Author: edaxblog

Be Direct When You Detect!

Fred Ulmer, South East Regional Sales Manager, EDAX/Gatan

Roughly 10 years ago, I was introduced to the exciting world of research using Transmission Electron Microscope (TEM)/Scanning Electron Microscope (SEM) principles. Working first as a Gatan field service engineer, then service manager. It was my first crash course in these research principles. It was a lot to take in at the time, but the excitement and enthusiasm shown by a customer when they have their new piece of equipment installed and begin to generate data was such a payoff. It seems like every year that there is a new, exciting technique or technology to apply to user’s research that enables researchers to keep getting better data.

Recently AMETEK purchased Gatan, which allowed for a great partnership between already owned EDAX and newly acquired Gatan. Also, I switched to sales from service at this time, becoming the South East Sales Manager with Gatan, and shortly after, I became the EDAX South East Sales Manager. Again, a lot to take in at the time, but it was rest assuring that EDAX, like Gatan, is at the forefront of TEM/SEM research.

One of the most technological advances I witnessed was the introduction of the K2 & K3 direct detection cameras for TEM from Gatan. This technology has allowed users to achieve data that was previously unheard of. From cryo-techniques to direct detection Electron Energy Loss Spectroscopy (EELS), these systems have become a game-changer.

Breakthrough K3 result: 2.7 Å structure of the 20S Proteasome with the K3 camera and Elsa cryo-holder on a TF20. Data courtesy of Alexander Myasnikov, Michael Braunfeld, Yifan Cheng, and David Agard.

Figure 1. Breakthrough K3 result: 2.7 Å structure of the 20S Proteasome with the K3 camera and Elsa cryo-holder on a TF20. Data courtesy of Alexander Myasnikov, Michael Braunfeld, Yifan Cheng, and David Agard.

Unsure of how, or even if direct detection could be used in the SEM world, it was exciting to get word from EDAX that they were releasing a direct detection EBSD analysis system called the Clarity™. This system is the world’s first EBSD detector based on direct detection technology. Current EBSD non-direct detection detectors have some drawbacks that include grain size and film thickness, causing localized blooming and some imaging artifacts in the EBSD patterns. So how does the Clarity overcome these drawbacks? It comes from the inherent design and technology of the detector. The Clarity does not require a phosphor screen or light transfer system. The technology uses a CMOS detector coupled to a silicon sensor. The incident electrons generate several electron-hole pairs within the silicon upon impact, and a bias voltage moves the charge toward the underlying CMOS detector, where it counts each event. This method is so sensitive that it can detect individual electrons. Coupled with zero read noise, the Clarity provides unprecedented performance for EBSD pattern collection. It can successfully detect and analyze patterns comprised of less than 10 electrons per pixel.

High-quality EBSD patterns collected with Clarity from a) silicon, b) olivine, and c) quartz.

Figure 2. High-quality EBSD patterns collected with Clarity from a) silicon, b) olivine, and c) quartz.

Intensity profile across (113) band from the Hikari Super (blue) and Clarity (red) detectors showing improved contrast and sharpness with direct detection.

Figure 3. Intensity profile across (113) band from the Hikari Super (blue) and Clarity (red) detectors showing improved contrast and sharpness with direct detection.

Direct detection will benefit many research areas like in‐situ microscopy, EBSD, 4D STEM, imaging beam sensitive materials, quantitative measurement of radiation damage, or quantitative electron microscopy. I am excited to see how the new generation of direct detection, like the EDAX Clarity, will continue to revolutionize the field of electron microscopy. Direct detection and electron counting are poised to advance electron microscopy into a new era. Let’s go direct detect!

EDAX Clarity EBSD Analysis System.

Figure 4. EDAX Clarity EBSD Analysis System.

Cover Worthy

Matt Nowell, EBSD Product Manager, EDAX

I firmly believe that one of the factors that has helped EBSD advance as a microanalytical technique is that it makes beautiful pictures. Of course, these images are packed with valuable information regarding the microstructure of materials. But in addition to this scientific content, they catch your eye. In our lab, we have taken advantage of this by hanging the covers of different journals and publications that feature EBSD images collected with EDAX equipment (Figure 1). Some of these are images we have collected internally, and others are from our customers. It is a fun reminder of interesting work that has been done over the years.

Our EBSD cover collection.

Figure 1. Our EBSD cover collection.

We have had an exciting past 18 months with the EBSD product line at EDAX. We launched our Velocity™ high-speed CMOS camera, which delivers greater than 4,500 indexed points per second. We released the APEX™ Software for EBSD, our new data collection platform with powerful analytical capability coupled with an easy-to-use interface. We introduced our groundbreaking Clarity™ EBSD Analysis System, which is the first commercial direct detection system designed for EBSD. As part of the development, testing, and marketing of these new products, I have used these products to collect thousands of images, some of which are utilized to highlight the performance of these new tools.

