Crystalline Quartz Research Articles

Karakteristik Mineralisasi Endapan Emas Epitermal Sulfidasi Rendah di Daerah Mekarbakti, Kecamatan Bungbulang, Kabupaten Garut, Provinsi Jawa Barat

The southern mountains of western Java have been known to have large gold deposit potential. The Mekarbakti area, located in Garut regency, is known to have gold-bearing quartz veins, but the distribution and characteristics of these veins are not well recorded. The purpose of this study is to determine the geological conditions of the deposits and the characteristics of the epithermal deposits in the study area, in term of alteration, ore mineralization, vein texture, and ore geochemistry. Field work includes random sampling of veins from surface outcrops and cores. Laboratory analysis includes mineragraphic, geochemical analysis by means of Fire Assay Atomic Absorption Spectrophotometry (FA-AAS) and Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) . The lithology of the Mekarbakti area is composed of volcanic rocks including andesite lava, andesite intrusion and pyroclastic rocks such as breccia and tuff. The mapping results show that the hydrothermal alteration that developed is divided into three zones of alteration type, namely the silicification zone (silica + - clay), the argillic zone (kaolinite + - smectite - illite) and the propylitic zone (chlorite - smectite - epidote - illite). Quartz texture is generally dominated by brecciated, colloform, comb, lattice bladed and cockade textures. The texture interpretation of the veins shows a crystalline quartz zone, which is enriched in base metals such as galena, sphalerite and chalcopyrite and a crustiform – colloform zone which usually contains gold and silver. Veins in the study area contain the elevated grades of 3.21 ppm Au and 75.5 ppm Ag.

Atomistic simulation of temperature and defects effects on mechanical properties of selected single and bicrystalline geomaterials

Understanding the nanoscale mechanical properties of rocks, particularly at higher temperatures, has always been a critical issue for high-temperature rock engineering applications. In this study, two geomaterials, including α-quartz and halite salt, are selected to investigate the effect of temperature, defects, including crack and grain boundaries (GB), on the mechanical properties by employing three-dimensional (3D) Molecular dynamics (MD) simulation. Based on this study, the fracture strength of the pristine sample of crystalline α-quartz and halite salt is 110 GPa and 2 GPa, respectively. In this regard, calculated Young's modulus of crystalline α-quartz and halite salt is 94 GPa and 41 GPa, respectively. According to the results, by adding a crack, the maximum fracture strength of α-quartz and halite salt is dropped 61% and 30%, respectively. However, Young's modulus does not change significantly. Also, it is found that increasing the temperature from 400 K to 800 K in crystalline quartz and halite salt, decreases fracture strength by nearly 35% and 42%, respectively. Moreover, by elevating the temperature from 400 K to 800 K in halite salt, the rocks behavior tends to be more ductile. In terms of the impact of grain boundaries on the mechanical response, the fracture stress of α-quartz is dropped down to 45 GPa, and in halite salt, the fracture stress is reduced to 1.6 GPa.

An investigation on the photo-catalytic oxidation of air pollutants via SiO2-supported TiO2

Persistence in the atmosphere of carbon dioxide (CO2) and volatile organic compounds (VOCs) represents a threat for human safety and health, both in the short and in the long term. Therefore, the removal, storage or, even better, utilization of these molecules is currently highly desirable. Photo-catalytic approaches aims to use the sunlight to afford this removal providing a limited or no further pollution. Wide band gap semiconductors are amongst the most studied and employed materials for this purpose. In this study, a crystalline (quartz) and an amorphous (SBA-15) type of silica were tested as TiO2 scaffolds in the photo-oxidation of VOCs. The photo-reduction of CO2 in presence of H2O was also considered as comparative reaction. Therefore, optical, chemical, and reflective properties of the synthesized materials were investigated. The two types of silica showed a different affinity and selectivity in both photo-reductive and photo-oxidative events. The light scattering properties of the scaffold were found to be effective as booster of the photo-catalytic performance of the active phase.

