Impurity Layer Research Articles

Significant enhancment of the accuracy of impurity determination in vacuums using classification one-point laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a highly promising technique for the in-situ, real-time diagnosis of impurity deposits on the inner walls of tokamak devices. The deposited impurity on plasma-facing materials (PFCs) pose a significant risk to the steady-state operation of the tokamak. Under vacuum conditions, an accurate quantitative analysis of the thin co-deposition layers is a technical challenge. In this study, 30 co-deposited layer samples of tungsten (10.0–92.3 a.t.%), molybdenum (2.0–77.8 a.t.%), iron (2.9–12.1 a.t.%) and copper (1.2–18.7 a.t.%) were prepared to simulate the co-deposition layers found on PFCs in Experimental Advanced Superconducting Tokamak (EAST). A variation of the CF-LIBS algorithm, the so-called One Point Calibrated LIBS (OPC-LIBS), was employed to analyze these co-deposited layer samples under conditions of 5 × 10−5 mbar. It was found that the matrix matching degree among the measured samples and the selection of standard samples play a decisive role in the quantitative analysis capability of OPC-LIBS. In actual situations, the composition of the co-deposited impurity layers at different locations in the Tokamak will be quite different. We addressed this challenge by developing the Classified OPC-LIBS (COPC-LIBS) model, an enhanced version of OPC-LIBS with pre-classification to offset matrix effects in LIBS analysis. For tungsten in the co-deposition layers, the root mean square (RMSE) calculated by the CF-LIBS method was 14.7, the OPC-LIBS method was 11.5, and the newly invented COPC-LIBS was reduced to only 5.1. The COPC-LIBS method is a highly efficient technique that can precisely measure the distribution of co-deposited layers on the surface of inner wall materials. The diagnostic data obtained from this method will provide valuable insights into the interaction between plasma and wall materials during the operation of fusion devices.

Effect of metal impurities on the adsorption energy of cesium and work function of the cesiated Mo (0 0 1) surface

Based on the DFT method, the effects of copper and tungsten impurities present in the negative ion source of neutral beams on the cesiated surface were studied, including their effects on the adsorption energy of cesium on the surface and the surface work function. The results indicate that copper impurities significantly increase the average adsorption energy of cesium, whereas tungsten has limited enhancement on the average adsorption energy of cesium and may even reduce it. The work function calculations show that, at cesium coverages below 4/16 θ, copper impurities cause a significant increase in the work function. However, at cesium coverages above 6/16 θ, high-coverage copper impurities lead to a further decrease in the work function, causing the cesium coverage corresponding to the lowest work function to shift towards higher cesium coverage. Under any tungsten impurity and cesium coverage, tungsten impurities can significantly increase the surface work function, with the maximum increase reaching 0.50 eV. The dipole moment density analysis shows that in most cases, impurities significantly reduce the dipole moment density of the cesiated surface, except when the coverage of cesium and copper impurities is above 6/16 θ. The charge transfer results show that the copper impurity layer has more positive charge compared to the tungsten impurity layer, which significantly affects the dipole moment density of the surface system. In addition, adsorbed atoms cause electrons in the molybdenum atomic layer to migrate to the surface, resulting in the molybdenum substrate having a pronounced negative dipole moment.

Influence of growth temperature on the properties of aluminum nitride thin films prepared by magnetron sputter epitaxy

High quality, uni-polar, epitaxial AlN with minimum oxygen content promises excellent surface acoustic wave and bulk acoustic wave resonator characteristics such as high electromechanical coupling coefficient and power handling capabilities, which is particularly useful for RF filter applications. By systematically varying the growth temperature, the study investigates its impact on the oxygen levels, defect states, and crystallographic texture of the AlN thin films using a combination of atomic force microscopy, X-ray diffraction, time-of-flight secondary ion mass spectrometry, spectroscopic ellipsometry, scanning transmission electron microscopy, as well as room temperature and temperature dependent I–V measurements. The research demonstrates that the films grown at a temperature of 700°C exhibit the most favorable results. These films exhibit the lowest oxygen levels, possess epitaxial growth, and display the highest crystalline quality (XRD AlN 0002 ω−FWHM=1.3°). Additionally, these films demonstrate a significant reduction in sub-bandgap absorption. By comparing the cathode current measured during deposition, we suggest that the presence of an impurity layer formed during idle time between depositions as a possible source of oxygen in the sputter chamber. In addition, the study presents a possible model to explain the mixed polarity observed in AlN and proposes various ways to achieve uni-polar AlN on silicon substrates.

