Presence Of Mica Research Articles

Characteristics and control factors of feldspar dissolution in gravity flow sandstone of Chang 7 Member, Triassic Yanchang Formation, Ordos Basin, NW China

To clarify the formation and distribution of feldspar dissolution pores and predict the distribution of high-quality reservoir in gravity flow sandstone of the 7th member of Triassic Yanchang Formation (Chang 7 Member) in the Ordos Basin, thin sections, scanning electron microscopy, energy spectrum analysis, X-ray diffraction whole rock analysis, and dissolution experiments are employed in this study to investigate the characteristics and control factors of feldspar dissolution pores. The results show that: (1) Three types of diagenetic processes are observed in the feldspar of Chang 7 sandstone in the study area: secondary overgrowth of feldspar, replacement by clay and calcite, and dissolution of detrital feldspar. (2) The feldspar dissolution of Chang 7 tight sandstone is caused by organic acid, and is further affected by the type of feldspar, the degree of early feldspar alteration, and the buffering effect of mica debris on organic acid. (3) Feldspars have varying degrees of dissolution. Potassium feldspar is more susceptible to dissolution than plagioclase. Among potassium feldspar, orthoclase is more soluble than microcline, and unaltered feldspar is more soluble than early kaolinized or sericitized feldspar. (4) The dissolution experiment demonstrated that the presence of mica can hinder the dissolution of feldspar. Mica of the same mass has a significantly stronger capacity to consume organic acids than feldspar. (5) Dissolution pores in feldspar of Chang 7 Member are more abundant in areas with low mica content, and they improve the reservoir physical properties, while in areas with high mica content, the number of feldspar dissolution pores decreases significantly.

Engineering geological characterization of micaceous residual soils considering effects of mica content and particle breakage

The engineering geological characteristics of micaceous residual soil (MRS), which is prevalent in subtropical regions, are markedly influenced by the presence and breakage of mica particles. Nevertheless, a comprehensive understanding of the underlying mechanisms responsible for these effects remains elusive. In this study, a series of experimental tests were conducted on two groups of reconstituted MRS samples. These samples were prepared by mixing natural MRS, from which the original mica had been removed, with intact and crushed mica powder, respectively. The aim was to investigate the effect of the mica content and particle breakage on the physical and mechanical properties of MRS. Scanning electron microscopy was employed to scrutinize the microstructural alternations of mica particles at different states of breakage, and a conceptual model was proposed based on the observations. The findings revealed that the presence of mica considerably altered the physical properties of MRS, resulting in higher Atterberg limits but lower plasticity, along with unfavorable mechanical properties, including high compressibility and swelling potential, low compactability, stiffness, strength, and ductility. The microstructural analysis elucidates that these effects stem from the resilient nature of layered mica flakes with high water-retention capacity. On the other hand, the breakage of mica particles changed these effects. The disappearance of interlayered voids following mica particle breakage leads to reduced Atterberg limits and enhanced compaction efficiency of the mixture. Moreover, MRS with a higher proportion of crushed mica exhibited more significant deformation and compression during shearing. This behavior can be attributed to the diminished stiffness of crushed mica and weaker interparticle contacts within the soil matrix. This study provided a multi-scale insight into how mica affected the engineering geological properties of MRS and proposes references for more effectively incorporating of MRS into engineering construction projects.

Correlations between mineral composition and mechanical properties of granite using digital image processing and discrete element method

This study investigated the correlations between mechanical properties and mineralogy of granite using the digital image processing (DIP) and discrete element method (DEM). The results showed that the X-ray diffraction (XRD)-based DIP method effectively analyzed the mineral composition contents and spatial distributions of granite. During the particle flow code (PFC2D) model calibration phase, the numerical simulation exhibited that the uniaxial compressive strength (UCS) value, elastic modulus (E), and failure pattern of the granite specimen in the UCS test were comparable to the experiment. By establishing 351 sets of numerical models and exploring the impacts of mineral composition on the mechanical properties of granite, it indicated that there was no negative correlation between quartz and feldspar for UCS, tensile strength (σt), and E. In contrast, mica had a significant negative correlation for UCS, σt, and E. The presence of quartz increased the brittleness of granite, whereas the presence of mica and feldspar increased its ductility in UCS and direct tensile strength (DTS) tests. Varying contents of major mineral compositions in granite showed minor influence on the number of cracks in both UCS and DTS tests.

