Influence of mechanical processing on physical and technological properties of industrial layer silicates

Layer silicates (e.g., kaolinite, talc, smectite, pyrophyillite) occurring as fine particulate minerals can be considered natural nanostructured materials showing size dependent properties that make them candidates for many applications, for example environmental remediation, catalysis, cement and ceramic processing and polymer-nanocomposite production. For this reason, recently a great attention is being paid to mechanical industrial processes, such as grinding and micronization, which can induce significant changes in structural, physical, thermal and technological properties of these silicates. Conventional industrial grinding is considered a high cost-effective process because the majority of mechanical energy is consumed by the grinding devices and only a few percent is transferred to material comminution. The present paper reports on the modification of structural and physical properties of kaolinite, talc and montmorillonite by using a specifically built ball milling apparatus that induces simultaneous shear and compaction stress to the material in controlled thermodynamic conditions (RT and vacuum). Controlled constant temperature of 25°C assures the reproducibility of the mechanical process and minimizes thermal reactions, whereas medium-high vacuum (P = 0.13 Pa) avoids possible water adsorption and cations exchange and is more effective to induce pronounced structural and morphological changes than air and inert gases.