EBSD

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 are keen to help 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.

My Fossil Background

Dr. René de Kloe, Applications Specialist, EDAX

Call me old-fashioned, but when I want to relax I always try to go outdoors, away from computers and electronic gadgets. So when I go on vacation with my family we look for quiet places where we can go hiking and if possible we visit places with interesting rocks that contain fossils. Last summer I spent my summer vacation with my family in the Hunsrück in Germany. The hills close to where we stayed consisted of shales. These are strongly laminated rocks that have been formed by heating and compaction of finegrained sediments, mostly clay, that have been deposited under water in a marine environment. These rocks are perfect for the occurrence of fossils. When an organism dies and falls on such a bed of clay and is covered by a successive stack of mud layers, it can be beautifully preserved. The small grains and airtight seal of the mud can give a very good preservation such that the shape of the plant or animal can be found millions of years later as a highly detailed fossil. Perhaps the most famous occurrence of such fossil-bearing shale is the Burgess shale in British Columbia, Canada which is renowned for the preservation of soft tissue of long-extinct creatures. The Hunsrück region in Germany may not be that spectacular, but it is a lot closer to home for me and here also beautiful fossils have been found.

Figure 1. Crinoid or sea lily fossil found in the  waste heap of the Marienstollen in Weiden, Germany.

Figure 2. Detail of sulphide crystals.

Figure 3. Example of a complete crinoid fossil (not from the Hunsrück area). Source https://commons.wikimedia.org/wiki/File:Fossile-seelilie.jpg

So, when we would go hiking during our stay we just had to pack a hammer in our backpack to see if we would be lucky enough to find something spectacular of our own. What we found were fragments of a sea lily or crinoid embedded in the rock (Figures 1,3) and as is typical for fossils from the area, much of the fossilised remains had been replaced by shiny sulphide crystals (Figure 2). Locally it is said that the sulphides are pyrite. FeS2. So of course, once back home I could not resist putting a small fragment of our find in the SEM to confirm the mineral using EDS and EBSD. The cross section that had broken off the fossil showed smooth fracture surfaces which looked promising for analysis (Figure 4). EDS was easy and quickly showed that the sulphide grains were not iron sulphide, but instead copper bearing chalcopyrite. Getting EBSD results was a bit trickier because although EBSD bands were often visible, shadows cast by the irregular surface confuse the band detection (Figure 5).

Figure 4. Cross section of shale with smooth sulphide grains along the fracture surface.

Figure 5. EBSD patterns collected from the fracture surface. Indexing was done after manual band selection. Surface irregularities are emphasized by the projected shadows.

Now the trick is getting these patterns indexed and here I do like computers doing the work for me. Of course, you can manually indicate the bands and get the orientations of individual patterns, but that will not be very helpful for a map. The problem with a fracture surface is that the substrate has a variable tilt with respect to the EBSD detector. Parts of the sample might be blocking the path to the EBSD detector which complicates the EBSD background processing.

The EDAX EBSD software has many functions to help you out of such tight spots when analyzing challenging samples. For example, in addition to the standard background subtraction that is applied to routine EBSD mapping there is a library of background processing routines available. These routines can be helpful if your specimen is not a “typical” flat, well-polished EBSD sample. This library allows you to create your own recipe of image processing routines to optimize the band detection on patterns with deviating intensity gradients or incomplete patterns due to shadowing.

The standard background polishing uses an averaged EBSD pattern of more than ~25 grains such that the individual bands are blended out. This produces a fixed intensity gradient that we use to remove the background from all the patterns in the analysis area. When the actual intensity gradient shifts due to surface irregularities it is not enough to just use such a fixed average background. In that case you will need to add a dynamic background calculation method to smooth out the resulting intensity variations.

This is illustrated in the EBSD mapping of the fossil in Figure 6. The first EBSD mapping of the fossil using standard background subtraction only showed those parts of the grains that happened to be close to the optimal orientation for normal EBSD. When the surface was pointing in another direction, the pattern intensity had shifted too much for successful indexing. Reindexing the map with optimised background processing tripled the indexable area on the fracture surface.

