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The dreaded “amorphous” hump created by x-rays scattering off plastic sample holders has plagued XRD users for decades. It’s a serious enough problem that we make a good volume of these holders from Aluminum which works very well for loose powders. The plastic scatters xrays at around 13 degrees 2Theta (Cu anode tube) which make a real mess of most geological patterns and isn’t fun to model out for Rietveld refinement. Zero background holders like our ZBH-32 work wonderfully in standard sample stages designed for a single sample at a time, but the large plate isn’t compatible with the autosampler.

I recently had a request for a hybrid holder which would allow for analysis of very small volumes of materials while retaining compatibility with the autosampler. This is almost identical to our standard powder holders, but with a well designed specifically for our small ZBH plate.

Key features include:

  • 6061-T6 Al material (anodized or as-machined)
  • Si(510) plate
  • Raised sample well minimizes the area of the sample holder in the plane of diffraction. (Original Siemens design)
  • Beveled well walls minimize the area of Al in the plane of diffraction
  • Other small modifications are made to improve reliability of these holders in the autosampler

One of the fundamental facts of lab-based X-ray production is that our x-ray tubes emit much more than the pure KA1 lines we rely on for material characterization and quantification. Most XRD users are familiar with techniques and hardware for the reduction or elimination of KB1, W LA1 and Bremsstrahlung, but take for granted the inseparable pair of KA1 and KA2 (referred to as the “doublet”). Luckily for us, these energies are present in strict proportion such that we can factor their paired presence into most XRD analysis to the point that one might barely notice their effect. However, the fact remains that we will see peak broadening at lower angles and completely independent additional peaks at higher angles due to this superfluous discrete emission.

Separating the doublet cannot be accomplished electronically or through absorption/attenuation such as might be effective for KB1 energies. It must be done in the primary-beam with an additional diffraction event. Primary-beam monochromators are generally classified by the number of diffraction events required for a photon to pass completely through the device. Single-bounce, 2-bounce and 4-bounce geometries are common with the latter providing the best energy resolution allbeit the lowest intensity (photon flux). My limited experience suggests that while the single-bounce models retain enough intensity to have some application in powder XRD, the others are relegated to HR-XRD applications such as XRR.

The alignment for any of this hardware is not for the faint of heart as it begins with coarse adjustments using fluorescent screens in the beam path. This was essential for us given how dramatically misaligned the monochromator had become after so many attempts to bring it back into operation. We actually needed our SDD system to verify that we were tuning for Cu KA1 energy rather than the KB1 emissions because some of the most basic aspects of the alignment had pushed way beyond their intended position.

Along the way we built ourselves a motorized remote adjustment tool which we’ll return to the user as small adjustments are required on a regular basis with this kind of monochromator to retain maximum intensity. It’s quite useful and even versatile enough to allow for the adjustment of multiple control knobs.

One final note regarding intensity. It’s easy to get excited about energy resolution like this, but bear in mind that we’re looking at ~20x reduction in intensity due to the inherent losses involved in the primary diffraction event. This data was collected at 10x the normal speed and at half the normal 2Theta step increment so it looks very good, but one would need a compelling reason to slow their data collection this much.

Another side effect of performing your energy discrimination in the primary beampath is that other issues such as fluorescence effects (incident x-rays exciting elements in the sample causing high background intensities) are harder to avoid than they would be with a diffracted-beam monochromator. The 4x reduction in intensity inherent in the diffracted-beam monochromatization makes it a poor choice to eliminate these effects when the incident intensities are already so low. We recommend energy-dispersive detectors such as our SDD-150 to eliminate extraneous energies without sacrificing net intensity. We’ve also worked with the Bruker LynxEye XE-T detector which has a very high energy resolution compared to other position sensitive detectors (PSD). Contact KS Analytical Systems for more information on these options.

