Ciencias
URI permanente para esta comunidadhttps://hdl.handle.net/11441/10802
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Examinando Ciencias por Autor "Abad, Manuel D."
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Artículo Extended X-ray absorption fine structure (EXAFS) investigations of Ti bonding environment in sputter-deposited nanocomposite TiBC/a-C thin films(Institute of Physics Publishing, 2014) Endrino, José Luis; Abad, Manuel D.; Gago, Raúl; Horwat, D.; Jiménez, I.; Sánchez López, Juan Carlos; Ministerio de Educación y Ciencia (MEC). España; European Union (UE)In this study, we have successfully used the extended X-ray absorption fine structure (EXAFS) technique at the Ti-K edge to extract the local structure in a set of nanocomposite TiBC/a-C coatings deposited by a combined d.c.-pulsed and r.f.-magnetron sputtering deposition process. The sequence of Fourier transform spectra in the deposited films shows that there is an increase in the number of Ti-C bonds in the films of higher carbon content in parallel with the increment of the total carbon content. In addition, Ti-K EXAFS spectra indicate that in all the deposited TiBC/a-C films, first-shell neighbours are in a nearer structural arrangement than the one expected for a bulk hexagonal TiB2, which could be due to the formation of mixed Ti-B-C compound in a structural unit similar to the one found in h-TiB2.Artículo Influence of silver content on the tribomechanical behavior on Ag-TiCN bioactive coatings(Elsevier, 2012) Sánchez López, Juan Carlos; Abad, Manuel D.; Carvalho, I; Escobar-Galindo, Ramón; Benito, N; Ribeiro, S; Henriques, M.; Cavaleiro, A.; Carvalho, S.urface modification of bulk materials used in biomedical applications has become an important prerequisite for better biocompatibility. In particular, to overcome the particle generation, low-wear coatings based on carbon (nitrogen) and containing antimicrobial elements such as silver are promising candidates. Thus, the present work explores the potentialities of silver-containing carbonitride-based (Ag-TiCN) thin films prepared by direct current unbalanced reactive magnetron sputtering. The silver content in the coatings was varied from 0 to 26.7 at.% by changing the targets and the fraction of C2H2 and N2 in the gas mixture with Ar. The obtained Ag-TiCN based coatings were characterized in terms of composition and microstructure. Mechanical and tribological properties of the films were studied by nanoindentation and reciprocating pin-on disk testing in a fetal bovine serum solution, respectively. Raman, scanning electron microscope and energy dispersive X-ray analysis was carried out in the contact region after tribological tests to obtain information about the friction mechanism. The cytotoxicity of the coatings was assessed by in vitro tests using fibroblast cells. The coatings comprised a mixture of TiCxN1 − x, Ag and a-C(N)x phases whose relative proportion varied depending on the Ag/Ti ratio. The mechanical, tribological and cytotoxicity properties were correlated with the chemical and phase composition. When the Ag/Ti ratios were below 0.20 (Ag contents < 6.3 at.%) the films resulted harder (~ 18 GPa) with higher wear resistance (~ 10−6 mm3/Nm), showing similar friction coefficient (~ 0.3) and good biocompatibility.Artículo Tribocorrosion behaviour of TiBxCy/a-C nanocomposite coating in strong oxidant disinfectant solutions(Elsevier, 2015) Gracia Escosa, Elena; García, Ignacio M.; Sánchez Lora, Juan Carlos; Abad, Manuel D.; Mariscal, A; Arenas, M. A; Damborenea, Juan de; Conde Amiano, Alejandro; Universidad de Sevilla. Departamento de Física de la Materia CondensadaCorrosion and tribocorrosion studies of a TiBxCy/a-C coating deposited on AISI 316L steel have been performed in an aqueous solution of 0.26 vol.% acetic, 0.16 vol.% peracetic and 0.18 vol.% hydrogen peroxide (commercial product Oxonia 1 vol.%). The corrosion current density of the TiBxCy/a-C coating ranges on the same order as bare steel but with a significantly decreasing friction (0.1 vs. 0.6) and wear rate (~ 10 times lower). The compact microstructure of the coating hinders the access of the aggressive electrolyte to the substrate, preventing the onset of the corrosion attack, while maintaining an excellent tribological behavior in strong oxidant solutions.Artículo Tribological comparison of different C-based coatings in lubricated and unlubricated conditions(Elsevier, 2014) Ciarsolo, I; Fernández, X; Ruíz de Gopegui, U.; Zubizarreta, C.; Abad, Manuel D.; Mariscal, A.; Caretti, Ignacio; Jiménez, I; Sánchez López, Juan Carlos; Ministerio de Educación y Ciencia (MEC). EspañaThe use of carbon-based coatings (hydrogenated and non-hydrogenated DLC, doped and alloyed-DLC) is of wide interest due to its applications in mechanical components submitted to friction and wear including sliding parts in automotive engines. A tribological comparative analysis using a reciprocating (SRV) tester in lubricated and unlubricated conditions with a 4-stroke motor oil has been carried out on six currently relevant state-of-the-art coatings (namely WC/a-C, TiBC/a-C and TiC/a-C:H nanocomposites, Ti-doped DLC, BCN film and a crystalline monolithic TiC film as reference). The quantification of the fraction of the sp2-bonded matrix has been done by fitting of C 1s XPS peak and the mechanical properties evaluated by nanoindentation. The comparative analysis has allowed us to identify the capabilities of each system depending on the testing conditions and the possible synergies as a function of the chemical composition and film nature. Under lubricated harsh conditions (max. contact pressure 1.7 GPa) only coatings displaying hardness superior to 20 GPa could stand the sliding motion without failure. At lower contact pressures, a significant fraction of sp2 carbon (≥ 75%) is advantageous for reducing wear in boundary lubrication. WC/a-C, BCN and Ti-DLC films showed the best tribological response in dry sliding conditions. This fundamental information would be of relevance for assisting engineers in selecting best partnership for lubrication systems