Marian Jaskuła

Study of the kinetics of the cementation of silver ions onto copper in a rotating cylinder system from acidic sulphate solutions

Abstract The kinetics of the cementation of silver ions onto copper from acidic sulphate solutions were investigated in a rotating cylinder system. The influence of several parameters on the course of the reaction, such as cylinder rotation speed, initial concentration of silver ions, temperature, concentration of sulphuric acid and the presence or absence of oxygen in the system, was investigated, and the reaction was found to follow first-order kinetics. The initial rate of the reaction is limited by diffusion through the mass transfer boundary layer. The experimental values of the initial rate constant calculated from both methods used for recording the changes of the silver ions concentration in the solutions corresponded ideally to the values predicted by semi-theoretical equations describing the turbulent flow in the rotating cylinder system. After the initial period of cementation, an enhancement of the rate was observed. In oxygenated solutions, rate enhancement is associated mainly with changes in the structure of the deposit involving an increase in the effective surface area during the process. However, the rate enhancement phenomenon in the absence of oxygen is attributed not only to an increase in the effective surface area but also to the chemical reaction between the Cu + and Ag + ions.

Study of the mechanism of silver ions cementation onto copper from acidic sulphate solutions and the morphology of the silver deposit

Abstract The mechanism of silver ion cementation with copper in acidic sulphate solutions has been investigated. It was found that oxygen present in solutions can strongly modify the mechanism of the process. In the first stage of the reaction, the Cu + ions appear in the solution independently of the presence or absence of oxygen. In deoxygenated solutions Cu + ions generated in the first stage can be transferred partially into the bulk of the solution. The migration of the reaction front results in a loosely adhering silver deposit. The reaction between Ag + and Cu + ions occurring in the bulk of the solution can be initiated in the deoxygenated solutions after reaching a certain value of the Cu + /Ag + concentration ratio. This reaction occurring in the bulk of the solution, parallel to the cementation reaction, consumes an additional amount of silver ions and produces a silver colloid in the deoxygenated solution. In oxygenated solutions saturated with oxygen the front of the reaction is located on the copper surface. As a result, tight and well-adherent silver deposit is formed. The morphology of the silver deposit is independent of the presence of oxygen in the solution. The tendency of silver deposition on already deposited silver cement was observed in the oxygenated solutions. This phenomenon is attributed to the fact that the surface area of anodic sites is more developed in the presence than in the absence of oxygen in the system due to the corrosion of copper. The anodic sites develop their surface into the bulk of the copper substrate and create cavities under the reaction surface.

Study of the kinetics of silver ions cementation onto copper from sulphuric acid solution

Abstract The kinetics of silver cementation with copper from sulphuric acid solution has been studied with a rotating cylinder. Two independent methods have been used to monitor the concentration of Ag+ ions in the solution: atomic absorption spectrophotometry (AAS) method and a continuous method with the use of an ion-selective electrode. The reaction has been found to follow first-order kinetics with respect to silver ion concentration. The initial rate of the reaction is limited by diffusion through the mass transfer boundary layer. The rate constant for initial period of cementation is independent of the absence or the presence of oxygen in the solutions and is independent of the presence of Cu2+ ions up to the concentration of 2×10−4 M. After the initial period of cementation a rate enhancement has been observed. In solutions containing 20 mg/L of Ag+ ions, the rate enhancement is associated with changes in the structure of the deposit which involve an increase in the effective surface area during the process. However, the rate enhancement phenomenon in the absence of oxygen at 100 mg/L of Ag+ is attributed not only to an increase in the effective surface area but also to a chemical reaction between Cu+ and Ag+ ions.

The initial behaviour of freshly etched copper in moderately acid, aerated chloride solutions

Abstract When freshly etched samples of various types of copper were exposed in moderately acid, aerated chloride solutions, two phenomena were observed. First the corrosion potential and the pH of the solution decreased over a shorter time, then the potential increased over a long period (600–1500 min), following an s-shaped pattern. Increase in pH during the second stage was avoided using a pH-stat. The corrosion rate increased little or not at all over the entire period. A tentative interpretation of the short-term behaviour is presented with some reservation. The long-term development of the potential suggests phase formation or transformation following the Avrami pattern. By suitable derivations it was possible to fit the development of potentials to the Avrami equation. Subsequent examinations by Auger spectroscopy proved the presence of thin layers of Cu 2 O on the copper surfaces, increasing in thickness with exposure time. The dissolution kinetics can be described in terms of two parallel electrochemical reactions and a simultaneous non-electrochemical dissolution reaction.

Properties of nanostructures obtained by anodization of aluminum in phosphoric acid at moderate potentials

The influence of the process duration, anodizing potential and methanol addition on the structural features of porous anodic alumina formed in a 0.3 M H3PO4 solutions by two# s tep self#organized anodizing was investigated for potentials ranging from 100 to 170 V. The structural features of porous structures including pore diameter and interpore distance were evaluated from FE#SEM top#view images for samples anodized in the presence and absence of methanol. For the highest studied anodizing time and methanol volume fraction, an excellent agreement between experimental values of the interpore distance and theoretical predictions was observed. The pore arrangement regularity was analyzed for various electrolyte compositions and anodizing potentials. It was found that the regularity ratio of porous alumina increases linearly with increasing anodizing potential and time. The addition of methanol improves the quality of nanostructures and especially better uniformity of pore sizes is observed in the presence of the highest studied methanol content.

