Before being crushed in the X-Press, hard rock samples for ICP analysis are polished (Figure 1, Steps 1 and 2) and put in a sonic bath at least three times (for 15-20 minutes each): first bath is with isopropyl alcohol and following baths are with DI water (Figure 1, Step 3; see ICP Preparation for further details). Hard rock samples for XRD analysis do not usually need to be polished before being crushed.
Figure 1. Polishing and cleaning hard rock samples
Crushing Samples in the X-Press
The X-Press is a motorized hydraulic press that crushes samples into smaller pieces. The X-Press is used to crush hard igneous rocks and highly compacted sediments.
Preparing the X-Press area
- First, clean the X-Press with simple green and isopropyl alcohol. Clean the work area and materials with isopropyl alcohol for each sample.
- Place a large KimWipe on your working surfaces for your clean materials. Next collect the following supplies that make up the 'crushing unit' of the X-press (Figure 2). Materials are located in the drawer labeled 'X-PRESS SUPPLIES' in the X-Ray Prep Area in the Thin Section Lab.
- Weigh Paper 6" x 6"
- Core liner
- Two Delrin discs
- Stainless steel base
- Aluminum Die
Figure 2. Materials needed for assembly of ‘crushing unit’. A. Weigh Paper 6”x6”. B. Core Liner C. Two Delrin Discs D. Stainless Steel Base E. Aluminum Die
3. Put on gloves and 'wash' them with isopropyl alcohol. Clean the crushing supplies with isopropyl alcohol and set them down on the clean surface.
4. Collect sample beakers from the drying oven (for ICP preparation) or dessicator located in the X-Ray Lab. Put a piece of Parafilm® over each beaker and bring them over to the X-Press (Figure 1, Step 4).
Assembling the crushing unit
Now that the X-Press area is clean and the samples are in the Lab, assemble the crushing unit as follows:
- Grab the stainless steel dish. This is the base for the crushing unit. Place a piece of Weigh Paper on the base (Figure 3, Step 1).
- Put one Delrin disc on top of the weigh paper (Figure 3, Step 2).
Place the sample on top of the Delrin disc (Figure 3, Step 3). These discs can fracture leaving Teflon flakes in the sample so arrange the sample such that the two flattest surfaces are the top and bottom.
- Now place the second Delrin disc on top of the sample (Figure 3, Step 4). Again make sure the disc rests flat against sample.
- Put the aluminum die on top of the Delrin disc, holding it until you slip the core liner over the unit (Figure 3, Step 5).
- Now slip the piece of core liner over all the pieces and resting inside the stainless steel base (Figure 3, Step 6). This contains the sample pieces inside the unit.
Figure 3. Assembling the crushing unit
The crushing unit is now assembled and we can start crushing samples (Figure 4).
Figure 4. A. Overview of the X-Press. A. Metal platform sample rests on B. Jacksrew C. Pressure Relief Handle. D. ‘On’ toggle E. Pressure Gauge. B. Crushing unit inside the X-Press
Place the crushing unit inside the X-Press in the middle of the metal platform (Figure 4A ). Put in the sliding polycarbonate door down when crushing samples. Tighten the jackscrew (Figure 14 B) until it rests firmly against the aluminum die. Tighten the 'pressure relief handle' with a clockwise turn (Figure 14 C).
Note: The polycarbonate door sits on two interlock switches that enable operation. If the door is not fully closed or pressing down on these switches the machine will not work.
Crush the sample by continuously holding down the toggle switch (Figure 14 D). The motor and pump can be heard and the pressure will rise (Figure 14 E). Once the desired pressure is reached the toggle can be released and the sample will sit under that pressure. Do NOT leave a sample under pressure for any reason. For most samples ~5 tons of pressure is enough force to crack it. If you find the need to go near 10 tons, try rotating the sample onto another side and repeat the process again. Taking the pressure up greater than 10 tons can cause the disks and the core liner to shatter. Contaminating the samples and creating a safety hazard.
