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Specific surface area and structures of aluminas from fibrillar pseudoboehmite

Coelho, Antonio Carlos Vieira; Rocha, Gifone Aguiar; Santos, Persio de Souza; Santos, Helena Lopes de Souza; Kiyohara, Pedro Kunihiko
Fonte: UNIV FED RIO DE JANEIRO, LAB HIDROGENIO Publicador: UNIV FED RIO DE JANEIRO, LAB HIDROGENIO
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
767.117%
By heating powders of the aluminum monohydroxide fibrillar pseudoboehmite from 200 degrees C to 1400 degrees C several high surface area aluminas are prepared and characterized by X-ray diffraction and electron optical methods. Aqueous sols with pseudoboehmite fibrils of different lengths were dried by two methods: at room temperature and spray-dried. The following aluminas were obtained after treatment of the powders at increasing temperatures and having a range of specific surface areas: gamma-Al(2)O(3) (470 degrees C - 770 degrees C; 179 m(2)/g 497 m(2)/g); delta-Al(2)O(3) (770 degrees C - 930 degrees C; 156 m(2)/g - 230 m(2)/g); theta-Al(2)O(3) (930 degrees C - 1050 degrees C; 11 m(2)/g - 200 m(2)/g); alpha-Al(2)O(3) (1050 degrees C - 1400 degrees C; 2 m(2)/g - 17 m(2)/g). Spray-dried powders, fired at the same temperature than the ground powders, showed higher specific surface areas. The higher surface area alumina have values of the same order of magnitude of the commercial ""ad-cat"" aluminas.

Synthesis of high-surface-area gamma-Al2O3 from aluminum scrap and its use for the adsorption of metals: Pb(II), Cd(II) and Zn(II)

Asencios, Yvan J. O.; Sun-Kou, Maria R.
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
658.3208%
Several types of alumina were synthesized from sodium aluminate (NaAlO2) by precipitation with sulfuric acid (H2SO4) and subsequently calcination at 500 degrees C to obtain gamma-Al2O3. The precursor aluminate was derived from aluminum scrap. The various gamma-Al2O3 synthesized were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), adsorption-desorption of N-2 (S-BET) and scanning electron microscopy (SEM). XRD revealed that distinct phases of Al2O3 were formed during thermal treatment. Moreover, it was observed that conditions of synthesis (pH, aging time and temperature) strongly affect the physicochemical properties of the alumina. A high-surface-area alumina (371 m(2) g(-1)) was synthesized under mild conditions, from inexpensive raw materials. These aluminas were tested for the adsorption of Cd(II), Zn(II) and Pb(II) from aqueous solution at toxic metal concentrations, and isotherms were determined. (C) 2012 Elsevier B.V. All rights reserved.; Brazilian National Council for Scientific Development (CNPq)

Uso da voltametria cíclica e da espectroscopia de impedância eletroquímica na determinação da área superficial ativa de eletrodos modificados à base de carbono; Use of cyclic voltammetry and electrochemical impedance spectroscopy for the determination of active surface area of modified carbon-based electrodes

Souza, Leticia Lopes de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/07/2011 PT
Relevância na Pesquisa
773.474%
Eletrodos à base de carbono, como os eletrodos de troca iônica, entre outros, têm aplicação principalmente no tratamento de efluentes industriais e rejeitos radioativos. Carbono é também amplamente utilizado em células a combustível como substrato para os eletrocatalisadores, por possuir elevada área superficial, que supera a sua área geométrica. O conhecimento desta superfície ativa total é importante na determinação das condições de operação de uma célula eletroquímica no que diz respeito às correntes a serem aplicadas (densidade de corrente). No presente estudo foram utilizadas duas técnicas eletroquímicas na determinação da área superficial ativa de eletrodos de carbono vítreo e poroso e eletrodos de troca iônica: espectroscopia de impedância eletroquímica (EIE) e voltametria cíclica (VC). Os experimentos foram realizados com soluções de KNO3 0,1 mol.L-1 em célula eletroquímica de três eletrodos: eletrodo de trabalho à base de carbono, eletrodo auxiliar de platina e eletrodo de referência de Ag/AgCl. Os eletrodos de carbono vítreo e de carbono poroso utilizado possuíam uma área geométrica de 3,14 x 10-2 cm2 e 2,83 10-1 cm2, respectivamente. O eletrodo de troca iônica foi preparado misturando-se grafite...

