Clean Metal Research Articles

Bioremediation of wastewater containing mercury using three newly isolated bacterial strains

To successfully clean and recycle heavy metal–contaminated wastewater, we developed a fast, simple, low-cost, and efficient bioremediation method to eliminate mercury (Hg) pollution. We isolated three bacterial strains with strong Hg tolerance and reduction capacities from the polluted waters of the Yellow River. These bacterial strains mainly reduced Hg2+ by the mer operon. The bacterial strains had the best treatment effect on Hg-contaminated wastewater when mixed in equal proportions. Under the optimum growth conditions of the bacterial strains, it would take about 60 L of the three strains in the same proportion in a cultured solution to treat 1 ton of wastewater containing 10 mg/L Hg2+. After 48 h of treatment, the concentration of Hg2+ in the wastewater could reach the national standard (Hg2+ ≤0.05 mg/L). The bacterial strains also exhibited tolerance and transformational abilities for Pb2+, Cr6+, As5+, and Cd2+, indicating that these bacteria could be utilized in more complex heavy metal–polluted environments. This work revealed a new method for the bioremediation of heavy metal–polluted wastewater.

Analysis of Wafer Cleaning Solution Characteristics and Metal Dissolution Behavior according to the Addition of Chelating Agent

Analysis of Wafer Cleaning Solution Characteristics and Metal Dissolution Behavior according to the Addition of Chelating Agent

Effect of oil price uncertainty on clean energy metal stocks in China: Evidence from a nonparametric causality-in-quantiles approach

Using the nonparametric causality-in-quantiles approach, we investigate the causal effects of oil price uncertainty on the returns and volatility of clean energy metal stocks under different market conditions in China. The results suggest that there is a causal relationship between oil price uncertainty and the returns and volatility of Chinese clean energy metal stocks. The effect differs slightly between returns and volatility. Specifically, the causal effect of oil price uncertainty on returns is mainly observed for lower quantiles, whereas the effect on volatility exists for all quantiles. In addition, the effects of change of market environment in China on the causal relationship are tested. The results show that change in market environment has significantly weakened the causal relationship between oil price uncertainty and clean energy metal stocks, suggesting that the structure of the Chinese clean energy metal stock market has undergone major changes.

High-Quality Hexagonal Boron Nitride from 2D Distillation.

The production of high-quality two-dimensional (2D) materials is essential for the ultimate performance of single layers and their hybrids. Hexagonal boron nitride (h-BN) is foreseen to become the key 2D hybrid and packaging material since it is insulating, impermeable, flat, transparent, and chemically inert, though it is difficult to attain in ultimate quality. Here, a scheme is reported for producing single layer h-BN that shows higher quality in view of mosaicity and strain variations than material from chemical vapor deposition (CVD). We delaminate CVD h-BN from Rh(111) and transfer it to a clean metal surface. The twisting angle between BN and the second substrate yields metastable moiré structures. Annealing above 1000 K leads to 2D distillation, i.e., catalyst-assisted BN sublimation from the edges of the transferred layer and subsequent condensation into superior quality h-BN. This provides a way for 2D material production remote from CVD instrumentation.

Technology of laser cleaning of steel structures

Cleaning metal surfaces from oxide films, corrosion products, scale and other contaminants to obtain the required quality is one of the basic technologies in many industries. There are traditional methods of cleaning, which in the process of their evolutionary development and improvement have approached the potential technological frontier and do not fully meet the ever-growing demands of the industry. An alternative method is laser cleaning. Goal. The aim is development of modes for laser cleaning of steel structures from rust and technological contamination, which can be used both in stationary and field conditions. Method. To clean the steel structures, we used an installation based on a pulse-periodic CO2 laser with a power of 130 W. To assess the quality of the surface layer, the microhardness method and roughness measurement were used. Results. Under the action of laser radiation on the oxidized surface, reactions of reduction of oxides and evaporation of paint and varnish contaminants occur. The influence of the radiation power and the number of passes during cleaning on the surface quality, which was evaluated by the degree of metallization and roughness, was investigated. Scientific novelty. It was determined that the position of the focal plane above the surface and on the surface is the optimal position of the laser radiation for cleaning. It was found that the microhardness of the surface layer of steel after normalization and after metallization of the surface in the process of laser cleaning is practically the same. It is shown that preliminary wetting of the surface during cleaning from rust using a CO2 laser is not advisable. Water vapor is especially strong in absorbing waves in the infrared range, and carbon dioxide is an intense absorber in the mid-infrared range. Practical significance. Recommendations have been developed for the use of a repetitively pulsed CO2 laser for cleaning the steel structures of bridges, power lines, towers of television and mobile transmitters from rust and technological contamination in field conditions.

