Mica Composites Research Articles

Thermal characterization of mica–epoxy composite used as insulation material for high voltage machines

The study of mica–epoxy-based composite has a great role in high voltage machines industry. Beside electric properties, this composite should present compatible mechanical and chemical, in this case thermal characteristics to insulate properly the conductor strand, avoiding short-circuits, and leading electrical current with minimal losses. Improvement of the quality is possible through the knowledge of raw materials and system. This study aims to list a complete thermal characterization of mica composite, its components, epoxy resin, anhydride methylhexahydrophtalic, mica tape and zinc naphthenate, and thermoanalytical interactions between them. These data shows intrinsic properties of the system, which is so relevant to its great electrical and thermal performance. Thermal analysis allows the detailed study of curing process and thermal decomposition, predicting and suggesting mechanisms, beside future and possible optimization to the system. Composite system glass transition (Tg) was obtained through an important and very respected methodology, presenting the value of Tg = 138 ± 2 °C, finally characterizing the material.

Variations in composition and abundance of white mica in the hydrothermal alteration system at Hellyer, Tasmania, as revealed by infrared reflectance spectroscopy

Short-wave infrared (SWIR) spectral reflectance of hydrothermally altered volcanic rocks in the footwall of the Hellyer massive sulfide deposit was measured with a portable PIMA-II infrared spectrometer. The Al–OH band was used to derive information on the octahedral Al content and the abundance of white mica (sericite) in the hydrothermal alteration and mineralization system. The range of the Al–OH band wavelength from 2192 nm to 2222 nm corresponds to the number of octahedral Al (Al vi ) in white mica approximately from 3.9 to 3.0 (based on 4 octahedral cations per formula). This Al vi range represents a significant compositional variation, covering most of the compositional region between muscovite (Al vi = 4.0) and phengite (Al vi = 3.0). Furthermore, the spectral reflectance data show that the compositional variation of white mica is spatially related to hydrothermal alteration zoning, such that phengitic white mica tends to occur in 1) main upflow fluid channel, 2) intensely altered volcanic rocks, and 3) Pb–Zn mineralization, whereas muscovitic white mica was formed preferentially distal to massive sulfide mineralization on the margin of the footwall alteration system. The results suggest that the Al–OH band wavelength, and therefore the octahedral Al content, of white mica can be used as vectors to mineralization to map the hydrothermal system at Hellyer.

A scanning electron microscope technique for identifying the mineralogy of dust in ice cores

AbstractDust particles in an ice core from East Rongbuk Glacier on the northern slope of Qomolangma (Mount Everest; 28°01′ N, 86°58′ E; 6518 m a.s.l.), central Himalaya, have been identified as mica using a combination of scanning electron microscope-based techniques and energy-dispersive X-ray spectroscopy to identify the elements present, and electron backscatter diffraction to identify the crystal type. This technique for identifying individual crystalline dust particles in samples of glacial ice could be especially useful in the future for identifying water-soluble crystals in ice, for studying the strain history (glaciotectonics) of basal ice or in studies of ice–mica composites used as analogs of quartz-mica rocks.

Effects of interfacial adhesion and crystallization on the thermoresistance of poly(lactic acid)/mica composites

Mechanical and thermal properties of poly(lactic acid) (PLA)/mica and poly(butylene terephthalate) (PBT)/mica composites were investigated when a coupling agent was added. When the PLA matrix was crystallized, it was observed that the interfacial adhesion between the PLA and the mica particles was improved. The result of dynamic mechanical analysis (DMA) showed that the thermoresistance of the crystallized PLA/mica composite was improved significantly. Influence of the interfacial adhesion was studied through finite element analysis (FEA) by inserting void elements between the polymers and the mineral particles. The FEA results were compared with the DMA results and predicted the contact area ratio between the PLA and the mica particles.

Modeling and Characterization of the Relationship between Cell Size and Mechanical Behavior of Microcellular PP/Mica Composites

Abstract The microcellular foamed polypropylene (PP)/mica composites were prepared through chemical microcellular injection to investigate the relationship between the mechanical behavior and the cell size. The mechanical behavior model of the microcellular foams is built based on the elastic stress/strain field. The mechanical behavior of the microcellular composites coincides well with the theoretical model. Under loading the large and non uniform cells are in a state of plane strain, which leads to low tensile and impact strengths, whereas small and uniform cells are in a state of plane stress, which contributes to the transition from brittle to tough fracture behavior in the microcellular PP/mica composite.

