Dr. Shangshang Mu, Application Scientist, Gatan/EDAX
Over the past year, I’ve rekindled my enjoyment of traveling as I visited customers in the Americas, Asia, and across Europe. During my return journey, I was deeply touched by an airline billboard at the Munich, Germany airport that read, “We all live under one sun. Let’s see it again.” Indeed, it is genuinely nice to see the world once more since reemerging from the pandemic.
While flying over Hudson Bay, an inland marginal sea of the Arctic Ocean, I saw numerous ice caps floating on the water from the aircraft’s belly camera view. To me, these were very reminiscent of the counts per second (CPS) map (Figure 1) in one of the wavelength dispersive spectrometry (WDS) datasets I shared with customers during these trips. Although they were orders of magnitude larger than the micron-scale sample, the resemblance was striking.
Figure 1. Ice caps in Hudson Bay (left) resemble the CPS map of a Si-W-Ta sample (right).
Throughout these journeys, our EDAX Lambda WDS system was one of the hot topics drawing customers’ attention. This parallel beam spectrometer features a compact design compatible with almost every scanning electron microscope (SEM). The improved energy resolution and sensitivity and lower limits of detection make it an excellent supplement to your energy dispersive spectroscopy (EDS) detectors. The CPS map I referred to was captured from a Si-W-Ta sample. The energy peaks of Si K, W M, and Ta M are heavily overlapped, with only approximately 30 eV energy difference between each other. Lambda WDS systems provide up to 15x better energy resolution than typical EDS systems, effectively resolving the ambiguity in analysis.
Figure 2. Overlay of EDS (red outline) and WDS (cyan color) spectra from the central area of the Si-W-Ta sample.
The overlay of EDS/WDS spectra from the central area of the map shows that the Lambda WDS system intrinsically resolves the overlapping EDS peaks (red outline), as depicted by the cyan color WDS spectrum (Figure 2). The shortcoming of EDS in resolving these overlapping peaks results in the distributions of the three elements appearing identical in EDS maps. However, the WDS maps provide clear and distinct visualizations of the individual distributions of the three elements (Figure 3).
Figure 3. EDS (top) and WDS (bottom) maps of the Si-W-Ta sample. The WDS maps resolve the artifacts due to Ta M, Si K, and W M peak overlaps in the EDS maps.
This year’s M&M meeting is just around the corner. If you are traveling to this entirely in-person event, stop by our booth (#504) to check out our integrated EDS-WDS SEM solutions and many other products that will capture your interest.
Dr. Shangshang Mu, Applications Engineer, Gatan/EDAX
The new APEX™ 3.0 is the ultimate materials characterization software, integrating Energy Dispersive Spectroscopy (EDS), Electron Backscatter Diffraction (EBSD), and Wavelength Dispersive Spectrometry (WDS) to deliver previously unattainable solutions. This optimized configuration offers the uncompromised performance of each technique and allows users to combine them for the ultimate materials insight. All three techniques seamlessly operate within the APEX, blending powerful elemental and crystallographic analysis routines through an intuitive interface to deliver outstanding data collection, faster analysis, and flexible reporting for users of all levels.
What does APEX WDS look like?
WDS functionalities are implemented seamlessly with the EDS graphical user interface. The user can quickly adapt to the new functionalities and employ WDS when and where EDS reaches the limit. With one-click from start to finish, Auto WDS allows fully automated WDS scan list generation, optimum sample height determination, and spectrum collection. It simultaneously collects EDS and WDS spectra and displays them side-by-side or overlaid for easy data visualization and interpretation (Figure 1), with no overlapping or overloading of windows.
Figure 1. Simultaneous EDS-WDS spectrum acquisition user interface.
APEX allows you to set an intermediate position for the EDS detector to ensure optimal count rates for both techniques.
Figure 2. Simultaneous EDS-WDS mapping user interface.
