Coatings and Surface Modification of Alloys for Tribo-Corrosion Applications

This review of the tribocorrosion of coatings and surface modifications covers nearly 195 papers and reviews that have been published in the past 15 years, as compared to only 37 works published up to 2007, which were the subject of a previous review published in 2007. It shows that the research into the subject area is vibrant and growing, to cover emerging deposition, surface modification and testing techniques as well as environmental influences and modelling developments. This growth reflects the need for machines to operate in harsh environments coupled with requirements for increased service life, lower running costs and improved safety factors. Research has also reacted to the need for multifunctional coating surfaces as well as functionally graded systems with regard to depth. The review covers a range of coating types designed for a wide range of potential applications. The emerging technologies are seen to be molten-, solution-, PVD- and PEO-based coatings, with CVD coatings being a less popular solution. There is a growing research interest in duplex surface engineering and coating systems. Surface performance shows a strong playoff between wear, friction and corrosion rates, often with antagonistic relationships and complicated interactions between multiple mechanisms at different scale lengths within tribocorrosion contacts. The tribologically induced stresses are seen to drive damage propagation and accelerate corrosion either within the coating or at the coating coating–substrate interface. This places a focus on coating defect density. The environment (such as pH, DO2, CO2, salinity and temperature) is also shown to have a strong influence on tribocorrosion performance. Coating and surface modification solutions being developed for tribocorrosion applications include a whole range of electrodeposited coatings, hard and tough coatings and high-impedance coatings such as doped diamond-like carbon. Hybrid and multilayered coatings are also being used to control damage penetration into the coating (to increase toughness) and to manage stresses. A particular focus involves the combination of various treatment techniques. The review also shows the importance of the microstructure, the active phases that are dissolved and the critical role of surface films and their composition (oxide or passive) in tribocorrosion performance which, although discovered for bulk materials, is equally applicable to coating performance. New techniques show methods for revealing the response of surfaces to tribocorrosion (i.e., scanning electrochemical microscopy). Modelling tribocorrosion has yet to embrace the full range of coatings and the fact that some coatings/environments result in reduced wear and thus are antagonistic rather than synergistic. The actual synergistic/antagonistic mechanisms are not well understood, making them difficult to model

The selected laser melting production and subsequent post-processing of Ti-6Al-4V prosthetic acetabular

&nbsp;Processing and post processing of human prosthetic acetabular cup by using 3D printing. The results showed using 3D printers leads to fabrication customized implants with higher quality.<br /

Degradation of persistent organic pollutants (pharmaceuticals & dyes) by combined dielectric barrier electrohydraulic discharge system and photo catalysts

Philosophiae Doctor - PhDWater pollution problems have continued to increase not only in South Africa but worldwide due to human activities. The presence of organic toxins and bacteria in water sources is mostly due to population growth, industrial development and agricultural run-off. The accumulation of persistent organic pollutants (POPs) in water and wastewater sources has raised various questions on the safety of potable water used for drinking, households and other activities. Traditional mechanical, biological, physical, and chemical methods such as flocculation, coagulation, reverse osmosis, filtration, ultrafiltration, adsorption and active sludge treatment methods have failed to remove these new xenobiotic from aquatic media. This is due to the fact that instead of degrading the toxins, the methods listed above often transform organic contaminants from one form another. Also, the post treatment of by-products resulting from these methods is costly. In addition, this new generation of contaminants, often referred to as compounds of emerging concern (CECs), exist in tiny concentrations (ng) and conventional techniques have not been designed for these low levels of pollutants which consequently pass through during treatment processes and end up in the treated effluents at minute concentrations (ug/L to ng/L). However, complete remediation of chemical toxins in wastewater treatment plants has not been achieved. A better option involves the direct oxidation of the pollutants in the effluent but so far their complete mineralisation has not been achieved. Advanced oxidation processes (AOPs) have emerged in recent years as adequate techniques for the complete removal of POPs. AOPs focus more on the production of non-selective hydroxyl radicals (OH.) which have been considered as the most powerful oxidants (2.8 V) that directly or indirectly mineralise the organic pollutant into dissolved CO2, H2O and harmless end-products. However, the use of excessive chemicals, corrosion of catalyst supports, wasted UV, ozone escapes and the cost associated with AOPs often limit their application for the removal of POPs from water and wastewater treatment facilities. The principal aim of this study was to optimise a double cylindrical barrier discharge (DBD) system for the removal of low concentration persistent organic pollutants (POPs). The efficiency of the DBD system was initially confirmed by quantification of three main reactive oxygen species including ozone (O3), hydrogen peroxide (H2O2) and hydroxyl radicals (.OH) among others. These three active species were successfully detected and quantified using indigo, per titanyl sulphate and terephthallic acid (TA) spectroscopy methods, respectively. Thereafter, the DBD reactor was optimised by assessing the effect of electrophysico-chemical parameters on the removal efficiencies of two selected pollutants including orange II sodium salt dye (O.II) and sulfamethoxazole (SMX), a pharmaceutical, as model persistent organic pollutants

Международная конференция "Физическая мезомеханика. Материалы с многоуровневой иерархически организованной структурой и интеллектуальные производственные технологии", 6-10 сентября 2021 г., Томск, Россия : тезисы докладов

Издание содержит тезисы международной конференции «Физическая мезомеханика. Материалы с многоуровневой иерархически организованной структурой и интеллектуальные производственные технологии». Физическая мезомеханика является научным направлением, в рамках которого материал представляется как иерархическая система взаимосвязанных структурных (масштабных) уровней. В книге отражены последние достижения в области развития принципов и методологии физической мезомеханики и результаты их применения к созданию перспективных материалов в интересах развития новых производственных технологий, освоения космического пространства, в том числе дальнего космоса, электроники, атомной энергетики, нефтегазового комплекса, медицины, транспорта и др. Книга адресована научным сотрудникам, инженерам, аспирантам и специалистам, занимающимся вопросами физической мезомеханики, разработки наноструктурных объемных и наноразмерных материалов, наноструктурированием поверхностных слоев, тонкими пленками и покрытиями, нанотехнологиями, компьютерным конструированием новых материалов и технологий их получения, технологиями локальной нестационарной металлургии и обработки материалов, неразрушающими методами контроля. Публикуется в авторской редакции