Página 1 dos resultados de 61 itens digitais encontrados em 0.011 segundos

Composite electrode of carbon nanotubes and vitreous carbon for electron field emission

MATSUBARA, E. Y.; ROSOLEN, J. M.; SILVA, S. Ravi P.
Fonte: AMER INST PHYSICS Publicador: AMER INST PHYSICS
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
35.95%
In this work, the electron field emission behaviour of electrodes formed by carbon nanotubes (CNTs) grown onto monolithic vitreous carbon (VCarbon) substrates with microcavities is presented. Scanning electron microscopy was used to characterize the microstructure of the films. Tungsten probes, stainless steel sphere, and phosphor electrodes were employed in the electron field emission study. The CNT/VCarbon composite represents a route to inexpensive excellent large area electron emission cathodes with fields as low as 2.1 V mu m(-1). In preliminary lifetime tests for a period of about 24 h at an emission current of about 4 mA cm(-2), there is an onset degradation of the emission current of about 28%, which then stabilizes. Electron emission images of the composites show the cavity of the samples act as separate emission sites and predominantly control the emission process. The emission of CNTs/VCarbon was found to be stable for several hours. (c) 2008 American Institute of Physics.; CAPES[BEX 0278/04-1]; CNPq (Rede de Nanotubos de Carbono, Instituto do Milenio); FAPESP

Eletrorrevestimento de substratos metálicos com tântalo em meio de fluoretos fundidos; caracterização física e eletroquímica dos revestimentos; Electro-coating of metal substrates with tantalum amid molten fluorides; Physical and electrochemical characterization of coatings

Pinto, Denise Villela Barcza Stockler
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 14/08/1998 PT
Relevância na Pesquisa
36.1%
O estudo do eletrorrevestimento de tântalo sobre aço e sobre cobre foi realizado na mistura eutética FLINAK (29,2% LiF - 11,7% NaF - 59,1% KF - % em massa) contendo 15% em massa de K2TaF7. Foram estudadas as influências da densidade de corrente catódica, do tempo de eletrólise, da temperatura e da natureza do substrato sobre as eficiências de correntes catódicas e a morfologia dos revestúnentos. Depósitos de tântalo lisos, brilhantes, aderentes e uniformes foram obtidos com alta eficiência de corrente catódica usando os seguintes parâmetros: densidade de corrente catódica de 23 mA/cm2 a 50 mA/cm2, temperatura de 750°C e tempo de eletrólise de 30 minutos a 120 minutos. Os revestimentos obtidos nestas condições possuem espessuras de 18 µm a 41 µm. Os depósitos de tântalo sobre aço e sobre cobre são constituídos de tântalo puro, sem formação de camada de difusão. Ensaios de eletrodeposição de camadas delgadas de tântalo em catodos de formas e geometrias complexas mostraram o bom poder de cobertura do tântalo. Curvas potencial de circuito aberto x tempo, feitas à temperatura ambiente em soluções de ácido nítrico a 40%, a 50% e a 60% em massa, ácido clorídrico a 3,6% em massa e ácido sulfúrico a 80% em massa...

Propriedades de revestimentos de nióbio obtidos por aspersão térmica a plasma sobre aço API 5L X65

Motta, Felipe Piccinini
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
35.91%
A seleção de revestimentos para aplicação em presença de fluidos altamente corrosivos, condições comumente presentes em tubulações na indústria petroquímica, requer uma rigorosa especificação dos requisitos a serem atendidos. A aplicação de revestimentos de nióbio por aspersão térmica, uma alternativa àquelas realizadas por soldagem e cladeamento (soldagem a frio ou no estado sólido) de chapas de nióbio puro sobre substratos de aço carbono, vem surgindo como fator de interesse pelos pesquisadores, visto que no Brasil situam-se as maiores reservas de nióbio do mundo. O presente trabalho teve por objetivo a obtenção e caracterização de revestimentos de nióbio, aplicados pelo processo de aspersão térmica a plasma sobre o aço API 5L X65. Foi avaliada a influência dos parâmetros operacionais (corrente elétrica e número de passes) sobre as propriedades morfológicas, mecânicas e eletroquímicas dos revestimentos. A preparação superficial do substrato foi realizada com limpeza, pré-aquecimento e jateamento abrasivo com alumina. A morfologia e a microestrutura dos revestimentos foi analisada por microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva (EDS), microscopia ótica...