Sets of combined EDS-WDS spectrum, linescan, and mapping data at different stage positions can be done via automated batch collection routines (Figure 2) to streamline SEM experiments. EDS and WDS data collection settings are managed in one user-friendly batch scan list (Figure 3).
Figure 3. Combined EDS-WDS batch list.
The quantitative elemental analysis supports individual technique or combined EDS-WDS standards. You can easily switch between EDS and WDS standards for each element by clicking on the icon in front of the element (Figure 4).
Figure 4. Quantitative results with combined EDS-WDS standards.
With the addition of WDS capabilities, APEX 3.0 now includes EDS, EBSD, and WDS. Each characterization tool can operate independently to utilize EDAX’s technological advancements or integrates data to provide solutions that were once unachievable.
When you are in Sweden at Scandem 2019 it is the perfect time to order SOS as an appetizer or for dinner. It is made of smör, ost and sill (butter, cheese and herring) served together with potatoes. Sometimes the potatoes need a little bit of improvement in taste. It is very easy to take the salt mostly located on all tables and salt them. Doing that I thought about how easy it is to do this today and what am I really pouring on my potatoes?
Salt was very important in the past. In ancient times salt was so important that the government of Egypt and other countries setup salt taxes. Around 4000 years ago in China and during the Bronze age in Europe, people started to preserve food using brine. The Romains had soldiers guarding and securing the transportation of salt. Salt was as expensive as gold. Sal is the Latin word for salt and the soldiers used to get their salare. Today you still get a salary. Later ‘Streets of Salt’ were settled to guarantee safe transportation all over the country. As a result, cities along these roads got wealthy. Even cities, like Munich, were founded to make money with the salt tax. Salt even destroyed empires and caused big crises. Venice fought with Genoa over spices in the middle ages. In the 19th century soldiers were sent out to conquer a big mountain of salt of an Inconceivable value, lying along the Missouri River. We all know the history of India´s independence. Mohandas Gandhi organized a salt protest to demonstrate against the British salt tax. The importance of the word salt is also implemented in our languages, “Worth the salt”, “Salz in der Suppe” or “Mettre son grain de sel”.
The two principle ways of getting salt are from underground belts and from the sea. It can be extracted from underground either by mining or by using solution mining. Sea salt is produced in small pools which were filled up during high tide and water evaporates under sunny weather conditions. Two kinds of salt mining are done. Directly digging the salt out of the mountain, then dissolving it to clean it. Or hot water is directly used to dissolve the salt and then the brine is pumped up.
Buying salt today is no longer that expensive, dangerous or difficult. But now a new problem arises. I´m talking about salt for consumption, which usually means NaCl in nice white crystals. So, are there any advantages to using different kind of salts? If we believe advertisements or gourmets, it is important, where the salt we use came from and how it was produced. Today the most time-consuming issue is the selection of the kind of salt you want in the supermarket!
For my analysis I chose three kinds of salts from three different areas. The first question was, are the differences big enough to detect them using EDS or will the differences be related to minor trace elements which can only be seen in WDS. It was a surprise for me that the differences are that huge. I had a look at several crystals from one sample. Shown as examples are the typical analysis of the different compounds and elements for that provenance.
First looking at the mined salt. I selected a kind of salt from the oldest salt company in Germany established over 400 years ago. One kind from Switzerland manufactured in the middle of the Alpes and one from the Kalahari, to be as far away as possible from the others. The salt from Switzerland is the purest salt only containing NaCl with some minor traces. The German salt contains a bigger amount of potassium and the Kalahari salt a bigger amount of sulfur and oxygen (Figure 2.).
Secondly, I was interested in the salt coming from the sea. I selected two types of salt from French coasts one from the Atlantic Ocean in Brittany and another one from the Mediterranean Sea. The third one came from the German coast at the Baltic Sea. The first interesting impression is that all the sea salt contains many more elements. The Mediterranean salt contains the smallest amount of trace elements. The salt from the Atlantic Ocean and the Baltic sea contains, besides the main NaCl, phases containing Ca, K, S, Mg and O. A difference in the two is the amount of Ca containing compounds (Figure 3.).
