Structure and Charge States of the Selected Hydrogenated Silicon Clusters Si2-Si8 by Non-Conventional Tight-Binding Method

Structures of SinHm clusters in neutral, positive and double positive charge states have been calculated by nonconventional tight-binding method and molecular dynamics. An influence of the charge state and the termination by hydrogen of dangling bonds on cluster structures those are obtained as a result of chemical vapor precipitation in silane, is considered for the first time. Fully hydrogenated clusters have tetrahedral branched structures. Other isomers have forms of closed circles

Nanosize Structures and Energy Parameters of Doped Silicon Clusters Passivated by Hydrogen

The paper considers the computer model of silicon clusters doped with boron and phosphorus, and the effect of hydrogen on their structure and energy parameters. While calculating nanostructure formation, the model assumes hydrogenated Si29 clusters with substitution of a matrice atom with B and P impurities and insertion of one or some hydrogen atoms. Nanostructured defect complexes of Si-P-H or Si-B-H are suggested to be formed under hudrogen insertion, with their stability depending on the hydrogen atom number and the dopant type. Computer modelling and optimization calculations were carried out in the frame of nonempyrical modelling methods for structure and properties of multiparticle systems - ORCA under the approximation of local electron state density

Effect of chitosan on the surface properties of cellulose-based paper obtained from the flax plant

The effects of chitosan, starch, and polyvinyl alcohol (PVA) were studied to improve the surface properties of cellulose-based paper obtained from local raw materials. Polymers are incorporated into the paper canvas by spraying. The results showed that the addition of chitosan to paper webs made from cellulose fibers has improved surface properties compared to the effects of other additives. The effect level of starch was similar to that of chitosan, but it resulted in a lower water absorption potential of paper than chitosan at the same concentration. In many other properties, particularly for printing papers, the most important property being surface smoothness, chitosan treated papers are superior to starch or PVA treated papers

Solution Properties of New Biosurfactants and Their Effect on The Modification of Surfaces

<p>Biosurfactants are surface active amphiphilic compounds of biological origin and produced by many different microorganisms. The microorganisms including bacteria, fungi and algae are the most efficient organisms at producing biosurfactants. The biosurfactants offer many advantages compared to the synthetic surfactants: they are environmentally friendly, have useful properties including bioavailability, biodegradability, activity under extreme conditions, low toxicity and structural diversity. The purpose of this work was obtaining new biosurfactants from microorganisms, investigating the colloid-chemical properties of new biosurfactants, the efficiency of biosurfactants water solutions on wettability of different surfaces and establishing correlations between colloid-chemical properties of new surfactants. The modern methods for determining the colloid-chemical and solution properties of biosurfactants were used in the work. The contact angles of biosurfactant water solutions on different hydrophilic and hydrophobic surfaces were investigated. It has been established that the contact angles of biosurfactant water solutions on the hydrophilic surfaces (aluminum, copper, steel, glass) significantly depends on the composition and structure of biosurfactant molecules. It has been shown, that the compositions with low biosurfactant concentrations have higher contact angles and the hydrophobization of aluminum, copper, steel and glass surfaces takes place. At high biosurfactant concentrations, the contact angles sharply decreased due to the fact that during adsorption, the biosurfactant molecules oriented by the polar groups to the surfaces. The concentration dependence of the contact angle passes through a minimum only for hydrophilic surfaces aluminum, copper, steel and glass as a monolayer of surfactant molecules was formed on the hydrophilic surface with orientation by polar groups to the solid surface. It has been established that the increase in the cosine of the contact angle at higher biosurfactant concentrations was associated with the hydrophilization of the hydrophilic surfaces due to the formation of micelles on hydrophilic surfaces. For a hydrophobic surfaces, such as polyethylene, plexiglass and paraffin, the cosine of the contact angle increased monotonically with the increase in the biosurfactant concentration. It has been established that the effect of the biosurfactant structure on the adsorptive modification of surfaces occurs only at low biosurfactant concentrations by the formation of a monolayer.</p&gt

STUDY OF THE PROPERTIES AND EFFECT OF NEW SURFACTANTS IN CEMENT SLURRY’S STRUCTURE FORMATION

Surface-active agents (surfactants) are widely used to improve the quality of materials and control technological processes. In this regard, a very urgent problem is the study new surfactants and creation of new compositions to improve the rheological and structure-forming properties of dispersed systems and cement slurries. To effectively solve this problem, it is necessary to investigate new surfactants in disperse systems. The purpose of this work was the study colloid-chemical properties of new surface-active derivatives of maleic acid and effectiveness for regulating structure formation in cement suspensions. Different methods for the measurements of properties and efficiency of new surfactants were used. New surfactants based on maleic acid derivatives with different numbers of ethoxy groups and carbon atoms in the alkyl chain were investigated. The obtained experimental data and correlations based on them showed that the colloid-chemical properties of the studied surfactants are closely related to the structure of their molecules. It was established that new surface-active derivatives of maleic acid are effective regulators of the structure formation of cement dispersed systems. It was shown that the introduction of new surfactants in combination with marble powder enhances the plasticizing effect and makes it possible to replace part of the binder with marble powder without reducing the final strength of the cement stone. It has been established that with an increase in the number of ethoxy groups in the molecule and the length of the carbohydrate chain, the surface activity and foaming ability of new surfactants increase. The use of modified marble powder with aqueous solutions of surfactants, lengthens the stage of initial structure formation and accelerates the subsequent process of structure formation with an increase in the daily strength of the cement stone

Вивчення впорядкованих структур і фазових переходів субкарбіда ванадіюметодом дифракції нейтронів

The results of neutron diffraction study of VC0.47 are presented and discussed. It is established scheme of the phase transitions. A low temperature orthorhombic ordered phase (space group Pbcn) and high temperature hexagonal ordered phase (space group P6322) exists in VC0.47. The kinetic of the transition is described by Kolmogorov – Johnson – Mehl – Avrami law. При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/30972Подані та проаналізовані результати дифракції нейтронів на зразках VC0.47. Установлені схеми реалізації фазових переходів. Виявлено існування низькотемпературної ромбічної впорядкованої фази просторової групи Pbcn і високотемпературної впорядкованої гексагональної фази просторової групи P6322. Показано, що кінетичний перехід описується законом Колмогорова-Джонсона-Мель-Аврамі. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/30972Представлены и проанализированы результаты дифракции нейтронов на образцах VC0.47. Установлены схемы реализации фазовых переходов. Обнаружено существование низкотемпературной ромбической упорядоченной фазы пространственной группы Pbcn и высокотемпературной упорядоченной гексагональной фазы пространственной группы P6322. Показано, что кинетический переход описывается законом Колмогорова-Джонсона-Мель-Аврами. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3097