Materials Characterization

We exercise a wide range of techniques to reveal a material’s microstructure and composition from the macro to nanoscale in 2D or 3D. 

• Scanning Electron Microscopy
Scanning Electron Microscopy

Scanning Electron Microscopy (SEM) scans a focused electron beam over a surface to create an image. This image provides information about the surface topography and composition.

The maximum resolution obtained in an SEM depends on multiple factors, like the electron spot size and interaction volume of the electron beam with the sample. On average, a modern full-sized SEM provides resolution between 1-20 nanometers whereas desktop systems can provide a resolution of 1000 nm or more.

The two most common detectors used in scanning electron microscopy are the secondary electron (SE) detector and the backscatter electron (BSE) detector.

In secondary electron imaging, the secondary electrons are emitted from very close to the specimen surface. In back-scattered electrons (BSE), beam electrons are reflected from the sample by elastic scattering, which emerge from deeper locations within the specimen. BSE are often used in analytical SEM along with the spectra made from the characteristic X-rays, because the intensity of the BSE signal is strongly related to the atomic number (Z) of the specimen. BSE images can provide information about the distribution of different elements in the sample.

Energy Dispersive X-Ray Spectroscopy allows us to determine the elemental makeup of the sample being imaged.

Detect elements from Boron to Americium

• Provide point analysis on areas of interest
• Provide line analysis across regions of interest
• Provide entire elemental maps (up to 10 elements)
• Overlay EDS data with image data EDS is critical for foreign particle analysis, process control, evaluating diffusion rates, and much more



Nanotubes

Low to high magnification images of patterned carbon nanotubes on Silicon.

 

 



Metal Powders
Low magnification image of metal powder to examine morphology and size before an additive print.​​​​​​

• Focused Ion Beam Microscopy
Focused Ion Beam Microscopy

The Focused Ion Beam (FIB) is used to modify the surface of a specimen through a sputtering process.  The ability to control the ion beam intensity and energy as well as precise patterning allows milling of the surface at a nanometer resolution. Along with removing material, material can be added to the specimen through ion beam assisted decomposition of precursor gasses delivered to the vicinity of the specimen through a gas injector system.  The FIB is generally combined with a field emission scanning electron microscope (SEM).  A 52o angle between the ion beam and the electron beam allows concurrent high-resolution imaging of the FIB milled surface.

One of the main applications of the FIB is for subsurface defect analysis. For example, if a bump were present on the surface of a sample, the FIB can mill a precise trench at the location of the bump. SEM imaging of the trench face will reveal the subsurface characteristics of that bump.  When an energy dispersive x-ray system (EDS) is attached to the FIB-SEM workstation, a full elemental analysis of the bump can be performed.

Another powerful application of the FIB is to prepare site-specific samples that can be examined in the transmission electron microscope (TEM). We have used this capability to devise a method of preparing TEM samples containing a portion of a crack front. This “crack tip” TEM analysis has been used to better understand mechanisms of crack propagation in Ni base superalloys. FIB can also be used to modify the surface of a sample through micromachining features such as nano-hole arrays or micro pillars which can subsequently be compressed using a nanoindentor.

Focused Ion Beam Systems:

• Helios 600 FIB/SEM
• Nova Dual Beam
• Ga Ion Source, 1.3pA-22nA
• Pt Gas Injector System
• Omniprobe Micromanipulator



SEM image of FiB Cross-section

SEM image of a FIB prepared cross-section through a specific material area.

 

 



Lift out Movie
Movie of FIB lift out process to produce electron transparent samples.​​​​​​

• Quantitative Image Analysis
Quantitative Image Analysis

Quantitative image analysis is the utilization of digital image processing to extract meaningful information from images. We employ computers to provide a wide range of digital image processing techniques to analyze images and provide metrics that can be used to track processes and solve problems.

Image analysis can be broken down into two main categories: Image processing and image analysis. Image processing is utilized to enhance features of interest and uses an incredible array of algorithms that transforms the digital information in images. Image analysis is the actual quantification of features of interest and includes Object-based image analysis. Object-based image analysis includes the process of segmentation of features of interest from the background and classification of detected features by grouping individual pixels into homogeneous objects. The relationship between these pixels and how they may relate to objects is a powerful tool in detecting and classifying features of interest.

Images can be in any size or format and from any instrument.

Integrated Image Analysis Equipment

• Nikon Epiphot 200 Inverted Reflected Light Microscope
• Marzhauser 100mm x100mm scanning stage with utofocus
• Lumenera 1600x1200 2Megapixel camera
• Dell Optiplex 760 Workstation
• Dell UltraSharp 30inch LCD monitor

Light Microscopy Imaging Equipment

• HIROX 3D Digital Microscope
• Zeiss Axio Observer Inverted Light microscope with scanning stage, autofocus, and 5megapixel camera

Software

• Clemex Vision Image Analysis software
• ImageJ (Fiji)
• Photoshop CS/Elements
• Image Processing Tool Kit (Photoshop plug-in)
• FEI Avizo Fire 3D Analysis Software



Coding to Represent Phase Distribution



Identification of Magnetic Flake Orientation

• High Resolution Computed Tomography
High Resolution Computed Tomography

Micro-CT is a three-dimensional (3D) non-destructive characterization tool that uses X-rays to determine the internal structure of objects through the detection of different densities within the object being imaged. X-rays generated from a target (typically Copper or Tungsten) are passed through an object on a rotating stage. Two-dimensional (2D) projection images are recorded on a detector while the object is rotating through 360 degrees. These 2D images are then back projected using specialized algorithms to create a 3D representation of the internal structure of the object. Contrast in the CT images are produced by density differences present in the object. This allows one to travel through the volume in any direction and angle, thus revealing complex hidden surfaces within the object. The imaging resolution scales with the size and material density of the object being imaged, and can vary from 1 µm/pixel to 50 µm/pixel for most types of specimens imaged, although a lower resolution is achievable too. The total scan time is anywhere between half hour to two hours, depending upon the shape and size of the object. Also, compared to other high-resolution imaging techniques, the sample preparation required for imaging using the micro-CT is minimal. 

How is Micro-CT used ?

• Detection of defects such as cracks and porosity
• Metrology for comparison of nominal to actual 
• Reverse engineering
• CAD modeling

Technical specifications of the Micro-CT instrument at GE

• Equipment: BHGE Vtomex M 300 with dual tube configuration (300 kVp micro-focus tube and 180 kVp nano-focus tube)
• 250RT Direct X-ray detector with 2024 x 2024, 200 µm/pixel pitch
• Resolution range: 1 µm – 120 µm/pixel
• Max weight on sample stage: 50 lbs
• Max dimension of sample to be imaged: 9 inches
• Large sample chamber with air environment
• Add-on module available for heating and cooling samples during imaging

 

Strengths	Limitations
Non-destructive Minimal sample prep required 3D information Quantitative analysis	No chemical information obtained Large data volumes



Carbon Fiber Composite
3D rendering of porosity in a carbon fiber sample from microCT imaging.



Virtual teardown of a Battery
3D rendering of an intact battery cell to pinpoint the root of the failure.

• Scanning Probe Microscopy
Scanning Probe Microscopy

Scanning Probe Microscopy (SPM) is a characterization tool to study properties of surfaces. In this technique, a sharp probe operates in the near field that scans over the surface while maintaining a very close spacing to the surface. In their first applications, SPMs are mainly used for measuring 3D surface topography (atomic force microscopy, AFM), but can be used to measure many other surface properties as well such as electrical properties, magnetic properties and adhesion.

Images can be collected in “contact” mode, in which the tip is physically in contact with the surface, or in “tapping” mode, wherein the tip is vibrated at its resonant frequency.  Contact mode applies higher forces between the tip and the surface and typically has higher resolution, while tapping mode has greater sensitivity. In the tapping mode, the tip oscillates at some frequency “tapping” along the surface and applies lighter forces on the surface as compared to the contact mode. 

The sharp probe “feels” its way over the surface to measure topography with nano-scale resolution in x-y and angstrom resolution in the Z.  The deflection change of the laser is noted by the detector and converted into topography.  The smallest area that can be scanned is on a nm scale and the largest scan is 100um x 100um.  The Piezo that steers the scanner head has a Z movement limitation of 5um. 

