Examining the Effect of Electrosynthesis Conditions on the Ni-P Alloy Composition

The Ni–P alloys are widely used as catalysts, magnetic and wear resistant materials. Properties of the nickel-phosphorous alloys are defined by the composition. A highly regulated technique to obtain the alloys with specified composition is the electrosynthesis. It is a relevant task to establish dependences of the alloy composition on the process conditions. In the present work we examined the influence of electrolysis parameters on the Ni–P alloy composition, obtained from the methanesulfonate and sulfate electrolytes. It is shown that an increase in the concentration of sodium hypophosphite, acidity and temperature of the electrolyte increases phosphorus content in the alloy. It was established that when carrying out the electrosynthesis under galvanostatic mode, a change in the alloy composition is predetermined by the rate of phosphorus formation. Atomic phosphorus is formed as a result of the course of two reactions. There occurs the electroreduction and disproportionation of hypophosphite-anion involving hydrogen ions. An increase in the concentration of hydrogen ions in the near-electrode layer contributes to an increase in the rate of phosphorus formation and growing phosphorus content in the alloy. That is why the alloys with a higher content of phosphorus are formed at lower pH indices of the electrolyte and at higher temperature. It was established that weak buffer properties of the methanesulfonate electrolyte are responsible for the lowered phosphorus content in the synthesized alloy. High pH index in the near-electrode layer reduces the rate of phosphorus formation. Established regularities might prove very useful when designing new technologies of the Ni–P alloy electrosynthesis of specified composition from the methanesulfonate electrolyte

Development of A New Suspension Electrolyte Based on Methane-sulphonic Acid for the Electrodeposition of Cu–TiO2 Composites

Electrodeposition of composite coatings based on copper is a promising direction in the creation of advanced materials for multifunctional purposes. An important area of composites application is to use them in the treatment systems for gas emissions and wastewater. It is advisable to use semiconductor oxide materials, in particular titanium dioxide, as the photocatalysts in the photo destruction of organic pollutants of wastewater. The structural features of wastewater treatment equipment require that titanium dioxide particles should be fixed in a rigid matrix. Resolving the task of fixing photosensitive elements at the surface of a certain configuration implies the electrodeposition of coatings by composites, in particular Cu–TiO2. An important factor affecting the functional characteristics of composites and their manufacturing technology is the nature of the electrolyte. It has been shown that the electrodeposition of Cu–TiO2 composites from methane-sulfonate electrolytes makes it possible to reduce the coagulation of the dispersed phase and to obtain coatings with a high content of titanium dioxide from a suspension solution containing no more than 4 g/l of TiO2. It was established that the content of the dispersed phase in the composite made at a current density of 2 A/dm2 and the concentration of titanium dioxide in the electrolyte at the level of 4 g/l is 1.3 % by weight, which is twice as much as when using a sulfate electrolyte. It has been shown that the increase in the content of the dispersed phase in the coatings from 0.1 to 1.3 % by weight is accompanied by an increase in the degree of photo destruction of the colorant from 6 to 15.5 %. The micro-hardness of coatings increases, in this case, by 30 %. The proposed electrolyte to make the Cu–TiO2 composites is an important contribution to the development of the synthesis of wear-resistant high-performance photocatalysts for treating wastewater from organic pollutant

Research Into Composition and Properties of the Ni–Fe Electrolytic Alloy

Promising yet insufficiently studied is the new electrolyte based on methanesulfonate salts of the alloy-forming metals. Examining the laws that govern the electrodeposition of the Ni–Fe alloy with assigned physical-chemiсal properties from the methanesulfonate electrolyte is a relevant task. In the present work we established influence of the concentration of iron(ІІ) ions in the electrolyte and of current density on the composition of alloy. The content of iron in the Ni–Fe alloy grows with an increase in the concentration of iron(ІІ) ions in the methanesulfonate electrolyte. Dependence of the content of iron in the alloy on current density is of extreme character. The maximum corresponds to the current density of 1 A/dm2. It is shown that the organic additive applied in the present work, sodium saccharinate, does not exert any substantial influence on the composition of alloy at current density exceeding 2 A/dm2. Sodium saccharinate increases microhardness of the coating with the Ni–Fe alloy whose values reach 500 kg/cm2. When introducing into the methanesulfonate deposition electrolyte of the Ni–Fe alloy of 6 mmol/l of sodium saccharinate, practically unstressed precipitations precipitate. A reduction in the internal stresses leads to a decrease in the values of coercive force of the alloy. It is demonstrated that the investigated properties of the Ni–Fe precipitations are determined by the structure of coatings. Sodium saccharinate, being a surface-active compound under the conditions of electrolysis, changes the structure of the cathodic Ni–Fe alloy and improves functional characteristics of coatings. The established dependences represent a rather valuable basis for designing new technologies of the electrodeposition of polyfunctional coatings with the Ni–Fe alloy with enhanced mechanical and magnetic characteristic

