Renewable Surface Research Articles

Acoustic Levitation-Controlled Droplets for Contactless Enrichment and Sensitive Detection of Volatile Organic Substances Integrated with GC-MS.

Analyzing trace-level volatile organic compounds (VOCs) remains challenging due to initial sampling and preconcentration limitations. Inspired by the highly reproducible and constantly renewable electrode surface of dropping mercury electrode (DME), a contactless enrichment process was first reported by using an acoustic levitation device to trap and concentrate VOCs from gas samples onto suspended droplets, which were then directly transferred into gas chromatography-mass spectrometry (GC-MS) for real-time analysis. Compared with traditional methods injection methods, this method achieves a 46-fold increase in nicotine peak area. The detection sensitivity was enhanced significantly, attributed to the high specific surface area of the droplets and the accelerating extraction vibration. Notably, the number of identified VOCs from burning cigarettes significantly increased from 17 to 212, including 22 aromatic compounds with distinct aromas. The remarkable versatility of this method was demonstrated by effectively monitoring the dynamic changes of 16 VOCs in environmental tobacco smoke (ETS) following cigarette burning, revealing the persistence of these compounds, even after 40 min. Moreover, directly analyzing human-exhaled aerosol found that nicotine rapidly decreased while its metabolite cotinine increased, showcasing the potential for tracking human metabolism and behavior in vivo. Furthermore, multivariate data analysis of VOC profiles from six cigarette brands allowed for their visual differentiation. With versatility, sensitivity, and the ability to distinguish trace-level VOCs in realtime, this method offers promising avenues for environmental monitoring, metabolic studies, and various analytical applications.

Study on Desulfovibrio desulfuricans mediated copper corrosion and its inhibition using bio-wax of Colocasia esculenta

In the present study, the bio-wax was extracted from Colocasia esculenta and was tested for its corrosion inhibiting property against Desulfovibrio desulfuricans. Inhibition of copper corrosion by bio wax from Colocasia was observed using weight loss method, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Results obtained from the weight loss studies and impedance measurements provided similar trends of inhibition efficiency. Cu coupon coated with bio-wax showed significant reduction in corrosion rate i.e. Rcorr of 0.0011mmpy. This result gives an idea about the protective nature of thick bio-wax coated copper coupons from bacterial adherence and bacterial metabolites. The impedance value in the bio wax coated coupon was found to be from 188.67 to 781.25 ohms at 1 Volt. The wax FTIR analysis in a spectral region of 4000 cm- 1 - 400 cm -1 showed peaks at 2918.75 cm -1 and 2849.73 cm -1 confirming the presence of hydrophobic hydrocarbon. Morphological changes were observed after coating the bio wax as shown from SEM analysis. The incorporation of the hydrophobic property of bio-wax showed sufficient reduction in MIC of copper. Bio-wax acted as a protective covering inhibiting the adherence of corroding bacteria on the surface. Inhibition efficiency results are in good agreement to use Colocasia bio wax as a source of sustainable and renewable surface coating material. This property might be used in future as an ingredient in anti-rust paint used in coating metal surfaces like ship parts, pipelines systems of petroleum industry and other metal made machines etc.

Mechanical stirring: Novel engineering approach for in situ spectroscopic analysis of melt at high temperature

This paper proposes a novel engineering approach to control molten metals at high temperatures considering the industrial environment of such materials. To reduce analysis time and cost, in-line analysis techniques are more advantageous as they provide real-time information about melt composition. For this reason, recent research works focus on the development of new devices based on LIBS (Laser Induced Breakdown Spectroscopy). These devices allowed for analyzing impurities inside molten metals with great performance. However, improvements related to the immersion probe conception are still required. Indeed, the previous design used bubbling inside the melt, leading to spatial instabilities of the surface analyzed by LIBS. The solution presented here is mechanical stirring by innovative rotary blades which will be a part of an immersion LIBS probe. Their rotation will generate a representative, renewed, and stable surface that will be targeted by spectroscopic techniques in general and particularly by LIBS laser for molten metal monitoring at high temperatures. This solution was validated using experimental tests based on particle imaging velocimetry (PIV) in water at room temperature and then applied to silicon melt at high temperatures. To do so, it was necessary to design a system that allows the introduction of the blade in the melt and controls its rotation.