A New Look at Cenozoic Fossil Wood from Thailand

Thailand contains two notable fossil forest regions. Pleistocene fluvial sediments in the Tak region in the northern highlands contain silicified trunks of large trees. Deposits in the Khorat Plateau in northeast Thailand contain a multitude of wood fossils that span a probable age range of Miocene to Pleistocene. At Ban Tak fossil logs are primarily mineralized with crystalline quartz. Incomplete mineralization is characteristic of the Tak wood, with intercellular spaces commonly remaining open. The resulting permeability allows penetration of moisture, and allows introduction of microbes and the accumulation of clays, iron oxides, soluble salts and other materials that may cause discoloration and deterioration. Hydration swelling of these components results in stress. Excavation of the huge logs means that they occupy topographically low positions prone to flooding during the monsoon season. These factors make the fossils vulnerable to weathering. A variety of methods have been employed in attempts to reduce the damage, including the construction of various styles of shelters to protect the fossil logs from direct precipitation. At Khorat, compositions of individual specimens range from pure quartz and pure opal to mixtures of the two polymorphs. Many specimens are preserved indoors in the Khorat Fossil Museum in Mueang Nakhon Ratchasima District, both as indoor exhibits and as outdoor displays in a garden plaza. The environmental complexities at the Tak and Khorat fossil wood localities challenge conservators, but their creative attempts provide useful lessons for future preservation efforts. Our report describes the geologic setting and our research mineralogy of specimens at both localities, and discusses conservation strategies.

Differentiating siliceous particulate matter in the diets of mammalian herbivores

AbstractSilica is crucial to terrestrial plant life and geochemical cycling on Earth. It is also implicated in the evolution of mammalian teeth, but there is debate over which type of siliceous particle has exerted the strongest selective pressure on tooth morphology.Debate revolves around the amorphous silica bodies (phytoliths) present in plants and the various forms of siliceous grit—that is, crystalline quartz (sand, soil, dust)—on plant surfaces. The problem is that conventional measures of silica often quantify both particle types simultaneously.Here we describe a protocol that relies on heavy‐liquid flotation to separate and quantify siliceous particulate matter in the diets of herbivores. The method is reproducible and well suited to detecting species‐ or population‐level differences in silica ingestion. In addition, we detected meaningful variation within the digestive tracts of cows, an outcome that supports the premise of ruminal fluid ‘washing’ of siliceous grit.We used bootstrap resampling to estimate the sample sizes needed to compare species, populations or individuals in space and time. We found that a minimum sample of 12 individuals is necessary if the species is a browser or as many as 55 if the species is a grazer, which are more variable. But a sample size of 20 is adequate for detecting statistical differences. We conclude by suggesting that our protocol for differentiating and quantifying silica holds promise for testing competing hypotheses on the evolution of dental traits.

Gene Expression Profiling of Mono- and Co-Culture Models of the Respiratory Tract Exposed to Crystalline Quartz under Submerged and Air-Liquid Interface Conditions.

In vitro lung cell models like air-liquid interface (ALI) and 3D cell cultures have advanced greatly in recent years, being especially valuable for testing advanced materials (e.g., nanomaterials, fibrous substances) when considering inhalative exposure. Within this study, we established submerged and ALI cell culture models utilizing A549 cells as mono-cultures and co-cultures with differentiated THP-1 (dTHP-1), as well as mono-cultures of dTHP-1. After ALI and submerged exposures towards α-quartz particles (Min-U-Sil5), with depositions ranging from 15 to 60 µg/cm2, comparison was made with respect to their transcriptional cellular responses employing high-throughput RT-qPCR. A significant dose- and time-dependent induction of genes coding for inflammatory proteins, e.g., IL-1A, IL-1B, IL-6, IL-8, and CCL22, as well as genes associated with oxidative stress response such as SOD2, was observed, even more pronounced in co-cultures. Changes in the expression of similar genes were more pronounced under submerged conditions when compared to ALI exposure in the case of A549 mono-cultures. Hereby, the activation of the NF-κB signaling pathway and the NLRP3 inflammasome seem to play an important role. Regarding genotoxicity, neither DNA strand breaks in ALI cultivated cells nor a transcriptional response to DNA damage were observed. Altogether, the toxicological responses depended considerably on the cell culture model and exposure scenario, relevant to be considered to improve toxicological risk assessment.

