Production and characterization of ZrCN-Ag coatings deposited by mganetron sputtering

Tese de Doutoramento (Programa doutoral em Engenharia de Materiais)Zr-C-N coatings, incorporating silver as antibacterial agent, are deposited onto stainless steel 316L (SS316L) and Si (100) substrates by unbalanced magnetron sputtering; their corrosion and tribological properties were evaluated to understand their potential to be used in joint orthopedic devices. Zirconium carbonitride was selected owing to both its excellent biocompatibility and non-toxic behavior. Despite ZrCN has been widely studied, no other report on the deposition and characterization of Zr-C-N-Ag coatings exist in the literature, to the author knowledge. Therefore, the contribution of this project for the state of the art on Zr-C-N system alloyed novel metallic elements is: (i) A structural characterization, including the phase composition, based on the identification of crystalline (X-ray diffraction and transmission electron microscopy) and amorphous phases (Raman spectroscopy), and the chemical composition of the material both in bulk (electron probe microanalysis) and at the surface (X-ray photonelectron spectroscopy). The morphology of the coatings was also studied (scanning electron microscopy), in order to evidence the influence of the deposition parameters on the coatings cross-section and surface morphology, and correlate them with the functional properties. (ii) In order to optimize the adhesion, mechanical and electrochemical properties of the coatings; an optimization method was applied to the deposition process to decrease the final number of coating runs. (iii) The in-depth electrochemical and tribological characterization of the coatings was performed in a Hank’s balanced salt solution with 10 gr/L of bovine serum albumin, in order to mimic as much as possible the condition of the biological fluid of human body. In Zr-C-N-Ag system a diversity of phases can occur, such as zirconium carbonitride (ZrCN), amorphous carbon (a-C or a-(C, N)) and metallic silver (Ag). By controlling the deposition conditions, it is possible to adjust the amount of each phase, and then, to tune the properties of the system. The optimization of the deposition process shows that the ideal composition of the Zr-C-N-Ag coatings is attained when the Zr2CN phase is deposited, with less than 8 at. % of silver nanoparticles, allowing achieving the best compromise between mechanical, electrochemical and tribological properties. The electrochemical evaluation reveals that both silver and amorphous carbon phases are detrimental to the corrosion resistance. The increase of silver triggers a more active electrochemical reactions in the system that increases the corrosion process. In addition, the combination of silver and amorphous phases produces a more electrochemical porous materials, which promotes the penetration of the electrolyte. Although marginally, silver also negatively affects the wear resistance of the system, when tested against an ultra-high molecular weight polyethylene, due to a delay it causes in the formation of a protective albumin layer. The coefficient of friction (COF) of the coatings, did not show any correlation with the amount of silver, while the amorphous carbon phases seems to reduce the COF. Finally, the phase distribution showed a relevant role in the silver ion release to the electrolyte, as a function of the silver nanoparticles surrounding. This distribution of phases creates nanogalvanic couples in the system that controls the silver ion release, depending on a:C or ZrCN phases, the oxidation of silver can be enhanced or retarded, respectively. The antibacterial effect of the system does not have a direct relation with the silver ion release. Even coatings with low silver ion release may possess antibacterial capabilities, if silver is highly agglomerated on the surface.Neste trabalho foram depositados revestimentos do sistema Zr-C-N-Ag, incorporando a prata como um agente antibactericida, em substratos de aço inoxidável 316L e silício (100), utlizando a técnica de pulverização catódica por magnetrão. Os revestimentos foram caraterizados no que concerne o seu comportamento tribológico e à corrosão, no sentido de compreender o seu potencial para serem utilizados em próteses ortopédicas. O zircónio foi selecionado por causa da sua biocompatibilidade e comportamento não tóxico. Ao conhecimento do autor, apesar do sistema ZrCN ter sido amplamente estudado, não existe na literatura qualquer referência à investigação deste sistema incorporando prata. Assim, a contribuição deste trabalho para o estado da arte dos revestimentos Zr-C-N com adições de outros elementos é: (i) Caraterização estrutural, incluindo a análise da composição fásica, baseada quer na identificação das fases cristalinas (difração de raios X e microscopia eletrónica de transmissão) e amorfas (espectroscopia Raman) quer na avaliação da composição química dos revestimentos, no maciço (microssonda eletrónica) e na superfície (espectroscopia de fotoeletrões de raios X). A morfologia dos revestimentos em superfície e secção transversal foi analisada por microscopia eletrónica de varrimento, pondo em evidência a influência dos parâmteros de deposição na rugosidade e compacidade dos revestimentos. (ii) De modo a otimizar a adesão e as propriedades mecânicas e eletroquímicas dos revestimentos, um método de otimização foi aplicado ao processo de deposição para diminuir o número total de experiências. (iii) A caraterização eletroquímica e tribológica dos revestimentos foi realizada numa solução salina balanceada com 10 gr/L de albumina sérica bovina de modo a mimetizar as condições dos fluidos biológicos caraterísticos do corpo humano. Podem occorrer no Sistema Zr-C-N-Ag diversas fases, tais como os carbonitretos de zircónio (ZrCN), carbono amorfo (a-C or a-(C, N)) e prata metálica (Ag). Controlando as condições de deposição, é possível ajustar a quantidade de cada uma das fases e, então, alcançar as propriedades desejadas. A otimização do processo de deposição mostra que a composição ideal para os revestimentos de Zr-C-N-Ag é atingida quando é depositada a fase Zr2CN, com menos de 8 % at. de nanopartículas de prata, permitindo encontrar o melhor compromisso entre propriedades mecânicas, eletroquímicas e tribológicas. A caraterização eletroquímica permitiu concluir que ambas as fases de prata e de carbono amorfo são prejudiciais para a resistência à corrosão. Adicionalmente, a prata tem uma ação negativa na resistência ao desgaste do sistema, quando os testes são realizados contra um contracorpo de polietileno de alta densidade de elevado peso molecular, devido ao atraso que ela provoca na formação no contato da camada protetora de albumina. Finalmente, a distribuição de fases tem um papel relevante na libertação de iões de prata para o eletrólito, dependente da vizinhança que têm as nanopartículas de prata. Dependendo de haver a fase de carbono amorfo ou de ZrCN, a oxidação da prata pode ser, respetivamente, realçada ou retardada. O efeito antibactericida do sistema não tem uma relação direta com a libertação dos iões de prata. Mesmo revestimentos com libertação de iões de Ag reduzida podem possuir capacidades antimicrobianas, se houver suficiente teor de prata aglomerada na superfície.This thesis was financially supported by a PhD scholarship from Fundação para a Ciência e Tecnologia (Ref.: SFRH/BD/80947/2011), inserted in the Programa Potencial Humano Quadro de Referência Estratégico Nacional (POPH - QREN) Tipologia 4.1 – Formação Avançada. The POPH-QREN is co-financed by Fundo Social Europeu (FSE) and by Ministério da Ciência, Tecnologia e Ensino Superior (MCTES)