Finally, I was interested in some uncommon types of salt. In magazines and television, experts often publish recipes with special types supposedly offering a special taste, or advertising offers remarkable new kinds of healthy salt. So, I was looking for three kinds which seem to be unusable. I found two, a red and a black colored, Hawaiian salt. The spectrum of the red salt shows nicely that Fe containing minerals cause the red color. Even titanium can be found and a bigger amount of Al, Si and O. The black salt contains mainly the same elements. Instead of Fe the high amount of C causes the black color. A designer salt is the Pyramid finger salt, which is placed on top of the meat to make it look nicer. Beside the shape, the only specialty is the higher amount of Ca, S and O (Figure 4).
It was really interesting that salt is not even salt. As the shape of the crystals varies, so they differ in composition. In principle it is NaCl but contain more or less different kinds of compounds or even coal to color it. There are elements found in different amounts related to the type of salt and area it came from. These different salts are located in a few very small areas in and on the crystals.
And finally, I pour salt onto my potatoes and think, ok it is NaCl.
Not too long ago I went to my optometrist to get an eye exam for some replacement glasses. My last pair had been stolen after my car was broken into in broad daylight during lunch at a restaurant in the Bay Area. (What the thief planned on doing with my prescription glasses is still a mystery to me.)
Figure 1: The old phoropter* (top) and the new phoropter** (bottom).
It had been at least a couple years since my last examination, but I was prepared to be guided through all the typical tests, culminating with that “giant-machine-with-multiple-lenses” pressed into my face to help the optometrist determine the prescription that would best correct the errors in my vision. I’d later learn that this machine is called a phoro-optometer, or more commonly a “phoropter.” And, contrary to my previous experiences with this instrument, it was now a super-sleek, slimmed down, digital version of the machine, using a computer controlled digital refraction system to cycle through the refraction options instead of using stacks of physical lenses that had to be manually cycled by the optometrist.
It was much smaller, quieter, faster, and easier than the version with which I was familiar. I was thoroughly impressed. But I was even more impressed when the instrument was pulled away and I saw the Ametek logo emblazoned on the side of it.
I couldn’t help but reflexively blurt out “Hey I work there!” to which the optometrist looked up from my file and began curiously interrogating me about my history in the eye care industry. Sadly, he quickly lost interest after I explained that I worked in a different division of Ametek that manufactures EDS, EBSD, and WDS systems.
After my exam, for some reason I felt a bit intimidated about not knowing more about Ametek’s business units outside of the EDAX niche to which I belong. I knew Ametek was a huge corporation, steadily growing larger over the decades — mainly by acquisition of smaller companies – but I’d never really grasped the sheer size and breadth of everything Ametek does. This wasn’t the first time I’ve been in this type of situation. Prior to joining EDAX/Ametek I worked for another scientific instrumentation corporation, slightly smaller than Ametek but still a similar type of behemoth with a wide range of companies making products that service comparable industries and applications. Even at that corporation my knowledge of the business outside of my business unit’s portfolio was very limited. These places are just so big!
Working at large corporations like these can, at times, be a little bit discouraging if you think of yourself as just a single cog in a machine with thousands of moving parts. Giant corporations certainly seem to have a bad reputation these days and I’ll admit I’ve experienced my fair share of corporation-induced angst over the years. Working within a large bureaucracy can make completing the smallest internal tasks overwhelming. Being in a smaller company that is acquired – I’ve been through two acquisitions — can be disruptive to business and cause a lot of anxiety.
But is there a good side to these mega-corporations? I think so.
I can find some important benefits that could be argued to outweigh the negative aspects, not just to the cogs like myself but also to the markets that they serve. Whether or not these apply to other more prominent mega-corporations is debatable, but I think they seem to be reasonable positive characteristics, at least from my experience in the scientific instrumentation field.