Highly corrosion resistant siloxane-polymethyl methacrylate hybrid coatings

Hammer, Peter; dos Santos, Fabio C.; Cerrutti, Bianca M.; Pulcinelli, Sandra H.; Santilli, Celso V.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 266-274
ENG
Relevância na Pesquisa
56.14%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Siloxane-polymethyl methacrylate hybrid films were deposited on carbon steel substrates by dip-coating from a sol prepared by acid-catalyzed hydrolytic co-polycondensation of tetraethoxysilane (TEOS) and 3-methacryloxy propyl-trimethoxysilane (MPTS), followed by radical polymerization of methyl methacrylate (MMA). Structural properties of the hybrids were studied using Si-29 and C-13 nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), as a function of the MMA/MPTS ratio, which ranged between 2 and 10. The efficiency of corrosion protection of hybrid-coated carbon steel was investigated by XPS, potentiodynamic polarization curves and electrochemical impedance spectroscopy after immersion of the material in acidic and neutral saline aqueous solution. The NMR and TGA results indicate a high degree of polycondensation (84%) and elevated thermal stability of 410 A degrees C for the hybrid film with a MMA/MPTS ratio of 8, exhibiting also and excellent adhesion to the substrate. The XPS analysis confirmed the variation of the MMA phase in the hybrid...

Carbon nanotube-reinforced siloxane-PMMA hybrid coatings with high corrosion resistance

Hammer, P.; Dos Santos, F. C.; Cerrutti, B. M.; Pulcinelli, S. H.; Santilli, C. V.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 601-608
ENG
Relevância na Pesquisa
76.4%
Siloxane-polymethyl methacrylate hybrid films containing functionalized multiwall carbon nanotubes (CNTs) were deposited by dip-coating on carbon steel substrates from a sol prepared by radical polymerization of methyl methacrylate and 3-methacryloxy propyl-trimethoxysilane, followed by hydrolytic co-polycondensation of tetraethoxysilane. The correlation between the structural properties and corrosion protection efficiency was studied as a function of the molar ratio of nanotubes carbon to silicon, varied in the range between 0.1% and 5%. 29Si nuclear magnetic resonance and thermogravimetric measurements have shown that hybrids containing carbon nanotubes have a similar degree of polycondensation and thermal stability as the undoped matrix and exhibit and excellent adhesion to the substrate. Microscopy and X-ray photoelectron spectroscopy results revealed a very good dispersion of carbon nanotubes in the hybrid matrix and the presence of carboxylic groups allowing covalent bonding with the end-siloxane nodes. Potentiodynamic polarization curves and electrochemical impedance spectroscopy results demonstrate that CNTs containing coatings maintain the excellent corrosion protection efficiency of the hybrids, showing even a superior performance in acidic solution. The nanocomposite structure acts as efficient corrosion barrier...

Desenvolvimento de sistemas multifuncionais baseados em híbridos orgânico-inorgânicos dopados

Santos, Fábio Cesar dos
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: 69 f. : il.
POR
Relevância na Pesquisa
35.97%
Pós-graduação em Química - IQ; Environmentally compliant organic-inorganic hybrid coatings for efficient corrosion protection of metallic surfaces are alternatives to the current methods based on chromate passivation. In this context hybrids coatings were prepared using the sol-gel process from the radical polymerization of methyl methacrylate (MMA) and 3-(Trimethoxysilyl)propyl methacrylate (MPTS) followed by the step of acidic hydrolysis and polycondensation of the silanes tetraethoxysilane (TEOS) and 3-(Trimethoxysilyl)propyl methacrylate (MPTS). To investigate the effectiveness of the hydrolysis/polycondensation process and the resulting structural properties, coatings were prepared with different ethanol to water proportions (0 < Ethanol/H2O < 1) for constant organic to inorganic phase ratio (MMA/TEOS = 4). The structural properties of ~2 μm thick films, deposited onto carbon steel substrates by dip-coating, were correlated with their anti corrosion efficiency. Nuclear magnetic resonance, X-ray photoelectron spectroscopy, thermogravimetry and nanoscratch test were used to study the structural properties and adhesion on steel. Electrochemical impedance spectroscopy and potentiodynamic polarization curves were carried out to evaluate the corrosion resistance of the coated samples after long-term exposure in standard saline (3...

