François Martin

Phyllosilicates synthesis: a way of accessing edges contributions in NMR and FTIR spectroscopies. Example of synthetic talc

A series of new-generation synthetic talcs were prepared by varying the hydrothermal synthesis duration from a few hours up to 2xa0months. Crystallinity and particle size analysis of the synthetic products were evaluated by photon correlation spectroscopy, transmission electron microscopy, differential thermal analysis and unoriented X-ray diffraction, and then analyzed by various spectroscopic methods such as Fourier transformed infrared spectroscopy and solid-state 1H and 29Si magic angle spinning nuclear magnetic resonance. The new process for preparing synthetic talcs allows to obtain single-phased particles which after few hours grow heterogeneously and simultaneously in both the c* direction and the (ab) plan. Fine particles, observed for whatever the synthesis duration, lead to the presence of numerous sheet edges surfaces due to particle size which represents the main difference with natural talc. Spectroscopy data show the influence of the fine particles on signals and highlight that synthetic talc characterization is a potential tool for better understanding crystal chemistry of natural talc.

Provenance of Cenozoic sedimentary rocks from the Sulaiman fold and thrust belt, Pakistan : implications for the palaeogeography of the Indus drainage system

Abstract: The provenance of middle Eocene to early Miocene sedimentary rocks cropping out in the Sulaiman fold and thrust belt has been determined examining the mineralogy, bulk-rock major and trace elements, and Nd–Sr isotopes. The older (50–30 Ma) deposits are characterized by a mixed orogenic provenance with a major contribution from the Karakorum and the Tethyan belt (c. 80%). As the 50–30 Ma deposits have a provenance distinct from that of coeval Subathu, Khojak and Ghazij shallow marine formations of India and Pakistan, we propose that they were deposited as a distinct delta system that once fed the Palaeo-Indus fan. We document a major change in provenance that occurred before the early–late Oligocene transition at c. 30 Ma. This change in provenance is marked by the appearance of chlorite and monazite and a shift toward more radiogenic Nd–Sr isotopic compositions. We interpret this change as the result of the exhumation and erosion of the proto-Higher Himalaya. The 30–15 Ma sampled rocks are characterized by a major contribution from the Tethyan belt and the Higher Himalayan Crystallines (70–90%) and a subordinate contribution (10–30%) from the Karakorum, Ophiolitic Suture and Trans-Himalaya. As the &egr;Nd(0) values of our 30–15 Ma samples are similar to those of the Palaeo-Indus fan deposits, we suggest that the 30–15 Ma sedimentary rocks of the Sulaiman fold and thrust belt were the fluvial onshore record of the Indus fan. Other coeval deposits of India and Pakistan recorded similar increasing exhumation of the Higher Himalaya range, so that we postulate that these sedimentary rocks all derived from the Palaeo-Indus drainage basin. This would suggest that the modern Indus drainage basin is no younger than 30 Ma.

Synthetic silico-metallic mineral particles (SSMMP) as nanofillers: comparing the effect of different hydrothermal treatments on the PU/SSMMP nanocomposites properties

Two new synthetic silico-metallic mineral particles like TOT–TOT swelling interstratified (SSMMP) produced with distinct hydrothermal processes (talc 7xa0h/315xa0°C and talc 24xa0h/205xa0°C) were used to synthesize polyurethane nanocomposites by in situ polymerization technique. These fillers were added in a range of 0.5–5xa0wt% related to the mass of the pure polymer. The dispersion and interaction between the fillers and the polymeric matrix were evaluated by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The X-ray analysis indicated that the synthetic SSMMP are well dispersed/or exfoliated into the polymer matrix. The high surface area of the synthetic SSMMP was significant for the increase in the crystallinity and thermal properties of the nanocomposites. In the case of Young’s modulus, for nanocomposites PU/SSMMP 24xa0h and the pristine PU, a similar behavior was observed. However, for the nanocomposites PU/SSMMP 7xa0h, an increase in the Young´s modulus values until 3xa0% of filler addition when compared to pure PU was noticed. The creep-recovery test showed that both SSMMP behave as a mechanical restraint of the polyurethane chains. The results evidenced the importance of the SSMMP syntheses conditions to obtain nanocomposites with desired properties.

