Upgraded SEM/EDX System

We recently replaced our Topcon SM-300 SEM/EDX system with a Topcon ABT-32 SEM/EDX system with an Evex EDX and imaging computer program.  Our present system is shown below:

We have realized a number of improvements as a result.  Among these are:

• Image digitization at 256 x 256, 512 x 512, 1024 x 1024, 2048 x 2048, 4096 x 4096, and 8192 x 8192 pixels.  The old system only digitized SEM secondary electron (SED) and backscatter (BSD) images at 1024 x 1024 pixels.  Most of our SED and BSD images will now be taken at higher pixel resolution, while 512 x 512 is often the best resolution for EDX elemental mapping, since the x-ray emission volume beneath the surface is much larger than the surface beam entrance cross section.  EDX samples about 1 to 2 micrometers deep into a sample and the emission volume is about 1 micrometer wide, so the resolution is much lower in EDX mode than in SED mode.
• We can now map up to 8 elements at one time in the EDX mapping mode, or while making line scans.  We were previously only able to perform the mapping of one element at time.  This greatly reduces the time it takes to produce a map of several elements.  We can now easily color code each characteristic x-ray emission map and combine them in various ways, including as superpositions on a SED surface topography image.
• The EDX energy dispersive detector is on the same side of the chamber that the secondary electron detector is on, which means both modes image the sample optimally without having to rotate the sample with respect to the incoming electron beam as we had to do on the SM-300 system.  Electron beam shadowing effects are now similar in both the SED and EDX images.
• The EDX x-ray count rates are slightly higher with the new detector, especially at the lower mass element end of the spectrum.  We are getting a slightly higher energy resolution also with this detector.
• The new Robinson Back Scatter detector has a slightly higher count rate than our previous detector did.  The back-scatter detector allows one to see higher mass element concentration areas as slightly brighter than lower mass elements.  Because one is only detecting high energy electrons from the sample, the volume emitting the signal is substantially deeper into the sample than in a SED image.  The resolution is somewhat less in the BSD mode than in the SED mode due to sub-surface spreading of the electron beam before many of the high energy electrons are back-scattered. 
• SED images can generally be made at higher resolution than on the SM-300 system. The resolution specification is 5 nm.  The SM-300 had a specification of 4 nm, but this was impractical because achieving that resolution required such small apertures in the electron beam column that they quickly became dirty with carbon accumulations.  For practical use, we therefore had to replace the really small apertures with larger apertures and our resolution was degraded to about 7 nm.   The ABT-32 system is based on a very different aperture geometry which allows larger apertures placed differently.  Practical operation at up to 40,000 times magnification is now reasonable.
• All the data is acquired with one computer now, rather than one for SED and BSD images and another for EDX analysis.  Export of data and images into reports is also more easily accomplished now.
• The sample chamber is slightly larger now than it was in the SM-300, though that was also a large chamber.
• We have a wider variety of sample holders and clamps.
• The belt sample manipulation controls are tighter on this system.  Those on the SM-300 had more hysteresis than one would like.

Dr. Lorrie A. Krebs and Dr. Kevin A. Wepasnick are the primary SEM/EDX users and both of them are very much enjoying using the improved system.  Please feel free to talk to them directly about any SEM/EDX analysis projects you may have.

NACE Interview with Lorrie A. Krebs, Ph.D.

NACE, the National Association of Corrosion Engineers, conducted a series of interviews with prominent NACE members who participated in the Corrosion 2011 Conference about how NACE membership had affected and enriched their careers.  Lorrie A. Krebs, Ph.D., Vice President, Senior Scientist, and co-owner of Anderson Materials Evaluation, Inc. was selected for one of these NACE interviews.

Lorrie served as the Chairman of the Annual Program Conference Committee for Corrosion 2011.  She will be performing the same job at the upcoming Corrosion 2012 at Salt Lake City, Utah from 11-15 March 2012.  She tried to wiggle out of the interview, but NACE was insistent, so here it is:

http://www.youtube.com/watch?feature=player_detailpage&v=s-BMntzIlFg

How Wonderful it is to be a Scientist!

The reality in which we live is full of beauty and wonder, but there is much more beauty and wonder if one knows enough science to appreciate many aspects of that beauty.  Knowing science, we can better appreciate the many ways that something might be different than it is.  We can better appreciate what is beautiful in its simplicity and what is beautiful in its complexity.

