X-Ray Diffractometer: User Guide

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Manual Information

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The goniometer has 2 circles: the theta (θ) circle, which sets the sample position, and the 2θ circle, which moves the detector. The position of the X-ray tube remains fixed. The goniometer center is defined by the concentric circle axes.

Sample Holders

Sample holders for powdered XRD samples are steel or steel with a silicon or quartz spacer. The selection of a sample holder depends on the volume of sample to be analyzed.

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The VANTEC-1 detector features the fastest simultaneous recording of XRD patterns within a wide 2θ angular range. For powders, measurement time is reduced by a factor of up to 100 in comparison to other detectors.

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The instruments in the lab need to be turned on in this order: (1) HASKRIS and (2) D4. The HASKRIS cools the water supplied to the D4 to prevent the X-ray tube from overheating. Turning the D4 on prematurely will damage the X-ray tube.

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Figure 1. HASKRIS Control Panel. (A) Actual temperature. (B) Set temperature. (C) On/Off switch. (D) Flow meter. Image Removed

Procedure

1. Flip the "On" switch (Figure 1C) to the HASKRIS and the water in the tank will begin to cool. The water temperature needs to reach 55°F (Figure 1A).
2. Flip the ON switch (Figure 2A) on the side of the machine.
   1. The solid green "Low Voltage Ready" light (Figure 2F) turns on.
   2. You will hear several beeps and the "System Activity" light (Figure 2D) will start flashing green.
3. Press the "High Voltage Enable" button (Figure 2B).
   1. The "System Activity" light turns green.
   2. An orange "High Voltage Ready" (Figure 2E) light will turn on.

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Figure 2. Side control panel on D4. (A) Power On/Off. (B) High voltage enable button. (C) Alarm light. (D) System activity flashing light. (E) High voltage ready light. (F) Low voltage ready light.

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4.      Go to the front of the machine and press the green circular button. This enables the mains power and activates the sample handler (see Figure 3).

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Figure 3. D4 top control lights.

5. Turn the “Generator Power” key to the right for a few seconds and look at the lights on top of the D4 (Figure 4)

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Figure 4. D4 Front control panel.

6.   When the

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“Alarm” light turns off and the

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“Ready” light turns on, release the key back into its middle position. The top of the machine should have a solid orange

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“Ready” light and a solid green

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“On” light. 

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7.    If this is the first time in 24 or more hours that the D4 has been turned on, the X-ray tube now needs to be conditioned. Go to the Maintenance section under Tube Conditioning for instructions

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Sample Preparation

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Solid samples are prepared for X-ray diffraction by grinding, which depending on the sample matrix, the size of the sample, and/or quantity of prepared material needed can be accomplished by several different methods.

Drying Samples

Freeze-dry sample(s) for at least 12 hours before grinding. If the samples still feel cold when removed from the dryer, the samples still have moisture in them and need to dry longer.
The freeze dryer is comprised of a sample "bell" chamber and a Labconco freeze-dryer. On the bell are two valves, as shown in Figure 5. Each valve has an "Open" and "Closed" position. The top valve controls the vacuum inside of the bell, and the bottom valve controls the air flow between the cooling coil and bell. A valve parallel with the tube is open and allows air flow; a valve perpendicular with the tube is closed. In Figure 5, configuration A (closed) will hold a vacuum, but configuration B (open) will not.
Figure 5. (A) Freeze dryer bell valves in closed position. (B) Freeze dryer bell valves in open position.
To freeze-dry samples,