The effects of silica fume and diatomaceous earth on the mechanochemical activation and pozzolanic activity of kaolin

In this study, the mechanochemical activation of kaolin was combined with the addition of two different pozzolanic substances (silica fume or diatomaceous earth) to modify the structure and pozzolanic activity of kaolinite. The mixtures of kaolin and pozzolanic substances, in mass ratios of 25:75, 50:50, 75:25, and 100:0, were co-ground for the activation. It was performed by high-energy dry grinding to obtain completely (100%) and incompletely (~90%) amorphized kaolinite phases, which were examined by X-ray diffraction, Fourier transform infrared spectroscopy, thermal analysis, scanning electron microscopy, as well as by the determination of the specific surface area and particle-size distribution. To characterize the pozzolanic reactivity, the compressive strength of mortar specimens were studied, in which 10% of ordinary Portland cement was replaced by mechanochemically activated materials.The addition of silica fume or diatomaceous earth reduced significantly the required grinding time and energy of the complete and partial amorphization of kaolinite. The accelerated amorphization of kaolinite can be attributed to the action of amorphous silica or hydrous silica grains as grinding bodies. The effect of these amorphous silica grains on the mechanochemical amorphization of kaolinite was found practically the same as that of the crystalline quartz grains. The partial substitution of ordinary Portland cement by the mechanochemically activated materials increased the compressive strength of the mortar specimens due to the higher pozzolanic reactivity caused by the enlarged reactive silica and alumina content. The resulting strength data also demonstrated that the incomplete (~90%) amorphization of co-ground kaolinite, as compared to the complete amorphization, is more favorable to efficiently produce pozzolanic cement substitute materials with a high reactivity due to the high amount of amorphous kaolinite and the relatively weak interaction of particles.

Mineralogical and Geochemical Characteristics of Banded Agates from Placer Deposits: Implications for Agate Genesis.

The phase composition and geochemical characteristics in banded agates with different structural sequences have been investigated in detail. The results reveal that the agate bands have a combination of a pseudo-granular silica → fibrous chalcedony → crystalline quartz (type I) sequence and a newly discovered pseudo-granular silica → crystalline quartz (type II) sequence. The banded agates mainly consist of α-quartz, moganite, and a minor amount of amorphous silica, goethite, hematite, kaolinite, illite, and carbonates. With the evolution of two structural sequences, the content of α-quartz and moganite increases and decreases, respectively. There is no moganite in crystalline quartz. The increased concentration of trace elements like Li, Na, Al, K, Ca, Ti, Mn, and Fe in different bands may correspond to the decrease in the water content in the mineral-forming fluid. The increased trace elements promote the structural transformation process of silica. With the evolution of the type I sequence, the thermal gradients between adjacent bands are 17 and 51 °C, respectively. In contrast, a significantly higher thermal gradient of 53–66 °C is exhibited when pseudo-granular silica transforms directly to crystalline quartz. It is inferred that a slightly increased thermal gradient between adjacent bands promotes the structural transformation process of the type I sequence. The sharply increasing thermal gradient between adjacent bands leads to the formation of the type II sequence from pseudo-granular silica to crystalline quartz. The formation process of different structural sequences in agate may be controlled together by trace element concentrations and thermal gradients.

Comparing α-Quartz-Induced Cytotoxicity and Interleukin-8 Release in Pulmonary Mono- and Co-Cultures Exposed under Submerged and Air-Liquid Interface Conditions.

The occupational exposure to particles such as crystalline quartz and its impact on the respiratory tract have been studied extensively in recent years. For hazard assessment, the development of physiologically more relevant in-vitro models, i.e., air-liquid interface (ALI) cell cultures, has greatly progressed. Within this study, pulmonary culture models employing A549 and differentiated THP-1 cells as mono-and co-cultures were investigated. The different cultures were exposed to α-quartz particles (Min-U-Sil5) with doses ranging from 15 to 66 µg/cm2 under submerged and ALI conditions and cytotoxicity as well as cytokine release were analyzed. No cytotoxicity was observed after ALI exposure. Contrarily, Min-U-Sil5 was cytotoxic at the highest dose in both submerged mono- and co-cultures. A concentration-dependent release of interleukin-8 was shown for both exposure types, which was overall stronger in co-cultures. Our findings showed considerable differences in the toxicological responses between ALI and submerged exposure and between mono- and co-cultures. A substantial influence of the presence or absence of serum in cell culture media was noted as well. Within this study, the submerged culture was revealed to be more sensitive. This shows the importance of considering different culture and exposure models and highlights the relevance of communication between different cell types for toxicological investigations.