Figure 6. Analysis of the fracture surface in the fossil. -1- PRIAS center image showing the smooth sulphide grains, -2- Superimposed EDS maps of O(green), Al(blue), S(magenta), and Fe(orange) -3- EBSD IPF on IQ maps with standard background processing, -4- original IPF map, -5- EBSD IPF on IQ maps with optimized background processing, -6- IPF map with optimized background.

In addition to the pattern enhancements also the band detection itself can be tuned to look at specific areas of the patterns. Surface shadowing mainly obscures the bottom part of the pattern, so when you shift the focus of the band detection to the upper half of the pattern you can maximize the number of detected bands and minimize the disturbing effects of the edges of the shadowed area. It is unavoidable to pick up a false band or two when you have a shadow, but when there are still 7-9 correct bands detected as well, indexing is not a problem.

Figure 7. Band detection on shadowed EBSD pattern. Band detection in the Hough transform is focused at the upper half of the pattern to allow detection of sufficient number of bands for correct indexing.

In the images below are a few suggestions of background processing recipes that can be useful for a variety of applications.

Of course, you can also create your own recipe of image processing options such that perhaps you will be able to extract some previously unrecognized details from your materials.

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’.

EDAX China User Meeting in Guiyang 贵阳用户会流水帐

Dr. Sophie Yan, Applications Engineer China, EDAX

EDAX China User Meeting, Guiyang.

EDAX China User Meeting, Guiyang.

EDAX held a China user meeting in Guiyang, Guizhou province in July 2017. We had a wonderful time with over 100 customers and colleagues. The User Meeting was very interesting; the weather is cool in summer; and the activities after the meeting were great fun.. I have several pictures to show the different moments…
Generally, Guiyang is not very popular with Chinese people. In Shanghai, there are luxuries in Huaihai Road and crowds in Nanjing Road; in Beijing, you find the solemn Tiananmen Square and desolate The Great Wall, but in Guiyang, I just had an impression of a poverty-stricken mountain area. Then I met a friend from Guiyang, she also talked about poverty and the mountain area, but she was much more enthusiastic about the region. She said it was warm in winter and cool in summer; she said the mountain and water were so nice. She was a stylish girl, living an exquisite life; but she always wished she could go back to hometown earlier. From then on, Guiyang became a kind of mystery in my mind.
其实我对贵阳思慕已久。
上海上海,是淮海路的名牌南京路的热闹;北京北京,是天安门的庄严长城的苍凉。贵阳,有什么?大山的贫瘠与封闭?直到当年,我碰到一位朋友,来自贵阳。她也说起大山及贫穷,但是她的话里,那里冬暖夏凉,水暖山温。那位朋友,思想前卫,生活精致,心心念念的,却是早日回家。至此,贵阳,在我心里是颇为神秘的所在。
After so many years, when I arrived in Guiyang, the feeling of mystery and novelty disappeared. The airport looks great and the billboard is modern and impressive. It was no different from other places, except that it’s 10 degrees cooler than Shanghai. I shared this image in ‘wechat’ moments, then got a lot of ’likes’.
一念多年。当踏上这个城市的土地,我所以为的一切,新奇,神秘,通通颠覆。这里的机场不小,广告牌也一派摩登气派。和我去过的地方并无多大不同。除了,比起火炉一般的江浙沪低了十度,发在微信朋友圈,引起一片哀号。看看这一张截图,就拉了多少仇恨。

During the conference our VP Mark Grey came and delivered a corporate introduction. Nan Lin from Singapore and local applications showed new product information: EDS, EBSD, XRF, etc.
开会中……VP Mark过来作公司简介,新加坡的林楠以及国内的应用分别作产品介绍……EDS,EBSD,XRF,嗯,分工明确。

Invited speakers shared their research work in the afternoon. Each one generated lively discussion. The EDAX user meeting is not only an opportunity to show EDAX products, it is also a platform for users’ to communicate with each other and discuss current challenges in microanalysis.
下午各位嘉宾给大家作邀请报告……每个报告都引起了热烈的反应,讨论得不亦乐乎……EDAX的用户会不单是一个产品展示的环节,更是一个用户交流的平台……