Ag+ release and corrosion behavior of zirconium carbonitride coatings with silver nanoparticles for biomedical devices

Zirconium carbonitride coatings with silver nanoparticles were produced by DC unbalanced dual magnetron sputtering system, using two targets, Zr and Zr/Ag in an Ar, C2H2 and N2 atmosphere. Stainless steel 316L and silicon (100) substrates were used for electrochemical and structural characterization, respectively. Silver was found to be well distributed throughout the coatings, maintaining the films' composition in depth, while its diffusion to the electrolyte decreases as immersion time increases, stopping its release after 7 to 8 days of immersion. Electrochemical characterization revealed very stable films that have improved base material, without any diminished corrosion resistance due to the silver content.The authors are grateful to 3B's Research Group in Biomaterials, Biodegradables and Biomimetics for the ICP measurements and Prof. Isabel Leonor, PhD for her assistance. This research is partially sponsored by FEDER funds through the program COMPETE-Programa Operacional Factores de Competitividade and by Portuguese national funds through FCT-Fundacao para a Ciencia e a Tecnologia, under the project ANTIMICROBCOAT-PTDC/CTM/102853/2008. This work has also been supported by the Ministerio de Ciencia e Innovacion of Spain through the Consolider-Ingenio 2010 program (CSD2008-00023) and through the project RyC2007-0026

Nano-galvanic coupling for enhanced Ag+ release in ZrCN-Ag films: antibacterial application

