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High temperature tests on partially encased beams

Piloto, P.A.G.; Gavilán, Ana; Mesquita, L.M.R.; Gonçalves, Carlos
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
26.51%
Partially encased beams (PEB) are composite steel and concrete elements that present several advantages with respect to steel bare elements. This paper presents a set of experimental tests developed using two different beam lengths and two different shear conditions between stirrups and web (W – welded and NW – not welded), at high temperature (200, 400, 600 ºC) and room temperature. The composite section was built-up with IPE100 steel profile and reinforced concrete between flanges. The deformed shape mode and the bending resistance were compared for different temperature levels and stirrup shear conditions (W and NW). The behaviour of PEB was also compared with bare steel at room temperature. Most of the beams attained the ultimate limit state by lateral torsional buckling (LTB), with exception for those tested at 600 ºC, which collapsed by the formation of a plastic hinge (PH).

Experimental tests of partially encased beams at elevated and room temperature

Piloto, P.A.G.; Gavilán, Ana; Mesquita, L.M.R.; Barreira, Luísa; Gonçalves, Carlos
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
POR
Relevância na Pesquisa
26.61%
This work presents the experimental tests developed on partially encased beams (PEB) at elevated temperature and room temperature. PEB were built with IPE100 steel profile. Two beam lengths were tested (2.5 and 4 m) at room, 400 and 600 ºC. Seven series were tested to compare the performance of PEB using two different stirrups shear conditions (welded -W and not welded to web - NW). The behaviour of IPE 100 PEB was also compared with IPE 100 bare steel beam at room temperature. Most of the beams attained the ultimate limit state by lateral torsional buckling (LTB), with exception for those tested at 600 ºC which collapsed by the formation of a plastic hinge (PH). The performance of each PEB was characterized based on some load events. The load value for plastic behaviour (FMpl), the load value for displacement equal to L/30 (FL/30) and the load value for the ultimate load (Fu). The bending strength of the PEB at room temperature is almost two times the bending resistance of bare steel beam. The reduction on bending resistance of PEB is not directly proportional to the increase of temperature. An increase of temperature from room to 400ºC and to 600ºC leads to a reduction of 37 % and 64% on FL/30, respectively. The ultimate load of PEB increased 85% in comparison with bare steel at room temperature. A decrease in the ultimate load of 24% and 22% was verified when temperature increased from room to 400 ºC and from 400 ºC to 600 ºC...

Experimental tests of partially encased beams at elevated and room temperature

Piloto, P.A.G.; Gavilán, Ana; Mesquita, L.M.R.; Barreira, Luísa; Gonçalves, Carlos
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
26.61%
This work presents the experimental tests developed on partially encased beams (PEB) at elevated temperature and room temperature. PEB were built with IPE100 steel profile. Two beam lengths were tested (2.5 and 4 m) at room, 400 and 600 ºC. Seven series were tested to compare the performance of PEB using two different stirrups shear conditions (welded -W and not welded to web - NW). The behaviour of IPE 100 PEB was also compared with IPE 100 bare steel beam at room temperature. Most of the beams attained the ultimate limit state by lateral torsional buckling (LTB), with exception for those tested at 600 ºC which collapsed by the formation of a plastic hinge (PH). The performance of each PEB was characterized based on some load events. The load value for plastic behaviour (FMpl), the load value for displacement equal to L/30 (FL/30) and the load value for the ultimate load (Fu). The bending strength of the PEB at room temperature is almost two times the bending resistance of bare steel beam. The reduction on bending resistance of PEB is not directly proportional to the increase of temperature. An increase of temperature from room to 400ºC and to 600ºC leads to a reduction of 37 % and 64% on FL/30, respectively. The ultimate load of PEB increased 85% in comparison with bare steel at room temperature. A decrease in the ultimate load of 24% and 22% was verified when temperature increased from room to 400 ºC and from 400 ºC to 600 ºC...

