RESUMO
In this study, we developed and optimized a trivalent chromium coating electrodeposited on 304L stainless steel (SS) from a Cr-trivalent bath. The results reveal that the Cr coatings at all bath temperatures except for 80 °C showed clusters of polyhedral grains, however, the grain sizes decreased with an increase in bath temperature. Also, the coatings deposited at bath temperatures of 30, 50, and 60 °C experienced networks of cracks, which decreased in population density as temperature increased. However, the coatings deposited at bath temperatures of 70 and 80 °C were crack-free due to surface modification, confirmed by 3D profile results with an advanced power spectral density and a multi-Gaussian histogram analysis. The mechanical test results demonstrate that the adhesion and wear resistance of the Cr-coatings formed on the SS substrate significantly improved, with the optimal coefficient of friction of 0.18. Likewise, electrochemical behavior observations of the Cr coatings show that pitting resistance improved with the increase in bath temperature conditions, as shown in the pitting potential values which increased from 272.6 mV to 436.2 mV as bath temperature increases from 30 °C to 80 °C. From this study, it is proposed that the Cr-coatings deposited at a bath temperature of 80 °C presents the optimal coating performance concerning a combination of all the target qualities aimed, such as better tribological behavior and improved pitting resistance. Thus, enabling the establishment of an innovative method to overcome the conventional issues encountered in Cr electrodeposition of SSs.
RESUMO
For the dry storage of Canada Deuterium Uranium (CANDU) spent nuclear fuels, the integrity of Zircaloy-4 fuel cladding has to be verified. However, the formation of ~10 µm-thick oxide layers in typical CANDU reactor operating conditions takes several years, which makes sample preparation a slow process. To overcome such limitations, in this study, an accelerated formation of an oxide layer on Zircaloy-4 cladding tube was developed with a combination of high-temperature water corrosion (HT-WC) and air oxidation (AO). First, Zircaloy-4 tubes were corroded in oxygenated (2 ppm dissolved oxygen) high-temperature water (360 °C/19.5 MPa) for 500 h. Then, the tubes were air-oxidized at 500 °C for 30 h. Finally, the tubes were corroded again in HT-WC for 500 h to produce ~10 µm-thick oxide layers. The morphology and characteristics of the oxide layer in each step were analyzed using X-ray diffraction, scanning and transmission electron microscopy. The results showed that the oxide layer formed in the accelerated method was comparable to that formed in HT-WC in terms of morphology and oxide phases. Thus, the accelerated oxide formation method can be used to prepare an oxidized Zircaloy-4 cladding tube for CANDU fuel integrity analysis.
RESUMO
As an innovative therapeutic strategy, drug repurposing affords old, approved, and already established drugs a chance at new indications. In the wake of the COVID-19 pandemic and the accompanied urgency for a lasting treatment, drug repurposing has come in handy to stem the debilitating effects of the disease. Among other therapeutic options currently in clinical trials, chloroquine (CQ) and the hydroxylated analogue, hydroxychloroquine (HCQ) have been frontline therapeutic options in most formal and informal clinical settings with varying degrees of efficacy against this life-threatening disease. Their status in randomized clinical trials is related to the biochemical and pharmacological profiles as validated by in vitro, in vivo and case studies. With the aim to bear a balance for their use in the long run, this review not only synopsizes findings from recent studies on the degrees of efficacy and roles of CQ/HCQ as potential anti-COVID-19 agents but also highlights our perspectives for their consideration in rational drug repositioning and use.