Estudo de eletrocatalisadores nanoestruturados de Pt/C e Pt-Co/C depositados em carbono de alta área superficial: efeitos morfológicos e composicionais frente à reação de redução de oxigênio; Study of Pt/C and Pt-Co/C electrocatalysts deposited in high surface area carbon: morphological and compositional effects in the oxygen reduction reaction

Nikkuni, Flávio Ryoichi
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 29/07/2013 PT
Relevância na Pesquisa
663.35625%
Neste trabalho a atividade de eletrocatalisadores suportados em carbono de alta área superficial (Vulcan XC-72), Pt/C, Pt3Co/C e PtCo/C frente à reação de redução de oxigênio (RRO) foi correlacionada com as mudanças morfológicas, estruturais e composicionais sofridas em testes de envelhecimento eletroquímico acelerado. Os meios eletrolíticos utilizados foram ácido sulfúrico em várias concentrações e o ionômero/membrana de Nafion®. Os envelhecimentos se basearam em protocolos que consistiram na imposição ao eletrodo de diferentes saltos potenciostáticos ou em manter o seu potencial em um valor com constante. Os saltos potenciostáticos envolveram alternar o potencial do eletrodo a cada 1 minuto, variando entre os valores de 0,9 e 0,1 V vs ERH; 0,9 e 0,6 V vs ERH; 1,05 e 0,10 V vs ERH e 1,05 e 0,65 V vs ERH por 15 horas; No envelhecimento por polarização fixa, o eletrodo foi mantido durante 15 horas, nos seguintes potenciais: 0,9; 0,6 e 0,1 V vs ERH. Após o envelhecimento 0,9 - 0,1 V vs ERH as atividades dos catalisadores Pt-Co/C se mantiveram constantes porém houve uma melhora para o caso da Pt/C. Já para 1,05 - 0,10 V vs ERH também houve uma melhora para Pt/C, enquanto que para os outros catalisadores houve perda de atividade. Para todos os demais protocolos houve perda na atividade catalítica.
Um microscópio eletrônico de transmissão (MET) acoplado a um espectrômetro de energia dispersiva de raios X (X-EDS) foi utilizado para caracterizar os catalisadores novos e envelhecidos. Uma peculiaridade destas medidas é o uso da técnica microscopia eletrônica de transmissão de localidade idêntica (ILTEM)...

Synthesis of silica xerogels with high surface area using acetic acid as catalyst

Arenas, Leliz Ticona; Simm, Carolina Wildner; Gushikem, Yoshitaka; Dias, Silvio Luis Pereira; Moro, Celso Camilo; Costa, Tania Maria Haas; Benvenutti, Edilson Valmir
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
ENG
Relevância na Pesquisa
978.41664%
Nesse trabalho foi estudada a influência do ácido acético na estrutura de poros e na área superficial de sílicas preparadas pelo método sol-gel. Condições experimentais de síntese, tais como temperatura de policondensação e solventes, também foram estudadas. Isotermas de adsorção de N2 das amostras foram classificadas como do tipo 1, típicas de materiais microporosos, o que explica os altos valores de área superficial obtidos. A adição simultânea dos ácidos acético e clorídrico como catalisadores e de acetona como solvente, bem como o emprego de uma temperatura de policondensação de 20 °C, possibilitaram a preparação de sílicas amorfas com valores de área superficial de até 850 m2 g-1. O alto valor de área superficial dessas amostras pode ser explicado principalmente pela microporosidade e também pelo tamanho nanométrico das partículas.; The influence of acetic acid on the pore structure and surface area of silica prepared by the sol-gel method was investigated. Experimental conditions of synthesis, such as gelation temperature and solvents, were also studied. N2 adsorption isotherms of the samples were type 1, typical of microporous materials, explaining the high surface area values (BET) observed. The simultaneous addition of acetic and hydrochloric acids as catalysts and of acetone as solvent...