High temperature tests on partially encased beams

Piloto, P.A.G.; Gavilán, Ana B. R.; Mesquita, L.M.R.; Gonçalves, Carlos
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
POR
Relevância na Pesquisa
26.51%
Partially encased beams (PEB) are composite steel and concrete elements that present several advantages with respect to steel bare elements. This paper presents a set of experimental tests developed using two different beam lengths and two different shear conditions between stirrups and web (W – welded and NW – not welded), at high temperature (200, 400, 600 ºC) and room temperature. The composite section was built-up with IPE100 steel profile and reinforced concrete between flanges. The deformed shape mode and the bending resistance were compared for different temperature levels and stirrup shear conditions (W and NW). The behaviour of PEB was also compared with bare steel at room temperature. Most of the beams attained the ultimate limit state by lateral torsional buckling (LTB), with exception for those tested at 600 ºC, which collapsed by the formation of a plastic hinge (PH).

Buckling of steel and composite steel and concrete columns in case of fire

Correia, Antonio M.; Rodrigues, João Paulo C.
Fonte: Federal University of Rio de Janeiro; State University of Rio de Janeiro Publicador: Federal University of Rio de Janeiro; State University of Rio de Janeiro
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
46.63%
Bare steel columns are known to have a very low fire resistance. The high thermal conductivity and the sudden decrease of the steel yield stress and Young Modulus in function of the temperature are responsible for this behaviour. The purpose of this study is to compare different modes of failure of building steel columns. The buckling of the columns is strongly influenced by the contact with other elements such as brick walls. Three types of situations were compared: steel columns embedded on brick walls, bare steel columns and composite columns made of partially encased steel sections. The deformed shapes of the columns are analyzed in this work.

Fire Resistance of Steel and Composite Steel-Concrete Columns

Correia, António José Pedroso de Moura
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
36.76%
O fogo é uma acção extrema a que uma estrutura pode ser sujeita, e portanto deve ser dimensionada para lhe resistir. Os Eurocódigos estruturais disponibilizam métodos de cálculo para permitirem garantir às estruturas a resistência ao fogo adequada. O objectivo deste trabalho foi estudar pilares de aço e mistos aço-betão em edifícios, em situação de incêndio. A influência de diversos parâmetros, tais como o contacto com as paredes de tijolo, a rigidez da estrutura circundante, o nível de carregamento, e a esbelteza do pilar, foram alvo de um estudo paramétrico realizado experimental e numericamente no presente trabalho. Resultados dos ensaios experimentais foram comparados com os estudos numéricos reproduzindo as condições usadas nos ensaios experimentais, com a finalidade de fornecer dados valiosos para o desenvolvimento ou melhoria de métodos de dimensionamento de pilares em situação de incêndio. O principal objectivo foi reproduzir, tanto quanto possível, em laboratório, as condições a que opilar está sujeito, num edifício real em incêndio. O programa experimental comportou a realização de ensaios em pilares de aço de secção H embebidos em paredes, pilares de aço e mistos aço-betão parcialmente preenchidos com betão com dilatação térmica restringida. Os ensaios experimentais referenciados foram realizados na Universidade de Coimbra. Os resultados foram comparados com os de ensaios realizados no Bundesanstaltfür Material-forschungund- prüfung (BAM)...

Composite connections in slim-floor system: An experimental study

Nardin, Silvana de; El Debs, Ana Lucia Homce de Cresce
Fonte: ELSEVIER SCI LTD; OXFORD Publicador: ELSEVIER SCI LTD; OXFORD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
26.51%
This paper reports the results of full-scale tests in beam-to-column connections for composite slim floor systems, including tests on Bare Steel connection and composite connection. The tested system consists of a concrete-filled composite column and a composite floor where an asymmetric steel beam is connected to a composite column by shear steel plates. Tests results previously obtained on partially encased composite beams were used to define the position of the headed studs in the slim floor system. Based on the obtained results of connections, the composite and Bare Steel connection behaved as semi-rigid and nominally pinned respectively. The tests results also indicated a significant contribution of the slim floor to the moment capacity of the connection. (C) 2011 Elsevier Ltd. All rights reserved.; Fapesp - Research Support Foundation of Sao Paulo State; FAPESP (Sao Paulo State Foundation of Research Support)

