Impurity Elements Research Articles

Microstructure evolution and solidification behaviour of ZrB2-SiC composite ceramics fabricated by laser surface zone-melting

Microstructure evolution and solidification behaviour of ZrB2-SiC composite ceramics fabricated by laser surface zone-melting were investigated. Microstructure coarsening at high scanning speed and microstructure refining after turning off the laser was observed due to the changes in the solidification rate. The solidification behaviour from bottom to top of the molten pool was studied, where there are some coarsen eutectic bands caused by the secondary heating of the melting pool on the solidified eutectic zone in the molten pool. The deviation of melt composition from the eutectic ratio due to the volatilization of SiC can form a coarse primary ZrB2 phase among fine eutectic structure (single-phase instability), and the constitutional supercooling due to the accumulation of impurity elements can form coarse eutectic dendrites among fine eutectic structure (two-phase instability). Both single-phase instability and two-phase instability are adverse to the mechanical properties, which should be prevented by adjusting the composition of raw materials and the solidification process.

Inhibition of Ti-rich precipitates and improvement of the irradiation resistance in V-4Cr-4Ti by adding La element

Four kinds of V-4Cr-4Ti-xLa (nominal composition x = 0, 0.1, 0.5, 1.0 wt.%) alloys with different La contents were prepared by vacuum arc melting. Three of them (x = 0, 0.1, 1.0 wt.%) were selected for single He+ (2000 appm for peak concentration) irradiation and sequential He+/V2+ (10 dpa for peak damage) irradiation at 550 °C. The results showed that the addition of La element could refine the grains by forming the second phase La2O3 particles. Moreover, the addition of La element reduced the sum of impurity elements concentration in the alloy, which inhibited the formation of Ti-rich precipitates and affected the vacancy concentration, thus affecting the evolution of He bubbles under different irradiation types. In addition, the V-4Cr-4Ti-1.0La alloy had a lower irradiation hardening after sequential He+/V2+ irradiation, which might be related to the removal of impurity elements. This work provided a reference for the performance optimization of vanadium alloy for fusion reactors.

Development and characterization of nano-magnesia-based refractories filled with graphite nanosheets

Thermo-mechanical and mechanical properties of Magnesia-Carbon (MgO–C) refractories are of great importance in industrial furnace applications and are greatly influenced by the amount of carbon in the MgO Matrix. In this research work, the effect of exfoliated graphite nanosheets (EGS) content on mechanical behavior and thermal shock resistance of MgO-based refractories was examined. MgO nanoparticles were synthesized by the co-precipitation method and micro-MgO particles were used as received. EGS was added in both micro and nano-MgO in variable amounts ranging from 0.5 to 2.5 wt % to study its effect on fracture strength and thermal shock resistance. The morphology of synthesized MgO nanoparticles and the fractured surfaces of the resultant composites were analyzed by field emission scanning electron microscopy (FESEM) coupled with energy dispersive x-ray (EDX) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and compression testing. The synthesized nano-MgO and as received micro-MgO particles were found to be of spherical morphology with no impurity elements as observed by FESEM and EDX mapping. XRD analysis did not show any phase change after the sintering of the composites. The FESEM and TEM images of the fractured surfaces of MgO-EGS refractory samples displayed the fine distribution of EGS. EGS were embedded in MgO particles, enhancing the composite-refractory samples' fractured strength. Fracture strength and thermal shock resistance were increased with the increasing amount of EGS in MgO. However, the highest fracture strength and thermal shock resistance values were achieved for nano-MgO with 2.5 wt% EGS. The resulting refractory samples can be used as furnace linings having a lower carbon content and enhanced thermo-mechanical properties.

Composite Cryogels Based on Hydroxyapatite and Polyvinyl Alcohol and the Study of Physicochemical and Mechanical Properties.

Nowadays, due to the increasing number of diseases and injuries related to bone tissue, there is an acute problem of creating a material that could be incorporated into the bone tissue structure and contribute to accelerated bone regeneration. Such materials can be represented by a polymeric matrix that holds the material in the bone and an inorganic component that can be incorporated into the bone structure and promote accelerated bone regeneration. Therefore, in this work we investigated polyvinyl alcohol-based composite cryogels containing an in situ deposited inorganic filler, hydroxyapatite. The freezing temperature was varied during the synthesis process. The composition of the components was determined by infrared spectroscopy and the phase composition by X-ray phase analysis, from which it was found that the main phase of the composite is hydroxyapatite and that the particle size decreases with increasing freezing temperature. The elemental composition of the surface is dominated by carbon, oxygen, phosphorus and calcium; no impurities of other elements not typical for polyvinyl alcohol/ hydroxyapatite cryogels were found. Higher mechanical properties and melting points were observed at -15 °C. Cryogenic treatment parameters did not affect cell viability; however, cell viability was above 80% in all samples.

Dissolution corrosion of FeCrAl alloy exposed to oxygen-depleted lead–bismuth eutectic containing Ni impurities at 600 ℃

FeCrAl alloy is one of the potential candidates of structural materials due to its high strength, low radiation swelling and good oxidation resistance for the application of lead-cooled fast reactors (LFRs). Particularly, FeCrAl alloy can form protective Al-containing oxide scales after exposure to liquid oxygen-rich Pb and lead–bismuth eutectic (LBE) at 400–800 ℃, showing better performance than traditional commercial stainless steels such as T91, 316L and 15-15Ti. Given the possibility that oxygen in liquid metal could be consumed and not be supplied timely in some quasi-static regions of the actual coolant circuit, to figure out the corrosion behavior of FeCrAl alloy in oxygen-depleted LBE is necessary. In this work, the commercial FeCrAl alloy was exposed to static liquid LBE containing Ni impurities with 10−9 wt% oxygen concentration at 600 ℃ for up to 5000 h, and the surface and cross-sectional morphology of the samples was characterized and analysed. It is found that FeCrAl alloy underwent severe dissolution corrosion, and the maximum penetration depth of LBE reached 161.4 μm after the test for 5000 h; PbBi infiltrated into alloy matrix along the GBs and selectively leached Al from the affected grains. Besides, an interesting discovery is the Cr-rich thin layer at LBE/matrix interface and Ni3Al precipitates in LBE penetration front which should be attributed to the deposition of impurity elements dissolved in liquid LBE during the cooling process.

Selective and efficient extraction of lithium from spodumene via nitric acid pressure leaching

The thriving electric vehicle market has fueled a remarkable surge in the demand for lithium. Consequently, a heightened emphasis has emerged on the extraction of lithium from spodumene deposits. However, the sustainable growth of the lithium industry encounters challenges. The traditional process has the disadvantages of high acid consumption, high extraction rate of impurities and difficult purification of leach liquor. To address these challenges, this study proposes a process for the selective and efficient extraction of lithium from spodumene via nitric acid pressure leaching. In an autoclave at 200 °C, initial nitric acid concentration of 1 mol/L, liquid-to-solid ratio of 2.5 mL/g, and holding time of 30 min, 95 % Li was extracted, with low extraction rate of impurity elements. During pressure leaching, the aluminum–silicate cage structure of β-spodumene remains intact, while H+ freely exchanges with Li+ within the structure, resulting in the formation of HAlSi2O6. Subsequently, the leach liquor underwent thermal decomposition at 250 °C to achieve lithium-aluminum separation. It's noteworthy that nitric acid can be recycled in the process, resulting in low acid consumption. The proposed process has the potential to contribute significantly to the lithium industry by facilitating the adoption of environmentally friendly and sustainable practices.

Unraveling the Nanoscale Segregation Mechanism in N-Doped Niobium for Enhanced SRF Performance.

The nitrogen doping (N-doping) treatment for niobium superconducting radio-frequency (SRF) cavities is one of the key enabling technologies that support the development of more efficient future large accelerators. However, the N-doping results have diverged due to a complex chemical profile under the nitrogen-doped surface. Particularly, under industrial-scale production conditions, it is difficult to understand the underlying mechanism thus hindering performance improvement. Herein, a combination of spatially resolved and surface-sensitive approaches is employed to establish the detailed near-surface phase composition of thermally processed niobium. The results show that intermediate phase segregations, particularly the nanometric carbon-rich phase, can impede the nitridation process and limit the interactions between nitrogen and the niobium sub-surface. In comparison, the removal of the carbon-rich layer at the Nb surface leads to enhanced nitrogen binding at the Nb surface. Combining the RF test results, it is shown that the complex uniformity and grain boundary penetrations of impurity elements have a direct correlation with the mid-field quench behavior in the N-doped Nb cavities. Therefore, proper control of the nanometric intermediate phase formation in discrete thermal steps is critical in improving the ultimate performance and production yield of the Nb cavities.

Enhanced ICP-MS detection of 24 elemental impurities in complex, high matrix mineral, medicinal lanthanum carbonates according to ICH Q2 (R2).

Validation of the specificity of ICP-MS methods by ICH Q2 (R2) through spiking experiments cannot characterize the multi-atomic interference of complex high matrix samples, possibly affecting the accuracy of the method and reliability of results. In this study, we highlight this issue by investigating the elemental impurities in lanthanum carbonate raw materials and use isotope ratio analysis to overcome this limitation and establishing an accurate ICP-MS method for 24 elemental impurities (listed in ICH Q3D). An Agilent 7900 ICP-MS was used with an automatic sampler for sample determination in the He mode. The isotope ratio of elemental impurities in the spiked samples was analyzed to characterize polyatomic interference and select the exclusive mass number of elemental impurities. While the recovery rate of most elemental impurities met the requirements, that of selenium (default measurement mass number 78Se) exceeded the standard in the matric sample. The isotope ratio of Se (78Se/82Se) was much higher than the theoretical value, indicating that the response intensity of m/z 78 was formed by the combination of 78Se and other mass-to-charge ratios, such as LaOH2+ formed by the large amount of La in the matrix. Therefore, 82 was chosen as the mass number for Se. The validation results indicate that the method has strong specificity, high accuracy, and is simple and facile. This study provides technical support for the control of elemental impurities in lanthanum carbonates and isotope ratios can be used as a supplementary means of spiked recovery rates.

A facile synthesis of nano-magnesia by ultrasonication assisted co-precipitation method for antibacterial activity

Magnesium oxide (MgO) nanoparticles found considerable interest from the researcher because of their versatile biocompatible properties and the plethora of applications including anticancer, antimicrobial, antidiabetic, drug delivery, and tissue engineering etc. The growing applications of the MgO nanoparticles necessitate exploring new synthesis routes with faster production rates. Method: In this study, MgO nanoparticles were synthesized by ultrasonication-assisted co-precipitation method and calcined at 800°. MgO nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energydispersive X-ray spectroscopy (EDS) analysis. XRD results showed that the particles have a body-centered cubic (BCC) structure with a crystallite size of about 19.07 nm. SEM results displayed the spherical morphology of MgO nanoparticles. The impurity elements were absent as determined through EDX analysis and showed the high purity of the synthesized MgO. These particles are tested for in-vitro biological applications. The antibacterial activity of MgO nanoparticles on different bacteria was determined by the minimum inhibitory concentration (MIC) test. MIC test revealed that antibacterial activity increases by increasing the concentration of MgO nanoparticles. The synthesized nano-MgO showed high purity and spherical morphology and characterization analysis revealed that nano-MgO and biocompatible and can be applied in biomedical applications as verified by their bacterial activity test.

A new ultrasound-assisted microextraction for elemental impurities determination in tablets by ICP-MS according to USP chapters 232 and 233

Along with the United States Pharmacopeia (USP) chapters 232 and 233 regarding elemental impurities in pharmaceutical products, new challenges have been imposed in terms of sample preparation procedures prior to inductively coupled plasma mass spectrometry analysis, considering the matrix complexities. As so, a new microextraction procedure assisted by ultrasound using a cup-horn sonoreactor, minimal reactants, and sample was proposed and validated according to USP. The procedure was optimized with samples of milled tablets and 3 different acid mixtures (HNO3, 3HNO3:1HCl, and 9HNO3:1HF) and it was compared with microwave-assisted acid digestion. In the validation step, recoveries ranging from 85 to 120 % and RSD below 10 % were obtained for 22 analytes (except Ag and Pt) with satisfactory linearity and good sensitivity. The method was then applied for 37 samples of antidepressants, which presented trace levels of As, Ba, Cd, Co, Cr, Cu, Ni, Pb, Pd, Sn, and V.

Phytoremediation: An Approach for Petrochemical Contaminated Soil of Assam

The presence of a component, impurity, or other unfavourable element that taints, corrupts, infects, renders unfit, or degrades a material, or natural environment is referred to as environmental contamination. Due to the potential negative effects caused by the chemical discharges, environmental issues have now become crucial factors to consider. Petrochemical wastes are one of the most serious environmental contaminants which comprise a large group of chemicals derived from petroleum and natural gases. The petrochemical pollutants, belonging to the groups such as greenhouse gases, volatile organic compounds, Particulate Matter (PM) with heavy metals, and polycyclic aromatic compounds, act as potential soil contaminants, causing disturbance and harm to the soil ecosystem. Phytoremediation is an emerging and eco-friendly way to mitigate petrochemical contamination of soil. It is an in situ technique to purify contaminated soil or water using plants (trees, shrubs, grasses and aquatic plants) and their associated microorganisms. This technique is favourable for tropical countries like India where there is immense growth of plants. Though plants like Mirabilis jalapa, Italian ryegrass, sorghum, maize, and alfalfa are used worldwide, in Assam also various plant species are used for remediation purposes in petrochemical-contaminated soil. Crotalaria pallida, Cyperus brevifolius, Cynodondactylon. Mimosa pudica etc. are some of the plant species that have been reported to possess the ability to degrade toxic chemicals into non-toxic or less-toxic products with the aid of microbial colonies in the soil. This review is an effort to through some light on the plants of Assam as well as worldwide along with their family in the remediation of petroleum-contaminated soil. Thus, it will be helpful to select appropriate plants for the purpose of phytoremediation.

ICP-MS: a tool for detection and quantitation of fosfomycin residues in cleaning samples of finished product by estimation of phosphorous load

The ICP-MS technique is creatively utilized to quantify trace levels of fosfomycin, a non chromophoric and non-mass friendly molecule for cleaning validation samples.

Technological analysis of liquid waste parameters in treatment system for phosphorus production

This study considers the problem of analyzing a complex hierarchical system of phosphorus production wastewater treatment, which is characterized by considering the process of sedimentation of elemental phosphorus sludge particles and mechanical impurities. The study presents a framework for decision-making on the purification of wastewater from phosphorus production, which is contaminated with toxic impurities and must meet sanitary norms. The framework considers the reagents introduced, as well as the increased mineralization of water, which cannot be discharged into the water body for ecological reasons. Instead, it is reused in production. It is demonstrated that for mechanical treatment of sewage from elemental phosphorus and suspended solids, as well as to improve sedimentation of particles, iron sulphate is used as a coagulant. The action of this coagulant is similar to that of sulphuric acid aluminum, which is widely used for water treatment. Thus, a complex engineering approach is presented for a complex system of phosphorus production wastewater treatment.

Study on the behavior of impurity removal from lithium-iron-phosphate slag using the ultrasonic-assisted sulphuric acid leaching

The recovery of iron phosphate from the leaching slag of used lithium iron phosphate cathode materials is a crucial step to achieve closed-loop recovery of lithium iron phosphate, which has not yet been effectively accomplished. In the study, ultrasonic-assisted sulfuric acid leaching was used to remove impurities in the iron phosphate, to meet the stringent impurity content requirements for battery-grade iron phosphate regarding impurity content. Optimization of leaching conditions involved a sulfuric acid concentration of 0.2 mol?L-1, acid-leaching time of 30 min, power of 50 W, and reaction temperature of 80?. Under these conditions, the removal efficiencies of Cr, Cu, Ni, and Zn in iron phosphate were 26.09%, 83.0%, 75.9%, and 96.3%, respectively. Simultaneously, the content of impurity elements Cr and Zn concurred with the standard for battery-grade iron phosphate (HG/T 4701-2021), with both 50 ppm and 10 ppm contents. The leaching results indicated the effectiveness of ultrasound in enhancing the removal of impurity elements in iron phosphate within a sulfuric acid solution. Further analyses, including XRD, particle size, TEM, and XPS indicated that the surface of the iron phosphate particles cavitated after ultrasonic acid leaching, resulting in the formation of numerous pores. Additionally, particle collisions led to a reduction in particle size, with no generation of by-products during the process. This innovative approach not only contributed to the removal of impurity elements but also provided insights into the reuse of leaching slag (iron phosphate) and offered guidance for the recovery of metals from waste lithium iron phosphate cathode materials.

Growth and surface structrue of hydrogen terminal diamond thin films

The conductivity of hydrogen-terminated diamond is a limiting factor in its application in field-effect transistor devices. The traditional preparation process hinders the improvement of the electrical properties of hydrogen-terminated diamond due to impurity elements in the diamond bulk and surface damage caused by processing near the diamond surface. To overcome this, researchers have explored the epitaxial growth of a high-purity and flat-surfaced diamond thin film on a diamond substrate. However, this approach still faces challenges in film characterization and achieving high surface smoothness. In this study, microwave plasma chemical vapor deposition technology is used to epitaxially grow a sub-micron thick diamond film on a nitrogen-doping chemical vapor deposition diamond substrate of 10 mm × 10 mm × 0.5 mm in size. The influence of methane concentration on the growth and conductivity of diamond film is investigated. The test results reveal that the growth thickness of the diamond film ranges from 230 to 810 nm, and the nitrogen concentration in the epitaxial layer is lower than 1×10<sup>16</sup> atom/cm<sup>3</sup>. Three growth modes are observed for the homoepitaxial growth of the diamond thin film under different methane concentrations. A methane concentration of 4% enables two-dimensional planar growth of diamond, resulting in a smooth and flat surface with a roughness of 0.225 nm (10 μm×10 μm). The formation of different surface morphologies is attributed to the growing process and etching process of diamond. Surface low-energy electron diffraction testing indicates that the surface of the diamond film undergoes a structural transition from oxygen terminal (1×1: O) to hydrogen terminal (2×1: H) when grown for a short period of time. X-ray photoelectron spectroscopy analysis reveals an extremely low ratio of oxygen element to nitrogen element, giving the grown diamond film P-type conductivity characteristics. The Hall test results demonstrate that the hydrogen-terminated diamond film grown with a methane concentration of 4% exhibits the highest conductivity, with a square resistance of 4981 Ω/square and a hole mobility of 207 cm<sup>2</sup>/(V·s). This enhanced conductivity can be attributed to the lower defect density observed under these specific conditions. The findings of this study effectively improve the electrical properties of hydrogen-terminated diamond, and contribute to the development and practical application of high-power diamond devices.

Flue Dust Behaviour in FSF - Arsenic Condensation in Offgas Line Conditions

The suspension smelting oxidation step has favourable conditions to generate chemical flue dust from the low-boiling elements of the feed mixture due to the high particle temperatures in the reaction shaft where combusting sulphide mineral particles reach temperatures above the melting point of magnetite. Arsenic, antimony, lead, and zinc are common impurity elements of high volatility in copper concentrates. They tend to accumulate in the flue dust due to the high volatility and closed mode of the flue dust circulation practiced in most industrial smelting-converting processes. Then, the only outlets for the volatile impurities are the anodes and the discard slag. A separate flue dust treatment for impurity removal is an option but it creates an additional step for the smelting plant and cost in the processing. When the concentrate grades decrease, and their impurity levels rise this outlet for the trace elements may become necessary. The arsenic condensation mechanisms in dust-free conditions in the copper flash smelting process gas train have been recently studied in SO2-air-N2 gas mixtures. It seems that the formation mechanism of arsenic-containing dust deposits is kinetically constrained, and their chemistries are influenced by the condensation temperature and atmosphere.

The Elemental Composition of Hemp Flower: Sources of Elemental Impurities and Implications for Consumer Product Safety

The Elemental Composition of Hemp Flower: Sources of Elemental Impurities and Implications for Consumer Product Safety

Regulation Law of Tempering Cooling Rate on Toughness of Medium-Carbon Medium-Alloy Steel.

Temper embrittlement is a major challenge encountered during the heat treatment of high-performance steels for large forgings. This study investigates the microstructural evolution and mechanical properties of Cr-Ni-Mo-V thick-walled steel, designed for large forgings with a tensile strength of 1500 MPa, under different tempering cooling rates. Optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) were employed to analyze the microstructural features. The results demonstrate that the embrittlement occurring during air cooling after tempering is attributed to the concentration of impurities near Fe3C at the grain boundaries. The low-temperature impact toughness at -40 °C after water quenching reaches 29 J due to the accelerated cooling rate during tempering, which slows down the diffusion of impurity elements towards the grain boundaries, resulting in a reduced concentration and dislocation density and an increased stability of the grain boundaries, thereby enhancing toughness. The bainite content decreases and the interface between martensite and bainite undergoes changes after water quenching during tempering. These alterations influence the crack propagation direction within the two-phase microstructure, further modifying the toughness. These findings contribute to the understanding of temper embrittlement and provide valuable guidance for optimizing heat treatment processes to enhance the performance of high-performance steels in large forgings.

Direct recycling industrialization of Li-ion batteries: The pre-processing barricade

The substantial amount of retiring Li-ion batteries (LIBs) is a reason for environmental concern but also an economic opportunity. Extracted materials by recycling these batteries can potentially help coping with the rising demand and supply chain issues. Direct recycling is the most effective and economic way to reinsert the valuable cathode into cell manufacturing. Feedstock retrieval for direct recycling from the end-of-life (EoL) LIBs will be critical to validate scaling. Pre-processing constitutes the initial stage of safe and efficient handling of LIBs in the pursuit of feedstock retrieval. Here we have discussed the pre-processing steps for cathode black mass (CBM) extraction from EoL LIBs suitable for direct recycling feedstock. Pre-processing steps and their relevance to avoid impurities originating from cell components while maintaining active material features has been reviewed. We have attempted to understand the impact of impurity elements, such as Al, Cu, F, and C, on the active material direct regeneration from existing literature. Reviewing current state of the art for the pre-processing and direct recycling technologies, we have estimated the prospects remaining in active material revitalization and technical barricades to its remunerative scalability.

FEATURES OF THE RELATIONSHIP OF GERMANIUM CONTENT WITH THE CONCENTRATIONS OF TOXIC ELEMENTS AND THEIR DISTRIBUTION IN THE COAL SEAM С5 OF THE BLAGODATNA MINE

Problem Statement and Purpose. The purpose of this publication is to establish the character and level of the statistical relationship between the concentrations of germanium and toxic elements in coal seam c5 of the “Blagodatna” mine and the main features of their distribution for the assessment of possible environmental risks during the selective processing of coal enriched with this element. Coal is the main source of germanium. The study of the content of this element in coal seams acquires considerable importance due to its potential for industrial extraction and application as a valuable accompanying resource. Forecasts by the US Geological Survey point to an increase in global demand for germanium, with production expected to grow nearly 1.5 times by 2030. Data & Methods. The factual basis of the work was the results of data analyzes of 58 analyzes of the elements Ge, Be, F, Hg and As, conducted after 1981 in accredited state laboratories. In some cases, the data was supplemented with the results obtained by the furrow method of sampling from the core and mine workings, which was carried out from 1981 to 2018. At the beginning of the study, primary geochemical data were processed using STATISTICA 13.3 and IBM SPSS Statistics 22 to calculate basic statistical characteristics. Construction of frequency histograms for germanium content and reservoir thickness was also performed, as well as determination of their distribution characteristics. To achieve the research objectives, correlation and regression analyzes were performed using methods available in Micromine, one of the leading professional mining and geological information systems for 3D modeling, statistical data processing and mining planning (license MM5123). Results. The character and level of the statistical relationship between the content of germanium and “toxic elements” in coal seam c5 of the “Blagodatna” mine and the main features of their distribution were established for the assessment of possible environmental risks during the selective processing of coal enriched with this element. It has been proven that the correlation between germanium and all “toxic” elements is inverse and very weak. The existence of genetically different forms of germanium and arsenic, fluorine, mercury and beryllium was revealed. A general feature of the distribution of Ge, As, F, Hg, and Be in the coal seam is noncompliance with normal and lognormal laws and polymodality of the distributions with a shift of the density cores to the left. The diverse probable form of finding the considered impurity elements in general in coal allows to treat the regularities established with the help of regression and correlation analysis only as a kind of trend of dependencies between them.