SPM has extensive applications to determine surface roughness, thicknesses of thin film, dimensions of small features on surfaces, analysis of surface defects, MEMS analysis and studies of photovoltaic devices. Throughout the years, the Material Characterization team at GE has analyzed a diverse set of materials by SPM to address a wide variety of industrial applications.

How is Scanning Probe Microscopy Used?

• 3D surface topography 
• Roughness measurements 
• Electrical properties (low conductivity, capacitance) 
• Magnetic properties
• Adhesion properties

Technical Specifications of SPM
Equipment: Digital instruments (now Bruker) Dimension 3000 and Multimode
Z Resolution: angstrom resolution
X-Y Resolution/Probe Size: nano-scale resolution tip diameter dependent
Imaging/Mapping: Yes

 

Strengths	Limitations
Excellent resolution in the nano range Provides 3D images of surfaces Provides surface roughness values	Z range must be lower than 5µm Scan area <=100X100 5µm2 Samples must be flat



Image of a Nano-indent Demonstrating Depth Resolution By Scanning Probe Microscopy

• Metallographic Sample Preparation
Metallographic Sample Preparation

Metallographic Sample Preparation

The ability to image and analyze sample microstructure is wholly contingent upon the ability of preparing a specimen for imaging. GE has over 35 years of experience in metallography and provides world class metallographic sample preparation of all types of materials ranging from soft polymers and delicate coatings to nickel-based super alloys and ceramic matrix composites. The team utilizes equipment of the types listed below and in-house developed techniques to reveal complex microstructure, enabling all dependent imaging and analysis techniques.

Equipment: 

• Struers Abrapol-10 automatic polisher (1”, 1.25”, 1.5”, 2”, 2”x3” specimen capabilities)
• Struers Hexamatic automatic polisher with auto-feed specimen holders (1”, 1.25”, 1.5”, 2” specimen capabilities)
• ATM Saphir 550 automatic polisher (1”, 1.25”, 1.5”, 2”, 2”x3” specimen capabilities)
• ATM Brilliant 220 automatic high-speed wafering saw (up to 7” wafering blade)
• ATM Brilliant 250 automatic cutoff saw (up to 12” cutoff blade)
• ATM Vibromet
• Syntron vibratory polisher
• ATM Opal 46 mounting press (1”, 1.25”, 1.5”, 2” specimen capabilities)

Example Specimen Materials:

• Plastics
• Ceramics
• Ceramic matrix composites
• Metals
• Alloys
• Silicon carbide
• Fibers
• Powders

Mounting Materials: 

• Slow cure 2-part epoxy 
• Thermal set conductive epoxy 
• Thermal set bakelite 

 

Special Techniques	Strengths	Limitations
Super-prep for nickel-based super alloys Chemical etching Non-aqueous sample preparation Additional techniques developed per individual request	Dedicated team focused solely on sample preparation Preparing a wide variety of materials Established preparation methods for aqueous and non-aqueous specimens Variety of mounting materials Chemical etching capabilities	Specimen size is limited to a 2” diameter mount



Cross-sectional Mounts of Metal Components

 

 



Cross-sectional Mounts of Fiber
 

• Electron Probe Micro Analysis
Electron Probe Micro Analysis

The Electron Probe Micro-Analyzer (EPMA), or “microprobe”, is a variant of the scanning electron microscope and uses a high-energy electron beam to determine the elemental composition of solid samples. When atoms that are excited by the electron beam relax, X-rays with energies unique for each element are emitted. A quantitative chemical analysis is obtained by comparing X-ray counts on standards with those emitted from the “unknown." EPMA uses Wavelength Dispersive Spectrometers (WDS) to collect characteristic X-ray signals, as opposed to the more common Energy Dispersive Spectrometers (EDS) typically found on scanning electron microscopes. WDS spectrometers have superior energy resolution and signal-to-noise ratios compared to EDS systems, reducing or eliminating problem overlaps while improving detection limits. WDS systems require a specific geometry. Analyses must be performed on flat, polished samples with a spatial resolution of ~1-2 m2; smaller spot sizes are achievable using our high-resolution JEOL 8530F (Field Emission) instrument.

How is EPMA Used?

• Spot analyses on individual phases
• Composition Profiles
• Composition Maps
• Thin film analyses

 
Technical Specifications of EPMA Instruments at GE
Equipment:  JEOL 8200 & JEOL 8530F
Signal Detected: Characteristic X-rays, Secondary and Back-scattered Electrons
Elements Detected: Boron to Uranium
Detection Limits: ~0.1 wt% (lower in some cases)
Depth Resolution: ~200 nm
Imaging/Mapping: Yes 

Strengths	Limitations
Quantitative Automated Fast (minutes per analysis) High-resolution imaging	Samples must be vacuum compatible and stable under electron beam

 



Quantitative Compositional analysis via wavelength dispersive spectroscopy

• Transmission Electron Microscopy
Transmission Electron Microscopy

Transmission electron microscopy (TEM) is the evaluation of thin specimen material at sub-nanometer resolution scales, using a focused high energy coherent electron beam in transmission mode.

Researchers at GE Global Research have extensive experience utilizing TEM based techniques for characterizing a vast array of materials: Metallic, ceramic, semiconductors and organics – polymers and life sciences.

The specimen sizes (specimen preparation) have a thickness of <200nm (3mm disks by electropolishing or 10-50 microns by FIB).

The image formed by the electrons transmitted or scattered through the specimen are recorded at very high magnifications using a series of electromagnetic lenses. Images can be acquired in different modes representative of chemistry and microstructure. Diffraction contrast imaging is beneficial for studying crystallographic defects such as dislocations. Information from specific sites such as defects and precipitates can be obtained by electron diffraction and compositional analysis. Phase contrast imaging or high resolution TEM (HRTEM) which allows atomic scale investigation can be very insightful in understanding lattice, precipitates, interfaces and defect structures.

Taking advantage of specimen-electron interaction signals generated, such as characteristic X-rays (Energy dispersive spectroscopy – EDS) and energy loss of transmitted electrons (Electron energy loss spectroscopy – EELS), local chemical composition information can be obtained and quantified. These elemental analyses can be conducted at the nanometer scale. Local features can be interregated in point analysis. Areas can be interregated by EDS or EELS spatial composition maps.

The scanning transmission electron microscopy (STEM) mode enables rastering of a highly focused beam across the specimen region of interest allowing various signals to be recorded as a function of position. Chemically sensitive Z-contrast images can be obtained while simultaneously acquiring EDS/EELS maps/ line-scans or energy filtered elemental maps (EFTEM-EELS).

Applications: High spatial resolution analyses at sub-nanometer scale, composition and microstructure analysis, crystallography and defect analysis.

Instrumentation available for S/TEM analysis (200kV):

Instrument	Pt. resolution	Information limit	HAADF-STEM resolution	EDS	EELS	GIF (imaging filter)	Tomography
Tecnai Osiris	2.5 Å	1.4 Å	1.8 Å	Super-X windowless (4 quad)	Gatan Enfinium	-	-
Titan Themis	2.4 Å	1.2 Å	1.6 Å	Super-X windowless (4 quad)	Gatan Quantun ERS	√	√



DNA
Transmission electron micrograph of DNA on a carbon grid.



Microstructure of Structural Alloy
Bright Field scanning transmission electron micrograph and energy dispersive image of alloy microstructure.
 

• Energy Dispersive Spectroscopy
Energy Dispersive Spectroscopy

Energy dispersive x-ray spectroscopy (EDS, EDX or EDXS) is an analytical technique used to identify the elemental components of a solid surface.  This technique relies on a source to excite the atoms on the solid surface (>1micron) which then emit an x-ray when relaxing to ground state.  The collected x-ray spectrum will contain both qualitative and quantitative information about the sample composition.  

The energy of an emitted x-ray is specific to the atomic structure of the element it came from.  This information can be used to identify peaks in collected spectra. The intensity of each peak is related to the concentration of that element in the sample.  Peak intensity can then be used to obtain quantitative information.  The accuracy of a quantitative analysis will depend on the sample and the availability of appropriate standards.

EDX data can be collected in spot, raster, line scan or 2D mapping modes.  

Our lab has EDS systems on several scanning electron microscopes (SEM’s), our focused ion beam systems (FIB’s) our transmission electron microscopes (TEM’s) as well as a dedicated XRF instrument.

How is EDS Used?