Thermoresponsive degradable hydrogels with renewable surfaces for protein removal

Most biological materials used in the body undergo protein adsorption, which alters their biological functions. Previously, we introduced surface-degradable hydrogels as adsorbed protein-removing surfaces. However, only a few surface renewals...

The Investigation of the Amount of Blue Crab Production Regarding Other Crustaceans and Molluscs’ Farming in Türkiye

The aim of this study was to examine the factors affecting the catch rate of crustaceans and molluscs and to determine the effect of factors affecting the catch rate of blue crab. In this study, data of 14 variables (octopus, lobster, black mussel, etc.), total crustacean and mollusc content and total freshwater fish were examined from the crustaceans and molluscs caught from the TUIK website between 2012-2021. In addition to the comparison of these amounts, variables such as renewable water resources per capita, renewable surface water, total water withdrawal per capita, and water withdrawal for aquaculture were included in the study. Finally, the study was concluded by comparing seafood, aquaculture and freshwater products. The relationships between blue crab and other crustaceans and molluscs, water related statistics, aquaculture statistics were examined by regression analysis. As a result of the analyzes made, other creatures that affect the hunting rates of the blue crab; It was concluded that there is a category of jumbo shrimp, cuttlefish and other. At the same time, it was concluded that the total amount of fresh water and the amount of freshwater products affect the catch rate of the blue crab.

SPH–DEM modelling of hypervelocity impacts on rubble-pile asteroids

ABSTRACT Investigating the hypervelocity impact process on rubble-pile asteroids is crucial for understanding the formation and evolution of small celestial bodies, and has important implications for planetary defence. In recent years, numerical simulations have been widely used to model asteroid impacts, as a complement to experimental and theoretical approaches. In particular, the hybrid SPH–DEM framework has been introduced to describe the multistage dynamics involving shock propagation and gravitational re-accumulation. However, the tension between modelling accuracy and computational costs poses significant challenges in rubble-pile impact simulations. In this study, we introduce two distinct particle configurations, i.e. multiple layers of similar-sized surface contact particles and a set of different-sized gravity particles, to efficiently describe the large irregular boulders during long-term evolution. Accordingly, the new transition algorithms are implemented to convert the smoothed particle hydrodynamics (SPH) results into the desired discrete-element method (DEM) configurations. With the proposed method, the complexity of contact computation is reduced from $\mathcal {O}(N)$ to $\mathcal {O}(N^{2/3})$, and the gravity computation is accelerated by about one hundred times while maintaining the same level of resolution. The method is then used to simulate the double asteroid redirection test impact on the rubble-pile asteroid Dimorphos. Our numerical simulations have reproduced the observation results regarding momentum transfer and mass ejection. Moreover, we predict that the impact event will form a final crater larger than 45–68 m in diameter and lead to global resurfacing of the target. The renewed surface and fresh interior will be accessible to the upcoming Hera mission, providing new perspectives on the formation and evolution of the rubble-pile binary asteroids.

Visible light responsive MoS2/Ag@WO3/EG photoanode with highly stable Z-scheme induced circular electron motion pioneered by Exfoliated graphite for bisphenol a photoelectrodegradation

The alarming issue of endocrine disrupting chemicals increase in aquatic environment has heightened concerns about their potential impact on human health and ecosystem. Taking cognizance of this, the current investigation focused on fabrication of effective and efficient photoanode (MoS2/Ag@WO3/EG) from molybdenum disulphide/silver@tungsten trioxide (MoS2/Ag@WO3) photocatalyst and exfoliated graphite (EG) for the photoelectrocatalytic degradation of bisphenol A (BPA). The characterization results and Density Functional Theory (DFT) calculations together affirmed a strong interfacial contact and charge transfer direction at the interface of the materials for substantial promotion of charge separation and increased photoelectrocatalytic performance. The charge separation was further increased by EG’s “give-accept or redistribution” strategy of the charge at the interface that allowed circular motion of electrons in the formed Z-scheme heterostructure. The MoS2/Ag@WO3/EG photoanode exhibited the highest photoelectrocatalytic activity for BPA degradation with efficiency of 100% at optimum experimental conditions. The high degradation efficiency was attributed to uplifted visible light absorption emanating from EG surface plasmon resonance (SPR) contribution, formation of Z-scheme for efficient charge separation, and high stability of the photoanode, which possessed renewable surface. Moreover, scavenger experiments confirmed the participation of all the radicals (●O2– >●OH > h+) in BPA decomposition. Based on XPS, DFT, and radical experiments, the Z-scheme mechanism was proposed, and this work shed light on the production of highly effective house-made photoanode for photoelectrocatalytic processes, thus this can be a good fit in the industrial setup for degradation of other pollutants like microbials.

