A novel Cr–CeO2/La2O3 nanocomposite electrodeposited in sulphate Cr(III) bath

ABSTRACT

For the first time, the Cr–CeO₂ / La₂O₃ composite has been electrochemically deposited in a sulphate Cr (III) bath with an oxalate complexing agent. XRD analysis revealed that incorporation of CeO₂/La₂O₃ particles into the Cr matrix does not change its state and the Cr matrix remains fine-crystalline (crystallites size < 1?nm). The cross-section SEM and EDS analysis confirmed the incorporation of CeO₂/La₂O₃ particles into the Cr matrix. The studies of the mechanical properties of the Cr–CeO₂/La₂O₃ composite have shown that the hardness of the composite increases over that of the Cr deposit due to CeO₂/La₂O₃ particles incorporation, while both the friction coefficient and wear rate decrease. The mechanism of CeO₂/La₂O₃ nanoparticles incorporation into the Cr matrix has been discussed.     

Deposition of Zn–Co by constant and pulsed current

The initial stages of both Zn–Co and Zn electrodeposition were investigated by electrochemical quartz crystal microgravimetry (EQCM). The initial electrode mass growth, determined under both pulse and constant current conditions, was much higher than predicted by Faraday's law. This was explained in terms of the precipitation of scarcely soluble compounds of zinc on an electrode surface. The EQCM data confirm that the hydroxide suppression mechanism explains the anomalous Zn and Co codeposition. A nonuniform adsorption of brightener (benzalaceton) on the profiled surface was concluded on the basis of plating distribution investigations. The additive adsorbs to a greater extent on the surface projections.     

Peculiarities of deposition of amorphous phosphate coatings on MA-2 magnesium alloys

Peculiarities of the amorphous phosphating process and the properties of obtained coatings are studied for magnesium alloys MA-2.     

Tribological effects of Cu,Fe and Zn nano‐particles,suspended in mineral and bio‐based oils

Many studies focus on nanoparticles as lubricity additives but overlook the fact that wear produces nanosized debris during the field use. In order to simulate the fine metal contaminants, which are the most widespread in various field applications, prefabricated Fe, Cu and Zn nanoparticles were used. Their 0.01–1% suspensions in vegetable and mineral oils with or without ZDDP and ashless AW package were tested on four‐ball AW under 150‐N load. Tribological effects of nanoparticles were not significant in formulations without AW additives. However, nanoFe addition produced notable lubricity improvement in already excellently performing rapeseed formulation with ZDDP, while such addition reduced performance of the ashless AW pack. Results show that metal nanoparticles can play both positive and negative roles on additive effectiveness and nanosized contaminants can significantly affect the lubricant performance. Copyright © 2015 John Wiley & Sons, Ltd.     

Determination of the dye penetration rate in porous aluminum oxide using Raman spectroscopy

Oxidised aluminum coatings are useful in various high technology applications to protect surfaces from negative environmental effects. In this study, aluminum discs and foils of industrial alloys were anodised in a sulphuric acid/oxalic acid electrolyte. Scanning electron microscopy was used to determine the pore diameter, distribution and surface porosity. The anodising procedure was adapted to produce near‐hollow templates on aluminium foil, onto which aqueous solutions of commercial chromium‐complexed anionic azodyes were dropped. Raman spectroscopy was used to detect the penetration of dye compounds based on the most intensive vibrational modes. Each dye was successfully monitored to assess its penetration rate and behaviour in the anodised coating. This method could be applied to characterise newly developed organic dyes for aluminum colouring.     

Dry sliding tribological behaviour of bilayer Cr/Cr coatings obtained in sulphate Cr(III) baths

This study was intended to investigate the properties of Cr/Cr bilayer coatings. These coatings were deposited on a copper substrate by the DC electrodeposition method from Cr(III) sulphate baths with additions of formate-urea or glycine as complexing agents. Examination of the surface morphology of Cr coatings with SEM has shown that both single and bilayer Cr coatings obtained in the Cr(III) bath with formate-urea, and those obtained in the Cr(III) bath with glycine are cracked. It has been determined that the surface microhardness (HV) of bilayer Cr coatings obtained in the Cr(III) bath with glycine is higher compared with that of single-layer Cr coatings. Wear testing of the coatings was undertaken against an Al₂O₃ ball counterface (6?mm diameter) at 1N load. The results indicate that the friction coefficients (COF) of bilayer Cr/Cr coatings obtained in the Cr(III) bath with formate-urea increased from 0.2 to 0.5 compared with that of single-layer Cr coatings, while their wear resistance deteriorated. However, bilayer Cr/Cr coatings obtained in the Cr(III) bath with glycine exhibit wear resistance close to that of single coatings with COF equal to 0.05.     

Measurement of lubricant layer thickness in anodised alumina using confocal fluorescence microscopy

Aluminium alloys are anodised to improve hardness, corrosion protection and paintability, but their wear resistance is poor, so lubricant impregnation might often be necessary. It is problematic to measure lubricant penetration into the nanopores, which are formed during anodisation, because oil molecules contain C, H and O atoms only. Type III anodised coatings of 60?µm on 6082 alloy were impregnated in fluorophore-spiked methyl oleate with or without sonication. Ball-on-plate tribotests demonstrated that sonicated specimens were more wear resistant. Confocal fluorescence microscopy showed that lubricant penetrated deep into the anodised coating after sonicated impregnation, while conventional submersive impregnation led to lubricant layer of less than 15?µm thickness. Such non-destructive methodology can scan at least 60?µm depth of anodised coatings and rapidly quantify lubricant penetration, becoming instrumental in technological applications.     

The Corrosion Behaviour of Electrochemical Zn Coated with Conversion Chromate and Phosphate Films in Concrete

The corrosion behaviour of electrochemical Zn coatings with and without chromate (VI, III) and phosphate (amorphous and crystalline) films in aerated 0.1 M NaOH + 0.1 M NaCl solution and concrete, immersed into water has been studied. The estimated corrosion rate in 0.1 M NaOH + 0.1 M NaCl solution is minimal cf. Zn chromatised in Cr³⁺ solution. The value of j_cor of Zn chromatised in Cr⁶⁺ solution is 1.5 times as high as that in Cr³⁺. The experiments carried out in concrete immersed into water (pH 12.5) have shown that all the chromate films studied do not extend the operating time of the sample. The best corrosion protection is provided by crystalline phosphate film.     

Rapid method to determine suitability of ABS plastics for metallisation

In this study, the metallisation of acrylonitrile–butadiene–styrene (ABS) plastics has been investigated. The adhesion of the metallic layer on ABS was studied by the cross-cut test. Raman spectroscopy was used to evaluate the components of ABS plastics. The results indicate that Raman spectroscopy can be applied for rapid determination of suitability of ABS plastics for metallisation.