Silica Quartz Research Articles

Experimental Investigation on Reactive Powder Concrete by Partial Replacement of Cement with Different Pozzolanic Materials

Abstract: Reactive powder concrete (RPC) is one of the ultra-high performance concrete (UHPC). In RPC the coarse aggregate is eliminated and the micro particles like silica fume, quartz powder and sand are utilized in the production process. The high cement content and low water to binder ratio in RPC lead to shrinkage problems. Hence in this study, an attempt is made to produce eco-friendly RPC by replacing cement with 3 different pozzolanic materials from industrial wastes such as Fly ash, GGBS and Granite powder. To assess the viability of partial replacement of cement by pozzolanic materials, nine mixes have been arrived with 10%, 20% and 30% replacements. The fresh concrete property such as slump and the compressive strength are determined for all the mixes. By comparing the strength property the suitable alternate replacement material and replacement percentage for cement in RPC is found out

Implication of the diagenetic evolution, litho- and microfacies types on the storage capacity of the carbonate rocks in West Esh El Mallaha area, SW onshore Gulf of Suez, Egypt

The present study shed the light on the main litho- and microfacies of the Upper Cretaceous- Miocene sequence exposed at West Esh El Mallaha area (Egypt) with more focus on the carbonate rocks. Delineating the implication of the recorded facies and the diagenetic processes on the storage capacity of the entire sequence is among the prime targets of this study. The studied Esh El Mallaha sequence includes the Nubia, Duwi, Dakhla, Tarawan, Esna, Thebes, Abu Gerfan, Gharamul and Gemsa Formations, from older to younger respectively. The carbonate rocks exposed in the studied sequence were deposited in shallow marine, lagoonal outer ramp and environments with high energy and/or open marine conditions. These depositional environments are represented by ten microfacies types: lime-mudstone, foraminiferal wackestone, bioclastic wackestone, algal wackestone/packstone, foraminiferal packstone, bioclastic packstone/grainstone, phosphatic packstone/grainstone, oolitic and bioclastic grainstone, oyster rudstone and bafflestone. Aggrading neomorphism, calcite cementation (drusy calcite, pseudosparite, and poikilotopic calcite), silicification (silica cementation in the form of amorphous silica, micro-quartz, chalcedony and spherulitic quartz), compaction, clay mineral alteration, dissolution, fracturing and dolomitization are the main diagenetic processes recorded in the studied section.The storage capacity of the different rock units were primarily obliterated by multi-cementation phases by calcite, silica and/or clay minerals. Nonetheless, fracturing, dissolution and dolomitization enhanced the storage capacity and can be considered the main storage capacity-enhancing features in the studied sequence. These diagenetic features are more abundant in the studied Duwi, Thebes, Abu Gerfan and Gharamul Formations. This achievement indicates that the studied Upper Cretaceous- Miocene carbonate sequence may be promising in its subsurface extensions in the Gulf of Suez and other analogues in Egypt.

Experimental Study on the Properties of Autoclave Curing High-Strength Concrete According to CaO/SiO2 Ratio

In this experimental study, tests were conducted to obtain the CaO/SiO2 (C/S) molar ratio that minimizes the micropores of hardened concrete. To this end, the compressive strength, thermogravimetric analysis (TGA), and microporous structure of hardened concrete were investigated using concrete specimens made with silica fume and quartz powder under high-temperature/high-pressure conditions. The tests yielded the following results: (1) the highest compressive strength (200 MP) was exhibited in the C/S molar ratio range of 0.7–0.9, and lower compressive strength was exhibited in the C/S molar ratio ranges of ≤ 0.6 and ≥ 0.95; (2) the productivity of calcium silicate hydrate (C-S-H) tended to increase in proportion to the C/S molar ratio in all specimens; (3) the microstructure was measured using mercury intrusion porosimetry (MIP), and the maximum total porosity of specimens was calculated to be 10%. As the C/S molar ratio increased, the total porosity decreased, as did the pore diameter and threshold pore diameter. Thus, C/S molar ratio was found to be a major factor affecting the compressive strength and microporous structure of autoclave-cured cement and the optimal mechanical properties were exhibited in the C/S molar ratio of 0.8–0.9. However, the reactivity varies depending on the material used and curing conditions employed. Therefore, the hydration products obtained using the curing conditions need to be investigated further.

