Standard Quartz Research Articles

Are quick equivalent doses realistic? Testing range-finder luminescence dating for water-lain and postglacial flooding sediments in NE Poland

Raw sediment samples which are without prior lengthy laboratory preparation can be used to obtain a rough but rapid estimate of the luminescence equivalent dose, and thus of the relative age of the sediment. In this study, we tested this range-finder method on clastic sediments in NE Poland for the first time, with special focus on Pleistocene meltwater sediments generated by highly energetic glacial lake outburst floods, and the post-flooding sediments. Two datasets with known doses from standard measurements were compared to range-finder doses determined from quartz and feldspar in untreated sediments. We found statistically significant correlation between equivalent doses of (1) standard quartz optically stimulated luminescence (OSL) and range-finder feldspar infrared stimulated luminescence (IRSL) at 50 ºC, and (2) standard quartz OSL and range-finder quartz OSL in low-dose samples (<80 Gy). However, these correlations should only be considered as approximate whereby preparing more than three range-finder aliquots has the potential of yielding more accurate results. Correlation between the range-finder quartz OSL and range-finder feldspar IRSL is also significant. The rangefinder measurements can be used for approximate dose determination to preliminary assess the sediment age or as a selection tool to avoid incompletely bleached samples. The sedimentary environment and especially sediment reworking and transportation seem to influence these correlations. We consider the sediments studied here to have undergone between one and four reworking stages, and samples with repeated reworking usually represent well-bleached material for luminescence dating.

Recycling of magnesium oxychloride cement: Application of crushed MOC waste as a filler in the next-generation MOC composites

This study deals with magnesium oxychloride- (MOC-) based construction composites in which, a filler formed from end-of-life MOC-based composite recyclate is used as a partial or full replacement of standard quartz sand filler. The developed composites pose as a highly environmentally sustainable alternative to Portland cement (PC), which has dominated the global construction sector, largely due to its unique properties and adaptability to various conditions. As the PC industry is a major contributor to greenhouse gas emissions, it is ultimately necessary to find a suitable alternative. In our study, we demonstrated that the proposed composite, even with a very high content of the MOC-based recyclate performs well concerning its mechanical parameters evidenced by compressive strength exceeding 64 MPa. The developed composites also yield a low water absorption of about 3.3 wt% and even when exposed to the harsh environment of 95 % RH for 7 days, their softening coefficient reaches values higher than 85 %. The acquired material parameters of the prepared composites make them suitable for application in the production of construction materials with high mechanical strength and acceptable resistance to the action of moisture. The approach which was taken, where MOC-based construction waste can be fully reutilized in the next generation of MOC composites as a filler represents a very promising route for the development of waste-free and CO2-neutral technology.

Disturbance-immune, fast response LITES gas sensor based on out-plane vibration mode employing micro Fabry-Perot cavity with heterodyne phase demodulation

The disturbance-immune, fast response light-induced thermoelastic spectroscopy (LITES) gas sensor based on out-plane vibration (OPV) mode employing micro Fabry-Perot cavity with heterodyne phase demodulation was firstly reported in this paper. Compared to the traditional in-plane vibration (IPV) mode, the OPV mode has a lower resonance frequency (f0) to enhance the energy accumulation time of the system. The OPV mode based H-LITES (OPV-H-LITES) sensor and the IPV mode based H-LITES (IPV-H-LITES) sensor were established using a standard quartz tuning fork (QTF) at the same conditions for performance comparison. Acetylene (C2H2) was selected as the target gas to verify the sensor performance. In comparison to the IPV-H-LITES sensor, there has been a 3.5-fold improvement in signal-to-noise ratio (SNR) of OPV-H-LITES sensor. In order to further improve the sensor performance, a novel self-designed low-frequency QTF was adopted to replace the standard QTF, leading to a 2.3-fold increase in the SNR of the OPV-H-LITES sensor. Finally, a minimum detection limit (MDL) of 7.22 ppm for C2H2 detection was obtained. The proposed technique holds the merits of high sensitivity, power disturbance resistance, wavelength independence, excellent linear concentration response and long-term stability.

