Search Results (6)

Two ways of anodizing 3D-printed AlSi10Mg alloy were characterized, and then their fatigue properties were evaluated. Test specimens were fabricated via a laser-powder bed fusion (L-PBF) process followed by machining. Normal and hard anodizing were both conducted in a sulfuric acid bath. The anodized layer was observed using FE-SEM/EDS. Fine Si particles dispersed in the matrix showing web-like patterns were incorporated in the anodized layer. By etching the Si particles away with Keller’s reagent, a characteristic maze-like 3D structure of anodized Al was observed. Then, rotating bending fatigue tests were carried out to evaluate the fatigue strength at 10⁷ cycles. The fatigue strength of the as-machined, normal-anodized and hard-anodized specimens was 106, 100 and 95 MPa, respectively. The fatigue limits were proportional to the surface roughness with higher linearity. By reducing the surface roughness, the fatigue strength of the hard-anodized specimen was improved. This result demonstrates the possibility of improving the fatigue properties of anodized components by reducing their surface roughness. Lastly, a CASS (copper-accelerated acetic acid salt spray) test was conducted, and superior corrosion resistance of the normal- and hard-anodized layers was verified. Full article

The cable-stayed bridge anchorage system is prone to serious corrosion problems in the offshore environment, threatening its service safety. Based on the copper accelerated salt spray (CASS) test, the anchorage system was subjected to accelerated corrosion and then dissected along the axial direction to study the corrosion damage evolution of the internal structure. This revealed the evolution of corrosion damage in the anchorage system of offshore cable-stayed bridges. The results show that in the offshore environment, a large number of corrosion factors enter the interior of the cable anchorage system through the splicing seam at the junction of the anchor cup and the connecting barrel, and spread to both ends, thus causing corrosion damage to the anchor cup, connecting barrel, filling medium and cable steel wires. Inside the cable of the anchorage system, cross-sections with a higher corrosion level on the outer circle steel wires will also have a higher overall corrosion level. The outer circle steel wires are less able to meet the strength requirements, because they withstand most of the corrosion effects, and the corrosion pits on the surface of the steel wires will render them much weaker than the design tensile strength and fracture. After the CASS test, the ductility of cable steel wires decreases from the inner circle to the outer circle, and the higher the corrosion level of steel wires, the more obvious the brittle indications; the steel wires tend to undergo brittle failure. In the design and manufacture of the cable-stayed bridge anchorage system, special attention should be paid to the corrosion protection of the splicing seam, as well as the corrosion condition and residual strength of steel wires in the outer circle of the cable, to delay the degradation of the mechanical properties and brittle damage of the anchorage system. Full article

Chitosan is a chitin-derived fiber, extracted from the shellfish shells, a by-product of the fish industry, or from fungi grown in bioreactors. In oenology, it is used for the control of Brettanomyces spp., for the prevention of ferric, copper, and protein casse and for clarification. The International Organisation of Vine and Wine established the exclusive utilization of fungal chitosan to avoid the eventuality of allergic reactions. This work focuses on the differences between two chitosan categories, fungal and animal chitosan, characterizing several samples in terms of chitin content and degree of deacetylation. In addition, different acids were used to dissolve chitosans, and their effect on viscosity and on the efficacy in wine clarification were observed. The results demonstrated that even if fungal and animal chitosans shared similar chemical properties (deacetylation degree and chitin content), they showed different viscosity depending on their molecular weight but also on the acid used to dissolve them. A significant difference was discovered on their fining properties, as animal chitosans showed a faster and greater sedimentation compared to the fungal ones, independently from the acid used for their dissolution. This suggests that physical–chemical differences in the molecular structure occur between the two chitosan categories and that this significantly affects their technologic (oenological) properties. Full article

Recently, countries from around the globe have been actively developing a new solar power system, namely, the floating photovoltaic (FPV) system. FPV is advantageous in terms of efficiency and cost effectiveness; however, environmental conditions on the surface of water are harsher than on the ground, and the regulations and standards for the long-term durability of supporting devices are insufficient. As a result, this study aims to investigate the durability of supporting devices through a novel type of accelerated corrosion test, copper-accelerated acetic acid salt spray (CASS). After an eight-day CASS test, the results demonstrated that only a small area of white protective layer on the SUPERDYMA shape steel was fully corroded and rusted. Moreover, five types of screw, fastened solidly on the SUPERDYMA shape steel, namely a galvanized steel screw capped with a type 316 stainless steel (SS) nut, a type 304 SS screw, a type 410 SS screw, a chromate-passivated galvanized steel screw, and a XP zinc–tin alloy coated steel screw, achieved varying degrees of rust. In general, the corrosion degree of the eight-day CASS test was more serious than that of the 136-day neutral salt spray (NSS) test. Therefore, the CASS test is faster and more efficient for the evaluation of the durability of supporting devices. Full article

Copper is one of the most frequently occurring heavy metals in must and wine. It is introduced by pesticides, brass fittings, and as copper sulphate for treatment of reductive off-flavors. At higher concentrations, copper has harmful effects on the wine. It contributes to the oxidation of wine ingredients, browning reactions, cloudiness, inhibition of microorganisms, and wine fermentation. Last but not least, there is also a danger to the consumer. At present, some physicochemical methods exist to reduce the copper content in must and wine, but they all have their shortcomings. A possible solution is the biosorption of metals by yeasts or lactobacilli. Copper can also reach must and wine in the form of copper-containing phenol oxidases (grape tyrosinase, Botrytis cinerea laccases). Similar to free copper, they oxidize phenolic wine compounds, and thus lead to considerable changes in color and nutritional value, making the product ultimately unsaleable. All measurements for enzyme inactivation such as heat treatment, and addition of sulphites or bentonite are either problematic or not effective enough. The application of oenological tannins could offer a way out but needs further research. Full article

Certain heavy metals present in wine, including copper, can form insoluble salts and can induce additional casse, so their determination is important for its quality and stability. In this context, a new biosensor for quantification of copper ions with BSA protein (bovine serum albumin) and using SPE electrodes (screen-printed electrodes) is proposed. The objective of this research was to develop a miniaturized, portable, and low-cost alternative to classical methods. A potentiostat, which displays the response in the form of a cyclic voltammogram, was used in order to carry out this method. Values measured for the performance characteristics of the new biosensor revealed a good sensitivity (21.01 μA mM⁻¹cm⁻²), reproducibility (93.8%), and limit of detection (0.173 ppm), suggesting that it has a high degree of application in the analysis proposed by our research. The results obtained for wine samples were compared with the reference method, atomic absorption spectrometer (AAS), and it was indicated that the developed biosensor is efficient and can be used successfully in the analysis of copper in wine. For the 20 samples of red wine analyzed with AAS, the concentration range of copper was between 0.011 and 0.695 mg/L and with the developed biosensor it was between 0.037 and 0.658 mg/L. Similar results were obtained for the 20 samples of white wine, 0.121–0.765 mg/L (AAS) and 0.192–0.789 mg/L (developed biosensor), respectively. Full article