1,720,983 research outputs found
Equilibrium and growth forms of sucrose crystals in the {h0l} zone. 1. Theoretical treatment of {101}-d form
No full textObserved (h0l) growth forms of the sucrose crystal are compared with calculated ones, on the basis of attachment energy plots. Agreement is found for all forms only if a modification of character of the ( 101)-d face is taken into considation. Calculation of equilibrium and growth forms have been carried out using two potential foe dispersion and bond energy respectively. The same method is applied for studying the spiral growth shape on the (101) face and its field of validity is discussed: a low driving force values, the attachment energy at the steps is the relevant energy, determining the shape of spirals on (101) face of sucrose
(100) and (111) Forms of NaCl-like Crystals Coexisting in Growth from Pure Aqueous Solution.
No full textThe Authors prove, by means of SEM, the co-existence of (100) and (111) forms in pure aqueous solution in well defined supersaturation range. The consequences of the "octopole hypothesis" is discussed. Finally, according to the calculation of the reconstructed (111) surfaces, the equilibrium shape of the crystals was determined
Sucrose crystal growth kinetics in the presence of some peculiar impurities
No full textThe effect of some impurities on the growth rate of the single faces of sucrose crystals together with its morphology variation, is studied. The kinetic data are qualitatively explained on the grounds of the direct interaction between the impurities and the structure of the different faces of sucrose crystals
Growth kinetics of epsomite (MgSO4·7H2O)
No full textGrowth isothermes of the most important F forms (110), (010), (111), (-1-1-1), (100) of epsomite were measured on single crystals growing from pure aquous solutions at 30 and 40 °C. The results are discussed and compared with previous reported data
Sostanze coloranti nel cristallo di saccarosio
No full textCristalli di saccarosio ottenuti in presenza di varie sostanze coloranti sia in laboratorio che in scala pilota hanno mostrato l'importanza decisiva della velocità di crescita per l'inclusione di queste nelle loro facce (110), (111), (011), (11-1): quanto più è rapida la crescita, tanto maggiore la colorazione acquisita dai relativi settori
{1 0 4} cleavage rhombohedron of calcite: Theoretical equilibrium properties
No full textThe character of the most important crystallographic forms of calcite crystal is quantitatively reviewed according to the Hartman and Perdok theory. Specific surface and edge energies of the cleavage {1 0 4} rhombohedron are calculated in the crystal-vacuum system by means of a semi-empirical potential function and following Stranski's definition of the total surface energy of a finite crystal. A comparison is made between the calculated value and the experimental quantities entering the Dupre formula (specific crystal-solution interface energy, specific vapour-solution surface energy): the crystal-vacuum specific surface energy is proved to be quite reasonable, and for the first time, the specific crystal-solution adhesion energy for the {1 0 4} form is estimated
La colorazione dei cristalli di zucchero in funzione di alcuni parametri della cristallizzazione industriale. Sucrose crystals colour as a function of some industrial crystallization parametrs
No full textSulla base dei risultati raggiunti in una precedente ricerca, che aveva individuato nella cinetica di accrescimento la principale causa di inglobamento di sostanze coloranti nei cristalli di saccarosio, gli Autori proseguono la sperimentazione allo scopo di poter trasferire le loro conclusioni alla pratica della cristallizzazione industriale
Growth morphology of epsomite (MgSO4·7H2O)
No full textA first approach to the study of the growth properties of epsomite (MgSO4·7H2O) is presented. Particular attention is payed to the growth forms and to epitaxy relations between epsomite and some known habit modifiers. The starting point of the study is the Hartman and Perdok PBC analysis. It proves to be essential for knowing the actual surface profiles. Successively the theoretical growth morphology is given taking into account: the broken-bond model of Wolff and Broder, the energies associated to the hydrogen bonds only, and finally the attachment energies calculated on the basis of the Coulomb potential. Furthermore an analysis of 2D coincidence lattices leads us to the conclusion that a 2D epitaxy of both Na2B4O7·lOH2O and/or Na2SO4·lOH2O on {111} and/or {A figure is presented} forms of epsomite explains the effect of borax and Glauber's salt as habit modifiers. © 1985
The raffinose effect on sucrose morphology and kinetics
No full textThe authors carried out a detailed crystallographic study on the theoretical surfaces of sucrose, and face by face kinetics on both the single and twin sucrose crystals. The relevant experimental results are presented and discussed. Investigations on the eventual attachement of the raffinose molecule to the various faces of the sucrose crystal were carried out also. On the basis of the experimental data, and taking into account that through the structural investigation two different types of kink and two different types of set of the molecule are singled out, the possibilities of the attachment of the raffinose molecule to the sucrose molecule are discussed
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