Testing the accuracy of single-grain OSL dating on Eemian quartz samples

Single-grain OSL dating of quartz is a popular approach to OSL dating, even when incomplete bleaching is not likely to be significant. However, little testing of the accuracy of single-grain dating has been published; particularly for samples older than 50 ka. In this study, we investigate the accuracy of single-grain quartz OSL dating, when a significant number of individual grains are no longer able to accurately measure the burial dose because of saturation effects. We compare standard multi-grain OSL results with those obtained from single-grain OSL measurements for five OIS substage 5e (Eemian) samples (∼128 ka). We show that for these samples, standard multi-grain quartz dose estimation results in dose estimates in good agreement with the predicted doses (four of the five samples recover age control), but that standard frequentist single-grain dating procedures significantly underestimate the age controls, i.e. the measured to predicted dose range between 0.42 ± 0.03 and 0.84 ± 0.06, where the underestimation increases with increasing relative number of grains in saturation. Attempting to remove the inevitable bias in the dose estimation resulting from a significant number of saturated grains (by using the Dc criterion) reduced the underestimation, i.e. the measured to predicted dose ratio range between 0.63 ± 0.05 and 0.94 ± 0.08, but only the sample with the smallest absorbed dose is consistent with the age control. Using Bayesian analysis (“BayLum”) the ratio of measured to predicted dose range between 0.75 ± 0.07 and 1.14 ± 0.08, but only two of the five samples agree with the independent age control. Our results have implications for the evaluation of single-grain OSL dating of quartz in the 100–200 Gy natural dose range.

High power illumination system for uniform, isotropic and real time controlled irradiance in photoactivated processes research

In the study of photocatalytic and photoactivated processes and devices a tight control on the illumination conditions is mandatory. The practical challenges in the determination of the necessary photonic quantities pose serious difficulties in the characterization of catalytic performance and reactor designs and configurations, compromising an effective comparison between different experiments.To overcome these limitations, we have designed and constructed a new illumination system based in the concept of the integrating sphere (IS). The system provides uniform and isotropic illumination on the sample, either in batch or continuous flow modes, being these characteristics independent of the sample geometry. It allows direct, non-contact and real time determination of the photonic quantities as well as versatile control on the irradiance values and its spectral characteristics. It can be also scaled up to admit samples of different sizes without affecting its operational behaviour.The performance of the IS system has been determined in comparison with a second illumination system, mounted on an optical bench, that provides quasi-parallel beam (QPB) nearly uniform illumination in tightly controlled conditions. System performance is studied using three sample geometries: a standard quartz cuvette, a thin straight tube and a microreactor by means of potassium ferrioxalate actinometry. Results indicate that the illumination geometry and the angular distribution of the incoming light greatly affect the absorption at the sample. The sample light absorption efficiency can be obtained with statistical uncertainties of about 3% and in very good agreement with theoretical estimations.

The development of laboratory‐based high energy sources for XPS

Over the last fifty years, a number of higher energy X‐ray sources have been suggested as alternatives for the usual AlKα source found in the first commercial XPS systems and still the standard anode material for XPS today. This paper reviews the development of a number of such sources, predominantly in the authors' laboratory, and the rationale behind the desire to extend the binding energy range of the technique. The achromatic sources SiKα, ZrLα and TiKα are described along with monochromatic sources AgLα and CrKβ, both based on the standard quartz monochromator geometry but taking higher orders of diffraction. The driving force for much of this development was the desire to probe deeper core levels and CCC Auger transitions. These could be combined into initial or final state Auger parameters as described in much of the work cited in this review. The highest energy source considered is the CuKα source based around an external X‐ray tube, which provides much insight into the electronic structure of steels by measurement of the Fe1s and FeKLL peaks. The last decade or so has seen a significant increase of interest in HAXPES, and all manufacturers of turn‐key XPS instruments offer HAXPES options of one form or another, there are three dedicated HAXPES systems commercially available, which are very briefly described.

