Iezzi webinar

Overview of forensic engineers' analytical techniques for attorney use.

1. HELPFUL INFORMATION FOR ATTORNEYS WHEN WORKING WITH FORENSIC ENGINEERS© Dr. Robert Iezzi Docs > Iezzi Webinar.pptx
2. 2 OUTLINE  What Do Forensic Engineers Do ?  Types of Analytical Tools Commonly Used  Case Studies  Summary
3. 3 WHAT DO FORENSIC ENGINEERS DO ?
4. 4 WHAT DOES A FORENSIC ENGINEER DO ?  Determines reasons why products fail  What went wrong  Why it went wrong  How it went wrong Unbiased, accurate, defendable results
5. 5 ANALYTICAL TOOLS
6. 6 INITIAL SAMPLE OBSERVATION
7. 7 ANALYTICAL TOOLS  Optical Microscopy  Scanning Electron Microscopy  Energy Dispersive X-ray Spectroscopy (EDS)  Metallographic Cross-sections  Confocal Scanning Optical Microscopy  Atomic Force Microscopy (AFM)  X-ray Photoelectron Microscopy (XPS)
8. 8 ANALYTICAL TOOLS  Transmission Electron Microscopy (TEM)  Auger Electron Spectroscopy  Fourier Transform Infrared Spectroscopy (FTIR)  Gas Chromatography Mass Spectrometry (GC-MS)  X-ray diffraction (XRD)  X-ray Radiography
9. 9 OPTICAL MICROSCOPY
10. 10 OPTICAL MICROSCOPY  Optical microscope  Often referred to as light microscope  “As-is” samples - need sample to fit under lens  No surface prep  2-dimensional images  Direct link to camera and TV monitor  Light filters to see different features – polarized light shows crystals in polymers  ~2X to 2,000X magnifications  Resolution ~0.5 micron
11. 11 OPTICAL MICROSCOPY
12. 12 OPTICAL MICROSCOPY How Do I Use Take “as-is” photos of every sample I analyze Document original condition Use polarized light to observe structure of plastics
13. 13 SCANNING ELECTRON MICROSCOPY (SEM)
14. 14 SCANNING ELECTRON MICROSCOPY (SEM)  Produces images of a sample by scanning it with a focused beam of electrons  Electrons interact with atoms in the sample, producing various signals that contain information about the sample's surface features  Resolution better than 1 nanometer - 1 billionth of a meter  Detects the outer few microns of surface
15. 15 SCANNING ELECTRON MICROSCOPY (SEM)  More than 500,000 magnification, about 250 times the magnification limit of the best optical microscope  Samples must fit in the specimen chamber (~6” max)  Samples must be in high vacuum and must be electrically conductive  Non-conductive samples must be coated with ultra-thin conductive coating to prevent surface charging
16. 16 SCANNING ELECTRON MICROSCOPE
17. 17 SCANNING ELECTRON MICROSCOPY (SEM) Smooth metal facets characteristic of brittle fracture
18. 18 SCANNING ELECTRON MICROSCOPE How Do I Use Frequently Very high resolution/quality, high magnification images of “as-is” samples Minimal surface prep – original sample condition preserved Cost effective Very high “Bang for the Buck”
19. 19 ENERGY DISPERSIVE X-RAY SPECTROSCOPY (EDS)
20. 20 ENERGY DISPERSIVE X-RAY SPECTROSCOPY (EDS)  EDS is an analytical capability that can be coupled with SEM to determine elemental composition  The impact of the electron beam on the sample produces x-rays that are characteristic of the elements present on the sample
21. 21 ENERGY DISPERSIVE X-RAY SPECTROSCOPY (EDS)
22. 22 ENERGY DISPERSIVE X-RAY SPECTROSCOPY (EDS) How Do I Use Frequently Get elemental analysis results quickly on specific locations noted on SEM micrograph Cost included in SEM cost
23. 23 METALLOGRAPHIC CROSS– SECTIONS
24. 24 METALLOGRAPHIC CROSS– SECTIONS  Cut a “cross-section” of sample to obtain edge view – analogous to cutting into a steak on the grill to see if its cooked to your liking  “Mount” the cross-section in a plastic material
25. 25 METALLOGRAPHIC CROSS– SECTIONS  Sample then grinded and polished using successively finer abrasive particles to produce a scratch-free mirror finish  Analyze the cross-section in SEM or other methods discussed
26. 26 METALLOGRAPHIC CROSS– SECTIONS
27. 27 METALLOGRAPHIC CROSS– SECTIONS How Do I Use Frequently Particularly to determine why coatings fail or corrosion mechanisms Used with SEM or other tests methods
