microstructural analysis

Looking At A Grain!

Sia Afshari, Global Marketing Manager, EDAX

November seems to be the month when the industry tries to squeeze in as many events as possible before the winter arrives. I have had the opportunity to attend a few events and missed others, however, I want to share with you how much I enjoyed ICOTOM18*!

ICOTOM (International Conference on Texture of Materials) is an international conference held every three years and this year it took place in St. George, Utah, the gateway to Zion National Park.

This was the first time I have ever attended ICOTOM which is, for the most part, a highly technical conference, which deals with the material properties that can be detected and analyzed by Electron Backscatter Diffraction (EBSD) and other diffraction techniques. What stood out to me this year were the depth and degree of technical presentations made at this conference, especially from industry contributors. The presentations were up to date, data driven, and as scientifically sound as any I have ever seen in the past 25 years of attending more than my share of technical conferences.


The industrial adaptation of technology is not new since X-ray diffraction has been utilized for over half a century to evaluate texture properties of crystalline materials. At ICOTOM I was most impressed by the current ‘out of the laboratory’ role of microanalysis, and especially EBSD, for the evaluation of anisotropic materials for quality enhancement.

The embracing of the microanalysis as a tool for product enhancement means that we equipment producers need to develop new and improved systems and software for EBSD applications that will address these industrial requirements. It is essential that all technology providers recognize the evolving market requirements as they develop, so that they can stay relevant and supply current needs. If they can’t do this, then manufacturing entities will find their own solutions!

*In the interests of full disclosure, I should say that EDAX was a sponsor of ICOTOM18 and that my colleagues were part of the organizing committee.

Looking at the World of Microanalysis in Color

Tara Nylese, Global Applications Manager, EDAX

Several years ago, I was talking to a customer, who asked whether we could change the color scheme of the EDAX TEAM™ software. He said was that it was hard for him to tell the difference between the spectrum background and the cursor. I replied, “Well, the cursor is a lime green and the background is more like a gray-gre…..Oh, wait, you’re colorblind, aren’t you?” Surely enough he was, and while I can’t “see” his perspective, I can listen to and respect it. Thus, the motivation of this blog is to let our customers know that we in Applications listen to them and take their needs seriously.

In this specific case, I am happy to report that we just recently received feedback on the new EDAX APEX™ software, and one comment was that the user really liked the “contrast” of the red spectrum on the white background – see the image below.

More generally, it is one main goal of the EDAX Applications team to make sure that we capture the “real world” customer feedback and incorporate it as much as possible into future product enhancements, bug fixes and new generations of products. Each of our Worldwide Apps team members can talk to upwards of ten customers a week. These conversations are usually in interactions such as support calls, training sessions and demos. At each opportunity, we hear tremendously valuable real-world customer perspective, and very often we learn what we can’t “see” ourselves. Often, if I’m asked to share my thoughts, my words are just a colorful patchwork of years of customer ideas all melded into a microscopy amalgam.

Customer perspective is so important, in fact, that it is a cornerstone of the EDAX App Lab Mission Statement. A few years ago, I compiled about three pages of descriptions of what people thought of when they thought of Apps, and then condensed them down into the following statement that hangs on our HQ App Lab walls.

The EDAX US App Lab uses technical expertise and creativity plus a strong focus on understanding the needs of our internal and external customers to drive excellence in innovative analytical solutions. The applications group supports company-wide efforts to provide real-life value and benefits to our customers which differentiate our products in materials analysis.

Now to get back to the colors which are available for maps in our software. One of the lesser known functions is the ability to select and edit your color palette:

Using this option, you can choose from a 40-color palette, seen here. Remember to click on the element in the periodic chart first, then select your color.

Since I brought up the topic of colorblindness, I’ll also use a colorblind app that simulates how a Red/Green colorblind person sees the world (or our color palette).

Note the green color of O and P, and see how closely it compares to the yellow color of the lanthanide/actinide series!

