Effects of some plating variables on the electrodeposition of catalytically active nickel-thallium alloy powders

The electrodeposition of nickel-thallium alloy powders was investigated from a selected bath of the composition 0.0125 NiSO₄·6H₂O, 0.01 TICI, 0.10 (NH₄)₂SO₄, 0.10 H₃BO₃ and 0.07 Na₂SO₄·10 H₂O (mol dm^?3). The effects of the pH of the bath, deposition current density and deposition time on the cathodic polarisation, current efficiency and composition of the electrodeposited alloy were determined. The properties of the electrodeposits examined, as a function of the above-mentioned variables, were surface morphology and catalytic activity towards the decomposition of 0.4% H₂O₂ solution. It was found from this investigation that the operating variables influence to a great extent the current efficiency, composition and surface morphology of the electrodeposited alloys; and the catalytic activity is primarily controlled by the surface morphology.     

Electrodeposition of Sn-Co alloys from gluconate baths

Electrodeposition of Sn-Co alloys was carried out from baths containing 2–20 g dm^–3 SnSO₄, 4–18 g dm^–3 CoSO₄.7H₂O, C₆H₁₁O₇Na and K₂SO₄ under different conditions of bath composition, pH, current density and temperature on to copper substrates. The influence of these variables on the cathodic potential, cathodic current efficiency and composition of the deposit were studied. The results show that the deposition of Sn-Co alloys from gluconate baths depends greatly on the concentration of tin. At high tin concentrations, tin is the more noble component. At low tin concentrations, tin reduction is strongly suppressed due to the formation of a more stable Sn-gluconate complex species and tin becomes the less noble component. The codeposition of Sn-Co alloy from these baths can be classified as an irregular plating system. The surface morphology of deposits was examined by scanning electron microscopy and crystal structure by X-ray. The results show that the structure of the deposits was controlled by the alloy composition.     

Electroplating of cobalt from aqueous citrate baths

Electroplating of cobalt onto steel substrates from citrate baths has been investigated under different conditions of bath composition, current density, pH and temperature. A detailed study has been made of the influence of these variables on the potentiodynamic cathodic polarization curves, cathodic current efficiency and the throwing power as well as the throwing index of these baths. The optimum bath composition has been established and it contains: CoSO₄.7H₂O (0·36 mol dm⁻³) trisodium citrate (0·19 mol dm⁻³) and citric acid (0·1 mol dm⁻³) at pH 5·0. The microhardness of cobalt electrodeposited from citrate baths is high and it may be, under certain conditions, two or three times higher than that reported for cobalt electrodeposited from other different baths. The surface morphology of the as-plated cobalt was investigated by using scanning electron microscopy (SEM) while the structure was studied by using X-ray diffraction analysis and anodic stripping voltammetry (ASV) techniques. © 1998 Society of Chemical Industry     

Preparation and characterization of nanocrystalline Fe–Ni–Cr alloy electrodeposits on Fe substrate

Fe–Ni–Cr alloy layers were prepared by electrodeposition from trivalent chromium plating bath in chloride-sulfate based solution. The influences of bath composition and plating parameters on the alloy electrodeposition process and the properties of deposited alloy were studied. The effects of plating parameters and bath composition such as current density, bath pH, bath temperature, the concentrations of FeSO₄ · 7H₂O and CrCl₃ · 6H₂O on the contents of Fe and Cr in Fe–Ni–Cr alloy layer were investigated. Electrodeposited Fe–Ni–Cr alloy layers on Fe substrate were characterized by X-ray diffraction (XRD), Electronic Differential System (EDS) and a CHI600B electrochemistry workstation. The composition of the Fe–Ni–Cr coatings depends on bath composition and plating conditions including pH, current density, and temperature. The internal structure of the alloy is nanocrystalline, the average grain size is 87 nm, and the corrosion resistance of the alloy layers is better than that of pure nickel layers.     

