This is the MiniFlex II the latest model of the MiniFlex series of benchtop powder diffraction systems. Hundreds of units have been sold since the first MiniFlex was introduced in 1973. Click on the right arrow to learn more about this revolutionary benchtop XRD system.
Powder diffraction is used for four primary reasons.
The first is phase identification, also known as qualitative analysis. For example, rutile and anatase are two different forms of titanium oxide that are indistinguishable using XRF techniques. Because their crystal structures are different, however, XRD can easily determine which form is present in a sample.
In quantitative analysis, the concentration of various components in a mixture are determined using the RIR (relative intensity ratio) and standard reference values.
Powder diffraction lets you study a materials polymorphism. Different crystal structures of a material, for example, the dimetric (tetragonal) and hexagonal forms represent different polymorphs of that material. Since powder diffraction measures all the crystal structures present in a sample polymorhism can be detected and quantified.
The percent crystallinity of a sample can also be measured. Crystalline and non-crystalline components of a sample scatter X-rays differently. Powder diffraction measures each type of scattering and as a result can quantify each, leading to an understanding of how much of the sampe was crystalline.
The MiniFlex II can perform all of these routine powder diffraction applications and a lot more.
The MiniFlex II is composed of three basic components: the X-ray tube, the sample and the detector. During a phase identification experiment, the angle between the incident X-ray beam, the sample and the detector are changed gradually, the detector moving at twice the speed of the sample.
X-rays are diffracted at specific angles unique to a particular compound. The resulting diffraction pattern is plotted out with the diffraction angle along the X axis and the relative intensity along the Y-axis.
Software compares the experimental diffraction pattern to standard reference patterns for nearly 90,000 compounds stored in a database, in a process similar to the forensic comparison of unknown fingerprints to those stored in criminal or other database. A diffraction pattern is as unique to a substance as a fingerprint is to a person.
The above photograph focuses on the incident beam side of a MiniFlex II. The beam produced by the X-ray tube passes through a 5° soller slit and a 1.25° divergence slit. The sample holder is shown inserted into the sample stage.
The shutter is interlocked with the door—X-rays are only directed at the sample when the door is closed and the shutter is opened.
This is the receiving side of the MiniFlex II. The 150 mm radius goniometer is vertical and the X-ray tube is stationary. Both the sample and the detector move to achieve the desired diffraction geometry. Behind the Ni Kβ filter pictured above, there is a 1.25° scattering slit, a 5° receiving soller slit and a 0.3 mm receiving slit, all pre-installed and aligned.
A scintillation detector, the final component in the X-ray beam path, detects the X-rays.
For a typical diffractometer acquisition there are several burdens to be overcome, some of which arise even before the instrument is installed. Most X-ray diffractometers are large; therefore it is necessary to find sufficient space for the new instrument. It may even be difficult to get into the building. In some cases walls need to be removed or doors taken apart. If the X-ray lab isn't on the ground floor, there are even cases when a crane may be needed to get the system to its new home. Renting a crane was probably overlooked in the budget!
General XRD instruments require three-phase 220 volt power, which isn't standard in many locations, Diffractometers have historically been expensive, and an application for this type of instrument might not be approved. Since the cost of a MiniFlex II is low compared to a typical diffractometer, it might be possible to purchase the instrument with money left over from operating budgets or other grants.
Worries don't end after the instrument has been purchased and installed. Users must now figure out how to collect data, and many XRD instruments require numerous conditions to be selected before starting the first measurement. Should focusing or parallel beam optics be used? What power should the X-ray generator operate at? How wide should the soller, DS and RS slits be set? Beginners often have difficulty determining the correct values for these parameters.
In an academic setting, professors are faced with training new students in the operation of the system year after year. For more complicated XRD systems, some users may not grasp the operating procedures, need help from a dedicated staff member, or worse, run the system incorrectly.
Feeling stressed about buying an XRD instrument? Don't The MiniFlex II addresses all of these problems.
First, it is a benchtop system. It is much smaller and lighter than a general XRD diffractometer—it can be installed in minutes anywhere household 100-110 V power is available.
Secondly, it is easy to use. The measurement procedure is simple—users are up an using the system productively in minutes, not days or weeks.
Finally, the MiniFlex II is inexpensive, to purchase and to own. It will fit your budget and bring advanced powder diffraction capabilities to your organization.
