Materials Analysis and Research Laboratory (MARL) Rooms Town Engineering part of the Materials Science and Engineering Department of the College of Engineering at Iowa State University

MARL’s Mission MARL's function is three-fold: research and development, teaching, and service. It uses its facilities for chemical and physical characterization of a wide variety of materials to support research and teaching programs within the university. MARL also conducts research on unusual material evaluation problems for outside agencies through research grants MARL also undertakes analyses for industry when comparable facilities are not available.

Materials Analysis and Research Laboratory - Analytical Tools Scanning Electron Microscopy (microstructure and chemistry) Optical Microscopy (microstructure) X-ray Diffraction (atomic arrangement, crystal structure) X-ray Fluorescence (bulk chemistry down to ppm levels) Thermal Analysis (phase changes with temperature)

Scanning Electron Microscopy (SEM) High resolution Great depth of field Minimal sample prep Variety of imaging signals Combined microstructure and microchemistry

Resolution - Depth of Field High resolution - short ‘wavelength’ of electrons leads to resolution of 3 nm (compared to ~0.5 um for optical microscopes) Great depth of field – long working distance yields depths of field measured in tens or hundreds of microns, essential for rough samples.

Micro-machine -2000x

Deicer salt - 25x, showing depth of field

Deicer salt - 25x, stereo analgyph to show depth (3-D image, use glasses)

Dendrite in fracture - stereo analgyph to show depth (3-D image, use glasses)

Metal shaving - 250x, stereo analgyph to show depth (3-D image, use glasses)

Molybdenum crystals - stereo analgyph to show depth (3-D image, use glasses)

Minimal Sample Preparation Most materials need only be clean to examine them in the scope Samples may need to be coated to provide a conductive path for the electrons Environmental SEM can examine insulating samples without coating, i.e., in their natural state.

Wasp eye - 100x no sample preparation

Variety of Imaging Signals Secondary electrons – great topographic detail Backscattered electrons –atomic number contrast X-rays – elemental identification and concentration Other – cathodo-luminescence, absorbed current, voltage contrast

Combined microstructure and microchemistry Detects elements as light as Beryllium Analysis volumes as small as 1 um Quantitative chemical analysis down to tenths of a percent Quantitative concentration profiling Qualitative 1-D and 2-D mapping of multiple elements within minutes

Light Element Detectability X-ray spectrum of Dolomite - CaMg(CO 3 ) 2 showing oxygen and carbon peaks

Chemical Analysis - Alloy Identification Bronze contains tin (Sn) plus silicon (Si) for casting Both alloys contain lead (Pb) for machinability. Comparison of brass (red) and bronze (blue) alloys Brass contains zinc (Zn)

Normal brass (red) and brass following de-zincification (blue) Chemical Analysis - Brass Fittings

Quantitative Concentration Profiles: Mn, Ga, Ni alloy Localized fluctuations in composition are observed along with general trend

X ray map of concrete components Brightness reflects the concentration of the element Ettringite (S+Al) ImageAl Si KMg Na S Feldspar (Al, Si, + Na or K) Alkali-rich paste (K) Quartz (Si) Dolomite (Mg)

Qualitative Line Scan Dolomite Quartz K-rich paste Good for showing detail and subtle changes in composition. Scan starts at crosshair and proceeds up.

X-ray Point Analysis of Concrete Paste Blue line is from paste at bottom of view and shows high K, no S Red line is from paste toward top of view and shows S without K.

Thermal Analysis Thermogravimetric Analysis (TGA) and control console Differential Scanning Calorimetry (DSC) SDTA = Simultaneous Differential Thermal Analysis (DTA) and Thermogravimetric Analysis (TGA)

Thermogravimetric Analysis (TGA) of Limestone and Dolomite MgCO 3 decomposition CaCO 3 decomposition

Differential Scanning Calorimetry (DSC) of Portland Cement Cements contain different types of sulfur minerals which influence how the cement reacts with water. Gypsum is the normal sulfate mineral used to control the set-time of Portland cement. Gypsum Bassanite

X-ray Diffraction (XRD) Atomic arrangement, crystal structure

X-ray Diffraction of Sulfates in Portland Cement Pattern shows three sulfate minerals: Gypsum, Bassanite, and Anhydrite which influence the setting of portland cement Gypsum Anhydrite Bassanite

X ray Fluorescence (XRF) (bulk chemistry down to ppm levels) X ray spectrometer schematic status screen Robotic sample changer

X-ray Fluorescence of Trace Elements NBS97a standard from the National Institute for Standards and Technology (NIST) compared to ultra pure alumina (alpha-Al 2 O 3 ) Full scale is about 1000 ppm of Sr

X-ray Fluorescence of Trace Elements Cr in high-purity alumina. Full scale is about 100 ppm Cr. The sample denoted in blue contained about 2.5 ppm Cr. The limit of detection is about 0.4 ppm at 200 seconds of counting.

Optical Microscopy Transmitted light normal illumination Transmitted light crossed polarization

Partial List of Clients Amana American Meat Protein Corporation (AMPC) Iowa Department of Transportation Iowa Thin Films Maytag PMX Raytheon Sauer Square D Townsend Engineering U.S. Filter

Typical Applications

Contact Information Web: E mail: Jerry Amenson manager, SEM, TA 23 Town Engineering Scott Schlorholtz XRD, XRF, TA 68 Town Engineering Warren Straszheim SEM, EDS, image analysis 46 Town Engineering