Elchem Consulting Ltd.

Edmonton, Canada

Elchem Consulting Ltd.

Edmonton, Canada

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Djokic S.S.,Elchem Consulting Ltd. | Nikolic N.D.,University of Belgrade | Zivkovic P.M.,University of Belgrade | Popov K.I.,University of Belgrade | Djokic N.S.,Elchem Consulting Ltd.
ECS Transactions | Year: 2011

Electrodeposition and electroless deposition of metallic powders were comparatively investigated. Electrodeposition of copper is accompanied with the simultaneous hydrogen evolution, which significantly influences the morphology of Cu powder. At lower overpotentials, branched dendrites were produced. At higher overpotentials honeycomb-like deposits of copper were obtained. Formation of silver powders was characterized by the comparison of the exchange and limiting current densities. Instantaneous growth of dendrites starts at low overpotential due to large exchange current density in silver nitrate solution. Formation of powders such as Ni, Co, Ag, Pd and Au from homogenous solutions using an appropriate reducing agent or via galvanic displacement reaction was demonstrated. The hydrolysis of metallic ions is crucial in the deposition metallic powders via electroless deposition from homogenous solutions. Oxides, such as Ag 2O, Cu 2O and CuO, suspended in water can successfully be reduced with an appropriate reducing agent, leading to the precipitation of metallic powders. ©The Electrochemical Society.


Djokic S.S.,Elchem Consulting Ltd | Prashanthi K.,University of Alberta | Thundat T.,University of Alberta
Electrochemical and Solid-State Letters | Year: 2012

Thin black films composed of bismuth and respective iodides, i.e. CuI and AgI can be produced upon an immersion of copper or silver substrates into KBiI 4 solutions. The reactions leading to the formation of black films onto copper or silver surfaces into KBiI 4 solutions are spontaneous at the standard physico-chemical conditions, as evidenced by the thermodynamic data. © 2012 The Electrochemical Society.


Djokic S.S.,Elchem Consulting Ltd. | Djokic N.S.,Elchem Consulting Ltd. | Guthy C.,University of Alberta | Thundatb T.,Elchem Consulting Ltd.
Electrochimica Acta | Year: 2013

Deposition of copper, silver and gold from aqueous solutions onto germanium substrates is studied inthis work. For this purpose both acidic and alkaline solutions were used. All investigated metals cansuccessfully be deposited via the galvanic displacement reaction. These deposits are porous and withdifferent surface morphologies which depended on the type (p- or n-) of the Ge substrate used in theexperiments and on pH. Prolonged times of immersion of Ge substrates into investigated solutions maylead to a formation of more porous coatings and even powders, as successfully demonstrated on theexample of silver. It is believed that the approach presented in this work should further be investigatedas an activation step for a possible metallization of Ge substrates via autocatalytic or electrodepositionmethods. © 2013 Elsevier Ltd. All rights reserved.


Djokic S.S.,Elchem Consulting Ltd. | Cadien K.,University of Alberta
ECS Electrochemistry Letters | Year: 2015

Direct deposition of silver from fluoride-free alkaline solutions containing Ag(I) ions at pH higher than 12 onto silicon surfaces at room or elevated temperatures has been demonstrated. This deposition does not require a reducing agent, i.e. process proceeds via galvanic displacement reactions. This new process that is based on strong alkaline and fluoride-free solutions was experimentally illustrated through XRD and SEM analyses. Theoretically, it was confirmed that this process is thermodynamically favorable at room temperature, however for the real industrial applications elevated temperatures (up to 100 °C) are recommended. © The Author(s) 2015. Published by ECS.


Gaikwad R.,University of Alberta | Djokic S.S.,University of Alberta | Djokic S.S.,Elchem Consulting Ltd. | Thundat T.,University of Alberta
Journal of the Electrochemical Society | Year: 2015

A lithography technique based on reduction of metal ions on localized regions of GaAs surfaces is demonstrated. In this technique, an atomic force microscopy (AFM) tip was used to create localized defect patterns on a GaAs surface while operated in air. Subsequent exposure of the semiconductor surface to an Au(III) solution results in the deposition of gold by galvanic displacement reaction on pre-patterned defect areas. Random formation of gold islands outside of the pattern is eliminated by restricting the contact time between the Au(III) solution and GaAs semiconductor to approximately 5 minutes. © The Author(s) 2015. Published by ECS.


