Talc Samples Research Articles

VNIR–SWIR reflectance spectroscopy as a nondestructive technique for compositional determination of archaeological talc samples with a machine learning approach

The material from which an archaeological piece is made provides a great deal of information regarding the society in which it was made; thus, any misidentification can lead to erroneous conclusions. The uniqueness of many of these pieces hinders their mineralogical analysis because the pieces cannot be damaged for sampling; therefore, errors in the classification of these materials are common. In the present study, we evaluate the suitability of the spectroradiometry technique in the analysis of two archaeological talc pieces. Both came from the Iron Age archaeological site of Peña del Castro (La Ercina, León) in the northwestern Iberian Peninsula. We compared the spectral curves of these 2 pieces with the spectral curves from 50 talc geological samples from different geographical sources, combining bulk and powdered samples. Our results show that spectral curves enabled the identification of the talc material in the powdered and bulk samples. Moreover, the absence of the talc characteristic features in other soft materials also used in antiquity enabled the detection of incorrect identification of the classified pieces. Even though our results cannot be used to define any absorption feature characteristic to establish the provenance of the material, in the present study, spectral analysis has been shown to be suitable as a nondestructive technique to mineralogically identify archaeological pieces.

Raman and Far-Infrared Synchrotron Nanospectroscopy of Layered Crystalline Talc: Vibrational Properties, Interlayer Coupling, and Symmetry Crossover

Talc is an insulating layered material that is stable at ambient conditions and has high-quality basal cleavage, which is a major advantage for its use in van der Waals heterostructures. Here, we use near-field synchrotron infrared nanospectroscopy, Raman spectroscopy, and first-principles calculations to investigate the structural and vibrational properties of talc crystals, ranging from monolayer to bulk, in the 300-750 cm-1 and <60 cm-1 spectral windows. We observe a symmetry crossover from mono to bilayer talc samples, attributed to the stacking of adjacent layers. The in-plane lattice parameters and frequencies of intralayer modes of talc display weak dependence with the number of layers, consistent with a weak interlayer interaction. On the other hand, the low-frequency (<60 cm-1) rigid-layer (interlayer) modes of talc are suitable to identify the number of layers in ultrathin talc samples, besides revealing strong in-plane and out-of-plane anisotropy in the interlayer force constants and related elastic stiffnesses of single crystals. The shear and breathing force constants of talc are found to be 66% and 28%, respectively, lower than those of graphite, making talc an excellent lubricant that can be easily exfoliated. Our results broaden the understanding of the structural and vibrational properties of talc at the nanoscale regime and serve as a guide for future ultrathin heterostructures applications.

Water-based lubricant containing protic ionic liquids and talc lubricant particles: Wear and corrosion analysis

Water-based lubricants have been used in different industrial applications in recent years. However, studies evaluating the tribological and electrochemical effects of lubricants with Protic Ionic Liquid (PIL) and talc particles (TC) as additives on SAE 1010 and SAE 1045 steels are still scarce in the literature, which is the objective of this work. Samples extracted from steel sheets were investigated in the normalized (SAE 1010) and quenched-tempered (SAE 1045) conditions. Wear tests in a ball-on-plate type tribometer and corrosion tests using potentiondynamic polarization curves were performed in the presence of different lubricant solutions (PIL 3% + DI water, commercial lubricant 3% + DI water, with and without talc particle additions 0.05 and 0.1 wt%). Analyses of viscosity, pH, wettability, and particle size distribution were conduted on the lubricant and talc samples. Wear and corrosion surfaces were analyzed by SEM/EDS, and Raman techniques. The results showed that the tribofilm formed from the interaction between PIL lubricants and steel substrates decreased the wear due to the increase of lubricity of these lubricants. When the PIL and the commercial lubricants are compared, PIL additives presented higher performance, despite the talc addition. The influence of talc on the corrosion of steel is associated with the differential aeration effect, mitigated by adding the PIL.

