| Abstrakt: |
Calcium carbonate is widely distributed in nature, mainly in the form of calcite in sedimentary rocks of biogenic origin. Fine-grained calcite is widely used in various industries, but its amorphous modification (ACC) is often required. The review considers the structure and properties of the main calcium carbonate crystalline polymorphs, methods for determining their structure, and methods for stabilizing ACC. In lubricants, calcium carbonate is used in the form of overbased detergent-dispersant additives, where it is stabilized in the form of ACC, or in calcium-sulfonate complex greases. In greases, calcium carbonate is stabilized in the form of crystalline polymorphs of calcite or vaterite, which ensures the thixotropic properties of the lubricant. The conditions for mutual transitions of calcium carbonate polymorphs depending on the methods of preparation, conditions for stabilizing calcium carbonate particles, as well as the effect of the structure of calcium carbonate in additives and greases on tribological properties are considered. [ABSTRACT FROM AUTHOR] |
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