Elsevier

Applied Clay Science

Inquiry paper

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

Abstract

Over the past 2   years, the synthetic procedure of talc particles has evolved considerably, leading to an inexpensive, convenient, and rapid process that is uniform with industrial requirements. In addition to facilitate the synthetic talc preparation, the evolution of the synthesis procedure has led to an improved crystallographic arrangement of the talc particles in both the c* direction and (ab) airplane. In the present study, the most recent process was investigated with respect to the reaction time, temperature, force per unit area, pH, and table salt concentration to decide the optimal reaction parameters. In the geomaterial manufacture, X-ray diffraction is routinely used for pulverization 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⁎ management. These crystallinity characteristics were used to define the quality of the synthetic talc and its suitability for potential industrial markets.

Introduction

Talc, a layered magnesium silicate mineral with the ideal formula Mg3Si4O10(OH)ii, is ordinarily used every bit a filler in composite materials to reduce their production costs, ameliorate their physical and chemical backdrop, and provide new functionalities. It is used in numerous industrial applications (papers, paints, ceramics, cosmetics, and polymers; (Ferrage et al., 2002)) for its mechanical backdrop, barrier effects, and lubricating backdrop upwards to 900   °C. Still, the apply of this latter belongings in surfaces for the aeronautical sector (Martin et al., 2006, Martin et al., 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 construction. To resolve this outcome 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 force per unit area (Bowen and Tuttle, 1949, Eberl et al., 1978, Johannes, 1969, Roy and Roy, 1955). Then, in an investigation 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 tardily 1980s, Decarreau et al. (1989) used low-temperature and autogenous-force per unit area hydrothermal treatment (eighty–240   °C) to obtain stevensite, kerolite, and talc. The starting material was a gel with a Mg/Si ratio identical to that of talc (i.e., 3/4). Decarreau et al. (1989) demonstrated that the stability of the mineral depended on the temperature of the hydrothermal synthesis and concluded that the starting temperature for talc crystallization was approximately 170   °C. However, this method led to an unstable constructed talc, every bit observed in a retromorphosis experiment during which the crystallinity decreased to form kerolite.

When the replacement of natural talc by constructed talc was envisaged in specific industrial applications, the considerations included the cost of the reactants, the reaction time, and the energy requirements. Since 2004, efforts have been focused on developing an inexpensive, stable, highly pure production of submicronic size.

The present written report aims at fine-tune the most recent constructed process and to assess the influence of several parameters, such as reaction time, temperature, pH, the addition of sodium acetate, and external pressure, on the crystallinity of talc products equally assessed through X-ray diffraction (XRD) measurements. The constructed process is discussed with regard to specific industrial applications.

Section snippets

Experimental section

Synthetic talc samples were prepared using the processes described in different patents (Dumas et al., 2012, Dumas et al., 2013a, Dumas et al., 2013b, Dumas et al., 2013c, Martin et al., 2008b, Martin et al., 2008c). The processes are named in chronological order as P1, P2, and P3. The main steps of talc synthesis and the reactants used for each process are listed in Table 1.

Evolution of the synthetic processes

Any synthetic talc training requires at least two steps: 1) the training of a talc precursor and 2) hydrothermal treatment. Talc preparation has evolved significantly since the Decarreau et al. (1989) process, especially over the past 2   years, to facilitate the procedure and fit industrial requirements. Table one reports the evolution of synthetic talc processes. Every bit the method described by Decarreau et al. (1989) does not lead to a stable product, the first patented procedure (Martin et al.,

Conclusions

Synthetic talc appears to meet the needs of industrial applications and should substitute natural talc in niche market applications. Nanometric particle size and purity are the first added values of synthetic talc. Its synthesis on an industrial calibration is conceivable, as an inexpensive, convenient, and rapid method of preparation has emerged. The employ of inexpensive raw materials, some of which tin can exist reused in the next synthesis and, more peculiarly, the time saved by the newest procedure are

Acknowledgments

This study was financially supported by the ANR-09-MAPR-0017 project. We thank C. Nkoumbou and the anonymous reviewer for their constructive comments.

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