МОДЕЛИРОВАНИЕ ИСХОДНОЙ ЗАСОРЕННОСТИ ЗЕРНОСМЕСИ ПО ВЕЛИЧИНЕ ЗАГРУЗКИ ТРИЕРА И ПАРАМЕТРАМ РАСПРЕДЕЛИТЕЛЬНЫХ КОРОБОВ

Investigation of the dosing quality of the impurity component at low loading conditions of the experimental trier and low initial clogging with a long impurity using three distribution boxes with dimensions: 600 × 14 × 13 mm; 600×24×13 mm; 600×24×21 mm are made. Dosing quality indicators - the standard deviation and the coefficient of variation for single, pair, triple, quadruple and five distributing boxes, characterizing the required linear density of the distribution of the impurity component on the feeder belt, have been established. It has been established that the use of these boxes provides high dosing stability. The coefficient of variation under different conditions of their loading does not exceed 4.75%. Filling boxes with dimensions of 600×14×13 mm with shaking of impurities provides a higher quality of dosing: the standard deviation is lower by 18.9 - 47.32%, the coefficient of variation is by 23.96 - 49.45% for different frequency of unloading boxes at formation of the linear density of the impurity layer on the tape. A number of model compositions of grain mixtures, providing for the supply of 1.2 t / h, the variability of the initial contamination in the range of 0.46 - 6.65%; for the supply of 1.83 t/h, the range of initial contamination is 0.3 - 4.3%; for the supply of 2.45 t/h, the range of initial contamination is 0.22 - 3.25%; for the supply of 3.07 t/h, the range of initial contamination is 0.18 - 2.6%; for the supply of 3.71 t/h, the range of initial contamination is 0.15 - 2.15%; for the supply of 4.35 t/h, the range of initial contamination is 0.125 - 1.8%. established on the basis of the performed calculations. Distribution boxes of small cross section provide 20 interval values with a minimum step for each range of initial contamination, which allows you to qualitatively control the experiment when using a grain mixture with low values of contamination of the grain mixture and productivity of the trier.

Study on Dolomite Thin Layers and Nodules in the Qingshankou Formation Shale Oil Reservoir of Gulong Sag

Recently, 15.1 billion tons of shale oil geological resources were discovered in the Qingshankou Formation of Gulong Sag, Songliao Basin, and this discovery has attracted considerable attention. Thus far, the sedimentary environment and diagenetic process of the Qingshankou Formation in Gulong Sag, particularly the reservoir space and accumulation mechanism of the shale oil, are unclear, which has seriously affected the exploration and development of shale oil. Based on detailed core and thin section observation, thin section analysis, mineral analysis, and geochemical analysis, thin layers and concretions of dolostone in Qingshankou Formation shale in Gulong Sag are studied. Three types of layers and nodules can be seen in the core and thin sections: the first is composed of very pure micrite, powdery calcite, or dolomite (dolomite greater than 90%); the second are argillaceous dolomite thin layers or nodules (dolomite content of approximately 75–90%); and the third is a highly impure dolomite thin layer (dolomite content between 50–75%). The chemical composition of three kinds of dolomite thin layers and nodules is different: the contents of CaO and MgO of the pure dolomite thin layer and nodules are more than 40%. The contents of CaO and MgO in the thin layer and nodules of argillaceous dolomite are between 30 and 40%. The content of CaO and MgO in the impure dolomite thin layers and nodules is less than 30%. The reservoir space is developed at the micron or nanometer scale in the thin dolomite layers and nodules, although most of these layers are filled with asphalt. The development of thin layers and nodules of dolomites is related to a dry and hot depositional climate and influenced by hydrothermal fluids. The findings presented here provide important information for exploiting the newly discovered shale oil resources. Many dolostone thin layers and nodules have curved silt veins, and the bending coefficient is 1.48, indicating that the dolostone thin layers and nodules have undergone compaction after formation.