Metallogenesis of Ni–Co–Fe-arsenide type mineralization in the Purísima-Rumicruz deposit, Jujuy, Argentina

The Purísima-Rumicruz vein system is a Ni–Co–Fe-arsenide type or Five-Element deposit located in the Cordillera Oriental, northwestern Argentina. The host rocks are Ordovician black shales of the Acoite Formation. Three vein types, were identified (a) sulfides/sulfoarsenides + carbonates ± quartz; (b) barite; and (c) crystalline quartz veins. Sulfide-carbonate veins are narrow and exhibit multi-episode infill and are NW-SE and E-W oriented. Four successive stages of mineral precipitation were established. The first stage, sulfide-rich, comprises galena, pyrite, chalcopyrite, bornite, and Zn-rich tetrahedrite-tennantite. A second stage corresponds to native silver, arsenides, Ni-sulfarsenides and pitchblende, indicative of a rise in the As/S ratio in the hydrothermal fluids. The third stage evidences a decrease in the As/S ratio with sulfide precipitation of silver sulfides, chalcocite, chalcopyrite, tetrahedrite-tennantite, bornite and millerite. Finally, a supergene event with covellite, digenite, limonite and Cu-carbonates occurred. Microthermometric studies of Stage 1 quartz yield Th between 185 and 276 °C and 5.2–12 wt% eq. NaCl. Salinities. Stage 3 calcite yield Th 110-240 °C and salinities in two ranges, 1–11 and 16.8–24 %wt. NaCl eq. The δ34S values in chalcocite and galena range between +5.8 and + 7‰, and the δ18OSMOW values from quartz, are between +6.2 and + 9.0‰. δ18OSMOW and δ13CPDB values in calcite samples range between +10.9 and +14.7‰, and −3.05 to −4.07‰, respectively. Isotope data indicate a cortical source of the fluids, probably from connate waters. Early Cretaceous rifting produced a thermal anomaly and direct faults and fractures. Deep-seated brines mixed with connate fluids of the Acoite Formation led to the formation of the Purísima-Rumicruz veins.

Understanding the Anisotropic Mechanical Behavior of Single‐Crystalline Alpha Quartz From the Insight of Molecular Dynamics

AbstractQuartz is among Earth's most abundant minerals, which has several stable polymorphs in nature. In this study, molecular dynamics simulations are used to investigate the mechanical properties of crystalline alpha quartz. The obtained results specify that tensile stress under uniaxial tension is greater in z (c‐axis) than in other directions (290 vs. 115 GPa and 190 GPa). This outcome confirms that crystalline quartz has an anisotropic behavior under applied load, and as a result, Young's modulus varies in different directions. Furthermore, the effect of existing central cracks with different lengths are considered and the results analyzed. According to the results, central cracks decrease average stress and strain, and this reduction is higher in the z‐direction([0 0 0 1]). Additionally, it was found that the strain rate affects the stress‐strain behavior of the models; however, the strain rate plays a negligible role when the central crack length extends. In terms of potential energy, simulation results indicate that potential energy is the highest in the model without any crack and reduces by growing the central crack size.