• Small feature analysis (defects, particles, MEM’s and microelectronic structures)
• Surface analysis
• Compositional 2D mapping
• Thin film analysis composition top down or cross sections
• Metallurgical analysis
• Simultaneous secondary electron imaging

 

Strengths	Limitations
Fast  Identification of unknowns 2D elemental mapping	Standards required for quantitation Insulators can be difficult Samples must be vacuum compatible Detection sensitivity typically ≥1at%

 



EDS image Indicating the Elemental Distribution In An Alloy

The team analyzes the top most atomic layers of a surface with electrons, photons, ions and scanning probes.

• Auger Electron Spectroscopy
Auger Electron Spectroscopy

Auger Electron Spectroscopy (AES or Auger) is a surface-sensitive analytical technique that utilizes a high-energy electron beam as an excitation source to determine the elemental composition of a sample. Atoms that are excited by the electron beam can subsequently relax, leading to the emission of “Auger” electrons. The range of kinetic energies of the emitted Auger electrons is from 0-3kV. Therefore, the characteristic Auger electrons interrogate the top 3-10nm of the sample.

The electron beam can be scanned over a variably sized area, or it can be directly focused on a specific surface feature of interest. This ability to focus the electron beam to diameters of 10-20nm makes Auger Electron Spectroscopy an extremely high-resolution tool for elemental analysis of small surface features. When used in combination with a sputtering ion gun, Auger can also perform compositional depth profiling.

Larry Harris, a GE researcher, developed an instrument to detect Auger electrons and proposed a differentiated spectrum as the method of quantification in 1967. Throughout the years, the Material Characterization team at GE has analyzed a diverse set of materials by Auger to address a wide variety of industrial applications.

Auger analysis has extensive applications in coating analysis to determine composition as a function of depth and coating thickness, small particle analysis, in determining contamination sources and analyzing defects. We have developed unique methods to use a Focused Ion Beam to create electron transparent samples for compositional analysis vis AES. In addition, our instrument is equipped with an In-situ fracturing to examine contamination-free surfaces.

How is Auger Electron Spectroscopy Used?

• Defect and particle analysis
• Surface analysis
• Small-area depth profiling
• Thin film analysis composition
• Metallurgical analysis
• Chemical bonding information
• Simultaneous secondary electron imaging

 

Technical Specifications of Auger Analysis
Equipment: PHI 700 
Signal Detected: Auger electrons from near surface atoms
Elements Detected: Li-U
Detection Limits: 0.1-1at%; sub-monolayer
Depth Resolution: 20-200Ǻ, depth profiles 5nm-2um
Imaging/Mapping: Yes, 8 nm resolution
Lateral Resolution/Probe Size: >=70Ǻ (field emission)

 

Strengths	Limitations
Small area analysis (~20nm minimum) Excellent surface sensitivity (3-10nm information depth) Good depth resolution	Standards required for best quantification Insulators can be difficult Samples must be vacuum compatible Detection sensitivity typically ≥1at%

 



Auger Elemental Map
Auger elemental map from a cross sectional FIB lift out, illustrating the oxide formations.
 



Auger Depth Profile
Using an energetic ion beam to remove layers of the material, Auger spectra are collected at each depth to determine composition.
 

• X-ray Photoelectron Spectroscopy
X-ray Photoelectron Spectroscopy

X-ray Photoelectron Spectroscopy (XPS) is also called electron Spectroscopy for chemical analysis (ESCA). This is a surface-sensitive analytical technique that utilizes a monochromatic X-ray beam as an excitation source to determine the elemental composition of a sample. The X-ray photon transfers its energy to a core-level electron imparting enough energy for the electron to leave the atom. 

These emitted electrons are subsequently separated according to the energy and counted. The energy of the photoelectrons is related to the atomic and molecular environment from which they originated. The number of electrons emitted is related to the concentration of the emitting atom in the sample. The photoelectrons interrogate the top 5-10nm of the sample. The electron beam can be scanned over a variably sized area and when used in combination with a sputtering ion gun, XPS can also perform compositional depth profiling.

XPS analysis has extensive applications in thin films and coating analysis to determine surface composition, composition as a function of depth, thicknesses of thin film, determining contamination sources and analyzing surface defects. Throughout the years, the Material Characterization team at GE has analyzed a diverse set of materials by XPS to address a wide variety of industrial applications.

How is X-ray Photoelectron Spectroscopy Used?

• Surface analysis
• Depth profiling
• Thin film analysis composition
• Thin film thicknesses
• Chemical bonding information

Technical Specifications of XPS
Equipment:  Kratos AXIS Ultra DLD 
Signal Detected: Photoelectrons from the surface region
Elements Detected: Li-U
Detection Limits: 0.1at%; sub-monolayer
Depth Resolution: 5-10nm, depth profiles 500nm
Imaging/Mapping: Yes
Lateral Resolution/Probe Size: >=25nm 

 

Strengths	Limitations
Excellent surface sensitivity (5-10nm information depth) Good depth resolution Provides chemical information of the detected elements	Samples must be vacuum compatible Detection sensitivity typically ≥0.1at%

 

 



X-ray Photoelectron Spectrometer.

• Time-of-Flight Secondary Ion Mass Spectrometry
Time-of-Flight Secondary Ion Mass Spectrometry

Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) is a surface analysis technique that utilizes a high energy pulsed and focused ion beam to eject submonolayer amounts of material from the surface being analyzed.  ToF-SIMS provides high detection sensitivity (ppm to ppb), high surface specificity and high mass resolution.   All elements (including H), and their isotopes are simultaneously detected.  With the advent of cluster ion sources, ToF-SIMS is now able to detect high mass molecular species with high chemical sensitivity.   A full mass spectrum (0 to a few thousand amu) is collected and saved at every volume element.  Images are collected at each depth during a depth profile measurement providing 3D chemical information.

The ion beam can be rastered over a 500 micron area (or smaller).  Larger areas can be analyzed by moving the sample stage.  All ToF-SIMS analysis starts with rapid spectral evaluation of the material.  Certain peaks (elements, molecules, or molecular fragments) are selected to form a starting peak list for imaging and/or depth profile analysis.  As unexpected species appear, for instance at an interface during a depth profile analysis, they are added to the peak list and are retrospectively analyzed.  The ToF-SIMS analyst does not need to select all of the species to analyze at the start of the measurement.

We have developed numerous unique methods to analyze complex materials, including polished SEM cross sections to analyze tens to hundreds of microns below the sample surface and in-situ plasma cleaning of surfaces, to highlight two.

James McHugh and James Sherfield from Knolls Atomic Power Laboratory first reported secondary positive ion emission from industrially relevant materials in 1963.  Throughout the years, the Material Characterization team at GE has analyzed a diverse set of materials by ToF-SIMS to address a wide variety of industrial applications. 

How is ToF-SIMS Used?

• Surface spectral analysis
• Identification of unexpected species, especially sub-surface
• Analysis of hydrogen
• Isotopic analysis
• Analysis of molecular species, and detection of molecular decomposition
• Small-area to large area depth profiling; thick layers are analyzed in cross section
• 3-dimensional depth profiling

 

Technical Specifications of our ToF-SIMS Instrument
Equipment:  IonTof  ToF.SIMS5

• 25 kV 3 lens cluster liquid metal ion gun
• Dual source column with electron impact ion gun (oxygen or argon) and Cs
• Pulsed SE detector
• Low energy electron flood gun for charge compensation

 

Signal Detected: Secondary ions; secondary electrons (w/ pulsed SE detector)
Elements Detected: H-U, along with all isotopes
Molecular species:  Are detected
Detection Limits: ppm to ppb
Imaging/Mapping: Yes, <100 nm resolution
Depth Resolution: Can be as high as <1 Ǻ depth profiles 

 

Strengths	Limitations
Both elemental information and molecular information is obtained during a measurement Full mass spectrum is saved at every volume element Excellent surface specificity and sensitivity  Ability to detect very thin molecular layers (not possible via other techniques) Excellent depth resolution 3D depth profile analysis	Standards required for quantitative analysis Samples must be vacuum compatible Sample height must be about a cm or less

 



High mass to charge ratio ToF-SIMS imaging

• Scanning Probe Microscopy
Scanning Probe Microscopy

Scanning Probe Microscopy (SPM) is a characterization tool to study properties of surfaces. In this technique, a sharp probe operates in the near field that scans over the surface while maintaining a very close spacing to the surface. In their first applications, SPMs are mainly used for measuring 3D surface topography (atomic force microscopy, AFM), but can be used to measure many other surface properties as well such as electrical properties, magnetic properties and adhesion.