28. 28 CASE STUDIES USING THESE ANALYTICAL TECHNIQUES
29. 29 CASE #1 CORROSION OF PAINTED ALUMINUM WINDOW & DOOR FRAMES
30. 30 CORROSION OF PAINTED ALUMINUM WINDOW FRAMES
31. 31 CORROSION OF PAINTED ALUMINUM FRAMES
36. 36 CORROSION OF PAINTED ALUMINUM FRAMES Conclusions  Premature corrosion  Not due to aluminum substrate, window manufacturer, or paint company  Was due to poor pretreatment process by company who painted the product  Paint lifted from the pretreatment layer  Poor pretreatment layer likely due to  Use of tap process water, not de-ionized water  Contaminated water  Poor process control
37. 37 CASE #2 CORROSION OF COPPER ROOFING COATED WITH LEAD
38. 38 LEAD-COATED COPPER
42. 42 LEAD-COATED COPPER Conclusion  Premature corrosion caused by porosity and non-uniformity of the lead coating  The porosity exposed the copper substrate, creating an electrochemical corrosion cell which accelerated the corrosion of the lead  Poor LCC manufacturing
43. 43 CASE #3 MANGANESE PHOSPHATE COATING
44. 44 MANGANESE PHOSPHATE
45. 45 MANGANESE PHOSPHATE
46. 46 MANGANESE PHOSPHATE Conclusions  The premature failure of the compressors was due to the alternate MnP coating, which: -was very rough, non-uniform, and porous -wore away the compressor seals at an accelerated rate, causing the compressor to lose pressure and not pump refrigerant
47. 47 CONFOCAL SCANNING OPTICAL MICROSCOPY
48. 48 CONFOCAL SCANNING OPTICAL MICROSCOPY  Recent development in last 20 years  Evaluate “as is” sample - no sample prep or vacuum chamber  Filters out out-of-focus blur from 3- dimensional samples  Permits imaging of 3-dimensional samples or very rough surfaces  Gives quantitative measurements of height, surface profiles, and 3- dimensional image reconstruction
49. 49 CONFOCAL SCANNING OPTICAL MICROSCOPY Partial profile of 1-Euro coin
50. 50 CONFOCAL SCANNING OPTICAL MICROSCOPY How Do I Use Rarely – only when I need extreme detail about the surface features of surface sample Very few test labs have this equipment - relatively new and expensive Long time to process the sample = high cost per sample
51. 51 ATOMIC FORCE MICROSCOPY (AFM)
52. 52 ATOMIC FORCE MICROSCOPY (AFM)  AFM Analysis provides visual images with atomic resolution of surface features  Capable of quantifying surface roughness of samples down to the nanometer scale
53. 53 ATOMIC FORCE MICROSCOPY (AFM)
54. 54 ATOMIC FORCE MICROSCOPY (AFM) How Do I Use When I need extreme detail about the surface features of a flat sample Use confocal scanning optical microscopy if surface is not flat
55. 55 X-RAY PHOTOELECTRON MICROSCOPY (XPS)
56. 56 X-RAY PHOTOELECTRON MICROSCOPY (XPS)
57. 57 X-RAY PHOTOELECTRON MICROSCOPY (XPS) How Do I Use When I need to know the chemical compounds present on the surface (top 0 - 10 nm) of a material – not just chemical elements
58. 58 TRANSMISSION ELECTRON MICROSCOPY (TEM)
59. 59 TRANSMISSION ELECTRON MICROSCOPY (TEM)  Provides an image of a sample by transmitting beam of electrons through an ultra-thin sample  Image resolutions about 0.1 nm are produced  TEM has better spatial resolution/images than SEM or optical microscopy, but requires much more sample preparation
60. 60 TEM
61. 61 TRANSMISSION ELECTRON MICROSCOPY (TEM)  Provides extremely fine detail - even as small as a single column of atoms, which is thousands of times smaller than the smallest resolvable object in a light microscope
62. 62 TRANSMISSION ELECTRON MICROSCOPY (TEM) How Do I Use Rarely use because I usually do not need details down to the atom size TEM more suitable for basic material research at atomic level Sample prep tedious – very thin samples needed to transmit electrons through it Very few labs have TEM High cost per sample Overkill for most of my work
63. 63 AUGER ELECTRON SPECTROSCOPY
64. 64 AUGER ELECTRON SPECTROSCOPY
