MudMaster is a computer program, developed at the U.S. Geological
Survey and written by D. D. Eberl, V. Drits, J. Srodon and R Nuesch, that
calculates crystallite size distributions and strain for minerals from
X-ray diffraction data. This program was developed to measure particle
size distributions for minerals in rocks and soils, because particle size
data may yield geological information about a mineral's provenance, degree
of metamorphism, degree of weathering, etc. However, this program also
would be useful to many types of manufacturers who use or synthesize
nano-size material, because a mineral's particle size and strain may
strongly influence its physical and chemical properties (e.g. its rheology,
surface area, cation exchange capacity, solubility, reflectivity, etc.).
Nano-size crystals generally are too fine to be measured by light
microscopy. Laser scattering methods give only average particle sizes;
therefore, particle size cannot be measured in a particular
crystallographic direction. Also, the particles measured by laser
techniques may be composed of several different minerals, and may be
agglomerations of individual crystals. Measurement by electron and atomic
force microscopy is tedious, expensive, and time consuming. It is
difficult to measure more that a few hundred particles per sample by these
methods. This many measurements, often taking several days of intensive
effort, may yield an accurate mean size for a sample, but may be too few to
determine an accurate distribution of sizes.
Measurement of size distributions by X-ray diffraction (XRD) solves
these shortcomings. An X-ray scan of a sample occurs automatically, taking
a few minutes to a few hours. The resulting XRD peaks average diffraction
effects from billions of individual nano-size particles. Therefore one can
determine the size of an individual mineral in a mixture of minerals, and
the size in a particular crystallographic direction of that mineral.
Crystallite shape can be determined by measuring crystallite size in
several crystallographic directions.
The XRD method is based on the observation that XRD peaks are
broadened regularly as a function of decreasing crystallite size. The
program uses a Fourier analysis of XRD peak shape to calculate crystallite
size distributions and strain for crystalline samples, according to the
theory developed by Bertaut (1950) and Warren and Averbach (1950). The
program accurately calculates sizes in the range from about 2 nm to about
100 nm. The upper limit for size determination depends significantly on
the accuracy of instrumental standards.
Use of MudMaster requires Microsoft Excel, version 5.0 or greater,
and an elementary knowledge of how to use the Excel program (pasting data,
changing the axis on a chart, etc.). MudMaster works best on a computer
having 16 or more megabytes of RAM. Ten or more megabytes should be
assigned to run the Excel program if your system offers an option to assign
memory to a program. The program occupies about 4 Mb of disk space.
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