Seepage deformation characteristic of gap-graded coral sand in the South China Sea

Foundation settlement and collapse disasters resulting from seepage deformation in hydraulic-filled islands and reefs have been observed in the South China Sea, but the underlying failure mechanism and characteristic remain unclear. This study aims to investigate the influence of compactness and fine particle content on the seepage deformation of gap-graded coral sand and revel the characteristics and mechanism of seepage deformation of gap-graded coral sand through laboratory seepage deformation tests. The results indicate that the seepage deformation failure mode of gap-graded coral sand is influenced by the content of fine particles which undergo an evolution process from continuous piping to discontinuous piping to boiling. Particle loss is affected by the constraints between coarse particles, and the ability of different particle contact forms to restrict the loss of fine particles is different. Moreover, irregular particle morphology increases intergranular constraints, enhancing the coral sand's resistance to seepage deformation compared to standard quartz sand. Based on these findings, the instability coefficient was used to consider the influence of particle morphology and inter-particle contact on the seepage deformation. A hydraulic criterion for the internal stability of coral sand was established, demonstrating its versatility. Furthermore, the applicability of existing geometric criteria in evaluating coral sand was analyzed. The existing methods were found to be inaccurate in evaluating the internal stability of coral sand specimens with a fine particle content below 20 %.

MOC Composites for Construction: Improvement in Water Resistance by Addition of Nanodopants and Polyphenol.

The topic of modification of magnesium oxychloride cement (MOC) using specific functional additives is very much pronounced in the research of alternative building materials. This study deals with the co-doping of MOC by 1D and 2D carbon nanomaterials in order to improve its mechanical properties while using tannic acid (TA) as a surfactant. Furthermore, the effect of TA on MOC also improves its water resistance. As a filler, three size fractions of standard quartz sand are used. The proposed types of MOC-based composites show promising results considering their mechanical, macro- and microstructural, chemical, and hygric properties. The use of 1D and 2D nanoadditives and their mixture enables the improvement in the flexural strength and particularly the softening coefficient, which is the durability parameter characterizing the resistance of the prepared materials to water. After immersion in water for 24 h, the compressive strength of all tested specimens of modified composites was higher than that of the reference composite. Quantitatively, the developed co-doped composites show mechanical parameters comparable to or even better than those of commonly used Portland cement-based materials while maintaining high environmental efficiency. This indicates their potential use as an environmentally friendly alternative to Portland cement-based products.

Natural thermometers in concrete: Stability and reliability verification of inclusion decrepitation thermoacoustic thermometry

The fire-exposure temperature of concrete directly determines the degree of damage to its microstructure and the performance of concrete. Therefore, an accurate assessment of the fire-exposure temperature of concrete is crucial. But to date, there is not yet an accurate, practical, and effective method for measuring the internal temperature of concrete after fire. Based on the discovery that fluid inclusions in concrete act as natural thermometers, this paper investigates the scientific principles and experimental evidence of the decrepitation thermometry of inclusions. By extracting quartz sand samples from the interiors of concrete members after a fire and performing an inclusion decrepitation test on these samples, the maximum fire-exposure temperature of concrete can be determined with a high degree of accuracy. The test results reveal that the natural sand used in construction typically contains fluid inclusions, indicating that the necessary conditions for inclusion decrepitation thermometry are satisfied for concrete structures. In this study, standard quartz sand samples were configured, and inclusion decrepitation temperature measurements were conducted after subjecting the samples to different heating rates, cooling methods, thermostatic durations, and standing times after fire. The test results indicate that the impact of the aforementioned factors on the inclusion decrepitation temperature measurement is not evident. The maximum relative error between all temperature measurement results and the actual heating temperature is <10 %, and the average relative error is <2.5 %. The experimental results show that fluid inclusions are natural thermometers in concrete. After a fire, the maximum temperature experienced in the concrete can be quantitatively assessed using the initial decrepitation temperature of the inclusion. This method possesses the advantages of being a scientific test method and providing accurate temperature measurements without any indirect analysis or calculation using simple test equipment, sample preparation, and operation.