Metamorphic dolomitic marble-hosted talc from the Mulvoj area in the Western Pamir Mountains, Tajikistan

Abstract Talc is crystallized in the metamorphic dolomitic rocks of the southwest Pamir mountains in the Mulvoj area, Tajikistan. Field studies show that talc is restricted to metamorphic dolomitic marble layers in the garnet-mica schist and gneiss. The layers are parallel to the original sedimentary bedding and schistosity of the metamorphic rocks. Petrography and whole rock geochemistry reveal calcite, tremolite, quartz and dolomite as the main mineral phases in the talc-bearing metamorphosed dolomitic rocks, while calcite is absent in the samples without talc. XRD studies show that talc samples are almost pure, and geochemistry indicates very low Fe and Cr and very high Mg contents. Geochemical features along with field observations clearly shows that Mulvoj talc is not originated from peridotite. Based on phase relations studies in the CaO-MgO-SiO2-H2O-CO2 system, the reaction between dolomite, quartz, and water at pressure greater than 2 kbar and temperature up to ~460°C and XCO2 up to 0.6 was the main talc forming reaction. Talc and calcite consuming reaction produced tremolite, dolomite and binary (CO2-H2O) fluid.

Molecular overtones and two-phonon combination bands in the near-infrared spectra of talc, brucite and lizardite

Abstract. The near-infrared (NIR) spectra of hydrous minerals display absorption bands involving multiple excitations of vibrational modes. They usually involve OH stretching modes, but their interpretation is not straightforward due to the combined effects of bond anharmonicity and vibrational coupling. In the present study, the mid-infrared (MIR) and near-infrared spectra of well-ordered samples of trioctahedral layered hydrous minerals, talc, brucite and lizardite, have been measured on a spectral range extending from the fundamental vibrational modes to the second OH stretching overtones. The bands corresponding to molecular overtones are interpreted using an effective approach allowing us to infer the anharmonicity and coupling parameters controlling the OH stretching frequencies from spectroscopic data. They follow the usual relation between transition energy and quantum number of the excited state, which facilitates the comparison of NIR and MIR spectra. The results support the assignment of the main overtone bands to specific environments of OH groups and bring new constraints for the identification of the vibrational bands related to Fe and Al substitutions at octahedral sites in serpentines. The two-phonon absorption bands are theoretically analyzed at the density functional theory level by computing the absorption arising from the self-energy of the IR-active vibrational modes. The characteristics of the two-phonon OH stretching continuum between 7300 and 7400 cm−1 and of the combination bands between 4000 and 4800 cm−1 are related to the specificities of the one-phonon and two-phonon densities of states of the three minerals.

Talc modified by milling and alkali activation: Physico-chemical characterization and application in base catalysis

The work aimed at the development of benign solid base catalysts as alternatives for presently used noxious liquid bases. Talc, possessing intrinsic basic properties, was chosen as a particularly attractive and cost-effective precursor. Activation of talc by grinding in a planetary mill followed by treatment with 2 M NaOH was employed as means for basicity enhancement. Such protocol enabled profound modification of talc structure, otherwise resistant to treatment with a basic solution. Deep changes, not addressed in the literature reports so far, took place in the course of combined mechanical and alkali treatment. The amorphized ground talc transformed to the magnesium silicate hydrate (MSH) phase and brucite. Treatment with NaOH led to significant enhancement of surface basicity with respect to the parent materials. The effect was particularly spectacular for alkali-treated, strongly ground talc samples, containing the MSH component. The materials were tested in a base-catalyzed reaction of aldol condensation of acetone. The trend of catalytic activity followed closely the order of surface basicity, which pointed to the key role of MSH as a catalytically active phase in the modified talc solids. Joint mechanical and alkali activation of talc proved to be a simple, yet promising way of developing solid base materials for catalytic applications.