Ligações mistas viga-pilar - análise teórica e experimental ; Composite beam-column connection – Theoretical and experimental analysis

Figueiredo, Luciana Maria Bonvino
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 19/08/2004 PT
Relevância na Pesquisa
36.4%
Uma ligação em estruturas de aço é denominada mista quando considera-se a contribuição da laje no seu comportamento. Assim, além do detalhe da ligação em aço, outros parâmetros interferem no comportamento da ligação mista, como a taxa de armadura e o nível de interação entre a laje e a viga de aço. Os métodos de cálculo de ligações mistas derivam do Método dos Componentes proposto pelo Eurocode 3 para cálculo de ligações em aço. Apresenta-se uma adaptação de um destes métodos para cálculo de ligações mistas que representam a realidade brasileira em termos de perfis e detalhes de ligação. Foi elaborado um programa experimental de caráter exploratório envolvendo ligações mistas com chapa de topo estendida. Foram ensaiados modelos simulando pilares internos e pilares de canto. Um modelo numérico foi desenvolvido utilizando o programa Ansys, que permite a análise destas ligações de maneira simples e satisfatória. Os resultados experimentais foram confrontados com os resultados da análise numérica e com os valores obtidos a partir do modelo analítico.; A composite joint is a joint between a composite beam and a steel or composite column in which reinforced concrete slab is take into account. The moment-rotation relationship of composite joints depends on a significant number of parameters besides the type and configuration of the steel connection...

"Caracterização do comportamento frente à corrosão de um aço inoxidável austenítico para aplicações biomédicas com revestimentos PVD de TiN, TiCN e DLC" ; CHARACTERIZATION OF THE CORROSION BEHAVIOR OF AN AUSTENITIC STAINLESS STEEL FOR BIOMEDICAL APPLICATIONS COATED WITH TiN, TiCN AND DLC PVD COATINGS

Antunes, Renato Altobelli
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 15/12/2006 PT
Relevância na Pesquisa
36.44%
Biomateriais metálicos devem apresentar uma combinação de propriedades como resistência à corrosão, biocompatibilidade e resistência mecânica. Os aços inoxidáveis austeníticos, especialmente do tipo AISI 316L, aliam estas propriedades com a possibilidade de fabricação a um baixo custo. No entanto, são susceptíveis à corrosão nos fluidos fisiológicos e seus produtos de corrosão podem causar reações alérgicas ou infecciosas nos tecidos vizinhos ao implante. No presente trabalho, a aplicação de revestimentos obtidos por processos de deposição física de vapor (PVD) sobre um aço inoxidável austenítico do tipo AISI 316L foi realizada a fim de aumentar sua resistência à corrosão e biocompatibilidade. Os filmes depositados foram de nitreto de titânio (TiN), carbonitreto de titânio (TiCN) e de carbono tipo diamante (DLC). Estes materiais têm alta dureza e resistência ao desgaste, além de biocompatibilidade intrínseca, características altamente desejáveis para aplicações biomédicas. A caracterização do comportamento eletroquímico do aço com os três tipos de revestimentos mostrou que a presença de defeitos na superfície das camadas depositadas exerce uma influência negativa sobre a resistência à corrosão do substrato. A presença dos defeitos foi evidenciada por microscopia eletrônica de varredura. Foi proposto um mecanismo...

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
26.31%
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...

