Surface Analytical Techniques for Analysis of Coatings · Surface Analytical Techniques for...
Transcript of Surface Analytical Techniques for Analysis of Coatings · Surface Analytical Techniques for...
Surface Analytical Techniques for Analysis of Coatings
Mary Jane Walzak, Mark Biesinger and Brad Kobe The University of Western Ontario
Surface Science Western
ISO 9001:2008 Registered
Why do Surface Analysis?
Provide timely economical solutions to common manufacturing issues
• Contamination of raw materials• New product development• Understanding corrosion issues• Adhesion failures• Fracture and wear• Cosmetic staining• Surface modifications
• Quality assurance program• Reverse engineering• Reduce down time• Minimize scrap• Diagnose field returns
Common Analytical Techniques
• Optical Microscopy • Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy
(SEM/EDX)• Fourier Transform Infrared Spectroscopy (FTIR)• Laser Raman Spectroscopy• X-ray Photoelectron Spectroscopy (XPS)• Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS)• Dynamic Secondary Ion Mass Spectrometry (SIMS)• Scanning Auger Microscopy/Auger Electron Spectroscopy (SAM/AES)• Atomic Force Microscopy (AFM)• Surface Profilometry
Common Analytical Techniques
SEM/EDX• Vacuum technique• High resolution imaging with nanometer resolution• Elemental information from carbon to uranium• Analysis volumes on the order of 1 micron
FTIR and Raman spectroscopy• Optical microscope techniques• Vibrational techniques (functional groups)• Organic and inorganic species• Analysis of micron sized features
Comparison of hydrocarbon speciesfrom reference material (red)
and paint defect (blue)
SEM image of Ag coating
Common Analytical Techniques
X-ray photoelectron spectroscopy (XPS)• Vacuum technique• Elemental and chemical state information• Very surface sensitive (10 nm probing depth)• Sensitivity: 0.5 atomic %
Time of flight secondary ion mass spectroscopy (ToF-SIMS)• Vacuum technique• Mass spectral technique (up to 10,000 amu)• Analysis of outer most monolayers• Sensitivity is ppm to ppb
XPS scan of electrochemicallygrown coating
ToF-SIMS images of chromedefect on stainless steel
Case 1: Pinhole defects in chrome coatings
Analytical approach• Identification of defects using optical microscopy• Initially examined several defects using SEM/EDX
• No obvious contamination detected• Decided to use a surface more surface sensitive
technique (ToF-SIMS)
Problem• A manufacturer suddenly experienced pinhole defects in vacuum deposited
chrome coatings on polymer substrates
Optical image of pinhole
Case 1: Pinhole defects in chrome coatings
SEM image of pinhole defectResults• SEM imaging showed that the chrome
coating was very thin and feathered-out at the edges of the pinholes
• No obvious particles or surface debris was responsible for the defects
• ToF-SIMS is a very sensitive technique • Nitrate species detected: NO2¯and NO3¯• No ammonia, salt or silicone detected
• Nitrate contaminant prevented deposition of the chromium
ToF-SIMS images of pinhole defect
NO2¯ Cr
Case 2: Contamination of extruded material
Analytical approach• Prepared metallographic cross-sections for SEM/EDX• Thin cross-sections analyzed by FTIR in transmitted
light mode using the diamond compression cell• Raman spectroscopy also provided chemical
information about the defects
Problem• A company was experiencing black defects embedded in a clear extruded
polycarbonate part
Optical image of defect
Case 2: Contamination of extruded material
Results• Backscattered electron (BSE) images of the
defects showed a layered structure• Elemental X-ray intensity maps of defect
• Sodium, magnesium, oxygen and silicon• FTIR showed peaks consistent with talc• Polymer portion of the defect appeared to be
degraded polycarbonate (FTIR)• Raman analysis showed the presence of
amorphous carbon in the defect area
SEM Na
O
MgC
Si
BSE image and EDX maps
Case 3: Reverse engineering of packaging
Problem
Analytical approach
• A food packaging manufacturer was interested in reverse engineering a coffee container
• The total thickness of the sample container was approximately 400 microns
• Cross-sections were prepared for SEM/EDX analysis to determine the variation in the elemental composition of the layers
• Thin cross-sections were prepared for examination by optical microscopy, FTIR and Raman analyses
200 µm
Case 3: Reverse engineering of packaging
Results• Optical and BSE images showed the presence
of a layered structure with a number of thin layers at the ID