ОБОСНОВАНИЕ ПАРАМЕТРОВ ЛЕНТОЧНОГО ПИТАТЕЛЯ ДЛЯ ПОДАЧИ ПРИМЕСИ В ЭКСПЕРИМЕНТАЛЬНЫЙ ТРИЕР

The requirements and technical possibilities for ensuring the reproducibility of experimental conditions in the study of screener technologies for cleaning grain mixtures in terms of the stability of their component composition over time, by means of separate feeding of components into the screener, are substantiated. A belt feeder that makes it possible to ensure the reproducibility of experiments with the initial clogging of the grain mixture in the range Zi = 1 - 3% and the productivity of the trier WT = 1.2 - 4.35 t / h is proposed for impurity components with high particle cohesion (oats, wild oats). The distribution of the impurity component along the length of the tape is carried out by means of a box without a bottom. The parameters of the box section were adopted based on the analysis of the contradiction, which consists in the fact that an increase in the horizontal section of the box (Sk) leads to an increase in the relative error in the distribution of the impurity component during its laying, and a decrease in Sk increases the dynamics of the formation of an impurity layer on the tape, reducing the efficiency of using its width. The box parameters turned out to be preferable for the experimental conditions at Zi = 1 - 3% and Wt = 1.2 - 4.35 t/h: width - 60 mm; height - 70 mm. A significant influence of the dynamics of the formation of an impurity layer on the tape was experimentally established: the angle of repose decreases by a factor of 2.5 (30° to 12°); the layer width increases by 1.6 times (from 170 mm to 270 mm). Reducing the dynamic impact on the impurity component by reducing the height of the box leads to a decrease in the efficiency of using the width of the tape - the cross section of the impurity layer becomes trapezoidal. Prevention of impurity losses in the feeder operation is ensured by flexible collars fixed on the edges of the belt. The qualitative distribution of impurities along the length of the box in experiments with partial loading of the trier is carried out by a special leveler - a vertical gate placed in a slider with the possibility of adjusting the position and fixing it with a clamp. To control the distribution of impurities in the box, it is advisable to make at least one of its side walls from a transparent material.

Diagnostic study of impurity deposition in fusion device by calibration-free laser-induced breakdown spectroscopy

The quantification of impurities in fusion devices is important to improve understanding of all impurity-related issues and their solutions. In this study, the deposition of the impurity layer on the lower hybrid wave gas puffing pipe (LHW-GPP) used in the Experimental Advanced Superconducting Tokamak (EAST) was characterized. The calibration-free laser-induced breakdown spectroscopy (CF-LIBS) was employed to resolve the impurity deposition of the unknown standard by focusing the laser at various spot positions on the sample surface. The impurity elements that appeared in the spectrum of deposition are copper (Cu), tungsten (W), molybdenum (Mo), lithium (Li), silicon (Si), and carbon (C). The laser ablation of impurity showed an uneven deposition pattern. Each laser pulse depicted the different concentrations of the impurity elements. The results obtained from the quantification and the depth profiling showed that the impurity deposition was composed of eroded materials caused by the plasma-surface interactions with the divertors, main wall, limiters, and supporting structure materials. The exponential decrease in impurity signals and constant behavior of substrate intensity were also observed during consecutive laser shots. The study provided the estimation of impurity contents in the fusion plasma.