The majority of the samples we receive come in volumes high enough to completely fill the well in any of our standard sample holders. Some are too large or oddly shaped which calls for a special holding solution like those listed here, but many are simply very small quantities of powder. Placing these in a standard holder would leave them well outside the plane of diffraction and provide terrible data, not to mention substantial scatter
or diffracted background from whatever the powder is placed on. The answer is a zero background sample holder (ZBH). Most our users at KS Analytical Systems run the original Siemens/Bruker plates, but others are using Si(100) and even glass substrates. We’re very happy to say that
we’re able to offer a direct replacement for these with our new ZBH-32 holders. These fit most Siemens XRD systems and can be customized for use in most any other system. Contact us for more information on this. The scan below shows the data collected from a single mg of Silicon 640B standard powder spread across a ZBH.

Off Planar Quartz ZBH w-1mg 640B

Full scan of 1mg Silicon 640B standard spread across a ZBH

ZBH-32

ZBH-32 sample holders mounted for Siemens and Bruker single sample stages.

 

Some users report acceptable results using simple glass plates. While there are serious caveats here, it may be a reasonable solution for some users. The issue with amorphous glass is not diffracted peaks in the background, but rather, scatter off the surface. X-ray scattering off a surface is inversely proportional to the average atomic number of that material. That is to say, the lighter the matrix, the more efficiently it will scatter X-rays. This is why we use a pure Graphite sample to characterize the emission spectra of our XRF instrumentation. The glass sample shows the expected scatter “hump” starting at a very low angle and it doesn’t flatten until nearly 100°2Θ. While some of this can be modeled and subtracted with good profile fitting software like Jade 2010, it can be challenging to match the data quality of a good ZBH. We’re working on a series of videos to guide new users through some of these features, but on-site training classes are also available.

 

Glass plate

Amorphous glass empty

Glass-Qtz-Si510 overlay

Glass, ZBH-32 and off-planar quartz scans overlayed for comparison

 

 

 

 

 

 

 

 

Several of our customers in the geological industry use standard Si(100) wafers. These can be a great solution, but again have serious drawbacks for some applications. The Si(100) material creates diffracted peaks which are very sharp and therefore easier to model out sometimes, but also very high as the material is monocrystalline. The scan below shows what happens when one tries to run a normal scan across a bare plate. The largest peaks are actually only one or two which have over loaded the detector and caused it to drop out. All of these scans were collected with our SDD-150 which can handle up to 1×10^6 cps, but for the sake of good comparison, we left it tuned as it would be for a standard pattern. The monocrystalline nature of this material causes big problems, but it also allows for a creative solution. See the second scan for the results of the same measurement with the plate angled 1 degree off of theoretical. With this geometry, it’s unlikely this would affect the data quality dramatically, but the offending peaks are drastically diminished.

 

Si-100 wafer

Si-100 empty

Si-100 locked vs unlocked

Si-100 standard vs skewed scan

 

 

 

 

 

 

 

 

 

 

Off-planar Quartz holders have been the industry standard for decades. Historically, these have been made from solid, monocrystalline quartz material cut at a specific angle (6° off the C axis if I’m not mistaken). While these work well, they can be inconsistent. Even some of the OEM holders we’ve tested have shown some peaks which we can’t explain. Talking to some very experienced crystallographers, we find that they’ve had similar experiences.

 

 

Off Planar Quartz ZBH

Off-planar Quartz empty

ZBH-32 empty

ZBH-32 empty

 

 

 

 

 

 

 

 

We’ve been looking for a better answer for several years, but there are few off-the-shelf materials which work as well as off-planar quartz. The ideal answer was to cut solid Si(100) oriented billets such that the face presented to the diffractometer had no d-spacings which would diffract in the normal range of these machines. This is not unlike the off-planar Quartz method, but the starting material is much more consistent and durable. Si(510) offers very low background as well as the consistency of a manufactured product. The new ZBH-32 sample holders from KSA come in two versions, ZBH-25 and ZBH-32 with the latter being ideally suited for rotating stages and low angle work.

