Investigation Into Acid­basic Equilibrium on the Surface of Oxides with Various Chemical Nature

The acid-base equilibrium on the surface of CaO, MgO, FeO, Al2O3, Fe2O3, SiO2, TiO2 oxides was studied. As a result of the study, the main provisions have been formulated which made it possible to propose models of surface active centers and schemes of their acid-base equilibrium. The acid-base and energy equilibrium parameters of the active centers in the deprotonation reactions were calculated. Regularities of changes in the acid-base and energy parameters of the active centers were determined depending on the nature of the central element of the crystal lattice, the number of OH-groups and the number of hydration. Acidity of all considered types of active centers depends to a large extent on the nature of the central element, namely its charge and coordination number. It was found that with increase in the coordination number of the central elements with the same charge, pKa of anhydrous centers and the value of their Gibbs free energy in deprotonation reactions increase. Acidity of isolated anhydrous centers increases in a direct proportion as the number of OH groups increases. The obtained regularity preserves for the surfaces of all oxides considered. It was shown for all oxides that when the amount of adsorbed water molecules increases, acidity of the active centers of all types increases and this dependence is identical to the growth of acidity with an increase in the number of OH groups. This indicates identity of the nature of acidity growth with an increase in thickness of hydroxyl and hydration surface layers. The obtained results will ensure prediction of oxide filler behavior in compositions and adjustment of operating properties of composite material

Analysis of Correlation Dimensionality of the State of a Gas Medium at Early Ignition of Materials

We have considered the application of the method of nonlinear dynamic systems in order to analyze and detect the structural patterns in the dynamics of increments in the state of a gas medium generated by early ignitions of materials in a non-sealed chamber. The research method is based on analysis of the correlation dimensionality of increments in the state of a gas medium during ignition of materials. We have theoretically justified the method for evaluating the dynamics of correlation dimensionality of increments in the state of a gas medium at ignition. The considered method for CD evaluation is based on the computation of the Grassberger-Procaccia correlation integral, applied to the gas medium state increments using a sliding window with a fixed width. That allowed us to derive a current estimate of CD increments in the state of the gas medium during ignition of flammable materials in a chamber synchronized with the observation data acquisition rate. We have analyzed the dynamics of correlation dimensionality of increments in the state of a gas medium at early ignition of alcohol, paper, wood, and textiles in a simulation chamber. It was established that for the investigated state of the gas medium during ignition of various examined materials, the dynamics of correlation dimensionality is within 0.1 to 0.6. It is noted that this fact testifies to the fractal structure of the considered increments in the state of a gas medium in a chamber and its chaotic dynamics at the emergence of ignition sites of tested materials. In this case, the fractal structure is not the same, suggesting a "transitional chaos" in the examined state of the gas medium. It was established that current estimates of the correlation dimensionality of increments in the state at the time of materials ignition tend to a sharp increase. A given fact can be used to reliably detect early fires indoors. The results obtained are important for the in-depth studying and understanding of patterns in the structure of dynamics of increments in the state of a gas medium at early ignition. It has been shown the increments in the states of a gas medium at premises characterize it as a chaotic dynamic system with a small fractal dimensionality as opposed to the traditional approach assuming a gas medium being either deterministic or random syste

Research of the Intramolecular Interactions and Structure in Epoxyamine Composites with Dispersed Oxides