Comparative effect of the three talc deposits in detoxification of Cr(VI) from wastewater

Environmental application of three different talc deposits toward the removal of hexavalent chromium ions Cr(VI) from aqueous solution as simulated polluted water was investigated. Three talc samples (T1, T2 and T3) were used from Wadi Atshan area, Eastern desert, Egypt. The affecting parameters, such as pH, contact time, solution pH and the dosage, were studied during the progress of the adsorption process of chromium (IV). The results showed that a contact time of 65 min for T3, 80 min for T2, 85 min for T1 under optimum condition at pH 7 at 25 °C. The adsorption capacity for the removal of Cr(VI) using the three samples T1, T2 and T3 was evaluated to be 78%, 86% and 97%, respectively, under optimized conditions utilizing 1.0 g/L of the adsorbent. Characterization of the three talc samples was performed using XRF, XRD and FTIR analyses in order to assess the physicochemical properties of the adsorbents. This approach provided new class of adsorbent as highly efficient materials for Cr(VI) removal based on talc deposits which possess some privileges such as availability of the natural resources that makes the process to be low cost and simple.

MSA at 100 and why optical mineralogy still matters: The optical properties of talc

Abstract MSA’s 100 years are memorialized herein with a combination of (1) events marking our centennial; (2) publications devoted to it; and (3) my series of six MSA president letters in Elements written specifically for this moment. In some of those letters, I stressed the importance of optical mineralogy and the role it played in areas outside of academics. As such, new optical data are presented herein on 20 well-characterized talc samples from other studies, as there appears to have been no thorough study of the optical properties of talc. Other than academic interest, these data will find use in the ongoing issue of the purported asbestos content of talc.

Thermochemical purification of talc with ammonium sulphate as chemical additive

This study reports on the thermochemical reactivity of talc with ammonium sulphate, a low-cost, recyclable chemical additive commonly used in the thermochemical extraction of strategic metals from low-grade ores and industrial and mine residues. The talc sample used in this study contained 70% talc, 15% lizardite and 10% kaolinite, following the removal of carbonate minerals by HCl leaching as a pre-concentration step. The solid product obtained by thermochemical treatment followed by aqueous leaching contained high-grade purified talc (>98%) as the principal mineral phase. It was depleted of lizardite and kaolinite, which had reacted with ammonium sulphate to form water-soluble hydrated ammonium metal sulphates. A comparative analysis of the TGA profiles of the concentrated parent sample, the solid product and the solid residue highlighted an identical mass loss between 850 °C and 1000 °C, which is the temperature range at which the dehydroxylation of talc occurs. This indicated minimal, if any, structural denaturation of the talc phase following thermochemical treatment with ammonium sulphate under the experimental condition studied. This process may therefore represent a promising technology for the purification of talc under the right market conditions, provided the mineral co-exists with phases featuring a high degree of reactivity with ammonium sulphate under thermal conditions.

The influence of Ni/Mg content of synthetic Mg/Ni talc on mechanical and thermal properties of waterborne polyurethane nanocomposites

Waterborne polyurethanes (WPUs) present interesting properties when compared to their solvent-based counterpart besides being organic solvent free. WPUs also present some drawbacks such as low thermal and mechanical properties. The goal of this work was to synthesize and characterize new synthetic talc in a gel form with different magnesium (Mg) and nickel (Ni) ratios in their chemical structure Si4(MgxNi1−x)3O10(OH)2 with 0 < x < 1 and to evaluate their influence on mechanical and thermal properties when used as filler in WPU matrix in order to obtain new nanocomposites as well. WPU/STMgxNiy nanocomposites were prepared by physical mixing and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), atomic force microscopy (AFM) and mechanical dynamic analysis (DMTA). Improvements in nanocomposites mechanical properties in relation to pristine WPU matrix were observed for samples with higher synthetic talc content. The variation of the amount of Mg and Ni in synthetic talc composition altered the storage and loss modules results being higher for nanocomposites obtained with synthetic talc samples with higher Ni content in their compositions. Tg varied according to synthetic talc content. Synthetic talc with different metal content in their composition changes WPU nanocomposites thermal and mechanical properties. These fillers can be used to design nanocomposites with desired applications.