Finally, to summarize the Applications message: to our current customers – thank you for sharing your thoughts; to all our applications team colleagues – thank you for gathering so much wide-ranging information and promoting the importance of it internally, and to all our future customers – when you chose EDAX, you’re choosing to join a dynamic microanalysis company, which strives to develop the most meaningful features and functions to meet your microanalysis needs.

Aimless Wanderin’ – Need a Map?

Dr. Stuart Wright, Senior Scientist, EDAX

In interacting with Rudy Wenk of the University of California Berkeley to get his take on the word “texture” as it pertains to preferred orientation reminds me of some other terminologies with orientation maps that Rudy helped me with several years ago.

Map reconstructed form EBSD data showing the crystal orientation parallel to the sample surface normal

Joe Michael of Sandia National Lab has commented to me a couple of times his objection to the term “IPF map”. As you may know, the term is commonly used to describe a color map reconstructed from OIM data where the color denotes the crystallographic axis aligned with the sample normal as shown below. Joe points out that the term “orientation map” or “crystal direction map” or something similar would be much more appropriate and he is absolutely right.

The reason behind the name “IPF map”, is that I hi-jacked some of my code for drawing inverse pole figures (IPFs) as a basis to start writing the code to create the color-coded maps. Thus, we started using the term internally (it was TSL at the time – prior to EDAX purchasing TSL) and then it leaked out publicly and the name stuck – my apologies to Joe. We later added the ability to color the microstructure based on the crystal direction aligned with any specified sample direction as shown below.

Orientation maps showing the crystal directions aligned with the normal, rolling and transverse directions at the surface of a rolled aluminum sheet.

The idea for this map was germinated from a paper I saw presented by David Dingley where a continuous color coding schemed was devised by assigning red, green and blue to the three axes of Rodrigues-Frank space: D. J. Dingley, A. Day, and A. Bewick (1991) “Application of Microtexture Determination using EBSD to Non Cubic Crystals”, Textures and Microstructures, 14-18, 91-96. In this case, the microstructure had been digitized and a single orientation measured for each grain using EBSD. Unfortunately, I only have gray scale images of these results.

SEM micrograph of nickel, grain orientations in Rodrigues-Frank space and orientation map based on color Rodrigues vector coloring scheme. Source: Link labeled “Full-Text PDF” at www.hindawi.com/archive/1991/631843/abs/

IPF map of recrystallized grains in grain oriented silicon steel from Y. Inokuti, C. Maeda and Y. Ito (1987) “Computer color mapping of configuration of goss grains after an intermediate annealing in grain oriented silicon steel.” Transactions of the Iron and Steel Institute of Japan 27, 139-144.
Source: Link labeled “Full Text PDF button’ at www.jstage.jst.go.jp/article/isijinternational1966/27/4/27_4_302/_article

We didn’t realize it at the time; but, an approach based on the crystallographic direction had already been done in Japan. In this work, the stereographic unit triangle (i.e. an inverse pole figure) was used in a continues color coding scheme were red is assigned to the <110> direction, blue to <111> and yellow to <100> and then points lying between these three corners of the stereographic triangle are combinations of these three colors. This color coding was used to shade grains in digitized maps of the microstructure according to their orientation. Y. Inokuti, C. Maeda and Y. Ito (1986) “Observation of Generation of Secondary Nuclei in a Grain Oriented Silicon Steel Sheet Illustrated by Computer Color Mapping”, Journal of the Japan Institute of Metals, 50, 874-8. The images published in this paper received awards in 1986 by the Japanese Institute of Metals and TMS.