With the help of the software package HyprChem, using a method of quantum-chemical modeling, research into intermolecular interactions between epoxyamine grid and oxides of different chemical nature Al2O3, Fe2O3, TiO2, СаО was carried out. To take into account hydroxyl-hydrate surface layer of oxides, molecular complexes of the fragment of epoxyamine grid and hydroxides of metals Al(OH)3, Fe(OH)3, Ti(OH)4, Ca(OH)2 were used as models. As a result of modeling, it was established that Ca(OH)2 molecule forms strong intermolecular bonds and has the greatest influence on the spatial conformation of the epoxyamine fragment. It was shown that a calcium atom is oriented to π-electron cloud of the benzene ring with formation of donor-acceptor bond, and OH-groups form hydrogen bonds with OH-groups of the residue of a molecule of epoxy oligomer in the grid. The studied intermolecular interactions of epoxyamine grid and hydroxides of amphoteric metals Al(OH)3, Fe(OH)3, Ti(OH)4 indicate the formation of low-energy inductive and dipole-dipole (orientation) bonds. It was established that existence of amphoteric hydroxides does not cause a change of the spatial conformation of the grid's fragment. It was shown that the ability of hydroxides of metals to affect the spatial conformation of a fragment of the epoxyamine grid increases in the series: Ti(OH)3<Al(OH)3<Fe(OH)3<Ca(OH)2. The resulting series coincides with the series, in which basic properties of active Branstad centers (OH-groups) with the central elements Ti4+<Al3+<Fe3+<Ca2+ increase (acidic properties decrease). The influence of the oxide filler on the structure and spatial conformation of epoxyamine grid increases with an increase of basicity (alkalinity) of an oxide. Resistance of composites to aqueous aggressive media depends on the surface acidic-basic properties, dispersion and package density of fillers' particles in the polymer matrix. When adding strongly basic calcite oxide (CL), chemical resistance of composites decreases by 5 times. In this case, composites with non-homogeneous structure and non-uniform distribution of compacted areas are formed. It was found that when adding amphoteric rutile oxides (RT), alumina (AL) and hematite (HM), the main factors that affect chemical resistance of filled composites include dispersion and package density of fillers' particles. The calculated parameter a of composites, which describes package density of the filler in the polymer matrix, increases in the series of fillers HM<RT<AL. This series coincides with the series, in which resistance of filled composites in all aggressive media decreases. At an increase in package density of a filler, probability of pegridration of aggressive medium into the material decreases, which is associated with extension of the diffusion path

Research Into Surface Properties of Disperse Fillers Based on Plant Raw Materials

The properties of the dispersed fillers are investigated based on the agricultural and wood industry wastes: buckwheat and oats husk, wood and pine­needle flour. We experimentally determined structural­rheological characteristics, morphology and acid­base properties of the surface. By applying a potentiometric determining of hydrogen indicator of aqueous suspensions рНsusp., we studied the qualitative and quantitative characteristics of acid­base active centers on the surface of the particles of fillers. It was revealed that the surface of buckwheat husk is dominated by two types of active centers: weakly­acidic (рKа≈5.53–5.83) and close to neutral (рKа≈6.16–6.30). The surfaces of wood flour and pine­needle flour are characterized as the weakly­acidic with centers рKа≈5.29–5.52 and рKа≈5.02–5.36, respectively. Based on sources from the scientific literature, we compiled a comparative characteristic of the chemical composition of the examined fillers. A correlation is established between chemical composition, physical­chemical and surface properties. It is shown that the total mass content of cellulose and lignin can be one of the criteria for evaluating resistance of the fillers to high temperatures and acidic­base properties. A decrease in the sum of mass content of cellulose and lignin in the composition of fillers results in the improved thermal resistance while the surface acidity decreases. The results obtained allow us to predict behaviour of the fillers in compositions and control performance characteristics of composite materials

Study of the Free Surface Energy of Epoxy Composites Using an Automated Measurement System

Results of development of the automated measurement system (AMS) for determining contact wetting angles and calculations of components of free surface energy (FSE) of solid surfaces by the Van Oss-Chaudhury-Good method were presented. It was shown that AMS allows for calculations based on experimental measurement of geometrical parameters of a lying drop on the surface and energy characteristics of test fluids. It was found that the measured contact wetting angles and calculated values of FSE components of surfaces of epoxy polymer composites, steel and glass are adequate and reliable.Based on the conducted measurements and calculations, relationship between FSE, the structure and properties of epoxy polymer composites, filled with rutile, was established. In the course of research that was conducted using AMS, it was found that at an increase of the content of rutile, total FSE (γs), dispersive (γd) and acidic-basic (γab) components of composites increase. Dependences γs and γd on the filler's content are extreme in character, and γab increases and does not change at a subsequent increase in the amount of rutile. The influence of rutile is represented most vividly by dependences of the acidic (γa) and basic (γb) components, into which the polar (acidic-basic) FSE component γab is disintegrated. It was found that structural transformations are associated with the acidic-basic mechanism of intermolecular and inter-phase interactions in epoxy composition

