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South African Journal of Chemistry

versión On-line ISSN 1996-840X
versión impresa ISSN 0379-4350

S.Afr.j.chem. (Online) vol.64  Durban  2011

 

RESEARCH ARTICLE

 

Using PXRD to investigate the crystallization of highly concentrated emulsions of NH4NO3

 

 

E.E. FergI, *; I. MasalovaII

IDepartment of Chemistry, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031, South Africa
IIDepartment of Civil Engineering, Cape Peninsula University of Technology, P.O. Box 652, Cape Town 8000, South Africa

 

 


ABSTRACT

The process of crystallization of highly concentrated emulsions of ammonium nitrate can be studied using powder X-ray diffraction. The dispersed particles comprise a supercooled aqueous solution of the ammonium nitrate salt and are dispersed in a paraffin-based oil. This results in a thermodynamically unstable system that 'ages' with time resulting in changes in rheological properties and its phase composition where the collapse of the supercooled aqueous solution forms the crystallized salt. The crystallization processes of these emulsions are kinetically slow and can take up to a few months to crystallize completely. The general approach to this type of analysis is to determine the change in crystalline diffraction peak intensities relative to the halo due to the amorphous content. However, there are a number of problems associated with this method which are addressed by using Rietveld refinement methods which can take into account factors such as preferred orientation, crystallite size variations and mixtures of solid phases. The study showed that the ammonium nitrate emulsions kept at room temperature slowly crystallize predominantly to the room temperature solid ammonium nitrate phase IV. However, depending on the formulations used some samples showed crystallization to the high temperature ammonium nitrate phase II before changing to phase IV. The crystallization change could be modelled by the well-known JMAK kinetic relationship.

Keywords: Ammonium nitrate emulsion, crystallinity, X-ray diffraction


 

 

Full text available only in pdf format.

 

Acknowledgements

The authors thank the South African National Research Foundation (NRF) for funding towards the project.

 

References

1 H.A. Bampfield and J. Cooper, Emulsion Explosives, in Encyclopaedia of Emulsion Technology, Marcel Dekker, New York, NY, USA, 1985.         [ Links ]

2 R. Pons, C. Solans, M.J. Stebe, P. Erra and J.C. Ravey, Prog. Colloid Polym. Sci., 1992, 89, 110-113.         [ Links ]

3 I. Masalova, A.Y. Malkin, E. Ferg, E. Kharatiyan, M. Taylor and R. Haldenwang, J. Rheology, 2006, 50, 435-451.         [ Links ]

4 I. Masalova, A.Y. Malkin, P. Slatter and K. Wilson, J. Non-Newtonian Fluid Mech, 2003, 112, 101-114.         [ Links ]

5 F. Villamagna and M.A. Whitehead, J. Mol. Struct, 1995, 356, 149-158.         [ Links ]

6 P. Bergese, I. Colombo, D. Gervasoni and L.E. Depero, J. Appl. Cryst., 2003, 36, 74-79.         [ Links ]

7 M. Kakudo and N. Kasai, X-ray Diffraction by Polymers, Kodansha Scientific Books, Tokyo, Japan, 1972.         [ Links ]

8 R. Surana and R. Suryanarayanan, Powder Diff, 2000,15, 2-6.         [ Links ]

9 S. Yamamura, R. Takahira and Y. Momose, Pharm. Res., 2007, 24, 880-887.         [ Links ]

10 X. Chen, S. Bates and K.R. Morris, J. Pharm. Biomed. Anal., 2001, 26, 63-72.         [ Links ]

11 N.G. Parsonage and L.A.K. Staveley, Disorder in Crystals, Oxford University Press, Oxford, UK, 1978.         [ Links ]

12 A. Guinier, X-ray Diffraction in Crystals, Imperfect Crystals and Amorphous Bodies, Dover Publications, New York, NY, USA, 1994.         [ Links ]

13 P. Suortti, J. Appl. Cryst., 1972, 5, 325-331.         [ Links ]

14 A. Coelho, J. Appl. Cryst, 2000, 33, 899-908.         [ Links ]

15 E. Ferg, D.C. Levendis and F.R.L. Schoening, Chem. Mater., 1993, 5, 1293-1298.         [ Links ]

16 J.C.A. Boeyens, E. Ferg, D.C. Levendis and F.R.L. Schöning, S. Afr. J. Chem., 1991, 44, 42-46.         [ Links ]

17 C.S. Choi, H.J. Prask and E. Prince, J. Appl. Cryst., 1980,13, 403-409.         [ Links ]

18 ICDD, International Centre for Diffraction Data, Philadelphia, PA, USA, 2004.         [ Links ]

19 I. Masalova and A.Y. Malkin, Colloid J., 2007, 69, 198-201.         [ Links ]

20 Bruker AXS, Topas V3: General Profile and Structure Analysis Software for Powder Diffraction Data, Bruker AXS, Karlsruhe, Germany, 2005.         [ Links ]

21 P. Stutzmann, Adv. X-ray Anal, 2004, 47, 206-211.         [ Links ]

22 L. Mandelkern, Crystallization of Polymers, McGraw-Hill, New York, NY, USA, 1964.         [ Links ]

 

 

Received 24 December 2009
Revised 19 October 2010
Accepted 22 December 2010

 

 

* To whom correspondence should be addressed. E-mail: ernst.ferg@nmmu.ac.za

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