Date:         Fri, 11 Dec 1998 14:21:21 -0000
Reply-To: [email protected]
Sender: CLYMIN-L >[email protected]<
From: Stephen Hillier >[email protected]<
Organization: mluri
Subject:      spray drying
To: Multiple recipients of list CLYMIN-L >[email protected]<

Following, the recent postings on quantitative clay mineral analysis to
the CMS list server I have received a number of enquiries about spray
drying.  Therefore, it seemed appropriate to send some general
information back to the list.

Basically, we have developed a relatively simple and efficient
way to prepare a random powder sample for XRD by spray drying.  The
technique uses a similar but smaller oven to that described by (Smith et
al 1979) but the sample is sprayed from a hand held air-brush and
recovered from a sheet of paper.  The use of the air-brush and the paper
both contribute to a relatively good sample recovery of typically  80% of
what goes in. Poor sample recovery probably being the main reason why
this technique has not been widely adopted in the past.  At MLURI we
now routinely prepare all our random powder samples by spray drying
including soils, sediments, sandstones, drilling muds, bentonites etc, as
well as clay fractions separated from them. A competent operator can
process about 30 samples a day. The method and equipment is described
in a paper soon to be published (next issue I think) in Clay Minerals.

The result of spray drying is an extremely fluid and easily
handled powder consisting of thousands of spherical agglomerates of
the sample components.  The arrangement of any component within the
spherical agglomerates and of the agglomerates themselves ensuring
that preferred orientation is eliminated from the powder sample presented
to the X-ray beam (Smith et al. 1979). Although there are sophisticated
ways of dealing with the effects of preferred orientation, it's much better
to eliminate it in the first place. Thereafter, you can apply any method
you like to process your diffraction data for quantitative analysis,
computerised or otherwise.

At present we have built two spray dryers and are in the
process of supplying another as a complete kit (air-brush, oven, paper,
manual) to Bruker's application lab (formerly Siemens) in Germany. As a
result we are considering the possibility of producing these kits to order
through the commercial arm of the Macaulay Institute, MRCS.  If anyone
is interested in this possibility if they contact me directly, I can let 
them know the details.

Smith S.T., Snyder R.L. and Brownell W. E. (1979)  Minimisation of
preferred orientation in powders by spray-drying.  Advances in X-ray
Analysis 22, 77-87.


Steve Hillier

Dr Stephen Hillier
Soil Science Group
Macaulay Land Use Research Institute
Craigiebuckler, Aberdeen, AB9 2QJ, UK.

Tel/Fax: +44 1224 318611/311556