Electrodeposition of catalytically active nickel powders from sulphate baths. I. Effect of bath constituents

A detailed study was made of the influence of the sulphate bath constituents: 0.3 - 0.0125 NiSO₄·7H₂O (I), 0.05 – 0.23 (NH₄)₂SO₄ (II), 0.1 – 0.4 H₃BO₃ (III) and 0.07 – 0.35 mol l^?1 Na₂SO₄·10H₂O (IV) on the electrodeposition of nickel powder. The cathodic polarization, current efficiency, growth morphology, crystallite size and catalytic activity of the electrodeposited nickel powders were affected to different extents by the bath constituents. A highly pure nickel powder characterized by a small crystallite size (776 Å) and moderate catalytic activity was obtained from a bath containing: 0.0125 (I), 0.23 (II), 0.1 (III) and 0.07 mol l^?1 (IV) at a current density of 10 A dm^?2 and electrolysis time 60 min. at 25 °C. Structural studies with a scanning electron microscope are given and a reaction mechanism for the electrolytic powder deposition is discussed.     

Electrodeposition of Co–Cu alloy coatings from glycinate baths

The cathodic polarization, cathodic current efficiency of codeposition, composition and structure of Co–Cu alloy as a function of bath composition, current density and temperature were studied. Electrodeposition was carried out from solutions containing CuSO₄ · 5H₂O, CoSO₄ · 7H₂O, Na₂SO₄ and NH₂CH₂COOH. The cathodic current efficiency of codeposition (CCE) was high and it increased with increasing temperature and Cu²⁺ content in the bath, but it decreased with current density. The codeposition of Co–Cu alloys from these baths can be classified as regular. The Co content of the deposit increased with Co²⁺ content and current density and decreased with glycine concentration and temperature. The structure of the deposited alloys was characterized by anodic stripping and X-ray diffraction techniques. The data showed that the deposited alloys consisted of a single solid solution phase with a face-centred cubic (f.c.c.) structure.     

Electroplating of Fe-Ni alloys: a sulphate-amine bath

Thin films of Fe-Ni alloys have been electroplated from acidic sulphate bath (0.06 mol dm^–3 NiSO₄, O.O15 mol dm^–3 FeSO₄, 0.005 mol dm^–3 ascorbic acid, 20 g dm^–3 boric acid and 1 g dm^–3 saccharin) containing aliphatic amines. The percentage Ni in the alloy varied with bath composition (Fe/Ni), current density, stirring of the medium, nature and concentration of the amine. Increase of temperature and pH of the medium increased the percentage Ni in the deposit. The composition of the alloy remained constant with thickness of the film. The cathodic current efficiency depends on the plating variables. The plating potential in acidic sulphate bath was shifted in the less noble direction by the presence of amines. Smooth and bright films are obtained with small grain size when the Ni in the film is 75% or above. Electroplating conditions are optimized to get thin, magnetic 2080 Fe-Ni films.Presented at the International Symposium on Recent Aspects of Electroanalytical Chemistry and Electrochemical Technology at Chanigarh, India.     

Electrodeposition and characterization of thin layers of Zn–Co alloys obtained from glycinate baths

An alkaline bath containing CoSO₄ · 7H₂O, ZnSO₄ · 7H₂O, Na₂SO₄ and NH₂CH₂COOH is proposed for the deposition of thin layers of Zn–Co alloys onto steel substrates. Electrodeposition was carried out at 0.216–1.080 A dm^–2, pH 10 and 10–55 °C. The influence of bath composition, current density and temperature on galvanostatic cathodic polarization, cathodic current efficiency and alloy composition was studied. Different proportions of the two metals were obtained by using different deposition parameters, but at all Zn(II)/Co(II) ratios studied, preferential deposition of zinc occurred and anomalous codeposition took place. Increasing the bath temperature enhanced the cobalt content in the deposit. X-ray diffraction measurements indicated that the phase structure of the deposits was controlled by the applied current density. The Co₅Zn₂₁ phase was formed at low current density, while the CoZn₁₃ phase was formed at high current density. The potentiodynamic dissolution of the coatings showed that they contained Zn–Co alloy of different content and structure.     