So how do you choose what makes a good EBSD image? The first step is often picking an interesting sample, but interesting is in the eye of the beholder. Some examples are selected because they use specific materials, like aluminum, magnesium, or steel. I like samples that have interesting microstructures. Sometimes, this is from a novel processing approach, like friction stir welding or equal channel angular processing. Sometimes, it is from a multi-phase microstructure, where structure and chemistry can be characterized simultaneously with EDS-EBSD. Sometimes, it is application focused. In this example, I have selected a sample because it is an additively manufactured nickel alloy. Additive manufacturing is a market with growing interest, and the microstructure is important because it influences the final properties of the material.

Figure 2 shows an Inverse Pole Figure (IPF) map of this material, collected with the Velocity Super at >4,500 indexed points per second. This IPF map is colored relative to the surface normal direction, and I have included a (001) pole figure to show the crystallographic texture and a colored IPF key to help decipher the relationship between the colors and the crystal orientations, which is good practice. This image is interesting because it shows a (001) fiber texture, which explains why many of the grains are shaded red. This helps researchers understand how these grains were growing during the additive manufacturing process. But is it visually appealing? That’s a question I often ask as I share these images for different possible uses.

IPF Map of an additively manufactured nickel alloy collected with the Velocity Super at >4,500 indexed points per second.

Figure 2. IPF Map of an additively manufactured nickel alloy collected with the Velocity Super at >4,500 indexed points per second.

One possible approach to improving the visual appeal of this map is to superimpose it with a grayscale image derived from other EBSD measurement metrics. Figure 3 shows the same IPF map combined with an Image Quality (IQ) map and a PRIAS™ (center) map. The IQ value is derived from measuring the brightness and sharpness of the diffraction bands within the EBSD patterns. The PRIAS map is calculated from the intensity of the signal onto an ROI positioned within the center of the EBSD detector. Both signals show microstructural contrast and add supplemental information to the IPF map.

IPF map combined with Image Quality (left) and PRIAS center (right) contrasts.

Figure 3. IPF map combined with Image Quality (left) and PRIAS center (right) contrasts.

How about the colors, though? Is it too red? I hear that sometimes, but I wonder if it is because of the rivalry between the University of Utah (red – where I went to school) and Brigham Young University (blue – where some of my co-workers went to school). What can I do about this? One approach is to specify the IPF map relative to a different direction than the surface normal direction. Figure 4 shows an IPF map where I have selected a [111] sample vector. While it is harder to relate this to the fundamental additive manufacturing process, it does show how you are not limited to specific sample directions. This can be useful if, for example, the thermal gradient present during processing it not aligned with the sample normal direction. In this case, it gives us a different color distribution representing the same microstructure. Is this better?

IPF map relative to the [111] sample direction.

Figure 4. IPF map relative to the [111] sample direction.

I have been looking at these maps for 25+ years now, so sometimes it is the new and novel that catches my eye. Figure 5 shows the same microstructure colored using a Quaternion Misorientation scheme. Here a reference orientation is used as a baseline, and the misorientation from this reference is used for coloring. Our OIM Analysis™ software has a wide range of different methods for visualizing microstructures. I personally really like the way this one looks. It is as much art as science.

IPF map with Quaternion Misorientation coloring.

Figure 5. IPF map with Quaternion Misorientation coloring.

When images meet those aesthetic criteria, they can be used for marketing, publications, covers, and even clothing. Figure 6 shows a scarf printed using an IPF from a skutterudite material. The crystallization of this material looks a bit like exploding fireworks. I have heard plenty of times that we should be in the tie or T-shirt business with the array of stunning images we can produce. I am always amazed that beyond visual appearance, the information on orientation, grain size and shape, deformation, and phase, among other things, that can be easily represented with EBSD. I hope to continue to find interesting examples to share with you. Special thanks to Tara Nylese for sharing the photo.

EBSD scarf/dog warmer.

Figure 6. EBSD scarf/dog warmer.

The Only Constant is Change

Matt Chipman, Senior Regional Sales Manager, EDAX

The seasons are changing here in the mountains of Utah. Autumn is at least one of my four favorites! I have made my home here, largely because of the drastic seasonal changes in climate and the ability to participate in gravity fed activities, like skiing and mountain biking. My personal life has become a game of maximizing my time in the mountains within the confines of what the weather and other commitments allow. Do I ride my bike at 5,000 feet elevation or 9,000 feet elevation? Do I pull out the skis or the fat tire bike for riding on the snow? Do I have to ride early in the morning when the ground is frozen to avoid the mud? Maybe I just escape to the desert for a weekend. No matter what the weather decides to throw at me, I have an answer. If I ever get bored, then mother nature will change things up for me soon enough. I have learned to adapt and enjoy the constant change.

A perfect autumn day on the trail.

Figure 1. A perfect autumn day on the trail.

Escaping to the desert. Maybe I will see Dr. Stuart Wright there.

Figure 2. Escaping to the desert. Maybe I will see Dr. Stuart Wright there.

 Not enough powder for skiing? No problem.

Figure 3. Not enough powder for skiing? No problem.

