SYNTHESIS OF NICKEL HYDROXIDE IN THE PRESENCE OF ACETATE ION AS A «SOFT» LIGAND FOR APPLICATION IN CHEMICAL POWER SOURCES

Owing to high electrochemical activity [1], nickel hydroxides are used in various electrochemical devices. Ni(OH)2, double nickel hydroxides are used as the active material of nickel oxide electrode for alkaline batteries [2, 3], and as oxide after sintering – in lithium batteries [4]. Various Ni(OH)2 modifications are used as the active material of the Faradic electrode of hybrid supercapacitors. Ni(OH)2 is used on its own [5] (in the form of nano-sized [6] or ultrafine particles [7]), and in the form of a composite with nanocarbon materials (graphene oxide [8], carbon nanotubes [9]). For thin layer supercapacitors, a nickel film can be formed on the conductive substrate [10]. Nickel hydroxide is used in electrochromic devices [11, 12] because thin layers of Ni(OH)2 are almost transparent, while NiOOH has a dark-brown color. It is also used for the electrochemical oxidation of various organic compounds [13, 14] and in sensors [15, 16]. For a given application, there are optimal characteristics of nickel hydroxide. At the same time, the trend in chemical technology is directed synthesis of products with specific properties. Therefore, determining the influence of synthesis parameters on structural parameters and electrochemical properties of Ni(OH)2 is a relevant problem.


Nadiia Sova
PrAT «VENTS», Boyarka, Ukraine ORCID: http://orcid.org/0000-0002-7223-6974 The paper reports results of examining the influence of modifier admixtures on the corrosion resistance of concrete for reinforced concrete sleepers based on the criteria of electric resistance, resistance to alkaline corrosion and corrosion due to the crystallization of delayed and secondary ettringite. This study was conducted within the framework of resolving the issue on premature destruction of reinforced-concrete sleepers caused by the progressing crack formation at the stage of heat treatment and subsequent operation. It has been established that the introduction of pozzolanic admixtures containing active Al 2 O 3 in their formulation to the composition of concrete for sleepers makes it possible to minimize the risk of corrosion predetermined by the reaction between aggregates' silica and alkali and corrosion as a result of crystallization of delayed and secondary ettringite. The high efficiency of pozzolanic admixtures containing active Al 2 O 3 regarding the specified types of corrosion is due to binding alkali into the insoluble alkaline hydroalumosilicates, contributing to the compaction of the system with a decrease in the content of Na + /K + ions in the solution. A decrease in the content of alkali in the porous solution predetermines blocking the «alkali-silica reaction» and increasing the temperature of ettringite stability to higher values. This reduces the potential number of secondary ettringite forming cycles and the probability of delayed ettringite formation. The alternative mechanism of action of active Al 2 O 3 on pozzolan implies binding the SO 4 2and Ca 2+ ions from a porous solution into low-sulfate forms of calcium hydro-sulfoaluminates, which excludes the crystallization of delayed and secondary ettringite.
Reducing the consumption of cement and water through the use of admixtures-plasticizers makes it possible to increase the electrical resistivity of the modified concrete for sleepers above the level of a control composition without admixtures. The obtained results provide an opportunity to ensure the design durability of concrete in reinforced-concrete sleepers through their comprehensive modification by plasticizers and active mineral admixtures that contain active Al 2 O 3 . The process of hot metal desulfurization by magnesium, reduced by the heat from exothermic reactions, has been investigated. Our research into the thermodynamics of magnesium oxide reduction in line with various protocols has established that it is in principle possible to reduce magnesium oxide by carbon, silicon, manganese, iron, and aluminum. We have calculated starting temperatures for MgO reduction by iron, manganese, silicon, aluminum, and carbon, which are 2,956, 2,546, 2,313, 1,585 and 1,875 °C, respectively. It has been determined that the most rational method to reduce magnesium oxide is the process based on binding the products of reduction into a CaAl 2 O 4 compound.