Speakers at the China User Meeting 2017

Speakers at the China User Meeting 2017

Imagine the scenery outside. The weather forecast showed 29 degree(Celsius), but it was cool actually. Green trees and a humid atmosphere made the sultry summer go away.
开会中间例行出来拍照,当时天气预报29度,但是风吹得非常凉爽。分明才是初夏的温度,凉风习习的感觉。加上四周绿树葱茏,空气中的润泽气息,盛夏的酷热,早已远离。

 
The hotel located beside Guanshanhu Park, which was gorgeous.
酒店在观山湖公园旁边,风景如画(图片来自百度,笔者拍照无能……)
No one was in this corner of the park. Red flowers were quietly in bloom.
傍晚的公园角落寂寂无人,一丛红花在碎石小径上静静盛开。

We went to Huangguoshu waterfall! The white waterfall poured down. I felt the vapor and steam: it was amazing.
当然这次贵阳之行的精妙处不止于此……还有我最为盼望的——黄果树瀑布!如匹练的白色倾泻直下,瀑布脚下水汽氤氲,在近处感受那赫赫声势,大自然的鬼斧神工,实非人力所能及。
Just behind the hill, the water from the waterfall formed a lake, gentle and quiet.
瀑布积水成湖,湖水温柔静谧。水的另一面。

We also experienced the different culture of the local ethnic minority. Terraced fields, bamboo buildings,songs and dance from local people. Attractive.
我们还顺便见识了少数民族的多样文化。梯田,依山而建的竹楼,以及多姿多彩的歌舞。不虚此行。

Finally, we are looking forward to the next user meeting in China!
流水帐完结处,唯愿年年有今日,岁岁有今朝!

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.

Aimless Wanderin’ in 3D (Part 3)

Dr. Stuart Wright, Senior Scientist, EDAX

In my research on the origins of the term texture to describe preferred lattice orientation I spent some time looking at one of the classic texts on the subject: Bunge’s “red bible” as we called it in our research group in grad school – Texture Analysis in Materials Science Mathematical Methods (1969). As I was reading I found an interesting passage as it relates to where we are with EBSD today:

“In a polycrystalline material crystallites of different shape, size and orientation are generally present. It can thus also occur that regions of different orientation are not separated from one another by unequivocally defined grain boundaries, but that, on the contrary, the orientation changes continuously from one point to another. If one desires to completely describe the crystal orientation of a polycrystalline material, one must specify the relevant orientation g for each point with coordinates x, y, z within the sample:

g=g(x,y,z)           (3.1)

If one writes g in EULER’s angles, this mean explicitly

φ_1=φ_1 (x,y,z);  Φ=Φ(x,y,z);  φ_2=φ_2 (x,y,z);           (3.2)

One thus requires three functions, each of these variables, which are also discontinuous at grain boundaries. Such a representation of the crystal orientation is very complicated. Where therefore observe that it has as yet been experimentally determined in only a very few cases (see, for example, references 139-141, 200-203), and that its mathematical treatment is so difficult that it is not practically applicable.”

I don’t quote these lines to detract in any way from the legacy of Professor Bunge in the field of texture analysis. I did not know Professor Bunge well but in all my interactions with him he was always very patient with my questions and generous with his time. Professor Bunge readily embraced new technology as it advanced texture analysis forward including automated EBSD. I quote this passage to show that the ideas behind what we might today call 3D texture analysis were germinated very early on. The work on Orientation Coherence by Brent Adams I quoted in Part 2 of this series was one of the first to mathematically build on these ideas. Now with serial sectioning via the FIB or other means coupled with EBSD as well as high-energy x-ray diffraction it is possible to realize the experimental side of these ideas in a, perhaps not routine but certainly, tractable manner.

A schematic of the evolution from pole figure-based ODF analysis to EBSD-based orientation maps to 3D texture data.