65. 65 AUGER ELECTRON SPECTROSCOPY How Do I Use Use when I need visualization of spatial distribution of chemical elements on the top few atom layers of sample surface Ideal for metals but polymers may degrade during analysis Very few labs have this equipment High cost per sample
66. 66 FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR)
67. 67 FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR)  Chemical analysis  Identifies organic materials - plastics, lubricants, adhesives and cleaning agents  Ideal for the direct, in situ, analysis of organic contaminants on metallic surfaces
68. 68 FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR)
69. 69 FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR) How Do I Use Frequently for chemical analysis of organic material (paints, plastics, etc.) Fast, inexpensive test Most chemical test labs have FTIR
70. 70 GAS CHROMATOGRAPHY MASS SPECTROMETRY (GC-MS)
71. 71 GAS CHROMATOGRAPHY MASS SPECTROMETRY (GC-MS)  Quantifies organic volatile and semi- volatile compounds  Gas chromatography (GC) separates mixtures into individual components  Mass spectrometry (MS) - identifies the various components  Each compound has a unique mass spectrum that can be compared with mass spectral databases  Through use of standards, quantitation is also possible  GC-MS analysis can work on liquids, gases and solids
72. 72 GAS CHROMATOGRAPHY MASS SPECTROMETRY (GC-MS) How Do I Use Frequently for chemical identification of volatile compounds of solids, liquids, and gases Examples – outgassing of plastic food containers or can coatings, composition of vapors, chemical fumes, etc. Fast, inexpensive test Most chemical test labs have GC-MS
73. 73 X-RAY DIFFRACTION (XRD)
74. 74 X-RAY DIFFRACTION (XRD)  Characterizes crystalline materials  Enables quick phase identification for a large variety of crystalline samples  Provides information on structures, phases, preferred crystal orientations, average grain size, crystallinity, crystal defects, etc.
75. 75 X-RAY DIFFRACTION (XRD) How Do I Use To identify the composition & crystalline forms of metals Degree of Crystallinity of plastics and paint coatings Short time to process sample Low cost per sample Only useful for crystalline materials, not amorphous materials
76. 76 X-RAY RADIOGRAPHY
77. 77 X-RAY RADIOGRAPHY  Radiography is an imaging technique that uses x-ray radiation to view the internal structure of an opaque object  The X-rays that pass through the object are captured behind the object by a detector
78. 78 X-RAY RADIOGRAPHY X-ray of Broken Handrail Bracket
79. 79 X-RAY RADIOGRAPHY How Do I Use Occasionally used to determine if cracks are prevalent near a corrosion or product failure site, and if the cracks contributed to the issue
80. 80 SUMMARY
81. SUMMARY TOOL PRIMARY USE Optical Microscopy Document original condition (~2,000X) SEM High quality image of as-is surface (~500,000X) EDS Elemental analysis of surface Metallographic cross- section Edge view of sample AFM Surface features on atomic scale XPS Chemical compounds on surface
82. SUMMARY TOOL PRIMARY USE Confocal Microscopy Analysis of non-flat surface TEM Extreme detail – atomic sale AES Visualization of chemical elements on top atom layers FTIR Chemical analysis of organic material GC-MS Chemical analysis of volatile material – solids, liquid, gas XRD Composition of crystalline material X-RAY Internal cracks or defects in material
83. 83 SUMMARY  Forensic engineers have many technically-advanced analytical tools at their disposal  Each tool has its own unique capability to help determine why a product failed  Many of the tools are complementary  Frequently more than 1 tool is needed to get the whole story  It is to attorneys’ advantage to be aware of these various tools and capabilities to maximize the value of an expert to the theme of the case
84. 84 QUESTIONS Bob Iezzi rai-technical-solutions.com riezzi@rai-technical-solutions.com (610) 761-6721 Corrosion Paint Technology Metal Coatings Pretreatments Plastics Expert Witness

