I have tested the porous tungsten matrix after copper removal by SEM, and found that there are a lot of flaky fine particles on each tungsten particle (after EDS test, it is judged that these are tungsten or tungsten oxide if possible). Why do these fine particles appear on the surface of tungsten particles?
The appearance of flaky fine particles on the surface of tungsten particles in your SEM images could be due to several factors:
1.Oxidation: Tungsten is known to oxidize readily in the presence of oxygen or other oxidizing agents, even at relatively low temperatures. The formation of tungsten oxide (typically WO3 or WO2) on the surface of tungsten particles is a common occurrence. These oxide layers can appear as fine particles, flakes, or coatings.
2.Surface Contaminants: During the processing or handling of tungsten samples, contaminants such as oils, greases, or other organic materials may come into contact with the surface. When exposed to high vacuum conditions in the SEM, these contaminants can break down, producing fine particles or flakes.
3.Sample Preparation: The method used for sample preparation can influence the appearance of particles on the surface. Techniques like polishing or sputter coating can introduce artifacts or modify the surface of the sample.
4.Inherent Structure: Tungsten particles can have variations in their crystal structure, which may be more apparent on the surface. These variations could manifest as fine particles or flakes.
5. Sputtering or EDS Process: The sputtering process itself, which is used to remove surface layers for EDS analysis, can sometimes cause artifacts or redistribution of material on the sample surface, leading to the appearance of fine particles.
To determine the exact nature and origin of the fine particles on the surface of your tungsten particles, it's essential to consider the specific sample preparation techniques, the environment in which the samples were stored or handled, and the conditions under which the SEM and EDS analysis were conducted. Additionally, conducting further characterization, such as X-ray photoelectron spectroscopy (XPS), may provide more insight into the chemical composition and nature of the surface contaminants or oxides.
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