The Zeeman, spin-orbit, and quantum spin Hall interactions in anisotropic and low-dimensional conductors

To construct a microscopic theory of electrons and holes in anisotropic conductors that self-consistently treats their band effective mass anisotropy with their interactions with applied electric and magnetic fields, the Dirac equation is extended for an electron or hole in an orthorhombically-anisotropic conduction band. Its covariance is established both by a modified version of the Klemm–Clem transformations to a space in which it is isotropic, and also in its fully anisotropic form by making the most general proper and improper Lorentz transformations, proving its validity in both the relativistic and non-relativistic limits. The appropriate Foldy–Wouthuysen transformations are extended to expand about the non-relativistic Hamiltonian limit to fourth order in the inverse of the particle’s Einstein rest energy. The results have important consequences for magnetic measurements of many classes of clean anisotropic semiconductors, metals, and superconductors. In all of these cases, the Zeeman interaction is found to depend strongly upon the effective mass anisotropy. When an electron or hole is traveling in an atomically thin one-dimensional conduction band, its Zeeman, spin–orbit, and quantum spin Hall interactions are vanishingly small. Accurate expressions for the Zeeman, spin–orbit and quantum spin Hall interactions for two-dimensional conductors are provided.

Creation of aerosolized detergent compositions for cleaning high-precision metal mirrors

We report on a studies on the possibility of extending the service life of products of non-ferrous metals by physical and chemical treatments with specially created azeotropic compositions. These studies were carried out on high-precision copper mirrors for high-power CO2 lasers, exposed during operation to different climatic influences, worsening of their operational characteristics. The results obtained in this paper can be applicable for physical and chemical cleaning of such mirrors and other high-precision parts from non-ferrous metals. The work is devoted to the creation of aerosol detergent compositions intended for use during the operation of mirrors in the field climatic conditions. It is shown that when aluminium and tin-plate aerosol containers are used, compositions that are used to clean metal mirrors should not contain chlorine-substituted hydrocarbons or even “traces” of water and hydroxyl ions. In addition to copper mirrors, optical elements made of other materials were also studied in this work.

Facile and low-cost green synthesis of eco-friendly chitosan-silver nanocomposite as novel and promising corrosion inhibitor for mild steel in chilled water circuits

