Preparation of Thin Section Samples for Polarizing Microscopy
1. Sample selection
Select a suitable sample according to the needs, and determine the part that should be ground.
2. Cutting
According to the characteristics of the material, choose the inner circle or outer circle slicer. Generally, when slicing with an external circular slicer, it should be cut in strict accordance with the prescribed method. The size should not be too large or too small. It depends on the specific size of the material provided, generally around 2cm*2cm*.0.5cm.
3. Grinding the bottom surface
After sample selection, take the flat side as the bottom surface and select samples step by step on the grinder by hand or machine, and use 200#, 600#, 1200#, 2000# emery to smooth the surface, firstly grind the four sides evenly, and grind the thickness to About 1-2mm.
4. Viscose
Take soybean-sized gum Canada and drop it on the glass slide, heat it slowly with an alcohol lamp to melt the gum, and at the same time heat the sample that has been smoothed on the bottom to get rid of the water in it. During the heating process, you should use a matchstick to pick up a little Canadian gum at any time, put it in your hand and knead it after cooling down. If the gum sticks to your hands and cannot be kneaded into a ball, it means that the gum is still soft. At this time, it is not possible to stick the film. If the glue is kneaded in the hand and it becomes powder, it means that it has been heated too much, and the film cannot be glued. The gum must be heated until it is picked up with a matchstick, put it in the hand for a while, and then kneaded to form a ball. And use fingernails to scratch to a certain degree of hardness, no scratches, and no brittleness, stick the bottom surface of the sample to the glass slide with uniform pressure, but pay attention to the absence of air bubbles between the gum and the sample, if any If so, the glue must be reapplied.
5. Thinning
Put the glued sample on the grinder (or glass plate), grind it to 0.1-0.15mm with 200# sandpaper, and then change it step by step to 600#, 1200#, 2000# fine sandpaper and grind it to 0.03mm. Points to pay attention to: 1). When grinding thin, the fingers pressing on the glass slide should be evenly pressed, otherwise the thin slices will have a thickness difference and become wedge-shaped. Therefore, the sample should be observed against the light at any time, and according to The strength to correct the flatness of the entire test piece. 2). In the step-by-step replacement of corundum, the test piece must be strictly cleaned to remove the fine sand on the sheet, otherwise the coarse sand will inevitably affect the surface finish of the sheet. 3). When grinding with 2000# fine sand at the end, use a microscope to observe at any time. If you find that the thickness has reached (taking quartz as an example under crossed polarized light, the highest interference color appears yellow-white), you can stop grinding.
6. Whole coverslip
After the sample is ground, in order to preserve the sample and prolong the use time, it is necessary to correct the thin section. Use a general scraper to gently scrape off the excess Canada gum around the sample and trim it into a regular and beautiful shape. A small amount of Canada gum was then dropped onto the coverslip and heated slightly. After the gum is melted, it can be covered on the sheet. Attention should also be paid to the exclusion of air bubbles, so as not to affect the observation effect of the thin section.
7. hot glue
After the cover sheet is covered, the cover sheet can be moved because the Canadian gum has not yet been cured, and hot glue must be carried out. The method is to take a carving knife and heat it on a gas lamp until it turns red, then place it around the cover glass and scald it until the color of the Canadian gum is slightly yellow, then wash off the gum around the cover glass with alcohol or xylene , affix the label, and the entire sheet is finished.
