| Summary: | 碩士 === 國立臺灣大學 === 地質科學研究所 === 91 === In tribology, we study the grinding/attrition behaviors of two materials, usually with similar hardness, and all the phenomena happened on their boundaries. As to the grinding behaviors of two materials with very different hardness, i.e., one is soft and another much harder, only a little is known comparing to the rapid development and much progress in almost all the other areas of tribology. In this thesis, author summaries the results of a study on the grinding behaviors of ink-stick and ink-stone, which is very similar to the chemical mechanical polishing (CMP) process in modern semiconductor industry, also a perfect example of two materials with very different hardness.
We systematically analyzed some basic properties of several samples of one famous type of ink stone -- Luochi stone, and using a custom designed grinding machine carried out a series of experiments. We assumed that a good ink stone, comparing to other unsuitable stones, should have: (a) low open-porosity, (b) high density, (c) special mineral assembly, (d) small grain size, and (e) low surface roughness. Based on our analysis, however, we found assumptions (a)-(c) were false, and assumptions (d) and (e) were more likely to be true.
SEM analyses reveal that the grinding process of ink-stick and ink-stone consists of two stages. First, after water softening the glue at the tip of the ink-stick, many agglomerated large particles (tens of microns in diameter) are mechanically removed from ink-stick by grinding; second, the agglomerated large particles keep dissolving in water until all the glue in the particles fully dissolved, and finally only the carbon black (~50 nm in diameter) source material left in the black ink.
We have derived an empirical equation describing the relationship between the removing rate (RR) of ink-stick and two most important parameters, pressure P and grinding velocity V. The relationship is not linear; rather RR is proportional to P1/8 and to V1/5. This can be explained by the role of water in the grinding process — when pressure is high enough, not enough water can stay at the boundary of ink-stick and ink-stone, therefore the ink-stick can no longer be fully softened and the increment of RR will gradually decrease to a halt in response to the pressure. While when the grinding velocity is fast enough, the water at the boundary simply doesn’t have enough time to dissolve the glue at the tip of the ink-stick. Therefore, RR will also approach to a constant to the increasing of velocity. Nevertheless, we may never be able to reach the constant RR region, because the ink-stick will soon break down when suffering either a really high applied-pressure, or a high mechanical stress due to a fast grinding velocity. The quantitative descriptive model derived from this study hopefully will help to explain the grinding behaviors of other materials in many other systems.
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