New promising samples of silver nanoparticles: (SNPs)-chitosan (CT) nanocomposite (NC) abbreviated as (SNPs-CTNC) have been synthesized and characterized using the novel green chemistry approach. All the synthesized formulations showed innovative corrosion inhibition for the mild steel samples in the cooling water system. The experimental conditions for the green synthesis of eco-friendly silver nanoparticles (SNPs) using chitosan (CT) biopolymer as both reducing and protecting coating agent for SNPs have been optimized. The synthesis route presented herein was performed by the reduction of silver nitrate (AgNO3) by CT in an autoclave reactor vessel under 1 bar applied pressure at the reaction temperature of 120 °C and various contact time (2, 4, 8, and 16 h) between (AgNO3) and chitosan (CT). The four prepared samples of SNPs-CT NC have been abbreviated in terms of the reaction or the contact time as (2 h, 4 h, 8 h, and 16 h). The four SNPs-CT NC samples were characterized using: UV–Visible spectroscopy; Fourier transform infrared (FTIR); X-ray diffraction (XRD) and transmission electron microscopy (TEM). The SNPs coated by chitosan biopolymer showed good antimicrobial activity, and have extremely fine particle size approaching that of the quantum dots nanoparticles. The particle size distribution of all the prepared nanocomposite samples lies around the nanometer scale range of 3–6 nm. The corrosion rate of the standard corrosion coupons of mild steel in the industrial chilled water in the absence and the presence of different concentrations of SNPs-CTNC samples were measured by the gravimetric method as well as the electrochemical impedance spectroscopy (EIS) and DC-potentiodynamic polarization techniques. The inhibition efficiency (%IE) of SNPs-CTNC achieved up to 97–98% at the concentration of 150 ppm SNPs-CTNC of all the prepared samples (from chemical gravimetric weight loss results). The inhibition efficiency (%IE) of the best performance SNPs-CTNC sample (8 h) showed inhibition efficiency above 80% at 100 ppm (as evident by the further electrochemical techniques: impedance and potentiodynamic polarization results). Both the inhibition efficiency and the antimicrobial activity of SNPs-CT NC samples remained unchanged on aging for twelve months storage where: The percent inhibition efficiency of all SNPs-CTNC samples remain above the percentage of 93% on aging for this relatively long storage time period, the sample 2 h showed the most constant inhibition efficiency (97.6% for the fresh prepared sample and 97.5% for the twelve months aged sample). In addition, the scanning electron (SEM) micrographs have been showed that: A clean and bright metal surface was maintained after the exposure to the chilled water in the presence of SNPs-CTNC along the immersion time of one year. The nanocomposite samples acted by spontaneous physisorption on the metal surface as indicated by the negative value of ΔG°adsorption (equals −18.002 kJ·mol−1). The adsorption data represented in the surface coverage (θ) were found to be linearly fitted well to Langmuir adsorption isotherm with positive and relatively large value of the binding equilibrium constant (K) (43.6) that represented the strong attraction forces between the adsorbed nanocomposite particles and the metal surface. The mode of the adsorption of these nanocomposite particles on the metal surface has been interpreted in terms of the electrostatic interaction between the negatively charged colloidal SNPs and the positively the charged metal surface.

A comparative study on coated carbide inserts performance in cryogenic end milling of AISI D2 tool steel

Cryogenic metal removal with the help of liquid nitrogen will be a clean substitute for our conventional flood cooling due to environmental regulations in the machining industries. The present work experiments the efficiency of TiN as well as TiAlN layered insert of carbide in the process of milling which takes place at the end in AISI D2 steel. The performance caused by cryogenic machining for the finishing on the surface and tear and wear of the tool are studied, the results are estimated with dry and existing flood coolant metal removing process at different cutting speeds. When estimated with TiN layered inserts, inserts of TiAlN shower maximized life of the tool and maximized finishing in the surface during metal removing process at several speeds behind their spindle, more than that they are environmentally clean metal removing process. We are going to discuss the significance of the cryogenic metal removal process which provides its importance for increased efficiency of machined components through its better penetration of lubrication in the tool and workpiece interface.

Scanning tunneling microscopy and spectroscopy of rubrene on clean and graphene-covered metal surfaces.

Rubrene (C42H28) was adsorbed with submonolayer coverage on Pt(111), Au(111), and graphene-covered Pt(111). Adsorption phases and vibronic properties of C42H28 consistently reflect the progressive reduction of the molecule–substrate hybridization. Separate C42H28 clusters are observed on Pt(111) as well as broad molecular resonances. On Au(111) and graphene-covered Pt(111) compact molecular islands with similar unit cells of the superstructure characterize the adsorption phase. The highest occupied molecular orbital of C42H28 on Au(111) exhibits weak vibronic progression while unoccupied molecular resonances appear with a broad line shape. In contrast, vibronic subbands are present for both frontier orbitals of C42H28 on graphene. They are due to different molecular vibrational quanta with distinct Huang–Rhys factors.