 

 

 

 

20141124_161938Our recent sealed sample cell project required a thin covering film to be applied over loose powder before analysis by XRD. We tested a few options for this film as part of the design process and the results were interesting enough that we thought it would be worth dedicating a full post to that data and expanding the range of materials a bit to satisfy our curiosity.

All data was collected on our primary powder system. This is a Siemens D5000 configured with a theta/theta goniometer, automatic anti-scatter and divergence slits, a standard sealed Cu tube (LFF) and our new KSA-XRD-150 detector system. We alternate between a digital phi stage, 40-position autosampler and the standard, single sample stage which was used in these experiments. I had a spare sealed-sample cell available which made it easy to exchange the films without disturbing the sample surface. The design of these stretches the film taught each time the cell is assembled. I’d originally tried to simply lay the film over a side-load holder, but without being tightly held, it would buckle enough that results at low angles were probably affected. A NiO standard powder was used due to its high purity and compositional difference from any of the film materials.

The data clearly shows that Polyimide was the best choice for this application as it resulted in very limited attenuation as well as an extremely minimal increase in background intensity/amorphous scatter. Some of the other patterns were very interesting though.

20141124_161656 NiO CONTROL No film

 

 

 

 

 

 

 

 

 

NiO Prolene copy NiO Mylar copy

 

 

 

 

 

 

 

 

 

NiO Polycarbonate copy NiO Polyimide copy

 

 

 

 

 

 

 

 

 

 

NiO Polypropylene copy

 

 

NiO Prolene

Scotch “Magic” office tape. Adhesive side down.

NiO Scotch packing

Scotch “Heavy duty” packing tape. Adhesive side down.

 

 

 

 

 

 

 

 

 

 

Energy-dispersive detectors have been in use on XRD systems for decades, but have always come with caveats. Low energy resolution, Liquid nitrogen cooling, slow start-up and tedious/cryptic tuning controls have limited their popularity in many applications. Silicon Drift technology solves most of these issues and modern electronics covers the rest. The new KSA-SDD system for X-ray diffraction utilizes a full spectrum EDXRF detector which is fully software tuned. The result is a detection system with high enough energy resolution to match the performance of the traditional diffracted-beam monochromator/scintillation counter combination without the inherent 75% intensity drop. The increased countrate allows for much faster data collection speeds with the same counting statistics. We’ve been using this technology at our in-house testing lab (Texray Laboratory Services) for several months to great effect while we refined the system and are now ready to open it up to all XRD users. Contact us to discuss options for integration into your diffractometer.

SDD-XRD-150 installed on a Siemends D5000TT PXRD system. This is one of the powder systems we operate at Texray-Lab.

SDD-XRD-150 installed on a Siemends D5000TT PXRD system. This is one of the powder systems we operate at Texray-Lab.

The detector mounts directly in place of the original scintillation counter.

The detector mounts directly in place of the original scintillation counter.

 

 

 

 

 

 

 

 

 

 

 

Speed

  • Scanning 3-4 times as fast as the traditional scintillation counter/diffracted beam monochromator yields nearly identical results.
  • Scanning at the same rate results in much smoother scans, greatly improved statistical data and lower limits of detection/quantification.
Novaculite SDD vs SC

Complete scan of Novaculite Quartz with a diffracted beam monochromator and scintillation counter vs the new KSA-SDD-150.

Novaculite SDD vs SC 5 fingers

5-fingers of Quartz scan of Novaculite Quartz with a diffracted beam monochromator and scintillation counter vs the new KSA-SDD-150.

 

 

 

 

 

 

 

 

 

Energy resolution

  • 140eV under ideal conditions.
  • All KB peaks eliminated electronically.
  • W LA1 (8.40 KeV) lines eliminated from Cu KA1,2 (8.04 KeV) scans even with thoroughly contaminated tubes.
  • Common fluorescence energies (i.e. Fe when Cu tube anodes are used) are greatly reduced. (Bremsstrahlung effects are impossible to remove completely)
  • Most PSD detectors offer no better than 650eV. This allows for a great deal of fluorescence energy to pass as well as W LA1 from older Cu tubes.