HIGH STRENGTH MANGO LEAF WASTE/POLYURETHANE COMPOSITE REINFORCEMENT USING QUARTZ MATERIAL

Quartz stone contains silica components (SiO2) which have the ability as a reinforcement material for composite materials. Quartz SEM-EDX testing shows that the quartz silica comonent is 69%. Other components contained in quartz are 34% MgO and 2% CaO. Therefore, quartz stone is used as a reinforcing material in mango leaf waste composite materials. Meanwhile, compressive strength testing of composite materials was carried out with variations of Polyurethane (PU) polymers, namely 1, 2, 3, 4, 5, 6, and 7 grams, obtaining the highest maximum pressure at 6 grams polymer mass, which is 38.91 grams. Testing of composite materials that have been given a mixture of quartz stone with a mass of Polyurethane (PU) 6 grams and a quartz stone variation of 0.03; 0,06; 0,09; 0,12; 0,15; and 0.18 grams obtained the maximum power most optimally there is a quartz mass of 0.06 grams of 40.47 grams. The strength of mango leaf composite meets the strength standard for building materials, namely concrete with a value of 20-150 MPa. This shows that quartz stone can be a composite reinforcement comprehenent for mango leaf waste.

High-temperature heat transfer simulation and optimization of quartz fiber-aerogel composite multilayer 3D fabric

Quartz fabrics, which have excellent mechanical properties and high temperature resistance abilities, had been widely applicated in aerospace, military, and other thermal insulation fields. However, single-layer quartz fabric has poor thermal insulation performance, which is unfavorable to the high temperature application of this material. In order to improve the thermal insulation effect of quartz fiber fabric, silica aerogel materials with outstanding thermal insulation performance were introduced to the fabrication of quartz fabrics. Thermal insulation properties of quartz fiber and mechanical properties of silica aerogel were improved by a 3D braiding technique. Firstly, a 3D-fabric structure of quartz fiber-aerogel multilayer composite was designed. Silica aerogel and quartz yarn were woven into 3D composite fabric by textile technique. Through 3D braiding technique, silica aerogels were protected by quartz yarns while enhancing their mechanical properties. The thermal insulation performance and high temperature erosion resistance of the fiber-aerogel fabric are improved. Secondly, to explore the influence of the internal structure of the 3D fiber-aerogel composite fabric, a full-scale 3D simulation model for the heat transfer performance of fiber-aerogel multilayer composite was established. The thermal insulation performance of the composite fabric at 700 °C was predicted. Finally, the temperature of different positions inside the fabric in different environments (300 °C, 400 °C, 500 °C, 600 °C, 700 °C) was tested. It has been proved that introducing aerogel materials to the quartz fabric could reduce the surface temperature by about 60%.

The location of the chemical bond. Application of long covalent bond theory to the structure of silica.

Oxygen is the most abundant terrestrial element and is found in a variety of materials, but still wanting is a universal theory for the stability and structural organization it confers. Herein, a computational molecular orbital analysis elucidates the structure, stability, and cooperative bonding of α-quartz silica (SiO2). Despite geminal oxygen-oxygen distances of 2.61-2.64Å, silica model complexes exhibit anomalously large O-O bond orders (Mulliken, Wiberg, Mayer) that increase with increasing cluster size-as the silicon-oxygen bond orders decrease. The average O-O bond order in bulk silica computes to 0.47 while that for Si-O computes to 0.64. Thereby, for each silicate tetrahedron, the six O-O bonds employ 52% (5.61 electrons) of the valence electrons, while the four Si-O bonds employ 48% (5.12 electrons), rendering the O-O bond the most abundant bond in the Earth's crust. The isodesmic deconstruction of silica clusters reveals cooperative O-O bonding with an O-O bond dissociation energy of 4.4kcal/mol. These unorthodox, long covalent bonds are rationalized by an excess of O 2p-O 2p bonding versus anti-bonding interactions within the valence molecular orbitals of the SiO4 unit (48 vs. 24) and the Si6O6 ring (90 vs. 18). Within quartz silica, oxygen 2p orbitals contort and organize to avoid molecular orbital nodes, inducing the chirality of silica and resulting in Möbius aromatic Si6O6 rings, the most prevalent form of aromaticity on Earth. This long covalent bond theory (LCBT) relocates one-third of Earth's valence electrons and indicates that non-canonical O-O bonds play a subtle, but crucial role in the structure and stability of Earth's most abundant material.