Others have anticipated these advancements as well. In chapter 2 of Rudy Wenk’s 1985 book entitled Preferred Orientation in Deformed Metal and Rocks: An introduction to Modern Texture Analysis it states:

“Pole figures and fabric diagrams provide information only about the orientation of crystals. It may be desirable to know the relation between the spatial distribution of grains and grain shape with respect to crystallographic orientation. Orientation relations between neighboring grains further defined the fabric and help to elucidate its significance.”

But let us return to the theme of aimless wanderin’s in texture terminology. The title for Chapter 4 of Bunge’s book is “Expansion of Orientation Distribution Functions in Series of Generalized Spherical Harmonics”. This chapter describes a solution the determination of the three-dimensional ODF (orientation distribution function) from two-dimensional pole figures. The chapter has a sub-title “Three-Dimensional Textures”. The three dimensions in this chapter of Bunge’s book are in orientation space (the three Euler Angles). What we call today a 3D texture is actually a 6D description with three dimensions in orientation space and three spatial dimensions (e.g. x, y and z). And those working with High-Energy x-rays have also characterized spatially resolved orientation distributions for in-situ experiments thus adding a seventh dimension of time, temperature, strain, …

It is nice to know in the nearly 50 years since Bunge’s book was published that what can sometimes appear to be aimless wanderin’s with mixed up terminology has actually lead us to higher dimensions of understanding. But, before we take too much credit for these advances in the “metallurgical arts”, as it says on the Google Scholar home page we “stand on the shoulders of giants” who envisioned and laid the groundwork for these advances.

Journey of Learning: Teaching Yourself the Power of EBSD

Shawn Wallace – Applications Engineer, EDAX

The joy of learning is sadly something that many people forget about and some never really feel. One of the things I like to keep in mind when I am learning something new is that learning is usually not a eureka moment, but a process of combining concepts and ideas already known, to reach a new solution or idea. The reason I was thinking about learning as a process is because recently I found myself forgetting that. A customer sample came in that was, for EBSD, hard in every way: Difficult crystal system/orientation, sample prep issues, poor diffractor. With all those factors, the sample was putting up a fight and winning, mainly because I allowed it to. I had tried all my normal tricks and was not making much headway. I knew the sample was analyzable, but I was not treating the process as a personal learning opportunity, instead I was treating it as a fight that I had to win. I was quickly bouncing from potential solution to potential solution and trying them, without spending much time on thinking what would be best to try and how to tackle the problem as a problem, and not a challenge. I didn’t even frame it that way in my own head until a week later when I was visiting a customer site to do some training.

During the training session, a sample came up with a very different set of problems, but still ones that were stymieing us as we sat at the microscope. I found the user resorting to what I had done previously; just try this and see if it works, without thinking about what the best course of action was. As I sat there, I told them to take a step back and evaluate what the issue was and how we could use our knowledge of all the functions available to us in the TEAM™ software and/or our microscope to find a solution. We sat and talked about the issue and the user was able to come up with a game plan and try some things that would help him reach a solution or gain additional knowledge, aka LEARN. I learned that day – that I sometimes need to treat myself the way I would treat a user. There will always be cases when I don’t know the answer and I have to teach myself the solution.

That leads us to an open question. How do you learn EBSD as you go along? With that in mind, here at EDAX we are going to start a new series of blog posts to discuss the basics of EBSD, from pattern formation, the Hough Transform, and finally indexing. More importantly, I hope to touch on how to troubleshoot issues using your newfound understanding of these concepts and tie the entire processes together as they all play off each other.

My final goal is get your creative juices flowing to dive deeper into understanding the kind of questions that EBSD can answer, and how that, in the end, can provide you with an incredible understanding of your analysis challenges and ultimately a solution to the problem. EBSD is one of the most powerful analytical techniques that I know. It can answer the simple questions (what phase is my sample?) to the incredibly complex (if I squeeze my sample this way, which grains will tend to deform first?). As your knowledge grows, EBSD is one step ahead of you, egging you on to learn more and more. I hope to be your guide on this Journey of Learning. I think I will learn quite a bit too.