Synthesis of silica xerogels with high surface area using acetic acid as catalyst

Arenas,Leliz T.; Simm,Carolina W.; Gushikem,Yoshitaka; Dias,Silvio L. P.; Moro,Celso C.; Costa,Tania M. H.; Benvenutti,Edilson V.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2007 EN
Relevância na Pesquisa
976.3385%
The influence of acetic acid on the pore structure and surface area of silica prepared by the sol-gel method was investigated. Experimental conditions of synthesis, such as gelation temperature and solvents, were also studied. N2 adsorption isotherms of the samples were type 1, typical of microporous materials, explaining the high surface area values (BET) observed. The simultaneous addition of acetic and hydrochloric acids as catalysts and of acetone as solvent, together with the use of a gelation temperature of 20 ºC, made it possible to prepare amorphous silica materials with surface area values up to 850 m² g-1. The high surface area value of these samples could be explained by the microporosity and the nanometric size of the particles.

Specific surface area and structures of aluminas from fibrillar pseudoboehmite

Vieira Coelho,A.C.; Rocha,G.A.; Souza Santos,P.; Souza Santos,H.; Kiyohara,P.K.
Fonte: Rede Latino-Americana de Materiais Publicador: Rede Latino-Americana de Materiais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2008 EN
Relevância na Pesquisa
767.117%
By heating powders of the aluminum monohydroxide fibrillar pseudoboehmite from 200ºC to 1400ºC several high surface area aluminas are prepared and characterized by X-ray diffraction and electron optical methods. Aqueous sols with pseudoboehmite fibrils of different lengths were dried by two methods: at room temperature and spray-dried. The following aluminas were obtained after treatment of the powders at increasing temperatures and having a range of specific surface areas: γ-Al2O3 (470ºC - 770ºC; 179 m²/g - 497 m²/g); δ -Al2O3 (770ºC - 930ºC; 156 m²/g - 230 m²/g); θ-Al2O3 (930ºC - 1050ºC; 11 m²/g - 200 m²/g); α-Al2O3 (1050ºC - 1400ºC; 2 m²/g - 17 m²/g). Spray-dried powders, fired at the same temperature than the ground powders, showed higher specific surface areas. The higher surface area alumina have values of the same order of magnitude of the commercial "ad-cat" aluminas.

Preparation and Evaluation of Carbon Coated Alumina as a High Surface Area Packing Material for High Performance Liquid Chromatography

Paek, Changyub; McCormick, Alon V.; Carr, Peter W.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
672.6054%
The retention of polar compounds, the separation of structural isomers and thermal stability make carbonaceous materials very attractive stationary phases for Liquid Chromatography (LC). Carbon clad zirconia (C/ZrO2), one of the most interesting, exhibits unparalleled chemical and thermal stability, but its characteristically low surface area (20 – 30 m2/g) limits broader application as a second dimension separation in two-dimensional liquid chromatography (2DLC) where high retentivity and therefore high stationary phase surface area are required. In this work, we used a high surface area commercial HPLC alumina (153 m2/g) as a support material to develop a carbon phase by chemical vapor deposition (CVD) at elevated temperature using hexane vapor as the carbon source. The loading of carbon was varied by changing the CVD time and temperature, and the carbon coated alumina (C/Al2O3) was characterized both physically and chromatographically. The resulting carbon phases behaved as a reversed phase similar to C/ZrO2. At all carbon loadings, C/Al2O3 closely matched the unique chromatographic selectivity of carbon phases, and as expected the retentivity was increased over C/ZrO2. Excess carbon – the amount equivalent to 5 monolayers - was required to fully cover the oxide support in C/Al2O3...