Nanoporous anodic titanium dioxide layers as potential drug delivery systems: Drug release kinetics and mechanism

Nanoporous anodic titanium dioxide (ATO) layers on Ti foil were prepared via a three step anodization process in an electrolyte based on an ethylene glycol solution with fluoride ions. Some of the ATO samples were heat-treated in order to achieve two different crystallographic structures - anatase (400°C) and a mixture of anatase and rutile (600°C). The structural and morphological characterizations of ATO layers were performed using a field emission scanning electron microscope (SEM). The hydrophilicity of ATO layers was determined with contact angle measurements using distilled water. Ibuprofen and gentamicin were loaded effectively inside the ATO nanopores. Afterwards, an in vitro drug release was conducted for 24h under a static and dynamic flow conditions in a phosphate buffer solution at 37°C. The drug concentrations were determined using UV-Vis spectrophotometry. The absorbance of ibuprofen was measured directly at 222nm, whether gentamicin was determined as a complex with silver nanoparticles (Ag NPs) at 394nm. Both compounds exhibited long term release profiles, despite the ATO structure. A new release model, based on the desorption of the drug from the ATO top surface followed by the desorption and diffusion of the drug from the nanopores, was derived. The proposed release model was fitted to the experimental drug release profiles, and kinetic parameters were calculated.

Effect of different polishing methods on anodic titanium dioxide formation

Among various methods of synthesis of nanostructured TiO2, a self-organized anodization is the most commonly used and discussed in the literature. However, different methods of pretreatment of Ti before anodic titanium dioxide (ATO) formation are not often addressed. Therefore, various polishing procedures based on mechanical, chemical, electrochemical, and combined electrochemical with chemical pretreatments were examined to establish whether they represent effective methods for smooth Ti surface preparation before anodization. The ATO layers were prepared via two-step anodization carried out in an ethylene glycol solution containing fluoride ions at 20°C and under the anodizing potential of 60 V. The influence of applied polishing method on the cell size, pore diameter, pore circularity, pore density, and porosity of the top ATO layer was studied. In addition, the effect of polishing procedure on cell arrangement in ATO films was also investigated. The quantitative analyses of the regularity of cell arrangement, based on the regularity ratio derived from bottom-view SEM images, showed that the type of polishing procedure does not affect the cell order.

Pulse reversal plating of nickel-cobalt alloys

Abstract Electroforming, as a versatile process for fabrication of durable tools, is experiencing an increasing interest with the start of commercial use of products with micro or nanofeatures. Electroformed tools can be utilised for polymer, glass and metal replication processes and, in addition, when extreme demands, in terms of tool accuracy, process temperature and tool wear, are requested. In order to meet these demands, electroforming of hard nickel alloys is an obvious way forward. This paper presents several electrolytes from which it is possible to deposit nickel–cobalt alloys with high hardness (>550 HV), low internal stress and easy maintenance. Moreover, different organic complexing agents – as well as alternatives to boric acid – have been investigated.

Effects of nanoporous anodic titanium oxide on human adipose derived stem cells

The aim of current bone biomaterials research is to design implants that induce controlled, guided, successful, and rapid healing. Titanium implants are widely used in dental, orthopedic, and reconstructive surgery. A series of studies has indicated that cells can respond not only to the chemical properties of the biomaterial, but also, in particular, to the changes in surface topography. Nanoporous materials remain in focus of scientific queries due to their exclusive properties and broad applications. One such material is nanostructured titanium oxide with highly ordered, mutually perpendicular nanopores. Nanoporous anodic titanium dioxide (TiO2) films were fabricated by a three-step anodization process in propan-1,2,3-triol-based electrolyte containing fluoride ions. Adipose-derived stem cells offer many interesting opportunities for regenerative medicine. The important goal of tissue engineering is to direct stem cell differentiation into a desired cell lineage. The influence of nanoporous TiO2 with pore diameters of 80 and 108 nm on cell response, growth, viability, and ability to differentiate into osteoblastic lineage of human adipose-derived progenitors was explored. Cells were harvested from the subcutaneous abdominal fat tissue by a simple, minimally invasive, and inexpensive method. Our results indicate that anodic nanostructured TiO2 is a safe and nontoxic biomaterial. In vitro studies demonstrated that the nanotopography induced and enhanced osteodifferentiation of human adipose-derived stem cells from the abdominal subcutaneous fat tissue.

Mean thermodynamic activity coefficient of CuSO4 in the ternary system CuSO4H2SO4H2O at 60°C

Abstract The mean thermodynamic activity coefficient of CuSO4 has been determined in the ternary system CuSO4H2SO4H2O (CuSO4 0.2-1.15 mol/kg H2O; H2SO4 0.1–2.5 mol/kg H2O) using measurements of the electromotive force (e.m.f.) of the cell Cu(Hg)¦CuSO4, H2SO4¦Hg2SO4, Hg at 60°C. The activity coefficients obtained are described by a simple polynomial γ±CuSO4 = −1.307−0.124X−0.278Y−0.006X2+0.095XY+0.059Y2 [where X=mCuSO4 (mol/kg), Y=mH2SO4 (mol/kg)], reproducing the experimental results with a mean error of 0.5%.