AVA map and pole figure from a quartz sample from “Gries am Brenner” in the Austrian alps south of Innsbruck. The pole figure is for the c-axis. (B. Sander (1950) Einführung in die Gefügekunde der Geologischen Körper: Zweiter Teil Die Korngefüge. Springer-Vienna)
Source: In the last chapter (Back Matter) in the Table of Contents there is a link labeled “>> Download PDF” at link.springer.com/book/10.1007%2F978-3-7091-7759-4

I thought these were the first colored orientation maps constructed until Rudy later corrected me (not the first, nor certainly the last time). He sent me some examples of mappings of orientation onto a microstructure by “hatching” or coloring a pole figure and then using those patterns or colors to shade the microstructure as traced from micrographs. H.-R. Wenk (1965) “Gefügestudie an Quarzknauern und -lagen der Tessiner Kulmination”, Schweiz. Mineralogische und Petrographische Mitteilungen, 45, 467-515 and even earlier in B. Sander (1950) Einführung in die Gefügekunde Springer Verlag. 402-409 . Sanders entitled this type of mapping and analysis as AVA (Achsenvertilungsanalyse auf Deutsch or Axis Distribution Analysis in English).

Such maps were forerunners to the “IPF maps” of today (you could actually call them “PF maps”) to which we are so familiar with. It turns out our wanderin’s in A Search for Structure (Cyril Stanley Smith, 1991, MIT Press) have actually not been “aimless” at all but have helped us gain real insight into that etymologically challenged world of microstructure.

How to Increase Your Materials Characterization Knowledge with EDAX

Sue Arnell, Marketing Communications Manager, EDAX

The EDAX Applications and Product Management teams have been very busy offering free ‘continuing education’ workshops in September and October – with a great global response from our partners and customers.

At the end of September, Applications Specialist Shawn Wallace and Electron Backscatter Diffraction (EBSD) Product Manager Matt Nowell joined 6 additional speakers at a ‘Short Lecture Workshop for EBSD’, sponsored by EDAX at the Center for Electron Microscopy and Analysis (CEMAS) at The Ohio State University. The participants attended sessions ranging from ‘EBSD Introduction and Optimization of Collection Parameters for Advanced Application’ to ‘The Dictionary Approach to EBSD: Advances in Highly-Deformed and Fine-Grained Materials’.

Feedback on this workshop included the following comments, “This was a great learning opportunity after working with my lab’s EDAX systems for a couple of months”; “I like the diversity in the public and the talks.  I was very pleased with the overall structure and outcome”; and “Great! Very helpful.”

Matt Nowell presents at the ‘Short Lecture Workshop for EBSD’ at CEMAS, OSU.

In mid-October, EBSD Applications Specialist, Dr. Rene de Kloe traveled to India for a series of workshops on EBSD at the Indian Institute of Science (Bangalore), the International Advanced Research Center (Hyderabad), and the Indian Institute of Technology (Mumbai). Topics discussed at the sessions included:

• Effects of measurement and processing parameters on EBSD
• The application of EBSD to routine material characterization
• Defining resolution in EBSD analysis
• Three Dimensional EBSD analysis – temporal and spatial
• Advanced data averaging tools for improved EDS and EBSD mapping – NPAR™
• Microstructural Imaging using an Electron Backscatter Diffraction Detector – PRIAS™
• Transmission EBSD from low to high resolution

Dr. René de Kloe presents at one of three recent workshops in India.

According to our National Sales Manager in India, Arjun Dalvi, “We conducted this seminar at different sites and I would like to share that the response from all our attendees was very good. They were all eager to get the training from Dr. René and to take part in very interactive Q and A sessions, in which many analysis issues were solved.”

Global Applications Manager Tara Nylese was at the Robert A. Pritzker Science Center in Chicago, IL last week to give a presentation on “Materials Characterization with Microscopy and Microanalysis” for the Illinois Institute of Technology. “In this lecture, we started with a basic introduction to electron microscopy, and then dived deeper into the fundamentals of X-ray microanalysis. We explored both the basics of X-ray excitation, and how to evaluate peaks in an X-ray spectrum. From there, we looked at applied examples such as composition variation in alloys, chemical mapping of components of pharmaceutical tablets, and some fascinating underlying elemental surprises in biological materials.”