Djokic S.S.,Elchem Consulting Ltd. | Nolan L.,University of Alberta | Cadien K.,University of Alberta | Thundat T.,University of Alberta
ECS Electrochemistry Letters | Year: 2013

Deposition of copper or silver onto niobium surfaces is possible to achieve at elevated temperatures (above 80C) from strong alkaline solutions containing Cu(II) or Ag(I) ions at pH higher than 12. This deposition does not require a reducing agent, i.e. process proceeds via galvanic displacement reaction. © 2012 The Electrochemical Society.


Djokic S.,Elchem Consulting Ltd. | Djokic N.,University of Alberta | Thundat T.,University of Alberta
ECS Transactions | Year: 2013

Physico-chemical and antimicrobial properties of composite materials comprising a gauze coated with silver, Ag7O8NO3 (silver oxysalt), copper, or bismuth oxides were investigated. For this purpose, nylon substrates were coated with metallic silver or metallic copper using the electroless deposition procedures. Coating of nylon gauze with BiOCl was performed using BiCl3 as a source of bismuth ions. Additionally, silver or copper coated nylon substrates were treated with complexed K[BiI 4] solutions. Simple bacteriostatic and bactericidal activities of produced composite materials were also investigated. All samples containing oxidized silver or copper species in a combination with bismuth exhibited both bactericidal and bacteriostatic activities. BiOCl coated nylon substrates exhibited some bactericidal activity against P. aeruginosa and S. aureus, but notably, the results of the present showed that the presence of bismuth only was not sufficient for an acceptable antimicrobial activity. © The Electrochemical Society.


Djokic S.S.,Elchem Consulting Ltd. | Djokic N.S.,Elchem Consulting Ltd. | Thundat T.,University of Alberta
Journal of the Electrochemical Society | Year: 2012

Deposition of bismuth powders was investigated in this work. Bi powders can be obtained from heterogeneous systems e.g., via galvanic displacement reaction by an immersion of aluminum metal into Bi(III) complexed solutions. It was shown that, on the aluminum substrate, Bi powders can be obtained from acid, close to neutral or from alkaline solutions. Bi particles obtained via galvanic deposition are predominantly dendritic. To avoid the incorporation of Bi - oxides into the final product, it is recommended that the deposition via galvanic displacement reaction from K[BiI4] or complexed Bi(III)-citrate-EDTA solutions on Al substrate is carried out in the acidic solutions in order to suppress the hydrolysis of Bi(III) ions. Alternatively, bismuth powders can successfully be produced from homogenous aqueous systems using Bi(III) complexed solutions as a source of Bi and an alkaline Sn(II) solution acting as a reducing agent of Bi(III) ions. The average particle size was about 0.25 μm for Bi powders produced from Bi(III) - citrate complexed solution using alkaline Sn(II) as a reducing agent. For Bi powders produced from K[BiI4] solutions with Sn(II) as a reducing agent, the average particle size was estimated at about 0.65 μm. © 2012 The Electrochemical Society.


Djokic S.,Elchem Consulting Ltd.
ECS Transactions | Year: 2010

The antimicrobial activity of electrochemically oxidized silver and copper was investigated in this work. The surface oxidation of silver and copper samples was performed in a 2M KOH solution potentiostatically. Electrochemically oxidized silver specimens exhibited antimicrobial activity against Pseudomonas aeruginosa, which was attributed to the presence of silver oxide films at the surface. With non-oxidized silver specimens no antimicrobial activity was found. Both, metallic and electrochemically oxidized copper samples exhibited antimicrobial activity. The antimicrobial activity of copper is a consequence of the release of Cu(II) ions into the tested media. The release of Cu(II) ions may occur either due to the presence of copper oxide at the surface of electrochemically oxidized samples or due to corrosion of copper metal in the tested media. ©The Electrochemical Society.


Djoki S.S.,Elchem Consulting Ltd. | Djoki N.S.,Elchem Consulting Ltd.
Journal of the Electrochemical Society | Year: 2011

Deposition of metallic powders from aqueous solutions without an external current source is presented. Metallic powders can successfully be produced via galvanic displacement reaction or by electroless deposition from homogenous aqueous solutions or slurries. Formation of powders such as Cu, Ni, Co, Ag, Pd, and Au from homogenous solutions using an appropriate reducing agent or Ag via galvanic displacement reaction was demonstrated. The hydrolysis of metallic ions is a crucial step in the deposition metallic powders via electroless deposition from homogenous solutions. To confirm that the hydrolysis phenomenon is essential in the electroless deposition of metallic powders, oxides, such as Ag2O, Cu2O, and CuO, were suspended in water. It was clearly demonstrated that these oxides can be successfully reduced with an appropriate reducing agent, leading to the precipitation of metallic powders. © 2011 The Electrochemical Society.

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