Two-component Liquid Systems Research Articles

Bio-Stimulated Surface Healing of Historical and Compatible Conservation Mortars.

The main focus of this research was the bio-stimulated healing of cracks in lime mortar samples (historical and newly designed). The investigation started from comprehensive characterisation of historical mortars, while in the next stage a compatible conservation mortar was designed and characterised, with special attention given to the contact zone formation between original and conservation mortars. The next step was the design of a bio-stimulating crack-sealing agent, a two-component liquid system: bacteria culture Sporosarcina pasteurii DSM 33 and nutrients. Both historical and conservation mortar samples were used in order to study their potentials for bio-stimulated surface-crack repair. The experiment lasted for 150 days, allowing the ureolytic bacteria Sporosarcina pasteurii DSM 33 to induce the precipitation of calcium carbonate into cracks and heal the damaged surface of the tested materials. The healing phenomenon was continuously monitored during a period of 150 days. Special attention was given to the evaluation of the morphology, chemical and structural characteristics of the deposits created in/on the surface cracks, monitored by optical microscopy, SEM, XRF and XRD analyses. The obtained results present valuable input for the application of the developed system in real environmental conditions as a solution for the future sustainable architectural conservation of traditionally prepared mortars.

Functional mortars for conservation of cultural heritage structures

Mortar aging and deterioration are serious problem for architectural heritage conservation. The solution might be sought in advanced functional materials which could provide repair and lasting surface protection from atmospheric pollution and microbiological corrosion. In recent years, extensive studies have been conducted on the use of bacteria with biocalcification potential for self-healing effect in cements materials, but only a few publications deal with self-healing capacity of historical lime-based mortars.The main focus of our research was development of new bio-activated self-healing system and its application in laboratory conditions. The objects of the work were historical mortar samples from medieval Bač Fortress in Serbia and laboratory prepared and aged mortar models. Aiming to achieve high compatibility, laboratory models were prepared based on our previous results of historical mortars characterization. The bio-activated self-healing agent was made as two-component liquid system using bacterial cells of Sporosarcina pasteurii DSM 33 and nutrients. The components of the models were hydraulic lime, milled limestone, river sand, and crashed brick as aggregates, and water. Comparative characterization of historic mortars and aged models was performed by mechanical and colorimetric testing as well as examination of mutual interaction and cohesion between old and new material.The next step was efficiency evaluation of the external bacteria-based repair healing method in/on the laboratory samples. The detailed study of the cracks of the historical samples and the prepared models, and the bacterial suspension diffusion assessment were done by comparison of the results obtained by different complementary imaging techniques (optical and scanning electron microscopy). The experiments were performed on both samples of old and new materials treated with and without bio-activated self-healing agent.The obtained results are promising and support the development of the external bio-activated self-healing method. This solution represents functional system which could allow historical mortars and modern structures to heal themselves in the long-term, preserving their functional and aesthetic properties.

Intensification of Fast Chemical Processes at Interfaces of Two-Component Liquid Media in Tubular Turbulent Reactors

The possibility of intensifying fast chemical processes at the interface of two-component liquid medium in a tubular turbulent reactor has been considered. A new application of the turbulent reactor for processes occurring at interfaces in two-component liquid systems has been found. It has been observed that the chemical reaction time abruptly decreases, and the physics of the process affects the direction of and conversion in the chemical reaction at a high (up to 100%) yield of desired products. The geometric characteristics of the reactor have been analyzed, and it has been shown that the dispersion of drops in the emulsion is most efficient at large angles of inclination of an obstruction to the flow and at minimal gaps in the convergent-divergent channel of the reactor. It has been demonstrated that the average perimeter of drops of the dispersion oscillates with time, which causes elongation and breakup of drops. In its turn, the latter influences the contact surface area of the emulsion and, significantly, the chemical reaction rate.

Layering in a two-component liquid system undergoing a phase separation

The phase change possibilities in the surface phase formed in a binary liquid system (water 2,5dimethylpyridine) in contact with a solid (silica) have been examined on the basis of adsorption isotherms determined at ten different temperatures. The liquid mixture undergoes a liquid–liquid demixing but also, some 20° below the critical point, a solid phase separation. On the l.h.s. of a liquid–liquid coexistence curve 2,5dimethylpyridine, diluted in water, adsorbs step by step, and on the r.h.s. the relative adsorption is wave shaped. Both behaviors can be explained by a layering process, i.e., a solid–liquid surface demixing, which unexpectedly does not exclude a separate liquid–liquid surface demixing, which could constitute the prewetting process. This analysis is compared with known theories and its consistency is carefully checked on a thermodynamical basis.