Recently in my professional life, I have had to apply some of the same attitudes toward change. After spending my entire career with TSL, then EDAX, then AMETEK; I decided to leave and work for Gatan about five years ago. I was just shy of my 20-year anniversary with EDAX. It was a nice change of pace and scenery. I really enjoyed learning new products and getting in touch with cutting edge Transmission Electron Microscope (TEM) research applications that Gatan is involved with. Then the climate changed and AMETEK acquired Gatan! Things had come full circle, just like the seasons. Fortunately for me, selling EDS and EBSD is like riding a bike (pun intended)! I now get to associate with some old friends again and sell both Gatan and EDAX products. I’m trying to convince myself that there are never too many products to sell, just like you can never have too much snow. However, sometimes I wish there was more time in the day.

It’s impossible to have too much snow!

Figure 4. It’s impossible to have too much snow!

I am looking forward to the constant change that will come with the combined power of EDAX and Gatan products. Can we offer Gatan sample preparation equipment to EDAX Scanning Electron Microscope (SEM) users? We sure can! Check out the latest EDAX Insight newsletter to see an example. Can we offer heating stages to EDAX SEM users? Absolutely! Can we leverage the power of Electron Energy Loss Spectroscopy (EELS) and Energy Dispersive Spectroscopy (EDS) together with diffraction for the ultimate microanalysis experience for TEM users? I hope so! It will take some work, but like climbing mountains, it will be so worth it!

You can’t enjoy the descent without the hard work of climbing.

Figure 5. You can’t enjoy the descent without the hard work of climbing.

I am looking forward to being able to offer my customers more solutions to their research problems. No matter which way the wind blows; I expect to have the answer in the form of the combined EDAX and Gatan product portfolio. What research problems are you trying to solve? Let’s see what we can do together. See you out there!

If you are interested in talking with a representative about how EDAX and Gatan products can help you, please contact us.

There is a Screw Loose

Dr. René de Kloe, Applications Specialist, EDAX

I dare say that in everyday life, most people do not think about crystallography very often. Equally, when we think of grains, a familiar image that comes to mind is children playing on the beach, building sandcastles (or in good Dutch tradition, perhaps a dam to keep the sea out).

Children already know about building things. They know you must use moist sand to make nice figurines. They also know that when you dig too deep on the beach, that water may come in and wreck your castle. You have to know your stuff when you start building things. Parents stimulate these construction experiments by supplying the building materials for some serious out-of-the-box thinking. The children start small, developing new, and intriguing concept cars (Figure 1), and then move on to bigger ideas and perhaps they build robots (Figure 2).

A concept car made of Duplo blocks.

Figure1. A concept car made of Duplo blocks.

Robots made from carton boxes.

Figure 2. Robots made from carton boxes.

Why should this stop when you grow up? Some people might say there is a screw loose inside if you occupy yourself with carton robots (I designed the robots for a children’s vacation camp 😊). Still, the fascination with building beautiful things remains at all ages. A while ago, my neighbor asked me to take a look at this impressive tower built of Anker stones without using any glue (Figure 3, https://anchor-stone.eurosourcellc.com/).

An Anker stone model of the Grunewaldturm in Berlin.

Figure 3. An Anker stone model of the Grunewaldturm in Berlin.

Engineers have never outgrown the desire to put bits together to build things, and with the knowledge they gained during their education and experience, amazing things have been created. But as with the Anker tower, to have a stable structure, you need to keep paying attention to detail. If you have ever built anything yourself, you know how important it is to use the right components and ensure that all the parts fit together.

During my work at EDAX, I often work with engineers who are creating and testing new materials. Such materials are typically being deliberately developed for certain purposes by mixing components and then treating them just so, but sometimes also found by accident. And of course, it is not only the composition of a material that defines its properties, it is also the microstructure that makes a material suitable for specific applications. When you take care to pick the proper starting material for your product, you can successfully build something. However, sometimes corners are cut, and things go wrong.

For example, take a look at the two montage EBSD maps of iron screws in Figure 4.

An EBSD IPF (Y) on image quality maps of a) a coarse grained screw and b) a fine-grained screw. All the green grains are aligned with one of the edges of the unit-cell cube facing towards the tip of the screw.

Figure 4. An EBSD IPF (Y) on image quality maps of a) a coarse grained screw and b) a fine-grained screw. All the green grains are aligned with one of the edges of the unit-cell cube facing towards the tip of the screw.

These are two multi-million-point EBSD maps showing the microstructure in two screws. The greenish color indicates that in both screws the crystallographic [011] direction lies along the length of the screw. This is indicative of the production process of the metal rods from which the screws are cut. The different purple colors in the head are caused by the stamp that shapes it and pushes the cross into the top of the screw. But that is where the similarities end.

The top screw shows a very coarse grain structure, while the bottom screw has a much finer interconnected grain structure. This difference in grain structure has consequences. When we zoom in on the shaft of the coarse-grained screw (Figure 5a), the large grains appear flattened in between the threads, and there is a strong change in grain size from the center to the edge of the shaft. In between the threads, some of these larger grains have even been forced apart to form cracks. This combination is bad news for the strength of the screw. When you tighten this screw, the force gets “focused” on the weak areas between the threads, and the screw breaks easily. In the fine-grained screw (Figure 5b), a minor grain size reduction is visible right at the edge of the shaft, but the internal structure is constant over the entire screw. This homogeneous structure distributes the force evenly over the screw, and it does not break easily.

