Katya Nikolova Ignatova

Katya Nikolova Ignatova
University of Chemical Technology and Metallurgy | UCTM · Department Inorganic and Electrochemical Productions

About

27
Publications
802
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54
Citations
Citations since 2016
8 Research Items
32 Citations
201620172018201920202021202202468
201620172018201920202021202202468
201620172018201920202021202202468
201620172018201920202021202202468

Publications

Publications (27)
Article
Sn-Ni alloy powders with a wide range of compositions and structures by constant current, constant potential and pulse potential modes were deposited. Increasing the Ni²⁺/Sn²⁺ ratio in the electrolyte from 1 to 8 in both stationary modes leads to changes in the shape and composition of the powder particles from typically dendritic (5÷7 wt%Ni), to c...
Article
The effect of P-providing components (phosphorous acid, H3PO3 and sodium hypophosphite, NaH2PO2) in modified Watts electrolyte (pH = 2; 80 °C) on the barrier ability and durability of the deposited Ni–Co–P and Ni–Co (as a reference) coatings during extended exposure in 3.5% NaCl until 672 h was studied. The data acquired for the charge transfer and...
Article
Full-text available
The effect of NaH2PO2 concentration in the electrolyte (pH = 2) on the kinetics of NiP, CoP and NiCoP alloys electrodeposition at room temperature was studied. It was established that at concentration of NaH2PO2 about 0,2 M the deposition rate of NiP alloys decreases; the deposition rate of CoP alloys increases but at the same time the quality of t...
Article
This paper reports the effect of the Ni/Co ratio in a citrate electrolyte (with an optimum content of Na3 citrate) on the deposition kinetics, chemical and phase composition of the Ni-Co alloy coating, current cathodic efficiency of the electrodeposition, and morphology of the coating. It was established that by increasing the Co content in the sol...
Conference Paper
Full-text available
This paper presents some results, concerning the effect of organic additive (saccharin) on the composition and morphology of the alloy Ni-Co coatings deposited in citrate electrolyte using two types of deposition - constant potential and pulse potential electrodeposition. It was established, that the presence of saccharin in the electrolyte lowers...
Article
Full-text available
The kinetics of the electrodeposition of Cu and Co in Co-Cu alloy, chemical composition, cathodic current efficiency and morphology of Co-Cu alloys electrodeposited from an ammonia-sulphate electrolyte (AMSE) and from a weakly acidic citrate electrolyte (CE) without and with addition of saccharin (CE+SHR) at constant potential mode are compared. Th...
Article
The changes in the phase composition (through X-Ray analysis) and the corrosion behaviors (through potentiodynamic polarization studies in 4 % NaCl) of Ni-Co alloys, electrodeposited from a citrate electrolyte by changing the Ni/Coratio, content of organic additive (saccharine) and the content of sodium citrate in the solution, are studied. It is f...
Article
Full-text available
Ni-Co alloys with varying cobalt content are electrodeposited in stationary potentiostatic mode employing citrate electrolyte, either with or without addition of saccharin (SHR) at different Ni/Co ratios and variable content of sodium citrate (Na3citrate) in the electrolyte. The changes in the microstructure, chemical composition and cathodic curre...
Article
The membrane electrochemical technology for obtainment of three-polyphosphate non-cyanide electrolyte for coppering is developed and optimized. For the purpose of characterizing the selectivity of the ionic membranes used, the processes of mass transfer are examined through determining the transmission numbers of the ions in the three-chamber elect...
Article
Full-text available
In the paper the results from the study of the kinetic of joint electrodeposition of Ni and Co in Ni-Co alloy system are reported. It is found that the co-deposition of Ni and Co in Ni-Co alloy system in slightly acidic citrate electrolyte occurs under combined diffusion-kinetic control with a typical mechanism of nucleation similar to those in the...
Article
Full-text available
The elecrodeposition of Ni and Co was studied by electrochemical techniques in varying compositions of slightly acidic citrate electrolyte. Cyclic voltammetry and current transient measurements were used to characterize the initial stages of nucleation, growth mechanism and electrodeposition of Ni and Co. The voltammetry analysis showed that the el...
Article
The kinetics of independent and joined deposition of Ni and Co in citrate electrolyte in the presence of three types of additives: saccharine (SCH), urotropine (URT) and gelatine (GLT), is examined. Comparison is made between the chemical composition, the current cathodic efficiency (CCE) and the morphology of Ni-Co alloys depending on the type of...
Article
The kinetics of deposition of Co, Ni, and Ni-Co from low-acid citrate electrolyte on Cu and on chemically oxidized Al is compared. It is found that the formation of Ni-Co alloy on the Al cathode is hampered to a greater extent in comparison with the Cu electrode. In both cases (Cu and Al electrodes) "anomalous" co-deposition of Co and Ni is registe...