Editor's Notes

Good afternoon ladies & gentlemen. Thank you for attending this webinar. My purpose of this session is to provide some helpful information that you can use when dealing with the forensic engineers that you may retain as expert witnesses.

What I’m going to cover today is an overview of what forensic engineers do, and the various types of analytical tools they commonly use to provide value to attorneys as expert witnesses. I will cover 13 frequently-used analytical tools - focusing mainly on the type of information each provides. I will also discuss 3 case studies where I personally have used these tools while serving as an expert witness. Then a brief summary.

Lets 1st talk briefly about what forensics engineers do

It quite straight forward actually. Forensic engineers identify what went wrong; why it went wrong, and how it went wrong. An absolutely critical aspect of the analysis that a responsible forensic engineer and expert witness provides is that their results, conclusions, and opinions must be unbiased, accurate, and defendable – even during rigorous cross-examination by opposing counsel and/or Daubert or Fyre challenges.

Now let’s dig into the various analytical tools that a forensic engineer can use. I should mention that this webinar is not intended to be a technical treatise on how these sophisticated, complicated instruments work, but rather provide the kind of info these various techniques can provide, and what you, as top-flight attorneys, can request from experts. Also, the webinar is not meant to be inclusive of all types of analytical techniques available to forensic engineers – time simply would not permit that. Rather, I focus on the most common tools that I personally use in my expert witness & consulting practice in corrosion, paint coatings, metal coatings, chemical pretreatments prior to application of paint or metal coatings, and plastics.

Of course, the 1st step in any forensic engineering analysis to simply examine the sample under magnifying glass. This first step usually helps me determine what types of tests I need to do to obtain a broad picture of what went wrong. By the way, I promise this is the last picture of me.

This slide and the next one lists the various analytical tools I will discuss in this webinar. These techniques primarily involve the use of a microscope – hence the fancy name microscopy.

Note that there are many different techniques available to a forensic engineer. The choice depends on the type of info needed and the characteristics of a particular sample. It is very important to stress that most times I have to use 2 or 3 different techniques that are complementary to best reach unbiased, accurate conclusions. For example, consider if I’m analyzing a plastic material. FTIR analysis might tell me the sample is either nylon 6 or nylon 6,6, which are 2 different types of nylon. Nylon 6 and 6,6 have very similar FTIR spectra and can’t tell the difference between the 2. But if I need to know the specific type of nylon, I can then use a technique called DSC (differential scanning calorimetry) which gives me the melting point of the sample. Because nylon 6 and 6,6 have different melting points, I know if the sample is nylon 6 or nylon 6,6 – whereas with FTIR alone, I could not make that distinction. So this is a good example of the need to use complementary techniques to find out what I need to know.

So now let’s dive into each analytical tool. I’ll start with optical microscopy.

