Synthetic talc advances: Coming closer to nature, added value, and industrial requirements

a r t i c l e i n f o Over the past 2 years, the synthetic process of talc particles has evolved considerably, leading to an inexpensive, convenient, and rapid process that is compatible with industrial requirements. In addition to facilitate the synthetic talc preparation, the evolution of the synthesis process has led to an improved crystallographic arrangement of the talc particles in both the c* direction and (ab) plane. In the present study, the most recent process was investigated with respect to the reaction time, temperature, pressure, pH, and salt concentration to determine the optimal reaction parameters. In the geomaterial industry, X-ray diffraction is routinely used for powder material characterization; the crystallinity of our synthetic talc was evaluated by this technique through measurements of the Coherent Scattering Domain (CSD) size. A crystalline lamellarity index was defined as the ratio between the CSD size values in the (ab) plane and c ⁎ direction. These crystallinity characteristics were used to define the quality of the synthetic talc and its suitability for potential industrial markets. Talc, a layered magnesium silicate mineral with the ideal formula Mg 3 Si 4 O 10 (OH) 2 , is commonly used as a filler in composite materials to reduce their production costs, improve their physical and chemical properties, and provide new functionalities. It is used in numerous industrial applications (papers, paints, ceramics, cosmetics, and polymers; (Ferrage et al., 2002)) for its mechanical properties, barrier effects, and lubricating properties up to 900 °C. However, the use of this latter property in surfaces for the aeronautical sector (Martin et al., 2006, 2009) demonstrated the limitations of the particle size of natural talc (Sanchez-Soto et al., 1997). Natural talc cannot be ground homogeneously below 1 μm without leading to amorphization of the structure. To resolve this issue and to control particle size, we turned to talc obtained from hydrothermal synthesis. The first talc synthesis appeared in studies of equilibrium systems devoted to understanding the stability of metamorphic minerals and mineral assemblages, but this process generally required very high temperature and/or pressure of soils and sediments, new information was obtained from the study of synthetic clay single-phase specimens (Kloprogge et al., 1999; Zhang et al., 2010). In the late 1980s, Decarreau et al. (1989) used low-temperature and autogenous-pressure hydrothermal treatment (80–240 °C) to obtain stevensite, kerolite, and talc. The starting material was a gel with a Mg/Si ratio …