Solid phase extraction of DNA from biological samples in a post-based, high surface area poly(methyl methacrylate) (PMMA) microdevice

Reedy, Carmen R.; Price, Carol W.; Sniegowski, Jeff; Ferrance, Jerome P.; Begley, Matthew; Landers, James P.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
668.6418%
This work describes the performance of poly(methyl methacrylate) (PMMA) microfluidic DNA purification devices with embedded microfabricated posts, functionalized with chitosan. PMMA is attractive as a substrate for creating high surface area (SA) posts for DNA capture because X-ray lithography can be exploited for extremely reproducible fabrication of high SA structures. However, this advantage is offset by the delicate nature of the posts when attempting bonding to create a closed system, and by the challenge of functionalizing the PMMA surface with a group that invokes DNA binding. Methods are described for covalent functionalization of the post surfaces with chitosan that binds DNA in a pH-dependent manner, as well as for bonding methods that avoid damaging the underlying post structure. A number of geometric posts designs are explored, with the goal of identifying post structures that provide the requisite surface area without a concurrent rise in fluidic resistance that promotes device failure. Initial proof-of-principle is shown by recovery of prepurified human genomic DNA (hgDNA), with real-world utility illustrated by purifying hgDNA from whole blood and demonstrating it to be PCR-amplifiable.

A new synthesis route to high surface area sol gel bioactive glass through alcohol washing: A preliminary study

M. Mukundan, Lakshmi; Nirmal, Remya; Vaikkath, Dhanesh; Nair, Prabha D.
Fonte: Landes Bioscience Publicador: Landes Bioscience
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
664.6709%
Bioactive glass is one of the widely used bone repair material due to its unique properties like osteoconductivity, osteoinductivity and biodegradability. In this study bioactive glass is prepared by the sol gel process and stabilized by a novel method that involves a solvent instead of the conventional calcinations process. This study represents the first attempt to use this method for the stabilization of bioactive glass. The bioactive glass stabilized by this ethanol washing process was characterized for its physicochemical and biomimetic property in comparison with similar composition of calcined bioactive glass. The compositional similarity of the two stabilized glass powders was confirmed by spectroscopic and thermogravimetric analysis. Other physicochemical characterizations together with the cell culture studies with L929 fibroblast cells and bone marrow mesenchymal stem cells proved that the stabilization was achieved with the retention of its inherent bioactive potential. However an increase in the surface area of the glass powder was obtained as a result of this ethanol washing process and this add up to the success of the study. Hence the present study exhibits a promising route for high surface area bioactive glass for increasing biomimicity.

Rapid bench-top fabrication of poly(dimethylsiloxane)/polystyrene microfluidic devices incorporating high-surface-area sensing electrodes

Sonney, Sanjay; Shek, Norman; Moran-Mirabal, Jose M.
Fonte: AIP Publishing LLC Publicador: AIP Publishing LLC
Tipo: Artigo de Revista Científica
Publicado em 13/04/2015 EN
Relevância na Pesquisa
667.87164%
The development of widely applicable point-of-care sensing and diagnostic devices can benefit from simple and inexpensive fabrication techniques that expedite the design, testing, and implementation of lab-on-a-chip devices. In particular, electrodes integrated within microfluidic devices enable the use of electrochemical techniques for the label-free detection of relevant analytes. This work presents a novel, simple, and cost-effective bench-top approach for the integration of high surface area three-dimensional structured electrodes fabricated on polystyrene (PS) within poly(dimethylsiloxane) (PDMS)-based microfluidics. Optimization of PS-PDMS bonding results in integrated devices that perform well under pressure and fluidic flow stress. Furthermore, the fabrication and bonding processes are shown to have no effect on sensing electrode performance. Finally, the on-chip sensing capabilities of a three-electrode electrochemical cell are demonstrated with a model redox compound, where the high surface area structured electrodes exhibit ultra-high sensitivity. We propose that the developed approach can significantly expedite and reduce the cost of fabrication of sensing devices where arrays of functionalized electrodes can be used for point-of-care analysis and diagnostics.