Polypropylene‐based nanocomposite with improved mechanical properties: Effect of cellulose nanofiber and polyrotaxane with partial miscibility

AbstractThe mechanical properties and miscibility of polymer‐based composites containing cellulose nanofiber (CNF) and polyrotaxane (p‐rtx) as organic fillers were studied in detail. CNF and p‐rtx were introduced as powders into a polypropylene (PP) matrix, and composites were prepared using a simple melt‐compounding method. The best mechanical properties were achieved when CNF and p‐rtx were loaded at a concentration of 0.6 wt%. The Young's modulus of the composite increased by 760 MPa compared with that of the PP matrix. In addition, the presence of mica in the composite promoted the epitaxial growth of PP along the (1 3 0) plane. The various shifts in the melting/crystallization temperatures of the composites prepared at different CNF:p‐rtx ratios confirmed the partial miscibility between the fillers and the matrix. The enhancement in the mechanical properties of the composite is believed to be due to the miscibility of the surfaces of aggregates of the organic fillers with PP and the uniform dispersion of the organic fillers in the matrix.

Chemical and Mechanical Characterization of Unprecedented Transparent Epoxy–Nanomica Composites—New Model Insights for Mechanical Properties

Two nanomicas of similar composition, containing muscovite and quartz, but with different particle size distributions, have been used to prepare transparent epoxy nanocomposites. Their homogeneous dispersion, due to the nano-size, was achieved even without being organically modified, and no aggregation of the nanoparticles was observed, thus maximizing the specific interface between matrix and nanofiller. No exfoliation or intercalation has been observed by XRD, despite the significant dispersion of the filler in the matrix which produced nanocomposites with a loss in transparency in the visible domain of less than 10% in the presence of 1% wt and 3% wt of mica fillers. The presence of micas does not affect the thermal behavior of the nanocomposites, which remains similar to that of the neat epoxy resin. The mechanical characterization of the epoxy resin composites revealed an increased Young's modulus, whereas tensile strength was reduced. A peridynamics-based representative volume element approach has been implemented to estimate the effective Young's modulus of the nanomodified materials. The results obtained through this homogenization procedure have been used as input for the analysis of the nanocomposite fracture toughness, which has been carried out by a classical continuum mechanics-peridynamics coupling approach. Comparison with the experimental data confirms the capability of the peridynamics-based strategies to properly model the effective Young's modulus and fracture toughness of epoxy-resin nanocomposites. Finally, the new mica-based composites exhibit high values of volume resistivity, thus being excellent candidates as insulating materials.

Granitic quarry waste as a dual functional filler for high density polyethylene‐based composites: Mechanical and microwave absorbing properties

AbstractCost‐effective polymeric composites were successfully prepared by melt blending granitic quarry waste (GQW) with high‐density polyethylene (HDPE). The GQW is a waste generated during the production of manufacture fine aggregates (MFA) from crushed gneiss rock and contains significant amount of mica with iron in its structure. Different sieving and milling procedures were employed. The materials were characterized by mechanical and dynamic‐mechanical properties and scanning electron microscopy. Moreover, the influence of the GQW on the microwave absorbing properties in the X‐band frequency range was investigated. The presence of mica and iron compound in the GQW provides a dual function to the filler: toughening agent with microwave absorbing capacity. Indeed, the addition of 5 wt% of GQW previously sieved and milled by dry or wet‐grinding approach resulted in composites with outstanding toughness, modulus and elongation at break. Simulated RL studies revealed electro‐magnetic attenuation of −25 dB at 8.7 GHz. Such successful use of a waste generated in the production of a concentrate (MFA) not only contributes to the economics of the quarrying operation, but also to its environmental sustainability, since it replaces disposal of this product, which could lead to dust emissions, given its fine size and low moisture content.