Images can be collected in “contact” mode, in which the tip is physically in contact with the surface, or in “tapping” mode, wherein the tip is vibrated at its resonant frequency.  Contact mode applies higher forces between the tip and the surface and typically has higher resolution, while tapping mode has greater sensitivity. In the tapping mode, the tip oscillates at some frequency “tapping” along the surface and applies lighter forces on the surface as compared to the contact mode. 

The sharp probe “feels” its way over the surface to measure topography with nano-scale resolution in x-y and angstrom resolution in the Z.  The deflection change of the laser is noted by the detector and converted into topography.  The smallest area that can be scanned is on a nm scale and the largest scan is 100um x 100um.  The Piezo that steers the scanner head has a Z movement limitation of 5um. 

SPM has extensive applications to determine surface roughness, thicknesses of thin film, dimensions of small features on surfaces, analysis of surface defects, MEMS analysis and studies of photovoltaic devices. Throughout the years, the Material Characterization team at GE has analyzed a diverse set of materials by SPM to address a wide variety of industrial applications.

How is Scanning Probe Microscopy Used?

• 3D surface topography 
• Roughness measurements 
• Electrical properties (low conductivity, capacitance) 
• Magnetic properties
• Adhesion properties

Technical Specifications of SPM
Equipment: Digital instruments (now Bruker) Dimension 3000 and Multimode
Z Resolution: angstrom resolution
X-Y Resolution/Probe Size: nano-scale resolution tip diameter dependent
Imaging/Mapping: Yes

 

Strengths	Limitations
Excellent resolution in the nano range Provides 3D images of surfaces Provides surface roughness values	Z range must be lower than 5µm Scan area <=100X100 5µm2 Samples must be flat

 



Image of a Nano-indent Demonstrating Depth Resolution By Scanning Probe Microscopy

• Chromatic White Light Profilometry
Chromatic White Light Profilometry

Chromatic White Light Profilometry (CWLP) is a characterization tool to study surfaces of materials. This technique is based on a principle called axial chromatism, which uses a white light source that passes through an objective lens with a high degree of chromatic aberration.

The objective lens’ refractive index will vary in relation to the wavelength of the light. In effect, each separate wavelength of the incident white light will refocus at a different distance from the lens (different height). When measured sample is within the range of possible heights, a single monochromatic point will be focused to form the image. Due to the confocal configuration of the system, only the wavelength in focus will pass through the spatial filter with high efficiency, which causes all other wavelengths to be out of focus.

SPM has extensive applications to determine surface topography, surface roughness, dimensions of features on surfaces and analyzing surface defects. Throughout the years, the Material Characterization team at GE has analyzed a diverse set of materials by CWLP to address a wide variety of industrial applications.

How is Scanning Probe Microscopy Used?

• 3D surface topography 
• Surface features
• Roughness measurements 
• Step heights

 

Technical Specifications of SPM
Equipment: Nanovea ST500; FRT MicroProf 100
Z Resolution: 10nm to mm
X-Y Resolution/Probe Size: 1µm and up
Imaging/Mapping: Yes
 

StrengthsLImitations

• No sample preparation is required
• Excellent resolution in variety ranges
• Provides 3D images of surfaces
• Provides variety of parameters such as surface roughness, texture and height

• Best Z resolution is 10nm 
• Minimal probe size (X-Y Resolution) is 1µm

 



2 D Chromatic White Light Profilometry of a Silicon Diffraction lens array.



3D Chromatic White Light Profilometry of a Silicon Diffraction lens array

In order to understand a material’s crystal structure, phase transformation, and stress/strain we employ  X-ray, neutron, and electron beams.

• Electron Backscatter Diffraction
Electron Backscatter Diffraction

Electron backscatter diffraction (EBSD) is an analytical technique that utilizes a scanning electron microscope (SEM) to measure crystallographic features of a sample. A high-energy electron beam is accelerated onto the surface of a grounded sample. These electrons penetrate the sample and are scattered within the material. Some of the electrons exit and collide with the screen of an EBSD camera. Electrons scattered by the periodic crystalline lattice appear as pairs of parallel light and dark lines (Kikuchi lines). Crystallographic information can be derived from the pattern of these lines.

The electron beam can be scanned over a variably sized area, or it can be directly focused on a specific feature of interest. The ability to focus the electron beam to a diameter <10nm enables the analysis of very fine features. The diffraction signal is generated in the top ~25nm of the sample, so it is necessary to have a flat surface with a high-quality prep (i.e., vibratory polishing).

Starting in 1992, GE Global Research drove the development of HKL Technologies' first fully automated EBSD system. Previous systems were only reliable for cubic crystal systems. The new system was successfully delivered in 1995 and was fully capable and reliable for any crystal structure. At the time, this achievement was particularly important for characterizing dual-phased alloys used in aviation, such as titanium, which is composed of both cubic and hexagonal phases.

Electron Backscatter Diffraction Capabilities

• Crystal orientation mapping
• Crystallographic texture evaluation
• Grain size distribution
• Plastic strain quantification
• Transmission Kikuchi diffraction
• Phase identification
• Pattern simulation
• Simultaneous EBSD/EDS
   

Technical Specifications
Equipment:  Oxford Symmetry, Oxford NordlysMax2, Oxford Nordlys, Bruker e-FlashHR
Signal Detected:  Backscattered electrons
Lateral Resolution:  ~25nm in X, ~50nm in Y
Depth Resolution:  ~25nm
Imaging/Mapping:  Yes
 

Strengths	Limitations
Wide scale range (nm to mm) Large area mapping (up to 2” x 4”) Analysis of individual features as fine as 100nm Simultaneous acquisition with elemental chemistry	Samples must be crystalline Samples must be vacuum compatible Samples must polish well Insulators can present challenges

 



Orientation map of an additively built alloy (diameter = 5mm). EBSD reveals relationship between build pattern and crystal orientation.

• X-ray Diffraction
X-ray Diffraction

Ever since its discovery more than 100 years ago, the X-ray diffraction (XRD) has been one of the most fundamental and popular material characterization technique especially for the crystalline materials.  The X-ray wavelength is comparable with the materials’ interatomic distances – therefore crystalline material behaves as natural diffraction grating for the incident monochromatic X-ray beam and results in scattered or diffracted X-rays with specific angular distribution, as function of crystalline property of samples.  Those observed XRD patterns contain structural fingerprint data including (not limited to) crystal structure, phase(s), preferred orientation (texture), crystalline size, crystallinity and strain.  Our state-of-the-art analysis method allows to extract such valuable information from the raw XRD patterns.

The GE XRD lab is equipped with six dedicated machines for the best quality data.  They can cover from the typical powder form samples to arbitrary shaped bulk articles, from room temperature to the high temperature (up to ~2000 ˚C) and from the conventional Bragg-Brentano reflection geometry to the transmission or parallel beam configuration.  The micro-XRD system with 2D area detector also enable us to perform pin-point analysis or mapping on non-homogeneous samples (beam size from 2 to 0.05 mm).  We also maintain our ICDD database as well as other analysis software up-to-date.

Applications

• Crystalline phase(s) identification and/or quantification (up to ~ 1wt%) for any type of polycrystalline samples (some shape restrictions may apply).
• Quantification of amorphous phase by spiking (sample should be in powder form) or by line shape/intensity comparison (not necessarily in the powder form).
• Crystallite size analysis of polycrystalline powder or flat surface sample like thin film or polished bulk.
• Residual stress analysis for deposited thin film or machined/stressed parts.
• Texture analysis of thin film or directionally solidified materials.
• Whole profile analysis for precise structural parameters like lattice parameters, d-spacing of certain atomic layers, refined structural models, quantification of multiphase material.
• X-ray reflectivity (XRR) – thickness, density and roughness analysis for thin film or multilayer samples.
• Grazing Incidence XRD (GIXRD) – thin film or multilayer surface analysis as function depth.

 

Typical sample forms: 
Powder samples are ideal for (but not limited to): Phase identification/quantification, whole profile analysis, crystallite size analysis
Thin film or bulk samples with (polished) flat surface are ideal for (but not limited to): Phase identification/quantification, residual stress, texture, GIXRD, XRR analysis
Irregularly shaped samples ideal for (but not limited to): Phase identification/quantification, Residual stress.