Having the brand name recognition has always been an advantage. Customers (and their procurement departments) are typically more willing to do business with companies that have a long history of manufacturing products. Being in business for multiple decades with a proven track record of having the resources to reliably deliver products to the market and consistently service its user-base generates heaps of reassurance for customers that a younger or smaller company just can’t provide. It works similarly for vendors as well – it turns out that people are always more willing to sell you stuff if they’re confident that your company will pay for it.
Being in a large corporation also offers a huge advantage in the ability to research and develop new technology and product improvements. This can come by brute force – having deeper pockets to invest more money into R&D – or even by utilizing the synergy between individual companies under the corporation’s umbrella. EDAX is a great example of this in a couple ways. Ametek’s purchase of a new business unit in 2014 facilitated the development of EDAX’s groundbreaking Octane Elite and Octane Elect EDS systems, allowing for speed and sensitivity that had never been achieved before in any other EDS system. Collaboration between EDAX and another sister company within the Materials Analysis Division of Ametek, ushered in the release of EDAX’s new Velocity™ highspeed CMOS EBSD camera, by far the fastest EBSD system available. Realization of these two milestones of innovation would have been significantly delayed without the help of Ametek’s resources.
Figure 2: The Octane Elite (left) and the Velocity™ Super (right), two of EDAX’s products that were developed, in part, with the help of other business units inside Ametek.
But what I think tends to be the best part is that, as long as a company is meeting its targets and things are humming along nicely, corporations – at least the good ones, in my opinion — are usually happy to just let the business unit do its own thing. Having an “if it ain’t broke don’t fix it” mentality is the ideal way to keep the key talent happy and keep the business growing and making money. It also makes it possible to retain some semblance of the original company culture that contributed to its success in the first place. This is the holy grail for us cogs – being able to keep that small business feel while also being able to take advantage of all the big business benefits at the same time. Again, EDAX is a good example of this, with many of EDAX’s employees being legacy staff hired on long before the EDAX acquisition. This tells me Ametek must be doing something right.
So, I guess it’s debatable. While we may be willingly marching our grandchildren into a dystopia where three or four companies own all the businesses in the world, there are some undeniable advantages that working for a big company brings as well. And I take some comfort in the fact there are some very intelligent and innovative people behind the curtains, trying to do good things to make their customers happy and generally improve the lives of everyone in the world. We may or may not see all the things like the better phoropters out there, but our lives are almost certainly benefited by them whether we realize it or not.
A recent conversation on a list serv discussed sloppiness in the use of words and how it can cause confusion. This made me consider that in the world of microanalysis, we are not immune. We are probably sloppiest with two particular words. They are resolution and phase.
Let us start with how we use the word phase and how phases are commonly defined in microanalysis. In Energy Dispersive Spectroscopy (EDS), we use phase for everything, for example, phase mapping, phase library. In Electron Backscatter Diffraction (EBSD), the usage is a little more straightforward.
So, what is a phase? Well to me, a geologist, a phase has both a distinct chemistry and a distinct crystal structure. Why does this matter to a geologist? Two different minerals with the same chemistry, but with different structures, can behave in very different ways and this gives me useful information about each of them.
The classic example for geologists is the Al2SIO5 system (figure 1). It has three members, Kyanite, Sillimanite, and Andalusite. They each have the same chemistry but different structures. The structure of each is controlled by the pressure and temperature at which the mineral equilibrated. Simple chemistry tells me nothing. I need the structure to tease out that information.
Figure 1. Phase Diagram of the Al2SiO5 system in geological conditions. Different minerals form at different pressures and temperatures, letting geologists know how deep and/or the temperature at which the parent rock formed.**
EDS users use the term phase much more loosely. A phase is something that is chemically distinct. Our phase maps look at a spectrum pixel by pixel and see how they compare. In the end, the software goes through the entire map and groups each pixel with like pixels. The phase library does chi squared fits to compare the spectrum to the library (figure 2).