When I was a senior at Brown University working on my senior thesis on metals with defect structures in them, I had a discussion with a nice and very intelligent particle physicist who had taught me the introductory physics course for physics majors.  Half the freshmen physics majors were no longer physics majors by the time that course was over, but it was not because the professor was a poor teacher.  He was demanding.  Now when I told him about my project though, he was appalled and said that I was doing dirty engineering.  He told me that the beauty of physics was in simplicity.  I adamantly argued back that while simplicity was indeed often beautiful, so was complexity.  Complexity in materials allowed us to tune materials in many ways to get the properties we wanted for many purposes.  It was beautiful in that it made materials much more individualistic and gave us as molders of their properties much more power.  Of course this complexity could tax our brains, but was it not wonderful to be so challenged?  Wasn't there beauty in something that required us to be the most we could be mentally?  He was not convinced.

Years later, the work of physicists on amorphous materials came to be widely recognized as important physics, including a Nobel Prize award, and I hoped that my old professor had taken note of this.  Still later, there was a great deal of excitement in chaos theory and it was recognized that even relatively simple systems could behave in very complex ways.  Again, I wondered if my professor had taken note.

About seven years ago, I and a friend who is also a materials physicist, had a discussion about space and time.  It turns out that we each had already arrived at the conclusion that space and time were not likely continuous  as assumed.  We each thought that there were units of space volume and of time that were discrete in keeping with discrete packets of energy and matter in physics.  It is interesting to note that the director of the Fermilab Particle Astrophysics Center near Batavia, Illinois thinks this may be the case now also.  He is conducting experiments on the noise that would arise as a result to test this hypothesis now.  Physics itself and the universe it describes is just wonderfully complex and amazing because of this.

I have had an interest in the science of climate and the hypothesis that man-made emissions of infra-red absorbing and emitting gases such as carbon dioxide might have catastrophic effects on the climate for many years now.  The Earth's climate is wonderfully and beautifully complex.  It's understanding is in no way settled science, despite the many ridiculous claims that it is.  As with so many other manifestations of science and physics, we have many very essential and basic questions to answer yet.  We actually know little about how additions of carbon dioxide will affect the climate.  I have argued that there is good reason to believe the effect is much smaller than many alarmists would have us believe.  This is not to say that the effects of carbon dioxide are unimportant, but that part emitted by man is not nearly as important as has been claimed by many.  The dominant effects upon climate are very much those of nature alone.  This at least is my prediction based on my understanding of the essential physics.  But, I am very sure we will be able to watch many really beautiful insights into the climate develop as we continue to pursue our understanding of the physics of the climate.

We see many instances of beautiful physics in the materials we analyze in our laboratory for our clients.  These materials can be amazingly complex as we unravel their compositions and properties.  It is a most beautiful job to be a scientist earning a living by investigating the properties and wonders of materials.  We get to work on many of tens of thousands of types of materials processed in tens of thousands of ways and used for thousands of applications in tens of thousands of environments.  There is wonderful beauty in these materials and challenge after challenge in learning to appreciate it.

Kevin A. Wepasnick, Ph.D. Joined Staff

Kevin A. Wepasnick, Ph.D., joined the Anderson Materials Evaluation staff as a scientific project manager in July.  His prior experience at The Johns Hopkins University was extensive and is summarized in his brief biography below:

Dr. Wepasnick recently joined the staff of AME after completing his Ph.D. dissertation work at The Johns Hopkins University (JHU) in surface chemistry.  There, he focused his research on the surface analysis of functionalized and modified carbonaceous nanomaterials and metal nanoparticles.  Primarily tasked with understanding the chemical effects of oxidants on carbon nanotubes, he worked on derivatization methods to label specific functional groups on their surfaces to improve quantitative x-ray photoelectron spectroscopy (XPS) analysis of oxidation effects. Beyond XPS, Dr. Wepasnick applied a wide range of characterization techniques to explore the surface chemical and morphological effects of oxidation, including FTIR, TEM, Raman, Auger, AFM, and STM.  He also was responsible for running and maintaining the on-campus surface analysis laboratory.  In this capacity, he interfaced with over twenty independent research groups from across the JHU system, from outside universities, and from industry.  The JHU system includes The John Hopkins Applied Physics Laboratory and Johns Hopkins Medical, a $5 billion medical organization more heavily funded for medical research than any other university hospital system in the United States. He has experience working with a wide range of materials including biomedical materials, metal and metal oxide particles, self-assembled monolayers, CVD process films, and nanoparticles of various phases and compositions. He enjoys using a multitude of analytical techniques to characterize materials and to solve materials problems. 