Mineralogical and Geochemical Characterization of Talc from Two Mexican Ore Deposits (Oaxaca and Puebla) and Nine Talcs Marketed in Mexico: Evaluation of Its Cosmetic Uses

The detailed mineralogical, physical and chemical characterization of nine samples of imported cosmetic talc and of two samples of talc from currently non-productive Mexican ore deposits (Oaxaca and Puebla States) is presented. The imported cosmetic talc was classified into two groups, considering whether they are packed in the country of origin or in Mexico and considering their price. X-ray diffraction, infrared short wave, thermogravimetric analysis and scanning electron microscopy were used for mineralogical characterization. For the physical characterization, colorimetry and laser granulometry were used. The chemical composition (major, trace elements) was studied by ICP-MS. It was concluded that only the highest priced and imported in packaged form talcs meet the specific purity requirements for a talc of cosmetic type. The talcs that are packed in Mexico and the talc of the studied Mexican deposits present mineralogical and chemical impurities that make their use difficult in the manufacture of high-quality cosmetic talc. The low-price talc should not be sold as cosmetic talc, and the regulations in Mexico on this subject should be reviewed and updated.

The effect of solid solution on the stability of talc and 10-\xc5 phase

Talc and 10-Å phase are hydrous phases that are implicated in fluid processes and rheological behaviour in subduction zones. Natural samples of talc show limited compositional variation away from the MgO–SiO2–H2O (MSH) endmember, with only substitution of Fe2+ for Mg occurring in significant amounts. In experiments at 2 GPa, talc containing 0.48 apfu Fe2+ begins to break down in the divariant field talc + anthophyllite + quartz at ~ 550 °C, a temperature ~ 270 °C lower than in the MSH system. At 4 GPa, Fe-bearing talc breaks down over a wide temperature interval in the divariant field talc + enstatite + coesite. The large decrease in temperature of the beginning of talc breakdown shows that Fe2+ is partitioned strongly into enstatite and anthophyllite with respect to talc. In phase reversal experiments at 6.5 GPa, the beginning of the dehydration of 10-Å phase containing 0.48 apfu Fe2+ was bracketed between 575 °C and 600 °C, a temperature ~ 100 °C lower than the MSH endmember reaction. The relative positions of the talc and 10-Å phase dehydration reactions indicate that the latter is able to accommodate greater Fe substitution, and is, therefore, more stable in Fe-bearing systems. In experiments at 6.2 GPa, 650 °C in the systems MgO–Al2O3–SiO2–H2O (MASH) and Na2O–MgO–Al2O3–SiO2–H2O (NMASH), 10-Å phase was synthesised that contains up to 0.5 apfu Al in the system MASH (compared to 0.8 in the starting material) and up to 0.4 apfu Al + 0.4 apfu Na in the system NMASH (compared to 0.7 of each of Al and Na in the starting material). Further experiments are required to determine if higher Al and Na contents in 10-Å phase are possible. The much higher Al and Na contents than found in talc indicate that, as with Fe, substitution of these elements enlarges the 10-Å phase stability field with respect to talc. In contrast to the effect of Fe, Al and Na also increase the stability of 10-Å phase relative to its thermal breakdown products enstatite + coesite.

Effect of Combined Mechanical and Ultrasonic Milling on the Size Reduction of Talc

This study aims to investigate the effect of combined mechanical and ultrasonic milling on the size reduction of talc. Firstly, the talc sample was wet ground in a stirred media mill for five different times (30, 60, 90, 120, and 150 min), and the optimum result was subsequently achieved with treatment by ultrasonication. The effects of amplitude (20, 35, and 50 μm), solid content (2.5, 5, 7.5, and 10%), and sonication time (60, 120, and 240 min) on the sizes of the final product were investigated. The pre-milling by wet grinding caused a decrease in the grinding resistance of talc. Sequential ultrasonic treatment, which was applied to the talc sample, generated smaller particles in comparison to those acquired by stirred media milling alone. Experimental results were assessed based on the product particle size (d10, d50), reduction ratio, and specific energy consumption. Submicron particles prepared by ultrasonic treatment were perfectly stable compared to stirred media milling alone as investigated in terms of particle size. In addition, the effects of mechanical and ultrasonic milling on structural properties of talc particles were characterized by XRD analysis.