Optical microscopy is a fancy word for examining a sample under a light microscope – similar to evaluating a sample in a high school biology or chemistry lab. You simply put the sample in its original or “as-is” condition on the microscope stage – that is, under the lens. There is no specialized surface preparation of the sample needed. Most scientific optical microscopes provide direct links to a camera and TV monitor to facilitate taking photos, and have different light filters (e.g., polarized light) that provides sample contrast to see different features such as crystallization in polymers. Magnifications from 2X to 2,000 X are possible with resolution of about 0.5 micron.
Micron is 1 millionth of a meter – so you can see very fine detail using an optical microscope.

This is an example of my work using an optical microscope. This is a surface view (about 40 magnification) of a lead coating applied to a copper sheet. The coating corroded in spots. The red corrosion spot shown was caused by a pore in lead coating, and is about 0.5 mm in diameter. Certain lead corrosion products are red.

Optical microscopes are general purpose instruments. I use them to document the original condition of almost every sample I analyze. The polarized light feature is vey helpful in my work in determining the structure of plastics, and why a plastic may have failed in service.

I use scanning electron microscopy in most of the expert witness work I do. This is a high magnification micrograph of plant pollen - shown to demonstrate the capability of SEM.

SEM (read the slide). Because SEM I so surface sensitive and has such good resolution, I often use it to determine what’s on the surface of a material that may have caused paint to have poor adhesion and/or fail in service.

SEM can achieve more than 500,000X magnification. That’s about 250 times the magnification of the best optical microscope. Limitations of SEM are that samples must fit in the specimen chamber (usually about 6” max), samples must be placed in a high vacuum chamber for analysis, and must be electrically conductive. Non-conductive samples like plastic or paint must be coated with an extremely thin coating – usually gold, carbon or platinum.

This is a photo of the SEM in a lab that I use frequently – shows the SEM instrument & scientist operating it.

This is an example from my work. It involved fracture of a metal handrail bracket – lawsuit filed when handrail broke & person fell down steps. You’re looking at a 500X SEM micrograph of the fracture surface. Smooth facets (use cursor – focus on region) show brittle failure – like a brick snapping in half (use cursor to show 2 other smooth areas). Significance of brittle fracture is that it indicates that the handrail bracket failed instantaneously by too much wt on it.

I use SEM in nearly all my assignments because I get very high quality images of the original condition of the sample.

Energy Dispersive x-ray analysis (EDS) is used in conjunction with SEM to get elemental analysis.

It provides elemental results because the impact from the scanning electron beam on the sample produces x-rays that are characteristic of the elements present.

This is a typical spectra – showing elements at a particular location. This is an example from my work.

This is an extremely valuable tool that goes hand in hand with SEM. I get rapid elemental analysis on specific locations on a sample that is being analyzed in the SEM. Very cost effective.

Ex of my work. Painted AL. Shows corrosion of Al at cut edge.

I just covered 4 of the tools that I use most often. I’m now going to discuss 3 case examples where I used these tools before going back to the remaining tools I use less frequently.

Involved corrosion of painted Al door and window frames made of Al extrusions. Dozens of residential bldgs. in coastal areas showed excessive and premature corrosion at the cut edges of the frame sections. My role as an expert witness was to determine why they failed so quickly – usually within a few years. Home owners filed suit against who they bought the windows from, who sued everyone else – al mfger, company that applied the paint, the window mfger, and the paint co.

This photo shows me doing paint adhesion tests on many of the failed samples. I lied about not showing another photo of me.

Example of the corrosion on a door frame section. ~2-3”.

Common type of paint system used in industrial painting operations.

SEM micrograph of metallographic cross-section of paint lifting from cut edge. Primer and topcoat lifted off the surface. Good adhesion of the primer/topcoat – so-called intercoat adhesion good.

From the previous slides, I confirm that the primer and topcoat have good intercoat adhesion, and are lifting off the surface together. BUT why ?? So I take a closer look in the next slide.

Higher magn SEM micrograph (2000X) of where the paint is just starting to lift from the surface. I analyzed Loc C (point out) using EDS and found it to be the pretreatment layer. So its clear that the paint was lifting off the pretreatment layer.

