Morphology Of Deposits Research Articles

(Invited) Near-Surface pH during the Electrodeposition of Iron Group Metals

The all-iron flow battery initially proposed in 1981 by Hruska and Savinell represents a cost effective and environmentally benign system for large scale energy storage1. The all-iron chemistry consists of the Fe2+/Fe3+ redox reaction at the positive electrode, and iron plating and stripping at the negative electrode. Because the standard reduction potential for iron plating is more cathodic than that of hydrogen evolution, electrolyte pH heavily influences coulombic plating efficiency as well as deposit morphology and microstructure2-5. Increasing the electrolyte pH decreases the diffusion limited current for hydrogen evolution and shifts the equilibrium potential more negative6. However, iron is not stable at high pH as shown by the Pourbaix diagram, where it will precipitate as hydroxide species. Boric acid is a common component in iron group plating baths where it is believed to function as a buffering agent helping to stabilize pH near the electrode7-9. However, it is not understood how boric acid with a pKa value of 9.27 can buffer at low pH10. The aim of this work is to further understand the effects of pH near the electrode surface and the role of boric acid on the electrodeposition of iron group metals.Electrodeposition of selected iron group metals will be discussed with a focus on the effect of boric acid. We present an in-situ technique for monitoring near surface pH as a function of plating current density. This measurement is accomplished using a tungsten microelectrode which acts as an indicator for hydrogen ion activity11-13. Our results demonstrate that boric acid is not effective in buffering the near surface pH in the acidic baths tested. Even at high current densities in a pH 2.5 electrolyte, the near surface pH did not exceed 6. However, the addition of boric acid improved deposit morphology and current distribution; coupons plated from electrolytes containing boric acid, and those without, are compared and discussed. At high current density and high pH, boric acid incorporates into the deposits, which is studied by use of inductively coupled plasma optical emission spectrometry (ICPOES). Electrochemical impedance spectroscopy, cyclic voltammetry, and coulombic efficiency data aid in understanding additive adsorption as well as the influence of boric acid on the deposition mechanism. In addition to surface specific information, the effects of boric acid on exhaustive plating and long-term bath stability will be presented to account for buffering effects in the bulk electrolyte when pH exceeds 6.References W. Hruska and R. F. Savinell, Journal of The Electrochemical Society, 128, (1) 18-25 (1981)R. Gabe, Journal of Applied Electrochemistry, 27, 908 (1997)Nakahara and S. Mahajan, Journal of the Electrochemical Society, 127 (2) (1980)Cohen-Hyams, Wayne D. Kaplan, Joseph Yahalom, Electrochemical and Solid-State Letters, 5 (8) C75-C78 (2002)Hawthorne et al., Journal of The Electrochemical Society, 162 (1) A108-A113 (2015)Hilbert, Y.Miyoshi, G. Eichkorn, and W. J. Lorenz, Journal of the Electrochemical Society, 118, 1927 (1971)Zech and D. Landolt, Electrochimica Acta, 45 (21) 3461-3471 (2000)P. Hoare, Journal of The Electrochemical Society, 133 (12) 2491-2494 (1986).Santos, R. Matos, F. Trivinho-Strixino and E. C. Pereira, “Effect of temperature on Co electrodeposition in the presence of boric acid” Electrochimica Acta, vol. 53, pp. 644-649 (2007)R. Lide, CRC Handbook of Chemistry and Physics, p. 1274, CRC Press, Boca Raton, FL (2005)E. S. El Wakkad, H. A. Rizk and I. G. Ebaid, The Journal of Physical Chemistry, 59, (10) 1004-1008 (1955)O. Park, C.-H. Paik and H. C. Alkire, Journal of The Electrochemical Society, 8, (143) p. 174 (1996)Webb and R. Alkire, Journal of The Electrochemical Society, 146, (6) p. B280 (2002)

Controlling the Morphology of Electrodeposited Lithium Metal Via Seeded Growth: Stepwise Spherial to Fibrous Lithium Growth