High surface area titanium phosphonate materials with hierarchical porosity for multi-phase adsorption

Ma, T.Y.; Lin, X.Z.; Zhang, X.J.; Yuan, Z.Y.
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
Relevância na Pesquisa
660.3022%
Inorganic–organic hybrid titanium phosphonate materials with a hierarchically-porous structure were synthesized by a mild solvent evaporation strategy using 1-hydroxyethylidene-1,1-diphosphonic acid as an organophosphorus coupling molecule. The preparations were accomplished with the use of triblock copolymers F127 and P123 as structure-directing agents. All the samples possessed a macroporous morphology of the mesoporous framework with a high surface area, and were characterized by SEM, TEM and N2 sorption analysis. The hydroxyethylidene-bridged organophosphonate groups were homogeneously incorporated into the network of the hierarchical porous solid, as revealed by FT-IR, MAS NMR, TGA-DSC and XPS measurements. The hybrid materials were used as adsorbents for the liquid phase adsorption of Cu2+ ions in water and the gas phase adsorption of CO2, showing high adsorption capacity and good reusability, which makes them promising adsorbents for practical applications in environmental remediation.; Tian-Yi Ma, Xiu-Zhen Lin, Xue-Jun Zhang and Zhong-Yong Yuan

A comparison of mucosal surface area and villous histology in small intestines of the brazilian free-tailed bat (Tadarida brasiliensis) and the mouse (Mus musculus)

Zhang, Zhi-Qiang; Brun, Antonio; Price, Edwin R.; Cruz-Neto, Ariovaldo P.; Karasov, William H.; Caviedes-Vidal, Enrique
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica Formato: 102-108
ENG
Relevância na Pesquisa
674.1458%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 2012/04610-5; Studies on birds have led to the hypothesis that increased intestinal absorption between enterocytes (paracellular) evolved as a compensation for smaller intestinal size in fliers, which was perhaps selected to minimize the mass of digesta carried. This hypothesis predicts that bats will also exhibit relatively reduced intestinal size and high paracellular absorption, compared with nonflying mammals. Published studies on three bat species indicate relatively high paracellular absorption. One mechanism for increasing paracellular absorption per cm(2) small intestine (SI) is increased number of tight junctions (TJs) across which paracellular absorption occurs. To our knowledge, we provide the first comparative analysis of enterocyte size and number in flying and nonflying mammals. Intestines of insectivorous bats Tadarida brasiliensis were compared with Mus musculus using hematoxylin and eosin staining method. Bats had shorter and narrower SIs than mice, and after correction for body size difference by normalizing to mass(3/4), the bats had 40% less nominal surface area than the mouse...

Investigation of High Surface Area Artificial Floating Wetlands for Removal of Pollutants in Nutrient-rich Waters

Shane, AMANDA
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
666.6604%
Beneficial management practices for controlling and managing pollutant loadings from entering source waters are essential to preserving the natural habitat of lakes and rivers. Artificial Floating Wetlands (AFWs) are a promising technology, when applied with other beneficial management practices, for the removal of water borne contaminants in urban and agricultural runoff. To evaluate AFWs for their application for nutrient-rich water remediation, a pilot scale study was assessed at the Centre for Alternative Wastewater Treatment in Lindsay Ontario. Fifteen ponds, averaging in size from 7.2 m width to 9.7 m length to 3.8 m depth were divided into two controls and three treatments, each with three replicates. The controls were not covered with AFWs and were used for comparative purposes while the treatments had AFW coverage averaging 67% of the total surface area of each pond. The treatments and controls received varying inputs of simulated stormwater runoff during the study. This study was used to determine the effects of high surface area coverage of AFWs on temperature, pH, DO and ammonia. A lab scale study was designed to investigate the results obtained from the pilot study and to assess the effectiveness of 100% AFW coverage for nutrient-rich water treatment. The study consisted of twelve 150 L containers...