Low angle scatter

  • The detector mounts in place of the traditional scintillation counter allowing for use of automated variable (motorized) or interchangeable aperture slits to control angular resolution. Scans starting from 0.5 degrees 2? are possible with the proper slit arrangement just as they are with the scintillation counter. The user controls the intensity vs angular resolution of the scan based upon the ideal conditions for their work rather than the limitations of the hardware.
  • Position sensitive detectors are wide open by design which necessitates knife edges over the sample and additional mechanical aperture plates to block air scatter at low angles. Closing off the detector limits the useable channels and reduces the benefit of these detectors dramatically.
Novaculite SDD vs SC low angle

Minimal low angle scatter due to the use of standard aperture slits.

Novaculite SDD vs SC Cu KB1 and W LA1

Cu KB1 and W LA1 energies diffract from the 100% peak of Novaculite in between the two primary peaks shown here. Tests with a severely contaminated tube showed no W LA1 passing through the discriminator.

 

 

 

 

 

 

 

 

 

Truly zero maintenance design

  • No delays – The detector is ready to collect data almost as soon as power is applied.
  • No external cooling – Air backed Peltier cooling eliminates the need for water circulation and/or liquid nitrogen.
  • Zero maintenance vacuum design eliminates reliance on an ion pump/backup battery.
  • 12 month warranty against hardware failure under normal use.

Versatility

  • The Digital Pulse Processor (DPP) includes a usb interface allowing for adjustment and refinement should they be necessary for a particular application. With optional software, full quantitative EDXRF analysis can be performed.
  • Compatibility with grazing-incidence attachments and parallel beam optics for analysis of thin films.

 

The detector can be set for any common XRD anode (energy) easily. Multiple energies may even be configured to allow for use with various anodes without the need for additional hardware. We specialize in Siemens (now Bruker) XRD and WD-XRF instrumention and have installation kits ready for the D500, D5000 and D5005. The output is a standard BNC cable with a 5V square pulse output which is standard across every manufacturer we’ve worked with. Kevex and Thermo Si(Li) detectors used this same output.

Please contact KS Analytical Systems for a quote.

 

Posted by: In: Uncategorized 25 Aug 2014 0 comments Tags: , , , , ,

The most common practice in powder XRD is to simply fill the recessed well of a sample holder with finely ground powder and start collecting data. That works for a great many users, but everyone is eventually faced with a more complicated situation at some point. At Texray, odd samples and special requirements are the norm. The photos below represent some of the common and not-so-common needs we’ve come across. Many of these are one-off designs fabricated by KS Analytical Systems.

20140825_143140The top row shows the three most common holders we see with various well depths. These are almost exclusively used for loose powders. The goal is to get the surface of the sample into the plane of diffraction with as little of the holder in the beam as possible. The plastic material has a very high scattering coefficient which creates a hump in the data around 13 degrees 2Theta. These are all designed for the 40-position sample changers from Siemens (now Bruker).

The second row gets more interesting with a special holder for high volume instruments. This was designed for magnetic handling and worked great as long as you don’t mind the low angle scatter problem of the plastic and aren’t working with ferrous powders.

The middle is one we use for collecting data from membrane filters. These are notoriously hard to hold down with any precision so they get mounted from the rear and held against a “lip” to keep them both flat, and in the plane of diffraction. They work wonderfully.

Next we have a simple side load sample holder. I’m a big fan of these and use them anytime I’m running loose powders on a single sample stage. It allows the user to load with a very smooth top surface that’s perfectly flat without creating any preferred orientation. Preferred orientation is frequently caused by pressure being applied to the basic top-load holders in an effort to get a flat surface. It is to be avoided whenever possible. Notice that the holders are all Aluminum at this point. Most custom holders are Al or a combination of Al and stainless steel depending upon the special properties desired.