Safety Note: Always wear safety glasses. Do not stand directly in front of the X-Press while it is operating. Never leave the X-Press unattended while using. Do NOT take the instrument above 10 tons of pressure.
After the sample has cracked remove the crushing unit. To remove the unit, loosen the 'pressure relief handle' by rotating it counter clock wise and press down on the toggle switch. The pressure gauge should read zero and the metal platform will lower down. Do not leave the platform up, always make sure to lower it back down after crushing a sample. When the platform is level with the surface let go of the toggle and start unscrewing the jackscrew. Then open the door and remove the unit. The pieces can be poured into a labeled bottle that will eventually hold the finely ground powder. From here the pieces will then be put into the Shatterbox vessels.
If pieces are still too large then repeat the same setup and crush it again. Look out for and remove any pieces of the Delrin Discs that may have chipped off and gotten into the sample. Leaving pieces of the Delrin Discs in the sample will cause contamination.
Grinding Samples in the Shatterbox
The shatterbox takes the crushed pieces from the X-Press and grinds them into a very fine powder. The Spex shatterbox is capable of grinding three standard size samples or one large sample. Our grinding vessels used are tungsten carbide.
Apparatus and Materials
- Shatterbox
- Tungsten Carbide Vessels: Vessel, Puck, and Lid
- Samples
- 1oz Sample Vials
- Sample Labels
Turn on the Shatterbox by flipping the 'On' switch located on the back panel (Figure 15A). The control panel is located on the front of the lid next to the handle (Figure 15C).
Figure 15. Shatterbox. A. Power switch. B. Cover. C. Control panel
There are two sizes of grinding vessels: small and large. Each size has different components and requires a different setup inside the Shatterbox. The small vessel holds between 5-20 mLs of material and has three components: container, puck and lid (Figure 16).
Figure 16. Small vessel components. A. Container B. Puck. C. Lid
The large grinding vessel holds between 20 – 60mLs of material and has five components: a container, puck, inner ring, O-Ring and lid (Figure 17).
Figure 17. Large Vessel components. A. Container B. Inner Ring C. Puck D. O-Ring E. Lid
The small vessels have a small indent in the bottom of the container and they will sit in the shatterbox resting on either a three-pinned plate (Figure 18) or a one-pinned plate (Figure 19).
Figure 18. Three-pinned rack plate to hold three small vessels in Shatterbox
Figure 19. Single-pinned rack plate to hold one small vessel in Shatterbox
The three-pinned plate will hold three vessels while the one-pinned plate will only hold one. If two samples need to be crushed select the three-pinned plate. The large vessel will sit directly in shatterbox without an additional plate below it.
Loading the Shatterbox
Transfer the sample pieces into the grinding vessel. Pour sample pieces between the puck and the wall of the vessel (Figure 20). There can't be any material on top of the puck or inside the sealing ring; otherwise the vessel will not seal properly and the sample can spill inside the shatterbox. If any pieces are on top of the puck or ring, use gloves, tongs, or a KimWipe to move the sample into the vessel. Put on the lid and start assembling the shatterbox.
Figure 20. Small vessel filled with sample pieces. No sample material is on the top the puck or in the lid ring.
Open the lid, pull out the lever arm (Figure 21A), and pull up the clamp arm (Figure 21B). This will reveal full access to the inner capsule (Figure 21C).
Figure 21. The inside of the Shatterbox. A. The lever arm B. The clamp arm C. The inner capsule
Depending on vessel size, you will either put in the pinned plate (small vessels) or the large vessel directly. The shatterbox setup will also vary depending on sample number. If you are crushing one sample use the one-pinned plate, whereas for two or three samples use the three-pinned plate (Figure 22). For crushing two samples, two vessels will be full, whereas the third will be empty without a puck or you can add quartz sand to the third container. It is important to maintain balance within the machine to prevent damage.
Figure 22. Inside the Shatterbox with the bottom three-pinned rack plate resting inside the inner capsule.
Now load vessels onto the plate (Figure 23). The divet in the bottom of the vessels will settle onto the pins and fit firmly in place.