Utilization of waste carbon spheres in magnesium oxychloride cement

The Portland cement (PC) industry is a big producer of CO2 – a major contributor to the global warming. As the world tends to reduce the CO2 emissions because of its negative effect, a sustainable and efficient PC alternative is needed to be found. One of the most promising substitute is based on reactive magnesia – magnesium oxychloride cement (MOC). This paper deals with the design, development, and characterization of environmentally friendly composites based on MOC. In addition to the standard quartz sand filler, carbon spheres-based waste produced by polypropylene treatment via plasma gasification was used as a nanoadditive. Before the preparation of the composites themselves, the carbon spheres (CS) were analysed with a wide range of analytical methods in order to determine their microstructure and composition. The CS were used in the amount of 0.5, 1.0, and 3.0 wt% related to the weight of the pure MOC paste. The prepared composite samples were tested for their microstructure, phase and chemical composition, micro- and macrostructural parameters, and mechanical properties after 28 days of maturing. Furthermore, the influence of CS on the hygric properties and the water resistance of the MOC-based composites were studied after 24 h-long immersion in water. It has been shown, that with the increasing amount of CS, the mechanical parameters improve quite rapidly, making CS an enhancing eco-friendly nanoadditive. It was also shown, that CS helps to slow down water transport in MOC-based composites, which is a key aspect in the improvement of their water resistance and overall durability after exposure to humidity. The incorporation of carbon spheres-based waste as a nanoadditive in MOC-based composites shows promising improvements in mechanical properties and water resistance, contributing to the development of environmentally friendly construction materials.

Измерения спектральной зависимости коэффициента отражения комплектного алюминиевого зеркала спектрофотометра Shimadzu UV-2700

In this paper, we present the results of experimental investigation of the spectral dependence of the aluminum mirror reflection coefficient in the operating range of 185…900 nm. The aluminum mirror is a part of the Specular Reflectance Measurement Attachment to the Shimadzu UV-2700 spectrophotometer. We used experimental data obtained on the same spectro-photometer for a standard incidence angle of 5° for the reflection coefficient of a fused silicon dioxide plate as a reference sample. This is because the spectral characteristics of the optical parameters of fused silicon dioxide determined by the Sellmeier formular are well known. We used a standard quartz glass plate with a thickness of 2,2 mm and a spectrophotometer slit of 5 nm in our experiment. In this case it is possible to neglect interference effects due to multiple reflection. We found from our experimental data the spectrum of the absorption coefficient required for determining the calculated spectral dependence of its reflection coefficient in the spectrophotometer operating range. On the basis of this absorption spectrum the absolute values of the reflection coefficient of the quartz plate were calculated. This calculation was made for the normal incidence approximation and taking into account multiple reflections and dispersion of the refractive coefficient of fused quartz in accordance with the Sellmeier formula. The comparison of the spectra of calculated absolute and relative values of the reflection coefficient of the quartz plate measured on a spectrophotometer with experimental data for the reflectance of aluminum mirror made it possible to obtain the spectral dependence for the aluminum mirror for the entire operating range from 185 to 900 nm. It was found that spectral dependence of the reflection coefficient of a complete aluminum mirror was nonmonotonic. In case under consideration the deviations of its reflection coefficient from an ideal unit value do not exceed 10 % only in the spectral range from 350 to 670 nm. Thus, it is necessary to take into account the obtained spectral dependence of the reflection coefficient of the complete aluminum mirror for quantitative measurements in the entire operative range of the Shimadzu UV-2700 spectrophotometer from 185 to 900 nm.