Adherent diamond-like carbon coatings on metals via PECVD and IBAD

Capote,Gil; Bonetti,Luís F.; Santos,Lúcia V.; Trava-Airoldi,Vladimir J.; Corat,Evaldo J.
Fonte: Sociedade Brasileira de Física Publicador: Sociedade Brasileira de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2006 EN
Relevância na Pesquisa
45.97%
Adherent and low-stress a-C:H films were deposited on Ti6Al4V and stainless steel substrates using PECVD and IBAD techniques. An amorphous silicon interlayer was applied to improve the adhesion of the a-C:H films on the metal substrates. The XPS technique was employed to analyze the chemical bondings within the interfaces. The elemental composition and atomic density of the films were determined by ion beam analysis. The film microstructure was studied by means of Raman scattering spectroscopy. The mechanical properties were determined by means of stress and hardness measurements. The adherence was evaluated by means of scratch tests. The tests showed that the composition, the microstructure, and the mechanical properties of the films depend on the intensity of the ion bombardment and on the ion current.

XPS, XRD and laser raman analysis of surface modified of 6150 steel substrates for the deposition of thick and adherent diamond-like carbon coatings

Silva,William de Melo; Carneiro,José Rubens Gonçalves; Trava-Airoldi,Vladimir Jesus
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2013 EN
Relevância na Pesquisa
46.18%
Although the 6150 steel has an excellent fatigue and impact resistance, it is unsuitable to operate it when the corrosion is a limited factor. We propose here a sequence of steel pre-treatment by carburizing, carbonitriding and nitriding in order to improve the poor adhesion between Diamond Like-Carbon coatings on steel. This sequence is our attempt to reduce the difference between the coefficients of thermal expansion of steel and DLC through the graded interface. This work demonstrates the quantitative analysis of the molecules present at surface using X-ray photoelectron spectroscopy. The crystallographic structures are investigated by X-ray diffraction which shows the formation of carbides and nitride phases. Raman spectroscopy reveals the carburizing surface characteristics where DLC coating is nucleated and grown at the substrate. At the end of the analysis it is possible to verify which molecules and phases are formed on the steel surface interface after each step of pre-treatment.

Abrasive blasting contamination in Super Duplex and carbon steels - a quantification approach by rietveld analysis

Rocha,Adriana da Cunha; Nascimento,Áquila Vieira do; Margarit-Mattos,Isabel Cristina Pereira; Assis,Kioshy dos Santos; Mattos,Oscar Rosa
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2014 EN
Relevância na Pesquisa
56.49%
A methodology for quantifying the contamination after abrasive blasting by Aluminum Oxide and Martensitic Carbon Steel particles in Super Duplex and Carbon Steel substrates has been developed. The method consisted of performing x-ray diffraction in the blasted steel substrates and calculating the particle contamination using Rietveld Quantitative Method. In this way, it is possible to evaluate the substrate volume in which the abrasive particles have been trapped (taking into account the surface roughness) rather than solely performing visual examination, as indicated by standards documents. Equations describing the intensity model of the diffracted peaks as well as those describing the quantitative measurements are presented. Correction functions are also employed to compensate the effect of the surface roughness generated on the metallic substrates after blasting. Alumina and martensitic steel abrasives contaminations were detected and quantified in both steel substrates. Results showed that Super Duplex Steel substrates revealed a higher degree of contamination when compared to the Carbon Steel substrates, both for alumina abrasives as for martensitic abrasives. Also, the abrasive that generated the lower degree of contamination was the Martensitic Carbon Steel...

Corrosion Behavior of Coarse- and Fine-Grain Ni Coatings Incorporating NaH2PO4.H2O Inhibitor Treated Substrates

Ul-Hamid,Anwar; Quddus,Abdul; Saricimen,Huseyin; Dafalla,Hatim
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2015 EN
Relevância na Pesquisa
45.94%
Plain carbon steel substrates were treated with NaH2PO4.H2O inhibitor for 24 hours and coated with Ni using dc and pulse electrodeposition in standard Watt’s bath. The effect of dc and pulse electrodeposition, on the microstructure and corrosion properties of Ni coatings in 3.5 wt% NaCl solution was studied. The effect of inhibitor on the deposition process and corrosion behavior was also examined. Materials characterization was performed using field emission scanning electron microscopy, cross-sectional scanning transmission electron microscopy, atomic force microscopy, x-ray diffraction and nanoindentation. Experimental results indicated that pulse electrodeposition produced fine grained Ni coatings that showed lower corrosion rate compared to coarse grained dc electrodeposited Ni. Pre-treatment of substrates with inhibitor did not adversely affect the deposition process and adherent Ni coatings were readily developed. The results showed that pulse electrodeposition could be used to produce hard corrosion resistant Ni coatings while the inhibitor treatment yielded enhanced corrosion protection by providing a protective buffer layer between the Ni coating and the substrate.