Influence of intermittent opening density on mechanical behavior and fracture characteristics of 3D-printed rock

To investigate the influence of intermittent opening density on the mechanical behavior and fracture characteristics of rock, sand 3D-printed specimens containing different opening numbers are prepared using quartz silica sand and furan resin adhesive as printing substrates. Uniaxial compression testing is performed on these rock-like specimens. Based on digital image correlation (DIC) technology, a methodology for identifying crack types and evaluating rock damage is proposed to quantify the mechanical mechanism of crack evolution during loading. The experimental results are verified and explained using the rock failure process analysis (RFPA) code. The results show that with increasing intermittent opening density, the stress–strain curves of the specimens are similar. Meanwhile, the increase in intermittent opening density causes the stress field distribution of the specimen to change, which in turn leads to a decrease in the uniaxial compressive strength and elastic modulus. The types of cracks around the opening can be grouped into tensile cracks (T) and shear cracks (S), and the coalescence modes of the rock bridge between the openings can be grouped into shear coalescence (C1) and traction coalescence (C2). As the intermittent opening density increases, the coalescence type between openings changes from C1 to C2, and the overall failure pattern is converted from tensile-shear failure to tensile failure. The damage factor (Df) evolution is closely related to the intermittent opening density of the specimens. A one-way exponential decay correlation between the stress ratio and the damage factor is found. The above study is expected to deepen the understanding of the deformation and fracture mechanism of rock masses with openings and to provide a reference for the application of 3D printing technology in the rock mechanics field.

Micro-characterization of Dust and Materials of Dust Origin at a Cement Industry Located in Bangladesh

Industrial dust generation from material processing is an uninterrupted phenomenon, hence analyzing materials of dust origin with dust particles is important to comprehend the entire scenario of occupational health exposure (OHE). In this study, we investigated the morphological, elemental, and mineralogical characteristics of engendered dust and materials of dust origin in the cement industry (CI) in Bangladesh. The dust samples were accumulated from dust collectors and the internal roadways of the CI to understand the nature of atmospheric dust of the CI. All the materials that could potentially be the sources of the dust of the CI were collected, including clinker, gypsum, limestone, fly ash, slag, and two types of cement products. Scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDS), x-ray powder diffraction (XRD), and fourier-transform infrared spectroscopy (FTIR) were performed for the characterization. SEM micrographs showed the presence of fine (particles ≤ PM2.5) and ultra-fine (particles ≤ PM0.1) particles with diverse morphology in the studied samples. Ca, Si, Al, Mg, Fe, K, Na, Mo, and Ti were found as existing metallic elements in samples through the EDS technique. Several minerals of silicate, oxide, carbonate, and sulfate were detected with major crystalline phases of Portland cement by SEM-EDS, XRD, and FTIR analyses in samples; among which some are well documented as occupational hazards. The trace presence of organic carbon was observed in all FTIR spectra. The most significant outcome of this study is the detection of carcinogenic substances such as crystalline silica (quartz, cristobalite) and asbestoses (anthophyllite, chrysotile, and crocidolite) in samples. For instance, quartz was found in the dust of dust collectors while road dust of the CI showed the existence of both quartz and cristobalite. However, asbestoses were found only in source materials, but they could be released anytime during material handling, thus creating OHE.

Thickness dependence of microwave dielectric tunability in Ba0·5Sr0·5TiO3 thin films deposited by pulsed laser deposition

In this study, the Ba 0·5 Sr 0·5 TiO 3 (BST) thin films with different thicknesses are fabricated on fused silica quartz substrate by using the pulsed laser deposition (PLD) technique. The deposition was done using a laser fluence of ∼2 J/cm 2 and the number of pulses was varied from 2500 to 20,000 to change the thickness of the thin films. X-ray diffraction (XRD) patterns and Raman spectrum were used for the phase confirmation. The FESEM technique was used to observe the microstructure of BST thin films and the average grain size was found to be 208, 255, 267, 300, and 393 nm for the BST thin films with thicknesses of 150, 300, 450, 600 and 1000 nm. The optical bandgap ( E g ) of all films was ∼3.54 eV. Dielectric properties of the BST thin films were measured not only in the low-frequency region (1 kHz-1 MHz) but also in the microwave frequency region (0.5 GHz-4 MHz). The microwave dielectric properties of the BST thin films were also measured as a function of voltage using the circular patch capacitor (CPC). The highest microwave tunability was found to be ∼55.5% for the BST thin film with a thickness of 300 nm. It was found that too small a film thickness where the polarizable dipoles are constrained by proximity to an amorphous substrate and thick films where the grains approach the size of that in bulk are not suitable for yielding high dielectric tunability.