Electrochemical Performance of LBO-coated Ni-rich NCM Cathode Material: Experimental and Numerical Approaches

Ni-rich NCM-based cathode materials have garnered significant research interest for the development of high-performance lithium-ion batteries (LIBs) owing to their high energy capacity and low cost. However, they undergo several electrochemical degradation reactions that deteriorate the cathode performance. To alleviate the deterioration of the cathode, researchers have adopted surface coating materials, especially Li3BO3 (LBO), which demonstrates a superior modification effect, for Ni-rich NCM. Here, we investigate the electrochemical characteristics of an LBO-coated Ni-rich NCM cathode via experimental and numerical approaches. The cathode is synthesized through a wet chemical deposition method, and electrochemical measurements are conducted using coin half-cells. To further understand the effect of coating layer on the electrochemical performance, we developed an electrode coating model with modifying the porous electrode model. The model employs an impurity layer (Li2CO3 and LiOH), a protective layer (LiF), and a coating layer (LBO) to predict the discharge performance of LIBs. The validation results of the model are consistent with the experimental results. Electrochemical prediction results demonstrate that the LBO-coated Ni-rich NCM cathode would increase the discharge capacity.

Unexpected features in the optical vibrational spectra of δ-UO3

Uranium trioxide displays a complex chemical phase space, with at least six structurally distinct polymorphs accessible via different synthetic routes. Remarkably, despite its technological importance, full structural and electronic characterization of these polymorphs remains an open area of study. δ-UO3 in particular has attracted significant theoretical attention due to its high point group and space group symmetries, having U (VI) in octahedral coordination with polyhedra interconnected through corner-sharing to build a 3-D cubic lattice with space group symmetry Pm-3m and Z = 1. Critical experimental information, such as its optical vibrational spectra, are not known. Here, we study the Raman and infrared (IR) spectra of δ-UO3 together with the support of density functional theory (DFT) calculations for spectral interpretation. A symmetry analysis of the DFT-predicted phonon eigenmodes indicates that δ-UO3 should have two IR active modes and no Raman active modes. Experimental results, however, indicate significant Raman scattering from δ-UO3. We therefore propose four potential explanations for this apparent contradiction: a possible tetragonal distortion to the cubic cell, the existence of a surface impurity layer, vacancy scattering, and structural activation of Raman signal. We use powder X-ray diffraction and confocal Raman spectroscopy with depth profiling to investigate these possibilities and suggest future experiments to explore this phenomenon in more detail. Understanding the lattice dynamics of δ-UO3 is important for identification of technogenic U phases via Raman and infrared spectroscopy and our results indicate that the simple understanding of δ-UO3 as a high-symmetry cubic structure should be reconsidered.

(Invited) Garnet-Type Electrolytes for All-Solid-State Lithium Metal Batteries

All solid-state Li batteries are foreseen as the future state of battery technology due to their safety, high energy density, and high potential window as compared to the present organic liquid electrolyte batteries. Li-ion conducting garnet-type electrolytes have received considerable research interests due to their compatibility with Li metal anode, good ionic conductivity (10-3 S/cm) and wide electrochemical window (~ 6V vs. Li).1 Garnet-type Li6.5La3-xAxZr1.5-xTax+0.5O12 (A = Ca, Sr, Ba; x = 0.1, 0.5) solid electrolytes were prepared by conventional solid-state synthesis and spark plasma synthesis (SPS).2-4 The formation of the cubic garnet-type structure was confirmed by powder X-ray diffraction (PXRD). Microstructure of the solid electrolytes were analysed by scanning electron microscopy (SEM) and cross-sectional analyses showed that the SPS processed samples are highly dense compared to the same compositions prepared by conventional solid-state route. The AC electrochemical impedance spectroscopy (EIS) was used to measure the impedance of solid electrolytes and found that all samples exhibit bulk conductivity in the order of 10-4 S/cm at room temperature. SPS processed samples showed an excellent Li-ion charge transfer resistance and the highest critical current density compared to the samples prepared by conventional solid-state synthesis. X-ray photoelectron spectroscopy (XPS) analyses were conducted on SPS-processed samples to quantify the impurity layers on garnet surface. Electrochemical performance of a hybrid cell consisting of liquid Li-ion electrolytes and garnet electrolyte will be discussed. References Wang, K. Fu, S. Palakkathodi Kammampata, D. W. McOwen, A. Junio Samson, L. Zhang, G. T. Hitz, A. M. Nolan, E. D. Wachsman, Y. Mo, V. Thangadurai and L. Hu, Chem. Rev., 2020, 120, 4257–4300.Palakkathodi Kammampata, R. H. Basappa, T. Ito, H. Yamada and V. Thangadurai, ACS Appl. Energy Mater., 2019, 2, 1765–1773.Palakkathodi Kammampata, H. Yamada, T. Ito, R. Paul and V. Thangadurai, J. Mater. Chem. A, 2020, 8, 2581–2590.Yamada, T. Ito, S. P. Kammampata and V. Thangadurai, ACS Appl. Mater. Interfaces, 2020, 12, 36119–36127.