 

Strength	Limitation	Instruments
Non-destructive Quantitative if structure models are available for all observed phases Optional non-ambient atmosphere (air/moisture sensitive sample cases – need special sample prep) High temperature in-situ experiments (room temperature ~ 2000 ˚C) Optional enhanced surface sensitivity for thin films (GIXRD, XRR) Broad acceptable sample form – minimal or no sample prep necessary (subject to specific goals/tasks).	Amorphous phase cannot be identified Minimum X-ray beam spot size: ~0.05 mm Not element specific – sometimes need extra elemental information from spectroscopy like XRF.	Bruker D8 Advance with SOL-XE detector (Cu K rad.) Bruker D8 Advance with Anton Paar HTK 2000 high temperature stage (Cu K rad.) PANalytical Empyrean with PIXcel-3D detector (Cu K rad.) Bruker D8 Discover with VÅNTEC-500 detector (Cu K rad.) Rigaku UltraX 18 high-frequency rotating anode with Inel detector (Mo K rad.) Rigaku UltraX 18 high-frequency rotating anode with Mar345 detector (Mo K rad.)

 



Pole figures of (111) reflection from cubic phase of thin film specimen grown in different conditions

• Synchrotron Neutron Techniques
Synchrotron Neutron Techniques
Synchrotron and neutron encompass a wide range of characterization techniques available at large-scale user facilities across the country.  They are mostly used by academia for fundamental research, but increasingly they are used by industrial researchers for advanced characterization for challenging problems which cannot be solved by using conventional laboratory instrumentation.
Synchrotron and neutron techniques can be used for structural, compositional and morphological characterization of materials by scattering and diffraction, imaging and spectroscopy.   Comparing with laboratory techniques, they are superior in many aspects including spatial, angular, energy, and temporal resolutions and high throughput capabilities enabled by current robotic and machine-learning technologies.
In recent years, synchrotron and neutron are more frequently used in in-situ measurements during materials testing and processing, e.g., during fatigue or creep testing of engineering materials; such measurements can also be carried out at system level, e.g., during battery charge and discharge cycles.
We gain access to these user facilities in various modes, from proprietary measurements to collaborative research.  Typical turnaround time is from a couple of weeks to several months, depending upon nature of the work.  We have extensive expertise in many synchrotron and neutron based techniques, especially those listed below.
Most useful synchrotron and neutron techniques
• High-energy (60-200 keV) X-ray diffraction
• Neutron diffraction (complementary to X-ray diffraction)
• Pair-Distribution Function (PDF) analysis (for non-crystalline materials) 
• High-resolution X-ray or neutron powder diffraction (mail-in)
• Microtomography and imaging (X-ray or neutron)
• X-ray absorption spectroscopy (EXAFS and XANES)
• Small-angle X-ray or neutron scattering (SAXS, SANS)
• Grazing incidence X-ray diffraction 
 
Common applications of synchrotron and neutron techniques
• Non-destructive residual stress analysis
• Materials behaviors at high temperatures or under load
• Deformation (including dislocation) of metals and alloys 
• In-situ monitoring of chemical reactions for energy storage or catalytic systems 
• Characterization of nano-sized or -structured materials
• Thin film – structure and compositional analysis
• Texture analysis 
• Crystal structure solution
   
• Back-reflection Laue
Back-reflection Laue

Back-reflection Laue is used for quantifying the crystallographic orientation of single crystals. The purpose of such a measurement ranges from:

• Aligning a sample in a particular crystallographic orientation in order to maximize a desired property.
• Preparing a sample for cutting along a specific crystallographic plane.
• Quantifying the angle of misalignment between large grains to other situations where knowing the precise crystallographic orientation is needed. 

Unlike typical X-ray diffraction, instead of a monochromatic beam, Laue diffraction uses Bremsstrahlung radiation. As a result, diffraction spots are observed from a large number of crystallographic planes without needing to move the source or the detector as X-rays of various wavelengths satisfy Bragg’s Law for numerous planes simultaneously. 


Technical Specifications of Back-Reflection Laue
Equipment:  MWL120 Real-Time Back-Reflection Laue Camera 
X-ray source: standard-focus tungsten X-ray tube
Power: Up to 40kV and 30mA
Crystal systems: Cubic, hexagonal, trigonal, tetragonal, orthorhombic, monoclinic and triclinic
Orientation accuracy: 0.25° in regular mode, 0.05° in high resolution mode
Sample size: From a few millimeters to 25+ pounds
Minimum spot size: <1mm

 



Laue back reflection illustrating crystal orientation.  

The team identifies complex unknown organic chemicals, elucidates molecular structure and chemical interactions.

• HP Liquid Chromatography - Electro spray Time of Flight Mass Spectrometry
HP Liquid Chromatography - Electro spray Time of Flight Mass Spectrometry

Quadropole Time of Flight Mass Spectrometry (Q-ToF MS) is, in most cases, a liquid chromatography-based soft ionization mass spectrometry technique that can determine the accurate mass of nearly any molecule containing at least one heteroatom and having a mass between 100-2000 Daltons. The chemical requirement is that a stable or metastable ion can be produced by a molecule donating or accepting a proton to produce a charged species. Most traditional Time of Flight mass spectrometers can determine the accurate mass based on a charged species flight time between a pulsed start position and detection by a multi-channel plate detector.

The additional benefit of the Quadropole ToF MS system is that this instrument can isolate ionizable species in the Quadropole region that is upstream of the ToF Detector. Species that are isolated in the Quadropole then can be manipulated in several ways. The most common Q-ToF analysis is Collision Assisted Dissociation (CAD), most commonly known as MS-MS fragmentation analysis. This technique isolates parent compounds in the Quadropole where a collision gas is introduced, thus resulting in fragmentation of the parent molecule.  The resulting fragmentation spectrum can then be searched in the database for possible identification matches or manually interpreted to obtain molecular formulae and structure of an unknown species.

Analyses Specific to Q-ToF MS
Proteomics Applications – Protein Identification based on Database Search of Peptide Fragments
Metabolomics Applications – Metabolite ID based on group modification to a parent compound
E & L Testing – Identification of Extractable and /or Leachable compounds originating from pastics used in bioprocessing applications
Small Molecule Quantitative Analysis – Low Level Soluble Impurities
Structural and Compositional Analysis of Organic Compounds
 

Types of Ionization

• Electro Spray Ionization (ESI)
• Nano Spray Ionization (NSI)
• Atmospheric Pressure Chemical Ionization (APCI)
• Direct Acquisition in Real Time Ionization (DART)

 

Strengths	Limitations
Ability to analyze large molecules High resolution provides accurate mass  MS-MS fragmentation helps identify unknown species Large dynamic mass range: 50-2000 Daltons Sensitivity down to ppb levels Analyzes water soluble and organic soluble species High sensitivity to salt species	Cannot ionize hydrocarbons Limited sensitivity at low mass: <100 Daltons Only sees ionizable species Positive ions and negative ions must be analyzed separately

 

• Nuclear Magnetic Resonance
Nuclear Magnetic Resonance

Nuclear Magnetic Resonance (NMR) is a spectroscopic technique to observe local magnetic field around atomic nuclei. The NMR signal is generated by exciting the nuclei in a magnetic field with radio frequency pulses into nuclear magnetic resonances, which are detected with sensitive radio frequency receivers.  The local magnetic field around an atom changes the resonance frequency of its nucleus, thus giving access to details of the electronic structure of atoms, functional groups and molecules.  

NMR experiments can be performed on any NMR active nuclei—nuclei with a spin number not equal to 0, but the most common types are 1H, 13C, 15N, 19F, 31P and 29Si etc. Samples can be small or large molecules, bio-molecules, inorganic materials or complex mixtures, with experiments done in either solution or solid state.

Modern NMR techniques made it possible to detect neighboring nuclei (either through covalent bonds or space) using correlation spectroscopy techniques that allow fast and unambiguous structural elucidation. Molecular dynamics such as diffusion, relaxation or molecular binding can be probed using arrayed experiments.  Composition of mixtures can be obtained using quantitative NMR analyses.