Design of an Accurate Machine Learning Algorithm to Predict the Binding Energies of Several Adsorbates on Multiple Sites of Metal Surfaces

AbstractIn the current work, we design a single unique machine learning (ML) algorithm capable of predicting the binding energies of several C, N and O‐based adsorbates and atomic hydrogen on different facets (100, 111, 211) of eleven transition‐metals considering an FCC bulk structure (Co, Rh, Ir, Ni, Pd, Pt, Ru, Os, Cu, Ag, Au) with high accuracy with respect to the reference DFT calculations. The selected properties/features are based on already available data or electronic properties easily obtained from DFT calculations of the free adsorbates and on the clean metal surfaces. The mean average error (MAE) for the training set is equal to 0.074 eV, while for the test set (data not used in training) is equal to 0.174 eV, thus having a very small error with respect to the reference DFT calculations. Further modifications of the present algorithm, which is based on an Extragradient boost (XGBoost) regressor in combination with a tree booster, with the addition of few more features might set the ground to develop ML algorithms able to predict the binding energies of adsorbates on more complex catalytic surfaces.

Elimination of Metal Fencing by Optimizing Evaporator Dome Alignment

Successful metal liftoff requires a retrograde photoresist profile, or one created using a bi-layer process. Coupled with an evaporator setup for liftoff deposition, these ensure a discontinuity in metal coverage so that the unwanted field metal can be lifted off cleanly, without tearing or defects. An evaporator with an optimized liftoff configuration necessitates precise source-to-substrate alignment or defects will result. While a lot of development work has been reported on photoresist processes and liftoff techniques, a lack of publication on ideal evaporator geometry and proper setup suggests that the effects of source to substrate alignment have seldom been investigated or discussed. An evaporant flux with precise normality is essential to achieving clean metal liftoff. This paper examines how evaporator geometry influences the liftoff process. We will reveal the working principle of a special alignment tool and how the tool is used to keep the evaporator in precise alignment

Variable VOCs in plastic culture flasks and their potential impact on cell volatile biomarkers.

In order to find out cancer markers in human breath, in vitro cell culture is often used to study the characteristic volatile organic compounds (VOCs). In the cell culture process, disposable vessels are frequently adopted. However, these vessels are normally made of plastic, and they have the possibility to release some VOCs, which may interfere with the cell-specific volatiles and even can result in an incorrect conclusion. In this study, by using glass cell culture flasks as control, the headspace solid-phase microextraction gas chromatography mass spectrometry (HS-SPME-GC-MS) analyses of the VOCs in plastic cell culture flasks were systematically carried out for the first time. A total of 35 VOCs were detected in five brands of flasks. In each flask, there were between 13 and 25 volatile compounds. Furthermore, the components and packaging bag of each flask were also sampled and analyzed by HS-SPME-GC-MS. The results show that the flask cap, septum, flask body, and packaging bag exhibit respectively different volatile behaviors. The former two parts release the most volatiles which have obvious contributions to the headspace gases in the flasks, while the flask body mainly liberates styrene. For different flasks packed within the same bag, the headspace analyses show that their residual VOCs are inconsistent with each other. Moreover, the residual VOCs in the same flask are variable in three consecutive days. These results indicate that the multiple flasks in parallel cell culture experiments, or the same flask with different cell culture durations, will produce an indelible disturbance to the cell-specific VOCs. In addition, among the 35 VOCs detectable in five brands of empty plastic flasks, 15 VOCs were previously reported as characteristic VOCs from lung cancer, melanoma, cervical cancer cells, or normal cells. This is an alert that, when using plastic flasks, it must be careful to treat the possible interference from the background VOCs in the flasks. This study demonstrates that the cell culture tool needs to be standardized, and the clean glass or metal vessels are strongly recommended for usage when studying cell volatile biomarkers. Graphical abstract.

The impact of oil price on the clean energy metal prices: A multi-scale perspective

To examine the spillover effects of crude oil price and clean energy metal prices, we first explore the Granger causality between crude oil and clean energy metals prices. Then, we decompose crude oil price returns into a high frequency sequence (Oil_HF), a low frequency sequence (Oil_LF), and a trend residual (Oil_res) using the ensemble empirical mode decomposition model. Lastly, a VAR model is used to study the spillover effects of crude oil price on seven types of clean energy metal prices. The results show that crude oil price has non-linear Granger causality with lithium, cobalt, manganese, antimony, cadmium, molybdenum, and tellurium. And crude oil price has a significant positive spillover effect on seven types of clean energy metals at different time scales. Specifically, the crude oil original sequence, Oil_HF, Oil_LF, and Oil_res all have fluctuation effects on the cobalt and molybdenum markets. The spillover effects of the crude oil market on the lithium, manganese, antimony, and cadmium markets are caused by the low frequency sequence. The trend in crude oil price returns has a great effect on tellurium price, while the spillover effects of crude oil price, Oil_HF, and Oil_LF on tellurium are weak positive.