Biodiesel compatibility with carbon steel and hdpe parts

Maru, Marcia Marie; Lucchese, Márcia Maria; Legnani, Cristiano; Quirino, Welber Gianini; Balbo, Andrea; Aranha, Isabele Bulhões; Costa, Lilian Terezinha; Vilani, Cecília; Sena, Lídia Ágata de; Damasceno, Jailton Carreteiro; Cruz, Talita dos Santos; L
Fonte: Inmetro - Instituto Nacional de Metrologia, Qualidade e Tecnologia Publicador: Inmetro - Instituto Nacional de Metrologia, Qualidade e Tecnologia
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.09%
8 p.: il., tab.; Compatibility of the new environmentally-friendly alternative of diesel engine fuels, biodiesel, with storage and engine part materials, is still an open issue. In this work, the interaction between three fuels (petroleum diesel and two types of biodiesel — soybean and sunflower) and two materials (carbon steel and high density polyethylene) used in storage and automotive tanks, is analyzed in detail. A wide set of characterization techniques was used to evaluate the changes in both solid and fluid materials, as weight change measurement, optical, scanning electron and atomic force (AFM) microscopies, Raman and FTIR spectroscopies, and differential scanning calorimetry. The AFM technique allowed detecting surface roughness and morphology changes in the metallic material following the trends in the weight losses. In the case of polymeric material, weight gain by fluid absorption occurred, being detected by the spectroscopic techniques. The biodiesel fuels underwent some ageing however this phenomenon did not affect the interaction between the biodiesel fuels and the substrates. The petrodiesel, which did not age, caused more significant degradation of the substrates.

Synthesis and Electron Emission Properties of Aligned Carbon Nanotube Arrays

Neupane, Suman
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Relevância na Pesquisa
36.16%
Carbon nanotubes (CNTs) have become one of the most interesting allotropes of carbon due to their intriguing mechanical, electrical, thermal and optical properties. The synthesis and electron emission properties of CNT arrays have been investigated in this work. Vertically aligned CNTs of different densities were synthesized on copper substrate with catalyst dots patterned by nanosphere lithography. The CNTs synthesized with catalyst dots patterned by spheres of 500 nm diameter exhibited the best electron emission properties with the lowest turn-on/threshold electric fields and the highest field enhancement factor. Furthermore, CNTs were treated with NH3 plasma for various durations and the optimum enhancement was obtained for a plasma treatment of 1.0 min. CNT point emitters were also synthesized on a flat-tip or a sharp-tip to understand the effect of emitter geometry on the electron emission. The experimental results show that electron emission can be enhanced by decreasing the screening effect of the electric field by neighboring CNTs. In another part of the dissertation, vertically aligned CNTs were synthesized on stainless steel (SS) substrates with and without chemical etching or catalyst deposition. The density and length of CNTs were determined by synthesis time. For a prolonged growth time...

Coefficient of friction measured from nano- to macro-normal loads on plasma sprayed nanostructured cermet coatings

Basak, A.; Celis, J.P.; Vardavoulias, M.; Matteazzi, P.
Fonte: ASM International Publicador: ASM International
Tipo: Artigo de Revista Científica
Publicado em //2014 EN
Relevância na Pesquisa
35.79%
Alumina dispersed FeCuAl-based nanostructured cermet coatings were deposited from nanostructured powders by atmospheric plasma spraying on low carbon steel substrates. Nanostructuring was retained in the deposited coatings which exhibit up to four distinctive phases as revealed by electron microscopy. In this study, the friction behavior of the distinctive phases at nano-normal load scale was investigated alongside their contribution to the overall friction behavior at macro-normal load scale. Friction behavior at nano-normal load scale was investigated by lateral force microscopy, whereas conventional tribometers were used for investigations at micro and macro-normal loads. It appeared that, the friction measured at nano-normal loads on individual phases is dictated by both composition and hardness of the corresponding phases, and thus influences the overall friction behavior of the coatings at macro-normal loads. Moreover, the coefficient of friction at macro-normal loads differs from the one at nano-normal loads, and deviates from Amonton’s friction law.; A. K. Basak, J.-P. Celis, M. Vardavoulias, and P. Matteazzi