Iron aluminides – A step towards sustainable high-temperature wear resistant materials

Iron aluminides are promising candidates for high-temperature corrosion- and wear resistant materials. Their intermetallic nature provides good mechanical stability at comparatively low density in contrast to commonly used iron- and nickel-based wear resistant alloys such as white cast irons or Inconel alloys. The objective of this study is to measure the influence of different alloy compositions on the high-temperature abrasion resistance of iron aluminides. Alloys of 25–30 wt% Al, Ti, B and Si were characterized and compared to a high-temperature resistant white cast iron.Microstructural analysis via scanning electron microscopy as well as electron backscatter diffraction were performed to elucidate the materials’ microstructures and the different phases present. Hot hardness up to 700 °C and nanoindentation were determined to quantify differences in mechanical properties between compositions. Wear resistance was quantified with high-temperature abrasion tests performed in a modified ASTM G65 test at 20, 500 and 700 °C, with standard quartz sand as abrasive and a high-temperature resistant steel wheel as counterbody. Wear results point out a significantly better behaviour of the iron aluminides at 500 °C and 700 °C at a quarter of the wear rates of the white cast iron, which can be attributed to beneficial mechanical properties enabling the formation of protective mechanically mixed layer under incorporation of abrasives.Finally, a life cycle assessment (LCA) was performed to assess the environmental impact of the iron aluminides compared to the steel reference during production, accounting for the lifetime as indicated by the wear rates obtained. Results show significantly reduced environmental impacts in the evaluated impact categories, making iron aluminides promising candidates for future high-temperature wear components.

An NMR-assisted laboratory investigation of coal fines migration in fracture proppants during single-phase water production

Proppants are injected with the fracturing fluid to keep the hydraulic fractures open. However, deposition of coal fines in the void spaces between proppants significantly damage flow conductivity of the fractures. In this study, we experimentally model coal fines migration in a proppant pack. Standard quartz sand (16–20 mesh) is used to prepare the proppant pack. The proppant pack is installed within a low-field Nuclear Magnetic Resonance (NMR) facility to record NMR response before and after the experiment of fines suspension injection. The injected suspension consists of water with 500 ppm concentration of coal fines of radius from 2.8 to 142.9 µm. Coal fines are generated by crushing an anthracite coal sample. The permeability is damaged significantly by about 41% after 80 pore volume injection. NMR response suggests that volume of the large-size pores (radius rp > 60 um) decreases while that of the medium-size pores (0.9 um <rp < 60 um) increases. The pore structure change is caused by two possible mechanisms: (a) reducing pore size by fines occupying pore space and (b) developing inter-particulate pore space of fines gathering at the damaged pores. Although the fines size (radius from 2.8 to 142.9 um) is significantly smaller than the pore size (<1005.2 um), the large-size pores can still be damaged by the fines. The results of this study can help to understand mechanisms of fines migration and conductivity evolution in/of the hydraulic fractures during Coal Seam Gas production.

Biased quartz crystal microbalance method for studies of chemical vapor deposition surface chemistry induced by plasma electrons.

A recently presented chemical vapor deposition (CVD) method involves using plasma electrons as reducing agents for deposition of metals. The plasma electrons are attracted to the substrate surface by a positive substrate bias. Here, we present how a standard quartz crystal microbalance (QCM) system can be modified to allow applying a DC bias to the QCM sensor to attract plasma electrons to it and thereby also enable in situ growth monitoring during the electron-assisted CVD method. We show initial results from mass gain evolution over time during deposition of iron films using the biased QCM and how the biased QCM can be used for process development and provide insight into the surface chemistry by time-resolving the CVD method. Post-deposition analyses of the QCM crystals by cross-section electron microscopy and high-resolution x-ray photoelectron spectroscopy show that the QCM crystals are coated by an iron-containing film and thus function as substrates in the CVD process. A comparison of the areal mass density given by the QCM crystal and the areal mass density from elastic recoil detection analysis and Rutherford backscattering spectrometry was done to verify the function of the QCM setup. Time-resolved CVD experiments show that this biased QCM method holds great promise as one of the tools for understanding the surface chemistry of the newly developed CVD method.