Figure 2. Our Spectrum Library Match uses as Chi-squared fit to determine the best possible matches. This phase is based on compositional data, not compositional and structural data.
While the definition of phase is relatively straight forward, the meaning of resolution gets a little murkier. If you asked someone what the EDS resolution is, you may get different answers depending on who you ask. The main way we use the term resolution when talking about EDS is spectral resolution. This defines how tight the peaks in a spectrum are (figure 3).
Figure 3. Comparison of EDS vs. WDS spectral resolution. WDS has much higher resolution (tighter peaks) than EDS, but fewer counts and more set-up are required.
The other main use of resolution, in EDS is the spatial resolution of the EDS signal itself (figure 4). There are many factors which determine this, but the main ones are the accelerating voltage and sample characteristics. This resolution can go from nanometers to microns.
Figure 4. Distribution of the electron energy deposited in an aluminum sample (top row) and a gold sample (bottom row) at 15 kV (left column) and 5 kV (right column). Note the dramatic difference in penetration given by the right hand side scale bar.
The final use of resolution for EDS is mapping resolution. This is by far the easiest to understand. It is just the step size of the beam while you are mapping.
Luckily for us, the easiest way to find out what people mean when they use the terms resolution or phase, is just to ask. Of course, the way to avoid any confusion is to be as precise as possible with your choice of words. I resolve to do my part and communicate as clearly as I can!
…L. A. – this is the title of a popular song from Joshua Kadison which one may like or dislike but at least three words in this title describe a significant part of my work at EDAX. Truth be told I’ve never been to Los Angeles, but as an application specialist traveling in general is a big part of my job. I´m usually on the move all over Europe meeting customers for trainings or attending exhibitions and workshops. This part of my job gives me the opportunity to meet with lots of people from different places and have fruitful discussions at the same time. If I am lucky, there is sometimes even some time left for sightseeing. The drawback of the frequent traveling is being separated from family and friends during these times.
Nowadays it is easy to stay in touch thanks to social media. You send a quick text message or make phone calls, but these are short-term. And here we get back to the title of this post and Joshua Kadison´s pop song, because quite some time ago I started the tradition of sending picture postcards from the places I travel to. And yes, I am talking about the real ones made from cardboard, documenting the different cities and countries I get to visit. Additionally, these cards are sweet notes highly appreciated by the addressee and are often pinned to a wall in our apartment for a period of time.
Within the last couple of years, I notice that it is getting harder to find postcards, this is especially true in the United States. Sometimes keeping on with my tradition feels like an Iron Man challenge. First, I run around to find nice picture postcards, then I have to look for stamps and the last challenge is finding a mailbox. Finally, all these exercises must be done in a limited span of time because the plane is leaving, the customer is waiting, or the shops are closing. But it is still worth it.
It is not only the picture on the front side, which is interesting, each postcard holds one or more stamps – tiny pieces of artfully designed paper – as well. Postage stamps were first introduced in Great Britain in 1840. The first one showed the profile of Queen Victoria and is called “Penny Black” due to the black background and its value. Thousands of different designs have been created ever since attracting collectors all over the world. Sadly, this tradition might be fading. Nowadays the quick and easy way of printed stamps from a machine with only the value on top seems to be becoming the norm. But the small stamps are often beautiful to look at and are full of interesting information, either about historical events, famous persons or remarkable locations.
A selection of postage stamps from countries I have visited.
For me, as a chemist I was also curious about the components of the stamps. Like a famous painting, investigated by XRF to collect information about the pigments and how the artist used them. For the little pieces of art, the SEM in combination with EDS is predestinated to investigate them in low vacuum mode without damaging them. The stamps I looked at are from my trips to Sweden, Great Britain, the Netherlands and the Czech Republic. In addition, I added one German stamp as a tribute to one of the most important chemists, Justus von Liebig after whom the Justus-Liebig University in Gießen is named, where he was professor (1824 – 1852) and I did my Ph. D. (a few years later).