Facile Synthesis of Defective TiO2−x Nanocrystals with High Surface Area and Tailoring Bandgap for Visible-light Photocatalysis

Wajid Shah, Muhammad; Zhu, Yunqing; Fan, Xiaoyun; Zhao, Jie; Li, Yingxuan; Asim, Sumreen; Wang, Chuanyi
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 30/10/2015 EN
Relevância na Pesquisa
660.3022%
A facile hydrothermal approach has been developed to prepare defective TiO2−x nanocrystals using Ti(III)-salt as a precursor and L-ascorbic acid as reductant and structure direction agent. The prepared TiO2−x nanocrystals are composed of a highly crystallized TiO2 core and a disordered TiO2−x outer layer, possessing high surface area, controlled oxygen vacancy concentration and tunable bandgap via simply adjusting the amount of added L-ascorbic acid. The defective TiO2−x shows high photocatalytic efficiency in methylene blue and phenol degradation as well as in hydrogen evolution under visible light, underlining the significance of the present strategy for structural and bandgap manipulation in TiO2-based photocatalysis.

On the Formation and Structure of Nanometric Polyhedral Foams: Toward the Dry Limit

Corkery, Robert W; Fogden, Andrew
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
661.5215%
High surface area, high porosity, nanometric polygonal silica foams with hierarchically connected and uniformly sized pore systems are reported here. We observe a remarkable increase in foam cell sizes from mesoscopic to macroscopic dimensions upon swelli

Templated synthesis of high surface area inorganic oxides by silica aquagel-confined co-precipitation

Marbán Calzón, Gregorio; Fuertes Arias, Antonio Benito; Valdés-Solís Iglesias, Teresa
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 22195 bytes; application/pdf
ENG
Relevância na Pesquisa
663.53516%
8 pages, 7 figures, 2 tables. -- Available online 10 October 2007.; A new and simple synthetic strategy for the preparation of high surface area nanosized metallic oxides using low cost precursors is described in this work. It is based on the coagulation – precipitation processes that occur when the metallic cations of salts dissolved in a silica aquagel medium are forced to precipitate by means of basic reagents. Nanoparticulate aggregates of the metallic oxides can then be obtained by applying the subsequent steps of drying, calcination and silica removal. Here, we illustrate the application of this technique by the preparation of both single and mixed metallic oxides such as copper oxide/ceria, hematite, cobalt ferrite and copper manganese spinel. The materials obtained in this way are made up by aggregates of nanosized particles (2–8 nm) and they exhibit very high surface areas up to 300 m2/g. Depending on the chemical composition of the oxides, different structures ranging from quasi-rounded nanoparticles to aggregates of needle-shaped nanoparticles were obtained.; Funding by Spanish National Project MAT2005-00262 and FICYT Regional Project (IB05-001) is acknowledged. T.V.S. acknowledges the CSIC-ESF for the award of an I3P postdoctoral contract.; Peer reviewed

A highly stable zirconium-based metal-organic framework material with high surface area and gas storage capacities