Origin of Lithiophilicity of Lithium Garnets: Compositing or Cleaning?

AbstractGarnet‐type Li6.5La3Zr1.5Ta0.5O12 (LLZTO), a promising solid‐state electrolyte, is reported to exhibit lithiophobicity. Herein, it is demonstrated that the origin of the lithiophobicity is closely related to the surface compositions of both the lithium and LLZTO. Surface impurities with high melting points such as Li2O, Li2CO3, LiOH, or LiF inhibit the wettability between lithium metal and LLZTO, and the widely adopted compositing strategy may improve the wettability by merely breaking the surface impurity layers. A simple but effective “polishing‐and‐spreading” strategy is proposed to remove the surface impurities and obtain clean Li/LLZTO interfaces. Thus, a tight and continuous Li/LLZTO interface with an interfacial resistance of 17.5 Ω cm2 is achieved, which leads to stable cycling of the symmetric Li cells and a critical current density up to 2.8 mA cm–2. This work provides a new perspective to understand the lithiophilicity of garnet‐type electrolytes and contributes to designing robust Li/garnet interfaces.

​Testing of Bituminous Coal and its Impurity Layers as in situ Ameliorant of Physico-chemical Soil Reclamation Properties of Coal Mine

Background: Coal mined reclaimed soil is prone to losing organic carbon content, increased soil acidity, soil structural damage and compact. This degradation of soil properties can be reduced and improved by applying coal and coal impurities as potential ameliorants. This research was aimed at knowing the potential of coal and coal impurity (partings) to improve the physicochemical properties of coal mine reclaimed soil. Methods: The research was conducted using the randomized block design (RBD) with 3 types of treatment and was in a pot experiment. The tried treatments, among others, are 1) Control (K0), 2) Coal ameliorant (C) and 3) Coal impurity (partings) ameliorant (B). Coal and coal impurity (partings) were both tested with 5 doses, which respectively consisted of 5, 10, 15, 20 and 25 tons ha-1. Result: The results showed that the application of bituminous coal ameliorant and coal impurity significantly affected on physicochemical soil reclamation properties of coal mines. Both types of ameliorants had an effect on increasing pH and decreasing Al-dd contents but were only significantly different from the control (K0). Amelioration significantly affected the increase in the C-organic, Humic acid and N total content with doses of the applications bituminous coal C5, while coal impurity doses of C4.

GYROTROPY FEATURES OF AN IMPERFECT OPTICALLY ACTIVE 1D PHOTONIC ORIENTATIONALLY DISORDERED CRYSTAL

The paper is devoted to gyrotropic characteristics of a non-ideal 1D photonic crystal with an arbitrary number of sublattices (of which one is the optically active potassium dithionate K2S2O6) and to their variation due to a random layer substitution in the K2S2O6 sublattice by modeling impurity layers of an orientationally disordered molecular crystal. We adopt a microscopic approach to study the specific (per unit volume) light polarization plane rotation angle in the exciton spectrum region and perform the numerical calculation of the superlattice optical activity dependence on concentrations of impurity layers and of point-like defects (orientationally disordered molecules) which the latter contain.

