Materials Analysis and Materials Analysis and Research Laboratory (MARL)Research Laboratory (MARL)

Rooms 23-68 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 - 100xno 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(CO3 )2

showing oxygen and carbon peaks

2 4 6 8 10Energy (keV)

0

100

200

300

400

cps

Cu

Zn

Si Pb SnSn

Cu

Zn

Cu Zn

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)

2 4 6 8 10Energy (keV)

0

100

200

300

cps

Cu

Zn

Pb

Cu

Zn

Cu 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

0

10

20

30

40

50

60

-10 0 10 20 30 40 50 60 70

Pos., mm

Ato

mic

%

Mn

Ni

Ga

X ray map of concrete components

Brightness reflects the concentration of the element

Ettringite (S+Al)

Image Al

Si

KMg

NaS

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.

1 2 3 4Energy (keV)

0

50

100

150

200

cps

C

O

NaMg

Al

Si

S K

Ca

Ca

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

MgCO3

decomposition

CaCO3

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

AnhydriteBassanite

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-Al2O3)

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 lightnormal illumination

Transmitted lightcrossed 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 ApplicationsContaminated soil locate and characterize lead minerals

Solder joints characterize bubble distribution (strength)measure joint fillet size and shape (strength)

Anodized metal characterize contaminantsLaser scalpels document failure modes and contaminationAlloys quantitative analysis to verify compositionIngots Measure variation in composition with length/positionElectrical contacts Document migration of elements with useConcrete Measure air void content and distribution

Characterize aggregateIdentify failure modes

Corrosion products Identify corrosion products and mode of attackNew compounds Determine stoichiometry for new phasesContamination Identify contaminant particles to determine their source

Contact Information

Web: www.marl.iastate.edu

E mail: marl@iastate.edu

Jerry Amensonmanager, SEM, TA

23 Town Engineering294 8752jamenson@iastate.edu

Scott SchlorholtzXRD, XRF, TA

68 Town Engineering294 8761sschlor@iastate.edu

Warren StraszheimSEM, EDS, image analysis

46 Town Engineering294 8187wesaia@iastate.edu