The last row are good examples of odd-shaped sample holders. When you’ve got a rock with one flat surface or a little chip of some material, you still need to keep it in the plane of diffraction. The user simply places a ball of clay in the middle of the holder, the sample goes on top of that and then a glass plate is used to crush the clay (with the sample on top) down such that everything is in plane with the elevates posts. These posts interface with the machine to define the plane of diffraction right across their surface, thus the sample is right where it needs to be without any complicated engineering or microscopic adjustments.

 

Custom holders for a D500 user. Side load as well as top-load in Al.

Custom holders for a D500 user. Side load as well as top-load in Al.

Side load precision without the possibility of powder falling out at low angles.

Side load precision without the possibility of powder falling out at low angles.

Vacuum holding is common when working with semiconductors or other materials with very consistent thicknesses.

Vacuum holding is common when working with semiconductors or other materials with very consistent thicknesses.

We needed to keep our standards in our desiccator cabinet as well as store membrane filters long-term. Custom laser-cut shelves make this easy.

We needed to keep our standards in our desiccator cabinet as well as store membrane filters long-term. Custom laser-cut shelves make this easy.

A typical run of custom sample holders for a high volume XRD operation. This user actually has a custom loading tool that allows for multiple holders to be filled simultaneously.

A typical run of custom sample holders for a high volume XRD operation. This user actually has a custom loading tool that allows for multiple holders to be filled simultaneously.

This is a completely custom stage designed to hold a large thrust bearing race such that the bottom of the groove is in the plane of diffraction for retained austenite and residual stress measurements.  The bearing is held in place by magnets.

This is a completely custom stage designed to hold a large thrust bearing race such that the bottom of the groove is in the plane of diffraction for retained austenite and residual stress measurements. The bearing is held in place by magnets.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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A large part of our business at KS Analytical Systems is refurbishing and reselling WDXRF and XRD instrumentation. We specialize in Siemens and Bruker models because, and I can’t stress this enough, they last. Siemens was 20 years ahead of their time with features like full computer automation, interlocked radiation housings (not just an enclosed beam path) and independent axis control coming standard on most systems. The D500 may well be the most reliable powder diffractometer ever built and for most of our history, it’s outsold all other models of XRD and XRF combined. Most users are simply performing basic powder scans with many running the optional 40-position sample changer, but I always get excited when I find someone pushing the limits of the platform.

Several years ago I was approached by a new professor at a major American university about purchasing a refurbished Siemens D500 XRD. He’d been seriously considering a new instrument from one of the big-three OEMs, but chose to focus on the D500 due to its reputation for low cost of ownership, versatility and nearly identical resolution/intensity to the new system he’d been looking at. It’s been a few years since that unit was delivered and I’ve been very impressed with the improvements that have been made.

The first step was to bring the software up to date with a complete package from Materials Data Inc. (MDI). This included Datascan 5.0 for instrument control and data acquisition as well as the flagship Jade 9.5 analysis package. Whole pattern fitting (Rietveld), semi-automatic phase ID (Search/Match) and a host of other advanced quantitative and modeling options are included. Jade 9.5 is modular and can be purchased with any combination of these options. I’d estimate that 70% of the XRD systems we sell go out with some level of MDI package. We’ve been working with them for 20 years now and have never heard anything other than glowing praise for their excellent products and support. One key feature of Jade is that it was designed to be a universal analysis solution from the ground up so there’s never a problem opening any of the OEM file formats. It’s much easier to justify the cost to upgrade your software when you know it will integrate seamlessly with any other data or instruments you may encounter. Contact KSA if you’d like more information on this.

Jade 9.5

This is Jade 9.5. You’ll notice that it’s a much different interface than the Jade 2010 program I usually use. This option is modular with available plug-ins for all the higher level functions of Jade 2010, but 9.5 is perpetually licensed.