Hybrid Pu/Synthetic Talc/Organic Clay Ternary Nanocomposites: Thermal, Mechanical and Morphological Properties

Polyurethane (PU) nanocomposites filled with inorganic particles, aiming at the improvement of mechanical and thermal properties, are well known. Unlike previous work we describe here the combination of two fillers, synthetic talc (silico-metallic mineral particles-SSMMP) with distinct hydrothermal processes (SSMMP 7 h and 24 h) and organically-modified commercial clay (SPR), aiming towards development of new polyurethane ternary nanocomposites by in situ polymerisation. Fillers were added 3 wt.% of the mass of pristine polymer, with a ranging of weight proportions (75:25/25:75) of SSMMP and SPR. Results were compared to those for nanocomposites containing pure SSMMP and SPR fillers. Dispersion degrees and filler interactions with the polyurethane matrix were followed by FTIR, XRD, SEM, TEM and AFM techniques. Results showed that the fillers presented a good dispersion and were exfoliated/ well dispersed in the polyurethane matrix. Thermal and mechanical properties of nanocomposites were evaluated in comparison to the binary nanocomposites (PU/SSMMP 7 h, PU/SSMMP 24 h and PU/ SPR). All nanocomposites presented superior values of Youngs modulus to that of pristine PU. Results evidenced that the blend of SSMMP and SPR fillers is an interesting strategy to improve thermal and mechanical properties of nanocomposites.

Waterborne polyurethane/Fe3O4-synthetic talc composites: synthesis, characterization, and magnetic properties

Nano-Fe3O4-synthetic talc gel was used as filler in the synthesis of waterborne polyurethane/Fe3O4-synthetic talc nanocomposites. This filler presents numerous edges (Si–O and Mg–O) and OH groups easily forming hydrogen bonds and polar interaction with water conferring hydrophilic character, consequently improving filler dispersion within a water-based matrix. Yet, the use of waterborne polyurethane (WPU) as matrix must be highlighted due to its environmentally friendly characteristics and low toxicity compared to solvent-based product. Fe3O4-synthetic talc-nanofillers were well dispersed into the polyurethane matrix even at high filler content as supported by XRD and TEM analyses. NMR indicates the interaction of filler OH groups with the matrix. For all nanocomposites, one can see a typical ferromagnetic behavior below Curie temperature (about 120xa0K) and a superparamagnetic behavior above this temperature. The use of Fe3O4-synthetic talc for obtaining magnetic nanocomposites resulted in improved materials with superior mechanical properties compared to solvent-based nanocomposites.

Infrared spectroscopic study of the synthetic Mg–Ni talc series

Five talc samples [(Mg,Ni)3Si4O10(OH)2] covering the entire Mg–Ni solid solution were synthesized following a recently developed and patented process (Dumas et al., Process for preparing a composition comprising synthetic mineral particles and composition, 2013a; Procédé de préparation d’une composition comprenant des particules minérales synthétiques et composition, 2013b), which produces sub-micron talc particles replying to industrial needs. Near- and mid-infrared spectra were collected and compared to infrared spectra modeled from first-principles calculations based on density functional theory. The good agreement between experimental and theoretical spectra allowed assigning unambiguously all absorption bands. We focused in particular on the four main OH stretching bands, which represent good probes of their local physical and chemical environment. The description of the vibrational modes at the origin of these absorption bands and the theoretical determination of absorption coefficients provide a firm basis for quantifying the talc chemical composition from infrared spectroscopy and for discussing the distribution of divalent cations in the octahedral sheet. Results confirm that these synthetic talc samples have a similar structure as natural talc, with a random distribution of Mg and Ni atoms. They only differ from natural talc by their hydrophilic character, which is due to their large proportion of reactive sites on sheet edges due to sub-micronic size of the particles. Therefore, the contribution on infrared spectra of hydroxyls adsorbed on edge sites has also been investigated by computing the infrared signature of hydroxyls of surface models.