The removal of total suspended particulates (TSP) using chitosan/PVA electrospun fibers

Total suspended particle (TSP) is the measurement of the amount of suspended particle with a diameter less than 100 micrometers. The exposure of particulate matter can be significant for human health and environment. It can cause respiratory and cardiovascular effects, reduce visibility, and reduce water quality. Electrospun fibers is a versatile technology that can produce large surface area, controllable fiber diameter and interconnected pore structure. In this study, the effectiveness of chitosan-polyvinyl alcohol (CS-PVA) fibers incorporated with activated carbon (AC) for capturing TSP in the air was investigated. The CS-PVA fibers was prepared by combining CS and PVA solutions at ratio of 30:70 with various AC concentrations ranging from 0-3 wt.%. The CS-PVA fibers prepared were fitted in the low-volume air samplers (LVAS) and placed nearby the main road of UMK Campus Jeli, for the collection of PM2.5 and PM10. Additionally, the weathering data during the sampling days was requested from My MET website to observe the influence of weather on TSP collection. Based on the results, as the AC concentration increased in the CS-PVA fibers, the concentration of PM10 and PM2.5 also increased. The CSPVA-3 showed the highest collection of PM10 and PM2.5 compared to other CS-PVA fibers and standard quartz filter. However, the collection of TSP on the filter paper were also influence by the humidity, rainfall, and wind speed of the sampling day.

Rock surface and sand-sized sediment quartz dating using optically stimulated luminescence of a Middle-to-Upper Palaeolithic sequence at the Bordes-Fitte rock shelter (Les Roches d’Abilly, Central France)

In this study, we use optically stimulated luminescence (OSL) to establish a robust absolute chronology for the lower part of the stratigraphic record at “Les Roches d’Abilly”, an important Palaeolithic site in Central France. There, lithic assemblages recording the Middle-to-Upper Palaeolithic transition and the behaviour of Neanderthal and Anatomically Modern Human populations are preserved. At the Bordes-Fitte rock shelter, part of “Les Roches d’Abilly”, the archaeo-stratigraphic record has been sealed and preserved by the collapse of the shelter roof and this site has provided important data on the timing of human occupations and Middle-to-Upper Palaeolithic transition in this region. Here, we first obtain burial ages using standard multi-grain quartz techniques on sand-sized sediment grains and then investigate the information available in blue-stimulated luminescence-depth profiles into the surfaces of four quartz-rich cobbles found in the sedimentary record below the various collapses of the shelter roof. These profiles show qualitative evidence for past daylight exposure and a single burial event, allowing the data to be analysed quantitatively using a multiple-event mathematical model. Based on the results of this modelling, it is concluded that at least part of the cobble surfaces were well-bleached at burial and thus that estimated rock surface burial ages are unlikely to be significantly affected by incomplete bleaching. However, it appears that not all cobble surfaces were well-bleached, demonstrating the importance of only using surface doses derived from those cobble layers that can be shown to have been well-bleached at burial. The rock-surface burial ages of the most recent burial event are consistent with the quartz OSL ages derived from the surrounding sediments, giving burial ages of ∼ 50 ka. The OSL ages are consistent with previously published 14 C age control, although a single 14 C age (uncalibrated age of 41 , 900 ± 1 , 500 yr BP) of a lower unit may underestimate the OSL ages. This study provides a reliable absolute OSL chronology for the Bordes-Fitte rock shelter constraining the Middle-to-Upper Palaeolithic transition to occur between 44±2 ka and 48±3 ka ago (at the 68% confidence level).

Tailoring thermal expansion of mechanically interlocked carbon fiber composite reinforced metal

AbstractA method of controlling the thermal expansion of lightweight metals through the insightful incorporation of unidirectional carbon fiber reinforced polymer (CFRP) is demonstrated. The local and directional coefficients of linear thermal expansion (CLTE) of a carbon fiber composite reinforced aluminum (CFRP/Al) specimen can be controlled by tailoring the CFRP volume fraction and CFRP layup orientation, with a 36% reduction in CLTE achieved as compared to the baseline 7075 aluminum at a CFRP volume fraction of 0.26. When a unidirectional CFRP reinforcement is considered, the CLTE as predicted by the modulus modified rule of mixtures is within 1.3% of experimentally obtained values for CFRP volume fractions of 0.10, 0.16, and 0.26. Thermal digital image correlation (T‐DIC) was performed to obtain local and directional CLTE values for the anisotropic CFRP/Al specimens which indicated CLTE is heterogeneous across the specimen length and width, which is otherwise undetected using standard quartz rod dilatometry to measure the CLTE of the macroscopic sample. Evidence for a minimum critical CFRP reinforcement length is also considered based upon the local thermal strain data collected by T‐DIC. Using the mixed material approach presented here, it is possible to minimize or eliminate the thermal expansion mismatch effects that occur in mixed material structures, such as an automotive body structure (i.e., body in white).