Virtual XRD

This is actually the VirtualXRD program that comes along with Datascan. I don’t use it often, but some of my users run extremely long count times and predicting the affect of a parameter change could save them days of experimentation. It’s a great tool even for users running simple 1 hour scans.

 

 

 

 

 

 

 

 

 

 

 

The next step was more hardware based than anything else. The independent axis control of the D500 (in Theta/Theta or Theta/2Theta configurations) allows for both rocking curves and grazing incidence scans. With the goal of analyzing thin-films in mind, we upgraded the D500 with a grazing incidence attachment. These are designed to minimize scatter while the sample is held at a shallow (usually 3 degrees) incident angle and the scan is performed with the detector alone. The attachment consists of a long collimator coupled with a simple monochromator just before the detector. We’ve performed some rather intense studies with one of these at Texray and were very impressed with its performance. In fact, we use it whenever practical even though we have a dedicated parallel beam optics system in the lab as well. It was about time for a new tube so a new, ceramic Cu long, fine focus tube was included in the upgrade.

Ceramic XRD tubeGrazing incidence attachment

 

 

 

 

 

 

 

 

 

 

Some additional software solutions were developed on-site to facilitate XRR (X-ray Reflectivity) measurements around the same time. I confess that this is not something I’m personally very familiar with, but it seems fascinating. It involves scans at extremely low angles which can require caution since one is working with a very nearly direct beam.

The last upgrade he made is actually the one that most impressed me and the one I had absolutely nothing to do with. In an effort to further expand the capabilities of his instrument, he purchased and installed an energy dispersive detector with an integral digital pulse processor (DPP). Clever mounting and some experimentation allowed him to perform EDXRF elemental (qualitative AND quantitative) analysis on samples while using the D500s X-ray tube as the primary emission source. The flexibility of the D500 platform even allowed him to control the effective layer depth by adjusting the incident beam angle. Since his application involved analysis of a thin film coating, he set the goniometer to a low angle to minimize penetration depth and substrate interference. After seeing how well this worked, I immediately started working on a similar upgrade that we could offer to all our current and future XRD users. I’ll detail my early progress in the next post.

All of the powder XRD (PXRD) systems we work with use either manually interchangeable aperture slits or automatic (stepper motor driven) slits to control divergence and scatter. One of the most common questions I hear from new users is “What is For the ideal slit arrangement”. While I realize that there are many instruments out a there with “one-size fits all” slits, the D500, D5000, D5005 and D8 optics are what I call “Research Grade”. This means that they can be adjusted and tuned for  particular application to maximize effects that are desirable and minimize those which are not. One of the most common reasons to change the anti-scatter and divergence slits is to reduce scatter over the sample at low angles. This scatter is the primary limiting factor for users who want to see diffracted peaks at very low angles. At Texray, we offer instrument time (data collection) as one of our services and have received requests for starting angles as low as 1 wholesale nfl jerseys degree 2theta so it occurred to me that now would The be a phase good time to cheap jerseys online collect some reference data and answer this question once and for all.

The image on the left shows the effect that the anti-scatter and divergence slits have on low angle scatter. The image on the right is Puppy’s of the two primary reflections of quartz (Novaculite) with the same slits. Note the intensity Welcome loss. The benefit of automatic slits is that they can be set very small at the beginning of the scan and gradually open up throughout the angular range. Very few users need that kind of flexibility, but since we’re talking about slits, it wholesale mlb jerseys bears mentioning.

Low angle scans with various slits

This data was collected with matched slits set at 0.2mm, 0.6mm, 1mm and 2mm. These correspond to practical starting angles of 0.6, 0.9, 1.4 and 2.5 degrees 2theta respectively.