In the early 60’s, GE Global Research set up one of the first industrial NMR Labs in the US under the leadership of Liz Williams. Over the past decades, the NMR lab obtained experience with remarkable depth and breadth in the areas of polymer analysis, small molecule structure elucidation and composite and ceramic materials characterization in solving a wide variety of problem for almost every GE business.  

How is NMR used?  

• Small molecule structure elucidation
• Polymer structure, composition, end group analysis, additives, copolymer architecture
• Unknown mixture analysis
• Inorganic composites and ceramics
• Diffusion ordered spectroscopy (DOSY)
• Multiple nuclear approach

 

Strength	Limitations	Instrumentation
Structure and bulk composition Mixture analysis Dynamics information	NMR active nuclei Lower sensitivity Bulk properties (very limited surface information)	600 MHz Varian NMRS solution state: with 5mm indirect, 5mm 19F, 5mm and 10mm broadband, 10mm high 13C sensitivity and 10mm Si-back group free probes 500 MHz Avance III solution state: with 5mm and 10mm broadband probes 300 MHz Avance I solid state; with 2.5mm, 4mm and 7mm MAS probes

 



2D NMR are routinely used for complex molecular structure elucidation.  Shown above are Heteronuclear Single Quantum Correlation (HSQC) and Heteronuclear Multiple Bond Correlation (HMBC) of an imaging agent.



DOSY NMR are routinely used for probing molecular dynamics, such as diffusion and binding of both small and large molecules.

• IR Spectroscopy
IR Spectroscopy

Infrared Spectroscopy (IR) is an analytical technique based on the absorption of IR light which probes the chemical bonds of materials at characteristic frequencies. The IR spectrum of a material can often be used as a chemical fingerprint based on type and relative amounts of chemical bonds present.  This chemical fingerprint can be used to identify an unknown species by comparison to large spectral databases of standard materials, map a phase across a heterogeneous sample, or track changes in chemical bonding due to reaction or degradation.

At GE Global Research, we commonly use IR as a rapid screening tool to identify an unknown contaminant and direct further analysis.  Used in combination with XRF, we can rapidly identify both the organic, inorganic and metallic components of an unknown sample and attempt to trace its source.  Our IR microscope can even obtain high quality spectra from a single fiber or particle when used in conjunction with a diamond transmission cell, therefore sample size is rarely an issue.

How is IR Spectroscopy used?

• Analyze composition of solids, liquids or gasses
• Identification of unknown materials
• Track chemical changes due to reaction or degradation
• Determine kinetics for a chemical reaction
• Monitor differences in crystallinity or molecular order
• Rapid screening tool to direct more in-depth analyses

 

Technical Specifications of IR Spectrometer/Microscope
Equipment:  Bruker Vertex 70 benchtop spectrometer and Hyperion 3000 IR microscope
Signal Detected: Absorption or reflection of IR light
Spectral Range: 5000-500 cm-1; 2000-20000 nm; 2-20 μm
Lateral Resolution: ~20 μm
Detection Limits: Typically 0.1-1% by volume
In situ capabilities:  -196 C to 600 C; atmospheric control; programmed ramp rates and temperature profiles

 

Strengths	Challenges
Rapid identification of organic and some inorganic materials Fast acquisitions (typically <5 min) Non-destructive Requires small amount of material (often less a microgram)	•    Complex mixtures of materials can be difficult to interpret •    Insensitive to metals and some metal oxides •    Bulk characterization technique, often limited to components down to ~1 by volume •    Strong absorption by water limits usefulness for aqueous solutions



A small particle caught in the fuel filter of a jet engine was isolated, analyzed by IR spectroscopy and identified as a copolymer of vinylacetate/ethylene filled with an aluminosilicate.

• Raman Spectroscopy
Raman Spectroscopy

Raman Spectroscopy is an analytical technique which probes the movement of atoms or molecules at characteristic frequencies in response to excitation with a laser beam. Raman spectroscopy gives information about chemical bonding, phase and molecular orientation.  At GE, this technique is widely used to map phase composition in ceramic coatings and composites.

Our confocal Raman microscope can also be used for collecting fluorescence or photoluminescence (PL) spectra in the visible and near-IR (300-900nm).  PL mapping can be used to track changes in composition or stress state across a semiconductor or other emissive material.  The high spatial resolution provided by the confocal microscope allows the properties grains and grain boundaries to be interrogated with sub-micrometer resolution.

Raman is also commonly used to interrogate the structure of carbon (graphite, graphene, amorphous carbon, carbon nanotubes, diamond and diamond-like carbon coatings) due to its high sensitivity and specificity to differences in carbon-carbon bonding.

How is Raman Spectroscopy used?

• Map phase composition with sub-micrometer resolution
• Track chemical changes due to reaction or degradation
• Determine kinetics for a chemical reaction
• Map differences in crystallinity or molecular order
• Detailed structural analysis of carbon

 

Technical Specifications of Confocal Raman Microscope
Equipment:  Horiba LabRam Aramis
Signal Detected: Scattered light from laser excitation
Excitation Lasers:  532, 633 or 785 nm
Lateral Resolution: <1 μm
Detection Limits: Typically 0.1-1% by volume
In situ capabilities:  -196 C to 600 C; atmospheric control; programmed ramp rates and temperature profiles

 

Strengths	Challenges
<1 um spatial resolution Fast acquisitions (<1 sec to 10 min) Minimal sample prep Insensitive to water Non-contact, non-destructive	Fluorescence can swamp out Raman signal Usually bulk technique (sensitivity ~1% by volume) Damaging the sample with laser

 



Confocal Raman microscopy can be used to map phase composition in ceramic materials such as Yttria-stabilized zirconia (YSZ) with <1 μm spatial resolution.



Photoluminescence (PL) mapping of a polycrystalline semiconductor film shows defective (dark colored) material near grain boundaries

• GC x GC Time of Flight Mass Spectrometry
GC x GC Time of Flight Mass Spectrometry
Electron Impact (EI) Time of Flight Mass Spectrometry (ToF MS) is a gas phase ionization mass spectrometry technique that is usually associated with Gas Chromatography (GC) applications. A typical analysis uses EI to fragment species in the gas phase giving rise to a distinct fragmentation spectrum that is very often unique to, and diagnostic of, different chemical classes and individual compounds. Since the EI process produces fragmentation spectra that are usually very consistent from sample to sample regardless of what instrument is used, it has become an essential tool in chemical characterization of volatile and semi-volatile organic compounds.
The use of EI has a long history in the field of chemical analysis. Because of this, coupled with the robust reproducibility of EI spectra, there exists a vast resource of database information where fragmentation spectra can be searched against existing database entries to obtain positive identification of unknown compounds.
EI ToF MS when coupled to 2-Dimensional Gas Chromatography (2D GC x GC) provides a powerful analytical tool that can add increased resolution and characterization capability compared to traditional Gas Chromatography.  The difference between typical GC and the 2-Dimensional system is traditional GC analyses separate gas phase species as a function of vapor pressure or boiling point in a 1-dimensional analysis.  The 2-dimensional system separates each species eluting on the first column (1st dimension), then separates based on polarity on the second column (2nd dimension). The increase chromatographic resolution allows for cleaner fragmentation spectra to be obtained thus resulting in less overlap of coeluting species.
Typical Applications for 2D GC ToF MS
• Fuel Analysis – Biodiesel, Jet Fuels, Light Crude
• Analysis of Oxidation Products – Oils, Fuels, Gases, Light Crude, Organic Mixtures
• Evolved Gases from Chemical Processes – Composites, Curing Processes, Exposure Risks
• Compositional Analysis of Complex Organic Mixtures
• Derivatization for Metabolomics Application 
• Targeted Semi-Quantitative Analysis
 
Available Sample Introduction Techniques
• Direct Liquid Injection
• Static Headspace Analysis – (Ambient – 200C)
• Thermal Desorption – (Ambient – 350C)
• On-Column 

The team quantifies the elemental & ionic composition in diverse matrices, from bulk to part per billion trace impurity with high accuracy.

• Inductively Coupled Plasma
Inductively Coupled Plasma

Inductively coupled plasma optical emission spectrometry (ICP-OES) and ICP mass spectrometry (ICP-MS) are analytical techniques used for the determination of elemental composition. When a sample is introduced into the instrument, the plasma causes the emission of light or the generation of ions that are characteristic to each element. The concentration of an element within a material can be quantitatively calculated by detecting the wavelengths of light (OES) or ions (MS) associated with the element and comparing the signal to that of known reference materials (standards).