Figure 23. Three samples loaded into the Shatterbox.
Put the top rack plate over the vessels. Bring down the clamp arm (Figure 24A). The guide on the clamp arm will settle into the boss (Figure 24B) when centered properly.
Figure 24. The top rack plate sitting on top of the three samples. A. Clamp arm. B. the “boss” of the rack plate, where the clamp arm will attach.
Bring the lever arm down and push it into the end of the clamp arm (Figure 25B). Then push the lever arm down over the clamp arm (Figure 25A).
Figure 25. A. The lever arm inserted into the end of the clamp arm. B. The clamp arm pushed over the lever arm.
The resistance in the lever arm is very important and must be adjusted before use. There should be moderate resistance in the arm while pushing it down. If the resistance is too low the containers can shake free; whereas, if it's too strong the clamp can break. Ideal tightness is just past the point where the vessels can be rotated while the clamp is down. Adjust the resistance by raising the clamp arm and pushing on the 'locking pin.' Hold the locking pin and turn the guide (Figure 26A). Rotating the guide clockwise decreases resistance; whereas counterclockwise increases resistance.
Figure 26. The lever arm and the guide. A. Retractable locking pin being pushed to allow adjustment of the 'guide' length.
Now close the lid and turn the emergency stop switch to 'On'. This does not start the shatterbox but does enable operation. If an emergency shutdown is needed, flip this switch to 'Off' and all shaking will stop even though the timer will continue to count down.
Set the grinding time. The LCD screen displays the current operating time (Figure 27A). Adjust the time by pressing on the 'Minute' (Figure 27B) and 'Second' (Figure 27C) buttons. The timer maximum is 9:59.
Figure 27. A. Current operating time. B. Minute button. C. Second button. D. Start button. E. Pause/Stop button.
When the time is set press the 'Start' button (Figure 27D). To temporarily pause the operation press the 'Pause/Stop' button once (Figure 27E). To stop the machine press 'Pause/Stop' twice.
Normal Sounds: The shatterbox is extremely loud. The foam and strap surrounding the shatterbox helps keep it in place and minimize some of the noise.
Abnormal Sounds. If there are any metal on metal sounds shut off the shatterbox immediately. Something inside the shatterbox has probably come loose and will damage the inside of the container.
When the shatterbox cycle is done open the lid and remove the vessels, placing them on the counter. Open the grinding vessel and with clean tweezers take a bit of the powder and feel it against the inside of your wrist. The sample should feel like baby powder, if it does not, repeat the shatterbox cycle.
Transfer powder into Vial
Disassemble the vessel carefully wearing 'Powderless Nitrile' gloves. Clean off any powder on the lid or puck with clean gloves or a Kim Wipe. Carefully remove the puck from the vessel. Pour the sample onto a clean weighing paper. If any powder remains, use a clean plastic spatula, brush, or your finger to dislodge it.
Note: Never use metal to dislodge sample material, as any grooves or scratches in the vessels will increase the risk of contamination.
Cleaning the Grinding Vessels
Vessels must be cleaned in between samples and after all samples have been run for the day. Vessels should never be put away wet. This alters and tarnishes the vessel.
In Between Sample Runs
- Wearing nitrile gloves, wash the individual pieces of the grinding vessels with DI water and a small piece of a scouring pad (no soap).
- After each washed piece piece immediately spray it with isopropyl alcohol and wipe it down with a Kim Wipe. Do not use the ship's compressed air line to dry pieces as the air is too dirty.
- Lay the pieces on, and cover vessels with Kim Wipes.
After the last run for the day
1. Take a scoop of quartz sand and put it in your vessel and run it as you would a sample for several minutes.
2. Remove the vessel and empty out the sand. Scrub the pieces with DI water and a scouring pad. Then spray with isopropyl alcohol and wipe down with Kim Wipe.
If your vessel is particularly dirty run a combination of quartz sand, a little hot water and detergent (Borax). This can be run for several minutes. A thick paste will form and you clean it with DI water and isopropyl as in the other cases.