The antibacterial properties of materials developed for medical devices with embedded silver nanoparticles are enhanced by controlling the release of silver ions. In this study, a simple experimental procedure for the augmentation of the silver ion release from ZrCN-Ag coatings is described. The silver nanoparticles are embedded in an amorphous carbon matrix within the ZrCN coatings, to create nano-galvanic couples between the silver and the carbon phases. The galvanic couple promotes the oxidation of silver, and consequently, increases the silver release. It is demonstrated that coatings with a lower silver content, but integrating amorphous carbon phases, can release similar or even a larger amount of Ag+ ions than those with higher Ag content having just ZrCN and Ag phases. The antibacterial tests demonstrate that coatings with silver nanoparticles encapsulated into amorphous phase reveal a larger bacterial zone of inhibition compared to samples with similar or lower silver content. However, it is shown that the antibacterial effect of the coatings not only depends on the ability for silver ion release, but also on the availability of silver nanoparticles on the surface.This research is partially sponsored by FEDER funds through the program COMPETE - Programa Operacional Factores de Competitividade and by Portuguese national funds through FCT-Fundacao para a Ciencia e a Tecnologia, under the projects ANTIMICROBCOAT - PTDC/CTM/102853/2008 and in the framework of the Strategic Projects PEST-C/ FIS/UI607/2011", UID/EMS/00285/2013 and SFRH/BD/80947/2011

Surface characterization of Ti-Si-C-ON coatings for orthopedic devices : XPS and Raman spectroscopy

Ti–Si–C–ON films were deposited by DC reactive magnetron sputtering and their chemical properties, biofilm formation and toxicity were characterized. Based on the films composition three different growth regimes were identified on the films; (I) N/Ti = 2.11 (high atomic ratio) and low oxygen content; (II) 0.77 ≤ N/Ti ≤ 1.86 (intermediate atomic ratio) and (III) N/Ti ≤ 0.12 (low ratio) and high oxygen content. The phase composition varied from mainly TiN on regime I to TiCN on regime 2 and titanium oxides on regime III. Taking into account the results of biological characterization (biofilm formation and cytotoxicity), it was possible to conclude that samples with a high TiN content (regime I) presented more favorable biocompatibility, since it was less prone to microbial colonization and also displayed a low cytotoxicity.The authors are grateful to Dr. Alicia Andres, Institut de Ciencia de Materiales de Madrid (ICMM-CSIC), for his assistance in carrying out the Raman spectroscopic analysis. The work was financially supported by the CRUP Institution (project "Accao No E-1007/08), and the Spanish Ministry of Science and Innovation (projects FUN-COAT CSD2008-00023, MAT2008-06618-C02 and Integrated action HP016-2007). This research is partially sponsored by FEDER funds through the program COMPETE- Programa Operacional Factores de Competitividade and by Portuguese national funds through FCT-Fundacao para a Ciencia e a Tecnologia, under the project PTDC/CTM/102853/2008

Structure-property relations in ZrCN coatings for tribologic applications

ZrCN coatings were deposited by dc reactive magnetron sputtering with N2 flows ranging from 2 to 10 sccm in order to investigate the influence of the nitrogen incorporation on structure and properties. Information about the chemical composition was obtained by glow discharge optical emission spectroscopy and Rutherford backscattering spectroscopy. The evolution of the crystal structure studied by X-ray diffraction revealed the formation of a face-centred cubic ZrCN phase for N2 flows greater than 4 sccm. Additionally, the presence of an amorphous phase in the coatings deposited with the highest N2 flows could be evidenced by Raman spectroscopy and X-ray photoelectron spectroscopy. This phase can act as a lubricant resulting in a low coefficient of friction as shown in the conducted ball-on-disc tests. Nanoindentation measurements showed that coatings deposited with a 6 sccm N2 flow had the maximum hardness which also revealed the best performance in the conducted dry cutting tests.CRUP InstitutionSpanish Ministry of Science and InnovationChristian Doppler Research Associatio