Nearly all types of solids and liquids can be evaluated by ICP for element concentrations from trace-level (sub part-per-trillion, ppt) to the major components (high weight percent, g/g x 100). Most materials require some degree of preparation before they can be analyzed. Solids are converted into liquid form, usually by dissolution with mineral acids, and liquids are often treated with mineral acids to decompose organic components and to stabilize the elements in solution. GE Global Research has experience in many types of sample preparation procedures including hot block and microwave digestion, dry ashing, wet ashing (sulfuric char), and fusion.

When a laser is interfaced with an ICP, the technique is call Laser Ablation ICP (LA-ICP). This is most often done with an ICP-MS (called LA-ICP-MS) but can also be conducted with ICP-OES (LA-ICP-OES). The laser is used to selectively remove a small quantity of material from a solid sample for direct introduction into the ICP. In this way, the solid test material does not need to be dissolved or digested into a liquid prior to analysis. The laser can be used to sample specific locations on a part, such as a defect, or it can be used to scan across the sample to create an elemental distribution map.

How is ICP Used?

• Quantification of up to 74 elements in solids and liquids from trace-level concentrations to the major constituents
• Sample types include: alloy, ceramic, biological, glass, soil, water, oil, fuel, polymer, composite
• Bulk compositional analysis is conducted using traditional solution introduction system
• Elemental distribution and depth-profiling is conducted with Laser Ablation introduction system

 

ICP and Related Instrumentation in Material Characterization Lab
ICP-OES: Spectro Arcos SOP
ICP-MS (quandrupole): Perkin Elmer Elan 6000 and Perkin Elmer Elan DRC II
ICP-MS (high mass resolution): Thermo Scientific Element 2
CETAC LSX-213 213 nm Laser Ablation System
CEM Mars 5 Microwave Digestion System
Milestone UltraWAVE Microwave Digestion System

 

Strengths

Limitations

Bulk analysis technique that can determine up to 74 elements in a single sample analysis Quantitative  Low detection limits (ppt, ppb range for most elements) Several orders of magnitude linear dynamic range Ability to reprocess ICP data post analysis for optimal wavelength choice to minimize spectral influence increasing accuracy and detection limits Customized sample preparation with optimized instrument settings can provide very high precision and accuracy measurements

The sample to be analyzed by ICP-OES or ICP-MS typically must be in solution form. This requires digestion or dissolution in mineral acids in most cases.  Well controlled sample preparation and instrument calibration is critical for long term accuracy and precision. The analysis of samples with a complex matrix can be challenging due to spectral and matrix interferences.

 



Elemental map of trace levels of elements in a tissue sample.

• Ion Chromatography
Ion Chromatography

Ion chromatography (IC) is a specialized subset of liquid chromatography (LC) which is geared towards the quantification of anions and cations. The method separates the ions of interests in time through competitive interaction of the analyte ions and ions from the mobile phase with ion exchange sites on the stationary phase. Selectivity is based on many factors including the ion exchange site on the stationary phase and the charge, size and hydrophobicity of the ion.

Once separated, detection of the ions can be carried out by several means including conductivity, UV/VIS, or mass spectrometry.  Conductivity is most common because it is highly sensitivity to ions in solution and is easy to maintain and calibrate. However, conductivity is nonspecific, and to achieve the highest sensitivity, the ions from the mobile phase need to be removed to reduce background conductivity. This is typically accomplished by either chemical or electrolytic suppression devices. 

As with all LC techniques IC requires a sample to be in solution to be analyzed.  There are a variety of ways to accomplish this depending on the sample matrix and the analytes of interest.  Once the analytes are in solution, sample matrix spikes are made and retention times for each analyte are determined for the specific separation method being employed. Once retention times are identified a series of known ion standards are run and used to create a calibration curve. Response of the analyte in the sample is compared to the calibration curve and concentrations are calculated.

How is IC is used?

• Quantification of the anion and cation content of samples
• As a compliment of ICP providing quantification for halogens
• When the form of the element matters (e.g. sulfate vs sulfide, nitrate vs nitrite)

 

Strengths	Limitations
High sensitivity with detection limits in the ppb range Typically little sample preparation required for aqueous samples Can analyze many organic acids and inorganic anions in the same sample A good method for quantification of amines	Not good for unknown identification  High organic or metals content in samples requires additional preparation Solid samples require more extensive preparation methods Conductivity detection isn’t specific so interfaces can be problematic

Capabilities
We have capability to run both anion and cation methods on various Dionex/Thermo Fisher equipment, and are typically setup for inorganic anion/organic acid as well as alkaline/alkaline earth analysis. Our systems can be adapted to run most methods that require conductivity and/or UV-VIS detection. In addition, we have the ability to perform various sample preparation methods including Parr Oxygen Combustion bombs for organic materials and solid and liquid phase extractions/sample preparations.



A chromatogram from ion chromatography used for the quantification of low levels of F, Cl, Br and SO4 in a detergent matrix. 

• X-ray Fluorescence
X-ray Fluorescence

X-ray Fluorescence Spectroscopy (XRF) is the holistic name for a host of different instruments or methods that can provide the identity of elements present in and elemental composition of materials. The information is generated when X-Rays hit the sample and core shell electrons are ejected. These electrons leave holes, vacancies are filled with outer shell electrons, and the leftover energy is often emitted as X-rays. The energy of these emitted X-rays tells you what elements are present and the number of X-rays of a given energy are related to the concentrations of the element.

There are two main types of XRF instruments: Energy Dispersive (EDS) and Wavelength Dispersive (WDS).  Energy Dispersive instruments use a semiconductor detector to both discriminate the energy of and count the X-rays emitted by the sample. Wavelength dispersive instruments discriminate the energy of X-rays based on diffraction of the fluoresced X-rays by single crystals and counts them with flow/proportional counters and scintillator based detectors. The energy dispersive method generally provides fast analysis because it can analyze all the X-rays produced by the sample at once; however, this is at the expense of spectral resolution and the total count rates that can be achieved. Wavelength dispersive instruments scan through the relevant diffraction conditions so they are generally slower but provided the best spectral resolution and allow for higher count rates. Energy dispersive instruments are best when speed and/or simplicity are important and the samples do not have complex elemental profiles. Wavelength dispersive instrument are great for samples with highly complex elemental make ups and when the latest detection limits are necessary. 

How is XRF is used?

• Bulk elemental composition
• Spatially resolved elemental composition
• Alloy/Material identification
• Screening for/quantification of impurities in materials

 

Strengths

Limitations

Covers much of the periodic table Measures concentrations from ppm to 100% Can analyze conductive and nonconductive samples Direct analysis for many solid and liquid samples with minimal sample preparation Standardless semi-quantitative analysis High precision quantification with matrix matched standards Can analyze samples in vacuum or in air Micro analysis down to 25m and elemental mapping Can be non-destructive Can be very rapid (seconds to minutes)

Requires matrix matched standards for best quantification Some samples need more time-consuming preparation for best analysis Surface topography/particle size can impact results Detection limits tend to be 10s to 100s of ppm so they aren’t as sensitive as ICP For Light elements (B-F) detection limit/precision is poor

 

Capabilities
We have three main XRF instruments at GE Global Research Bruker S8 Tiger WDXRF, Bruker M4 Tornado micro XRF and four different Thermo Niton Handheld XRFs. In addition, we routinely perform typical XRF sample preparation methods including pressed powder, fusion, liquid cell, loose powder and polished pieces. By combining these instruments and sample preparation methods we can analyze almost any material from much of the periodic table. 
 

 

Capabilities
We have three main XRF instruments at GE Global Research Bruker S8 Tiger WDXRF, Bruker M4 Tornado micro XRF and four different Thermo Niton Handheld XRFs. In addition, we routinely perform typical XRF sample preparation methods including pressed powder, fusion, liquid cell, loose powder and polished pieces. By combining these instruments and sample preparation methods we can analyze almost any material from much of the periodic table. 
 



uXRF image of Cu, Sn, and multielement overlay maps along with a visual image of a circuit board are shown.  