What drives the distribution in nature of 3T vs. 2M1 polytype in muscovites and phengites? A general assessment based on new data from metamorphic and igneous granitoid rocks

Petrologic, chemical, and polytype data are presented for dioctahedral potassic micas from K-feldspar-bearing metamorphic and igneous rocks of acidic composition unaffected by high-pressure (HP) conditions. The paper aims to demonstrate that: (1) under non-HP conditions, in both metamorphic and igneous plutonic environments, a given bulk-rock compositional constraint imposes a more or less marked phengitic composition to dioctahedral potassic mica; and (2) this muscovite crystallizes as 2 M 1 , notwithstanding its phengitic composition. The samples (157 in number) are from widespread provenances. We conclude that the growth of 3 T polytype of muscovite is not a function of mica composition. This is consistent with the recent crystallographic knowledge on polytypism, cation ordering, elastic properties, and structural deformational mechanisms of muscovite, which address the stabilization of 3 T with pressure.

Effect of Coupling Agent on the Mechanical, Thermal, Electrical, Rheological and Morphological Properties of Polyetheretherketone Composites Reinforced with Surface-Modified Mica

The mica fillers reinforced Polyetheretherketone (PEEK) composites were fabricated using compression molding technique. The mica surface was chemically modified using vinyltrimethoxy silane and 3–Aminopropyltriethoxy silane. The properties of treated mica PEEK composites were examined in terms of scanning electron microscopy, dynamic mechanical thermal analysis, differential scanning calorimetry and rheological behavior. The modified mica was observed to disperse more uniformly than the unmodified counterpart. The tensile strength and modulus also improved with treated mica filled PEEK composites. The increment of the dynamic modulus for the PEEK/treated mica composites is 82% at 250°C, indicating apparent improvement of high temperature mechanical properties.

Melt Rheological Properties of PBT/ABAS/Mica Composites

Melt rheological properties of poly (butylene terephthlate) (PBT)/poly (acrylonitrile–butyl acrylate-styrene) terpolymer (ABAS)/mica composites were studied at 0.02 to 0.14 vol fraction (Φf) of mica at 518 K. The shear stress vs. shear rate plots was linear and the melts obeyed power law relation. The composites melts were shear thinning. Apparent melt viscosity decreased initially up to Φf = 0.07 the parameter increased with further increase in Φf. Melt elasticity viz. extrudate swell ratio also decreased up to Φf = 0.07 whereas the data increased at Φf > 0.07. Surface treatment of mica particles by zirconate coupling agent, NZ-97, brought about further modification of the rheological properties through enhanced interaction between the matrix and the dispersed phase.

Polypyrrole/conductive mica composites: Preparation, characterization, and application in supercapacitor

Polypyrrole/conductive mica (PPy/CM) composites were prepared by coating polypyrrole (PPy) onto the surfaces of the conductive mica (CM) via the in situ chemical oxidative polymerization method. The encapsulating morphologies were revealed with the scanning electron microscopy (SEM) technique. The PPy/CM composites were characterized with Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The composites possess high electrical conductivity at room temperature, the weak temperature dependence of the conductivity. Based on the cyclic voltammetry and the charge/discharge behavior of the PPy/CM composites, it was found that the composites performed typical electrochemical supercapacitor behavior.

Morphological, Mechanical, Thermal, Electrical and Rheological Properties of Polycarbonate Composites Reinforced with Surfaces Modified Mica

The mica fillers reinforced Polycarbonate (PC) composites were fabricated using compression molding technique. The mica surface was chemically modified using vinyltrimethoxy silane and 3–Aminopropyltriethoxy silane. The properties of treated mica PC composites were examined in terms of scanning electron microscopy, thermo gravimetric analysis, differential scanning calorimetry and rheological behavior. The modified mica was observed to disperse more uniformly than the unmodified counterpart. The tensile strength and modulus also improved with treated mica filled PC composites. Polycarbonate (PC) / mica composites were prepared by twin screw extruder at 250 °C. Rheological behavior of PC/mica composites was investigated. The PC / mica composites were characterized by parallel plate rheometer system. As increasing the mica particle size and the content, storage and loss modulus of the PC / mica composites were increased.