Early Microjet Experimentation with Liquid Water in Vacuum.

ConspectusIn this brief look at the history of liquid microjets, I recollect some personal reminiscences on initial challenges for introduction of this method, as well as unexpected problems and exemplary results using this new tool for liquid evaporation and photoelectron spectroscopy studies.Many efficient and direct, atomic level diagnostic instruments in use at solid state surfaces and in gas-phase atom or cluster studies require high vacuum. They have therefore not been applied to investigations of aqueous solutions because liquid water both strongly evaporates and rapidly freezes in vacuum. Only fairly recently, over the past three decades, have liquid microjets been considered as practicable targets for research on liquid-water interfaces in vacuum. The working principle is analogous to the functioning of a free molecular beam source, where molecules enter through a small aperture into a vacuum without being disturbed by subsequent collisions in their original Maxwellian velocity distribution. Similarly, above a microjet surface in vacuum, water vapor molecules do not interact with each other, or with different probe particles, as long as the liquid jet diameter is small in relation to the mean free path of the liquids' vapor at equilibrium conditions. For pure liquid water, this constraint is Djet < λvap < 10 μm for 6.1 mbar vapor pressure at the triple point of water. A high streaming velocity of the liquid jet, >50 m/s, delays freezing and exposes a steadily renewed fresh vacuum surface for experiments.For experimental verification of the microjet free surface concept, H2O vapor velocities were measured in a molecular beam time-of-flight experiment. These studies showed Maxwellian velocity distributions with the expected local water-jet temperatures for 5 and 10 μm jets, whereas larger liquid jet diameters of 50 μm exhibit narrowed vapor velocity profiles. This narrowing is the known signature of incipient, collision dominated, supersonic hydrodynamic expansions in nozzle beam sources. As a completely unexpected new result in evaporation studies of carboxylic acid solutions, freely evaporating acetic acid dimers showed apparent non-equilibrium liquid surface source temperatures several hundred kelvin above the simultaneously measured monomer temperatures, a phenomenon shown to be correlated with surface tension.Continuing with improvements, the vacuum water microjets were implemented inside a photoelectron spectroscopy apparatus that was modified for handling large amounts of water vapor. After initial complications with liquid jet charging phenomena, the first partial liquid-water photoelectron spectra were recorded using 21 eV photons from a He I discharge lamp. In the next step, the equipment was taken to a synchrotron radiation beamline at BESSY II, resulting in substantial improvements of signal intensity and in photon tunability for narrow band monochromatic soft X-rays up to 1 keV. Two early examples of these continuing experiments are considered, briefly, for aqueous alkali halide salt solutions and for the pH-value dependent protonation of an NH2/NH3+ group in an amino acid directly in a photoelectron spectrum of a solution.In conclusion, liquid microjets have opened up a completely new approach to studies of arbitrary liquids with chemical and biological relevance.

Interlayer Chemical Modulation of Phase Transitions in Two-Dimensional Metal Chalcogenides.

Two-dimensional metal chalcogenides (2D-MCs) with complex interactions are usually rich in phase transition behavior, such as superconductivity, charge density wave (CDW), and magnetic transitions, which hold great promise for the exploration of exciting physical properties and functional applications. Interlayer chemical modulation, as a renewed surface modification method, presents congenital advantages to regulate the phase transitions of 2D-MCs due to its confined space, strong guest-host interactions, and local and reversible modulation without destructing the host lattice, whereby new phenomena and functionalities can be produced. Herein, recent achievements in the interlayer chemical modulation of 2D-MCs are reviewed from the aspects of superconducting transition, CDW transition, semiconductor-to-metal transition, magnetic phase transition, and lattice transition. We systematically discuss the roles of charge transfer, spin coupling, and lattice strain on the modulation of phase transitions in the guest-host architectures of 2D-MCs established by electrochemical intercalation, solution-processed intercalation, and solid-state intercalation. New physical phenomena, new insight into the mechanism of phase transitions, and derived functional applications are presented. Finally, a prospectus of the challenges and opportunities of interlayer chemical modulation for future research is pointed out.

