Sheet Mica Research Articles

Ballistic Charge Transport by Mobile Nonlinear Excitations

The developments in hyperconductivity, the loss‐free transmission of electric charge at room temperature and above, due to the ballistic transport of electric charge in crystals with quasi‐layered structure, are reported. The electric charge is carried by quodons, a type of mobile nonlinear intrinsic localized mode of lattice excitation observed as fossil tracks in layered silicates and recently by laboratory experiments. Here, ballistic means moving with minimal scattering or interaction with phonons. A test for hyperconductivity in solid materials is developed. It is based on the unique effect of short‐term continuation of transport of charge, by total internal reflection, after creation of quodons has ceased. This effect is called the slow‐quodon‐decay effect or SQD effect. So far, only layered silicates have been shown to exhibit hyperconductivity. New evidence is presented for hyperconductivity in chrysotile, a nonlayered silicate material with new results. Being a fibrous material, it is more flexible than the sheet mica phyllosilicates. It is found that quodons can also be created and carry charge in very different materials, such as polymers, but without showing hyperconductivity, because of the very short range and lifetime of quodons in those materials.

Exploitation of Mica Deposits at Nellore Mica Belt, Andhra Pradesh, India

India is the leading producer of sheet mica and a major part of this is exported. Nellore mica belt is the largest mica-producing area covering part of Nellore district in Andhra Pradesh, India. As most of the mines are old and privately operated, they are developed and operated purely based on local experiences. In this article, we highlight the problems associated with the present mica-mining practices in the Nellore mica belt, and scientific approaches that have been adopted for fixing different parameters associated with mica extraction. Based on detailed field study, geo-mechanical data and tested rock properties, extensive numerical modelling is done to suggest the best possible method of mining for safe and sustainable mica extraction from the area.

Transforming ground mica into high-performance biomimetic polymeric mica film

Biomimetic assembly of high-quality nanosheets into nacre-like structures can produce macroscopic films with favorable mechanical and optical performances due to the intrinsic properties and high level of ordering of the nanoscale building blocks. Natural ground mica is abundant and exhibits great application potential. However, large size and low aspect ratio greatly limit its biomimetic assembly. Moreover, exfoliation of ground mica into high-quality nanosheets remains a significant challenge. Here, we report that large-scale exfoliation of ground mica into mono- or few-layered mica nanosheets with a production rate of ~1.0 g h−1 can be successfully achieved. The mica nanosheets are then assembled into strong biomimetic polymeric mica film that inherits the high electric insulation, excellent visible transmittance, and unique ultraviolet-shielding properties of natural mica. Its overall performance is superior to that of natural sheet mica and other biomimetic films, making the polymeric mica film a suitable substrate for flexible and transparent devices.

Contrast Characteristics of the Muscovitic Quartzite from Karelia, Russia - Determining the Possibility of Intensification of the Beneficiation Process

The use of muscovite is determined by its industrial look and quality. Sheet mica is traditionally used as electrically insulating material. Crushed mica dry or wet grinding and scrap (waste from the production of sheet mica) are used as electrical insulating material (for example, mica paper), filler in the manufacture of various kinds of fillers, grout and paint etc. In addition, today there is a steady demand for micronized muscovite for the production of decorative coatings and cosmetics.On the territory of the Republic of Karelia (Russian Federation) there is a significant number of deposits and occurrences moscoviticarum rocks. Promising target small iron-poor Muscovite is the manifestation of the Eastern Hitware identified in 1999. The average mineral composition of rocks of the productive series: quartz – 10-71%; Muscovite – 8-42%; plagioclase – 1,5-28%; kyanite – 2-13,5%; biotite, and 0.1-8%; ore (pyrite, sphalerite) and 1.5 – 11%.Enrichment of this type of mineral raw materials may be carried out using traditional methods – gravity, magnetic separation, flotation. Textural-structural and mineralogical features, a high degree of secondary changes (thin intergrowths of muscovite with graphite, ferritization, the decrease of the strength characteristics) and the availability of areas and dedicated silicification abundant pyrite mineralization and its vein type significantly impoverish muscovite ore, necessitate the adjustment of technological schemes and modes of enrichment. Possibilities of improvement of processes of pretreatment and subsequent enrichment is possible using the methods of pre-sorting that represent rational and cost-effective alternative to traditional beneficiation processes. To explore the possibility of using the optical methods being preconcentration, experimental study of the contrast of properties of samples of the original ore. The study was carried out on crushed material, graded by size: -10+5; -20+10; -40+20 -60 and+40 mm. the results revealed the main search area colour shades in images of mineral samples in the colour system HLS – grey, brown, bright yellow-orange and purple. The correlation between the colour characteristics of the individual pieces and the content of muscovite. To implement the sort method of photometric separation, the threshold separation can be determined by one of the highlighted areas of the gamut or in their entirety. Next, the sorted ore with the same mineralogical and structural properties can effectively be enriched with gravitational methods. In the complex process of enrichment, it is possible to obtain, in addition to muscovite, quartz and kyanite products, which undoubtedly will increase the output of marketable products.