Polyetheretherketone (PEEK) Composites Reinforced with Fly Ash and Mica

Polyetheretherketone (PEEK) composites were developed using fly ash and mica as fillers. PEEK composites of 5-30 wt% loading were compounded using twin screw extruder. Tensile strength, tensile modulus and flexural modulus increased with the incorporation of both the fillers in PEEK matrix. Tensile modulus of PEEK fly ash composites was found to be higher than PEEK mica composites. Charpy impact strength of PEEK mica composites improved drastically up to 15 wt% of filler but in PEEK fly ash composites charpy impact strength was decreased. The effect of fly ash and mica on the percentage crystallinity of PEEK composites was studied by using modulated differential scanning calorimeter (MDSC). Limiting oxygen index (LOI) of PEEK fly ash and mica composites also improved by 11% and 24% respectively than pure PEEK at 30 wt% loading respectively. The dynamic modulus of PEEK composites shows over 133% increment at 100-250 °C, indicating improvement of elevated temperature mechanical properties. Effects of filler on the morphology of PEEK composites have also been discussed.

Effect of Particle Size and Concentration on Mechanical and Electrical Properties of the Mica Filled PVC

The performance of the composites is determined on the basis of the interface bonding of the filler and the polymer matrix. Particulate filled polymer composites are used extensively for their wide range of applications at low cost. In this study, the effect of the mica with different particle size and different filler concentration (10 to 50 weight percent) on the mechanical and electrical properties of the polyvinyl chloride (PVC) was investigated. The PVC composites of water ground mica were prepared by Haake Rheocord 9000 machine, with Rheomix 600 using rotor type roller blades. Mechanical properties such as stiffness, and Young’s modulus of the PVC mica composites were found increasing with increase in mica loading, whereas elongation at break and tensile strength was found to be decreasing with the mica loading. Dielectric strength and surface resistance were found increasing with increasing mica loading whereas there was no significant increase of arc resistance of the composites. Morphological studies revealed that there is good dispersion and wetting of the mica with PVC matrix. SEM micrographs of the composites were studied for finding the filler dispersion and fracture analysis of the test samples.

Micas from the Khaluta carbonatite deposit, western Transbaikal region

The Khaluta carbonatite deposit located in the western Transbaikal region was formed during the Late Mesozoic rifting in the southern framework of the Siberian Craton. Carbonatite is associated with shonkinite and syenite and is accompanied by fenitization. The composition of mica in more than 160 samples of country rocks, carbonatites, silicate rocks, and fenites was studied. The Fe3+ and Fe2+ contents, as well as oxygen isotopic composition, were determined. The Mg and Fe contents increase, whereas the Ti and Al contents decrease in micas when passing from silicate rocks and fenites to carbonatites. Micas from carbonatites are depleted in Al, enriched in Fe3+, and distinguished by high Si and F contents. According to our calculations, in some cases Al replaces Si in the tetrahedral site instead of replacement of Fe3+ as is characteristic of tetraferriphlogopite. Formally, the mica from carbonatites falls within the tetraferriphlogopite field, but typical inverse pleochroism is not always observable. The δ18O values of micas from carbonatite, shonkinite, syenite, and fenite are similar to those of mantle-derived silicate minerals. The δ18O values in the minerals coexisting with phlogopite testify to their isotopic equilibrium and make it possible to calculate the crystallization temperature of carbonatite.

Dating microstructures by the 40Ar/39Ar step-heating technique: Deformation–pressure–temperature–time history of the Penninic Units of the Western Alps

White micas from the Penninic units of the Urtier Valley, in the Western Alps, have been dated by the 40Ar/39Ar step-heating method. A strong correlation is observed between measured ages, mica composition and deformation fabrics. Samples characterized by a single mineral reservoir yielded relatively flat age spectra, allowing to estimate an age of 44.4±0.4Ma for the formation of phengite-bearing fabrics in eclogite facies conditions (SHP) and an age of 42.0±0.4Ma for the microstructurally younger muscovite-bearing shear fabrics, which formed in greenschist facies conditions (SZgr1). Several micaschist samples are characterized by the overprint of the phengite-bearing SHP fabric by a younger muscovite-bearing fabric (FU) that is axial planar to tight upright folds that post-date the SZgr1 shearing event. BSE images reveal that the different generations of syn-kinematic micas are not exclusively tied to their respective fabric, but muscovite is commonly found also in the SHP microlithons, while relict phengite is often transposed into the new FU axial planar fabric. All the samples containing these two generations of white micas yielded convex-upward spectra, which, following considerations based on the 36Ar/40Ar Vs 40Ar/39Ar plots, have been interpreted to indicate mixing of two argon reservoirs of different ages, related to the older phengite and the younger muscovite visible with optical and electron microscopy. This method allowed to estimate a maximum age of ca. 36.5±0.5Ma for the folding of the shear-related structures. The ages estimated for SHP and SZgr1 in the study area are consistent with those obtained in other parts of the Penninic units with other geochronological techniques. Therefore, the post-crystallization loss of argon from the phengite associated with SHP and the muscovite defining SZgr1 is negligible, despite evidence indicating that conditions of T=480–510°C were reached during the later upright folding event.

