Dust particles lead to wear and damage in fine mechanical systems and to yield losses in the manufacture of electronic components. We have found experimentally that most of the damage is due to a relatively small fraction of the dust particles present. Many cases involve composite particles that become much more strongly adherent after cyclic changes in relative humidity and deliquescence. Water condenses around the water-soluble part of a composite particle. The water-soluble particle then dissolves. The solution wets both the substrate and the undissolved part of the composite. Later, when the relative humidity decreases, the soluble material recrystallizes, forming a strong bond between particle and substrate. A bond of this kind is much stronger than the original because the interfacial contact area has greatly increased. In many cases a particle cemented to the surface in this way cannot be removed without damage to the substrate. The right combination of soluble and insoluble components is found in only a small fraction of all dust particles. These cause most of the damage. We analyze the physical chemistry of the strong adhesion process and show the conditions under which it can take place.
KeywordsDust Particle Composite Particle Dust Sample Strong Adhesion Salt Particle
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