Article
Full-text available
The article reports the results from the examination on the effect of background additive (H3BO3) and complexation agent Na(3)citrate on the type of Ni and Co complexes at either pH=5.0 or pH=7.0. It is found that at pH=5.0 in an electrolyte containing both additives, NiCit(-) and CoCit(-) prevail (lg K-inst(Ni) = -5,379; lg K-inst(co).= -4,38). At...
Article
The kinetics of stationary and pulse potentiostatic electrodeposition of Co, Ni and Cu as well as the possibility for their co-deposition in alloys CoNi and CoNiCu from slightly acidic citrate electrolyte was investigated. The morphologies and the elemental composition of coatings were studied using SEM and EDSA analysis respectively. It was establ...
Article
The kinetics of electrodeposition and the microstructure of pure Ag and alloyed Ag-Ni powders were investigated depending on the type of electrolyte and conditions for deposition. It was found out that in acid nitrate electrolyte the Ag powders are white after deposition and have a more determined crystal structure. In complex ammonia-nitrate elect...
Article
The kinetics of the individual deposition of Cu, Co and Ni as well as the alloy deposition of CoCu, NiCo and NiCoCu in the slightly acidic citrate electrolyte (pH= 5,5) was investigated. Data about the alloy deposition in pulse potentiostatic mode at different pulse frequencies was received also. The morphology and the elemental composition of the...
Article
An eco-friendly membrane technology for electrochemical preparation of rodanide silver concentrates for the purposes of electroplating is developed. Theprocesses of mass transfer in three-chamber electrolyzerwith ionite membrane are studied. A detailed balance of the voltage between electrodes in membrane preparation of rodanide silver concentrate...
Article
The investigation on anode behavior of silver represents an important and integral part of the implementation of membrane technology for obtaining silver concentrates for galvanotechnics. Through recording the galvanodynamic polarization dependencies, evidences are obtained for the kinetics of anode dissolution of silver and the critical densities...
Article
The polarization dependences are recorded and the conditions of Ni–Co powder formation in amino-chloride electrolyte are found for different proportions of Ni2+/Co2+. Energy-dispersive spectral analysis (EDSA) is used to obtain data on the morphology and elemental composition of Ni–Co alloy powders depending on the Ni2+ and Co2+ ratio in the soluti...
Article
By means of the cyclic voltammetry (CV) the effect of nitrite anions (in the form of NaNO2) on the kinetics of separate and of codeposition of Ag and Cu is examined. The effect of the electrode substrate and the proportion of the basic components of the solution on the deposition kinetics and the powder formation of Ag-Cu alloys is also established...
Article
This article reports results, obtained by the method of cyclic voltamperometiy, applied to study the processes and mechanism of deposition of copper from ammonium nitrate electrolyte. The effect of the initial potential has been studied as well as that of the potential sweeping rate and the nature of the cathode substrate (copper or silver) in rega...
Article
Results of the study of the joint effect of square-wave pulsating electrolysis and presence of gelatin as an additive on the kinetics of silver deposition and its morphology are reported. It is found that the effect of additive effect grows with the decrease of pulse frequency and with the increase of pause/pulse ratio, Frequencies of about 500 Hz...
Article
The present paper reports results from the study of morphology, phase composition, and microstructure of Pd−Ag alloy powder obtained by potentiostatic pulsating electrolysis. Several independent physical methods (electron microscopy, X-ray diffraction and electronographic probe analysis) were applied. It was found that the powder contained two basi...
Article
Results are reported from a kinetic study of single and joint deposition of Pd and Ag, and of the morphology, structure and chemical composition of Pd-Ag powders deposited from aminonitrite electrolyte under potentiostatic and pulsating square-wave overpotential. It was established that the Pd content in the powder reaches 50% with increase in the...
Article
The process of copper electroextraction from sulfuric acid waste waters was studied. The experiments were carried out at different current densities (0,1 – 0,15 A / dm 2) , copper and sulfuric acid concentration (resp. 0,1 – 0,5 g/l and 10 – 150 g / l). It was established, that the rate of electroextraction is high at lower current densities and ac...
Article
Polarization characteristics of the processes of Cu, Co and Cu-Co alloy electrodeposition from ammonium sul-phate containing supporting electrolyte and their morphologies are investigated as a function of Cu 2+ and Co 2+ ions concentracions. By application of energy dispersive spectral analysis, (EDSA), including X-Ray analysis and SEM, data are ob...

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