Major- and trace-element compositional variation of phlogopite from kimberlites and carbonatites as a petrogenetic indicator

Ferromagnesian trioctahedral micas are a common macrocryst/phenocryst phase in kimberlites and carbonatites. We explored the possibility of using the chemistry of ferromagnesian micas to discriminate between these rocks in order to assess their economic potential. We determined the extent of major- and trace-element variations of micas from 14 selected kimberlite and carbonatite localities worldwide representing several different kimberlite fields and alkaline–carbonatite provinces. Phlogopite macrocrysts from kimberlites follow two principal evolutionary trends: primary macrocrystic (involving an increase in Ba, Al, Ti, Cr, Zr, Nb and Sr contents at decreasing Mg towards the rim) and transitional macrocryst-groundmass trend (involving an increase in kinoshitalite component at decreasing Fe, Ti and Cr contents). Micas from (dolomite–)calcite carbonatites cover a much greater compositional range than those from kimberlites, defining evolutionary trends towards annite, tetra-ferriphlogopite and kinoshitalite. Our data confirm that macrocrystic micas from kimberlites cannot be reliably distinguished from carbonatitic phlogopite on the basis of their major-element compositions. Exceptions are Fe–Al-rich [Fe/(Fe + Mg) ≥ 0.2] and Na-rich (> 0.3 wt.% Na 2O) micas that seem to be virtually restricted to carbonatites. The generally higher levels of Na in carbonatitic micas relative to those from kimberlites can be explained by the lower Na abundances in the latter relative to carbonatites. Our data indicate that the trace-element composition of mica determined by LA-ICP-MS can be used as a reliable petrogenetic indicator. Kimberlitic phlogopite is characteristically enriched in Cr (up to 12030 ppm), Ni (up to 1600 ppm) and Co (40–70 ppm), and depleted in Mn (≤ 280 ppm), Nb (≤ 28 ppm), Sr (≤ 55 ppm), Sc (≤ 8 ppm), Zr (≤ 12 ppm) and, to some extent, Cs (≤ 7 ppm) and Ta (≤ 3 ppm) with respect to carbonatitic micas (≤ 315 ppm Cr, ≤ 470 ppm Ni, ≤ 34 ppm Co, up to 17200 ppm Mn, 1080 ppm Nb, 830 ppm Sr, 80 ppm Sc, 105 ppm Zr, 27 ppm Cs and 19 ppm Ta). With the exception of Zr, the observed differences in trace-element composition of mica probably reflect the contrasting trace-element geochemistry of kimberlitic and carbonatitic magmas. The depletion of kimberlitic phlogopite in Zr (and possibly, Nb + Ta) can be explained by sequestration of these elements in the earlier-crystallized ilmenite. Variations in Ba, Rb and V contents are similar in mica from both rock types and cannot be used as a petrogenetic indicator.

Nitrogen‐Enriched Nonporous Carbon Electrodes with Extraordinary Supercapacitance

AbstractNitrogen‐enriched nonporous carbon materials derived from melamine–mica composites are subjected to ammonia treatment to further increase the nitrogen content. For samples preoxidized prior to the ammonia treatment, the nitrogen content is doubled and is mainly incorporated in pyrrol‐like groups. The materials are tested as electrodes for supercapacitors, and in acidic or basic electrolytes, the gravimetric capacitance of treated samples is three times higher than that of untreated samples. This represents a tenfold increase of the capacitance per surface area (3300 µF cm−2) in basic electrolyte. Due to the small volume of the carbon materials, high volumetric capacitances are achieved in various electrolytic systems: 280 F cm−3 in KOH, 152 F cm−3 in H2SO4, and 92 F cm−3 in tetraethylammonium tetrafluoroborate/propylene carbonate.