Grain maps of the two screws shown at the same scale illustrating the difference in grain size. a) Shows a coarse-grained microstructure and b) depicts a fine-grained microstructure.

Figure 5. Grain maps of the two screws shown at the same scale illustrating the difference in grain size. a) Shows a coarse-grained microstructure and b) depicts a fine-grained microstructure.

A final detail scan of the grain structure shows an additional difference (Figure 6). In the coarse-grained screw, long trails of carbide particles can be observed in between the grains, which effectively separate the grains and facilitate cracking. In the fine-grained screw, the grains show a lamellar martensitic microstructure with very few carbides. These microstructures exacerbate the difference in strength between the screws.

Detail maps of the grain structure in a) the weak and b) the strong screw.

Figure 6. Detail maps of the grain structure in a) the weak and b) the strong screw.

The investigation example shown above was born out of frustration when I tried to build something, and the screws just kept breaking while I thought I was doing nothing wrong. So, I decided to cut up one of the failing screws and compare it with a screw from another box that had never given me trouble.

This was just about a screw used in a DIY project to put a wooden panel to a wall. Nothing crucial, you would think. But just imagine when this screw would have been used to hold up something a bit more impressive, like that big, heavy chandelier 10 meters above your head in the lobby of a hotel? Then suddenly, the microstructure of a humble construction component, such as a screw, becomes crucial, and thinking about the crystallography and grain structure of everyday items turns out to be really important.

Care and Upkeep of Your Standards

Shawn Wallace, Applications Engineer, EDAX

As I prepared for some analytical work yesterday, I had to repolish a standard block. This made me think about how important these little blocks are and how often they are not cared for properly. With that in mind, I thought it might be useful to pass on some little nuggets of information I have gathered over the years from many sources.

The most important thing about caring for a block is knowing what is in it. Standard blocks can be purchased as a whole or personally made. No matter what, you need to know what you have! To do so, you should keep several copies of the following for every standard you have:

  • Optical light images of the whole block
  • SEM Montage image of the whole block (BSE and SE)
  • Individual image of each standard material
  • Composition of each standard material with sources
  • Notes on each standard

Each of our standard blocks has a name and a duplicate document. This packet has optical, BSE, and SE images of the standard. This allows us to quickly find the standard we want while having all the information easily accessible in hand.

Figure 1. Each of our standard blocks has a name and a duplicate document. This packet has optical, BSE, and SE images of the standard. This allows us to quickly find the standard we want while having all the information easily accessible in hand.

Each of these above items is important. You want to keep both a visual record of your standards, a record of what it is and the condition that it is in, to allow you to track any issues that may pop up (Figure 1). Therefore, having a note section is important. You may find that one of the areas of your standard gives anomalous values and should be avoided. You want to make sure this information is easily accessible to everyone that uses the standard. I suggest scanning and keeping electronic copies in a shared folder on your desktop.

Besides the documentation aspect of care, physical care is just as critical. Most commercial standard blocks come pre-polished and carbon-coated. Over time, both of those will degrade and need to be redone. Usually, the carbon coating damages first, but you also need to check for burn marks and other beam damage done to the standard material itself. When repolishing and recoating, I usually do a solid 10 minute repolish with diamond paste. This removes enough material to eliminate the carbon coating and get new clean, undamaged surfaces while not change the physical appearance all that much. I try my best to avoid using an Al-based polishing material, as they tend to stick around too much and can interfere with my analysis on elements I use. With carbon-based polishing material, it is much easier to see the effects of the carbon. In the end, I do not tend to do quant work on carbon that much, while I often try to quantify aluminum. Whatever you do, document what was done. It can help you both head off and understand issues that may present.

While physically handling your sample, it shouldn’t need to be said, but you should never be touching your sample with ungloved hands. Your oils are bad for both the SEM cleanliness and the sample cleanliness. Avoid any sort of colloidal products with standards, as they do tend to flake with age. When not in use, samples should be held in a desiccator with good desiccant (Figure 3).

A good desiccator should have a rubber molding to help it hold a seal at a minimum. You should try to keep it under vacuum for the best results. While taking this picture, I noticed I should dry my desiccant or replace it. I have seen some users keep a small plastic bag of fresh desiccant in the desiccator as a quick visual reference.

Figure 3. A good desiccator should have a rubber molding to help it hold a seal at a minimum. You should try to keep it under vacuum for the best results. While taking this picture, I noticed I should dry my desiccant or replace it. I have seen some users keep a small plastic bag of fresh desiccant in the desiccator as a quick visual reference.

There are many other tips I can think of sharing, but to wrap it up, standards are valuable in our industry. A good, well cared for standard will last multiple careers while giving consistent results time after time. Take the time to keep your standards in the best condition, and they will repay your time spent on them tenfold.