Storage degradation mechanism of layered Ni-rich oxide cathode material LiNi0.8Co0.1Mn0.1O2

With advantages such as high specific capacity and low cost, Ni-rich layered oxides are considered to be ideal cathode materials for power batteries. However, due to the high sensitivity of materials to air, structural degradation occurs during transportation and storage, resulting in the formation of an impurity layer. The degradation of the structure will weaken the comprehensive properties of Ni-rich cathode materials. The impurity layer will bring difficulties to the subsequent electrode manufacturing process, which seriously limits the practical application of Ni-rich materials. Therefore, it is particularly important to explore the storage decline mechanism of Ni-rich materials. Herein, the decay mechanism of structure and electrochemical properties of LiNi0.8Co0.1Mn0.1O2 materials after storage at room temperature and high humidity and high-temperature and humidity were studied. It is found that the instability of Ni3+ leads to the appearance of NiO rock salt phase on the surface of the material, accompanied by the formation of reactive oxygen species. Lithium and reactive oxygen species in the material react with H2O and CO2 in the air to form surface residual lithium compounds. The formation of the inert NiO layer and residual lithium compounds hinders the diffusion kinetics of Li+, resulting in serious capacity loss. During the high-temperature storage process, the material forms thicker residual lithium compounds, which aggravates the decay process. After 28 days of high-temperature storage, a residual lithium compound layer of about 7 nm thickness was formed, which seriously hindered the transmission of Li+. This study is helpful to deeply understand the storage failure behavior of Ni-rich cathode materials and promote the large-scale industrial production and application of Ni-rich cathode materials.

Unraveling the mechanisms of carbon nanotube growth by chemical vapor deposition

The mechanisms of carbon nanotube (CNT) growth by chemical vapor deposition of acetylene on Fe/SiO2:Al2O3 (zeolite Y) catalyst are unraveled through a combined computational and experimental study. CNTs are synthesized in a horizontal reactor under atmospheric pressure within the temperature range 650 °C–850 °C and characterized by SEM, TEM and Raman spectroscopy. A macroscopic computational fluid dynamics (CFD) model accounting for fluid flow, heat transfer and species transport is developed for the process, incorporating also kinetic expressions for acetylene surface decomposition, acetylene gas-phase reactions, carbon diffusion through the bulk of the catalyst, carbon surface accumulation on the catalyst surface and eventually, CNTs growth. The experimental behavior of the CNTs growth can be accurately described by the proposed macroscopic model. Most importantly, theoretical predictions suggest that there are two distinct temperature regimes for CNTs formation: at the low temperature regime, the process is dominated by the competition between carbon diffusion through the catalyst and carbon impurity layer formation on the catalyst surface, while at higher temperature, the gas-phase reactions of acetylene prevails, releasing byproducts that deposit on the catalyst surface in the form of carbon impurities. Finally, using the developed computational approach, the catalyst lifetime, which is directly affected by these mechanisms, is correlated with the CNTs growth process.

Influence of Impurities in Electrical Contacts on Increasing the Efficiency of Energy Transmission

The aim of this paper is to analyze the heat distribution in the high-current electrical contact under the action of an assumed current of 3000 A using mathematical modeling and simulation. Electrical contacts that carry high currents are an essential component of many electric devices. In transmission and distribution systems, the electrical contacts are of particular importance because they must withstand adverse weather conditions that decrease their effectiveness. Therefore, it is essential to detect any rise in temperature of the electrical contact to ensure efficient and reliable energy transmission. For this paper, simulations of the temperature field in direct electrical contact were carried out in ANSYS and discussed. During the simulation, a high-current electric contact was exposed to 3000 A current and the change of the adverse effects of contaminated contact layers affected temperature field. According to the results, electric contact in good condition (represented by impurity layer of lower resistivity) had a temperature of 80 °C lower than an electric contact that was worn out (represented by impurity layer of higher resistivity). The investigation of the resistivity of contaminated contact layers has led to the determination of permissible values for the power grid operators to maintain these types of devices when temperatures rise.

Elucidating the Humidity-Induced Degradation of Ni-Rich Layered Cathodes for Li-Ion Batteries.