Corrosion protection of stainless steel by polysiloxane hybrid coatings prepared using the sol-gel process

Sarmento, V. H. V.; Schiavetto, M. G.; Hammer, P.; Benedetti, A. V.; Fugivara, C. S.; Suegama, P. H.; Pulcinelli, S. H.; Santilli, C. V.
Fonte: Elsevier B.V. Sa Publicador: Elsevier B.V. Sa
Tipo: Artigo de Revista Científica Formato: 2689-2701
ENG
Relevância na Pesquisa
36.35%
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); Polysiloxane hybrid films were deposited on 316 L stainless steel substrates by dip-coating in a sol prepared by acid-catalyzed hydrolytic co-polycondensation of tetraethoxysilane (TEOS) and 3-methacryloxy propyltrimethoxysilane (MPTS), followed by radical polymerization of methacrylic moieties. Structural features of the polysiloxane hybrids were studied using (13)C and (29)Si nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), as a function of the TEOS/MPTS ratio, which ranged between 0 and 2. The efficiency of corrosion protection of hybrid-coated stainless steel was investigated by X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) after immersion of the material in acidic and neutral saline aqueous solutions. The NMR and TGA results indicated a high degree of polymerization and polycondensation (85%) for the hybrid film with a TEOS/MPTS ratio of 2, as well as elevated thermal stability of 410 C and excellent adhesion. The XPS analysis confirmed the hybridized structure of the polysiloxane network...

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
46.55%
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...

Tribological behaviour of CVD diamond films on steel substrates

F. J. G. Silva; A. J. S. Fernandes; F. M. Costa; V. Teixeira; A. P. M. Baptista; E. Pereira
Fonte: Universidade do Porto Publicador: Universidade do Porto
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
36.26%
Diamond films have been prepared by microwave plasma chemical vapour deposition (MPCVD) on high-speed steel substrates pre-coated with an intermediate metal multi-layer system. Wear tests were performed in a micro-abrasion apparatus by rotating ball, using a slurry of diamond abrasive particles in water (sphere-on-flat geometry). The tests were carried out on the bare steel substrate, on the substrate provided with the multi-layered system and, finally, on the diamond-coated samples. The worn surfaces were characterised by scanning electron microscopy (SEM) and micro-Raman spectroscopy, in order to identify the wear mechanisms involved. Wear data are compared and discussed. CVD diamond films have revealed an excellent performance for medium film thickness and moderate normal loads.

Performance evaluation of retrofitting strategies for non-seismically designed RC buildings using steel braces

Varum, H.; Teixeira-Dias, F.; Marques, P.; Pinto, A.; Bhatti, A.
Fonte: Springer Verlag Publicador: Springer Verlag
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.31%
Recent major earthquakes around the world have evidenced that research in earthquake engineering must be directed to the vulnerability assessment of existing constructions lacking appropriate seismic resisting characteristics. Their retrofit or replacement should be made in order to reduce vulnerability, and consequent risk, to currently accepted levels. In this work, the efficiency of ductile steel eccentrically-braced systems in the seismic retrofitting of existing reinforced concrete (RC) buildings is studied. The retrofit technique studied consists in a bracing system with an energy dissipation device, designed to dissipate energy by shear deformation. The numerical model was calibrated with cyclic test results on a full-scale structure. The models used for the RC frame and masonry represent their real behavior and influence in the global structural response. The steel bracing system was modeled with strut rigid elements. The model for the energy dissipater device reproduces rigorously the behavior of the shear-link observed in the cyclic tests, namely in terms of shear, drift and energy dissipation. With the calibrated numerical model, a series of non-linear dynamic analyses were performed, for different earthquake input motions...