Here is a typical X-ray laboratory. Not a very organized place-you've probably seen labs like this before. At first glance, it appears that there is no room for a new XRD instrument. However, the MiniFlex II is only 560 mm × 665 mm × 375 mm (W × H × D). Small enough to set up on the white table in the corner of this lab
Maybe the previous picture doesn't explain it clearly enough. Here is a compact car. The MiniFlex II is small enough to fit in the back of this small vehicle. If you can secure standard 110V electric power (sorry, you can't run it from the cigarette lighter!) and 2 gallons of water, you can run it anywhere. It's no longer necessary to send samples back to the lab. Get your results faster!
Remember that crane that you might need to install your XRD system in the lab on the third floor? No such worries with the MiniFlex II. At 75 kg, you can move it through the halls with an ordinary cart ordinarily transporting books or A/V equipment. Two adults can lift it on a lab bench, a process made easier by four metal lifting shafts that can be screwed into holes on either side of the diffractometer. Once the MiniFlex II is in place, these rods can be removed and stored in case you decide to relocate the diffractometer or take it out into the field. It's that easy.
What about those heavy demands for utilities? As we said earlier, general XRD instruments require three-phase, 220 V power and draw 30 amps. The MiniFlex II is much more modest in its requirements: 100-110 VAC, 15 A. You can plug it into any standard wall outlet. Anywhere! And since the total power output is only 450 W, enabling an air-cooled water chilling unit.
The MiniFlex II is easy to use. You don't need to worry about tube power settings, tube lifetime, or measurement geometries. You don't need to consider aperture values for the soller slits or the RS and DS slits, issues that confuse many beginners and make little difference in most cases for the measurement. With the MiniFlex II, these conditions are set at the most commonly used values and fixed.
By now, you're probably wondering about the quality of the data produced by the MiniFlex II. As these next slides will demonstrate, the MiniFlex II performs powder diffraction measurements at the same accuracy as full size machines. This slide demonstrates the peak profile of 1% anatase in magnesium oxide. Even at such trace levels, the anatase peak can be easily detected. The high sensitivity of the MiniFlex II is due, in part, to the 150 mm goniometer radius, allowing excellent performance.
Two sample attachments are available for the MiniFlex II. First, for quantitative analysis on samples with uneven particle sizes, a specimen rotation attachment is available to suppress the change in peak intensity ratio in the diffraction pattern caused by preferred orientation. Also available is the ASC-6 six-sample changer that enables six samples to be rotated at different speeds.
To mount one of these attachments, set it into position and tighten one screw. Then insert the power plug into the attachment jack. For other XRD instruments, θ realignment is required after a sample attachment is installed. No alignment is required with the MiniFlex II.
Let's look at some applications you can perform with the MiniFlex II.
Example 1 is the identification of the production site of iron ore. The presence of certain impurities can be used to uniquely determine the production site of the iron ore. Detecting these impurities is essential during the steel making process.
This example demonstrates the ability of the MiniFlex II to perform quality control during production of pharmaceuticals. The sample of interest is theophylline, which can crystallize in either in the pure form or as a monohydrate. Because they have different physical properties (stability, melting point, solubility), the bioavailability for these two polymorphs is different. Pharmaceutical compounds can change into different polymorphs during grinding, tablet manufacture or other production processes.
XRD is the simplest and most important method of detecting the existence of polymorphs. The lower profile is of an equal mixture of theophylline nonhydrate and the monohydrate. The upper scan shows how that 2% contamination of the monohydrate can be detected in a bulk sample that is primarily the nonhydrated form.
This example demonstrates a quantitative analysis of TiO2, a substance that is widely used in white pigments, electronics materials, optical catalysts and UV absorbents. It exists in three polymorphs: rutile, anatase and brookite. The efficiencies of rutile and anatase as optical catalysts are different, so a method to determine the rutile:anatase ratio is needed.
The quickest way to do quantitative analysis in XRD is to determine the RIR (Relative Intensity Ratio).
The profile above is of a prepared mixture of rutile and anatase in a 3:1 ratio. Using Jade software to apply profile fitting algorithms, integrated intensities of several peaks were determined. The result showed rutile at 71.6 wt% and anatase at 28.4 wt%, which are approximately consistent with the ideal values of 75% and 25% respectively. This method is widely used as a simple, quick way to perform quantitative analysis.
In conclusion, the MiniFlex II benchtop diffractometer is easy to use, compact, and portable. Installation is simple, taking less than an hour. Users will be able to fully understand and use the system in minutes. Data quality is identical compared to larger units for most samples.
MiniFlex II. Perform XRD experiments inexpensively; Produce XRD results easily; Predict your success confidently.