All the measurements shown below were done under the same conditions using an acceleration voltage of 20 kV, with a pressure of 30 Pa and 40x magnification. With the multifield map option the entire stamp area was covered, using a single field resolution of 64×48 each and 128 frames.
The EDS results show that modern paper is a composite material. The basic cellulose fibers are covered with a layer of calcium carbonate to ensure a good absorption of the different pigments used. This can be illustrated with the help of phase mappings. Even after many kilometers of travelling and all the hands treating the postcards all features of the stamps are still intact and can be detected. The element mappings show that the colors are not only based on organic compounds, but the existence of metal ions indicate a use of inorganic pigments. Typical elements detected were Al, S, Fe, Ti, Mn and others. The majority of the analysis work I do for EDAX and with EDAX customers is very specialized and involves materials, which would not be instantly familiar to non-scientists. It was fun to be able to use the same EDS analysis techniques on recognizable, everyday objects and to come up with some interesting results.
After all these years I still get excited about new technologies and their resulting products, especially when I have had the good fortune to play a part in their development. As I look forward to 2019, there are new and exciting products on the horizon from EDAX, where the engineering teams have been hard at work innovating and enhancing capabilities across all product lines. We are on the verge of having one of our most productive years for product introduction with new technologies expanding our portfolio in electron microscopy and micro-XRF applications.
Our APEX™ software platform will have a new release early this year with substantial feature enhancements for EDS, to be followed by EBSD capabilities later in 2019. APEX™ will also expand its wings to uXRF providing a new GUI and advanced quant functions for bulk and multi-layer analysis.
Our OIM Analysis™ EBSD software will also see a major update with the addition of a new Dictionary Indexing option.
A new addition to our TEM line will be a 160 mm² detector in a 17.5 mm diameter module that provides an exceptional solid angle for the most demanding applications in this field.
Elite T EDS System
Velocity™, EDAX’s low noise CMOS EBSD camera, provides astonishing EBSD performance at greater than 3000 fps with high indexing on a range of materials including deformed samples.
Velocity™ EBSD Camera
Last but not least, being an old x-ray guy, I can’t help being so impressed with the amazing EBSD patterns we are collecting from a ground-breaking direct electron detection (DED) camera with such “Clarity™” and detail, promising a new frontier for EBSD applications!
It will be an exciting year at EDAX and with that, I would like to wish you all a great, prosperous year!
Dr. Michaela Schleifer, European Regional Manager, EDAX
The European team had a very exhausting but successful week last week. Some months ago, we discussed the possibility of holding a user meeting at our headquarters in Weiterstadt, Germany. During our stay in Wiesbaden it became a tradition to do at least one user meeting or workshop a year. Because of our move to Weiterstadt and the development of some new structure in the European organization, it took quite some time to plan another user meeting. In spring time, we discussed how to satisfy the different areas in Europe regarding language and also how to transfer information about new technology to our distributors. We finally decided that we should organize 3 different meetings during the week of October 15th. The first two days were for our German speaking customers in Europe, mid-week we invited our distributors and on the last two days we offered a user meeting for our English-speaking customers. There was a lot of organization to be done, like making hotel reservations, preparing presentations, organizing hosting and also booking nice restaurants for the evening events. All of us were a bit nervous about whether everything would work, whether we had forgotten anything important and whether our SEM and system would work properly. The week before the meetings we installed the Velocity™ camera, our new high speed EBSD system in our demo lab and our application people were very happy with the performance and had fun playing around with it.
On Monday October 15th we started our first user meeting in the Weiterstadt office at around 1 pm with customers from the German speaking area. Around 45 participants joined the meeting. At the beginning we gave an overview of our current products and explained that our complete SDD series is using the Amptek modules with Si3N4 windows. Based on some spectra we showed the improved light element performance. After that Felix, one of our application specialists, showed our new user interface APEX™ live and the discussion which arose showed the interest from our users. Although only some users are doing EDS on a TEM we explained a little bit about the differences between EDS on a TEM and on a SEM. We finished the first day with a question and answer session and invited all the participants to a nice location in Darmstadt to have a typical German dinner together.