Mineralogical and crystal-chemical characterization of the talc ore deposit of Minzanzala, Gabon

AbstractThis research aims to characterize the mineralogical and crystal-chemical purity of two samples of natural talc (BTT6, BTT7) from the occurrence ‘Ecole1’ in the deposit of Minzanzala, southwest Gabon. X-ray diffraction and modal-composition calculations demonstrated the presence of quartz and Al–Fe-bearing phases (kaolinite and/or chlorite and/or Al–Fe oxyhydroxides) as accessory minerals in both ores. In contrast, the chemical and spectroscopic characterization of the talc component revealed remarkable chemical purity expressed by very low Fe contents. According to these results, the talc of Minzanzala might be used as a filler in a wide range of industrial applications, such as in cosmetics, paints, polymers or ceramics.

Analysis of Techniques for Improving the Adsorption Capacity of Talc

Mineral adsorbents, such as talc, are materials that are abundant in nature and used as scavengers, binding agents, fillers, etc. Mechanical and physicochemical pretreatment creates new opportunities for the production of highly effective mineral materials with a wide range of destinations. The possibility of using various techniques to enhance the adsorption properties of dispersed talc, namely, enrichment and use in a mixture with another mineral, treatment with various reagents, and changing the temperature and acidity conditions, is demonstrated. Phenomena and trends having an effect on the adsorption ability of talc are considered. Surface modification of talc can significantly increase its technological capability of absorbing resinous components of wood pulp in the manufacture of paper. It is shown that the adsorption and structural characteristics of dispersed talc change significantly after modifying it with organic reagents. The best effect is achieved when pretreating talc with cationic surfactant N-cetylpyridinium chloride. The resulting adsorbent is characterized by a high value of rosin adsorption, reaching 200 mg/g, which is commensurate with the data on the absorption of rosin by talc pretreated with a Penta-416 industrial mixture. Substantial changes in the surface properties due to an increase in the temperature, a change in the acidity, and a shift in the hydrophilic-hydrophobic balance occur when using the accessible, affordable, and safe anionic surfactants. The highest value of adsorption of rosin (160–170 mg/g) is typical for samples of talc modified with sodium oleate and enriched with zinc oxide. The importance of pretreatment of talc with solutions of mineral acids and salts that promote settling of suspensions and the formation of a compact precipitate is shown.

Application of Talc as an Eco-Friendly Additive to Improve the Structural Behavior of Porous Concrete

Talc is an eco-friendly material used in various domains. In this study, talc, quartz and lime sand were added for improving the performance of porous concrete. For this, talc/quartz and lime sand were used as substitute with 5–30% and 5–15% of aggregates, respectively. Compressive strength, porosity and permeability of the porous concrete blocks and their draining capacity were the tested characteristics. Results showed that although by increasing the amount of talc, quartz and lime sand, compressive strength was improved, permeability and porosity were reduced. However, despite the significant difference in hardness of talc and quartz, mixtures containing talc had acceptable performance and were close to quartz so that the average compressive strength of talc samples was only 0.4 MPa less than the quartz ones. It was also found that threshold value for the addition of talc to increase the strength of porous concrete was 25% and over this rate makes no difference in resistance and even reduces it. Results also revealed that all mixtures had good performance in drainage of synthetic urban runoff—the least-permeable talc sample drained 40-mm runoff in 69 s. Also, the most impermeable quartz specimen drained the 40-mm runoff in 44 s. Generally, the mentioned results indicated that talc, as an eco-friendly additive, had acceptable performance in improving the properties of porous concrete.