Preliminary study on Cd accumulation characteristics in Sansevieria trifasciata Prain

Phytoremediation techniques to clean heavy metal pollution soil depend on identifying plant species that can act as phytoremediators. One important approach to screening potential phytoremediators is to evaluate characteristics of heavy metal accumulation. In this study, we performed firsthand analysis of Cd tolerance and accumulation characteristics of three Sansevieria trifasciata cultivars by pot experiment. Plant growth results showed that all three S. trifasciata cultivars can tolerate 50 mg kg−1 soil Cd concentration. After growth under 50 mg kg−1 soil Cd concentration for 4 months, the Cd bioconcentration factors in the shoots of S. ‘Trifasciata’, S. trifasciata ‘Laurentii’, and S. trifasciata ‘Silver Hahnii’ were 1.26, 1.30, and 1.19, while those in the roots were 12.53, 11.43, and 5.45, respectively. This result reveals the considerably low translocation factors of 0.10, 0.12, and 0.22 for S. ‘Trifasciata’, S. trifasciata ‘Laurentii’, and S. trifasciata ‘Silver Hahnii’, respectively. These results suggest that all three S. trifasciata cultivars had high Cd absorption capacities but low Cd translocation capacities. In combination with total Cd accumulation distribution and plant growth characteristics, S. trifasciata can be designed as a phytostabilizer in Cd-contaminated soils in its cultivation regions. Meanwhile, the mechanism of high Cd tolerance and accumulation characteristics in the roots of S. trifasciata should be explored. This study provides new resources for dealing with Cd-contaminated soils and exploring Cd tolerance and accumulation mechanisms in plants.

On‐Surface Synthesis of Cumulene‐Containing Polymers via Two‐Step Dehalogenative Homocoupling of Dibromomethylene‐Functionalized Tribenzoazulene

AbstractCumulene compounds are notoriously difficult to prepare and study because their reactivity increases dramatically with the increasing number of consecutive double bonds. In this respect, the emerging field of on‐surface synthesis provides exceptional opportunities because it relies on reactions on clean metal substrates under well‐controlled ultrahigh‐vacuum conditions. Here we report the on‐surface synthesis of a polymer linked by cumulene‐like bonds on a Au(111) surface via sequential thermally activated dehalogenative C−C coupling of a tribenzoazulene precursor equipped with two dibromomethylene groups. The structure and electronic properties of the resulting polymer with cumulene‐like pentagon–pentagon and heptagon–heptagon connections have been investigated by means of scanning probe microscopy and spectroscopy methods and X‐ray photoelectron spectroscopy, complemented by density functional theory calculations. Our results provide perspectives for the on‐surface synthesis of cumulene‐containing compounds, as well as protocols relevant to the stepwise fabrication of carbon–carbon bonds on surfaces.

On-Surface Synthesis of Cumulene-Containing Polymers via Two-Step Dehalogenative Homocoupling of Dibromomethylene-Functionalized Tribenzoazulene.

Cumulene compounds are notoriously difficult to prepare and study because their reactivity increases dramatically with the increasing number of consecutive double bonds. In this respect, the emerging field of on‐surface synthesis provides exceptional opportunities because it relies on reactions on clean metal substrates under well‐controlled ultrahigh‐vacuum conditions. Here we report the on‐surface synthesis of a polymer linked by cumulene‐like bonds on a Au(111) surface via sequential thermally activated dehalogenative C−C coupling of a tribenzoazulene precursor equipped with two dibromomethylene groups. The structure and electronic properties of the resulting polymer with cumulene‐like pentagon–pentagon and heptagon–heptagon connections have been investigated by means of scanning probe microscopy and spectroscopy methods and X‐ray photoelectron spectroscopy, complemented by density functional theory calculations. Our results provide perspectives for the on‐surface synthesis of cumulene‐containing compounds, as well as protocols relevant to the stepwise fabrication of carbon–carbon bonds on surfaces.