Cornfields and Characterization: A Story of Failure Analysis

Dr. Jordan Moering, U.S. Eastern Sales Manager, EDAX

It was an icy morning in early November where I found myself, freezing, staring at a chunk of mangled aluminum, carbon fiber, and hickory nestled against mounds of pumpkins in a largely empty cornfield in Sussex County, Delaware. As the sun began to rise over the frosty ground, the carnal wreckage was investigated, pondered over, poked and prodded, touched, and engaged in any other means of characterization at the disposal of the rag-tag cohort of farmers, engineers, enthusiasts, and politicians surrounding me. In hindsight, this scenario seems like something out of a science fiction novel or perhaps a post-apocalyptic memoir, but I can assure you that this is a common sight to behold. Common, at least, at the World Championship Punkin Chunkin.

As it turns out, the twisted composite beam was one of the first instances I experienced in witnessing true engineering failure firsthand. Although the beam failed in some of our early testing, it had previously been attached to a world-class, 7-ton, torsion catapult capable of launching pumpkins over a kilometer at nearly the speed of sound. It could withstand tensile loads exceeding the weight of a Boeing 747 and extended nearly 20 feet in length. All of that impressive performance was a thing of the past as I closely examined the jagged features at the fracture surface, the twists along the flanges of the I-beam, and the shards of carbon fiber shattered amongst the corn husks.

Replacing the broken "Throwing Arm" with a convenient spare that we had brought with us.

Figure 1. Replacing the broken “Throwing Arm” with a convenient spare that we had brought with us.

Although I was just a student at the time, I already recognized the characteristic ductile fracture surface before me. I might have squinted my eyes and imagined some fatigue striations within the metal surface, but sadly this was the only means at my disposal of diagnosing the problem at the time. In a laboratory setting, I would have been able to not only characterize the elemental composition of the beam (it was a gift from a benevolent team sponsor) but also fully describe the crystalline structure with techniques like EBSD, XRD, and EDS. This type of material identification study is routine with modern analytical instruments, but recent advancements have taken this a step further. Had I known then what I know now, the unprecedented capabilities of high-resolution EBSD and ultra-high sensitivity of direct detection could have allowed me to understand and quantify, quite literally, the stressed state of the surrounding metal at the fracture surface.

The most frequently used deconstruction and characterization device we had at our disposal - an angle grinder.

Figure 2. The most frequently used deconstruction and characterization device we had at our disposal – an angle grinder.

While my first foire into failure analysis lacked the sophistication of modern analytical capabilities, it did spark an intense curiosity into this critical line of work. The modern electron microscopist, lab technician, or researcher has a wealth of opportunity at his/her disposal for understanding how materials fail. Sometimes these failures originate at some inclusion or material defect that could have previously been detected by methods like micro-XRF or EDS elemental analysis. Other times, inherent weaknesses in the system concentrate stress in ways that might not be apparent to the naked eye. Techniques like high-resolution EBSD and X-ray diffraction might be used to prevent these calamities. The list goes on and on.

I’ve only been working at EDAX for several months now, but every day I wake up and get to work with individuals who face scenarios, not unlike my previous encounter with twisted beams and flying pumpkins. Although a researcher at semiconductor foundry might not be surrounded by farmers in the middle of a cornfield, they certainly may find themselves staring at an improperly functioning device, wondering where things went wrong. In this capacity and many others, I find myself relating to our customers. I empathize with their challenges, and I am excited to help them uncover solutions to some problems that they previously were not aware of.

Because if there is one thing I have learned from Punkin Chunkin and Advanced EM Characterization, it is that you never know what you will find under the surface of your material.

The video below is of the beam in operation prior to its demise: https://www.youtube.com/watch?v=aYKGaLq3xPM.

Sunshine of My Life

Lin Nan, Regional Sales Manager, EDAX

EDAX is in a scientific business, exploring the unknown by looking at small materials. As EDAX employees, this makes us proud because we know that small things matter and our products and services help people discover scientific breakthroughs that make the world a better place.

But even for people like us, at least it never occurred to me, that a small virus, just nanometers in size, can change our lives so significantly. It reflects how little we know and how insignificant we are compared to the massive nature of the unknown. Science and human civilization still have a long way to go. We should remain respectful and humble about the world and nature.

COVID-19 has changed our lives in a way that no one expected, and maybe no one ever wanted with suffering and loss of life. Furthermore, the impact on our perception of society and the world may have been changed forever.

For the past six years at EDAX, like lots of our colleagues, I have always performed the majority of my job on the road. In my position as a Sales Manager, I promote and manage EDAX business and help our customers explore unknowns in small scale samples, hoping that it contributes to science. Airports, hotel breakfast, and complaints from my wife have become routine to me. Luckily, with “known” science and technology, the FaceTime and video calls do make it much easier for me to stay connected with my family while I’m traveling.

But for the past six months, my routine has changed completely. I have been sitting still within my apartment, like most people around the world. Ironically, instead of using video calls to connect with my family, I am now using video conferences and other internet resources to conduct business remotely and keep in touch with our customers. I have become the family man that I never dreamed I would become over the past 10 years, and it is a dream come true.

Lin Nan and his family spending time during the pandemic.

(left to right): Yuanna, Rong Xu, and Lin Nan enjoying time together during the pandemic.

Face-to-face communication is certainly always the most effective form of real-time interaction, but it requires close proximity to others. But when this is impossible, we realize the advantages of online meetings, including time, convenience, and economic impacts.