Clinical utility of platinum chromium bare-metal stents in coronary heart disease

Jorge, Claudia; Dubois, Christophe
Fonte: Dove Medical Press Publicador: Dove Medical Press
Tipo: Artigo de Revista Científica
Publicado em 27/08/2015 EN
Relevância na Pesquisa
26.46%
Coronary stents represent a key development for the treatment of obstructive coronary artery disease since the introduction of percutaneous coronary intervention. While drug-eluting stents gained wide acceptance in contemporary percutaneous coronary intervention practice, further developments in bare-metal stents remain crucial for patients who are not candidates for drug-eluting stents, or to improve metallic platforms for drug elution. Initially, stent platforms used biologically inert stainless steel, restricting stent performance due to limitations in flexibility and strut thickness. Later, cobalt chromium stent alloys outperformed steel as the material of choice for stents, allowing latest generation stents to be designed with significantly thinner struts, while maintaining corrosion resistance and radial strength. Most recently, the introduction of the platinum chromium alloy refined stent architecture with thin struts, high radial strength, conformability, and improved radiopacity. This review will provide an overview of the novel platinum chromium bare-metal stent platforms available for coronary intervention. Mechanical properties, clinical utility, and device limitations will be summarized and put into perspective.

Corrosion mitigation of buried structures by soils modification [Mitigación de la corrosión de estructuras enterradas mediante la modificación de suelos]

Cordoba V.C.; Mejia M.A.; Echeverria F.; Morales M.; Calderon J.A.
Fonte: Universidade de Medellín Publicador: Universidade de Medellín
Tipo: Article; info:eu-repo/semantics/article
ENG
Relevância na Pesquisa
36.38%
Carbon steel samples were buried in loamy soil modified with lime, fly-ash and Portland cement in ratio of 5 and 10% during 60 days. Corrosion attack was assessed by electrochemical impedance spectroscopy. Loamy soil without modification was taken as reference. The corrosion products in rust were characterized by Raman spectroscopy. It was found that soil with fly-ash and Portland cement can develop corrosion protection to bare steel due to the changing of formed rust on steel samples. Lepidocrocite and Goethite were found as major constituents in formed rust on buried steel in soil modified with fly-ash and cement, while Magnetite was found in formed rust on buried steel in soil without addition of cementitious materials and modified with lime. According to the electrochemical results, the soil with 5% of fly-ash exhibited the anticorrosive best performance.

Extremely durable biofouling-resistant metallic surfaces based on electrodeposited nanoporous tungstite films on steel

Tesler, Alexander B.; Kim, Philseok; Kolle, Stefan; Howell, Caitlin; Ahanotu, Onye; Aizenberg, Joanna
Fonte: Nature Pub. Group Publicador: Nature Pub. Group
Tipo: Artigo de Revista Científica
Publicado em 20/10/2015 EN
Relevância na Pesquisa
36.26%
Formation of unwanted deposits on steels during their interaction with liquids is an inherent problem that often leads to corrosion, biofouling and results in reduction in durability and function. Here we report a new route to form anti-fouling steel surfaces by electrodeposition of nanoporous tungsten oxide (TO) films. TO-modified steels are as mechanically durable as bare steel and highly tolerant to compressive and tensile stresses due to chemical bonding to the substrate and island-like morphology. When inherently superhydrophilic TO coatings are converted to superhydrophobic, they remain non-wetting even after impingement with yttria-stabilized-zirconia particles, or exposure to ultraviolet light and extreme temperatures. Upon lubrication, these surfaces display omniphobicity against highly contaminating media retaining hitherto unseen mechanical durability. To illustrate the applicability of such a durable coating in biofouling conditions, we modified naval construction steels and surgical instruments and demonstrated significantly reduced marine algal film adhesion, Escherichia coli attachment and blood staining.