GEOCHEMICAL ANALYSIS OF MICA SOURCE SPECIMENS AND ARTIFACTS FROM THE ABBOTT FARM NATIONAL HISTORIC LANDMARK (28ME1)

The Abbott Farm National Historic Landmark is one of the more significant Woodland-period sites in the Northeast. Numerous Hopewellian cultural traits (copper artifacts, cremated burials, exotic cherts, and mica) have been identified at the site. Numerous potential geological sources for the mica artifacts exist in the Mid-Atlantic region. We explore two analytical methods to evaluate the most likely geological sources of the mica artifacts. Source and artifact specimens were analyzed using pXRF as well as neutron activation. Our pXRF data are suggestive, but show high analytical uncertainty. We make several recommendations relevant to future attempts that would use this kind of instrument to study sheet mica. Our neutron activation results are promising and suggest that geochemical sourcing of mica has much potential. Results of both assays suggest that most of the artifact specimens recovered from Abbott Farm share a similar chemistry, and this composition is very similar to mica from southeastern Pennsylvania. A cut-and-drilled pendant exhibits a chemical makeup distinctly different from all other artifacts and source specimens evaluated here. Although our results are preliminary, the application of modern analytical methods to extant archaeological collections has the potential to provide significant new information.

Procedencia de la mica de Teotihuacan: control de los recursos suntuarios foráneos por las élites gobernantes

This article describes the provenance and contexts in which mica (phlogopite or biotite) has been found, as a foreign raw material imported from the Valley of Oaxaca, in the great metropolis of Teotihuacan in Central Mexico, during the Classic period (first 6 centuries CE). More than 90% of the mica found in the Classic city is concentrated in two compounds at Teotihuacan: the Xalla Palace, to the north of the Sun Pyramid, and the Viking Group, to the south of the Sun Pyramid, both sites that were related to the city's governing elite. In contrast to the large amount of mica in these contexts is the small amount (measured in grams) found in multi-ethnic neighborhood centers such as Teopancazco, which were also excavated by this project.The approximately 37kg of sheet mica found in Xalla during the project “Teotihuacan. Elite and government” (Linda R. Manzanilla, 1997-2016) occurs as cut plaques, triangles, trapezoidal figures, rectangles and circles, as well as flake mica and dust. At Xalla, they were used on the lower part of the walls; as circles incorporated as “eyes” in theater-type censers found in Oztoyahualco 15B; and as disks and angular geometric figures in important burials at Teopancazco.Through archaeometric studies (X-ray diffraction, scan electron microscopy, neutron activation), mica from Xalla and Teopancazco is characterized and compared with sources of mica in the Valley of Oaxaca (Las Trancas near San Francisco Telixtlahuaca, Paraje Loma Gorda near Cuilapan, Loma Yaguín near Santo Tomás Jalieza, the modern mine of Minerales de Antequera S.A. in Ocotlán de Morelos) and with Prehispanic mica from the archaeological sites of Monte Albán, Cerro de las Minas, and Huamelulpan in Oaxaca. Most of the Prehispanic mica may have come from the area of the modern mine of Minerales de Antequera S.A. in Ejutla.

Deposition of high permeability FeCoN films on mica substrates

In this study, sheet mica was explored as an alternative substrate for thin film deposition due to its unique layered structure and atomically flat surface. Static magnetic properties and microwave permeability of sputtered FeCoN films on mica with and without SiO2 under-layer were examined. In-plane isotropy and a large coercivity of 70 Oe were observed for the film directly deposited on mica substrate. With the insertion of 40 nm SiO2 under-layer between the film and mica substrate, well-defined in-plane anisotropy is formed due to the significant reduce in film residual stress, associated with a 3 Oe coercive force along easy axis. As a result, excellent microwave properties have been achieved and are comparable with the same film on Si substrate. Moreover, the permeability spectra are surprisingly stable from room temperature up to 390 K. Mica is proved as a promising substrate for magnetic films with high microwave performance, which is a great advantage for practical applications. Furthermore, our r...

Ion implantation doping and electrical conductivity enhancement of C 60 films

Pristine C 60 films sublimed onto sheet mica were implanted with 20 keV K + ions and I + ions at doses of 1.0 × 10 16/cm 2, 3.0 × 10 16/cm 2 and 5.0 × 10 16/cm 2, and with 20 keV Ar + ions at a dose of 5.0 × 10 16/cm 2. The distributions of dopants were studied using Rutherford backscattering spectrometry (RBS). The temperature dependence of sheet resistivity of the films was investigated applying a four-probe system. It was proposed that the conductivity enhancement of K + implanted C 60 films was due to the implanted ions in the films, while for I + implanted C 60 films, both implanted I + ions and irradiation effects of the ions contributed to the enhancement of conductivity.