Finally, today we have 50 participants at the Geological Museum in Cambridge, MA for a training workshop given by Dr. Jens Rafaelsen and sponsored by Harvard University on “Taking TEAM™ EDS Software to the Next Level” * Presentation topics include:

• Basic operation of the TEAM™ EDS Analysis package
• How to get the most out of TEAM™ EDS Analysis
• Advanced training
• Tips and Tricks using TEAM™ EDS Analysis

Dr. Jens Rafaelsen presents at the Harvard workshop.

Here at EDAX, we are keen to provide our customers, potential customers, and partners with opportunities to improve their knowledge and polish their skills using the techniques, which are central to the EDAX product portfolio.  Our EDS, EBSD, WDS and XRF experts enjoy helping with regular training sessions, webinars, and workshops. If you would like to be included, please check for upcoming webinarsworkshops, and training sessions at www.edax.com.

*A video of these workshop sessions will be available from EDAX in the coming weeks.

A Bit of Background Information

Dr. Jens Rafaelsen, Applications Engineer, EDAX

Any EDS spectrum will have two distinct components; the characteristic peaks that originate from transitions between the states of the atoms in the sample and the background (Bremsstrahlung) which comes from continuum radiation emitted from electrons being slowed down as they move through the sample. The figure below shows a carbon coated galena sample (PbS) where the background is below the dark blue line while the characteristic peaks are above.

Carbon coated galena sample (PbS) where the bacground is below the dark blue line while the characteristic peaks are above.

Some people consider the background an artefact and something to be removed from the spectrum (either through electronics filtering or by subtracting it) but in the TEAM™ software we apply a model based on Kramer’s law that looks as follows:Formulawhere E is the photon energy, N(E) the number of photons, ε(E) the detector efficiency, A(E) the sample self-absorption, E0 the incident beam energy, and a, b, c are fit parameters¹.

This means that the background is tied to the sample composition and detector characteristic and that you can actually use the background shape and fit/misfit as a troubleshooting tool. Often if you have a bad background, it’s because the sample doesn’t meet the model requirements or the data fed to the model is incorrect. The example below shows the galena spectrum where the model has been fed two different tilt conditions and an overshoot of the background can easily be seen with the incorrect 45 degrees tilt. So, if the background is off in the low energy range, it could be an indication that the surface the spectrum came from was tilted, in which case the quant model will lose accuracy (unless it’s fed the correct tilt value).


This of course means that if your background is off, you can easily spend a long time figuring out what went wrong and why, although it often doesn’t matter too much. To get rid of this complexity we have included a different approach in our APEX™ software that is meant for the entry level user. Instead of doing a full model calculation we apply a Statistics-sensitive Non-linear Iterative Peak-clipping (SNIP) routine². This means that you will always get a good background fit though you lose some of the additional information you get from the Bremsstrahlung model. The images below show part of the difference where the full model includes the steps in the background caused by sample self-absorption while the SNIP filter returns a flat background.

So, which one is better? Well, it depends on where the question is coming from. As a scientist, I would always choose a model where the individual components can be addressed individually and if something looks strange, there will be a physical reason for it. But I also understand that a lot of people are not interested in the details and “just want something that works”. Both the Bremsstrahlung model and the SNIP filter will produce good results as shown in the table below that compares the quantification numbers from the galena sample.

Table

While there’s a slight difference between the two models, the variation is well within what is expected based on statistics and especially considering that the sample is a bit oxidized (as can be seen from the oxygen peak in the spectrum). But the complexity of the SNIP background is significantly reduced relative to the full model and there’s no user input, making it the better choice for the novice analyst of infrequent user.

¹ F. Eggert, Microchim Acta 155, 129–136 (2006), DOI 10.1007/s00604-006-0530-0
² C.G. RYAN et al, Nuclear Instruments and Methods in Physics Research 934 (1988) 396-402

What an Eclipse can teach us about our EDS Detectors

Shawn Wallace, Applications Engineer, EDAX

A large portion of the US today saw a real-world teaching moment about something microanalysts think about every day.