Behaviour of hard stones submitted to different foot traffic

Building stones when submitted to wear conditions can change their appearance and eventually lose the characteristics for which they were chosen, leading to expensive and undesired material replacement. The physical–mechanical properties of the stones should fit their application purposes to ensure the desired durability, as in covering floors submitted to intense foot traffic. This paper presents the results of the evaluation carried out of some properties of the stone floor, composed of honed finished slabs of granite (Branco Micaela) and gabbronorite (Nero Impala), applied in a commercial zone for 10 years. The assessment of colour, roughness and gloss were carried out in 105 slabs. Beyond the colour differences, granite is lighter than gabbronorite, though both stones have chromatic homogeneity. There are also differences in surface roughness and gloss, with Branco Micaela showing a higher roughness and a lower gloss. Mineralogical composition, mainly the presence of micas, and the grain size govern the polishing of the stones, which affect the roughness and gloss. Nero Impala has large minerals and shows better polishing, whilst Branco Micaela, with more contacts and detachable micas, is more susceptible to losing mineral fragments, consequently showing higher roughness and less gloss. There is a wear difference between the areas of high and low pedestrian foot traffic, though these differences do not significantly modify the aesthetic characteristics of the floor. The use of honed finishing proved to be a good option to prevent the undesirable evolution of surface characteristics.

Comparing transient and steady-state methods for the thermal conductivity characterization of a borehole heat exchanger field in Bergen, Norway

A comparative study was carried out aiming at characterizing the thermal conductivity of rocks sampled in a borehole heat exchanger field. Twenty-three samples were analysed with four different methods based on both steady-state and transient approaches: transient divided bar (TDB), transient line source (TLS), optical scanning (OS), and guarded hot plate (GHP). Moreover, mineral composition (from XRD analyses), P-wave velocity, and density were investigated to assess the petro-physical heterogeneity and to investigate possible causes of divergence between the methods. The results of thermal conductivity showed that TLS systematically underestimates thermal conductivity on rock samples by 10–30% compared to the other devices. The differences between TDB and OS, and GHP and OS are smaller (about 6% and 10%, respectively). The average deviation between TDB and GHP, for which the specimen preparation and the measurement procedure were similar, is about 10%. In general, the differences are ascribable to sample preparation, heterogeneity and anisotropy of the rocks, and contact thermal resistance, rather than the intrinsic accuracy of the device. In case of good-quality and homogeneous samples, uncertainty can be as low as 5%, but, due to the above-mentioned factors, usually uncertainty is as large as 10%. Opposite relationships between thermal conductivity and P-wave velocity were observed when analysing parallel and perpendicular to the main rock foliation. Perpendicular conductivity values grow with increasing perpendicular sonic velocity, while parallel values exhibit an inverse trend. Thermal conductivity also appears to be inversely correlated to density. In quartz-rich samples, high thermal conductivity and low density were observed. In samples with calcite or other likely dense mineral phases, we noticed that lower thermal conductivity corresponds to higher density. The presence of micas is likely to mask major differences between silicate and carbonate samples.

Effect of mica content on pore pressure and stress-strain response of micaceous sand using energy dissipation and different failure mechanisms

ABSTRACT Mica particles are platy, flexible and resilient in nature having numerous intact mica flakes foliated over each other with low stiffness. Presence of mica among sand particles creates complex geometric arrangements due to bridging, ordering or pore filling phenomena; which make micaceous sand highly compressible with low shear strength. When flaky mica particles are augmented among spherical sand particles, the governing shear behaviour mechanisms substantially varies due to redistribution of contact forces among sand-sand matrix, sand-mica matrix and mica-mica matrix formation of micaceous sand. The current experimental study investigated the effect of mica content on pore pressure and stress-strain behaviour of micaceous sand due to varying sand-mica microstructural evolutions. The variation in shear strength parameters were studied under different failure criteria: peak deviatoric stress and peak effective stress ratio. The deviations in mechanical behaviour of micaceous sand at varying mica content were further examined through cumulative dissipated strain energy mechanisms to understand the inter-particle contact-force transfer mechanisms for varying sand and mica matrix.

