow additives have been added to the calcined powder. Finally, a polymer has been added to the three materials and specimens have been printed from these three material mixtures. The 3D printed parts were then sintered at 1320°C. The sintering leads to shrinkage which differs between 29.51–71.53% for the tested material mixtures. The porosity of the parts is beneficial for cell growth which is relevant for future medical applications. The results reported in this study demonstrate the possibility to fabricate porous piezoelectric barium titanate parts with a 3D printer that can be used for medical applications. 3D printed porous barium titanate ceramics can especially be used as scaffold for bone tissue engineering, where the bone formation can be promoted by electrical stimulation.

The Michigan Titan Thermospheric General Circulation Model (TTGCM)

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Bell, J. M.; Bougher, S. W.; de Lahaye, V.; Waite, J. H.

2005-12-01

The Cassini flybys of Titan since late October, 2004 have provided data critical to better understanding its chemical and thermal structures. With this in mind, a 3-D TGCM of Titan's atmosphere from 600km to the exobase (~1450km) has been developed. This paper presents the first results from the partially operational code. Currently, the TTGCM includes static background chemistry (Lebonnois et al 2001, Vervack et al 2004) coupled with thermal conduction routines. The thermosphere remains dominated by solar EUV forcing and HCN rotational cooling, which is calculated by a full line-by-line radiative transfer routine along the lines of Yelle (1991) and Mueller-Wodarg (2000, 2002). In addition, an approximate treatment of magnetospheric heating is explored. This paper illustrates the model's capabilities as well as some initial results from the Titan Thermospheric General Circulation model that will be compared with both the Cassini INMS data and the model of Mueller-Wodarg (2000,2002).

Nanotube phonon waveguide

Science.gov (United States)

Chang, Chih-Wei; Zettl, Alexander K.

2013-10-29

Disclosed are methods and devices in which certain types of nanotubes (e.g., carbon nanotubes and boron nitride nanotubes conduct heat with high efficiency and are therefore useful in electronic-type devices.

A post-Cassini view of Titan's methane-based hydrologic cycle

Science.gov (United States)

Hayes, Alexander G.; Lorenz, Ralph D.; Lunine, Jonathan I.

2018-05-01

The methane-based hydrologic cycle on Saturn's largest moon, Titan, is an extreme analogue to Earth's water cycle. Titan is the only planetary body in the Solar System, other than Earth, that is known to have an active hydrologic cycle. With a surface pressure of 1.5 bar and temperatures of 90 to 95 K, methane and ethane condense out of a nitrogen-based atmosphere and flow as liquids on the moon's surface. Exchange processes between atmospheric, surface and subsurface reservoirs produce methane and ethane cloud systems, as well as erosional and depositional landscapes that have strikingly similar forms to their terrestrial counterparts. Over its 13-year exploration of the Saturn system, the Cassini-Huygens mission revealed that Titan's hydrocarbon-based hydrology is driven by nested methane cycles that operate over a range of timescales, including geologic, orbital (for example, Croll-Milankovitch cycles), seasonal and that of a single convective storm. In this Review Article, we describe the dominant exchange processes that operate over these timescales and present a post-Cassini view of Titan's methane-based hydrologic system.

Co-crystal formation between two organic solids on the surface of Titan

Science.gov (United States)

Cable, M. L.; Vu, T. H.; Maynard-Casely, H. E.; Hodyss, R. P.

2017-12-01