Low angle scans with various slits PEAK COMPARISON

Looking at the actual peaks, you can see the affect the smaller slits have on the rest of the data. These were collected without the benefit of a diffracted beam monochromator and Phase with the primary soller slit removed. Neither of Topic these factors would have a dramatic impact on the result, but the lack of a primary beam soller slit explains the asymmetrical peak shape in the second scan range pictured.

 

 

 

 

 

 

 

 

 

 

 

 

XRD work is categorized into two major groups. Single crystal and powder analysis. While single crystal work is usually highly customized to particular applications and involves a largely unique hardware set, powder (PXRD) work covers a broad range of applications. Many of which can be performed without any special hardware at all. Perhaps it would be more accurate to call it “Randomly oriented small particle” diffraction. Somehow I think “ROSPXRD” would be slow to catch on. At the risk of oversimplifying the options, I’d like to take a few posts to showcase some of the more common analyses which can be performed with a basic PXRD system and perhaps wholesale nfl jerseys a few that require minimal additional attachments.

This is an example of a Bruker D8 Advance configured in its most basic PXRD state with only a scintillation counter, sample stage and source.

This is an example of a Bruker D8 Advance configured in its most basic PXRD state with only a scintillation counter, sample stage and source.

This is the same D8 base instrument configured for single crystal XRD. Note the Chi, phi, XYZ stage, area detector (2D) and Goebel focusing mirrors.

This is the same D8 base instrument configured for single Damen crystal XRD. Note the Chi, phi, XYZ stage, area detector (2D) and Goebel focusing mirrors.

 

 

 

 

 

 

 

 

 

 

 

My last post involved a basic phase identification and this seemed like a great place to start. Most PXRD users are asked to identify some unknown bit of скачать corrosion, rock or contaminant at some point. I once took a shot at something which later turned out to be sewage sludge ash. I have no idea what they hoped to find in that. Exotic, mundane or distasteful, the most basic XRD can collect the necessary data to perform this analysis. Phase ID is usually the first step most users take toward more advanced software. In addition to the simple pattern analysis features that usually come standard, you’ll need an engine designed to search one of the many commercial or open-source databases available. The ICDD, NIST and wholesale mlb jerseys AMCSD are probably the most popular with several others on the fringe. There are even user-developed databases which are usually compiled in a particular lab to cover the range of phases they expect to see based on their product or application.

Limiting the search to categories of phases which are likely to be present Broker greatly improves the relevance of the results list. There’s obviously no reason to search through a huge list of minerals when trying to identify a metallic oxide coating. Hit lists can also be refined based on data from other sources such as qualitative elemental analysis. We use our WDXRF systems and the built in elemental filter in Jade to trim the options substantially.

Any good search/Match engine will have support not only for multiple databases, but also offer the option to limit your search to certain subfiles which are group my material categories.

Any good search/Match engine will have support not only for multiple databases, but also offer the option to limit your search to certain subfiles which are group my material categories.

Semi-quantitative or simple qualitative elemental data can be used to eliminate a large percentage of erroneous hits so the analyst can focus on only pertinent options. We prefer to bundle an XRF scan with any Phase ID project.

Semi-quantitative or simple qualitative elemental data can be used to eliminate a large percentage of erroneous hits so the analyst can focus on only pertinent options. We prefer to bundle an XRF scan with any Phase ID project.

 

 

 

 

 

 

 

 

 

 

Isolating the valid hits from erroneous is where experience comes into play. Non-ideal particle size, preferred orientation and crystallographic imperfections can make the process quite difficult. Relative peak intensity ratios, peak width and sometimes even the complete absence of ID a particular peak which would theoretically be present all present opportunities to gain additional insight. Sometimes this is relatively easy as in the case I presented in the previous post, wholesale nba jerseys but other situations are not so simple. These difficulties are amplified in the case of low concentrations and complex mixtures.

This is  a great example of Phase ID the way we all wish it came out. The peaks are sharp, intense and located right on their theoretical angle.

This is a great example of Phase ID the way we all wish it came out. The peaks are sharp, intense and located right on their theoretical angle.