Study of Thermal Dehydration of Sodium Orthophosphate Monosubstituted

Depending on the conditions of conducting the synthesis, it is possible to obtain polymeric phosphates of different composition and structure. The mixtures of polyphosphates, employed in the production of technological lubricants, are expedient to synthesize by the high-temperature dehydration of sodium orthophosphate monosubstituted. The temperature ranges, over which the thermochemical transformations of sodium orthophosphate monosubstituted with the formation of polyphosphates proceed, are established by the thermogravimetric method. The composition of polyphosphates is determined using the X-ray phase analysis. Quantitative composition of the mixtures of polyphosphates is determined by applying the original method of eluent ion-exchange chromatography. It is established that the basic products of thermal dehydration of sodium orthophosphate monosubstituted in the range of temperatures 200–650 °C are Na3Р3О9, Na2H2P2O7 and Na6P6O18. Thermochemical transformations of NaH2PO4 into Na6P6O18 at temperature 650 °C are accompanied by the side reactions of formation of Na3H2P3O10. We proposed the chemical scheme of the high-temperature dehydration of sodium orthophosphate monosubstituted. Kinetics of the isothermal process of obtaining the polymeric phosphates from sodium orthophosphate monosubstituted at different temperatures is examined.We established quantitative composition of the mixtures of inorganic polymeric phosphates depending on the duration of isothermal process of dehydration. The possibility of obtaining a salt mixture of polymeric phosphates of the assigned qualitative and quantitative composition is demonstrated. We proposed to use the mixture: 76 % Na6P6O18, 8 % Na2H2P2O7, 8 % Na3H2P3O10, 8 % NaH2PO4, obtained at 650 °C, as the basic phosphate component of technological lubricants for the hot rolling of pipes

Research Into Corrosion and Electrocatalytic Properties of the Modified Oxide Films on Tin

Oxide films on tin, modified by titanium compounds, are non­toxic and serve as anticorrosion protection, material for gas sensors, photo­ and electrocatalysts. We investigated the process of anodic tin treatment in the presence of potassium metatitanate. It is shown that the two­stage technique for the formation of an oxide film at the electrode potentials of −0.3 V and 3.0 V makes it possible to substantially increase the content of titanium oxide compounds in the oxide mixture. The content of Ti(IV) reaches values of 14−15 % (mol). Films with a maximum content of titanium compounds and the largest corrosion resistance are formed at a concentration of potassium metatitanate above 1·10–3 mol/l. The time of self­activation of such films is 10 times longer than that of the unmodified films. We explored catalytic properties of the obtained films with mixed composition SnОх(TiОу). It is shown that an increase in the content of titanium oxide compounds in the film contributes to the acceleration of anodic oxidation of MTBE. It was established that this process takes place directly on the surface of the oxide film rather than during interaction with oxygen formed on the anode. The modified oxide films SnОх(TiОу) on tin with maximal corrosion resistance and electrocatalytic activity are formed from the solutions that contain 0.5M KOH

Study of the Anticorrosion Effect of Polymer Phosphates on Steel at Elevated Temperatures