Copper-Bearing Mineralisation in the Upper Devonian Limestones: A Case Study from the Historical Teresa Adit in the Świętokrzyskie Mountains, Poland

The studied copper ore deposit is located in Miedzianka Mountain (Świętokrzyskie Mountains, central Poland). This deposit was exploited from the 13th century to the 1950s; therefore numerous historical adits are currently present. One of these is Teresa adit (established in 1805), consisting of underground mining corridors and natural cave developed in the Upper Devonian limestones, partially transformed by mining works. Samples of copper- and rock-forming minerals in limestones collected at seven sites within the richest copper-bearing mineralisation in this adit were studied with petrographic investigation of thin sections, micro-area chemical analysis (EDS), and XRD. This study shows the presence of various minerals: (a) Cu-Fe sulphides (relics of chalcopyrite) and Cu sulphides (covellite, chalcocite), (b) Cu-Fe oxides (cuprite and hematite), (c) Ca and Cu carbonates (calcite, azurite, and malachite), (d) clay minerals (Fe-Mg illite), and (e) micro-crystalline silica (quartz). For the first time in the studied deposit, we described chalcopyrite relics in cuprite pseudomorphosis, hematite with admixture of vanadium in pinkish-creme veins in limestones, and the presence of an admixture of Fe-Mg illite and microcystaline silica within cracks of limestones. In addition, for the first time, unit cell parameters of malachite and azurite from Miedzianka Mountain were determined, indicating very low substitutions of atoms other than Cu in their structures. We suppose that the minerals studied were formed during three types of copper mineralisation processes: (a) hydrothermal (relics of chalcopyrite), (b) secondary weathering (chalcocite, covellite, cuprite, hematite), and (c) adsorptive mineralisation (azurite, malachite). The latter stage is related to residuum, which consists of a mixture of Fe-Mg illite and micro-crystalline quartz, which was formed during the dissolution of limestones in karst processes in some crevices. We proposed a model of the formation of copper carbonates in the adsorption stage of the copper-bearing mineralisation in Miedzianka Mountain deposits. Two generations of calcite veins (older—red calcite and younger—crème-pinkish calcite) were also detected. Mineralogical–petrographical studies of samples revealed a high scientific and educational value. Due to the fact that the Teresa adit is planned to be made available to geotourists, this work is worth presenting to the public either in the adit and/or in a local museum in Miedzianka village.

Preparation and analysis of multi-scale colored superhydrophobic coatings with excellent mechanical strength and self-cleaning properties

Since most commercial building coatings are porous in structures, the building facades are easily to be damaged by acid rain, harmful particles in the air, and drastic temperature changes. Superhydrophobic coatings have great potential to solve these problems on account of their excellent water-repellent and self-cleaning properties. Previous studies have focused on improving the durability of superhydrophobic coatings. However, a colorful superhydrophobic coating that meets both durability and aesthetic requirements is rarely reported. Therefore, we developed a self-cleaning and colorful superhydrophobic (SCS) coating consisting of silica nanoparticles (nano-SiO2 particles), quartz sands, silicone sealant, and latex paint. The thickness of the SCS coating could be adjusted from 0.05 to 0.3 mm, the average contact angle (CA) was 155.09 ± 1.9° and the average sliding angle (SA) was 3.6 ± 0.2°. The SCS coating could be still retained superhydrophobicity after 350 cycles of mechanical abrasion under the weight of 200 g and 100 cycles of tape peeling. It was shown that there were no evident changes after immersing in chemical solutions and irradiating under ultraviolet (UV) light in the aging test. The mechanism of the excellent performance was studied by scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The facile fabricated SCS coating with excellent mechanical stability, anti-corrosion, and UV-resistance performance is expected to apply in the building engineering field for keeping clean and waterproof.