For us, we can almost respond and interact immediately, without trying to squeeze another customer site visit into our busy travel schedules, which could take another few weeks or even months. Without physically traveling, we actually get more support from our colleagues in applications and R&D, even from different time zones, which provides more expertise and profound knowledge to our customers that salespeople normally cannot deliver. In the scientific field, this is really valued by customers.

On the other hand, for customers, it is easier to set up and participate, since meetings can be attended from anywhere and at any time with a smart device and internet access. Especially when a meeting is presented by an application scientist, rather than a salesperson.

This may become the new norm for communication.

This type of lifestyle change probably only comes once in a lifetime. It can be depressing and frustrating, but at the same time, it is valuable and enjoyable to me that I could spend more time with family, something that I never did before, and I can make up for lost time with them.

Especially with the birth of my new baby daughter this July, I have been fully involved and able to foster her growth without being away, missing moments that I missed with my two and half year old son. There is no escape from waking up in the middle of the night, changing diapers, and bottle feeding. Like it or not, that is all part of our life.

I named my son “煦” pronounced “XU” and my daughter “熙” pronounced “XI”.

Not only do both characters look similar, but the spelling is similar as well. The only difference is the last letter, which is “U” and “I”.

Both characters mean warm and harmonious sunshine, which my son and daughter bring to my life. It reflects my faith as well, there is always a bright side, and everything is at its best arrangement.

Among the world of unrest we are experiencing now, a little sunshine is particularly important to keep the faith within.

Tomorrow will be fine!

“Don’t Sweat the Small Stuff” vs. “It’s the Little Things that Matter Most”

Dr. Stuart Wright, Senior Scientist, EDAX

A few weeks ago, my colleague at EDAX, Shawn Wallace, posed a question that has stayed with me, and so I thought my turn at the EDAX blog would be a good place to address it. Shawn was building an EBSD structure file for a new phase and encountered the following dialog for adding an atom to the unit cell.

Dialog box for building a new structure file for a new phase.

Shawn asked how important it was to get the Ion Type correct for the structure he was working with. I realized I had implemented this capability several years ago for kinematical calculations of structure factors but had never really explored it’s impact on the calculations. I guessed that it would not have much of an impact, but I wasn’t entirely sure that was the case. The choice of ion type affects the atomic scattering factor used in structure factor calculations. I looked through our phase structure database for a binary compound containing Fe and decided to use a simple Al-Fe structure to check out the effect of the ion type selection on the structure factor calculation.

Structure factors for the Fe and Fe+3 selections in the dialog box.

I calculated structure factors for the Fe and Fe+3 selections in the dialog box above. As shown, the difference in the structure calculation results is imperceptible in the kinematically simulated patterns. The maximum difference between the two patterns is only a 1.6% difference in the relative intensity of the {100} bands.

Kinematically simulated patterns for Fe and Fe+3.

Here is a table showing that the structure factors are quite similar, confirming my initial guess. I haven’t tried any other structures, so it is not a complete study, but I suspect other structures will follow the trend shown by the simple Al-Fe structure. Thus, my conclusion is, Don’t Sweat the Small Stuff.

(hkl) FFe FFe+3
110 4.773 4.826
100 1.291 1.738
200 3.256 3.252
211 2.566 2.562
111 1.098 1.104
220 2.189 2.186
222 1.633 1.632
210 0.913 0.908
310 0.858 1.856
321 1.462 1.461

With that little study wrapped up, I turned my attention to choosing the Debye-Waller factor used in the dynamical simulation. In the dialog above, it says the default Debye-Waller factor for iron is “0.003106 for bcc, 0.533 for fcc”. Does the choice of Debye-Waller factor matter? Here are dynamically simulated patterns for these values.

Dynamically simulated patterns using the Debye Wall factor.

The two patterns are quite different. To correctly use the new simulation tools, I need to expend some effort to learn more about Debye-Waller factors. Clearly, It’s the Little Things that Matter Most.

Want a Free Set of Microanalysis Standards?

Dr. Shangshang Mu, Applications Engineer, EDAX

Modern EDS systems are capable of quantitative analysis with or without standards. Unlike standard-less analysis, the k-ratio is either calculated in the software or based on internal standards. For analysis with standards, it is measured from a reference sample with known composition under the same conditions as the unknown sample. As an applications engineer, sometimes users ask me where to order these standards. Usually, I point them to the vendors that manufacture and distribute reference standards where you can order either off-the-shelf or customized standard blocks. In addition to these commercial mounts, I always tell them that they can request a set of mineral, glass, and rare earth element phosphate standards from the National Museum of Natural History free of charge! These are very useful standards that I’ve seen widely used in not only the geoscience world but also in various manufacturing industries. These free standards are also great for those graduate students with limited budgets and ideal for practicing sample preparation (yes, I was one of them).