Dr. Lorrie A. Krebs and I are delighted to have him on board with us.  His knowledge, versatility, and enthusiasm have immediately made him invaluable to our materials characterization and failure analysis missions.

Activated Carbon Website Uses AME SEM Images

A new website for activated carbon has used the activated carbon SEM images from our website used as an illustrative example of our SEM analyses.  These images were made by Dr. Lorrie Krebs.  The Australian website using these images has done so with our permission.  That website is here and uses the images to show the high surface area of activated charcoal.  The example from our website is given below:

Illustrative Example 2: Activated Carbon

Figure 1 is a low magnification (50X) SEM micrograph of activated carbon particles of an air filter. Activated carbon is similar to graphitic carbon except that it has a high degree of porosity and a large internal surface area. Activated carbon is mostly used as a filter material for removing impurities from water and various gases. Figure 2 is a moderately magnified (1000X) SEM micrograph (of the particle to the right in Figure 1) indicating internal surfaces and porosity in the activated carbon. This sample was sufficiently conductive that it was not coated.

Figure 1 Figure 2

Examining a High Intensity Electron Gun Used Cathode with Optical Microscopy

We make it a habit to examine samples sent to us with optical microscopy even if the requested analysis is x-ray photoelectron spectroscopy (XPS), thermal analysis, electrochemistry, or FTIR spectroscopy.  While optical microscopy is not the newest of laboratory techniques, it provides relatively easily obtained valuable information.  It allows us to document the appearance of a sample so that other materials characterization results can be matched with certain material appearances over time.  The next similar sample sent by a customer for analysis may not be as similar as thought.  One of most frequent things we learn is whether there are two or more chemical or structural phases present.  There may be phases present which optical microscopy will not reveal, but it does very often make it clear that multiple phases are present which the eye may not have perceived or perceived in such detail.  This is very important to know when interpreting the quantitative elemental composition determined by XPS or EDX (Energy Dispersive X-ray analysis) or various phase change features in a thermogravimetry, differential scanning calorimetry (DSC), or thermomechanical analysis.

In the optical microscopy images below, we will examine a cathode which has seen 25 months of service in a high intensity electron gun used in an x-ray source.  This tungsten cathode consists of a thin circular foil mounted on three legs and doped with cesium to lower its work function.  A filament consisting of a serpentine etched circular tungsten foil sits behind it and produces a flood of electrons which are accelerated at 12 KeV into the back side of this cathode.  The most common failure mode is that the tungsten filament separates at a grain boundary between grains, which often grow with usage until a single grain traverses the entire current path and the grain boundaries become the strong electron scatterers or the high resistance points until failure occurs at a grain boundary.  Another failure mode has been that one of the spot welds holding the three legs of the cathode fails and the cathode shorts out to the extractor lens of the electron gun.  In the case of this cathode/filament assembly, the failure was the rupture of the filament.

The cathode shown below was imaged with an inspection microscope with illumination at an angle of about 30 degrees relative to the surface normal.  This provides an image much like what the eye sees commonly, though at a much lower magnification.

This surface is highly reflective, so much of the detail is lost.  But, we do get a sense that many irregularities and perhaps chemical phases or surface roughness result mostly near the three legs of the cathode.  If we place the illuminating light at an angle of about 65 degrees to the surface normal, we get a better image which makes it clear that there is great variability of surface condition on this used cathode.  These are also very much enlarged grains with usage etched grain boundaries.

Looking at the cathode at higher magnification we see striation patterns more clearly:

Are these bright lines due to chemical phases or are they ridge lines of raised surface areas?  Let us make use of the metallographic microscope with light normal to the surface of the cathode.