Figure 1. Total solar eclipse - image from nasa.gov

Figure 1. Total solar eclipse.                                  Image credit-nasa.gov

With today’s Solar Eclipse, you could see two objects that have the same solid angle in the sky, assuming you are in the path of totality. Which is bigger, the Sun or the Moon? We all know that the Sun is bigger, its radius is nearly 400x that of the moon.

Figure 2. How it works.                                             Image credit – nasa.gov

Luckily for us nerds, it is also 400x further away from the Earth than the moon is. This is what makes the solid angle of both objects the same, so that from the perspective of viewers from the Earth, they take up the same area in the sphere of the sky.

The EDAX team observes the solar eclipse in NJ, without looking at the sun!

Why does all this matter for a microanalyst? We always want to get the most out of our detectors and that means maximizing the solid angle. To maximize it, you really have two parameters to play with: how big the detector is and how close the detector is to the sample. ‘How big is the detector’ is easy to play with. Bigger is better, right? Not always, as the bigger it gets, the more you start running in to challenges with pushing charge around that can lead to issues like incomplete charge collection, ballistic deficits, and other problems that many people never think about.

All these factors tend to lead to lower resolution spectra and worse performance at fast pulse processing times.
What about getting closer? Often, we aim for a take-off angle of 350 and want to ensure that the detector does not protrude below the pole piece to avoid hitting the sample. On different microscopes, this can put severe restrictions on how and where the detector can be mounted and we can end up with the situation where we need to move a large detector further back to make it fit within the constraining parameters. So, getting closer isn’t always an option and sometimes going bigger means moving further back.

Figure 3. Schematic showing different detector sizes with the same solid angle. The detector size can govern the distance from the sample.

In the end, bigger is not always better. When looking at EDS systems, you have to compare the geometry just as much as anything else. The events happening today remind of us that. Sure the Sun is bigger than Moon, but the latter does just as good a job of making a part of the sky dark as the Sun does making it bright.

For more information on optimizing your analysis with EDS and EBSD, see our webinar, ‘Why Microanalysis Performance Matters’.

Celebrating the 50th Birthday of Microanalysis

Sia Afshari, Global Marketing Manager, EDAX

The Microscopy & Microanalysis (M&M) Conference is celebrating 50 years of microanalysis at this year’s meeting in St. Louis next week. There is an entire session (A18.3) dedicated to the 50-year anniversary and the historical background of microanalysis from several different perspectives.

My colleague, Dr. Patrick Camus will be presenting the history of EDAX in his presentation, “More than 50 Years of Influence on Microanalysis” at this session and this is a must see for everyone who is at all interested in the historical development and advances in microanalysis!

Looking back at some of the images in the field of microscopy and seeing how far we have come from static spectrum collection to the standardless quantification of complex materials makes me wonder (in a good way!), about the future and especially about the technical possibilities in microanalysis.

Figure 1. Nuclear Diodes EDAX System Interfaced to Cambridge Stereoscan Scanning Electron Microscope – circa 1968

Pat will be describing the evolution of the company from Nuclear Diodes (1962) through EDAX International (1972) and purchase by Philips (1974) to acquisition by Ametek in 2001. Many accomplished microanalysts have been part of the EDAX team along the journey and have contributed enormously to the technical development of microanalysis. The advancements which have been made to date and those which will continue in the future would have not been possible without the dedication and hard work of all these pioneers in this field.

Figure 2. EDAX Element Silicon Drift Detector on a Scanning Electron Microscope – 2017.

At EDAX, which happens to be older than 50 years, I have been honored to meet some of the pioneers of microanalysis. I extend my gratitude to all those whose work has made it possible for us to enjoy the level of sophistication achieved today and we hope to continue their innovative tradition!

Please click here for more information on EDAX at M&M 2017.