This set of standards is officially called the Smithsonian Microbeam Standards and includes 29 minerals, 12 types of glass, and 16 REE phosphates. You can find out more information about these standards and submit a request form by clicking on the link below:
https://naturalhistory.si.edu/research/mineral-sciences/collections-overview/reference-materials/smithsonian-microbeam-standards

I mentioned sample preparation earlier. Yes, you read that right. These standards come in pill capsules containing from many tiny grains to a few larger ones and you need to mount them on your own (Figure 1).

Grains in a pill capsule.

Figure 1. Grains in a pill capsule.

Since you can get the information such as the composition, locality, and references for each standard from the website, what I want to discuss in this blog post is how to prepare them properly for X-ray analysis. The first tricky thing is to get them out of the capsules. The grains in Figure 1 are almost the largest in this set and you won’t get too many of this size. Some of the grains are even too tiny to be seen at first glance. For the majority that are really tiny, you need to tap the capsule a couple of times to release the grains that get stick to the capsule wall, then you can open the capsule very carefully and let the grains slide out with a little tapping.

For mounting, the easiest way is to mount the standards in epoxy using a mounting cup and let it cure. I did this in a fancy way to make it look like a commercial mount (Figure 2). I ordered a 30 mm diameter circular retainer with 37 holes used by commercial mount manufacturers (Figure 3) and filled the holes with standards on my own. I must admit that the retainer is not cheap, but you can machine the mount by yourself or have a machine shop do it for you. In addition to looking pretty, the retainer ensures a good layout so you can quickly locate the standards you need during microanalysis, and you can mount the same type of standards on one block and get rid of the hassle of frequently venting and pumping the SEM chamber to switch standard blocks.

Examples of commercial mounts.

Figure 2. Examples of commercial mounts.

 

30 mm diameter circular retainer with 37 holes.

Figure 3. 30 mm diameter circular retainer with 37 holes.

To prevent the tiny grains from moving and floating up when pouring the epoxy mix, I placed the retainer upside down and pressed it onto a piece of sticky tape (Figure 4a) and positioned the grains on the sticky surface of the tape within the holes. When tapping the capsule to let the grains slide out and fall into the hole, the other holes were covered to prevent contamination (Figure 4b). These holes are small in diameter and pouring the epoxy mix directly will trap air bubbles in the hole to separate the grains from the epoxy mix. To overcome this problem, I filled up the hole by letting the epoxy mix drip down very slowly along the inner surface of the hole.

Positioning grains within the holes of the retainer.

Figure 4. Positioning grains within the holes of the retainer.

For general grinding, I start with wet 240 grit SiC sandpaper with subsequent use of 320, 400, 600, 800, and 1,200 grit wet SiC sandpapers. But coarser grits can grind off tiny grains in this case, so I would recommend starting with a relatively fine grit based on the sizes of the grains you receive and always use a light microscope or magnifier to check the grinding. For polishing abrasive, I used 1 micron and 0.3 micron alumina suspensions on a polishing cloth. For the grains used as standards or quantification in general, the surface needs to be perfectly flat. However, the napped polishing cloth tends to abrade epoxy and the grains at different rates, creating surface relief and edge rounding, especially on tiny grains. To mitigate this effect, the polishing should be checked under a light microscope constantly and stopped as soon as the scratches are removed. A vibratory final polishing with colloidal silica is optional. Followed by ultrasonic cleaning and carbon coating, the standard mount is ready to use.

Note that commercial mount manufacturers may prepare standards individually (especially for metal standards) and insert them into the holes from the back of the retainer and fasten them with retaining rings (Figure 5a). A benefit of this approach is that the standards on the mount are changeable, so you can load all the standards you need on one mount before microanalysis. I used to make several individual mounted standards that can fit into the retainer (Figure 5b) but this process is very time consuming and much trickier to keep the small surface flat during grinding and polishing.

a) The back of a commercial metal standard mount. b) A tiny cylindrical mount that can fit into the retainer holes.

Figure 5. a) The back of a commercial metal standard mount. b) A tiny cylindrical mount that can fit into the retainer holes.

This is definitely a good set of standards to keep in your lab. With EDAX EDS software, in addition to quantification with these standards, you can also use them to create a library and explore the Spectrum Matching feature. The next time you want to quickly determine the specific type of a mineral, you can simply collect a quick spectrum and click the “Match” button, and the software will compare the unknowns to the library you just created.

Between the Lines

Dr. René de Kloe, Applications Specialist, EDAX

While I am testing new hardware and software versions, I use it as an opportunity to collect some data on unique materials. Testing detector speed or general software functionality is easiest on a simple material like an undeformed Ni or Fe alloy. But, I think it is a shame to perform longer duration tests on materials I have already seen many times before. For such occasions, I look through my collection of materials for something nice to map. During testing of the upcoming APEX™ 2.0 EBSD software, I collected a few larger scans on fossils that I had found during geological fieldwork and family holidays. This included large single-field scans and a Montage map, where we combine beam scans with stage movements for a large mosaic map.

Cross-section through a fossil crinoid stem and IPF on PRIAS™ center map of the fossil crinoid stem sample collected from the indicated area.

Figure 1. a) Cross-section through a fossil crinoid stem. b) IPF on PRIAS™ center map of the fossil crinoid stem sample collected from the indicated area.