All-optical light-induced thermoacoustic spectroscopy for remote and non-contact gas sensing

All-optical light-induced thermoacoustic spectroscopy (AO-LITS) is reported for the first time for highly sensitive and selective gas sensing, in which a commercial standard quartz tuning fork (QTF) is employed as a photothermal detector. The vibration of the QTF was measured by the highly sensitive fiber-optic Fabry-Pérot (FP) interferometry (FPI) technique, instead of the piezoelectric detection in the conventional LITS. To improve the stability of the sensor system, a compact QTF-based fiber-optic FPI module is fabricated by 3D printing technique and a dual-wavelength demodulation method with the ellipse-fitting differential-cross-multiplication algorithm (DW-EF-DCM) is exploited for the FPI measurement. The all-optical detection scheme has the advantages of remote detection and immunity to electromagnetic interference. A minimum detection limit (MDL) of 422 ppb was achieved for hydrogen sulfide (H2S), which was ~ 3 times lower than a conventional electrical LITS sensor system. The AO-LITS can provide a promising approach for remote and non-contact gas sensing in the whole infrared spectral region.

Transformation of mine tailings into cement-bound aggregates for use in concrete by granulation in a high intensity mixer

Mine tailings pose one of the world's largest volumes of challenging residues. To overcome the environmental liability and reduce monitoring and reclamation costs associated with the long-term storage of tailings – and to add extra income to the miners' activities – sustainable solutions and new applications for such residues seem prudent. The aggregate market may be able to absorb significant volumes of tailings. Due to the fineness of tailings, however, a granulation process is required. The tailings studied in the present work originated from the flotation process of a non-ferrous multi-metal mine and were mostly composed of limestone and quartz. The granulation process with a cement binder in a high intensity mixer was studied in detail in this paper. An optimization of the mixing parameters resulted in granules with a single granule crushing strength of 3.1 MPa when using only 5 wt% of CEM III/B as binder (95 wt% of tailings). The optimal granules were tested in mortars by partially replacing standard quartz sand (17 and 32 wt%). Compressive strength after 28 days of 44 MPa was obtained and the leaching of heavy metals was suppressed by using CEM III/B as cement binder.

Development of the spectrum transmittance measurement system for large-size optical elements of Cherenkov telescope

The Cherenkov and fluorescence telescopes are used to detect cosmic rays in many large-scale experiments. Certain large-size optical elements, such as quartz glasses with window and filters, are installed in front of cameras as the window to seal the cameras and minimize the impact of the night sky background light. The transmittance of those optical elements in Cherenkov and fluorescence telescopes is therefore vital for the measurement of the number of photons reaching the camera. The uniformity is an important parameter of transmittance at different wavelength over the whole window surface. It is difficult to ensure the uniformity of the window material when it is produced, especially for the size as large as 1 m2. The measurement of the uniformity of the transmittance of filters at different positions on the window, and over a large optical spectrum, is not a trivial task and therefore a dedicated system has been developed. The large-size filter transmittance measurement system can measure the spectrum range from 250 nm to 900 nm. A two dimensional motorized device is used to carry the system and the accuracy of the system is up to 0.01 mm. In addition, the measuring system can measure the transmittance at an incident angle ranging from 0° to 44°. The relative standard deviation can be reduced to less than 1% by alternately measuring with and without samples. The transmittance spectra of the neodymium glass standard sheets and quartz glass JGS2, of size 876 mm × 862 mm × 4 mm have been measured with this system and compared. The result of neodymium glass indicates that the system can measure the transmittance spectrum precisely, up to 1% uncertainty. The results of the JGS2 quartz glass demonstrate that our system is capable of measuring the optical parameters of very large sample with a precision at the level of 1% over a wide spectrum range.