Electrodeposition of catalytically active nickel-thallium alloy powders from sulphate baths

The electrodeposition of nickel-thallium alloy powder was investigated from acidic sulphate baths containing 0.0125 NiSO₄·6H₂O, 0.005–0.020 Tl Cl, 0.05–0.23 (NH₄)₂SO₄, 0.1 H₃BO₃ and 0.07 mol l^–1 Na₂SO₄ · 10H₂O. The polarization curves, the percentage composition and the current efficiency of the electrodeposited alloy powders were determined as a function of the bath composition. In addition, some properties of the deposits were examined such as the surface morphology, the structure as revealed by X-ray diffraction analysis and the catalytic activity towards the decomposition of 0.4% H₂O₂ solution. The results indicate that the characteristics of the alloy deposition and the properties of the alloy powder are affected to different extents by the bath composition.     

The electrodepositions of copper and nickel from trifluoroacetate-H2O baths

In the present study, the electrodepositions of copper from the Cu(CF₃COO)₂CF₃COOHH₂O bath and nickel from the Ni(CF₃COO)₂NH₄ClH₂O bath, were studied.In the copper electrodeposition from Cu(CF₃COO)₂ (100 g/l)CF₃COOH(0.1 N)H₂O bath, the cathode current efficiency showed about 100% and the anode current efficiency showed over 100% at low cd. In the nickel electrodeposition from Ni(CF₃COO)₂ (200 g/lH₄Cl(15.0 g/l)H₂O bath, the efficiencies of the cathode and anode were about 100%. The range of current density to obtain bright and smooth copper and nickel deposits were 4.0 ～ 24 A/dm², 5.0 ～ 16 A/dm² respectively, and the cross-section of the electrodeposits showed a granular structure.The rates of the electrodeposition of copper and nickel from the above-mentioned baths were controlled by the charge-transfer reaction in the same way as in the reaction in non-aqueous solution[1, 2].     

The influence of ammonium and methods for removal during the anaerobic treatment of poultry manure

The addition of exogenous NH₄Cl to poultry manure and synthetic medium was used to study the effect of ammonia-nitrogen on the activity and composition of a methanogenic consortium. Results indicated that the production of biogas and methane was not affected by the variation in NH₄Cl concentration within the range 2–10 g dm⁻³ (0·5–2·6 g N-NH₄ dm⁻³). At higher values of ammonium (10–30 g dm⁻³ or 2–8 g N-NH₄ dm⁻³) a significant decline in both parameters (by 50–60% for biogas and 80–90% for methane) was observed. A significant decrease in the numbers of bacteria of all physiological groups (especially proteolytic and methanogenic) was observed when more than 30 g NH₄Cl dm⁻³ (7·8 g N-NH₄ dm⁻³) was added to the fermentation medium. The addition of 10% (w/v) of powdered phosphorite ore enhanced the production of biogas and methane at NH₄Cl concentrations up to 30 g dm⁻³, and also changed the composition of the methanogenic consortium. A partial recovery in the numbers of proteolytic and methanogenic bacteria coupled with the decrease in the density of sulphate-reducers was observed. High concentrations (more than 50 g dm⁻³) of NH₄Cl seemed to cause irreversible inhibition of methanogenesis which could not be eliminated by the addition of phosphorites. ©1997 SCI     

Effect of cellulose triacetate membrane thickness on forward‐osmosis performance and application for spent electroless nickel plating baths

Cellulose triacetate (CTA) forward‐osmosis (FO) membranes were prepared via the phase inversion method. The influence of thickness on the performance and morphology of CTA FO membranes was discussed in detail. When the thickness of the membrane was 50.0 ± 0.5 μm (CTA4), the prototype CTA membranes displayed a water flux of 20.2 L m^?2 h^?1 and a reverse salt transport of 14.6 g m^?2 h^?1 using 1 mol/L NaCl as the draw solution and deionized water as the feed solution during the FO process at 25 °C. In addition, the high‐performance CTA4 FO membranes have been used to process spent electroless nickel plating baths where the water flux could reach 13 L m^?2 h^?1 and NiSO₄·6H₂O crystals occurred in the feed solution of the spent electroless nickel plating baths. The recovery rates of NiSO₄·6H₂O and water from the spent electroless nickel plating baths were 44.54% and 53.53%, respectively. This study focused on improving membrane design for the FO process and finding a new method of waste liquor or wastewater treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45049.     

