Natural Materials Analytical Research Laboratory
The Natural Materials Analytical Research Laboratory (NMARL) offers analytical services
designed specifically to address engineering problems in a wide range of fields.
Analytical facilities combined with an experienced team of researchers provide a
full range of advanced materials characterization and data interpretation.
Scanning Electron Microscopy
Scanning electron microscopy is an analytical technique that is capable of combining both
imaging and chemical analysis. Scanning electron microscopes (SEMs) have imaging capabilities
that can range from tens to tens of thousands of times of magnification. The energy-dispersive
spectrometry (EDS) system allows chemical analyses of single points, small areas, lines, and
even chemical mapping of the sample surface (mineral maps). The physical and chemical
relationship of grains or materials next to each other is an important part of materials
characterization, whether that characterization is to be used to determine the origin or
chemical transformations of minerals and materials or to predict the behavior of a material
when exposed to various conditions.
The NMARL uses two JEOL 5800 series SEMs. One is a JEOL 5800 LV and is capable of low-vacuum (LV)
imaging and analysis, and the other is a dedicated high-vacuum (HV) SEM. Both of the SEMs are
equipped with Oxford Instruments EDS systems, and both have silicon drift x-ray detectors (SDD)
for high-speed analysis. The EDS detector on the JEOL 5800 LV is an Oxford Instruments X-Max®
detector with an 80-mm2 analyzing crystal. The analytical system uses both Inca® and AZtec® EDS
software by Oxford Instruments that is capable of point analyses, linescans, x-ray and phase mapping,
and automated feature analysis. The JEOL 5800 HV uses an INCA X-act® x-ray detector with a
10-mm2 analyzing crystal and Oxford Instruments Inca® software capable of point analysis, x-ray mapping,
and automated feature analysis.
X-Ray Diffraction (XRD)
XRD is a qualitative to quantitative technique used for problems ranging from the identification
of minor and clay phases to determining the anisotropic thermal expansion coefficients of novel
materials. Phases are identified using the automated search–match PDF2 database and TOPAZ,
the most widely used commercial software for whole-pattern fitting; the Rietveld, Pawley, and
LeBail methods; indexing; quantitative-phase analysis (QPA); and ab initio structure determination.
Depending on sample preparation and composition, QPA can determine the absolute amounts of crystalline
phases down to 0.1 wt%. XRD can also identify the presence of amorphous material (glass) but
not the composition. The system is capable of performing thin-film analysis, stress analysis, and texture analysis.
The Bruker AXS D8 ADVANCE is a state-of-the-art research-grade XRD instrument for conducting
crystalline-phase identification, ab initio structure determination, and QPA. The Bruker XRD is
capable of conversion from Bragg–Brentano to parallel-beam geometry for various sample types. It is
equipped with a nine-position sample changer and a rotating stage. The software is Bruker’s Eva®,
with automated search–match of the crystalline phases using the PDF2 database. QPA is done with Topas® software,
which is a widely used commercial software package for whole-pattern fitting using the Rietveld method.
X-Ray Fluorescence (XRF)
XRF is a technique that provides the bulk chemical composition of samples. Most often,
samples are powders pressed into pellets, but the fusion pellet process can be used to make glass pellets.
Quick semiquantitative determinations can be made for elements with atomic numbers 5–92. XRF can be used
in conjunction with chemical fractionation, a wet-chemistry technique used to quantitatively determine the
modes of occurrence of the inorganic elements in coal, based on the extractability of the elements in solvents.
The Rigaku ZSX PRIMUS II is a wavelength-dispersive x-ray system that is good for elements above atomic
number 6 with accuracies that can be attained to the ppm level (traditional reporting to 0.1 wt%). Standards
must be available for elements to be quantified.