Structure and mechanical properties of low temperature magnetron sputtered nanocrystalline (nc-)Ti(N,C)/amorphous diamond like carbon (a-DLC) coatings

TSOTOS C.; BAKER M.a.; POLYCHRONOPOULOU K.; GIBSON Peter; GIANNAKOPOULOS K.; POLYCARPOU A.; BOBEL K.; REBHOLZ C.
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Articles in Journals Formato: Printed
ENG
Relevância na Pesquisa
35.95%
This paper reports on the structure and mechanical properties of ~ 2 µm thick nanocrystalline (nc-) Ti(N,C)/ amorphous (a-) diamond like carbon (DLC) coatings deposited on 100Cr6 steel substrates, using low temperature (~ 200 oC) DC reactive magnetron sputtering. The carbon content was varied with acetylene partial pressure in order to obtain single layer coatings with different a-DLC carbon phase fractions. The nanocrystalline Ti(N,C) phase is approximately stoichiometric for all coatings and the DLC phase fraction increases from 31 ¿ 47 at. % as the coatings stoichiometry changed from TiC1.34N0.51 to TiC2.48N0.48, respectively. TiC1.34N0.51 coatings showed the highest nano-indentation hardness (H) of ~14 GPa and a modulus (Er) of ~144 GPa; H reduced to < 6 GPa and Er to < 70 GPa for TiC2.48N0.48 coatings. Nc-Ti(N,C)/a-DLC coatings are promising candidates for applications where better matching of the modulus between relatively low modulus substrate, hard loading support layer and low modulus-high H/E ratio top layer is required.; JRC.I.4-Nanobiosciences

Influence of high frequency and moderate energy pulses on DLC deposition onto metallic substrates by magnetron sputtering technique

Oliveira,R. M.; Hoshida,L.; Ueda,M.; Baba,K.
Fonte: Sociedade Brasileira de Física Publicador: Sociedade Brasileira de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2009 EN
Relevância na Pesquisa
35.97%
The deposition of Diamond-like carbon (DLC) films brings excellent mechanical, chemical, optical and electronic properties to a large range of materials. However, a problem to be overcome is its poor adhesion on metallic substrates. Usually, a silicon layer must be deposited on the surface of metals previous to DLC film deposition. In fact, in our experiments using conventional Magnetron Sputtering (MS) technique for deposition of DLC film on metal surfaces (AISI 304 stainless steel, Al 2024, Ti-6Al-4V), the silicon interlayer was crucial to avoid delamination. However, a combined process using MS and high frequency and moderate energy pulses (2.5kV/6µs/1.25 kHz), was successful to grow DLC film without the interlayer. Additionally, by monitoring the stress and the thickness in silicon samples after the processes, it was possible to correlate the conditions of operation with such characteristics. Stress measurements carried out by a profilometer and calculated by Stoney's equation varied from 2 GPa to 10.5 GPa depending on the conditions of operation of the process (pressure, distance source-substrate, frequency, length and intensity of the pulse). The thickness, the composition, the structure and the morphology of DLC coatings deposited in such metallic surfaces were obtained. Tribological and corrosion tests were also performed.

Electrodos modificados y sus aplicaciones en electrocatálisis; Nanostructured films and electrodes and their applications in electrocatalysis

Völker, Edgar
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: info:eu-repo/semantics/doctoralThesis; tesis doctoral; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2013 SPA
Relevância na Pesquisa
36.25%
La investigación básica y aplicada en electrodos funcionalizados ha ido incrementándose en los últimos 30 años debido a su diversidad de aplicaciones en catálisis, óptica, electrónica, protección contra la corrosión, etc. Existen diversas maneras en las cuales se puede modificar un electrodo, ya sea por deposición de películas por spin o dip coating, adsorción de monocapas autoensambladas, drop casting, autoensamblado capa‐por‐capa, etc. En esta tesis estudiamos la modificación química controlada de superficies de electrodos y sus aplicaciones en reacciones electrocatalíticas y redox. Materiales diversos como Au, Cu, aleaciones Au‐Cu, polioxomolibdatos y polímeros redox fueron utilizados como electrodos funcionalizados. Estos materiales fueron caracterizados exhaustivamente y se estudiaron sus aplicaciones en reacciones electrocatalíticas de importancia en medio ambiente (reducción de CO2, nitritos, cloratos y peroxodisulfatos), así como también en reacciones redox. Durante esta tesis se desarrolló un nuevo método para la síntesis de nanoaleaciones Au‐Cu soportadas en negro de carbón. La síntesis produce nanopartículas aleadas, estables y robustas. Las nanopartículas Au‐Cu fueron caracterizadas por espectroscopía UV‐visible...