Earliest Ediacaran speleothems and their implications for terrestrial life after the Marinoan snowball Earth

Cryogenian snowball Earth glaciations may have had disastrous impacts on the biosphere, particularly the terrestrial ecosystem. However, how the terrestrial ecosystem responded to and recovered from these glaciations remains poorly understood. Speleothems offer important insights into terrestrial life because their formation is critically dependent on soil CO2 derived from microbial respiration. Here we report the wide distribution of miniature paleo-speleothems from the ∼ 635 Ma Doushantuo cap dolostone in South China and assess their implications for the recovery of terrestrial life after the terminal Cryogenian Marinoan glaciation. The ∼ 3-m-thick cap dolostone was deposited during the initial transgression following deglaciation but subsequently experienced subaerial exposure due to post-glacial rebound, which resulted in the development of extensive sheet-cavities in the cap dolostone and a widespread karstic surface atop the cap dolostone. The sheet-cavities were filled with multiple generations of minerals, including isopachous dolomite interpreted to have formed in the phreatic zone, speleothems consisting of fibrous calcite interpreted to have formed in the vadose zone, as well as later phases (i.e., isopachous radial chalcedony, crystalline quartz, and blocky calcite). The Doushantuo speleothems are millimeter-to-centimeter in size and include gravitational speleothems (stalactites and stalagmites) and non-gravitational speleothems (helictites, moonmilk, botryoids, and flat crusts). Some of them were secondarily silicified by hydrothermal fluids before a renewed transgression in which ∼ 632 Ma shales overlying the cap dolostone were deposited. The wide distribution of Doushantuo speleothems and the preservation of microfossils in these speleothems indicate the presence of an active soil-microbial ecosystem in the earliest Ediacaran Period and the rapid recovery of terrestrial life after the Marinoan snowball Earth.

Reusing Construction and Demolition Waste to Prepare Alkali-Activated Cement.

Large amounts of waste are derived not only from construction processes, but also the demolition of existing buildings. Such waste occupies large volumes in landfills, which makes its final disposal difficult and expensive. Reusing this waste type is generally limited to being employed as filler material or recycled aggregate in concrete, which limits its valorisation. The present work proposes reusing construction and demolition waste to manufacture alkali-activated cement to improve its sustainability and recovery. Construction and demolition waste (C&DW) from a demolition waste collection plant in Valencia (Spain) was physically and chemically characterised. This residue contained large fractions of concrete, mortar, bricks, and other ceramic materials. X-ray fluorescence (XRF) analysis showed that its chemical composition was mainly CaO, SiO2 and Al2O3. X-ray diffraction (XRD) analysis revealed that it presented some crystalline products, and quartz (SiO2) and calcite (CaCO3) were the main components. Blends of C&DW and blast furnace slag (BFS) were alkali-activated with mixtures of sodium hydroxide and sodium silicate. The corresponding pastes were characterised by techniques such as thermogravimetry and scanning electron microscopy (SEM). The alkali-activated mortars were prepared, and the resulting mortars’ compressive strength was determined, which was as high as 58 MPa with the 50% C&DW-50% BFS mixture. This work concluded that it is possible to make new sustainable binders by the alkali activation of C&DW-BFS without using Portland cement.

Physical and chemical properties of dust in the Pre-Aral region of Uzbekistan

The aim of this work is study of physical and chemical properties of dust of the Pre-Aral region of Uzbekistan such as Karakalpakstan and Khorezm that are located near the three deserts such as the Aralkum, Karakum, and Kyzylkum. The dust particles fell on glass have been collected in Karakalpakstan and Khorezm and studied systematically by employing wide range of methods. Particle volume vs size distribution has been measured with maximum around 600 nm and ~ 10 µm. The major and minor constituent materials present in the dust have been studied systematically by X-ray fluorescence spectroscopy, energy dispersive X-ray diffraction, and inductively coupled plasma optical emission spectroscopy. Main characteristic absorption bands corresponding to Si–O, Si–O-Si bonding in quartz and Fe–O bonds in hematite Fe2O3 have been identified by infrared and Raman spectroscopy. Quartz, hematite, lime, corundum, magnesia, and several other trace minerals have been identified in the dust particles. X-ray diffraction peaks corresponding to quartz, hematite, and corundum are sharp and are found to be more crystalline with some level of disorder. Analysis of the particle size and crystallinity on human being has been performed: disordered or crystalline quartz can create the lung disease; the particles in the size of 0.5–0.7 µm may produce diseases such as chronic silicosis, silicosis, and silica tuberculosis whereas hematite might create lung disease. Dust particles worsen optical transmittance of glass of the panels.Graphical abstract

Implications of Major and Trace Element Migration in Altered Granites for Hydrothermal Alteration and Granite-Related Uranium Mineralization in the Sanjiu Ore Field, South China