Authigenic silica in continental lacustrine shale and its hydrocarbon significance

Taking lake basin shales of the Triassic Yanchang Formation in the Ordos Basin, NW China and the Cretaceous Qingshankou Formation in the Songliao Basin, NE China as research objects, the characteristics and origins of different types of silica in the shales have been studied by means of core observation, thin section identification, cathodoluminescence, X-ray diffraction analysis, scanning electron microscope (SEM), electron probe and rock pyrolysis. The results shows that the origins of silica include felsic mineral dissolution, tuffite devitrification, clay mineral transformation and siliceous mineral metasomatism. The silica formed by feldspar dissolution commonly appears as spots and veins, with low degree of crystallization, and is largely aqueous opal mineral, with an average SiO2 content of 67.2%. Silica formed by devitrification of tuffite mainly occurs in two forms, amorphous silica and authigenic quartz with better crystal shape. The authigenic silica formed during the transformation of clay minerals is embedded in the clay minerals in the form of micron-scale plates and small flakes, or mixed with clay minerals in a dispersed state. The authigenic quartz formed by siliceous mineral metasomatism is in better angular crystal shape, and has an average SiO2 content of 87%. The authigenic siliceous mineral content is positively correlated with the content of terrigenous felsic minerals. The pressure solution of felsic minerals is the main source of authigenic siliceous minerals, followed by the transformation of clay minerals, and the organic matter has some boost on the formation of authigenic silica. The authigenic siliceous materials of different origins have different geological characteristics and occurrence states from terrigenous quartz, which would affect the storage performance, seepage capacity and fracturing effect of continental shale. Although the organic-rich shale has high silica content, different from terrigenous quartz, authigenic silica in this kind of shale mostly floats and disperse in clay minerals, which would have negative effect on the formation of complex fractures in fracturing, fracture support ability after fracturing, and formation of effective seepage channels. Calculating the brittleness index of shale intervals only based on the composition of brittle minerals cannot accurately characterize mechanical characteristics of continental shale oil reservoirs, and would affect comprehensive evaluation and selection of continental shale oil “sweet spots”.

An inter-laboratory effort to harmonize the cell-delivered in vitro dose of aerosolized materials

Air-liquid interface (ALI) lung cell models cultured on permeable transwell inserts are increasingly used for respiratory hazard assessment requiring controlled aerosolization and deposition of any material on ALI cells. The approach presented herein aimed to assess the transwell insert-delivered dose of aerosolized materials using the VITROCELL® Cloud12 system, a commercially available aerosol-cell exposure system. An inter-laboratory comparison study was conducted with seven European partners having different levels of experience with the VITROCELL® Cloud12. A standard operating procedure (SOP) was developed and applied by all partners for aerosolized delivery of materials, i.e., a water-soluble molecular substance (fluorescence-spiked salt) and two poorly soluble particles, crystalline silica quartz (DQ12) and titanium dioxide nanoparticles (TiO2 NM-105). The material dose delivered to transwell inserts was quantified with spectrofluorometry (fluorescein) and with the quartz crystal microbalance (QCM) integrated in the VITROCELL® Cloud12 system. The shape and agglomeration state of the deposited particles were confirmed with transmission electron microscopy (TEM).Inter-laboratory comparison of the device-specific performance was conducted in two steps, first for molecular substances (fluorescein-spiked salt), and then for particles. Device- and/or handling-specific differences in aerosol deposition of VITROCELL® Cloud12 systems were characterized in terms of the so-called deposition factor (DF), which allows for prediction of the transwell insert-deposited particle dose from the particle concentration in the aerosolized suspension. Albeit DF varied between the different labs from 0.39 to 0.87 (mean (coefficient of variation (CV)): 0.64 (28%)), the QCM of each VITROCELL® Cloud 12 system accurately measured the respective transwell insert-deposited dose. Aerosolized delivery of DQ12 and TiO2 NM-105 particles showed good linearity (R2 > 0.95) between particle concentration of the aerosolized suspension and QCM-determined insert-delivered particle dose. The VITROCELL® Cloud 12 performance for DQ12 particles was identical to that for fluorescein-spiked salt, i.e., the ratio of measured and salt-predicted dose was 1.0 (29%). On the other hand, a ca. 2-fold reduced dose was observed for TiO2 NM-105 (0.54 (41%)), which was likely due to partial retention of TiO2 NM-105 agglomerates in the vibrating mesh nebulizer of the VITROCELL® Cloud12.This inter-laboratory comparison demonstrates that the QCM integrated in the VITROCELL® Cloud 12 is a reliable tool for dosimetry, which accounts for potential variations of the transwell insert-delivered dose due to device-, handling- and/or material-specific effects. With the detailed protocol presented herein, all seven partner laboratories were able to demonstrate dose-controlled aerosolization of material suspensions using the VITROCELL® Cloud12 exposure system at dose levels relevant for observing in vitro hazard responses. This is an important step towards regulatory approved implementation of ALI lung cell cultures for in vitro hazard assessment of aerosolized materials.

