Linear Velocity Of Crystallization Research Articles

Solidification behaviour of addition compounds and eutectics of pure components and addition compounds

AbstractSolid‐liquid equilibrium data for (i) o‐phenylenediamine‐β‐naphthol, (ii) resorcinol‐o‐phenylenediamine, (iii) o‐phenylenediamine‐α‐naphthol, and (iv) picric acid‐catechol systems, showing congruent melting points, have been recorded. The 1:1 addition compounds formed in these systems form eutectics with either of the components. The linear velocity of crystallization and heat of fusion for the addition compounds and the eutectics have been measured. Microstructural studies indicate that the addition compounds have a structure similar to that of the pure components, whereas the eutectics have fibrous, feather‐like, spherulitic and lamellar structures. The effect of impurities on microstructures has also been discussed. Diffusion coefficient measurements in lamellar eutectics show that Jackson‐Hunt theory of eutectic growth, based on a diffusion model, is applicable. Excess thermodynamic functions, gE, hE, and SE have also been calculated for eutectics.

Solidification Behaviour and Zone‐Melting Studies of Eutectic: Pyrogallol‐m.aminophenol system

AbstractPhase diagram, relative undercooling, linear velocity of crystallization and microstructure of eutectic have been investigated for the pyrogallol‐m;aminophenol system. The linear velocity of crystallization, V, for pure component and eutectic depends on ΔT according to the relation V = k(ΔT)n, where k and n are constant. Zone‐melting studies were made to determine the direction of solute transference, separation efficiency and equilibrium distribution coefficient.

Chemistry of organic eutectics (III). α‐Naphthol‐naphthalene system

AbstractRelative supercooling, linear velocity of crystallization and microstructure for the α‐naphthol‐naphthalene eutectic system have been investigated in order to understand the mechanism of eutectic solidification. Heat of fusion measurements indicate the possibility of molecular association in the liquid melt. The effective distribution coefficient, direction of solute transference, and separation efficiency have also been determined using zone melting technique.

Chemistry of organic eutectics: II. The naphthalene-p-chloronitrobenzene eutectic system

A detailed study of the naphthalene-p-chloronitrobenzene eutectic system has been made. Phase diagram, undercooling, linear velocity of crystallization, and diffusion coefficient measurements have been made. Microstructure studies indicate that the system possesses rod structure. The results indicate that the diffusion model theory proposed by Jackson and Hunt is satisfied by the data.

Chemistry of organic eutectics. I

α-naphthol-catechol and β-naphthol-catechol eutectic systems were investigated using phase diagram, undercooling, linear velocity of crystallization, heat of fusion, and diffusion coefficient measurement methods. Microstructure observations of the eutectics indicate that they possess lamellar structures. The surface nucleation theory and the diffusion model proposed by Jackson and Hunt were tested. It is found that the diffusion model of nucleation is probably in better agreement with the experimental results.

Mechanism of eutectic crystallization. II

Abstract Relative undercooling, linear velocity of crystallization and microstructure of eutectics have been investigated for (i) naphthalene-m-nitroanaline, (ii) m-dinitrobenzene-phenanthrene, (iii) m-dinitrobenzene-acetanilide, and (iv) 2,4 dinitrophenol-acetanilide systems. The linear velocity of crystallization I for pure components and eutectics is found to depend on Δ according to the equation I = K ( ΔT ) n , where K and n are constants. For the eutectics, apparently lamellar structure in system (ii) and rod type structure in systems (iii) and (iv) are obtained. For system (ii), the interlamellar spacing λ and I are related by the equation λ = cI - 1 2 . The experimental data have also been examined in the light of recent theory of lamellar growth due to Jackson and Hunt.