For example, Figure 1a shows a cross-section through a fossil crinoid stem. At the edge, the lighter areas represent the structure of the organism, while the darker areas are later sedimentary infill.

This is beautifully visible in the 2.1 x 1.7 mm IPF on PRIAS™ center map, where the biomineral structure appears smooth and fine-grained. In contrast, the infill is more equiaxed and shows topography due to compositional differences (Figure 1b).

Another beautiful scan was collected while I was trying out the new APEX™ 2.0 EBSD Montage map wizard. This wizard allows easy pre-imaging of the entire scan field to set the actual scan area. With the wizard, setting up such a large, 18 million point, 30-field Montage map over a 1.3 x 7 mm area can be done in a few minutes.

Calcite rock sample with fossils and EBSD Montage map of one of the nummulite fossils.

Figure 2. a) Calcite rock sample with fossils. b) EBSD Montage map of one of the nummulite fossils.

We collected these two scans on calcite rocks for which you can simply load the appropriate crystal structure. But collecting data is not always that easy, especially if you are not sure what phase(s) you have in your sample. And ultimately, EBSD data collection is based on pattern analysis and then matching the detected bands against a lookup table. In most cases, you can just search the included EDAX structure file database that contains close to 500 phases and covers most commonly studied materials, such as the calcite used for the scans above.

But where do these files come from? Partly, they are a result of our combined legacy. Over the years, we have seen many materials and often painstakingly identified which bands to select to get reliable indexing results. Nowadays, you can create phase files directly using atomic and crystallographic information. However, you can continue to extract the majority of “new” phase files from XRD databases, such as the AMCS, ICSD, or ICDD PDF databases. These databases contain 10’s to sometimes 100’s of thousands of phase descriptions that are based on XRD measurements. The XRD data shows which lattice planes are effective X-ray diffractors, and are also useful to construct a structure file for electron diffraction patterns.

Indexed olivine EBSD pattern.

Figure 3. Indexed olivine EBSD pattern.

And there the fun starts. Often there are multiple possibilities for phases or minerals (e.g., solid solution series) available in the database. Which one to select? And in many cases, there is no single-phase file that matches the pattern exactly. There are always bands that do not get labeled or are shown in the overlay that are not visible in the real pattern. This is due to the differences between X-ray and electron diffraction intensities or simply incomplete database entries. Time for some human intervention. The APEX™ EBSD software contains advanced tools to modify and optimize the reflector tables of imported or calculated structure files. First, the color-coding itself. All bands are labeled with a color that corresponds to the IPF color triangle, so equivalent lattice planes get identical colors. This allows a visual inspection if bands that are designated with the same color also appear identical.

IPF color triangle.

Figure 4. IPF color triangle.

Then there is a band ID tool to help identify non-labeled bands in the diffraction patterns. When a pattern appears correctly indexed, but a number of bands are not labeled, the user can draw a line on the missing band. The software then shows which lattice plane corresponds to that band and also indicates all crystallographic equivalent planes. When it is still difficult to identify the correct indexing solution, it can be beneficial to bypass the Hough band detection and instead manually draw the bands for indexing. A good trick for low symmetry crystals is only to select the thinnest bands. These correspond to the lattice planes with the largest d-spacings and should be the important low-index crystallographic planes. By excluding the (often) large number of bands with similar bandwidths, you reduce the number of options and more quickly land at the best matching orientation or phase.

Manual Band Selection tool.

Figure 5. Manual Band Selection tool.

When a solution is found that matches the thin bands, you can start drawing in the other ones. When drawing a band, the software automatically shows where all the crystallographic equivalent planes should be. If a line is drawn where no band is present, you have the wrong candidate, and you need to look further. If all the indicated bands match in appearance and width, you can enable the reflector. This way, it is easy to interactively generate a matching phase file. Just keep in mind that when you have optimized a structure file to a pattern, it is a good idea to find some more patterns from that phase (if necessary, just rotate the sample to get a different orientation) and verify that all the bands in the other patterns are also properly identified. This is especially important for low symmetry materials where few lattice planes are equivalent.

Band optimization sequence on an EBSD pattern from W2C. The initial reflector table (a) misses a number of strong bands. Manually selecting a band (b) shows which reflector this is and where the crystallographic equivalent bands should be. This can be repeated (c) until all clear bands have been labeled.

Figure 6. Band optimization sequence on an EBSD pattern from W2C. The initial reflector table (a) misses a number of strong bands. Manually selecting a band (b) shows which reflector this is and where the crystallographic equivalent bands should be. This can be repeated (c) until all clear bands have been labeled.

Although it can be rewarding to identify a new phase and optimize the structure file to allow for EBSD mapping of a new and interesting material, I would like to end with a word of warning. When you are working with a good pattern and successfully identify the phase and orientation, it is very tempting to keep looking for bands and completely fill the pattern with everything you can see. But that is often a bad idea, as the weaker bands will typically not get selected by the Hough transformation on the poorer patterns that are used during indexing. Enjoy playing with the materials and structure files, but don’t overdo it.

Diffraction pattern with all visible bands enabled for indexing.

Figure 7. Diffraction pattern with all visible bands enabled for indexing.