Technological greases based on polyphosphates of alkali metals have great prospects for application at high-temperature machining of steel. An important task is to study the anti-corrosive effect of polyphosphates on steel at elevated temperatures. Temperature ranges, in which phase transformations of metaphosphate and sodium tripolyphosphate, as well as interaction with iron oxide, occur, were established using a thermogravimetric method. Composition of products of interaction between metaphosphate and sodium tripolyphosphate and scale is determined employing an X-ray phase analysis. It was established that in the region of temperatures of hot steel deformation the iron oxides, contained in scale, are dissolved in molten metaphosphate and sodium tripolyphosphate. As a result of interaction between sodium metaphosphate and iron oxide, the mixed polyphosphates Na3Fe2(PO4)3 and Na9Fe2(P3O10)3 are formed. It is shown that sodium tripolyphosphate almost does not participate in the interaction with the iron oxide of scale. Comparison of the results of corrosion test of the steel surface, treated in the presence of a polyphosphate lubrication and sodium chloride, testifies to the high anti-corrosive effect of polyphosphates. Thus, the time before the emergence of first signs of corrosion in the presence of polyphosphates increased fourfold, while the degree of corrosion damage was reduced by 40 times. It was established that at the deformation treatment of steel at a temperature of 800 °C in the presence of a polyphosphate lubricant, corrosion resistance is due to the formation of a barrier film at the steel surface, consisting of mixed polymer phosphates

Investigation of Adsorption Behavior of Smoothing Additives in Copper Plating Electrolytes

Smoothing additives are the necessary component of copper plating electrolytes. Choice of the required additive is determined by the type of electrolyte and its pH values. Studies of adsorption behavior of such compounds in electrolytes with different acidities are of current interest. Adsorption activity of poly-N, N'-dimethylsafranine and poly-N, N'-diethylsafranine on the copper electrode in sulfate electrolytes was established in the present work. The dependencies of the differential capacitance of the double electric layer of the copper electrode on the potential which were obtained in acidic (pH 1.7) and neutral (pH 5.9) electrolytes indicate that acidity of the medium has a significant effect on the additive adsorption. The studied organic substances show high adsorption activity in an acidic solution. The likely cause of the established phenomenon in an acid medium is transition of these organic compounds to a protonated state with formation of positively charged amino groups. Cationic groups of the additives are responsible for an additional interaction with the cathode surface and provide stronger adsorption of poly-N, N'-dimethylsafranine and poly N, N'-diethylsafranine on the copper electrode in comparison with a neutral sulfate electrolyte. Poly-N, N'-diethylsafranine with its molecular weight higher than that of poly-N, N'-dimethylsafranine is characterized by higher adsorbability. Since the smoothing effect of additives in electrodeposition of copper coatings is determined by their adsorption properties, it should be expected that the most effective in this process will be the use of poly-N, N'-diethylsafranine at lower pH values of the copper plating electrolytes

Research Into Effect of Propionic and Acrylic Acids on the Electrodeposition of Nickel

Nickel coatings are widely used in machine-building, electronics, automotive and aerospace industries. High requirements for environmental safety and operational performance of contemporary processes of electrochemical nickel plating predetermine the search for the new electrolytes. Electrolytes based on carboxylic acids are characterized by high buffer properties, ecological safety, and enhanced values of limiting current. Heuristic approach when fabricating comprehensive electrolytes, based on empirical data, does not make it possible to conduct predictable optimization of the formulations of nickel plating electrolytes. Solving this problem seems possible when using a quantum-chemical simulation. In this work, we performed quantum-chemical calculations for the propionate and acrylate complexes of nickel. It was established that coordination numbers of the propionate and acrylate complexes of nickel are equal to five and six, respectively. It is shown that electroreduction of the propionate nickel complex proceeds with the formation of an intermediate particle. The negative charge of this particle is localized on the intrasphere molecules of water. This may lead to the electroreduction of the latter and to an increase in the pH of a near-electrode layer. In the intermediate particle of the acrylate complex, localization of the charge occurs on the vinyl fragment of acrylate-ion. Electrochemical reaction of reduction of the coordinated water molecules in such a particle is not energetically favorable. It was established that the isolation of nickel from the acrylate complex proceeds with lower kinetic difficulties than from the propionate complex. An assumption was made that fewer insoluble hydroxide nickel compounds, which block the cathode surface, form in the acrylate electrolyte.Such an assumption is based on the fact that given close buffer properties of acids, electroreduction of the acrylate complexes does not imply the involvement of coordinated water molecules in the electrode process. The results obtained are very valuable for selecting the nature of carboxylic acid as a component for the complex nickel plating electrolyt