Soret coefficient of isotopic Lennard-Jones mixtures and the Ar-Kr system as determined by equilibrium molecular-dynamics calculations.

The Soret coefficient (thermal diffusion coefficient) characterizing the coupling between heat and mass transport in more-component systems has been obtained by equilibrium molecular dynamics. Two-component liquid systems of the Lennard-Jones type were considered: three isotopic mixtures and Ar-Kr. Computations 20 times longer than the ones used for a ``usual'' transport coefficient, as the thermal conductivity, were necessary to obtain this cross coefficient with modest accuracy. The analysis of the Green-Kubo integrand shows that, opposite to the thermal conductivity, the thermal diffusion depends strongly on the terms containing the partial enthalpies of the components. For the isotopic mixtures, it was found that the Soret coefficient grows with the mass ratio in a way consistent with experimental results. For the Ar-Kr system, direct comparisons with nonequilibrium molecular-dynamics data indicated good agreement. As experimental Soret coefficients for Ar-Kr are lacking, we cannot compare our results with data of the real mixture. The order of magnitude found agrees, however, with that experimentally observed for binary liquid mixtures.

A simple theory to predict small changes in volume and refractivity during mixing of a two-component liquid system

A presentation of a simple theory to predict small changes in volume and refractivity during mixing of a two-component liquid system.

The Solution of the Tracer Diffusion Equation in a Two-Component Liquid System

The Solution of the Tracer Diffusion Equation in a Two-Component Liquid System

Rough hard spheres treatment of tracer diffusion of each component in two-component liquid systems

The rough hard spheres treatment of diffusion is extended to cover tracer diffusion of both species in five two-component organic liquid systems. Self-consistent results are obtained for the factor expressing coupling of translational-rotational motion and reasonable agreement is found where comparisons can be made with mutual diffusion data.

Plait Points in Two- and Three-Component Liquid Mixtures

It is pointed out that the plait-point (isothermal critical-mixing-point) phenomenon in a three-component liquid system of fixed pressure and temperature is identical in character to that in a two-component liquid system of fixed temperature but variable pressure. A lattice-gas model of a two-component liquid system is described. The intermolecular forces are all postulated to be infinitely strong repulsions, as between hard cores, but the model system nevertheless undergoes first-order phase transitions with an associated plait point. The behavior of the system with varying densities ρ1 and ρ2 of its two components, at fixed temperature, is shown to be exactly transcribable, with only a change of language, from the behavior of a reference one-component lattice gas of varying density and temperature, in which the interaction between neighboring molecules is attractive. The critical point of the reference one-component system is mapped into a plait point in the isothermal ρ1, ρ2 plane of the binary system. The two-phase coexistence curve (binodal curve) in the isothermal ρ1, ρ2 plane of the binary system is found to be of algebraic degree (1—α′)/β near the plait point, where α′ and 1/β are the index of the divergence of the constant-volume specific heat in the two-phase region of the reference system, and the algebraic degree of the reference system's temperature—density coexistence curve, respectively. Fluctuations in ρ1 and ρ2 in the one-phase region of the binary system are found to diverge as the —γ/(1—α) power of the distance from the plait point, where α and γ are the indices of the divergence of the constant-volume specific heat and of the compressibility, respectively, in the one-phase region of the reference system.

Flow-cell studies of thermal diffusion in liquids. Part 2.—Phenomenological equations and their solution

Equations are developed describing the attainment of Soret equilibrium in two-component liquid systems flowing in a laminar fashion through a rectangular duct. The resulting diffusion equation is solved in a simplified form, valid for small temperature intervals, by a suitable finite difference approximation. A complementary solution yielding an explicit expression for the separation and valid for large times is derived from the calculus of variations. Use of this expression for interpreting practical results, as in the calibration experiments, is shown in part 1. Consideration of the errors involved in the simplified diffusion equation leads to an upper limit on the temperature interval for the validity of the solution. Errors arising from finite thermal and velocity entry lengths are shown to be negligible.

The magneto-optic rotations of some two-component liquid systems

The first page of this article is displayed as the abstract.

Opalescence of a two-component liquid system near the critical mixing point.

Opalescence of a two-component liquid system near the critical mixing point.