Constructing micro-dynamic surface of boron-polyurethane with endurable anti-fouling properties

Self-polishing coatings (SPC) with renewable surfaces are widely used in the shipping industry and offshore installations to prevent unexpected costs and safety concerns from marine biofouling. However, self-polishing coatings still suffer from uncontrollable release of antifouling biocides which is called “initial burst and final decay” and poor mechanical properties. Herein, a series of controlled-release boron-polyurethane antifouling coatings (DBIT) were prepared with good mechanical properties and micro-dynamic surface. 2, 2-bis(hydroxymethyl)propionic acid (DMPA) and pyridine-diphenylborane (PDB) were used as reaction sites and antifouling functional side chain groups, respectively, which endowing the coatings with the controlled release ability and good performance. The results showed that the DBIT coatings had certain mechanical properties, up to an ultimate stress of 14.8 MPa. The DBIT75 coating could reduce 90.6 % settlement of Halamphora sp., 92.7 % settlement of Nitzschia closterium, and repel the settlement of mussels. More importantly, DBITx coatings displayed excellent antifouling performance for at least 4 months in the field test, which shows that the controlled-release polyurethane coatings provide a new choice for marine antifouling applications.

Dual‐Responsive Supramolecular Antimicrobial Coating Based on Host‐Guest Recognition

AbstractThe adhesion and proliferation of the bacteria on biomedical surfaces have posed a great threat to patients. Developing a class of renewable bactericidal surface with excellent bacteria release capability is crucial for elongating the service life of the biomedical devices. However, releasing the bacteria fast and frequently is usually a trade‐off with releasing them thoroughly and completely regenerating the surface. Herein, a temperature/light dual‐responsive antimicrobial coating is developed. The cyclodextrin (CD)‐contained antifouling macromolecule and the thermal‐responsive azobenzene‐contained macromolecule are assembled on the CDs‐modified surface, combined with additional silver nanoparticles. The surface exhibits low bacteria attachments of 9.30 × 105 cells cm−2 (E. coli, 120 h), high bactericidal efficiency of ≈96.3%. Meanwhile, ≈86.9% of the attached bacteria can be released from the surface rapidly in response to temperature, and the residues can be thoroughly removed by irradiating UV irradiation (release ratio ≈91.0%). The functions of the surface can be resumed by switching the host‐guest network via light regulation. The 3rd regenerated surface still maintains low bacteria density of 12.4 × 105 cells cm−2, bacteria killing ratio of ≈95.0%, and bacteria release rate of ≈95.7%. The work is supposed to provide a new insight into the design of multifunctional antibacterial surface and broaden their applications.

Plasma facing components with capillary porous system and liquid metal coolant flow

Liquid metal can create a renewable protective surface on plasma facing components (PFC), with an additional advantage of deuterium pumping and the prospect of tritium extraction if liquid lithium (LL) is used and maintained below 450 °C, the temperature above which LL vapor pressure begins to contaminate the plasma. LM can also be utilized as an efficient coolant, driven by the Lorentz force created with the help of the magnetic field in fusion devices. Capillary porous systems can serve as a conduit of LM and simultaneously provide stabilization of the LM flow, protecting against spills into the plasma. Recently, a combination of a fast-flowing LM cooling system with a porous plasma facing wall (CPSF) was investigated [A. Khodak and R. Maingi, Nucl. Mater. Energy 26, 100935 (2021)]. The system takes an advantage of a magnetohydrodynamics velocity profile as well as attractive LM properties to promote efficient heat transfer from the plasma to the LL at low pumping energy cost, relative to the incident heat flux on the PFC. In the case of a disruption leading to excessive heat flux from the plasma to the LM PFCs, LL evaporation can stabilize the PFC surface temperature, due to high evaporation heat and apparent vapor shielding. The proposed CPSF was optimized analytically for the conditions of a fusion nuclear science facility [Kessel et al., Fusion Sci. Technol. 75, 886 (2019)]: 10 T toroidal field and 10 MW/m2 peak incident heat flux. Computational fluid dynamics analysis confirmed that a CPSF system with 2.5 mm square channels can pump enough LL so that no additional coolant is needed.

Polarography with non‐mercury electrodes: A review

AbstractThis article reviews non‐mercury configurations that have hitherto been reported in the literature as the working electrodes applicable in polarographic measurements. The individual types, namely gallium, liquid amalgams, dropping electrolyte, and carbon fluid electrodes, together with a carbon paste‐based assembly or even solid disc electrodes with a periodically renewable surface, are presented, discussed, and critically assessed with respect to their potential employment in the present day's electrochemistry and electroanalysis.

Highly Efficient and Sustainable PM Filtration Using Piezo Nanofibrous Membrane with Gradient Shrinking Porous Network

Nanofibrous filters have limited filtration against ultrafine airborne particulate matter (PM) due to thick fiber fineness and large pore size, which can be unraveled by increasing thickness and basis weight, however, the pressure drop of the filters also increases sharply. Inspired by the bryophyte leaf structure, unconventional piezo nanofibrous membranes with gradient shrinking porous network are created for PM filtration by one-step electrospinning of polyvinylidene fluoride (PVDF), dibenzylidene sorbitol (DBS), and short-chain fluorinated alkyl modified silica (F-SiO2) through pattern metallic mesh collectors. The membranes are assembled into charged and hydrophobized gradient porous networks with pores in feeding to outlet gradually shrinking. This structure features a well-designed filtration mechanism that balances filtration efficiency and pressure drop, facilitating high trap efficiency against PM (PM0.3 > 98.82%; PM0.5 > 99.87%, quality factor ∼ 0.121–0.507 Pa−1; PM0.8–7.5 = 100%) with a low pressure drop (16–55 Pa) and good stability in an acid, alkali, ultraviolet (UV), or humid environment. Simultaneously the piezo nature of the membrane endows renewable surface charge richness by hand pressing to provide sustainable caption of ultrafine particles, especially PM0.3. This study provides a new design approach for constructing PM filters in a reliable, sustainable and affordable way.

S-scheme BiVO4/CQDs/β-FeOOH photocatalyst for efficient degradation of ofloxacin: Reactive oxygen species transformation mechanism insight

Photocatalysis technology exhibited promising application for advanced treatment of wastewater. Nevertheless, the design of efficient photocatalyst and the mechanism of free radicals in pollutant degradation still remained to be further investigated. Herein, BiVO4/CQDs/β-FeOOH photocatalyst was fabricated by electrostatic self-assembly method, which exhibited the excellent photocatalytic performance. Under visible-light irradiation, the removal rate of ofloxacin by BiVO4/CQDs/β-FeOOH (0.25 min−1) was 1.93 times than pristine BiVO4, and the removal efficiency in 15 min reached 99.21%. The perfect reusability of BiVO4/CQDs/β-FeOOH was ascribed to the persistent catalytic active centers provided by the renewable surface oxygen vacancies on the β-FeOOH. As electron transfer channels, CQDs facilitated the transfer of BiVO4 photogeneration electrons. The matched band structure allowed the construction of S-scheme heterojunctions, and the higher conduction band position was retained while the carrier separation was promoted. More importantly, this work firstly reported the phenomenon that the main reactive groups in the photocatalysis process would be directionally transformed with the change of pH conditions. Based on the analysis of capture and electron paramagnetic resonance experiments, ·O2− was the main free radicals to photodegrade OFL in neutral and alkaline conditions. However, when the solution pH turned into acidic, the photodegradation of OFL was dominated by 1O2. This innovative phenomenon was due to that acidic condition accelerated the reaction kinetics of spontaneous transformation of ·O2− to 1O2 and inhibited the direct oxidation of pollutants by ·O2−. Accordingly, this research could inspire theoretical study of free radical reaction and the design of S-scheme heterojunction photocatalysts.

Structure of interfaces on mechanically renewed Sn, Pb, and Sn-Pb electrodes in acetonitrile solutions of surface inactive electrolytes

• Ideal polarizability regions of Sn and Pb electrodes in AN solutions were found. • Zero charge potentials of Sn and Pb in AN solutions were determined. • Time changes of capacitance curves are observed on Sn-Pb electrode after renewal. • It is shown that Pb atoms are squeezed out to the surface layer of Sn-Pb electrode. • Time effects on renewable Sn-Pb/AN solutions interface were analyzed in detail. The electrical double layer (EDL) structure of mechanically renewed electrodes of Sn, Pb, and Sn-Pb alloy (1 at.% Pb) is studied in acetonictrile (AN) solutions of LiClO 4 by the impedance method and cyclic voltammetry. The potential regions are found in which these electrodes can be considered in good approximation as ideal polarizable. In these solutions, the potentials of zero charge ( E σ = 0 ) on Sn and Pb electrodes are found to be –0.37 ± 0.02 and –0.59 ± 0.02 V (vs. aqueous SCE), respectively. The experimental dependences of the capacitance on the potential are shown to be in good agreement with the classical EDL model of Gouy–Chapman–Stern–Grahame. Based on the results of capacitance measurements carried out on renewed Sn-Pb electrodes, it is found that as the time of exposure of the renewed alloy surface to electrolyte increases, the C vs. E curves indicate that the concentration of lead atoms in the surface layer of alloy also increases, i.e., Pb is the surface-active component of these alloys. By analyzing the observed time effects, the surface coverage of Sn-Pb electrode by lead atoms (θ) is calculated in different time ( t ) after the renewal. It is shown that the θ vs. t dependences well agree with the model proposed earlier that describes the process of surface segregation of atoms of the surface-active component of eutectic alloys by the mechanism of surface diffusion. The kinetics of process of surface segregation of lead atoms on the mechanically renewed Sn-Pb electrode is compared for AN and aqueous solutions. The increase in θ is found to proceed slower in AN solutions than in aqueous solutions of the similar composition. The main reason for the differences observed is proposed.

Self-induced transformation of raw cotton to a nanostructured primary cell wall for a renewable antimicrobial surface.

Herein, raw cotton is shown to undergo self-induced transformation into a nanostructured primary cell wall. This process generates a metal nanoparticle-mediated antimicrobial surface that is regenerable through multiple washings. Raw cotton, without being scoured and bleached, contains noncellulosic constituents including pectin, sugars, and hemicellulose in its primary cell wall. These noncellulosic components provide definitive active binding sites for the in situ synthesis of silver nanoparticles (Ag NPs). Facile heating in an aqueous solution of AgNO3 activated raw cotton to produce Ag NPs (ca. 28 nm in diameter and 2261 mg kg-1 in concentration). Compared with scoured and bleached cotton, raw cotton requires lower concentrations of AgNO3-ten times lower for Klebsiella pneumonia and two times lower for Staphylococcus aureus-to achieve 99.9% reductions of both Gram-positive and Gram-negative bacteria. The Ag NPs embedded in the primary cell wall, which was confirmed via transmission electron microscopy images of the fiber cross-sections, are immobilized, exhibiting resistance to leaching as judged by continuous laundering. A remarkable percentage (74%) of the total Ag NPs remained in the raw cotton after 50 laundering cycles.

Use of structural anomalies in steel gas-thermal coatings during increased wear-out

The structure of gas-thermal coatings made of wire materials has been studied by determining the most efficient methods of controlling the process of structure formation to achieve the highest physical and mechanical properties of renewable surfaces of vehicle parts. The effect of formation of anomaly amount of residual austenite in sprayed steel coatings was established. Technologies of application of the “austenitic effect” is suggested here to increase a coating wear-resistance. It is determined that the main factors influencing the content of residual austenite in hardened steel are the cooling rate of steel, the concentration of alloying elements in the austenitic phase, as well as thermal stabilization of austenite during self-tempering. It is shown that to ensure the formation in the structure of sprayed coatings of alloy structural, tool and corrosion-resistant steels of metastable austenite, which has a low flow temperature of deformation gamma-alpha transformation, which corresponds to the operating temperatures of sliding friction units, it is necessary to achieve certain coating conditions. wire spraying, cooling rate of molten particles and the degree of their oxidation). One of the most probable reasons for the appearance of the "austenitic effect" in coatings is the heating of the surface layer to a temperature that promotes thermal stabilization of austenite, as well as saturation of melt droplets with alloying elements (primarily chromium) and impurities (carbon, nitrogen) in flames. The relatively low flight speed of molten steel particles and the high concentration of propane containing carbon in the combustion products contribute to the deep saturation of the melt droplets with carbon. It is likely that these circumstances are associated with a high content of residual austenite in the coatings obtained by gas-flame spraying. An additional factor that increases the resistance of austenite in the sprayed coating may be the saturation of the droplets of the melt with carbon during melting and spraying using a propane flame. The studies under discussion have suggested that both for the method of gas-flame spraying and for the method of electric arc spraying, there are modes and steels for spraying that allow the formation of large amounts of metastable austenite in coatings, which in the process of tribocoupling will turn into martensite.On the basis of the carried-out researches technologies of restoration of details of vehicles by drawing multipurpose coverings in which the choice of a method of heating of a wire at spraying is carried out depending on temperature of the beginning of martensitic transformation of a wire material are offered.