Single- and few-layer graphene growth on stainless steel substrates by direct thermal chemical vapor deposition

John, Robin; Ashokreddy, A; Vijayan, C; Pradeep, T
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.97%
Steeping interest on graphene research in basic sciences and applications emphasizes the need for an economical means of synthesizing it. We report a method for the synthesis of graphene on commercially available stainless steel foils using direct thermal chemical vapor deposition. Our method of synthesis and the use of relatively cheap precursors such as ethanol (CH3CH2OH) as a source of carbon and SS 304 as the substrate, proved to be economically viable. Presence of single- and few-layer graphene was confirmed using confocal Raman microscopy/spectroscopy. X-ray photoelectron spectroscopic measurements were further used to establish the influence of various elemental species present in stainless steel on graphene growth. Role of cooling rate on surface migration of certain chemical species (oxides of Fe, Cr and Mn) that promote or hinder the growth of graphene is probed. Such analysis of the chemical species present on the surface can be promising for graphene based catalytic research.

Diamond-Like Carbon film from Liquid Gas on Metallic Substrates

Vesaghi, M. A.; Shafiekhani, A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/01/1998
Relevância na Pesquisa
35.89%
Liquid gas was used to produce DLC films on Cu, Al and steel substrates by DC plasma technique. The absorption in IR reflectance indicates, grown films are DLC. By deconvolution of room temperature UV-visible spectra of the films grown at 50 mtorr and 200${}^\circ$C, in addition to the spectra lines reported for CL, PL, PLC and ESR, some new spectra lines were obtained. We also, have seen exciton absorption line at room temperature.; Comment: 6 pages, Postscript, 2 figures

Electrophoretic mobilities of dissolved polyelectrolyte charging agent and suspended non-colloidal titanium during electrophoretic deposition

Lau, Kok-Tee; Sorrell, C. C.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/09/2013
Relevância na Pesquisa
35.79%
Coarse (<=20 micron) titanium particles were deposited on low-carbon steel substrates by cathodic electrophoretic deposition (EPD) with ethanol as suspension medium and poly(diallyldimethylammonium chloride) (PDADMAC) as polymeric charging agent. The preceding data demonstrated that Ti particles of ~1-12 micron size, electrosterically modified by the PDADMAC charging agent, acted effectively as colloidal particles during EPD. Owing to the non-colloidal nature of the particles and the stabilization of the Ti particles by electrosteric forces, the relevance of the zeta potential is questionable, so the more fundamental parameter of electrophoretic mobility was used. A key finding from the present work is the importance of assessing the electrophoretic mobilities of both the suspensions and solutions since the latter, which normally is overlooked, plays a critical role in the ability to interpret the results meaningfully. Further, algebraic uncoupling of these data plus determination of the deposit yield as a function of charging agent addition allow discrimination between the three main mechanistic stages of the electrokinetics of the process, which are: (1) surface saturation; (2) compression of the diffuse layer, growth of polymer-rich layer...

Morphology and Corrosion Performance of Chromate Conversion Coatings on Different Substrates

Domínguez-Crespo,Miguel Antonio; Onofre-Bustamante,Edgar; Torres-Huerta,Aidé Minerva; Rodríguez-Gómez,Francisco J.
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2008 EN
Relevância na Pesquisa
46.05%
The aqueous corrosion resistances of galvalume (Fe-Al+Zn) and steel galvanized (Fe-Zn) alloys, passivated by immersion in chromating solution with different immersion times (0, 10, 30 y 60 s) are compared. The electrochemical behaviour of various chromated and non-chromated coatings was investigated in 3 wt-% NaCl solution using polarization techniques. For comparison, AISI 1010 carbon steel substrates were also analyzed. The characterization measurements and polarization curves revealed that textural properties of Fe alloys influence the growth of the films and both the cathodic and anodic reactions. An optimum anticorrosive protection was obtained at 30 s. CCCs treatments inhibited the corrosion of zinc to a significant degree, but less effectively than coatings formed with aluminium-zinc alloys. The difference in the corrosion protection given by the two substrates types was attributed to the structural properties, thickness coating, grain size and roughness observed, which affect oxygen diffusion.