Fabrication and Characterization of Electrospun PVA/Mica Fibrous Nanocomposite Mats

ABSTRACTThis paper focuses on the fabrication of cost effective and high performance poly(vinyl alcohol)/mica fibrous nanocomposites using electrospinning. Effective incorporation of fine particles of mica in poly(vinyl alcohol)/mica nanocomposites was examined and confirmed along with the evidence of good dispersion, by digital optical microscopy and scanning electron microscopy. The presence of mica improved the mechanical properties of the nanocomposites without affecting the thermal stability. The electrospun poly(vinyl alcohol) mats containing 20 wt% mica exhibited tensile strength of 13.29 MPa and tensile modulus of 180.3 MPa as compared to values of 3.92 and 83 MPa, respectively, for poly(vinyl alcohol) fiber mats.

Physicochemical, Geochemical and Mineralogical Aspects of Agricultural Soils in Limpopo Province, South Africa

ABSTRACTSoil samples were collected from three selected sites (uncultivated, cultivated and grazing land) at University of Limpopo Experimental Farm (Syferkuil) in Mankweng area to characterise their physicochemical, geochemical and mineralogical properties and their influence on soil fertility for agriculture. Soil textural triangle using Texture Auto Lookup Software (TAL 4.2) Package was used to determine particle sizes of samples which were all dominated by a loamy texture. Chemical characterisation carried out included determination of exchangeable cations, major elemental oxides and trace elements. Silica was the dominant oxide with the highest weight percentage values ranging from 75.99 to 83.45. Chemical index of alteration values of 66 to 75 depicted moderate silica weathering with depletion of soil nutrients due to leaching. Seven minerals were identified i n soil samples which were dominated by kaolinite. The presence of mica and smectites in the soils displayed properties typical of soils rich ...

Sedimentological characteristics and geochemistry of lake waters of the Rio Grande basin, west of Bahia State (Brazil)

ABSTRACTThe lacustrine system of the Rio Grande basin is placed where it gathers singularities from both geological and climatic points of view. In order to understand the origin and dynamics of this system, a faciological description of the deposits from two lakes considers both textural and mineralogical elements via XRD analyses. This was followed by a chemical analysis of a dozen lakes' water, in order to standardize the evolution of the lowlands which form the lakes. The hydrochemical data revealed two trends: one group of lakes presented sodium and base, and the other group calcium and acid. Both these groups also presented some differences in their sediment characteristics, registering round pebbles, a higher percentage of sand and presence of mica in one of the lakes, contrasting with the muddy texture with predominance of quartz and kaolinite in the other lake. Such results allowed the proposition of two evolutionary models for the lakes of the São Francisco Lowlands, which share the same climate; evidence that the other landscape elements affect the system's dynamics. One of the models is represented by lakes that evolved from little permeable sedimentary rocks. These rocks, however, are more fractured, favouring the lakes area expansion and more water permanence with recent links to the river network. On the other proposed model, the lakes evolved from permeable but less fractured carbonic rocks with rapid vertical water infiltration and less water permanence, which reflects more atmospheric than lithological influence in their geochemical characteristics. This study provides important information for the comprehension of this landscape evolution.

Evaluation of asphalt mastic containing mica due to aging

Asphalt concrete consists of coarse aggregate, fine aggregates, fillers and binder. Fines passing a #200 sieve are called fillers, and most often contain mica. Previous studies show that the presence of mica reduces the strength of asphalt concrete. This study evaluates the mineral and chemical composition of asphalt mastic containing mica. Five different concentrations of mica were added to the fines and then X-ray diffraction (XRD) was used to identify the mineralogy of the mica and the presence of mica. An XRD pattern can differentiate mica from fillers and determine the presence of mica in fines. Then mastic containing different percentages of mica was aged and examined with a scanning electron microscope and a bending beam rheometer to determine the chemical composition and low-temperature stiffness. Scanning electron microscopy showed that, with the addition of mica, the microstructure of mastic changed and the number of uncoated flakes increased. However, the number of uncoated flakes decreased with aging. Also for high concentrations of mica, the presence of oxygen and sulfur decreased with aging. Bending beam rheometer test results showed that the addition of mica decreased the mastic stiffness. However, the rate of stiffness increase due to aging decreases with the addition of mica. This could suggest that mica reduces the rate of aging.

