Application of CuCoMnO (x) coat by sol gel technique on aluminum and copper substrates for solar absorber application

Solar thermal heaters are used widely in domestic and industrial applications. The main part of solar thermal heaters is the absorber surface which must have a maximum absorptivity (alpha) and minimum emissivity (epsilon) of solar radiation. This is achieved by application of selective coating on the absorber surface. In the present work, solar selective CuCoMnO (x) spinel films are deposited by sol gel technique using a dip-coating technique on copper and aluminum sheets. The precursor's ratio Co:Cu:Mn applied is 1:3:3. Different precursor molar ratios were combined with a fixed amount of solvents for the coating process. Process parameters such as withdrawal rate, heat treatment, and substrate materials on the coat characteristics and optical properties were studied. The coated metallic samples were heat treated at 450A degrees C for 30 min in the case of aluminum and at 200A degrees C at different times in the case of copper. Optical properties of the coatings, namely absorptivity (alpha) and emissivity (epsilon) were measured and the deposition process parameters were optimized in order to produce the maximum selectivity (alpha/epsilon) values. The deposition parameters were found to influence both the thickness and surface roughness of the coatings. As the coating thickness decreases, the absorptivity increases while the emissivity decreases irrespective of the substrate material. It was also observed from the results that when applying the coat on aluminum substrates, a maximum selectivity value of (alpha/epsilon) = 31 was realized while for the copper substrates a maximum value of (alpha/epsilon) = 81.8 was obtained. The deposited coatings were analyzed using SEM, XRD, and AFM

Deformation behavior and properties of severe plastic deformation techniques for bulk materials: A review

This paper presents a comprehensive review of the successful application of Severe Plastic Deformation (SPD) in producing ultra-fine grained (UFG) and nano-structured crystalline bulk materials. SPD achieves outstanding grain refinement without significantly altering the original dimensions of the workpiece, making it particularly useful for ductile materials that can withstand large strains under high hydrostatic pressure before failure. The study explores the grain refining mechanism during severe plastic deformation and its impact on the microstructure of metals. It also examines the use of SPD in hard to deform brittle materials like tungsten oxide, B2O3 glasses, and amorphous materials. The paper discusses the advantages and disadvantages of each technique, along with their applications and potential for combining more than one technique. The review is significant because it emphasizes recent progress in process development, which could potentially enable the industrialization of certain SPD techniques for specific applications. This paper fills the gap in the literature by addressing this issue. Overall, the review demonstrates the potential of SPD in metalworking and its application in the development of new UFG materials with improved mechanical properties

Machinability characteristics of lead free-silicon brass alloys as correlated with microstructure and mechanical properties

The aim of this work is to evaluate the machinability of Pb-free brasses with Si from 1% to 4 wt%, which were prepared using Cu 60/Zn 40 and Cu 80/Si 20 Pb-free master alloys. Machinability of the investigated alloys is tested based on cutting force, tool wear, surface roughness, and chip type. In the 1 wt% Si alloy, which exhibits maximum strength, the maximum cutting force is measured and undesirable continuous chip type is produced, while tool wear and machined surface roughness have the lowest values. Increasing the silicon content from 1% to 4%, results in increasing the tool wear by 140%, machined surface roughness by 25%, while the chip type changed from continuous to discontinuous type, and the cutting force was reduced by 50%. Machinability results are correlated with the alloy mechanical properties and with the phases present in the microstructure

Effect of Mg Addition and PMMA Coating on the Biodegradation Behaviour of Extruded Zn Material

Although zinc (Zn) is one of the elements with the greatest potential for biodegradable uses, pure Zn does not have the ideal mechanical or degrading properties for orthopaedic applications. The current research aims at studying the microstructure and corrosion behaviour of pure Zn (used as a reference material) and Zn alloyed with 1.89 wt.% magnesium (Mg), both in their extruded states as well as after being coated with polymethyl methacrylate (PMMA). The grafting-from approach was used to create a PMMA covering. The “grafting-from” method entails three steps: the alkali activation of the alloys, their functionalization with an initiator of polymerization through a phosphonate-attaching group, and the surface-initiated atom transfer radical polymerisation (SI-ATRP) to grow PMMA chains. Electrochemical and immersion corrosion tests were carried out in a simulated body fluid (SBF), and both confirmed the enhanced corrosion behaviour obtained after coating. The electrochemical test revealed a decrease in the degradation rate of the alloy from 0.37 ± 0.14 mm/y to 0.22 ± 0.01 mm/y. The immersion test showed the ability of complete protection for 240 h. After 720 h of immersion, the coated alloy displays minute crevice corrosion with very trivial pitting compared to the severe localized (galvanic and pitting) corrosion type that was detected in the bare alloy