Construction of the Method for Semi-adaptive Threshold Scaling Transformation When Computing Recurrent Plots

A method has been constructed for the threshold semi-adaptive scaling transformation. The method provides calculation of recurrent plots, which adequately map the dynamics of real complex dynamic systems in natural and technical spheres. A new scientific result implies the development of theoretical basis for the method of semi-adaptive scaling transformation of the threshold during calculation of recurrent plots by improvement of linear normalized spaces due to introduction of a scalar product of vectors. The proposed method of threshold transformation provides computation of recurrent plots with increased information content, invariance to parameters of measured state vectors, and irregularity of measurements. We performed tests of operability of the proposed method of semi-adaptive scaling transformation of the threshold based on experimental measurements of concentrations of formaldehyde, ammonia, and carbon monoxide in atmospheric air in a typical industrial city with conventional stationary and mobile sources of pollution.Taking into account the proposed method of semi-adaptive scaling transformation, the obtained results of the calculation of recurrent plots confirmed its operability in general. It was found that the calculation of RP during the semi-adaptive transformation of the threshold for various α angular dimensions of a recurrence cone, equal to 1°, 5°, 10°, and 20°, indicates that accuracy of recurrent plots in detection of dangerous states in dynamic systems increases with a decrease in angular dimensions of a cone. It was established experimentally that the values of angular dimensions of the recurrence cone should be 1–5° for adequate mapping of recurrent states of real dynamic systems with the use of calculated recurrent plot

Mathematical Model of Determining A Risk to the Human Health Along with the Detection of Hazardous States of Urban Atmosphere Pollution Based on Measuring the Current Concentrations of Pollutants

A mathematical model of joint determining the risk to human health and the identification of hazardous states of the polluted urban atmosphere based on the measurement of current concentrations of pollutants was developed. The structure of the model includes two structural units. The input data for structural units are the results of measuring current concentrations of atmospheric pollutants at a checkpoint. The current risk to human health is calculated in the first unit, and recurrent states of atmosphere for early detection of dangerous pollution levels are determined in the second unit. A distinctive feature of the model is the use of only measurements of current concentrations of pollutants in the atmosphere at a control point. Meteorological or other information is not used. That is why the developed model is universal and can be used in any weather conditions and peculiarities of the urban infrastructure. The operation efficiency of the proposed model was tested experimentally using the example of measuring current concentrations of formaldehyde, nitrogen dioxide, and ammonia in the atmosphere of the typical urban infrastructure. It was established that the developed model makes it possible to determine the risk of immediate toxic effects and chronic intoxication for humans, caused by atmospheric pollution. It was proved experimentally that the proposed model makes it possible, together with the identification of relevant risks to human health, to detect hazardous states of the polluted atmosphere, in which pollutants are usually accumulated. It was established that determining the current probability of recurrent conditions of the polluted atmosphere makes it possible with various reliability degrees to detect the possible occurrence of negative effects of atmospheric pollution on human health 6–12 hours beforehan

Development of the Correlation Method for Operative Detection of Recurrent States

The correlation method for operative detection of recurrent states in complex dynamical systems at irregular measurements was proposed. The concepts of correlation for the case of the vectors of states of the trajectory of dynamics of complex systems and estimates of vectors correlation for a fixed length fragment moving along the trajectory were generalized. The space with scalar product of states vectors is used to implement the method. Estimation of the magnitudes of correlations of state vectors makes it possible to interpret them as corresponding levels of energy interaction of states vectors and to detect degree of their recurrence. In this case, calculation of the magnitudes of correlation are carried out only based on the known measurements of the state vector and does not require determining the threshold and the method of distance calculation, traditionally used in the methods of recurrent plots. The efficiency of the proposed method was tested on a specific example of experimental data of the actual dynamics of the vector of states of pollution of the urban atmosphere. The following gas pollutants were considered as components of the vector of state: formaldehyde, ammonia and carbon dioxide. The obtained results in general indicate the efficiency of the proposed method. It was established experimentally that the correlation method in case of irregular measurements of atmospheric contaminations ensures the authenticity of detection of recurrent states, corresponding to maximum correlation of states. In this case, the correlation assessment should be conducted for a movable fragment of a trajectory of the states vector. The length of the fragment should not be more than 10 response