Electrodeposition of catalytically active Co-Ni-Tl alloy powders from dilute sulphate baths

Cobalt-nickel-thallium alloy powders were electrodeposited from dilute metal sulphate baths of composition: 0.007–0.0245 mol l^–1 CoSO₄·7H₂O, 0.0245–0.007 mol l^–1 NiSO₄·6H₂O, 0.001 mol l^–1 TlCl, 0.5 mol l^–1 (NH₄)₂SO₄, 0.07 mol l^–1 Na₂SO₄·10H₂O and 0.4 mol l^–1 H₃BO₃. The cathodic polarization curves were traced during electrodeposition and utilized in the discussion of a reaction mechanism for the electrolytic powder deposition. The alloy composition and the cathodic current efficiency were influenced to a great extent by the bath composition (I) and slightly by the deposition current density (II). Irrespective of variables (I) and (II), the electrodeposition of the alloy belonged to the anomalous type. The surface morphology and the catalytic activity, towards the decomposition of 0.4% H₂O₂ solution, of the as-deposited alloy powders were affected predominantly by the percentage of cobalt in the alloy. X-ray diffraction studies showed that the alloys consisted mainly of the face-centred cubic nickel phase either alone or with minor proportions of face-centred cubic cobalt phase and hexagonal close-packed -cobalt phase. The occurrence of the latter phases was observed only in the alloys with a higher cobalt percentage than nickel.     

Utilization of response surface methodology to optimize the culture media for the production of rhamnolipids by Pseudomonas aeruginosa AT10

Pseudomonas aeruginosa AT10 produced a mixture of surface‐active rhamnolipids when cultivated on mineral medium with waste free fatty acids as carbon source. The development of the production process to an industrial scale included the design of the culture medium. A 2⁴ full factorial, central composite rotational design and response surface modelling method (RSM) was used to enhance rhamnolipid production by Pseudomonas aeruginosa AT10. The components that are critical for the process medium were the carbon source, the nitrogen source (NaNO₃), the phosphate content (K₂ HPO₄/KH₂PO₄ 2:1) and the iron content (FeSO₄·7H₂O). Two responses were measured, biomass and rhamnolipid production. The maximum biomass obtained was 12.06 g dm^?3 DCW, when the medium contained 50 g dm^?3 carbon source, 9 g dm^?3 NaNO₃, 7 g dm^?3 phosphate and 13.7 mg dm^?3 FeSO₄·7H₂O. The maximum concentration of rhamnolipid, 18.7 g dm^?3, was attained in medium that contained 50 g dm^?3 carbon source, 4.6 g dm^?3 NaNO₃, 1 g dm^?3 phosphate and 7.4 mg dm^?3 FeSO₄·7H₂O. © 2002 Society of Chemical Industry     

Electrodeposition of cobalt-nickel alloys from Watts-type baths

The electrodeposition of cobalt-nickel alloys was carried out from Watts-type baths of composition 5–60gl⁻¹ CoSO₄ · 7H₂O, 100–300gl⁻¹ NiCl₂ · 6H₂O and 25gl⁻¹ H₃BO₃ at a pH of 4.4. The cathodic polarization during electrodeposition and the alloy composition were greatly influenced by the concentrations of the depositable metal ions; whereas, the cathodic efficiency was only slightly affected. Under the examined conditions, the electrodeposition of the alloys belonged to the anomalous type. X-ray diffraction studies revealed that the alloys were deposited in the face-centred cubic structure and consisted of a mixture of the two phases α(Co) andβ(Ni). Sound, smooth and bright alloy deposits were obtained and their properties were improved by increasing the nickel content of the bath.     

Electroless plating of rhenium–nickel alloys

In this study, rhenium–nickel (Re–Ni) films were formed by electroless deposition on conductive (Cu) and non-conductive (SiO₂) substrates. Different bath compositions were evaluated, aiming to achieve high Re-content. Both sodium hypophosphite and dimethylamine-borane were used as reducing agents. Films containing up to 75 at% Re were obtained. The influence of nickel concentration in the solution on alloy composition, deposition rate and surface morphology were determined. It is shown that Ni²⁺ acts as a catalyst for the in situ reduction of the perrhenate ion, in a manner similar to what was proposed for electroplating of the same alloy. The rate of electroless plating is similar to that found in electroplating at an applied current density of 50 mA cm⁻². While pure Re cannot be deposited from our electroless plating baths, the addition of even a very small amount of Ni²⁺ ions (0.25 mM) is enough to start the induced codeposition of Re. Proper selection of the bath composition can lead to fine control of the alloy thickness and its Re-content, thus making it potentially attractive for thin barrier layers.     