Gutov, Oleksii V.; Bury, Wojciech; Gomez-Gualdron, Diego A.; Krungleviciute, Vaiva; Fairen-Jimenez, David; Sarjeant, Amy A.; Snurr, Randall Q.; Hupp, Joseph T.; Yildirim, Taner; Farha, Omar K.
Fonte: Wiley Publicador: Wiley
Tipo: Article; accepted version
EN
Relevância na Pesquisa
664.6709%
This is the accepted manuscript. The final version is available as 'Water-Stable Zirconium-Based Metal?Organic Framework Material with High-Surface Area and Gas-Storage Capacities' from Wiley at http://onlinelibrary.wiley.com/doi/10.1002/chem.201402895/abstract.; We designed, synthesized and characterized a new Zr-based metal?organic framework material, NU-1100, which exhibits a pore volume of 1.53 cm3/g and Brunauer-Emmett-Teller (BET) surface area of 4020 m2/g; to our knowledge currently the highest published for Zr-based MOFs. CH4/CO2/H2 adsorption isotherms were measured over a broad range of pressures and temperatures and are in excellent agreement with the computational predictions. The total hydrogen adsorption at 65 bar and 77 K is 0.092 g/g which corresponds to 43 g/L. The volumetric and gravimetric methane storage capacities at 65 bar and 298 K are ~180 vSTP/v and 0.27 g/g, respectively.; OKF, JTH and RQS thank DOE ARPA-E and the Stanford Global Climate and Energy Project for support of work relevant to methane and CO2, respectively. TY acknowledges support by the U. S. Department of Energy through BES Grant No. DE-FG02-08ER46522. WB acknowledges support from the Foundation for Polish Science through the ?Kolumb? Program. DFJ acknowledges the Royal Society (UK) for a University Research Fellowship. This material is based upon work supported by the National Science Foundation (grant CHE-1048773).

Synthesis of mesoporous carbons of high surface area and porosity by using polymer blends as template

Lin, Yu-Chien; Wu, Sheng-Ho; Liu, Che-Wei; Lim, Zheng-Yi; Huang, Cheng-Wei; Lin, Hong-Pin; Deng, Shiensen; Yang, Ming-Chang; Tang, Chih-Yuan; Lin, Ching-Yeh
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
971.7794%
In this paper, we provided a new method to generate the carbonizable polymer-silica nanocomposite in one step by using different polymer blends of phenol formaldehyde (PF) and silica-gelling polymer (i.e., Pluronic F127, PEO6000 or gelatin) as the template. The PF-silica gelling polymer-silica nanocomposite was obtained from fast silicification in a highly diluted silica solution at pH∈≈∈5.0. Because the PF, one kind of carbon sources, was embedded in the as-synthesized nanocomposite, the mesoporous carbon was easily obtained from pyrolysis at 1,000°C and silica removal by diluted HF solution. The resulted mesoporous carbons possess a high surface area of 780-1,500 m2 g-1 and large pore size of 2.6-13.7 nm. In addition, the morphology of the mesoporous carbons can be tailored to nano-sized particles and hollow spheres by using different silica gelator-PF polymer blends. In practice, the electrically conducting mesoporous carbons of high surface area and large pore size can be considered as good material for preparing the supercapacitor. The mesoporous carbons exhibit electric capacity of 75-158 Fg-1 in 2.0 M H2SO4 electrolyte solution at scan rate of 1-50 mVs-1.

Dental occlusal surface area in relation to body mass, food habits and other biological features in fossil xenarthrans

Vizcaíno,Sergio F.; Bargo,M. Susana; Cassini,Guillermo H.
Fonte: Ameghiniana Publicador: Ameghiniana
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2006 EN
Relevância na Pesquisa
660.8882%
The Xenarthra includes the most intriguing mammals from the Cenozoic of South America: the glyptodonts (Cingulata) and the ground sloths (Tardigrada). Their masticatory apparatuses are diverse and peculiar, with a strongly reduced, hypselodont dentition that lacks enamel and displays different degrees of lobation. The goal of this study is to investigate the relationship between dental occlusal surface area (OSA) and diet, and other physiological factors in fossil xenarthrans. Over one hundred and fifty specimens, including living herbivorous epitherians and both extinct and living xenarthrans, were measured and photographed, and their OSA estimated and plotted against body mass. For most fossil xenarthrans OSA is smaller than expected for extant herbivorous mammals of equivalent body size. Within xenarthrans, cingulates show the highest OSA values, suggesting more extensive oral food processing than in tardigrades. Among ground sloths, mylodontids have extremely low OSA values, suggesting low efficiency in oral food processing that was probably compensated by high fermentation in the digestive tract, or lower metabolic requirements, or a combination of both adaptations. On the other hand, Megatherium americanum has an OSA expected for...