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1. Cut open the sealed sample bags and fold the top edge over to keep the bag open.
2. Take the top of the bell off of the dryer and arrange samples in the bell, making sure no sample bags are pinched closed.
3. Close the vacuum valves slowly so that you do not cause a large rush of air to blow the samples around. Figure 5A shows the configuration to dry samples and Figure 5B shows the configuration for loading and unloading samples.
4. Set the freeze dryer to resemble the settings shown in Figure 6 and flip the "On" switch located on the right side of the machine.
5. Press the "Auto Refrigeration" button (Figure 6A) and then the vacuum button (Figure 6B). The temperature will start to drop and the vacuum pump will turn on.
   1. When the temperature drops to –40°C, the vacuum is created in the bell and the pressure drops.
   2. Expect the temperature to be between –42° and –52°C and the pressure to be ~0.350 mBar.
   3. The indicator lights (Figure F6D) show how the cooling and pressure reduction are progressing. When all indicator are lights are on the freeze dryer is at its peak performance.
   4. If there is an error the red "Alarm" light will turn on. Press the "Menu" button (Figure F6C) to view it and clear it
6. Figure 6. Freeze dryer control panel. Image Removed After samples are dry, slowly open the valves to let out the vacuum in the bell. Remove the samples from the bell and store them inside the desiccator until they are ready to be ground to prevent reabsorption of moisture.

Grinding Solid Samples

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Figure 6. Freeze dryer control panel. 

Grinding Solid Samples

There There are three primary ways to grind samples:

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Mortar and pestle is the most common method. Below, each method is outlined.
Mortar and Pestle
Choose the appropriate mortar and pestle size (large or small) and place it on the counter. Obtain a glass slide, a sample holder, and a scoopula. Clean all items after each use with isopropyl alcohol and a KimWipe.
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Figure 8: Mortar and pestle sample preparation set up. Image Removed 

Pour sample into the mortar and grind the sample with the pestle. When finished, the sample should be the consistency of talc powder. Test the sample by taking a pinch and rubbing it on your skin. If the sample feels gritty, it needs to be ground more. If the texture is good and the sample looks homogenous, you can pack the sample into a sample holder to be placed in the D4.
Mixer mill

 There are two mixer mills located in X-Ray Prep. Both mills operate very similarly but do have slight differences. The 8000 is featured on the top and the 8000M on the bottom. 

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Figure 9: 8000M mixer mill. (A) Safety latch (B) Minute timer (C) Seconds timer (D) Start button (E) Pause/Stop button (F) Timer countdown LCD display.

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Figure 10: 8000 mixer mill. An older simplified version of the 8000M. Featured are the safety latch, timer dial, and start/stop button in the middle of the dial.
Image RemovedImage Removed There are two mixer mills located in X-Ray Prep. Both mills operate very similarly but do have slight differences. The 8000M is featured on the left and the 8000 on the right.


The main difference between the two mixer mills is the timer. The 8000M timer uses 2 buttons to adjust the minutes (Figure 9B) and seconds (Figure 9C), 2 separate buttons to start (Figure 9D) and manually stop (Figure 9E), and counts down time on the LCD display (Figure 9F). To operate the 8000 mixer mill, turn the knob to the desired time and press the "Start" button in the middle. That button will also stop the mixer mill. The dial does not move automatically, so if it is turned to 5 minutes it will stay there. The dial does not need be set back to 0 to work.
Grinding Vessels
There are three types of grinding vessels available: alumina ceramic, tungsten carbide, and hardened steel (Figure 11). Tungsten carbide and steel vessels are better for more robust grinding, and alumina ceramic is better for minimizing contamination. Check with the Science Party to see which vessel type is preferred.
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Figure 11: Three types of mixer mill grinding vessels. Image Removed

Each grinding vessel has its own components. Parts should not be shared amongst the different types of vessels. Combining pieces made of different materials can cause severe damage to the pieces involved.

Below are the components for each type of vessel. The steel (Figure 12) and tungsten carbide (Figure 13) both have a vessel body with attached lid and one separate lid that is screwed on. Cross-threading is very easy with these containers, so be very careful when screwing on the lid. Also note that the steel container has an O-ring, whereas the tungsten carbide does not. The alumina ceramic vessel (Figure 14) is assembled differently than the other two vessels: two cork rings are placed inside each lid, and the lids slip onto either side of the vessel body.