The role of a novel p‐phenylen‐bis‐maleamic acid grafted atactic polypropylene interfacial modifier in polypropylene/mica composites as evidenced by tensile properties

AbstractPresent work is devoted to the study of the tensile behavior of polypropylene (PP)/mica composites with improved interfacial interactions from the matrix side caused by the presence of a p‐phenylen‐bis‐maleamic acid grafted atactic polypropylene (aPP‐pPBM) as an interfacial agent. Hence, aPP‐pPBM was previously obtained, in our laboratories, by reactive processing in the melt of a by‐product (atactic PP) from industrial polymerization reactors. Present article is two‐fold, on one hand it has been planned to evidence the so called interfacial effects caused by this novel interfacial agent (aPP‐pPBM) yielding better final properties of the heterogeneous system as a whole as revealed by tensile mechanical properties, and on the other to obtain models to forecast the overall behavior of the system. For such purpose, a Box‐Wilson experimental design considering the amount of mica particles and of interfacial agent as independent variables was used to obtain polynomials to forecast the behavior of the PP/Mica system in the experimental space scanned. The existence of a critical amount of aPP‐pPBM to optimize mechanical properties appears to emerge. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The effect of shear on mechanical properties and orientation of HDPE/mica composites obtained via dynamic packing injection molding (DPIM)

AbstractThe interfacial interaction and orientation of filler play important roles in the enhancement of mechanical performances for polymer/inorganic filler composites. Shear has been found to be a very effective way for the enhancement of interfacial interaction and orientation. In this work, we will report our recent efforts on exploring the development of microstructure of high density polyethylene (HDPE)/mica composites in the injection‐molded bars obtained by so‐called dynamic packing injection molding (DPIM), which imposed oscillatory shear on the melt during the solidification stage. The mechanical properties were evaluated by tensile testing and dynamic mechanical analysis (DMA), and the crystal morphology, orientation, and the dispersion of mica were characterized by scanning electron microscopy and two‐dimensional wide‐angle X‐ray scattering. Compared with conventional injection molding, DPIM caused an obvious increase in orientation for both HDPE and mica. More importantly, better dispersion and epitaxial crystallization of HDPE was observed on the edge of the mica in the injection‐molded bar. As a result, increased tensile strength and modulus were obtained, accompanied with a decrease of elongation at break. The obtained data were treated by Halpin–Tsai model, and it turned out that this model could be also used to predict the stiffness of oriented polymer/filler composites. Copyright © 2009 John Wiley & Sons, Ltd.

Experimental study of fluorine and chlorine contents in mica (biotite) and their partitioning between mica, phonolite melt, and fluid

This paper reports the results of a study of the composition of mica (biotite) crystallizing in the system of phonolite melt-Cl- and F-bearing aqueous fluid at T ∼ 850°C, P = 200 MPa, and $$ f_{O_2 } $$ = Ni-NiO, as well as data on F and Cl partitioning between coexisting phases. It was established that Cl content in mica is significantly lower than in phonolite melt and, especially, in fluid. Fluorine shows a different behavior in this system: its content in mica is always higher than in phonolite melt but lower than in fluid. The mica-melt partition coefficients of Cl and F also behave differently. The Cl partition coefficient gradually increases from 0.17 to 0.33 with increasing Cl content in the system, whereas the partition coefficient of F sharply decreases from 3.0 to 1.0 with increasing total F content. The apparent partition coefficients of F between biotite and groundmass (melt) in various magmatic rocks are usually significantly higher than the experimental values. It was supposed that the higher Bt/glassDF values in natural samples could be related to the influence of later oxidation reactions, reequilibration of biotite at continuously decreasing $$ f_{H_2 O} $$ /f HF ratio, and an increase in this coefficients with decreasing total F content in the system.

Sensitive Colored Hybrid Inorganic/Organic Pigments Based on Polymer-Coated Microsized Particles

We present herein the preparation of colored hybrid organic/inorganic pigments: poly(styrene- co-alizarin)/mica. We have used direct nitroxide-mediated radical polymerization of styrene and modified alizarin from mica-bound bicationic azo compounds as initiator. The color of the P(S-co-A)-mica composites is related both to the adsorption density of polymers on mica surface and to the length of the macromolecular chains. The longer the polymerization time is, the more the chains are crushed onto the mica surface and the nearer the dye is to the surface. Consequently, the dye will be strongly influenced by the oxanions of the surface leading to color variation. This variation has been attributed to the superimposition of different adsorption of the alizarin due to different states: when closer to the surface, alizarin is more influenced by oxanions and its color tends to pink, when farther away from the surface, the alizarin electronic state is less changed and its color tends to yellow. Finally, the global color is due to the mix of the different electronic states leading to orange pigments. This behavior could be represented as a gradient of alizarin position from the mica surface to the air/polymer interfaces. Depending on the synthesis methodology, the color of such pigments can be easily tuned not only by adjustment of the length and the grafting density but also by the number of dyes in the chains.