Based on the established rational conditions for magnesium oxide reduction, the exothermic mixture for hot metal desulfurization was calculated, %: MgO -15.0; FeO -56.0; CaO -7.0; Al -22.0. Experimental study has confirmed the most successful technical solution for the introduction of the calculated exothermic mixture to the melt aimed at desulfurization, which implies the application of a device for the introduction of active reagents into the melt, which is equipped with a chamber that collapses under the influence of the heat of liquid hot metal. Its use makes it possible to achieve the mean level of desulfurization of 65-70 %. We have performed, under industrial conditions, an experimental desulfurization of chromium hot metal using the designed exothermic mixture. According to the research conducted, the achieved degree of hot metal desulfurization in a ladle was at the level of 38 %; for the material of castings -at the level of 45.7 %. Thus, there is a reason to argue about resource and energy savings when applying the proposed technology for the outof-furnace hot metal desulfurization by reduced magnesium.
Keywords: out-of-furnace hot metal treatment, desulfurization, magnesium oxide, alumothermia, complex oxides, exothermic mixture. The data obtained significantly exceed the same indicators for a liquid glass at high shear rates, from 14 to 39 1/sec. For the adhesive with a composition of Na 2 O⋅Al 2 O 3 ⋅6SiO 2 ⋅20H 2 O, at low shear speeds there is a sharp increase in the shear effort, from 40 to 110 dyne cm 2 . This is due to the dispersion processes in the silica component. At an increase in the shear speed values from 5 to 42 1/sec, the shear effort increases from 110 to 158 dyne/cm 2 . This relates to the stabilization of viscosity values with the formation of a homogeneous adhesive structure.
Keywords: aluminosilicate adhesive, dynamic and plastic viscosity, surface tension, wetting angle, shear force, wood backing. It has been shown that significant reduction of «carbon trace» in construction technology is achieved by production of clinker-effective concretes based on composite Portland cements. Studies have shown that uneven distribution of grain fractions of the filler mix and their increased specific surface area lead to growth of water demand, stratification, bleeding in the concrete mix and a decrease in concrete strength. To achieve higher grain packing density, an approach based on optimizing particle size distribution in the concrete mix components was implemented. It was found that increased early strength of concretes based on low-emission composite cements is achieved by introduction of polycarboxylate (PCE) superplasticizers and alkaline-sulfate activation. To establish connection between environmental and technical properties of concretes, clinker efficiency in concrete was determined. An increase in strength of modified concrete based on composite Portland cement CEM II/B-M 32.5 R (clinker factor 0.65) create the possibility for a significant reduction of specific consumption of clinker per unit strength, up to 4.5…3.0 kg/(m 3 ⋅MPa); accordingly, CO 2 intensity 3.9...2.6 kg CO 2 /(m 3 ⋅MPa). Significant intensification of the processes of early structure formation in nanomodified clinker-efficient concretes is ensured by a comprehensive approach: optimization of the component mix, introduction of the PCE superplasticizer and nanomodifiers. Using the laser diffraction method, it was proved that main contribution to development of specific surface of the nanomodified cementing matrix is made by ultrathin particles (K isa = 761.2 µm -1 vol. %) of nano-SiO 2 . It was established that synergistic combination of mineral additives in composite Portland cement and complex nano-SiO 2 +C-S-H-PCE nanomodifier provide increased early strength (after 12 hours -R c = 6.4 MPa) and obtaining rapid hardening concrete class C50/60 (f cm2 /f cm28 = 0.51). Thus, there are reasons to argue that it is advisable to develop nanomodified clinker-efficient concretes in order to ensure rapid construction and solve problems connected with necessity of implementation of a strategy of low-carbon development.
Keywords: clinker-effective concrete, composite Portland cement, polycarboxylate type superplasticizer, alkaline activator, nanosilica, early strength, CO 2 emission index. An innovative technology of complex hydrogen and thermobaric chemical effects (CHTBCE) on the productive formation of oil (gas) wells has been developed with the aim of stimulating hydrocarbon recovery. The basis of this technology is the integrated use of the anomalous properties of hydrogen under the conditions of a multistage thermal-gas-chemical chemical-technological process (CTP). Improving the effectiveness of the technology requires a significant improvement in the controllability of the underlying CTP.