Filler from crushed aggregate for concrete: Pore structure, specific surface, particle shape and size distribution

Characteristics of fine particles (0–125μm diameter) from seven different crushed and natural sands from five different Norwegian rock types were determined. The results suggest that the same water absorption values, as determined by EN 1097-6 on coarser sand fractions, can be applied to the fines. The values of specific surface area measurements vary widely between different materials and between different measurement methods. BET measurements seem to be strongly affected by the mineralogical composition (presence of mica) and surface morphology (weathering) of the particles. Specific surface area calculated from the particle size distributions (PSD) is mainly dependent on the precision of the test methods in the size range below about 3–5μm, because these small particles contain most of the surface area. Shape measurements by both Dynamic Image Analysis (DIA), which is a 2-D method, and X-ray microcomputed tomography (μCT), which is a 3-D method, have yielded similar relative length-to-thickness aspect ratios of the particles between different mineralogies, though with lower absolute values for DIA due to 2-D projection of 3-D quantities.

Palynology and clay mineralogy of the Deccan volcanic associated sediments of Saurashtra, Gujarat: Age and paleoenvironments

The intertrappean sediments associated with Deccan Continental Flood Basalt (DCFB) sequence at Ninama in Saurashtra, Gujarat yielded palynoassemblage comprising at least 12 genera and 14 species including Paleocene taxa such as Intrareticulites brevis, Neocouperipollis spp., Striacolporites striatus, Retitricolpites crassimarginatus and Rhombipollis sp. The lava flows of Saurashtra represent the northwestern most DCFB sequence in India. It is considered that the Saurashtra lava flows represent the earliest volcanic activity in the Late Cretaceous of the Reunion Mantle Plume on the northward migrating Indian Plate. The present finding of the Paleocene palynoflora from Ninama sediments indicate Paleocene age for the associated lava flows occurring above the intertrappean bed which suggests that the Saurashtra plateau witnessed eruption of Deccan lava flows even during Paleocene. The clay mineral investigation of the Ninama sediments which are carbonate dominated shows dominance of low charge smectite (LCS) along with the presence of mica and vermiculite. Based on the clay mineral assemblage it is interpreted that arid climatic conditions prevailed during the sedimentation. The smectite dominance recorded within these sediments is in agreement with global record of smectite peak close to the Maastrichtian–Paleocene transition and climatic aridity.

Evaluation of Saudi pegmatite and its use in porcelain industry

Pegmatite is the main source of feldspar for ceramics industry. Usage of pegmatite in ceramic industry causes some problems due to the presence of mica and iron oxides. These materials reduce tile strength, hardness and density of the final product leading to low quality ceramic products. Southern Saudi pegmatite separation treatment was carried out in two phases in order to improve the ceramic quality of the feldspar obtained from this pegmatite. The first phase consists of gravitational separation to remove the heavy impurities and in the second phase magnetic separation was carried out to further minimize iron content. Porcelain ceramic batches were prepared by wet-mixing, drying, pressing (semi-dry press) and fired at temperatures from 1000 to 1350 ?C. The porcelain ceramic bodies were prepared and examined by DTA, X-ray diffraction, SEM and tested for bulk density, linear shrinkage, water absorption and flexural strength. These results indicated that, after treatment (gravity and magnetic separation), the pegmatite can be considered as a good source of potash feldspar. The present study provides a positive indication for using of Southern Saudi pegmatite after treatment in ceramic industries.