Measuring the electrical resistance of metals to 40 GPa in the diamond-anvil cell

A four-probe technique is described for measuring the electrical resistance of metals in a diamond-anvil cell at pressures up to 40 GPa. The pressure range for electrical resistance measurements was extended by developing insulating gaskets that provide the necessary support for the diamonds and the electrical leads at the diamond edges. The various gasket materials and construction methods that were tested fall into two categories: (1) gaskets made entirely of insulating materials, and (2) gaskets made of metal coated with insulating materials. Gaskets developed in each category were used successfully in making resistance measurements up to 40 GPa. The most reliable gaskets were composites of sheet mica and MgO powder. This report describes the testing and development of the gaskets and presents electrical resistance data obtained for iron and beryllium to 40 GPa.

The electrical double-layer properties of the mica (muscovite)-aqueous electrolyte interface

Electrophoresis and streaming potential data are reported for crushed and sheet muscovite mica respectively. For streaming potential measurements a newly designed radial flow apparatus was used. Measurements on crushed mica show that both aluminium and silicon leach out of the mica. Leached aluminium and silicon may readsorb to confer increased positive and negative charge respectively on the mica. Electrophoresis data indicate that leaching of aluminium occurs more rapidly than of silicon. Aging experiments on sheet mica show leaching effects to be much slower than on crushed mica. Streaming potential measurements on freshly cleaved mica sheets showed that (i) the zeta- potential depended strongly on electrolyte (KCl) concentration; (ii) the zeta-potential was relatively independent of pH and (iii) monovalent cations were adsorbed in the sequence H+ > Cs+ > K+ > Na+ > Li+, whilst Ca2+ adsorbed more strongly than K+. It is proposed that the structure of the electrical double layer at the mica/electrolyte interface results from the distribution of all ions between the diffuse layer, the Stern plane (hydrated) and more critically the lattice holes of the silica-alumina basal plane.

Thermal Behavior of Muscovite Sheet Mica.

The three spectral types of muscovite sheet mica, i.e., very pink ruby, light green, and dark green, were subjected to heat treatments at temperatures up to 600 °C. The changes in the apparent optic axial angle and in the absorption spectra (0.3 to 15 μ) were studied along with color.The differentiation of muscovite sheet according to these spectral types extends to the behavior of apparent optic axial angle and to certain regions of the spectrum under heat treatment. The pink associated absorption region (0.47 to 0.6 μ) can be enhanced or bleached away by appropriate thermal treatment, although the associated infrared multiplet at 3 to 3.5 μ is little affected. The absorption band at 12 μ increases in intensity with temperature of treatment. It is suspected that the 0.47 to 0.6 μ absorption is the result of color centers.

Correlation of Muscovite Sheet Mica on the Basis of Color, Apparent Optic Angle, and Absorption Spectrum.

A detailed experimental study of color, apparent optic angle, and absorption spectrum (0.3 to 16μ of λ) indicates that there are basic chemical and structural differences in muscovite micas. Color identification is based upon spectrophotometer measurements. A method for quantitative evaluation of absorption band activity is defined so that single and multiple band intensities within the spectrum of an individual specimen and within spectra of different specimens can be compared. Three basic spectral types exist for the 0.3 to 1μ λ region which are comprised of various weak lines and absorption regions lying along the base of a deep absorption edge near 0.32μ. Of the three spectral types, one is associated with ruby micas, while the other two are associated with dark green and light green micas. The activities of numerous lines and bands are reported. It is shown that apparent optic axial angle is related to the position of the deep band edge except for a certain class of ruby specimens which show anomalous values. A definitive characterization of muscovite sheet is formulated in terms of the absorption coefficients at 0.44, 0.49, and 0.58μ. Direct associations are shown between certain lines in the visible λ range and certain bands in the near infrared, while the activities of a number of bands in the middle infrared are correlated to color.

SHEET MICA IN BRAIN SURGERY

To the Editor: —Referring to the article on Repair of Dural and Brain Defects by Drs. Halstead and Caylor (The Journal, April 26), permit me to call attention to the value of sheet mica (stove isinglass) for this purpose. I once published an article on the subject pointing out the superiority of this (mineral glass) to others as a covering for exposed and damaged brain tissue. Sheet mica can be obtained at any hardware store or, in emergency, removed from the glass windows of heating stoves. It can be split to any amount of thickness from a solid block to that of the thinnest tissue paper. It is smoother than glass; absolutely nonirritant, indestructible, nonadherent to the tissues: a window for observation of the part on which it is applied; is elastic and difficult to break, and can be cut with scissors into whatever size or shape required. Not least