The effect of heat treatments and coatings on the outgassing rate of stainless steel chambers

Mamun, M. A.; Elmustafa, A. A.; Stutzman, M. L.; Adderley, P. A.; Poelker, M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.31%
The outgassing rates of three nominally identical 304L stainless steel vacuum chambers were measured to determine the effect of chamber coatings and heat treatments. One chamber was coated with titanium nitride (TiN) and one with amorphous silicon (a-Si) immediately following fabrication. The last chamber was first tested without any coating, and then coated with a-Si following a series of heat treatments. The outgassing rate of each chamber was measured at room temperatures between 15 and 30 {\deg}C following bakes at temperatures between 90 and 400 {\deg}C. Measurements for bare steel showed a significant reduction in the outgassing rate by nearly a factor of 20 after a 400 {\deg}C heat treatment (3.5x10-12 Torr L s-1 cm-2 prior to heat treatment, reduced to 1.7x10-13 Torr L s-1 cm-2 following heat treatment). The chambers that were coated with a-Si showed minimal change in outgassing rates with heat treatment, though an outgassing rate reduced by heat treatments prior to a-Si coating was successfully preserved throughout a series of bakes. The TiN coated chamber exhibited remarkably low outgassing rates, up to four orders of magnitude lower than the uncoated stainless steel, but the uncertainty in these rates is large due to the sensitivity limitations of the spinning rotor gauge accumulation measurement and the possibility of a small pump speed due to inhomogeneity in the TiN coating. The outgassing results are discussed in terms of diffusion-limited versus recombination-limited processes.; Comment: 9 figures...

Catalytic growth of carbon nanotubes on stainless steel: Characterization and frictional properties

Abad, Manuel D.; Sánchez López, Juan Carlos; Berenguer Murcia, A.; Golovko, V. B.; Cantoro, M.; Wheatley, Andrew E.H.; Fernández-Camacho, A.; Johnson, B. F. G.; Robertson, J.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 22195 bytes; application/pdf
ENG
Relevância na Pesquisa
36.4%
5 pp. Published in Diamond and Related Materials Copyright © 2008 Elsevier B.V.; Carbon nanotubes (CNTs) have been grown both on a sample of stainless steel (317-2R) and on the same steel coated with cobalt colloid nanoparticles. Both materials are suitable supports for the growth of vertically aligned carbon nanotubes, although a more sparse growth of significantly thicker carbon nanotubes is observed in the case of the bare steel. We find that carbon nanotubes grown directly on the stainless steel support show very poor tribological behaviour whereas the support using nanoparticles for carbon nanotube growth displayed interesting tribological properties with friction coefficients of approximately 0.1–0.2. The modified CNT material (studied by Raman spectroscopy) adheres to both mating surfaces avoiding direct contact between asperities and plough so the friction and wear processes decrease greatly.; The authors would like to thank Dr. Frederic Mirabella (ArcelorMittal Steel) for kindly supplying the steel supports and for useful discussions. A.B.M. thanks the Spanish Ministry of Education for a Post-Doctoral Research Fellowship. Funding from projects NOE EXCELL NMP3-CT-2005-515703 (EU), MAT2004-01052 (Spanish MEC) and 2007GB0014 (CSIC-The Royal Society) is also acknowledged.; Peer reviewed

Tribological properties of Bi xTi yOz films grown via RF sputtering on 316L steel substrates

Parra,Johanna; Piamba,Oscar; Olaya,Jhon; Alfonso,José Edgar
Fonte: DYNA Publicador: DYNA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2015 EN
Relevância na Pesquisa
36.31%
In this paper, we present the results obtained in surface chemical analysis, morphological characterization and evaluation of tribological properties of coatings of amorphous bismuth titanate (Bi xTi yOz) deposited on substrates made of 316L stainless steel using rf sputtering technique. The chemical elemental analysis was performed using Auger electron spectroscopy (AES), the morphology of the coatings was determined by atomic force microscopy (AFM). Measures of friction coefficient and wear rate were obtained by ball on disc test. EEA analyses allowed to establish that the first 10 nm of the coatings are comprised probably of Bi4Ti3O12 and Ti2O3, AFM measurements indicate that the coatings have an average roughness of 22.28nm and grain size of 50nm. Finally, the tribological tests established that the coefficient of friction and wear rate of the coated steel has similar values to the bare steel.