Manijeh Reyhani | Curtin and UWA (original) (raw)

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Papers by Manijeh Reyhani

Developments in chemical engineering and mineral processing, May 15, 2008

Manganese sulphate crystals can be produced in laboratory‐scale batch crystallisers by either hea... more Manganese sulphate crystals can be produced in laboratory‐scale batch crystallisers by either heating or by salting‐out crystallisation. However, manganese sulphate produced through heating forms monohydrate while salting‐out mode will form the tetrahydrate. The effects of various operating conditions including supersaturation, temperature and seed dosage on growth rate of these hydrates were studied. The crystal size distribution of manganese sulphate crystals was determined by Malvern Mastersizer laser diffraction and by using a Nikon microscope with digital camera attached. The growth rate was determined from the time shft of the crystal size distribution expressed in population density numbers and by the moments method. The measurements of the growth of the crystals from ex situ microscopy supported the calculated growth rate. Salting‐out crystallisation resulted in relatively large cubic crystals, and their size and size distribution can be improved by careful control of the operating conditions. However, heating crystallisation produced irregular crystals where controlling the operating conditions has little effect on the final crystal size and size distribution with almost no observable growth.

Scripta Metallurgica, Apr 1, 1986

Scripta Metallurgica, Apr 1, 1987

International Journal of Modern Physics B, Jan 20, 2002

Real time in situ monitoring of calcite growth and inhibition on the cleavage plane [Formula: see... more Real time in situ monitoring of calcite growth and inhibition on the cleavage plane [Formula: see text] is investigated using atomic force microscopy (AFM). Calcite growth and inhibition were studied using a Molecular Imaging microscope in contact mode, equipped with an in situ fluid cell. As has been reported previously, it is observed that calcite growth from aqueous solution is by motion of mono-molecular steps, and dissolution by a combination of step motion and etch pit expansion. The measured step heights were between 2.7 to 3 Å. Our aim is to study the effects of a range of phosphonate-based crystal growth inhibitors of related structure, in order to provide insight into the mechanism of inhibition as a function of the additive structure. Results of this study demonstrate the effect of inhibitors on the growth steps and terraces on the [Formula: see text] surface of calcite in real time. The organic additives bind to the crystal surface, with selective binding to the step edges particularly evident in some cases. In other cases, it appears that the additive acts by binding to the terraces on the crystal surface, resulting in inhibition by coating the surface. Efforts to correlate the observations made by atomic force microscopy with bulk crystallization experiments have been made.

American Chemical Society eBooks, Jun 1, 1997

Acs Symposium Series, Jun 1, 1997

The conversion of bauxite ore into alumina, via the Bayer process, is a well established major in... more The conversion of bauxite ore into alumina, via the Bayer process, is a well established major industry. However, the rate of precipitation of alumimum trihydroxide as gibbsite is an extremely slow process and is not well understood. Moreover, difficulties are encountered in ...

Journal of Crystal Growth, Mar 1, 2003

The inhibition of barium sulfate precipitation in the presence of phosphonate containing molecule... more The inhibition of barium sulfate precipitation in the presence of phosphonate containing molecules was investigated experimentally and speciation curves were used to elucidate the interactions involved. Inhibition of precipitation was found to be pH dependent and loss of inhibition was observed at both very high and low pHs. Maximum inhibition for all the inhibitor molecules occurred at pH 8. While speciation curves showed that inhibition could be improved by the presence of 2 or more fully de-protonated phosphonate groups (for pure aminophosphonates) on the molecule at pH ≤ 8, at pH 12 inhibition was insensitive to the number of deprotonated phosphonate groups. It is, therefore, suggested that surface charge repulsion affects inhibition at very high pH. For molecules which are not pure aminophosphonates, stereochemistry as well as functional groups and their ionisation state appear to play a significant role in inhibition at 3<pH≤8.

Journal of Materials Science & Technology, Oct 10, 2009

The relationship between Charpy absorbed energy and the fracture toughness by means of the (crack... more The relationship between Charpy absorbed energy and the fracture toughness by means of the (crack tip opening displacement (CTOD)) method was analyzed based on the Weibull stress criterion. The Charpy absorbed energy and the fracture toughness were measured ...

Science Access, 2004

This contribution reports on the Raman spectra and polarised light images obtained for hexagonal ... more This contribution reports on the Raman spectra and polarised light images obtained for hexagonal six-fold twinned and diamond shaped single crystals of synthetic and industrial gibbsite. The results are interpreted in terms of a possible growth mechanism for gibbsite.

Journal of Crystal Growth, Sep 1, 1996

Secondary nuclei of potash alum crystals may easily be produced by gentle crystal contact. In thi... more Secondary nuclei of potash alum crystals may easily be produced by gentle crystal contact. In this investigation, crystal faces of the {100}, {110} and {111} families were identified in a parent crystal, and gentle contact between these and a solid surface in a slightly supersaturated solution of potash alum produced many secondary nuclei of the same orientation. Breeding of the large number of particles produced by contact between a parent crystal and a glass surface under supersaturated aqueous solution was directly observed by optical microscopy with an in situ, thermostatted cell. A strong correlation was found between the symmetry of the nuclei produced and that of the parent crystal face. Ex situ scanning (SEM) and transmission electron microscopic (TEM) measurements were also carried out to study this type of secondary nuclei, produced from a known surface geometry. In these cases, many small nuclei in the size range of 50 nm to 1 /xm were produced and studied. The larger crystals displayed morphologies commensurate with that of the parent face; the very small nuclei, whilst frequently showing very poorly ordered boundaries, nonetheless were highly ordered internally, as shown by electron diffraction, the symmetry observed reflecting that of the parent face.

Applied Physics A, Mar 1, 1998

Although secondary nucleation is the main source of new crystal nuclei in an industrial crystalli... more Although secondary nucleation is the main source of new crystal nuclei in an industrial crystallizer, the precise source of contact nuclei has not yet been determined. To address the various theories presented in the literature, we have adopted the dual approach of using microscopy to characterize, at their earliest stages of growth, the secondary nuclei that are produced by contact and also the surface topography of the primary crystals before and after contact. AFM studies of a range of crystals, including isomorphous alums, combined with scanning and transmission electron microscopy experiments indicate that, at least for the case of very gentle contact, transfer of crystallographic information can occur through an ordered solute layer in a supersaturated solution without the need for the transfer of solid materials from the primary crystal by microattrition. Knowledge about this mechanism has the potential to improve the quality of product from industrial crystallizers, through control of crystal morphology and size distribution.

Scripta Metallurgica Et Materialia, Oct 1, 1994

Previous studies on the effect of cycling in Fe-Mn-Si alloys have shown an increase in reversibil... more Previous studies on the effect of cycling in Fe-Mn-Si alloys have shown an increase in reversibility with increasing number of thermal cycles. In Fe-Mn-Si-Cr-Ni and Fe-Mn-Si-Co-Ni alloys, the shape recovery strain during thermomechanical cycling increased when the strain amplitude for each successive cycle is kept constant. Where the total strain (i.e., the sum of the transformation and permanent strain) is

Scripta Metallurgica, 1986