You can see from this example how powerful the techniques of cross-sectioning the sample and using SEM/EDS – 3 complementary analytical techniques..

Project involved premature corrosion of copper roofing coated with a thin lead coating. Pb has been used in roofing and statues for centuries in Europe bec it lasts hundreds of years in most environments. Lead coated copper occasionally used on buildings in the US bec the lead gives a dull gray, antique look that is desired by some – and the lead should last decades. The lead is usually applied to copper sheet bec the lead is not very strong as a stand alone material, and the copper substrate gives the structural strength needed, particularly for roofing. In this case, LCC was used on a private residence bec the owner wanted an antique look. Unfortunately, the lead corroded within 2 years and the roof was a visual nightmare – with red and white corrosion products all over the roof. So much lead corroded and was washed off by rain that lead contaminated his lawn area – he became a federal and state HAZMAT site and had his property monitored by federal and local environmental agencies. Needless to say the owner was not happy and sued the contractor, architect, and LCC mfger. My role was to determine why the LCC corroded prematurely.

Here’s a photo of a small roof section. You can see the non-uniform appearance and corrosion. I analyzed the circled section, along with many others.

This a OM of a cross-section that section. The most prominent feature is the large uncoated area (a pore) and thin coating on the side exposed to the atmosphere – the outer surface. Note the other side (inner surface not exposed to the atmosphere) had a relatively uniform & thicker ctg. Ctg on outer side was below ASTM spec for ctg thickness; inner side was in spec. This was typical of the dozens of samples I analyzed.

SEM (2000X) of surface view - showing pore in the Pb ctg (Loc A) and exposing some of the copper substrate. Location A was analyzed with EDS & showed the copper substrate (next slide).

EDS of pore – location A from previous slide - shows the copper substrate. Pb/Sn intermetallic which binds the lead to the copper. There is some tin added to the lead so it flows better and bonds to the copper.

Project involved Mn Phos pretreatment for A/C condensers. MnP pretreatment is a thin ctg applied to metals used to help with lubrication of moving parts, particularly at break-in periods. Most common is for auto engine crank shafts. Mn Phos is a crystalline ctg (called a pretreatment bec it is so thin) that absorbs lubricating oil and holds it during the break-in period. The MnP ctg itself has lube properties – so it + the oil is a temp break-in lube. This project involved MnP ctg for AC condenser parts,. The problem occurred when the AC mfger switched MnP chemical suppliers. With the new MnP supplier, premature failure of the condensors occurred very rapidly. The AC mfger sued the new chem supplier. I was called in as an expert in pretreatment chemicals to find out why the new MnP product failed.

This slide shows a 200X SEM of surface of the original or current MnP pretreatment (on right) vs the one the AC mfger switched to (on left). The current MnP pretreatment was very uniform and smooth, and had the appearance of a typical MnP ctg. The alternate MnP was very rough, non-uniform, and porous. With this SEM info, and extensive lab testing of both MnP chemicals, I was able to determine that the non-uniform, porous MnP ctg wore away critical components of the condensor seals at an accelerated rate, causing the compressor to lose pressure and not pump refrigerant.

This slide has a SEM micrograph (200X) of a different area of the compressor component with the alternate MnP ctg. Note the non-uniform MnP crystals, and the areas with no MnP ctg at all. Those non-coated areas were also rough and contributed to the premature seal wear and compressor failure.

I will jump back to cover the remaining analytical tools. First talk about confocal scanning microscopy.

Confocal microscopy is relatively new – about 20 years old. The biggest advantage over other types of microscopes is that it gives excellent images of 3 dimensional surfaces, such as a sharp bend on a sample, or a sample with a rough surface. Other types of microscopes usually only detect features of the flat portion of a sample – non-flat surfaces will not be in focus. Other advantages of confocal microscopy is that no sample prep is needed, and you can get quantitative measurements and visualization of surface roughness.