Aggregation properties of a short peptide that mediates amyloid fibril formation in model proteins unrelated to disease

Short peptides have been identified from amyloidogenic proteins that form amyloid fibrils in isolation. The hexapeptide stretch ²¹DIDLHL²⁶ has been shown to be important in the self-assembly of the Src homology 3 (SH3) domain of p85 alpha subunit of bovine phosphatidylinositol-3-kinase (PI3-SH3). The SH3 domain of chicken brain alpha- spectrin, which is otherwise non-amyloidogenic, is rendered amyloidogenic if ²²EVTMKK²⁷ is replaced by DIDLHL. In this article, we describe the aggregation behaviour of DIDLHL-COOH and DIDLHL-CONH₂. Our results indicate that DIDLHL-COOH and DIDLHL-CONH₂ aggregate to form spherical structures at pH 5 and 6. At pH 5, in the presence of mica, DIDLHL-CONH₂ forms short fibrous structures. The presence of NaCl along with mica results in fibrillar structures. At pH 6, DIDLHL-CONH₂ forms largely spherical aggregates. Both the peptides are unstructured in solution but adopt beta-conformation on drying. The aggregates formed by DIDLHL-COOH and DIDLHL-CONH₂ are formed during drying process and their structures are modulated by the presence of mica and salt. Our study suggests that a peptide need not have intrinsic amyloidogenic propensity to facilitate the selfassembly of the full-length protein. The propensity of peptides to form self-assembled structures that are nonamyloidogenic could be important in potentiating the self-assembly of full-length proteins into amyloid fibrils.

An identification study of vermiculites and micas: Adsorption of metal ions in aqueous solution

This study deals with the identification of vermiculite in the presence of mica. Three natural silicates were first subjected to expansion by rapid heat treated at 400 °C. Then, the starting silicates and their derived heat-treated products were analyzed by X-ray diffraction, FT-IR spectroscopy, N 2 adsorption at − 196 °C, and helium density measurement. The adsorption of cadmium, chromium, and lead was also carried out. Two of the silicates are composed of mainly biotite and the other of biotite and vermiculite. In general, the results of X-ray diffraction, FT-IR spectroscopy, and helium density measurements are well in agreement. The heat treatment at 400 °C has little effect on the chemical composition, structure, and texture of the silicates. The development of microporosity is small in the silicates. Surprisingly, the adsorption capacity toward chromium and lead is larger for the biotite silicate than for the vermiculite containing silicate.

Characteristics of Acrylic Rubber Composites with Mica and Carbon Black

In this work mica or carbon black were used as filler in composites of acrylic rubber (ACM). The fillers differ not only in nature, mica being a mineral material and carbon black being organic, but also in form and particle size. The content of filler varied from 0 to 50 phr and its influence on ACM was evaluated based on cure parameters, mechanical, and swelling properties. The cure parameters allow the conclusion that the presence of mica does not have a negative effect on the cure or processability; the swelling results indicated a weak interaction between ACM and mica even though the mechanical properties of ACM composition with 40 phr of mica were found to be similar to those of 20 phr carbon black. As a result of mica being less expensive than carbon black, is light colored and easily processible, these properties are of industrial importance. All properties analyzed were compared with gum type composition (without filler).

High shear strain behaviour of synthetic muscovite fault gouges under hydrothermal conditions

Major continental fault zones typically contain phyllosilicates and have long been recognised as zones of persistent weakness. To establish whether the presence of micas can explain this weakness, we studied the frictional behaviour of simulated muscovite fault gouge by performing rotary shear experiments in the temperature range 20–700 °C, under constant effective normal stresses of 20–100 MPa, a fixed fluid pressure of 100 MPa and at sliding velocities of 0.03–3.7 μm/s, reaching shear strains up to 100. Cataclasis causes substantial grain size reduction up to 600 °C. With increasing strain, both pervasive and localized cataclasis and related compaction result in strain hardening, until steady state is reached. This reflects the progressive development of a continuous network of fine grained, hardening bands. Coarse grained relict lenses between these bands show folded and kinked muscovite grains indicative of ductile mechanisms. Samples deformed at 700 °C show evidence for chemical alteration and partial melting. Since our data suggest that muscovite gouge strengthens with depth and strain, it is questionable whether its presence can contribute to the long-term weakness of major crustal fault zones, unless a substantial decrease in strength occurs at shear strain rates lower than attained in our study.