The recently discovered Sanjiu ore field (SJOF) is a granite-related uranium ore field located in the middle of Zhuguangshan (South China). The relationship between hydrothermal alteration of granite and uranium mineralization in the SJOF is crucial yet understudied. In this study, the major- and trace-element contents of granite samples (fresh granite, altered granite, and tectonites) with different uranium contents were analyzed by using X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma–mass spectrometry (ICP–MS). The analytical results show a relative increase in Si, S, Ca, Pb, Mo, and Sb content in altered granites and tectonites, relative to fresh granites. During the mineralization stage, the increase of the aforementioned elements is related to various hydrothermal alterations (e.g., silicification, carbonation, sulfation, etc.) and newly formed minerals (e.g., microfine crystalline quartz veins; calcite agglomerates or fine veins; and metal sulfides, such as pyrite). There is a concomitant relative decrease in Na, K, Al, Fe, Mg, and other elemental contents that may be due to mineralogical alteration processes, such as biotite to chlorite, feldspar-group minerals to clay minerals, and redox of Fe-bearing minerals. The LREE/HREE ratio in altered granites decreases significantly with the increase in uranium content, suggesting that a low LREE/HREE ratio may be a prospecting indicator. The normalized trace-element patterns of mineralized granite (ore) and the relatively high U content of fresh granite imply that granitic rocks may be the primary uranium source in the SJOF. The uranium mineralization is mainly concentrated in the redox zone that occurs at a depth of 100−300 m. The redox zone is characterized by the most developed hydrothermal alterations and enrichment of trace elements, including W, Mo, Sb, Li, and the HREE.

Aeolian driven oxidant and hydrogen generation in Martian regolith: The role of mineralogy and abrasion temperature

The surface of Mars is a dynamic, cold environment where aeolian abrasion leads to the fracturing of silicate minerals which can produce oxidants upon exposure to water. Here we report results of a series of laboratory experiments where the abrasion of sand sized (125 – 300 μm) quartz, labradorite, forsterite and opal were conducted under a simulated Martian atmosphere at a range of temperatures common to Mars' surface (193 to 273 K). Our results suggest that abrasion rates are controlled by temperature; an observation that may have potential for providing insight into Martian paleo-temperatures. On the addition of water, detectable H2O2 was generated in all abraded experiments with crystalline quartz, labradorite and forsterite, but not amorphous opal – supporting previous inferences that mineral crystal structure plays a role in oxidant production. Dissolved Fe concentrations also indicated a strong additional control on net H2O2 production by Fenton reactions. Detectable H2 was similarly measured in abraded experiments with crystalline minerals and not for amorphous opal. Labradorite and forsterite generated minimal H2 and only in more abraded samples, likely due to the reaction of Si• with water. In quartz experiments H2 was only present in samples where a black magnetic trace mineral was also present, and where H2O2 concentrations had been reduced to close to detection. In the quartz samples we infer a mechanism of H2 generation via the previously proposed model of spinel-surface-promoted-electron transfer to water. The presence of H2O2 may exert an additional control on net H2 production rates either directly (via reaction of H2 with OH• and H2O2) or indirectly (by the oxidation of H2 generating sites on mineral surfaces). Overall, our data supports previous inferences that aeolian abrasion can produce additional oxidants within the Martian regolith that can increase the degradation of organic molecules. We further suggest that the apparent control of H2O2 concentrations on net H2 generation in our experiments may help explain some previous apparently contradictory evidence for mineral-water H2 generation at low temperatures.

Dielectric Properties of Steatite Ceramics Produced from Talc and Kaolin Wastes

The main objective of this work was to study the use of kaolin processing wastes in the production of steatite ceramics, emphasizing mechanical strength and dielectric properties. Steatite ceramics were prepared using mixtures of talc with fine and coarse particle kaolin wastes (7.5, 10 and 12.5 wt.%) sintered at different temperatures (1200, 1250 and 1300°C). After sintering, the specimens were submitted to mineralogical and microstructural characterization. Linear shrinkage, apparent porosity, flexural strength and dielectric properties were also evaluated. Results showed the formation of the crystalline phases protoenstatite and quartz for all produced ceramics. The results verified for porosity, mechanical strength and dielectric properties proved to be suitable for the application of this material in electrical insulation.