• Instrumental Gas Analysis
Instrumental Gas Analysis
Instrumental Gas Analysis (IGA) measures carbon (C), sulfur (S), oxygen (O), nitrogen (N) and hydrogen (H) present in metals, ceramics and other inorganic materials. It is a bulk technique that utilizes combustion, infrared absorption, and thermal conductivity detectors to determine the C, S, O, N, and H composition.
C and S in a solid sample are measured by combustion analysis and detected by non-dispersive infrared (NDIR) detectors.  When a pre-weighed sample is placed in ceramic crucibles it is oxidized to CO2 and SO2, respectively.  . The C and S concentrations of an unknown samples is determined relative to calibration standards.
Oxygen, nitrogen, and hydrogen are measured by inert gas fusion analysis, where a pre-weighed sample is placed in a graphite crucible, and is heated in an impulse furnace to release analyte gases. Oxygen present in the sample reacts with the graphite crucible to form CO and CO2, which are detected using non-dispersive infrared (NDIR) cells. The gas then flows through a heated reagent, where the CO is oxidized to form CO2, and H2 is oxidized to form H2O. H2O and CO2 are measured again by another set of NDIR cells which detect H and O contents in the sample. These analytes are then scrubbed out of the carrier gas stream. The final component in the flow stream is nitrogen and then detected by a thermal conductivity (TC) detector. The O, N, and H concentrations of unknown samples are determined relative to calibration standards.
How is IGA used?
C, S, O, N and H determination in solids, powders or particulate inorganic materials, such as SiC, titanium, nickel, cobalt alloys, irons, steels, ceramics, ores, metals, etc. 
Technical Specifications of IGA
Instruments	LECO CS 844	LECO ONH 836
Elements Analyzed Carrier gas Detector Instrument range (mg) Precision Sample size(mg)	Carbon,  Sulfur O2 NDIR 0.0006 to 60 0.0003 or 0.5% RSD 10-1000	Oxygen, Nitrogen,  Hydrogen He NDIR and TC 0.00005 to 50 0.000025mg or 0.3%RSD 10-1000
Strengths
• Accurate determination of C, S, O, N, H in solids, powders, or particulates materials
• Large linear range of quantification (ppm to wt%)
• Quick and easy with autoloaders
• High throughput
Limitations
• A few mg to 1 grams of samples needed depending on the concentration in the samples
• Destructive technique

The team studies phase transformation and mechanical property changes both in situ and ex-situ.

• TGA-MS Gas Evolution Analysis
TGA-MS Gas Evolution Analysis

TGA-MS Gas Evolution Analysis

A thermogravimetric analyzer equipped with a mass spectrometer (TGA-MS) continuously measures mass while a sample is heated over time. Mass, temperature and time in thermogravimetric analysis are considered base measurements while many additional measures may be derived from these three base measurements.

A typical thermogravimetric analyzer contains a heating furnace along with a precision balance.  The sample and sample pan are located inside a furnace. The temperature is generally increased at a constant and programmable rate. Since thermal degradation and weight loss changes may differ depending on the atmosphere used, various gas environments can be selected such as air, nitrogen, argon and heliumto best replicate the experimental conditions needed.

Thermogravimetric analysis combined with quadropole mass spectrometric detection is a useful tool in three key ways:

• Analyzing evolved gas species created from a thermal process
• Understanding chemical reactions involved in high temperature curing
• Determination of the removal of organics as a function of thermal treatment


Instrument: Netzsch STA 409 CD-QMS 403/5 SKIMMER
The Netzsch SKIMMER coupling system with a quadrupole mass spectrometer (QMS) is a powerful addition to traditional Thermogravimetric analysis (TGA).  The specific benefit of using the Netzsch STA 409 Skimmer system is that the mass spectrometer skimmer is positioned directly above the TGA outflow, thus minimizing the potential for cold zones and loss of analytes.  Our TGA system coupled with the QMS mass spectrometer has proven to be useful characterization tool for organic as well as inorganic characterization of thermal processes.

Capabilities and Parameters
Temperature Range: Silicon Carbide Furnace: Ambient to 1450C / Alumina Orifice
Temperature Range: Graphite Furnace: Ambient to 2000C / Glassy Carbon Orifice
Ramp Range: 0.001 to 100C / Minute
Sample Weight Range: 5 to 15000mg
Mass Range for QMS: 1 to 512 mass units
Mass Resolution: 0.5 mass units
Gas Environment Options: Argon, Nitrogen, Helium or Air

 

Strengths	Limitations
Measures evolved gases directly from thermal losses High sensitivity mass spectrometer detection - 0.2mg organics Can obtain mass spectra throughout entire heating ramp up to 1450C Can provide quantitative results for simple weight loss profiles	Complex evolved gas mixtures will give rise to overlaps in mass spectra Cannot obtain accurate mass data (0.5-unit resolution) High amounts of volatiles can overwhelm mass spectrometer High amounts of water can cause interferences

 

• Thermal Gravimetric Analysis
Thermal Gravimetric Analysis

Thermogravimetric analysis (TGA) is a technique in which the mass of a substance is measured as a function of temperature or time while the substance is subjected to a controlled-temperature program in a specified atmosphere. Common usage includes investigation, selection, comparison and end-use performance evaluation of materials in research and production applications.

A typical thermogravimetric analyzer contains heating furnace along with a precision balance.  The sample and sample pan are located inside a furnace. The temperature is generally increased at a constant and programmable rate. Since thermal degradation and weight loss changes may differ depending on the atmosphere used, various gas environments can be selected such as air, nitrogen, argon, helium, CO2, and etc., to best replicate the experimental conditions needed.

How is TGA Used?
The sample can be powder, bulk sample, and liquid. Common applications include but not limited to: 

• Decomposition kinetics
• Oxidative and thermal stability
• Reaction relating to mass changes 
• Residue/Filler content in polymer matrix
• Moisture and volatiles contents

 

Strengths	Limitations	Instruments
Small sample size Temperature range RT to 1600°C  TGA resolution: 0.01 to 0. 1µg Multi-component mass loss events	Evolved products are not identifiable Destructive	TA Instruments Q5000 Netzsch STA F5 Netzsch STA F3 Netzsch STA 449 C Mettler Toledo TGA/DSC

• Micro-indentation Hardness Testing
Micro-indentation Hardness Testing
Microindentation hardness testing measures the hardness of a material by imparting a microscopeindent into the material. One can calculate the hardness by measuring the size or surface area of the indent and the load applied. There are two basic types of microindentation hardness testing that we use: Vickers and Knoop. The Vickers and Knoop hardness test uses a diamond indenter of a specific shape with a dead load directly over the indenter which is slowing placed on the surface of the sample and held there for about 20-30 seconds. The Vickers indenter is a square based pyramid with an angle of 136° between faces while the Knoop indenter is a rhombic based pyramid that generates a diagonal ratio of about 7 to 1. The advantage of the Knoop method is that it creates an indent.
Samples must be polished or at least very flat to achieve a high-fidelity impression.  Once finished, the indent diagonals are measured and plugged into a formula which generates a Vickers or Knoop hardness. Any hardness testing pattern that can be programmed by the scanning stage so that fully automated testing can be achieved.
Microindentation Hardness Equipment
Microindentation Hardness Equipment
• Automated Clemex CMT hardness tester
• Programmable 60mm x 200mm scanning stage with autofocus
• Four objectives: 5x, 10x, 20x, 40x
• Load range: 1-2000gms
• Vickers and Knoop
   
• Nano Indenting
Nano Indenting

Nanoindentation works by pressing a nanoindentor probe into the surface of a material and measuring the applied load and probe displacement.  The resulting load and displacement curve can be used to calculate quantitative mechanical properties of the material at the nanoscale. A fundamental feature of nanoindentation is that mechanical properties can be determined without having to measure the size and depth of the resulting nanoindent. Nanoindentation utilizes an optical microscope to precisely position the nanoprobe. Additionally, the nanoprobe can be scanned across the surface of the sample giving a scanning probe image with greater resolution. The most common mechanical properties that are measured are hardness and elastic modulus. Other properties that can be determined depending on the sample include creep, stress relaxation, interfacial adhesion and fracture toughness.

Instrumentation

• Hysitron TI950 Triboindentor
• Features include:
  • Low load transducer – max load 10uN, max displacement 5um
  • High load transducer – max load 10N, max displacement 80um
  • Optical imaging
  • Scanning probe imaging
  • Motorized stage for automated testing
  • Heating stage for high temperature testing (Up To 800C)