Dielectric and electrical properties of nematic liquid crystals 6CB doped with iron oxide nanoparticles. The combined effect of nanodopant concentration and cell thickness

Dispersing nanomaterials in liquid crystals has emerged as a very promising non-synthetic way to produce advanced multifunctional and tunable materials. As a rule, dielectric and electrical characterization of such materials is performed using cells of single thickness. As a result, the published reports vary even for similar systems. Confusion still exists as to the effects of nanodopants and cell thickness on the dielectric and electrical properties of liquid crystals. This factor hinders a widespread use of liquid crystals – nanoparticles systems in modern tech products. In this paper, we report systematic experimental studies of the combined effect of the cell thickness and iron oxide nanoparticle concentration on the electrical and dielectric properties of nematic liquid crystals 6CB. The measured dielectric spectra can be divided into three distinct regions corresponding to a low frequency (<10 Hz) dispersion, dispersion free range (102 - 104 Hz (electrical conductivity) and 102 - 105 (dielectric permittivity)), and high frequency dispersion (104 - 106 Hz (electrical conductivity) and 105 - 106 Hz (dielectric permittivity)). The real part of the dielectric permittivity is not affected by the cell thickness and its value can be tuned by changing the concentration of nanoparticles. At the same time, the electrical conductivity depends on both cell thickness and nanoparticle concentration. At intermediate frequencies (102 - 104 Hz) the electrical conductivity obeys the Jonscher power law and is dependent on the cell thickness because of ion-releasing and ioncapturing effects caused by nanoparticles and substrates of the cell. In addition, its value is affected by the electronic conductivity due to iron oxide nanoparticles and their nanoclusters. At higher frequencies (104 - 106 Hz) the electrical conductivity follows a super linear power law and is nearly independent of the cell thickness and nanoparticle concentration

Природно-заповідна мережа Волинської області: параметри сучасного стану, показники динаміки, картографічні моделі

У статті відображено результати дослідження природно-заповідного фонду Волинської області: його структуру, коефіцієнт заповідності, коефіцієнт інсуляризованості, особливості просторової локалізації природоохоронних територій. Створено картографічні моделі, які відображають параметри сучасного стану природно-заповідного фонду досліджуваного регіону.The article presents research results of Volyn region natural preservation fund, its structure, reserve’s coefficient, insularization rate, space location of the conserved territories. The cartographic models have been created that show the present state parameters of considerated region natural preservation fund

колективна монографія

Кримінальний процесуальний кодекс 2012 року: ідеологія та практика правозастосування: колективна монографія / за заг. ред. Ю. П. Аленіна ; відпов. за вип. І. В. Гловюк. - Одеса : Видавничий дім «Гельветика», 2018. - 1148 с

Studying the Influence of Metakaolin on Self-healing Processes in the Contact-zone Structure of Concretes Based on the Alkali-activated Portland Cement

This paper reports results from comparative testing the reaction "alkali ‒ active silica" in traditional Portland cement and alkaline Portland cement with the addition of metakaolin. The research is based on studying the process of structure formation in cements in the contact zone "cement stone – basalt".The research results allow us to conclude that the dynamics of the process of interaction of the reaction "alkali‒silica" in cements may be constructive and destructive in character. That depends on the content of components that are able to actively interact with alkalis in the presence of reactive silica. The so-called "constructive" processes are accompanied by the binding of corrosion products during the formation of alkaline hydroalumosilicates. The research results were used as the basis for developing the mechanism of preventing the reaction "alkali – active aggregate" in concretes based on alkaline cement by introducing to the cement composition additional amounts of materials containing active aluminum, in particular, metakaolin.Our study has shown that the introduction of a metakaolin additive could effectively control the processes of structure formation in the contact area "cement stone – active silica", thereby changing the character of new structures. The mechanism of an alkaline corrosion process of an active aggregate in the presence of metakaolin has been established, according to which metakaolin enters the reaction at a rate of microsilica, providing for a very Fast binding of the Na+ and K+ ions. Silicate gel of alkaline metals binds into insoluble zeolite-like new structures and hybrid hydroalumosilicates. As resilient structures, the latter condense and strengthen the contact area by enhancing its microhardness and strength.We have investigated the natural shrinkage deformations (expansion) of the developed compositions of concretes based on the traditional and alkaline Portland cements. It has been shown that the introduction of a metakaolin additive to the system formulation makes it possible to reduce the system expansion indicators from 0.44 to 0.01 mm/m, thereby maintaining the defect-free structure of cement stone and concrete and improving the durability of concret

A Comparative Study on the Influence of Metakaolin and Kaolin Additives on Properties and Structure of the Alkali­activated Slag Cement and Concrete

The influence of the metakaolin and kaolin additives on the formation and properties of the alkali-activated slag cements and concretes was studied.The influence of the metakaolin and kaolin additives on macro- and microstructure formation of the cements and concretes was studied.A conclusion was drawn that the processes of microstructure formation of the cement stone with the additive flow in a similar sequence but with different intensity. A conclusion was drawn that the addition of the kaolin instead of metakaolin affected as follows: 2.5–10 % by mass reduced the value of NCP by 9.5–8.7 %, respectively; 2.5–5 % by mass did not affect setting times, but with increase up to 10 % by mass the initial setting time was shorter (from 48 min to 40 min); 2.5–5 % by mass did not affect compressive strength at all stages of hardening, but with increase up to 10 % by mass reduced strength characteristics of the cement-sand specimens (from 57.0 MPa to 49.0 MPa).In case of the addition of 5 % kaolin by mass, an optimal macrostructure of the concrete is formed in which the quantities of the ''conditionally'' closed pores are by 17.7 % higher compared to those of the concretes with the same quantities of the metakaolin. This resulted in the higher freeze/thaw resistance of the concrete (from F400 up to F500). Based on the comparison of properties and structure of the cement and concrete containing the kaolin and metakaolin additives, a possibility to substitute metakaolin by kaolin as a correcting additive was established