This is an example of something a little harder to nail down. Overlapping peaks, several additional phases and a highly imperfect sample. Refining the options based on external measurements and in depth sample prep make the difference between success and failure in cases like this.

This is an example of something Texray a little harder to nail down. Overlapping peaks, several additional phases and a highly imperfect sample. Refining the options based on external measurements and in depth sample prep make the difference between success and failure in cases like this.

 

 

 

 

 

 

 

 

 

 

XRD pattern analysis has come along way in the last 40 years and most of the major improvements have come on the heels of increased computing capability which enables us to perform exhaustive iterative calculations on complex patterns quickly and at comparatively low cost. However, there is nothing on the market as of now which has made an experienced analyst obsolete.

 

I stumbled into Dondero’s Rock Shop a few weeks ago and struck up a conversation with the owner. He had been interested in geology all his life and was now operating a very nice shop in North Conway, NH with just about every type of mineral one could imagine on display. It was a great opportunity to have an expert identify a few specimens my boys had collected the previous day and he was more than happy to help. These were very large single crystals of relatively common minerals, but it was obvious that experience makes all the difference when one is trying to identify them by sight. I offered to return the favor by collecting XRD data on anything that ever managed to stump his well cheap MLB jerseys trained eye and he immediately brought out an interesting sedimentary formation which he’d sliced into cross to sections. He had been very curious about its composition and I brought home a sample. My wholesale MLB jerseys technical expertise is primarily in the hardware we use at Texray while the real science is handled by other, more highly skilled hands, but this seemed like a fun little project and good practice if nothing else.

Geological samples are particularly difficult to analyze by XRD as they contain various defects which are difficult if not impossible to model based on theoretical data. Our precious Rietveld refinements roll off of this type of data like water off a ducks back all too often and we’re left wondering how on earth this mud could be mistaken for moon rocks. As wonderful as Erlebnis Rietveld is in well-trained hands, we tend to rely much more on comparative data when we’re working with this type of sample. We can thank Dennis Eberl of USGS in Boulder, CO for bringing RockJock into the world to solve exactly these types of problems. RockJock is relies on what’s called RIR. That is Relative Intensity Ratio analysis to cheap nfl jerseys provide both qualitative and quantitative results. The  algorithm has been massaged into a number of commercial products in an effort to improve the user interface and add additional functionality, but the core of all that is still readily available on the internet for anyone interested to download. If you’re interested in something a little more user friendly, we offer ClaySim from MDI.

To the left you can see the data I collected after mild grinding. It’s not uncommon to spend several hours collecting data before it’s adequate for quantification or other advance analysis, but as we’re only interested in qualitative phase Program ID, this will more than suffice. I was quite surprised to find only two major phases present since the sample clearly shows four distinct layers with completely different coloration. The scan actually ran all the way to 120°2Θ, but the “action” is mostly concentrated at the lower angles. Hardcore geologist actually push the lower limit all the way down to 2.5°2Θ in an effort to catch a few illusive peaks. The analysis program you see here is MDI Jade 2010. It’s their flagship product and for good reason. Almost all of our users are running some form of Jade for their wholesale NFL jerseys analysis and all have had nothing but glowing praise for it.

So it appears that the mystery rock was actually little more than Quartz and Dickite. It’s possible that there’s a bit of Kaolinite mixed in there as well, particularly because Dickite and Kaolinite share a chemical composition. The real fun started when I let Jade loose using a feature called “One Click Analysis”. This is as close to a “black box” as XRD analysis will ever get. With good data collected on a solid, well-aligned XRD, this little button can provide impressive results with no user input at all. It’s not the magic bullet for every situation, but in Face this case, it recommended yet another phase with the same chemical composition as Kaolinite and Dickite. Nacrite. Adding this into our phase list improved the difference pattern and cheap NBA jerseys allowed Jade to model nearly every bump in the pattern.