The next day was completely dominated by EBSD. Our EBSD product manager Matt Nowell, who came from Draper, USA to support us during our meetings, demonstrated the performance of our new Velocity™ EBSD camera. Matt also explained the differences in the camera technology using CCD or CMOS chips and described direct electron detection. It was easy to get more than 3000 indexed points per second while measuring a duplex steel with the Velocity™ camera. Our EBSD application specialist René de Kloe presented a lot of tips and tricks regarding EBSD measurements and analysis of measurement too and did not get tired of answering all the questions. At the end of our program all participants left with a good feeling having learnt a lot and got some good ideas about how to improve their measurements or what they might try to measure on their own samples.
The next day we shortened our program for our distributors and explained our product range and gave live demonstrations of APEX™ software platform and the Velocity™ CMOS EBSD camera. This day was dominated by a lot of discussions with the group and also by questions about our roadmap for 2019.
On Thursday and Friday of this week we did the same program for our English-speaking customers in Europe as we did for the German speaking customers. We had around 15 participants.
During this week we had around 75 customers in our office in Weiterstadt. Each customer was different in his applications and how he uses our systems but what we could observe during the evening was that most of them are very similar in what they like for dinner:
Late on Friday evening the whole European team was very happy that we managed the week with all the meetings and that based on the feedback we got it was a successful week. You may be sure that all of us went home and had a relaxing weekend!
I would like to thank Matt, Rene, Felix, Ana, Arie, Rudolf, Andreas and Paul and especially our customers who gave some interesting presentations about their institutes and the work they are doing there.
My family and I love the beach. We love to swim in the water, ride the waves, and play in the sand. Each summer we typically spend time at Sunset Beach, North Carolina. After years of seeing the cool stuff in the SEM, materials science and microscopy are always topics of discussion. This year, after enjoying the musical Hamilton, my wife was inspired to start working on a periodic table of elements rap song. My 13-year-old learned more about metalworking watching the History Channel show, Forged in Fire, where participants are challenged to make different weapons from assorted metallic sources. My favorite part was watching them evaluate different parts of a bicycle for heat-treatable steel to recycle. One of my favorite moments though was unpacking my beach shoes on the first day.
Generally, when we visit a beach, we try to bring home a shell or a piece of driftwood. However, when I was putting on my shoes for the first time, I noticed some sand was still present. My last beach trip had been to the Cayman Islands. I immediately noticed that this sand looked much different than the sand at Sunset Beach. I decided to save a little bit of each for some microscopy and microanalysis when I got back home.
When I looked at them both more closely, I saw that the sand from Sunset Beach (SB) on the left was much darker with black flecks, while the sand from Grand Cayman (GC) was much lighter. Thinking about the possible composition of the sand got me thinking about the bladesmithing competition held at the TMS annual meetings. One year, the team from UC Berkeley created a sword using magnetite found at local beaches using magnets. I thought it would be interesting to examine both of these sands with my SEM, EDS, and EBSD tools.
Sand grains from Sunset Beach.
Sand grains from Grand Cayman.
Initially I placed a bit of sand on an aluminum stub for SEM and EDS analysis. To reduce charging effects, I used the Low Vacuum capability of our FEI Teneo FEG-SEM, running at 0.1 mbar pressure. Images were collected using the Annular BackScatter (ABS) detector for atomic number contrast imaging. The sand grains from Sunset Beach were generally a little smaller than the Grand Cayman sand, as expected from visual inspection. Both sands exhibited cracking and weathering, which isn’t surprising in hindsight either. Many grains show flat surfaces, with internal structure visible with ABS imaging contrast.