Structural Phase Transitions of Molecular Self-Assembly Driven by Nonbonded Metal Adatoms.

The involvement of metal atoms in molecular assemblies has enriched the structural and functional diversity of two-dimensional supramolecular networks, where metal atoms are incorporated into the architecture via coordination or ionic bonding. Here we present a temperature-variable study of the self-assembly of the 1,3,5-tribromobenzene (TriBB) molecule on Cu(111) that reveals the involvement of nonbonded adatoms in the molecular matrix. By means of scanning tunneling microscopy and noncontact atomic force microscopy, we demonstrate the molecular-level details of a phase transition of TriBB assembly from the close-packed to porous honeycomb structures at 78 K. This is an unexpected transformation because the close-packed phase is thermodynamically favored in view of its higher molecular density and more intermolecular bonds as compared to the honeycomb lattice. A comprehensive density functional theory calculation suggests that Cu adatoms should be involved in the formation of the honeycomb network, where the Cu adatoms help stabilize the molecular assembly via enhanced van der Waals interactions between TriBB molecules and the underlying substrate. Both calculation and experimental results suggest no chemical bonding or direct charge transfer between the adatoms and the molecules, thus the electronic characteristics of the Cu adatoms trapped in the molecular confinement are close to the intrinsic ones on a clean metal surface and different from those in the traditional coordination-bonded framework. The nonbonded metal adatoms embedded self-assemblies may complement the metal-organic coordination system and can be used to tailor the chemical reactivity and electronic properties of supramolecular structures.

An overview of solar decarbonization processes, reacting oxide materials, and thermochemical reactors for hydrogen and syngas production

Solar decarbonization processes are related to the different thermochemical conversion pathways of hydrocarbon feedstocks for solar fuels production using concentrated solar energy as the external source of high-temperature process heat. The main investigated routes aim to convert gaseous and solid feedstocks (methane, coal, biomass …) into hydrogen and syngas via solar cracking/pyrolysis, reforming/gasification, and two-step chemical looping processes using metal oxides as oxygen carriers, further associated with thermochemical H2O/CO2 splitting cycles. They can also be combined with metallurgical processes for production of energy-intensive metals via solar carbothermal reduction of metal oxides. Syngas can be further converted to liquid fuels while the produced metals can be used as energy storage media or commodities. Overall, such solar-driven processes allow for improvements of conversion yields, elimination of fossil fuel or partial feedstock combustion as heat source and associated CO2 emissions, and storage of intermittent solar energy in storable and dispatchable chemical fuels, thereby outperforming the conventional processes. The different solar thermochemical pathways for hydrogen and syngas production from gaseous and solid carbonaceous feedstocks are presented, along with their possible combination with chemical looping or metallurgical processes. The considered routes encompass the cracking/pyrolysis (producing solid carbon and hydrogen) and the reforming/gasification (producing syngas). They are further extended to chemical looping processes involving redox materials as well as metallurgical processes when metal production is targeted. This review provides a broad overview of the solar decarbonization pathways based on solid or gaseous hydrocarbons for their conversion into clean hydrogen, syngas or metals. The involved metal oxides and oxygen carrier materials as well as the solar reactors developed to operate each decarbonization route are further described.

Work Function Evolution in Li Anode Processing

AbstractToward improved understanding and control of the interactions of Li metal anodes with their processing environments, a combined X‐ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and density functional theory (DFT) characterization of the effects that O2, CO2, and N2, the main gases in dry‐atmosphere battery production lines, induced on a reproducibly clean Li surface at room temperature is presented here. XPS measurements demonstrate that O2 is ten times more effective than CO2 at oxidizing metal Li. Notably, pure N2 is shown to not dissociate on clean metal Li. UPS results indicate that decomposition of O2 (CO2) reduces the work function of the Li surface by almost 1 eV, therefore increasing the reduction energy drive for the treated substrate by comparison to bare metallic Li. DFT simulations semiquantitatively account for these results on the basis of the effects of dissociative gas adsorption on the surface dipole density of the Li surface.