Speleothems in sandstone crevice and boulder caves of the Elbe River Canyon, Czech Republic

A variety of speleothems are present in crevice and boulder caves developed in Cretaceous sandstones of the Elbe River Canyon in northern Czech Republic. A set of complementary instrumental mineralogical methods was applied to characterize the speleothems and cave dripwaters, including X-ray powder diffraction, scanning electron microscopy and microanalysis, Raman spectroscopy and optical emission spectrometry. Four morphological types were distinguished and characterized in terms of their mineral and chemical composition: 1, rusty brown mud-dominated coatings with micro-gours, composed of a mixture of clay minerals; 2, white “chalky” coatings (moonmilk) composed of calcite with minor gypsum; 3, cauliflower-shaped coralloids composed of calcite and silica in a layered structure, with gypsum layers in apical parts; 4, knob coralloids, dark gray-brown with smooth surfaces and distinctly layered structures, composed of silica (quartz, opal-A) and Si–Al phases (kaolinite) and including phosphate-rich laminae (sasaite, vashegyite, taranakite). Only modest microbial mediation of silica precipitation was observed in cauliflower-shaped coralloids while no clear signs are present in knob coralloids despite organic enrichment in the topmost layer. White “chalky” coatings and cauliflower-shaped coralloids precipitated from weakly acidic Ca-, Mg- and sulphate-rich deeper sandstone percolates. These forms are probably still active, much like the micro-gours, produced by particulate clay deposition. Formation of knob coralloids combined clay deposition and the dominant silica precipitation from pore waters similar to the present shallow acidic percolates under changing climatic conditions, probably in the Pleistocene. It was favored by specific rock lithology (quartzose sandstone with kaolinite admixture), which explains the scarcity of similar forms in sandstone caves. Concentration of knob coralloids along protruding vertical edges and the presence of wind-guided forms suggests that silica precipitation was driven by evaporation under a constant air flow.

Direct non-oxidative methane coupling on vitreous silica supported iron catalysts

Direct non-oxidative methane coupling (NMC) is one of the promising pathways for methane upgrading into value-added olefin and aromatic hydrocarbons. The silica-supported iron (i.e., Fe/SiO2) catalyst has been reported effective for NMC, but the effects of silica support on the catalyst property and NMC performance have rarely been explored. In this work, we prepared a vitreous silica-supported iron (Fe/SiO2-V) catalyst by flame fusion of a mixture of quartz silica and fayalite. The physicochemical properties and NMC performance of the as-prepared catalysts were measured. Compared to crystalline cristobalite support in Fe/SiO2 catalyst that has been studied previously, vitreous silica support has disordered Si-O bonds and structural defects, enabling better iron dispersion and more vital metal-support interaction. The as-prepared Fe/SiO2-V catalyst had a shorter induction period in methane activation and lower coke yield in NMC. The increase in iron concentration in Fe/SiO2-V catalysts elongated the catalyst induction period and promoted aromatics and coke formation. The coke type of the spent Fe/SiO2-V catalyst is more uniform than the cristobalite-supported iron catalyst.

Thermomechanical and optical characteristics of nanoquartz‐ and nanozircon‐filled poly(methyl methacrylate) composites

AbstractThe thermomechanical and optical properties of poly(methyl methacrylate) (PMMA)/quartz and PMMA/zircon composites at filler content variations of 0, 1, 2.5, and 5 wt% have been studied. The silica quartz and zircon powders were derived from local sands collected from Tanah Laut, South Kalimantan, and Kereng Pangi, Central Kalimantan, Indonesia, respectively. The nanoquartz and nanozircon fillers (herewith were designated as quartz and zircon respectively) were obtained by milling these powders for 15 h. Dynamic mechanical analysis was used to acquire the storage modulus and glass transition temperature as the thermomechanical properties of the PMMA/quartz and PMMA/zircon composites. Meanwhile, the optical properties were determine using ultraviolet–visible spectroscopy. Results indicate that zircon fillers can improve the storage modulus of the composites up to 1.85 times that of PMMA alone. Zircon is more effective than silica in improving the storage modulus of PMMA. Implementing the degradation rate model shows us that all the composites have nearly the same degradation behavior in the glassy region. Moreover, the addition of fillers decreases the band gap energies.