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Figure 12: Steel vessel components.
 (A) Lid
Lid  (B) Container (C) Steel Grinding Ball (D) O-Ring 

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Figure 13: Tungsten carbide vessel.
(A) Vessel container (B) Lid (C) Tungsten carbide grinding ballFigure ball

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Figure 14: Alumina ceramic vessel components.
(A) 2 cork rings (B) Vessel body (C) Alumina ceramic grinding ball (D) 2 lids Image Removed

Label the vessel with a small printed label of the sample it holds. After the sample is ground, transfer that label to an 8 or 16 mL snap cap bottle that will hold the powder.

Loading the Grinding Vessel into the Mill
Put your sample inside the vessel. The material should be approximately the size of a pea to prevent any jamming and to ensure all pieces are ground up. Place 1 to 2 grinding balls inside the container. Tungsten carbide and steel vessels can take up to 2 balls. The alumina ceramic vessel is more brittle and 1 ball is recommended. Finish assembling the grinding vessel and open the lid to the mixer mill.
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Figure 15: Inside the 8000M mixer mill.
Highlighted  Highlighted is the sample holder clamp that holds the grinding vessels, the primary lock, and the secondary lock. Image Removed

Hold the grinding vessel between the sample holder clamps (Figure 15), flush against one side. Still holding the vessel, start turning the primary lock. The holder will begin to clamp down on the sample. When the vessel is secured, you can remove your hand and continue tightening the primary lock until the sample is firmly gripped. Then tighten the secondary lock until it feels firm. Check the vessel to make sure the lids are resting flat on the clamps. If the vessel is ajar inside the clamp, when the motor starts the vessel can start grinding away at itself or fly loose into the machine.

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Shatterbox
Shatterbox vessels are not commonly used for powder XRD samples. Please refer to the ICP Prep User Guide for instructions for using the shatterbox.

Preparing Sample Holders for the D4

There are three ways to load a sample holder: front load, side load, and backload. Front and side loading methods uses the same sample holders and back-loading uses unique holders. Front Loading is the most common method. Back and side-loading are ideal for reducing preferred orientation and should be used over frontloading if preparing samples for semi quantitative analysis. 

Collect Enough Material to Fill a Sample Holder

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This method will leave a small gap in the well of no powder. For this packing method it is ok and the material should be tightly packed in.

Back-Load samples

Back-loading samples is a preparation method to reduce mineral orientation. This method may be desirable for quantitative XRD
Figure 40. Back-loading smaple holder pieces. A. Sample Ring B. Back piece C. Funneling piece D. Tapper There are 10 back-loading holders. The holder has an empty ring and backing piece that snaps in from behind (Figure 40). There are also two loading pieces. One piece helps funnel the powder in and the other taps down the powder into a flat surface.

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Figure 25: EVA diffractogram.
The arrow points to the Background Subtract tool.

1. Strip Kα₂ and Append (Figure 26).

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Figure 30: Data Tree panel Scan Area list.

1. Open the QAQC corundum standard Equipment Verification 3.3.xls Excel spreadsheet.
2. Enter your name and date and select "Vantec-1" for the detector.8. Enter the following values into the spreadsheet:

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Regularly check the filter in the HASKRIS tank. If there is a lot of debris it may be necessary to drain the tank and refill with DI water only. The filter can be sprayed off in a sink taking care not to puncture the screening. If the water flow rate to the system begins to drop close to 4 L/minute it may mean there is a clog in the quick disconnect points behind the back panel or the sprayer head in the X-ray tube housing needs to be cleaned.

Checking QAQC Files

Compare the QAQC corundum scan with past results. X-Ray Tubes deteriorate. When the intensity of the Corundum scan is approximately half of what it was at the date of installation it is time to replace the tube. Check the scans for Tungsten lines, if any appear it is time to replace the X-Ray tube even if the intensity is still acceptable.