Adsorption of chlorophyll-a from acetone solution on natural and activated bentonite

The adsorption of chlorophyll-a on bentonite desiccated at 110°C, untreated and acid-treated with H₂SO₄ solutions over a concentration range between 0·25 and 2·50 mol dm^?3, from acetone solution at 25°C has been studied. The adsorption isotherms may be classified as using Giles' classification, as type S (untreated sample and 0·25 mol dm^?3 H₂SO₄-treated sample), type H (0·50 mol dm^?3 H₂SO₄-treated sample) and type L (1·00 and 2·50 mol dm^?3 H₂SO₄-treated samples). This fact suggests that the bentonite surfaces (low, high and medium affinity, respectively) behave in differently relation to the adsorption of the chlorophyll-a molecules. The experimental data points have been fitted to the Freundlich equation in order to calculate the adsorption capacities (K_f) of the samples; K_f values range from 0·43 mg kg^?1 for the untreated bentonite up to 108·89 mg kg^?1 for the 0·50 M H₂SO₄-treated bentonite. The removal efficiencies (R) have also been calculated and range from 5·71% for the untreated bentonite up to 85·18% for the 0·50 M H₂SO₄-treated bentonite.     

Electrodeposition and corrosion behaviour of a Ni–W–B amorphous alloy

Electrodeposition of Ni–W–B alloys from plating baths containing ammonia and citrate is reported. Optimum conditions for plating including current density, temperature, mechanical agitation and pH were studied. The corrosion resistance and amorphous character were also evaluated. The operational conditions for depositing the alloy with good corrosion resistance were: current density 35 mA cm⁻², bath temperature 40 °C, pH 9.0 and cathode rotation at 90 rpm. The alloy was deposited at 38% current efficiency, with an average composition of 73 wt% Ni, 27 wt% W and traces of boron and with E _corr −0.300 V and R _p 3.369×10⁴ Ω. The deposit obtained under these conditions had an amorphous character with the presence of some microcracks on its surface reaching down to the copper substrate. Electrochemical corrosion tests verified that the Ni–W–B alloy had better corrosion resistance than Co–W–B.     

Preparation of WC/Co composite powders by electroless plating

Ultra-fine WC/Co composite powders were prepared by electroless plating in this study. The Co layers with an average thickness of 50–100 nm were uniformly and completely covered on raw WC particles with a diameter of 0.3–0.5 µm. The influences of electroless plating conditions on the composites were investigated. The Co layer covering on WC particles was controlled by the content of CoSO₄·7H₂O, pH value and bath temperature. With increasing the content of CoSO₄·7H₂O up to 25 g/L, both the weight gain and the plating rate markedly increased. However, when the content of CoSO₄·7H₂O further increased to 30 g/L, while the weight gain displayed a slight decrease, the plating rate continued to increase moderately. Moreover, with the increase of pH value from 9.5 to 11, both the weight gain and the reaction time decreased. Furthermore, the plating rate exhibited an exponential relationship with the bath temperature. When the pH value, bath temperature and the concentration of CoSO₄·7H₂O are 10, 80 °C and 25 g/L respectively, the weight gain of Co-coated WC composite powders is 185.1 mg/g.     

Black nickel electrodeposition from a modified Watts bath

Black nickel coatings were electrodeposited on to steel substrates from a Watts bath containing potassium nitrate. The best operating conditions necessary to produce smooth and highly adherent black nickel were found to be NiSO₄ · 6H₂O 0.63 M, NiCl₂ · 6H₂O 0.09 M, H₃BO₃ 0.3 M and KNO₃ 0.2 M at pH of 4.6, i=0.5 A dm⁻², T=25 °C and t=10 min. The modified Watts bath has a throwing power (TP) of 61%, which is higher than that reported, not only for nickel, but also for many other metals electrodeposited from different baths. The potentiostatic current–time transients indicate instantaneous nucleation. X-ray diffraction (XRD) analysis shows that the black nickel deposit is pure metallic nickel with Ni(111) preferred orientation.