This microscope does not offer the depth of field of the inspection microscope, so we cannot see the three legs of the cathode any more.  But, we do see that there is a great variation in surface reflectivity and this may create a great variability in local surface electron emission in use.  We can make use of a Nomarski interference phase contrast feature of this microscope to differentiate areas of about the same surface height from those of different heights.  This mode inserts a prism at the objective lens and uses two polarized films to create images similar to those below:

The areas of a given color are at the same distance from the objective lens, so we can learn more about the surface topography now.  If the material being imaged were partially transparent to visible light, we would have to be prepared for possible phase contrast due to materials of different index of refraction, which would probably be due to different chemical phases.  This tungsten is to reflective for that to be of concern here.  The presence of the colored patterns over a given grain do mean that there is surface topography on that grain.  Let us look at a higher magnification at parts of this cathode surface:

At twice the prior magnification:

The upper image of these last two was a relatively non-reflective area near a leg and the very surface rough grain in the lower left corner of the lower image was also near a leg.  Note the very wide grain boundary on the right side of the large blue-green grain in the lower image also.  Such a wide grain boundary in the filament would likely become a point of separation and failure.  The surface roughening is probably due to one of these reasons:

• Impurities from the cooler legs migrate to the cathode surface near them and promote the surface ridge lines and other roughened topography.
• Grains near the legs are slightly cooler and impurities incident upon the surface have a higher probability of sticking on the surface and promote surface roughening.
• The surface roughening is a function of a certain range of temperatures due to a phase change of the tungsten crystal structure which occurs in a certain temperature window.  Tungsten is usually said to have the bodied centered cubic (bcc), which is its thermodynamically stable phase.  It also has a beta phase of simple cubic structure which grows as rods under oblique incidence sputtering of tungsten onto a substrate.  Perhaps some impurities may stabilize the simple cubic structure within a certain temperature window.

The last image above seems to show a large single grain whose top left corner is breaking away, perhaps due to the spread of an impurity from the highly roughened grain in the lower left corner.  It would be interesting to perform XPS and EDX analysis of this cathode to gain further understanding of the mechanisms for the roughening of some grain surfaces.  Would we detect impurities responsible for this?

Nomarski phase contrast interference sure can produce some colorful and beautiful images!  They are also useful.

Move to a Larger and Improved Laboratory Facility

In mid-February 2011, we moved from our old laboratory of 3,592 square feet into our new Columbia, Maryland laboratory of 5,439 square feet in a facility less than 1 mile away from our old laboratory.  While our old laboratory was largely taken as was from a prior medical services laboratory, we were able to design the layout of our new laboratory to better suit our needs.  We have added an area suitable for environmental and corrosion testing of materials, where it is well-separated from the laboratories we need to keep clean.  We have further lab areas suitable for future expanded capabilities.  Our laboratory bench and cabinetry space has increased, so we can keep more laboratory tools and implements out and readily available.

Within 1 week of our move, we had all of our spectrometers and microscopes and our thermal analysis instruments up and running again, with the exception of our EDX.  We replaced our EDX x-ray detector crystal with one having better carbon and oxygen resolution and detection than our old crystal had provided.  Fortunately, work has been pouring in since our move, since we have some very significant liabilities to pay as a result of this move!  Lorrie A. Krebs, Ph.D., Stephanie J. Roberg, M.S., and Charles R. Anderson, Ph.D. are eager to talk to you about how we can help you solve your materials characterization, development, processing, failure analysis, and quality control problems and create new materials usage opportunities for you.  Our contact information is given in the sidebar, including our e-mail addresses.  Feel free to talk to Dr. Lorrie Krebs about your corrosion, electrochemistry, metallography, and fracture failure analysis needs.  Talk to Stephanie Roberg about FTIR infra-red spectroscopy requirements and thermal analysis by thermogravimetry (TG or TGA), differential scanning calorimetry (DSC), or thermomechanical analysis (TMA).  Finally, discuss surface quantitative elemental and chemical analysis, adhesive bonding problems, and general multi-technique analysis projects with Dr. Charles Anderson.

Those of our clients who are local, please feel free to visit our new laboratory and office facility.  Or if you come by to drop off samples or to discuss a materials problem, please feel free to request a tour of the labs.

Our new XPS Surface Analysis Laboratory:

Our new SEM/EDX Laboratory:

Our new FTIR Infra-Red Spectroscopy Laboratory:

Our new Thermal Analysis Laboratory:

Our new Electrochemistry and Corrosion Evaluation Laboratory:

Our new Optical and Metallographic Microscopy Laboratory: