Effect Of Impurities Research Articles

Investigation of the impurity effect on the kinetics of thermal decomposition of natural gypsum at high temperatures

Natural gypsum is the most common sulfate on our planet, which is widely used in construction due to its excellent astringent properties, environmental friendliness, thermal and fire resistance, accessibility in nature and low price. Currently, the influence of modifiers, impurities and additives that can improve the strength, acoustic and thermal insulation characteristics of gypsum, which is so important in modern architecture, construction and reducing power consumption, is being increasingly studied. However, additives and impurities, controlled and uncontrolled, as in natural gypsum, can unpredictably affect the thermal stability and fire resistance of gypsum. The purpose of our work is to study the thermal characteristics of gypsum from various deposits in a wide temperature range. Our work shows that the temperature and rate of dissociation of gypsum directly depends on impurities that can change the process of its decomposition. As a result of the decomposition of natural gypsum with impurities, new phases are formed.It has been experimentally shown that the process of thermal destruction of gypsum with impurities has a complex multistage character, which is described by successive reactions of the nth order of the Avrami-Erofeev equation. It can be assumed that the reaction mechanism consists in the rapid formation of numerous nucleation centers on the surface of solid anhydrite. Kinetic parameters of thermal decomposition of gypsum of complex composition and phase formation at high temperatures are calculated. This experimental study shows the dependence of thermal stability on the amount and grade of impurities in gypsum. The results obtained contribute to the improvement of the basic concepts of the mechanism of decomposition of gypsum, as well as the explanation of some high-temperature phase formation processes in nature.

Revealing the impact of CO2 exposure during calcination on the physicochemical and electrochemical properties of LiNi0.8Co0.1Mn0.1O2.

The synthesis atmosphere plays a fundamental role in determining the physicochemical properties and electrochemical performance of NMC811 cathode materials used in lithium-ion batteries. This study investigates the effect of carbonate impurities generated during synthesis by comparing three distinct samples: NMC811 calcined in ambient air, NMC811 calcined in synthetic air to mitigate carbonate formation, and NMC811 initially calcined in ambient air followed by annealing in synthetic air to eliminate carbonate species. Physicochemical characterization through XRD, SEM, FTIR, and TGA techniques revealed noticeable differences in the structural and chemical properties among the samples. Electrochemical assessments conducted via coin-cell testing demonstrate superior performance for materials synthesized in synthetic air, exhibiting an enhanced discharge capacity of 145.4 ± 4.8 mA h g-1 compared to materials synthesized in normal air (109.4 ± 4.3 mA h g-1) at C/10. More importantly, sample annealing in synthetic air after air calcination partially recovers the electrochemical performance of the cathode (142.1 ± 4.6 mA h g-1 at C/10) and this is related to the elimination of carbonate species from the ceramic powder. These findings highlight the importance of controlling synthesis conditions, particularly the atmosphere, to tailor the properties of NMC811 cathode materials for optimal lithium-ion battery performance.

The Effect of Electrolyte pH and Impurities on the Stability of Electrolytic Bicarbonate Conversion.

Electrolytic bicarbonate conversion holds the promise to integrate carbon capture directly with electrochemical conversion. Most research has focused on improving the faradaic efficiencies of the system, however, the stability of the system has not been thoroughly addressed. Here, we find that the bulk electrolyte pH has a large effect on the selectivity, where a higher pH results in a lower selectivity. However, the bulk electrolyte pH has no effect on the stability of the system. A decrease in CO selectivity of 30% was observed within the first three hours of operation in an optimized system with 3 M KHCO3 and gap between the membrane and electrode. Single-pass electrolyte experiments at various constant pH values (8.5, 9.0, 9.5, and 10.0), show that only at a pH of 10 the CO selectivity was stable during three hours, reaching a faradaic efficiency toward CO of only 18% as compared to an initial 55% at pH 8.5. Trace metal impurities present in the electrolyte were found to be the cause of the decrease in stability as these deposit on the electrode surface. By complexing the trace metal ions with ethylenediaminetetraacetic acid (EDTA), the metal deposition was avoided and a stable CO selectivity was obtained.

Effect of Nickel Impurities in Pyrite on Catalytic Degradation of Thiosulfate

The effects of nickel content in nickel-bearing pyrite on photocatalytic properties, light absorption properties, and oxidative decomposition of thiosulfate were studied. The leaching experiments show that the consumption of thiosulfate in the Cu2+-ethylenediamine (en)-S2O32− system increases with an increase in nickel content in nickel-bearing pyrite. The consumption of Cu(en)22+ initially increases and then decreases with an increase in leaching time. There is a clear correlation between the change trend in its consumption and the doping amount of nickel in pyrite. The XPS results show that in the Cu2+-ethylenediamine (en)-S2O32− leaching gold system (temperature 25 °C, time 35 h, solution: 0.1 mol/L S2O32−, 5 mmol/L Cu(en)22+, 200 mL solution), the nickel of pyrite-containing nickel can be transferred to the leaching solution and becomes nickel ion. In this leaching system, Cu(II), which was originally complexed with en, is reduced to Cu(I) in a short time. The consumption of Cu(en)22+ increased rapidly in the 5 h period and then decreased gradually after 5 h. The results showed that the presence of free Ni2+ in the solution facilitated the conversion of bivalent copper ions to monovalent copper ions. Free Ni2+ ions can compete with Cu2+ ions for en ligands. When ethylenediamine complexes with Ni2+, the decomposition of Cu(en)22+ into Cu(en)+ and en occurs more rapidly. And the en, which was originally to be oxidized with Cu(en)+ to form Cu(en)22+, forms Ni(en)22+. As a result, the concentration of Cu(en)22+ continues to decrease in a short period of time.

Tetrahedral shape and Lambda impurity effect in $^{80}$Zr with a multidimensionally constrained relativistic Hartree-Bogoliubov model

Abstract This study investigates the tetrahedral structure in $^{80}$Zr and Lambda ($\Lambda$) impurity effect in $^{81}_{~\Lambda}$Zr using the multidimensionally constrained relativistic Hartree-Bogoliubov model.
 The ground states of both $^{80}$Zr and $^{81}_{~\Lambda}$Zr exhibit a tetrahedral configuration, accompanied by prolate and axial-octupole shape isomers. 
 Our calculations reveal there are changes in the deformation parameters $\beta_{20}$, $\beta_{30}$ and $\beta_{32}$ upon $\Lambda$ binding to $^{80}$Zr, except for $\beta_{32}$ when $\Lambda$ occupies $p$-orbits. 
 Compared to the two shape isomers, the $\Lambda$ particle exhibits weaker binding energy in the tetrahedral state when occupying the $1/2^+[000](\Lambda_s)$ or $1/2^-[110]$ single-particle states. In contrast, the strongest binding occurs for the $\Lambda$ particle in the $1/2^-[101]$ state with tetrahedral shape. A large $\Lambda$ separation energy may not necessarily correlate with a significant overlap between the density distributions of the $\Lambda$ particle and the nuclear core, particularly for tetrahedral hypernuclei.

Effect of impurity and radiation defects on the scattering of normal and fluctuation carriers in YBa2Cu3O7–δ and Y1–zPrzBa2Cu3O7–δ single crystals

Effect of impurity and radiation defects on the scattering of normal and fluctuation carriers in YBa2Cu3O7–δ and Y1–<i>z</i>Pr<i>z</i>Ba2Cu3O7–δ single crystals

Corrosion of iron in liquid uranium hexafluoride at 80 °C. Part I: Normal and abnormal experimental kinetics

The results reported here are the first on pure iron corrosion in liquid UF6 at 80 °C. Two kinetic behaviours have been observed: one led to micrometric scales (from micron to hundreds of microns after several months) and the other one to hundreds of nanometers for several months. The higher corrosion kinetics resulted in the presence of impurities such as NOxF complexes formed by interaction between the medium and the reactor material. These NOxF catalysed the corrosion reaction leading to a corrosion mechanism controlled by the cathodic reaction rate. Effect of impurities in UF6 coming from experimental conditions or nature of uranium ore should then be systematically and carefully checked. Whatever the corrosion kinetics and the presence of impurities, the nature of the layer was identical: a duplex fluoride scale composed of an iron rich layer, FeF2, and a uranium rich layer evolving over time from U2F9 to UF5.

Effect of oxygen or copper impurities on the work function of cesiated surfaces under co-existence with hydrogen: A study about negative hydrogen ion sources for neutral beam injection systems

This study investigates the effect of oxygen and copper impurities on the work function of the Cs/H/Mo (001) surface based on the Density Functional Theory (DFT) method. First, the deposition of 2/16 θ impurities on the Cs0.5/H0.5/Mo (001) surface (the subscript 0.5 represents 8/16 θ coverage) is studied. It is found that the deposition of impurities beneath the cesium layer and oxygen impurities as atoms, and in a high-symmetry configuration, both lower the surface system energy. As the impurity coverage increases, it is observed that impurity deposition with a coverage of less than or equal to 8/16 θ effectively reduces the work function of the Cs0.5/H0.5/Mo (001) surface. However, as the cesium and hydrogen coverage increases, the impurities are no longer effective at reducing the work function. Moreover, when the cesium coverage reaches 16/16 θ, the surface work function approaches that of a cesium metal surface. Another important discovery is that when oxygen impurities are deposited above the cesium layer on the Cs0.5/H0.5/Mo (001) surface, a reduction in the surface work function is observed. This anomalous phenomenon is attributed to significant charge polarization caused by the deposition of oxygen impurities. The migration barriers of impurities traversing the dense cesium layer to the Mo (001) substrate are evaluated using the climbing image nudged elastic band (CI-NEB) method. Oxygen impurities tend to traverse the cesium layer in molecular form, facing a minimum barrier of 0.52 eV, while copper atoms encounter a lower barrier of 0.09 eV when traversing the cesium layer.

Investigation of the corrosion behavior of 29NC alloy in LiCl-KCl melt at 500 oC depending on the content of Li2O and LiOH from 0 to 2 mol. %

Molten chloride salt electrolytes are promising for use as a working medium for the implementation of high-temperature technologies. Alkali metal chlorides are an aggressive environment in relation to structural materials. One of the possible methods of reducing the corrosion damage of a structural material is the method of oxygen passivation of the surface of a metal or alloy by introducing a certain amount of oxygen-containing additives into the melt. The article considers the effect of oxygen-containing impurities (lithium oxide and lithium hydroxide) on the corrosive behavior of a metal material — an alloy of the composition iron–cobalt–nickel. To assess the corrosion resistance of materials, gravimetric analysis, micro-X-ray spectral analysis (XRSA) of the surface and cross-section sections, and X-ray phase analysis (XRF) of the sample surface were used. The dependences of the corrosion rate of the material on the concentration of oxygen-containing additives Li2O and LiOH are presented. Based on the data set of gravimetric, MRSA and XRF data, it was found that 29NC alloy samples in the LiCl–KCl–nLi2O salt melt are not susceptible to corrosion, but in the LiCl–KCl–nLiOH melt, the speed of the 29NC alloy increases significantly due to the interaction of the LiOH additive with the most electronegative component of the alloy — iron.

Leveraging multi-omics tools to comprehend responses and tolerance mechanisms of heavy metals in crop plants.

Extreme anthropogenic activities and current farming techniques exacerbate the effects of water and soil impurity by hazardous heavy metals (HMs), severely reducing agricultural output and threatening food safety. In the upcoming years, plants that undergo exposure to HM might cause a considerable decline in the development as well as production. Hence, plants have developed sophisticated defensive systems to evade or withstand the harmful consequences of HM. These mechanisms comprise the uptake as well as storage of HMs in organelles, their immobilization via chemical formation by organic chelates, and their removal using many ion channels, transporters, signaling networks, and TFs, amid other approaches. Among various cutting-edge methodologies, omics, most notably genomics, transcriptomics, proteomics, metabolomics, miRNAomics, phenomics, and epigenomics have become game-changing approaches, revealing information about the genes, proteins, critical metabolites as well as microRNAs that govern HM responses and resistance systems. With the help of integrated omics approaches, we will be able to fully understand the molecular processes behind plant defense, enabling the development of more effective crop protection techniques in the face of climate change. Therefore, this review comprehensively presented omics advancements that will allow resilient and sustainable crop plants to flourish in areas contaminated with HMs.

The effects of crystal orientation and common coal impurities on electronic conductivity in copper–carbon composites

The electronic conduction properties of copper–graphene composite materials including common coal impurities are studied. Exploring the transport properties for three crystallographic orientations [(111), (110), and (100)] of copper in copper–graphene composites, a strong orientational dependence on electronic conductivity is shown. Graphene exhibits near-ideal registries for (111) and (110) orientations, forming a connected network between grains that enables efficient carrier transport. The influence of non-carbon elements: nitrogen (N), oxygen (O), and sulfur (S) in graphene, representing possible structures in coal-based graphene are investigated. N, O, and S in graphene negatively impact the composite’s electronic conductivity relative to pristine graphene. A new method is introduced for visualizing the spatial distribution of electrical conduction activity in materials using the square of the electronic charge density near the Fermi level, based on the work of Mott. We call this technique the N2 method.

Impurity convection reversal caused by edge localized turbulence for generating a stationary edge radiative layer in the HL-2A tokamak

Abstract Effect of impurity on edge turbulence was investigated on the HL-2A tokamak by using Neon supersonic molecular beam injection (SMBI). For the first time, a stationary radiative layer accompanied by edge localized turbulence lasting more than 100ms is observed at the edge region ρ=0.7-0.9. This duration is much longer than the SMBI pulse length (1.2ms), indicating that the impurity diffusion is on the whole cancelled out by the impurity convection without spreading of the localized turbulence during this period. This implies that the impurity convection is reversed from positive to negative impurity density gradient region. This reversal could be explained by the parallel impurity compression mechanism. The observed turbulence is a broadband electrostatic turbulence (25-70 kHz) propagating in the electron diamagnetic drift direction with normalized poloidal wavenumber of 0.1≤ kθρs≤0.4. It has been found that the excitation of the edge localized turbulence strongly depends on the local collisionality. This feature is qualitatively predicted by the spectral multiscale gyrokinetic turbulence simulation, which suggests that the turbulence could be a dissipative trapped electron mode (DTEM). This experiment demonstrates that mutual interaction between externally injected impurity ions and edge turbulence can generate a stationary edge radiative layer and avoid impurity core accumulation. These results could provide a potential approach for the formation of a stable impurity radiative layer by impurity injection in tokamaks.

Effect of impurities on hydrogen defect stability and migration barrier in yttrium dihydride crystal

The impurity or alloying atoms in YH2 can alter the local electronic structure and so the hydrogen defect stability, as well as the H migration barrier energy. Thus, DFT calculations were employed to determine the effect of foreign elements from alkali and alkaline earth metals to transition metals and one critical impurity element, O, on H vacancy stability and retention characteristics in YH2. Results revealed that alloying elements act as hydrogen vacancy sinks by reducing the vacancy formation energy at neighboring sites. The implantation of non-magnetic foreign elements (s1, s2, and d10 valence electrons) in hydrogen energy landscape was calculated to be minor; while the hydrogen vacancy formation energy was reduced from 1.37 eV to 1.00 eV, the migration energy barrier of hydrogen was increased from 0.87 eV to 1.15 eV for non-magnetic foreign elements. The migration energy barrier monotonically decreased with increasing d-shell occupancy, reaching as low as 0.4 eV for Cr, Mo(d4), and Fe (d4). Alloying with late transition metals (d8 and d9) moderately impacted the hydrogen vacancy formation. Finally, it was found to be O addition into the YH2- lattice did not alter the energy landscape of hydrogen vacancies. Since alloyed YH2 has not been studied extensively, this study provides an atomistic understanding how alloying elements and impurities trap vacancies and affects hydrogen mobility YH2. Meanwhile, the main findings of this study may serve as guidelines for introducing alloying elements in ZrH2 as well.

Impurity effects on local electronic structure of twisted bilayer cuprates

Impurity effects on local electronic structure of twisted bilayer cuprates

First-principles thermodynamical modeling of molecular reactions on α-U(001) and α-UH3(001) surfaces and their influence on hydrogen activation

Density functional theory calculations coupled with thermodynamic analysis have been performed to investigate the reactions of hydrogen and impurity gases including O2, CO2, CO, N2 on α-U(001) and α-UH3(001) surfaces. Binding strength of adsorbates on α-UH3 is calculated to be weaker than α-U, suggesting enhanced poisoning-resistant properties of U-hydride compared to its metallic state. Surface phase diagrams of U under binary H2-O2, H2-N2 and H2-CO gaseous environments show that while N and C elements prefer to stay in their hydrogenated states on the hydride surface, isolated O atoms favorably interact with both α-U(001) and α-UH3(001), indicating the heavily poisoning effect of impurities containing oxygen. Global optimization of partially oxidized α-U(001) slabs induces surface geometry reconstruction and the activity of oxidized surfaces toward hydrogen adsorption can be linearly correlated with local electronic and atomic properties of the adsorption site.

Lifting of Gap Nodes by Disorder in Tetragonal FeSe_{1-x}S_{x} Superconductors.

The observation of time-reversal symmetry breaking and large residual density of states in tetragonal FeSe_{1-x}S_{x} suggests a novel type of ultranodal superconducting state with Bogoliubov Fermi surfaces (BFSs). Although such BFSs in centrosymmetric superconductors are expected to be topologically protected, the impurity effect of this exotic superconducting state remains elusive experimentally. Here, we investigate the impact of controlled defects introduced by electron irradiation on the superconducting state of tetragonal FeSe_{1-x}S_{x} (0.18≤x≤0.25). The temperature dependence of magnetic penetration depth is initially consistent with a model with BFSs in the pristine sample. After irradiation, we observe a nonmonotonic evolution of low-energy excitations with impurity concentrations. This nonmonotonic change indicates a transition from nodal to nodeless, culminating in gapless with Andreev bound states, reminiscent of the nodal s_{±} case. This points to the accidental nature of the possible BFSs in tetragonal FeSe_{1-x}S_{x}, which are susceptible to disruption by the disorder.

