Failure modes observed on worn surfaces of W-C-Co sputtered coatings

During scratch testing, the indenter gives rise to a distribution of stresses similar to that observed in tribocontacts. In this work, rJ.- sputtered W-C-Co coatings deposited from sintered WC + Co (6,10 and 15 Wl.% Co) at various substrate biases were scratched and tested tribologically and the morphology of the damaged surfaces was analysed. The cobalt content of the coatings is the main factor determining their tribological characteristics. The failure modes observed on the worn pin-on-disc tested surfares are explained and compared with those obtained by scratch testing. In spite of it not being possible to establish quantitative results for the wear resistance ofW-C-Co coatings from scratch testing, an estimation can be performed based on the observation ofthe failure modes in the scratch track. Thus scratch testing can i:>eused to predict the tribological behaviour of coated surfaces. This possibility can reduce the number and cost of tribological tests

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

Effect of the microstructure on the cutting performance of superhard (Ti, Si, Al)N nanocomposite films

A d.c. reactive magnetron sputtering technique was used to deposit (Ti,Si,Al)N coatings onto WC–Co cutting tools. The microstructure of the coatings was analysed using X-ray diffraction (XRD) and highresolution transmission electron microscopy (HRTEM) measurement. Before the cutting experiments, the XRD results revealed a structure indexed to an fcc TiN. The results obtained by the XRD tests, with detector variation in asymmetric mode (rocking curves) showed a decrease in the quality of the fiber texture in the (111) grains with the change on deposition chamber geometry (two magnetrons in place of four magnetrons). Cross-sectional HRTEM images of the (Ti,Al)N sample showed grains with a diameter between 16 and 30 nm, while for the (Ti,Si,Al)N samples grains with a diameter between 6 and 10 nm were observed. Furthermore, through the visualization of bright field images it was possible to discern a columnar structure. For samples prepared at high deposition rates (2 mm/h), HRTEM micrographs revealed the formation of the multilayer stacking of (Ti,Si)N/(Ti,Al)N

An experimental and theoretical study on the crystal structure and elastic properties of Ta1-xOx coatings

The production of Ta1-xOx coatings has attracted a lot of attention due to their wide variety of industrial applications. Nonetheless, to properly control the functional properties of these coatings, a good understanding of their structural properties must be achieved. Ta1-xOx phases have structural similarities since they are formed by the distortion of the body centered cubic (bcc) Ta structure and, therefore, a clear and unequivocal identification of the crystalline phases is not trivial. In this regard, this work proposes a theoretical and experimental study to understand the evolution of the structural and the elastic properties of Ta-based coatings. The coatings were deposited by magnetron sputtering as a function of oxygen content and characterized by EPMA (electron probe microanalysis), XRD (X-ray diffraction), STEM (scanning transmission electron microscopy) and SAW (surface acoustic waves). The results demonstrate the formation of a bcc alpha-Ta phase in the non-reactive Ta coating, which transitions to a mixture of crystalline tantalum and tantalum oxide phases for low oxygen concentrations while amorphous phases are observed for high oxygen levels. Ab-initio calculations of different Ta-O phases are in good agreement with the experimental results and reveal that the oxygen addition to the metallic Ta phase, leads to a distortion of the Ta crystal structure, causing a decrease in density and an increase of the elastic constants.- This research is sponsored by FEDER funds through the program COMPETE -Programa Operacional Factores de Competitividade and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013, and UID/EMS/00285/2013 and with a PhD fellowship SFRH/BD/98199/2013. The authors also thank the financial support in the framework of ERA-SIINN/0004/2013 and PTDC/CTM-NAN/4242/2014 projects

Reactor para síntese química com aquecimento óhmico, método e suas aplicações

O presente invento refere-se a um reactor com aquecimento óhmico para síntese química. Este método de aquecimento tem aplicação desde a síntese orgânica à inorgânica, preparação de materiais organo-metálicos, síntese de nanopartículas e de polímeros. a presente invenção diminui o consumo de energia e aumenta o rendimento das reacções de síntese química, por meio de um reactor para síntese química, e respectivo método, o qual compreende: - um depósito para os reagentes (1), o qual contém pelo menos uma tubuladura lateral (1a); - uma tampa (3), esta tampa deverá ser de preferência resistente a ataques químicos e a solventes orgânicos; - dois eléctrodos (3a,3b) para produzir aquecimento óhmico do meio reaccional, configurados para produzir uma corrente eléctrica com frequência superior a 15 khz. O presente invento é aplicável, na indústria química e na indústria farmacêutica em particular em processos de síntese química

Anaerobic co-digestion of cork based oil sorbent and cow manure or sludge

Cork, a material with great economic, social and environmental importance in Portugal, is also a good oil sorbent that can be used in the remediation of oil spills. The oil-impregnated cork can be easily removed, but requires further treatment. In the case of vegetable oil spills, anaerobic digestion may be a potential solution. This study aims to evaluate the effect of adding cork contaminated with sunflower oil as co-substrate in anaerobic digestion processes. Biodegradability assays were prepared with cow manure or sludge from a wastewater treatment plant, in the presence of five concentrations of oil-contaminated cork, between 200 and 1000 mg· L-1 as COD. Maximum cumulative methane production increased with the amount of oily cork up to 41 % and 101 % in the assays with manure and sludge, respectively. Sporadic addition of cork contaminated with vegetable oil during anaerobic digestion of manure or sludge increases significantly the methane production of these processes.Programa Operacional Regional do Norte (ON.2 - 0 Novo Norte), QREN, FEDERPortuguese Foundation for Science and Technology (FCT, in the frame of projects FCOMPO 1-0124-FEDER-014784 (FCT: PTDC/EBBEBI/114364/2009

Octatosylaminophthalocyanine: a reusable chromogenic anion chemosensor

Detailed herein is the use of 2,3,9,10,16,17,23,24-octatosylaminophthalocyanine as a chromogenic chemosensor for anions. The host:guest complexes formed during the sensing event can be regenerated by acid treatment without loss of the sensing ability. This allows the phthalocyanine chemosensor to be reused. This system also responds in a colorimetric manner when exposed to the neutral solvent molecules, dimethyl sulfoxide and methanol. A single-crystal X-ray structure of the Pc 1:2 MeOH complex was obtained. It illustrates the main interactions between the host:guest species in the solid state. Fits of the binding curves are consistent with this stoichiometry predominating in the solution state

Energy production from lipids by novel anaerobes

[Excerpt] Anaerobic microbial diversity encloses a very high potential that can be used for biotechnological applications. This potential is still largely unexplored, since the majority of the microorganisms in Nature are unknown or poorly characterized. This work is focused on the study of novel anaerobic microorganisms that participate in the metabolism of lipids, long chain fatty acids (LCFA) and glycerol, with the main goal of producing valuable energy-rich organic compounds. For that, conventional anaerobic culturing procedures were combined with continuous bioreactors operation and allied to microbial ecology approaches. Two main examples of the work performed will be presented. (...