Distribution of component molecules in p-dibromobenzene-p-dichlorobenzene solid solutions from raman effect data

Korshunov, M. A.

doi:10.1134/1.1578137

Cited by 3 publications

(5 citation statements)

References 1 publication

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“…Clearly, neglecting the diffusion in the solid phase, in the end the solid phase will be inhomogeneous with the last-grown solid portion being richer in 1,4-dichlorobenzene as compared to the first-grown part of solid. On behalf of the latter, the investigation of mixed crystals of the issued components by Raman effect [8] illustrates their distribution along the length and diameter of the single crystal, showing that the concentration of 1,4-dichlorobenzene increases in direction from the centre to the periphery of the crystal.…”

Section: Article In Pressmentioning

confidence: 99%

Metastability in solid solution growth

Matovic

Miltenburg

Los

2005

Journal of Crystal Growth

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Crystallization of binary mixtures of 1,4-dichlorobenzene and 1,4-dibromobenzene is examined in an adiabatic calorimeter. First heated to 380 K under adiabatic conditions and thus transformed into a binary melt, the mixture was slowly cooled to 250 K. The experimental cooling curves (the recorded change of mixture's temperature with time) obtained for the various compositions of the issued mixture, served for the specification of enthalpy change of the mixture during crystallization. In order to demonstrate the importance of the kinetics during an even slow crystallization process, the experimental data will be interpreted in terms of a kinetic model as opposed to the traditionally used equilibrium approach. We will show that kinetic model can serve for the derivation of excess parameters that characterize the degree of mixing in the phases. r

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Section: Article In Pressmentioning

confidence: 99%

Metastability in solid solution growth

Matovic

Miltenburg

Los

2005

Journal of Crystal Growth

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“…dH mix = dH mix,cool + dH trans = c p,mix dT + H fus ds (9) where H fus is the composition dependent enthalpy of fusion of the mixture and ds refers to the amount of the solid phase that is formed within the time interval dt corresponding to the temperature change dT . Let us turn now to the qualitative analysis of the experimental data, where the two parts of the crystallization process were distinguished.…”

Section: Quantitative Analysis Kinetic Modelmentioning

confidence: 99%

“…Therefore, the result of crystallization will be an inhomogeneous state of solid that contains composition gradients in its bulk. As an example, previous analysis of the mixture of 1,4-dichlorobenzene and 1,4-dibromobenzene by Raman spectroscopy illustrates the distribution of the given components along the length and the diameter of the single crystal [9].…”

Section: Introductionmentioning

confidence: 99%

Kinetic approach to the determination of the phase diagram of a solid solution

Matovic

Miltenburg

Oonk

et al. 2006

Calphad

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A binary mixture of 1,4-dichlorobenzene and 1,4-dibromobenzene, as a representative of a system that forms a solid solution, was measured in an adiabatic calorimeter. Several mixtures of different compositions were heated to 380 K, kept in the liquid phase at this temperature overnight, and then cooled slowly down to 250 K. The enthalpy path of the mixture measured during cooling carries the information that enables us to describe the crystallization process. In the first stage, crystallization develops rapidly and clearly deviates from equilibrium, while in the second stage it proceeds significantly slower, whereby we assume that the surface of the solid is in equilibrium with the existing liquid phase at the given temperature during cooling. Such an approach opposes the one that assumes equilibrium between the liquid and solid bulks, known as the equilibrium model. We show that by employing the kinetic model, the experimental enthalpy path of the mixture during cooling in the adiabatic calorimeter can be very successfully reproduced, while the equilibrium model fails in this aspect. Furthermore, we propose a procedure where the kinetic model is used to obtain the excess thermodynamic properties of the solid phase. These quantities enable the calculation of the liquid-solid phase diagram using the excess parameters obtained from the approach that does not assume the overall equilibrium between the phases during the crystallization process.

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“…The plan of installation shown in 2, consists of He-Ne the laser (1) which beam (2) transiting through a prism turning it (3) and a lens (4) focalized on a surface of an explored sample (5). The scattered radiation of a crystal (6) transiting through a diaphragm (7) and a lens (8) hits on a crack of a spectrograph (9).…”

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confidence: 99%

“…Using the installation circumscribed in-process [5], permitting to gain Raman of spectrums from small areas is modeled and the focused laser beam sondage of received organic films is carried out.…”

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confidence: 99%

Use of laser for study of allocation of vacancies in nanocrystallic films of organic matters

Korshunov

Proceedings of CAOL 2005. Second International Conference on Advanced Optoelectronics and Lasers, 2005.

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The presence of defects in a structure (vacancies causing a diffusion, etc.) can affect quality of a material used in nanotechnology. To study this problem the examination of a nanocrystal film of organic matter by a method of Raman effect has been used. This method picked, as spectrums of the lattice oscillations are rather sensitive to structural change of a crystal. In the capacity of a subject of inquiry the molecular crystal paradibromobenzene which are a good model for the picked object. It is shown the sondage usage by the focused laser beam of films of organic crystals and Raman effect method of light allocation of vacancies in a film. It is found that at diminution ofthickness of a film the number of vacancies will increase up to particular quantity, and their allocation on a film surface in investigated samples is not uniform. The changes of physical properties because of a dimensional change of crystal grains for the structures built from organic molecules, apparently, is observed at their greater size, than for the structures built from atoms.Organic crystals find the increasing application in molecular electronics (at making chips, and in devices of storage). Thus, it is used nanotechnology. Nanostructure properties differ from properties of crystals of greater size. Change of physical properties because of a dimensional change of crystal grains for the structures built from organic molecules, apparently, should be observed at their greater size, than for the structures built from atoms. Thus, the number of defects per unit volume with diminution of the sizes will increase. Besides, surface effect is incremented by physical properties of crystal grains.The presence of defects in a structure (vacancies causing a diffusion, etc.) can affect quality of a used material. For example, the molecule with the changed parameters can migrate and change noted information. It is necessary to know how defects place in the obtained structure (it is even or is not even). Therefore, the increasing value is gained with methods of a non-destructive quality control used is model also examination of the obtained structure nanocrystal a material. As [1] mobility of atoms is scored in-process and, apparently, molecules will increase in nanocrystal substances by 5-6 orders in comparison with routine polycrystals.To study this problem, the examination of a nanocrystal film of organic matter by a method of Raman effect has been lead. This method picked, as spectrums of the lattice oscillations are rather sensitive to structural change of a crystal. In the capacity of a subject of inquiry the molecular crystal paradibromobenzene which are good model object picked. Paradibromobenzene it was studied by various methods. It crystallizes in space group P2, /a with two molecules in a unit cell [2]. It has been prepared three samples. Firstly, the monocrystal paradibromobenzene was brought up. Secondly, the monocrystal film on a glass substrate by thickness -5 m on a method given in-process [3] was brought up. After that, the film wa...

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Distribution of component molecules in p-dibromobenzene-p-dichlorobenzene solid solutions from raman effect data

Cited by 3 publications

References 1 publication

Metastability in solid solution growth

Metastability in solid solution growth

Kinetic approach to the determination of the phase diagram of a solid solution

Use of laser for study of allocation of vacancies in nanocrystallic films of organic matters

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