Standoff Detection of Oil and Powder Mixtures at 12 Meters Using a Tunable Quantum Cascade Laser-Based System with a Close Focus Telescope and Uncooled Infrared Detector

We have designed and demonstrated a quantum cascade laser (QCL) based standoff system that utilizes an uncooled mercury cadmium telluride (MCT) detector with lock-in signal processing for chemical identification at a distance of 12.5meters in indoor ambient light conditions. In the system, a tunable quad-QCL operating (1MHz) in quasi-continuous wave mode between 8.45 and 10.03μm (∼1182 to 1000 cm-1) serves as the active mid-infrared source for remotely interrogating mineral, powder, and thin film oil samples including powder mixtures (6, 12.5, 25, and 50%) of crystalline quartz (SiO2) in KBr. Light as reflected from a given sample is collected using a 10-inch (25.4cm) Dall Kirkham telescope and coupled with ZnSe optics to an uncooled MCT detector. The mixture dependence of the highly transparent KBr and strongly absorbing quartz was found to fit a modified version of the Schatz reflectance model for compacted powder mixtures. All reflectance spectra reported are relative to an Au-coated diffuse reflector. A NIST traceable polystyrene standard reflector was also used to determine the QCL wavelength tuning range and calibration.

Understanding the slag transformation behaviors during entrained‐flow gasification based on comparative analysis of slag properties

AbstractIn this work, four slag samples were collected from the OMB CWS gasification, and the mineral behavior and morphology were studied to explore the formation mechanism of blockage slag. Results showed that amorphous phase is dominant in all slag samples, which was mainly glassy substances rich in low‐temperature eutectic of iron. The precipitation of metallic iron and the crystals of SiC, calcite, and quartz were found in slags which were taken from the bottom of the combustion chamber (S‐b). The quench slag collected from stable operation conditions (S‐s) had a low content of quartz crystalline. While slag from the down pipe of the quench chamber (S‐b) and bulk slag from the water‐cooled pool (S‐p) had observed the precipitation of crystals. Comparing to S‐s, carbon matters in S‐b had a higher order degree of carbon structure. By comparing the slag sample obtained during stable operation (S‐s) with slag blocking occurs (S‐b, S‐d, S‐p), it is found that the blockage of the OMB CWS gasifier was strongly related to unreacted residual carbon and the high content of sodium and iron in coal. They will interact with each other and form small number of crystals and most of the amorphous material.

Aeolian driven silicate comminution unlikely to be responsible for the rapid loss of martian methane

Seasonally varying levels of methane have been measured at parts per billion by volume levels in the lower Martian atmosphere. The source of this methane is not understood, but equally intriguing is its rapid loss, which is higher than the current chemical or photochemical decomposition models suggest. This implies an unknown but efficient sink mechanism. Earlier investigations reported the formation of Si• during the comminution of borosilicate glass and quartz that permitted the uptake of methane. This led to the speculation that an analogous aeolian driven comminution of Si-rich minerals on Mars could similarly sequestrate atmospheric methane. However, borosilicate glass is an artificial material and crystalline quartz is not common on the surface of Mars. To investigate whether this mechanism could take place on materials that were more representative of those on Mars, we comminuted a set of Mars analogue silicate rocks/minerals (basalt, obsidian, feldspar, pyroxene, zeolite, opal) in the presence of 13C-labeled methane. Solid-state Nuclear Magnetic Resonance (NMR) analysis of borosilicate glass and quartz indicated silicon carbide bond formation and this observation was supported by attenuated total reflectance-Fourier transform infra-red spectroscopy and X-ray photoelectron spectroscopy. However, silicon carbide bonds and methane sequestration were not detected in our set of Mars analogue samples. We hypothesise that electron donation by redox-active elements within the analogue materials, such as Fe, may have suppressed Si-methyl bond formation during comminution. Aeolian driven Si radical formation appears unlikely to be responsible for the rapid loss of methane in the Martian atmosphere, and thus the methane sink mechanism(s) require further investigation.