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- Take a front-loading holder and put a clean glass slide over it.
- Take the ring, flip it upside down and put it on the slide (Figure 17). Now the powder will fall on a smooth flat surface that will be easy to flip over.
Figure 17. Ring upside down on glass. Funnel piece next to unit.
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Clay mounts are put onto a zero-background silicon disk that fits into a 2 mm steel sample holder (Figure 21). Only put the disks into sample holders that have a hole drilled in the bottom. The hole allows the disks to be taken out, otherwise they are stuck inside the holder. The disk should sit flush with the sample holder.. Some of the disks are at different depths, so a quartz insert disk can also be put in the bottom of a sample holder with the silicon disk on top. Do not force the zero background disks into the holder, it may break.
Figure 21: Steel sample holder with silicon disk
1. Remove the <2 µm size fraction by collecting the uppermost 1 cm of solution with an eye dropper (it helps to add a little isopropanol). If necessary resuspend flocculated clay particles using the dismembrator and add more borax solution.
2. If material is still very suspended, try centrifuging the samples for 4 minutes at 750 rpm. In this instance, the >2 µm size fraction will be the only fraction suspended in the liquid and all the larger grains will be packed in the bottom. Take the suspended material with an eyedropper and put it on the quartz disk.
3. Make an oriented clay mount by placing 2–3 drops (enough to cover the disk) of clay suspension directly onto the silicon disk. If the material is not spreading evenly, add a drop or two of 70% isopropanol and spread the material around with a small glass rod. Once spread, let the sample dry in the desiccator. The clay particles orient themselves as the solution dries on the disc. Note that it can be difficult to determine if there is enough material on the disc for a scan. Sometimes it may appear as if there is no sediment in the upper 1-2cm and thus nothing on the disk. Try scanning in the XRD first, it is surprising what the XRD will return. If the scan is not satisfactory add a few more drops from a bit deeper in the test tube.
Once the sample is dry, you are ready to run it through the D4. If there are additional treatments requested, continue to the sections below.
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