• EDX mapping showed variations in the carbon, oxygen and titanium in the various layers
• FTIR and Raman identified nine distinct layers in the material
BSE image and EDX overlay
Case 3: Reverse engineering of packaging
Results
HIGH IMPACT POLYSTYRENE
ETHYLENE VINYL ACETATE COPOLYMER
POLY(VINYL ALCOHOL-CO-ETHYLENE)
POLYETHYLENE
10 µm
POLYSTYRENE with TiO2
100 µm
POLYSTYRENE with TiO2
POLYSTYRENE
POLYSTYRENE with TiO2
POLYSTYRENE
POLYETHYLENE (Textured Surface)
Case 4: Adhesion failure of body side molding
Analytical approach• The foam adhesive was first examined using XPS• Next, the painted side panels exhibiting full failure, interment failure and
good reference panels were analyzed by XPS
Problem• During application at an assembly facility it was noted that intermittent
failures of the adhesive on body side moldings was occurring
Case 4: Adhesion failure of body side molding
Results• XPS analysis of the foam adhesive surfaces
did not reveal any significant contamination• XPS analysis showed significant changes in
the silicon levels on the painted side panel• High resolution silicon 2p spectra showed the
silicon to be present as silicone• After testing is was revealed that the excess
silicone was due to a mixing problem in one of the clearcoat totes
XPS survey spectra of clear coat
Case 5: Raman spectroscopy of pigment
Analytical approach• The defects were identified using a stereo microscope
and thin slices were prepared using a scalpel• The sections were examined using SEM/EDX and laser
Raman spectroscopy
Problem• A company was experiencing dark defects in their basecoat and wanted to
know if the formulation was correct
Case 5: Raman spectroscopy of pigment
Results• EDX spectroscopy detected high levels of carbon,
oxygen, nitrogen and iron in the defect• Laser Raman spectroscopy was then performed• The spectrum of the blue defect material
matched that of ferric ferrocyanide, a common blue pigment
• Ferric ferrocyanide was NOT the specified blue pigment for use in this basecoat
• This was an issue with the pigment supplier
Ferric Ferrocyanide
Defect Material
Raman spectra of defect material and reference blue pigment
Case 6: Analysis of crater defects
Analytical approach• Initially assess the crater defects optically• If no obvious residue or contaminant is visible
• typically examine crater using either XPS or ToF-SIMS• If large contaminants are visible
• Use SEM/EDX combined with FTIR spectroscopy • most likely cross-sectioning would be required
Problem• Many automotive companies experience paint crater defects on car panels
Cast 6: Analysis of crater defect
Results• ToF-SIMS imaging showed fluorine associated
with the particle• Silicone was detected at the center of the
crater and a hydrocarbon species was observed at the edges of the crater
• The particle is consistent with Teflon®• The silicone and hydrocarbon species are
possibly from oils and lubricants
ToF-SIMS images of crater defect
Case 7: Cosmetic corrosion of aluminum
Analytical approach• Initially, these samples were examined by SEM with
elemental X-ray mapping• XPS imaging was then used with spot analyses to
check specific corroded regions
Problem• Cosmetic corrosion study of zinc galvannealed aluminum test panels that
were strapped on vehicles and driven around various cities for two years
Case 7: Cosmetic corrosion of aluminum
Results• SEM/EDX analysis revealed the presence of
sulphur and other salts • What form is this sulphur? Need to know to
change testing procedure• XPS imaging with spot analyses was used to
check the form of the sulphur present
BSE image and elemental X-ray maps
Case 7: Cosmetic corrosion of aluminum
Results• S (2p) high resolution spectra collected from
a 220 micron spot• Sulphur 2p peak found at 169.3 eV indicative
of sulphate• Results were used to improve normal
corrosion tests that use salt sprays or salt baths (containing sodium and chlorine)
NameSulphate
Pos.169.27
FWHM2.19
%Area100.0
S 2p
210
220
230
240
250
260
172 170 168 166 164 162Binding Energy (eV)
Zn
Summary of Surface Analysis Techniques
• Common analytical techniques include:
• These techniques can be used to solve manufacturing issues from many sectors including aerospace, automotive, medical and semiconductor
• Fast and accurate methods to diagnose coating and material issues• Contamination• Corrosion issues• Adhesion failures
• Failure analysis• Reduce scrap• Diagnose field returns
SEM/EDX FTIR Raman XPS ToF-SIMS
ISO 9001:2008 Registered