Alkali Activated Concretes Mix Design Using Red Mud as an Active Aggregate

The object of the study is compositions of common alkali activated concretes using red mud as an active aggregate. The main problem when working with red mud is its chemical composition and high specific surface area, which quite negatively affect the properties of building materials.The study used modern methods of physico-chemical analysis to obtain results. Determination of physical-mechanical and special (strength, frost, carbonation, corrosion resistance, radiation resistance, durability, own shrinkage deformation) properties of the tested concrete mixtures and alkaline concretes with high red mud content were carried out according to standard methods. The world's experience in dealing with red mud is also taken into account.Optimal indices of the functional properties of concrete with the use of red mud have been obtained, which makes it possible to confirm the durability and environmental friendliness of such material. This is due to the fact that the reliability of the immobilization of alkaline concretes meets the requirements of the standard, which indicates that the concretes developed are environmentally friendly.Radiation resistance of alkaline concretes based on red mud is conducted and it is determined that this concrete with a mud content of up to 40 % (by weight of concrete) belongs to Class I according to the classification of building materials and can be used for all types of construction without restrictions.This provides an opportunity to expand the nomenclature of building materials and obtain a completely new product made on the basis of man-made raw materials, which significantly reduces the price and increases the demand for products. Especially in comparison with other similar products made on natural raw materials

Influence of Aeration Rate and Method of Process Activation on the Degree of Purification of Zinc-containing Waste Water by Ferritization

The aeration rate for the degree of purification of highly concentrated galvanic wastewater from zinc and ferrum ions was investigated using various activation methods. It is shown that the intensity of aeration has a significant effect on the quality of wastewater treatment and the characteristics of water treatment sludge. The efficiency of the use of an energy-saving method for activating the ferritization process with the use of electromagnetic pulses for the extraction of zinc ions from wastewater has been confirmed. It was determined that with an increase in the aeration rate to 3.5 dm3/min per 1 dm3 of the reaction mixture and the use of thermal activation of the process, the residual concentration of zinc ions remains within the range of 0.12÷0.2 mg/dm3. In this case, the concentration of ferrum ions decreases to values of 0.08÷0.14 mg/dm3. It was found that at an aeration rate of 2.5 dm3/min and the use of pulsed electromagnetic (EMP) activation, the residual concentrations of heavy metal ions decrease to values of 0.08÷0.16 mg/dm3. Comparison of the results indicates the advisability of using low rates of aeration of the reaction mixture. This, together with the use of resource-saving EMR process activation, allows to achieve a significant reduction in energy costs. The quantitative phase composition of ferritization precipitates was determined, in which the crystalline phases of zinc ferrite Zn2Fe2O4 and magnetite Fe3O4, as well as ferrum oxyhydroxide FeO (OH) and sodium sulfate Na2SO4, prevail. It is found that with an increase in the volumetric aeration rate, the proportion of the ferrite phase increases. At an aeration rate of 2.0 dm3/min, more than 85 % of the zinc ferrite phase was found in the sediments. Taking into account the qualitative and quantitative composition of precipitates, it is recommended to use them in the production of building materials. The experimental results obtained make it possible to provide a comprehensive processing of liquid galvanic waste

Research of the Treatment of Depleted Nickel­plating Electrolytes by the Ferritization Method

Considerable attention has been paid recently to the development of comprehensive recycling of industrial wastewater, which provides for an appropriate degree of purification for both organization of circulation water supply, and subsequent disposal of waste of water treatment. The improved ferritization process, which allows decreasing original concentration of nickel ions in depleted electrolytes of nickel plating from 50–100 g/dm3 to &lt;0.2 mg/dm3, was presented. The experimental ferrite-reactor with the use of the traditional thermal and electromagnetic pulse method of activation of ferritization process in the range of generating frequencies of up to 0.9 kHz was developed. Economic benefits of the use of the electromagnetic pulse activation compared to the high temperature one were identified. Kinetics of extraction of nickel and iron ions from aqueous solutions was explored. The impact of the basic technological parameters of ferritization at different ways of activation was experimentally determined. The most effective results of treatment of highly concentrated wastewater were achieved using the electromagnetic pulse (T=20 °C) and thermal (T=70 °C) way of activation of the ferritization process at the original ration of concentration Fe2+/Ni2+ within 3/1–4/1, total concentration of ions of heavy metals of 20–25 g/dm3, original pH of the reaction mixture of 9.5 and duration of ferritization process of 15 min. Research into phase composition and physical properties of ferritization sediments was performed. Comparative analysis of sediment volumes at different ways of compaction was carried out. Sediments are mainly characterized by the crystalline structure, ferromagnetic properties, and considerable chemical resistance. This provides for actual environmental ways of recycling, which makes it possible to avoid the loss of valuable and, at the same time, toxic metal – nickel. The proposed comprehensive process of recycling liquid industrial waste prevents pollution of the environment, ensures effective and efficient use of water, raw materials, and power in the system of galvanic production