Optical and electrical properties of GaZnO films deposited by co-sputtering method on two types of substrates

ABSTRACT Gallium zinc oxide GaZnO (GZO) thin films are deposited on silica glass and quartz substrates using DC power and RF power on ZnO and GaO targets, respectively. Structural characteristics are investigated using X-ray diffraction XRD, optical parameters such as refractive index n, optical energy gap Eop and dispersion parameters in addition to the electrical property are investigated for all considered films. The optical properties reveal that GZO films have high transmittance (70–98%) and a low absorption coefficient in the visible range of the spectra. The optical band gap was found to increase from 3.28 to 3.44 eV with increasing the RF power on GaO target. The dielectric constant of GZO was found to be larger than the dielectric loss and has high optical conductivity (≈1015 S−1), The VELF and SELF values of GZO films are calculated and investigated.

Geothermometry in High-Temperature Reservoirs of the Geothermal Springs in Southern Thailand: Insights from Cations and Silica Geothermometers

Geothermal springs have provided a unique opportunity to study the geothermal system of geological processes. A reservoir temperature estimation based on the chemical geothermometers is vitally essential for assessing the exploration and development of geothermal resources. The paper represents the various techniques of geothermometers with comparisons between the silica (quartz and chalcedony) and the cation geothermometers (Na–K–Ca and K–Mg) for the high exit temperature (temp. ≥55°C) of geothermal springs in southern Thailand. The Na–K–Ca geothermometer presented more elevated reservoir temperatures than the K–Mg, silica and chalcedony geothermometers, about 20–30◦C. The preliminary assumed difference between the geothermometers may indicate that the shallow subsurface conditions are mixed with groundwater

Incorporation of a high volume of cenosphere particles in low water-to-cement matrix for developing high strength and lightweight cementitious composites

The incorporation of a high volume of lightweight aggregates generally results in a reduction of mechanical properties. To overcome this intrinsic problem, this study used a high volume of cenosphere particles (10–20 wt.% of cement) along with silica fume and quartz powder in a very dense microstructure. The reactivity of the cenospheres in the composites was investigated by X-ray diffraction and thermogravimetric analysis. Furthermore, microcomputed tomography was used to visualize the cenosphere particles in the designed cementitious composite for ensuring uniform distribution. The experiments showed that compressive strengths of 64–74 MPa and 87–90 MPa at 28 days of curing were achieved under ambient (20 °C) and high (90 °C) temperature, respectively. Furthermore, it exhibited significantly low density and thermal conductivity compared to other cementitious composites with cenospheres. Finally, the role of the cenospheres in the designed cementitious matrix was limited to inert filler, and no direct evidence of a chemical reaction was observed.

Adhesion and Cohesion of Silica Surfaces with Quartz Cement: A Molecular Simulations Study.

This study focuses on developing an adhesive and cohesive molecular modeling approach to study the properties of silica surfaces and quartz cement interfaces. Atomic models were created based on reported silica surface configurations and quartz cement. For the first time, molecular dynamics (MD) simulations were conducted to investigate the cohesion and adhesion properties by predicting the interaction energy and the adhesion pressure at the cement and silica surface interface. Results show that the adhesion pressure depends on the area density (per nm2) and degree of ionization, and van der Waals forces are the major contributor to the interactions between the cement and silica surfaces. Moreover, it is shown that adhesion pressure could be the actual rock failure mechanism in contrast to the reported literature which considers cohesion as the failure mechanism. The bonding energy factors for both “dry” and “wet” conditions were used to predict the water effect on the adhesion pressure at the cement–surface interface, revealing that H2O can cause a significant reduction in adhesion pressure. In addition, relating the adhesion pressure to the dimensionless area ratio of the cement to silica surfaces resulted in a good correlation that could be used to distribute the adhesion pressure in a rock system based on the area of interactions between the cement and the surface. This study shows that MD simulations can be used to understand the chemomechanics relationship fundamental of cement–surfaces of a reservoir rock at a molecular/atomic level and to predict the rock mechanical failure for sandstones, limestones, and shales.