Here is an example of the tremendous visualization possible of the “as-is” surface. We are looking at a small section of a 1 Euro coin – a section about 800 microns square, which is nearly 1 mm square. So the entire section you are looking at is slightly less than 1 mm square (use cursor). Top of star raised about 30-50 microns from the flat area of the coin. You can tell by the color difference from red to blue (shown here) and the associated color scale bar on the right (shown here). Dark red is the baseline of 0 microns – dark blue gives the depth from the top of the star (about 50 microns). Confocal microscopy is very useful in determining surface roughness of a sample that may have failed in service, or identifying a manufacturing defect.

I only use confocal microscopy when I need extreme detail about the surface features of a sample. I use it rarely because very few labs have this equipment, and the cost per sample is high

I’ll now move to Atomic Force Microscopy (AFM)

(Read slide) NM = 1 billionth of a meter

This is an example of the extreme surface sensitivity of AFM. Looking at the surface of a sample. Hard to read the vertical scale bar on the right (use cursor) – but red is about 0.1 nm (use cursor) and the light yellow (use cursor) about 0.2 nm. NM = 1 billionth of a meter. We are measuring surface roughness difference (between red and yellow) of 1 tenth of a NM - ~1 tenth of a billionth meter. AFM is a tremendous tool for surface characterization.

I use AFM (read slide)

XPS provides info on the type of chemical compound that is present on the surface of a sample. Most other techniques give elemental analysis, but XPS gives chemical compound info. E.g. other techniques I discussed might identify Na and Cl, but XPS will tell me if the Na and Cl are chemically bound as salt, or some other cpd.

XPS Spectra shows various moisture components on sample surface – technique works by measuring binding energy of the material. E,g, Useful in determining if contamination of a surface prevented good paint adhesion.

NM = 1 billionth of a meter - extremely surface sensitive technique – e.g. detect chemical compounds on surface that may have caused product failure in service.

TEM produces an image of a material by shooting beams of electrons through an extremely thin sample. TEM gives extremely fine detail of the material. TEM gives better images than SEM or optical microscopy, but requires much more sample prep – mainly from cutting the very thin sample using a technique called microtoming. NM = 1 billionth of a meter

As an example, here are TEM images of Mo cpds. Photo D – clearly showing rod-like structure ~10 nm in dia. This image gives an idea of the level of detail that is possible using TEM. I use TEM on cases where I need extreme details of the material structure – perhaps failure analysis of an automotive axle that broke and caused an accident – i.e. why did the axle break.

Microtome cuts very thin slices of a sample for analysis

This is an example of what Auger can do in helping me as a forensic engineer. I can visually see how chemical elements are distributed on a sample surface – which is a powerful tool in explaining my results to a judge and jury. This particular example compares elemental images to the SEM image. SEM image on left shows a surface defect – middle photo shows the Auger image of the same spot for indium – the right photo shows the Auger image of that same spot for Selenium. Therefore, we learned that the surface defect is composed of Indium and Selenium

Helps me identify surface contamination that may contribute to product failure

Ex of FTIR spectra. FTIR analysis is like comparing finger prints. You compare the sample spectra (shown in the bottom) to a reference standard spectra that matches the sample (top spectra). Computer software does the matching.

GC-MS quantifies organic volatile compounds like oils and greases. The GC component separates mixtures into individual components. Then the MS component identifies the various compounds by comparing to reference databases. The other techniques I covered today deal with solids only, and cannot analyze liquids or gases.

I use mainly to identify composition of a metal sample – is it brass, steel, etc. I also use XRD to determine the Degree of Crystallinity of plastics and paint ctgs which determines their mechanical properties such as strength. Degree of crystallinity has a significant effect on the properties of a plastic or paint. Fast, inexpensive test to run. Cannot use to analyze amorphous materials bec amorphous materials have no crystal structure.

Basically the same as when you get x-rays of your body

Ex from my work – supplemented the SEM of fracture surface of broken handrail bracket I showed several slides ago.

This and next slide summarizes the 13 analytical techniques I covered today.

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