Browsing by Author "Hannula, Pyry Mikko"

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    Controlling the deposition of silver and bimetallic silver/copper particles onto a carbon nanotube film by electrodeposition-redox replacement
    (Elsevier Science, 2019-09-25) Hannula, Pyry Mikko; Pletincx, Sven; Janas, Dawid; Yliniemi, Kirsi; Hubin, Annick; Lundström, Mari; Department of Chemical and Metallurgical Engineering; Department of Chemistry and Materials Science; Hydrometallurgy and Corrosion; Vrije Universiteit Brussel; Silesian University of Technology
    The electrodeposition-redox replacement (EDRR) process was studied to control the creation of copper and silver containing particles on the surface of a carbon nanotube film. Synthetic solutions simulating typical hydrometallurgical copper electrolysis process solutions (40 g/L Cu, 120 g/L H2SO4) with different dilute concentrations of silver (1–10 ppm) were utilized as the source for particle deposition and recovery. Such process solutions are currently underutilized for use as a potential source for the deposition of noble particles. The effect of deposition voltage, deposition time, stirring, and redox replacement time between deposition pulses were investigated as the parameters affecting the morphology and composition of the deposited particles as well as deposition kinetics. The results showed that pure copper particles can be deposited when the redox replacement time between deposition pulses is very short (t = 2 s). By increasing the redox replacement time (t = 50 s and more) the original copper particle composition transforms into a core-shell structure with an outer layer predominately consisting of silver or a bimetallic mix of copper and silver, depending on the deposition conditions. The bimetallic Cu/Ag particle size could be controlled from 200 to 840 nm by the applied deposition voltage. At high redox replacement times (t = 150 s and more) the resulting particles were shown to be pure silver with a small diameter from 100 to 250 nm.
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    Corrosion behaviour of cast and deformed copper-carbon nanotube composite wires in chloride media
    (2018-05-25) Hannula, Pyry Mikko; Masquelier, Nicolas; Lassila, Sanni; Aromaa, Jari; Janas, Dawid; Forsén, Olof; Lundström, Mari; Department of Chemical and Metallurgical Engineering; Hydrometallurgy and Corrosion; Nexans Research Centre Lens; Silesian University of Technology
    Copper-carbon nanotube (Cu-CNT) composite wires were produced by casting, rolling and drawing to produce composites with 0.05 wt% CNTs embedded at the grain boundaries of copper. The corrosion properties of wires were investigated in mild and highly corrosive media: solution I consisting of 0.05 wt% sodium chloride (NaCl) and 0.4 wt% ammonium sulfate (NH4)2SO4 and solution II consisting of 3.5 wt% NaCl. Composite samples showed similar behaviour and corrosion rates as oxygen free copper in solution I. In 3.5 wt% NaCl all composite samples showed slight improvement in corrosion resistance when compared with oxygen free copper. The corroded wire surfaces after five days in 3.5 wt% NaCl showed less dissolution for composite samples compared with pure copper. The observed decreased corrosion rate for composite wires with embedded CNTs is suggested to be due to reduced cathodic reaction. Galvanic current density between pure copper and carbon nanotubes was observed by mixed potential theory and zero resistance amperometry, neither of which showed tendency towards microgalvanic activity. The results indicate similar or slightly improved corrosion properties of copper containing small additions of CNTs in chloride containing media.
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    Energy efficient copper electrowinning and direct deposition on carbon nanotube film from industrial wastewaters
    (2019-01-10) Hannula, Pyry Mikko; Khalid, Muhammad Kamran; Janas, Dawid; Yliniemi, Kirsi; Lundström, Mari; Department of Chemical and Metallurgical Engineering; Department of Chemistry and Materials Science; Hydrometallurgy and Corrosion; Silesian University of Technology
    Heavy metal pollution is one of the most serious environmental issues of today. Removal of one common pollutant, copper, from synthetic wastewaters (containing copper, iron, sulfur and sodium) and complex authentic metallurgical plant wastewater (containing copper, iron, aluminum, zinc, nickel, arsenic, sulfur and lead among others) was studied by electrowinning. Due to the complexity and low concentration of these wastewater streams, energy efficient copper removal is challenging. The copper concentration in the investigated solutions varied from 100 to 428 ppm, while the iron concentration was an order of magnitude larger. Copper was recovered energy efficiently on glassy carbon from all investigated solutions that contained iron with a small specific energy consumption (1.5–2.5 kWh/kg Cu), depending on the solution composition and employed parameters. In the absence of iron, the specific energy consumption increased to ca. 3.5 kWh/kg Cu with the same parameters. The results indicate that the presence of iron in copper containing wastewater induces lower energy consumption during electrowinning, due to a decrease in cell voltage. Due to the low applied polarization the produced copper deposits from the authentic industrial wastewater were smooth and bright with no other metals as impurities, confirmed by energy-dispersive X-ray spectroscopy. Electrowinning was also applied on a carbon nanotube film as the working electrode to create carbon nanotube-copper composite structures of high purity directly from the industrial wastewater. These results highlight the energy efficient recovery of high purity copper from complex industrial wastewaters by electrowinning and furthermore, that the method may be used in producing high added value materials.
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    A sustainable two-layer lignin-anodized composite coating for the corrosion protection of high-strength low-alloy steel
    (Elsevier, 2020-11) Dastpak, Arman; Hannula, Pyry Mikko; Lundström, Mari; Wilson, Benjamin P.; School services, CHEM; Department of Chemical and Metallurgical Engineering; Hydrometallurgy and Corrosion
    In this study, plasticized kraft lignin was used to prepare anti-corrosive coatings on steel, which was galvanostatically anodized (80 °C, 25 wt.% NaOH) by utilizing three different current density values (24, 50 and 120 mA/cm2). It was shown that the anodization affects not only the properties of anodic coatings but also their interaction with lignin coatings. A combination of pull-off adhesion measurements with linear sweep voltammetry (LSV) demonstrated an enhanced adhesion strength of plasticized lignin coatings (4.32 MPa on anodized surface vs. 2.38 MPa on bare steel) and decreased corrosion current density from 15 μA/cm2 (bare steel) up to ca. 0.5 μA/cm2 for anodized and lignin coated steel.