Atomic electrostatic maps of point defects in MoS2

In this study, we use differential phase contrast images obtained by scanning transmission electron microscopy combined with computer simulations to map the atomic electrostatic fields of MoS2 monolayers and investigate the effect of sulphur monovacancies and divancancies on the atomic electric field and total charge distribution. A significant redistribution of the electric field in the regions containing defects is observed, with a progressive decrease in the strength of the projected electric field for each sulphur atom removed from its position. The electric field strength at the sulphur monovacancy sites is reduced by approximately 50% and nearly vanishes at the divacancy sites, where it drops to around 15% of the original value, demonstrating the tendency of these defects to attract positively charged ions or particles. In addition, the absence of the sulphur atoms leads to an inversion in the polarity of the total charge distribution in these regions.The authors would like to acknowledge that this project has received funding from the EU Framework Program for Research and Innovation H2020, Scheme COFUND-Cofunding of Regional, National and International Programs, under grant agreement no. 713640. This work was supported by FCT, through IDMEC, under LAETA, project no. UIDB/50022/2020. R.M.R. acknowledges the FCT grant UIDB/FIS/04650/2020-2023. D.A. acknowledges the Presidential Early Career Award for Scientists and Engineers (PECASE) through the Army Research Office (W911NF-16-1-0277) and a National Science Foundation grant (ECCS-1809017). R.M.R. acknowledges support by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020

Silver activation effect in the antibacterial activity in multifunctional coatings

With the increase of life expectancy, hip joint prosthesis is being widely used worldwide, with concerns about the quality of life of patients and costs involved in the chirurgical procedures. Staphylococcus epidermidis have emerged as one of the major nosocomial pathogens associated with microbial infections, one of the major causes of the failure of medical devices, that can happen at the time of the chirurgical procedure or subsequently. In order to minimize this drawback, the introduction of multifunctional coatings in the biomaterial could be a step to improve their physical, mechanical, tribological and biological properties and consequently avoid the revision surgeries by microbial infection. Plasma Vapor Deposition (PVD) is a powerful technique disseminated today, used in order to make thin films in many substrates. The main goal of this work was to produce multifunctional Ag-ZrCN for antimicrobial coatings for hip prostheses. Metallic silver (content up to 11 at. %) in ZrCN matrix, was deposited onto stainless steel 316L, by DC reactive magnetron sputtering. In spite silver historic performance in medicine due his potent antibacterial effect, Ag-ZrCN does not show antibacterial effect, since silver is present on its metallic form. Indeed antibacterial activity depends of the released Ag+ from metallic silver. Therefore, the proposed challenge of this work is to enhance the silver ionization, in order to achieve their release to the biological environment and promote its action on microorganisms, preventing its development. Silver antibacterial activity of these coatings was achieved by an activation procedure, by immersion of the samples in a 5% (w/v) NaClO solution for 5 minutes. After the activation, there are significant changes in the Ag 3d XPS spectra. The peak related to Ag-clusters simply disappears and a new peak shifted to lower energies arises, which can be attributed to silver oxides. In fact, the formation of oxidized nano silver based material can inhibit bacterial growth since its bioavailability allows improve biocidal Ag+ formation and mobility, providing a constant concentration of Ag+ ions in aqueous environments. Samples were tested using the halo method, using S. epidermidis. In close contact with medium humidity, Ag+ spontaneously diffuses over the surrounding aqueous medium (bacteria suspension and agar) killing or inhibiting bacteria growth and a Zone of Inhibition was disclosed

Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles can providemultiple benefits for biomedical applications in aqueous environments such asmagnetic separation or magnetic resonance imaging. To increase the colloidal stability and allow subsequent reactions, the introduction of hydrophilic functional groups onto the particles’ surface is essential. During this process, the original coating is exchanged by preferably covalently bonded ligands such as trialkoxysilanes. The duration of the silane exchange reaction, which commonly takes more than 24 h, is an important drawback for this approach. In this paper, we present a novel method, which introduces ultrasonication as an energy source to dramatically accelerate this process, resulting in high-quality waterdispersible nanoparticles around 10 nmin size. To prove the generic character, different functional groups were introduced on the surface including polyethylene glycol chains, carboxylic acid, amine, and thiol groups. Their colloidal stability in various aqueous buffer solutions as well as human plasma and serum was investigated to allow implementation in biomedical and sensing applications.status: publishe

Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV

Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

Penilaian Kinerja Keuangan Koperasi di Kabupaten Pelalawan

This paper describe development and financial performance of cooperative in District Pelalawan among 2007 - 2008. Studies on primary and secondary cooperative in 12 sub-districts. Method in this stady use performance measuring of productivity, efficiency, growth, liquidity, and solvability of cooperative. Productivity of cooperative in Pelalawan was highly but efficiency still low. Profit and income were highly, even liquidity of cooperative very high, and solvability was good