I followed the imaging work with compositional analysis using EDS. The Sunset Beach sand was primarily composed of silicon and oxygen grains, which I suspect is quartz. The single brighter grain in Figure 3 was composed of an iron-titanium oxide. The Grand Cayman sand was primarily a calcium carbonate (Ca-C-O) material. The more needle shaped grains were primarily sodium and chlorine, which I assume is then salt that has solidified during the evaporation of the water. All this leads me to believe I really didn’t do a good job of cleaning my shoes after Grand Cayman.
While quartz being present in sand wasn’t surprising to me, the observation of calcium carbonate did remind me of some geological homework I did on the island. The water in Grand Cayman was very clear, which made it great for snorkeling. We swam around and saw a coral reef, a sunken ship, lots of fish, and stingrays. To understand why the water was so clear, I read that it was the lack of topsoil, and the erosion and runoff of topsail to the water that was responsible for the clarity. Looking again at this reference, it mentions that the top layer of the island is primarily composed of carbonates. The erosion of this material would explain the primary composition of the beach sand in my shoes.
Of course, the next step now is analyzing these sands with EBSD to determine the crystal structure of the materials. I’ve started the process. I’ve mounted some of the sand in epoxy, and hand polished to get some flat surfaces for analysis. I’m able to get EBSD patterns, but getting a good background is going to be tricky. I think the next step will be to watch my colleague Shawn Wallace’s webinar on Optimizing Backgrounds on MultiPhase samples to be presented on September 27th. You can also register for this here.
In the meantime, I’ll keep the sand samples on my desk to remind me of summer as the colder Utah winters will be approaching. It will be a good reason to stay inside and write the next chapter of this analysis for another blog post.
This summer was my third working for the EDAX Applications Team. It has been an amazing opportunity to be directly involved with research, customer support, and software testing here in Mahwah. I was able to continue with the APEX™ software testing that I worked on last summer which I found incredibly interesting because I’ve been able to observe the software evolve to best meet customer needs and improve in overall performance. I also had the chance to attend the Microscopy and Microanalysis (M&M) show in Baltimore, MD. This was an incredible experience for an undergraduate student, like me, interested in Materials Science and Microscopy. I was able to connect with people in the field, attend talks on topics at the forefront of Microscopy research, and present a poster that I have been helping out with this summer here at EDAX.
The majority of my time this year has been focused on helping Dr. Jens Rafaelsen, the head of the Mahwah Applications Team, with the data collection and analysis for a paper on the effects of Variable Pressure on EDS. Although Variable Pressure is an incredibly useful tool for studying SEM samples that are susceptible to charging, the introduction of gas to the specimen chamber has implications that must be considered when collecting EDS spectra. Additional gas particles in the SEM chamber lead to a scattering of the electron beam, known as beam spread or beam skirting.
In order to study and quantify this phenomenon, we used a double insulated Faraday cup with a 10 µm aperture, pictured below, to measure the unscattered beam at different pressures and working distances. We also modeled this beam scattering using Monte Carlo simulations that consider the SEM geometry as well as the type of gas in the chamber, which vary based on the type of SEM. Based on our experimental and theoretical results, we determined that as much as 85% of the electron beam is scattered outside of the 10 µm diameter high pressures of 130 Pa. This is much more scattering than we had anticipated, based on previous papers on this subject, making these results incredibly important for anyone using variable pressure in the SEM.
Double insulated Faraday cup with a 10 µm aperture.
Unscattered Beam Percentage vs. Pressure: Theoretical
Unscattered Beam Percentage vs. Pressure: Experimental
Overall, I am very thankful for the opportunities that EDAX has given me this summer and in the past. As a member of the Applications Team, I was able to work alongside the Engineering, Software Development, Customer Support, and Sales teams in order to help provide customers with the best analysis tools for their needs. I also gained a deeper understanding of the research, data collection, and analysis processes for writing a paper to be published: a truly incredible experience for an undergraduate student. Above all, the plethora of knowledge and experience of those here at EDAX and their willingness to share this information with me and others has been the most valuable aspect of my time here.