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; Procede de preparation d’une composition comprenant des particules minerales synthetiques 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.

Frontal Polymerization of Deep Eutectic Solvents Composed of Acrylic and Methacrylic Acids

ABSTRACTFrontal polymerization of deep eutectic solvents (DESs) made with acrylic or methacrylic acid as the monomer and hydrogen bond donor was studied. Fronts with acrylic acid and choline chloride propagated more uniformly than with pure acrylic acid, so an exploration into how the DES affected frontal polymerization was performed. The hydrogen bond acceptor of the DES was replaced by several analogs to determine the effect on the DES front behavior. The analogs used were talc, DMSO, lauric acid, and stearic acid, which acted as a heat sink, inert diluent, hydrogen bonding diluent, and inert phase change material, respectively. None of the methacrylic acid‐analog systems were able to sustain a front. While the acrylic acid‐analog systems did sustain a front (with the exception of stearic acid), none of the fronts replicated the acrylic acid DES behavior. The acrylic acid–talc sample behaved more violently—like pure acrylic acid polymerization—than the acrylic acid DES, and the DMSO and lauric acid samples produced slower fronts than that of the acrylic acid DES. We propose that the reactivity of the acrylic acid and methacrylic acid is enhanced in the DES. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 4046–4050

Analysis of an Authentic Historical Italian Cosmetic Talc Sample – Further Evidence for the Lack of Cancer Risk

Italian talc from the Pinerolo Mines in North West Italy is known for its extreme purity. Several historical investigations of these mines have demonstrated very small amounts of tremolite in the host rock that occasionally found their way into the mined ore. However, more than sixty years of epidemiological studies of the Pinerolo miners and millers have failed to demonstrate any attendant cancer risk and show that this trace tremolite contamination is of no biological significance.Claims made that the Pinerolo Italian cosmetic talc produced prior to 1975 were contaminated with asbestos, principally tremolite, have been difficult to refute given the lack of authentic historical samples of commercial products. We now describe the analytical findings of a recently discovered authentic historical sample.Sample analyses of this material showed only a few non-asbestiform tremolite fibres - a finding discussed in the light of the historical (pre-1975) studies of this talc deposit: no serpentine (chrysotile) or amphibole fibres were detected.The numerical concentration of tremolite fibres in the talc sample was 3.687 x 106 fibres/gram, corresponding to a mass concentration of 0.722 parts per million.

Environmental Particle Emissions due to Automated Drilling of Polypropylene Composites and Nanocomposites Reinforced with Talc, Montmorillonite and Wollastonite

In this study, the effect on nanoparticle emissions due to drilling on Polypropylene (PP) reinforced with 20% talc, 5% montmorillonite (MMT) and 5% Wollastonite (WO) is investigated. The study is the first to explore the nanoparticle release from WO and talc reinforced composites and compares the results to previously researched MMT. With 5% WO, equivalent tensile properties with a 10 % weight reduction were obtained relative to the reference 20% talc sample. The materials were fabricated through injection moulding. The nanorelease studies were undertaken using the controlled drilling methodology for nanoparticle exposure assessment developed within the European Commission funded SIRENA Life 11 ENV/ES/506 project. Measurements were taken using CPC and DMS50 equipment for real-time characterization and measurements. The particle number concentration (of particles <1000nm) and particle size distribution (4.87nm – 562.34nm) of the particles emitted during drilling were evaluated to investigate the effect of the silicate fillers on the particles released. The nano-filled samples exhibited a 33% decrease (MMT sample) or a 30% increase (WO sample) on the average particle number concentration released in comparison to the neat polypropylene sample. The size distribution data displayed a substantial percentage of the particles released from the PP, PP/WO and PP/MMT samples to be between 5-20nm, whereas the PP/talc sample emitted larger particle diameters.