Shape coexistence in Ne isotopes and hyperon impurity effect on low-lying states

Shape coexistence in Ne isotopes and hyperon impurity effect on low-lying states

Effect of H2S on the corrosion behavior of austenitic and martensitic steels in supercritical CO2 at 550 °C and 20 MPa for Brayton cycle system

Corrosion of alloy materials significantly influences the stability and efficiency of the supercritical carbon dioxide (S-CO2) Brayton cycle. In this study, we investigated the corrosion behavior of the austenitic alloy SP2215 and the martensitic alloy X19CrMoNbVN11-19 (X19) in S-CO2 at 550°C and 20 MPa. The effect of impurities, H2S, on corrosion behavior was studied. After 900 hours, SP2215 formed a 1.1 μm thick oxide layer (Cr2O3). X19 formed a loose and porous double oxide layer of 4.1 μm (outer: Fe3O4, inner: FeCr2O4). After H2S doping, SP2215 had an oxide layer of 6.2 μm (FeS, SiO2, and Cr2O3), while X19 was 9.8 μm (outer: Fe3O4, SiO2, FexSy and Fe2O3, inner: FeCr2O4, Fe2SiO4 and Cr2S3). Metal sulfides formed and the corrosion layer thickened. This indicates that H2S not only changes the corrosion mechanism but also aggravates the corrosion. However, the corrosion of CO2 is dominant. SP2215 has better corrosion resistance than X19.

Effect of Electroslag Remelting on the Microstructure and Ballistic Penetration Characteristics of an Austenite‐Based Lightweight Steel

Herein, the effects of electroslag remelting (ESR) and impurities in ESR slag on the composition, microstructure, and properties of lightweight steel with a nominal composition in wt% of Fe‐20Mn‐10Al‐1.5C are studied. These results can provide a reference for the production of such steels using ESR and the design of the composition of such steels. The results show that ESR can make the contents of Si increase and that of S decrease, make the grain size decrease, make the phase transformation of austenite at about 540 °C change from spinodal decomposition to ordered transformation, make the contents of MnS and SiO2 and inclusions greater than 5 μm decrease, make the distribution of inclusions homogenize, and make the shape of inclusions change from long strip with sharp corners to spherical shape. ESR can improve its strength, plasticity, and antiballistic penetration properties.

Thermodynamic analysis of supercritical CO2 power generation system for waste heat recovery with impurities in CO2

Waste heat recovery from gas turbines is an effective method for meeting the demand for a more efficient and cleaner energy system with decreased CO2 emissions and lower environmental pollution. The supercritical CO2 Brayton cycle is a promising power conversion system for waste heat recovery. The advantage of the supercritical CO2 Brayton cycle can be attained based on its physical characteristics. However, when another fluid is mixed as an impurity in a system using pure CO2, physical characteristics of working fluid was changed and operation at the design point can be challenging. Therefore, it is important to verify the purity of CO2 and understand the effect of impurities in CO2 in advance. This study examined the effects of impurities in the working fluid of a supercritical CO2 power generation system for actual demonstration facilities. The effect of impurity, a CO2-based mixture, in a supercritical CO2 power generation system on waste heat recovery from an LM500 gas turbine was investigated. A purity test of industrial grade CO2, which was noted as 99.9 % pure by the supplier, was conducted to verify the composition of the working fluid. The results of the purity test showed that the supplied CO2 consisted of 99.076 % CO2 along with nitrogen, argon, oxygen, water, and methane. Based on the results of the purity test, sensitivity analyses of the CO2-based binary mixtures and industrial mixtures were performed. A design point analysis was conducted for the CO2-based industrial mixture in comparison with pure CO2, which has cycle efficiency of 16.15 %, gross power of 510.03 kW, mass flow rate of 12.55 kg/s, and waste heat recovery of 2119.06 kW. In the case of fixed waste heat with mass flow rate of 14.417 kg/s, the cycle efficiency decreased by 0.39 % and gross power increased by 66.14 kW. In the case of fixed mass flow rate with 1844.598 kW waste heat, the cycle efficiency decreased by 0.32 % and gross power decreased by 9.84 kW. In addition, the influence of the performance of the major components on the system performance was investigated.