Measuring the levels of Zn, Cu, Pb and Cd via the polarography method in fermentative pickled cucumbers purchased from Tehran market, Iran

Pickled cucumber is frequently consumed by Iranians. According to the production process, there are two forms of pickled cucumber including industrial and fermentative. There is not an appropriate monitoring system available for the production of the latter form; therefore, high levels of heavy metals might be present in this type of pickled cucumber. Accordingly, so the levels of cadmium, zinc, lead and copper were measured in fermentative pickled cucumbers obtained from the Tehran market via the polarographic method. Polarography is a subclass of voltammetry where the working electrode is a dropping mercury electrode (DME) or a static mercury drop electrode (SMDE), which are useful for their wide cathodic ranges and renewable surfaces. Fifty different samples of pickled cucumbers were purchased from the market. Of each sample, dry ashes were produced. Measurement was repeated three times and the acquired data was then analyzed. The mean levels of zinc and copper in the evaluated samples were significantly lower than the standard limits respectively presented by the EOS and Codex (P value&lt;0.001) while the mean level of cadmium and lead was slightly higher than the standard limit established by Codex with no significant differences observed (P values=0.450 and 0.246, respectively).

Low Temperature Rare Earth Alloy Formation in Molten Metal

Rare earth element (REE) processing, both separation stages and metal production, is chemically intensive. Conventional methods for reducing REEs include molten salt or fused salt electrolysis, and metallothermic reduction. During molten salt electrolysis, separation is achieved by the formation of a “low temperature” (~1100°C) REE alloy employing the use of a liquid cathode such as Zn or Cd [1]. The molten REE metal which is less dense, rises to the surface and is subsequently separated [1]. In metallothermic reduction, conproportionation is used to effectively reduce REEs such as La, Ce, Pr, and Nd at 1100°C using reactive metals such as Na, Li, Al, K, Ca, and Fe [2]. Separation of REEs through solvent extraction or ion exchange is challenging due to nearly equivalent chemical properties and lack of diversity in redox state across the series. Separation is limited to very small separation factors which require up to hundreds of stages to achieve pure products [3]. While these conventional methods are used to process REEs, an alternative was reported involving the amalgam formation for the reduction and separation of REEs [4]. This work was prevalent during the 1940s through the 1960s in nuclear materials processing work, but left dormant for the past half century [4]. The advantages of using liquid metal electrodes such as Hg over solid electrodes is the high hydrogen evolution reaction (HER) overpotential and the reduced reduction potential through alloy formation, allowing reduction from aqueous solution. Previous work showed that REEs formed amalgams over one volt more positive than the standard reduction potential [5]. However, Hg is toxic and thus not suitable for new chemical processes. To utilize alloy formation as a processing route, there is a need for a material substitute with similar characteristics but a nontoxic nature. The promising nature of Ga and Ga alloys have made it an attractive substitute for mercury electrodes. Similar to mercury, Ga and Ga alloys possess a high HER overpotential, renewable surface, and a low vapor pressure [6]. This research investigates the reduction of REEs using liquid Ga as cathode material. The kinetics involving the formation of amalgams with rare earths are studied, as well as the reduction or entrainment of REEs in Ga oxides.In this work REE elements Pr and Nd are reduced at the cathode which comprises a Ga pool electrode with a submerged copper contact. Ga-REE alloys, and entrainment of REEs into a solid dark mass via Ga oxidation were observed to have been formed with each element. This was corroborated through data analysis. This work is part of an effort to process critical materials such as Pr and Nd from magnets, coal fly ash and ores. The setup was designed to operate slightly above room temperature (slightly above the Ga melting point). During electrolysis in the presence of Pr and Nd, two phases are formed. We observe that the shiny Ga surface turns dull during the electrochemical process above ~-1.3 V vs Ag/AgCl in lithium acetate electrolyte. When the electrochemically formed alloy is leached in dilute HCl, analysis shows REEs in the leachate, H2 gas production (water reduction), and a lower REE concentration in the electrolyzed solution. In similar experiments with a stirred Ga pool, a dark grey solid mass is formed. The mass appears to form due to the oxidation properties of Ga in aqueous solution with the reduced REE present. When filtered and analyzed, this mass is rich in REE containing over 50 wt% of REEs from the feed solution with higher concentrated feed solution, and over 90 wt.% of REEs from coal fly ash surrogate solutions. These preliminary results show some encouraging new routes to REE processing.