Ni-rich layered oxides, in a general term of Li(NixCoyMn1-x-y)O2 (x > 0.5), are widely recognized as promising candidates for improving the specific energy and lowering the cost for next-generation Li-ion batteries. However, the high surface reactivity of these materials results in side reactions during improper storage and notable gas release when the cell is charged beyond 4.3 V vs Li+/Li0. Therefore, in this study, we embark on a comprehensive investigation on the moisture sensitivity of LiNi0.85Co0.1Mn0.05O2 by aging it in a controlled environment at a constant room-temperature relative humidity of 63% up to 1 year. We quantitatively analyze the gassing of the aged samples by online electrochemical mass spectrometry and further depict plausible reaction pathways, accounting for the origin of the gas release. Transmission electron microscopy reveals formation of an amorphous surface impurity layer of ca. 10 nm in thickness, as a result of continuous reactions with moisture and CO2 from the air. Underneath it, there is another reconstructed layer of ca. 20 nm in thickness, showing rock salt/spinel-like features. Our results provide insight into the complex interfacial degradation phenomena and future directions for the development of high-performance Ni-rich layered oxides.

A high temperature cell for investigating interfacial structure on the molecular scale in molten salt/alloy systems.

In this work, we describe the designand development of an in situ neutron reflectometry cell for high temperature investigations of structural changes occurring at the interface between inorganic salts, in their molten state up to 800°C, and corrosion resistant alloys or other surfaces. In the cell, a molten salt is confined by an annular ring of single crystal sapphire constrained between the sample substrate and a sapphire plate using two gold O-rings, enclosing a liquid salt volume of 20 ml, along with a dynamic cell volume to accommodate expansion of the liquid with heating. As a test case for the cell, we report on an in situ neutron reflectometry measurement of the interface between a eutectic salt mixture of MgCl2-KCl (32:68 molar ratio) and a single crystal sapphire substrate at 450°C, resulting in the formation of a 60 Å layer having a scattering length density of 1.72 × 10-6 Å-2. While the origin of this layer is uncertain, it is likely to have resulted from the salt reacting with an existing impurity layer on the sapphire substrate.

Effect of humidity and contaminants on dry band formation in Outdoor Distribution Current Transformer 20 kV

This study reports the effect of humidity and pollutants on the formation of dry band phenomena on the insulation surface of an outdoor 20 kV distribution current transformer. From the results of measurements at high humidity 95% and high conductivity 36 mS/cm at a working voltage of 2-20kV test there is a change in the curve of increasing the value of the leakage current which is very volatile. Wet layer of impurity will cause a drastic decrease in surface resistance resulting in a large increase in leakage current. At a high conductivity of 36 mS/cm, the results of the measurement of surface resistance at low humidity of 55% worth 30.2 giga ohms decreased to 2.1 giga ohms at high humidity of 95%. While the value of the leakage current curve is very fluctuating from the value of 206 - 678 A at high conductivity with heavy pollutants. This information confirms the hypothesis that the boundary region of the two air-solid dielectrics of the epoxy resin causes surface discharge problems in dry band formation due to an increase in the non-uniform local electric field in the impurity layer adhering to the surface of the distribution current transformer. Keywords : leakage current, dry band, surface discharge, contaminants

Implementation of forward osmosis to concentrate alpha-ketoglutaric acid from fermentation broth: Performance and fouling analysis

Forward osmosis (FO) was demonstrated as a promising method to concentrate alpha-ketoglutaric acid in fermentation broth. Using a model solution containing alpha-ketoglutaric acid, the impact of the initial pH value on water flux, reverse salt flux, and rejection of alpha-ketoglutaric acid were first elucidated. Results from this study show that water flux was not affected by feed solution pH. However, feed solution pH could influence alpha-ketoglutaric acid rejection and reverse salt flux. The highest alpha-ketoglutaric acid rejection of 99.7% and lowest reverse salt flux were observed at pH 5. Multi-component model and real fermentation broth were then used to validate FO application for concentrating alpha-ketoglutaric acid. Water recovery of 80% was achieved without severe membrane fouling. In addition, membrane fouling analysis show that the built-up fouling layer of impurities is flaky and of unstable nature, suggesting that membrane fouling could be reversible. Knowledge of the fouling layer formation can contribute to the development of an effective method of pretreatment of the fermentation broth and cleaning FO membranes in the future.