Making a Parameter File

A parameter file tells the D4 the conditions that a sample will run under. This is a DQL file made with the XRD Wizard program. The parameter file includes scan settings, scan parameters, generator settings, and beam optics. Some of these settings are constant because they are hardware features of our D4.
To start, double-click the XRD Wizard icon on the Desktop.
An empty gray screen will open. There options on the top bar to either open a preexisting file or open a completely blank sheet. It is better to open and edit an old file and save it under a new name. Many settings are fixed, and editing a file reduces the chance of entering in a wrong value.
After a file (new or old) is opened, this first screen will open (Figure 34). Change the "Operator" to your name and click "OK" at the bottom of the page. You can click "Update" to get the current date and time.
Figure 34: First page of parameter file setup.



The second page declares the detector and PSD electronic window (Figure 35). These settings are PSD: VANTEC-1 and 3. Do not deviate from these values. Click "OK" and continue to Scan Settings.
Figure 35: Detector declaration.
Scan Settings includes Scan Type and Sample Rotation. Scan Type should stay set to "Locked Coupled". This is a hardware setting indicating that the theta and 2theta positions move together. Under Sample Rotation, the Spinner can be set on or off. This spinner spins the sample while being scanned. This is typically on because it captures all potential angles of the sample giving a complete image of the material. Rotation Speed is set to 30 rpm and .5 rps (you only have to enter in one of these fields). Click "OK" and continue to scan parameters.
Figure 36: Scan Settings parameter window.



Figure 37: Scan Parameters window.Scan Parameters includes the scanned angle range, angle step size, number of steps, time per step, and delay time (Figure 37). Adjust the angle range depending on the material and scientific objectives. For example, if looking for clays, set a low angle (3° – 30°). The step size determines how much the goniometer will move before recording more data. The number of steps will adjust itself based the step size and angle range. Time/Step controls how long each step is measured. The Delay Time will add in an amount of time to wait before scanning the next sample. The machine does have limits on these settings and if something is entered outside of its range it will alert you. Click "OK" and move onto Generator Settings. At low angles (2-4° 2theta) there is a very sharp peak. This is caused by beam overspill onto the sample holder.



Generator Settings contains the X-Ray Tube Configuration and Generator Configuration (Figure 38). The X-Ray Tube values are constant. You can adjust the kV and mA in the Generator Settings. The voltage is typically between 30 and 40 kV and the current is 40 mA. Lowering these values too far can reduce peak intensity. Click "OK" and continue to the Beam Optics window.
Figure 38: Generator Settings window.The Beam Optics settings lists the Divergence Slit and AntiScattering Slit (Figure 39). Both of these are constant values based on our hardware setup. The Divergence Slit should be set to .300°. Click "OK" and you will have finished all the settings and will loop back to the first window.
Figure 39: Beam Optics window.
Save the file under a new name to the path Local Disk C: > DIFFDAT1 > DIFFDAT1_old computer pre March 2013. You can print this file by clicking the "Report" tab at the top the subtree window and then clicking the print icon. Occasionally scientists will ask for a printout of the settings to put in their reports.

Troubleshooting

For specific errors or instructions on adjusting or realigning components on the D4 please refer to the D4 hardware maintenance binders in the XRD lab.

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Using fixed scan mode, the start to stop range is determined by the configuration and cannot exceed the geometry angle set in Config (max = 12°).

Appendix A: Running Samples in Manual Mode

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At some point it may be necessary to run samples in manual mode, for example the automatic sample grabber is not working. Manually loading samples does require the user to load in samples one by one, making a more labor intensive process.
To run the D4 on manual mode:

1. Place the sample, by hand, into the sample transport (Sample swing).
2. Set up the Job in XRD Commander
3. In the Job tabs, create a new job
4. For sample position, enter "man"
5. Set the rest of the job up as normal, i.e. dql file, raw file…
6. Select start
7. The sample will swing back into place, and lift it into measuring position
8. When the measurement is done, the sample will be brought back to the front of the sample transport.
9. Multiple dql files can be used only if the same sample is being measured.

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