Lithium metal has been gained intense research interest because of its high specific capacity and lowest electrochemical potential for next generation battery systems with high energy density. However, the utilization of Li metal as an anode material has been limited due to the uncontrolled Li deposition and side reactions on Li metal surface that induce low coulombic efficiency, poor cycle performance and safety issues. Controlling morphology of electrodeposited Li metal is one major direction to resolve these issues. Identification of Li deposition mechanism governing the morphology evolution is prerequisite for establishing strategy for controlling morphology. Herein, we explore governing deposition mechanism from the morphology evolution at varied current (0.2- 1.8 mA cm-2) and suggest a strategy for growing low surface area Li fibers.We found that fibrous Li growth follows the initial spherical Li particle formation when the Li sphere size reaches the critical value. The diameter of the initially formed Li particles decreases with the current density. Initially formed spherical Li particles at a low current density (0.2 mA cm-2) are sufficiently large to grow with a fibrous morphology. Thus, the spherical particles evolve to fibrous Li during subsequent growth. On the other hand, at a higher current density, the Li particles are initially smaller than the critical size and thus cannot immediately grow into a fibrous morphology. Spherical growth of the existing Li particles and additional nucleation on the current collector surface continue, resulting in multilayer Li particles. After Li particles reach the critical size, Li can grow with a fibrous form. Due to the preferential deposition on the existing fibrous Li, the morphology of spherical Li particles smaller than the critical size does not change. Therefore, only fibrous Li deposits were formed at low current density (0.2 mA cm-2), but both spherical and fibrous Li deposits were formed at higher current densities.Based on the morphology evolution mechanism, seeded Li deposition strategy was proposed to minimize the surface area of Li deposits and improve cycling stability of Li metal electrode. The stepwise spherical to fibrous Li growth was achieved by changing the current from low to high (0.2 to 1.8 mA cm-2). Li deposits morphology was well controlled by this strategy resulting in all fibrous morphology with smooth surface. The Li deposits of seeded growth strategy achieved smaller surface area, suppressed side reactions and improved cycle life more than four times compared to that of constant current deposition with same average current density (1 mA cm-2). Figure 1

Challenges in Understanding Electrochemical Growth

Over the past 100 years, electrodeposition has matured to an important method with numerous industrial applications, up to processes in micro- and nanofabrication. Knowledge on electrochemical processes on the atomic scale is still limited, however. While for vapor deposition under vacuum conditions the evolution of the deposit morphology can nowadays be predicted with high precision, a similar predictive understanding of electrodeposition is missing so far. A key issue here is the electrochemical interface where this growth occurs. The structural complexity of this interface on the one hand makes understanding of the elemental processes in nucleation and growth difficult. On the other hand, it is just this complexity that allows to tune electrodeposition processes in ways that are not possible for deposition in vacuum and thus make them attractive for many applications.In this talk, I will discuss current challenges in developing a true microscopic picture of electrodeposition processes, using examples from us and other groups. The focus will be on puzzling experimental observations and fundamental aspects that we do not yet understand and thus provide a rich field for future research. These include the mechanisms of elemental steps in electrochemical growth processes, such as ion transfer, intra- and interlayer surface diffusion, and the resulting development of the deposit morphology. Of particular interest is how these events are influenced by the electric field and electrolyte species in the electrochemical double layer, which is of key relevance for understanding the effects of overpotential and additives. A further challenge is to extend the insights obtained for electrodeposition of metals to the electrochemical growth of compound materials, such as oxides.

The Adoption of Lithiophilic Nano Sn on Cu Current Collector By Electroplating Techniques to Improve the Stability of Lithium Metal Anode

The growing demand for higher energy density batteries is increasing due to needs of electric vehicle (EV) [1]. Until now, it cannot exceed the one-time charging distance of an internal combustion engine vehicle, due to energy limit of batteries. Li metal anode (LMA) is one of the attractive anode candidates because of the lowest electrochemical redox electrode potential (-3.04 V vs. SHE) and the extremely high theoretical gravimetric capacity (3,860 mAh g-1) compared to graphite anode (372 mAh g-1) [2]. However, uneven Li deposition causes dendritic growth leading to low Coulombic efficiency (CE) and safety hazards which is impeding the practical use of LMAs [3]. Recently, to suppress such dendritic growth, various solutions such as introduction of solid-state electrolyte (SSE) [4], artificial solid electrolyte interphase (ASEI) [5], 3D current collector (CC) [6], and lithiophilic materials [7] have been proposed.Among the several approaches, introducing lithiophilic material on a CC is one of the facile and effective strategies to increase the lithiophilicity, and hence to induce the planar growth of Li. Also, assuming that electroplating is largely divided into two steps: nucleation and growth, lithiophilic material can change the intrinsic nucleation behavior by preferentially forming a different phases such as Li alloys [8]. Since the Li nucleation process significantly influences the final growth of Li, different cycling behaviors of LMAs would be expected depending on lithiophilic material [9]. As for the methods to adopt the lithiophilic materials, the electrodeposition is very attractive, since it can easily control the surface morphology, which might affect the Li deposition morphology and the related behavior. In this regard, we chose the tin (Sn) as a lithiophilic material, which can be deposited on Cu CC by electroplating, and moreover have a fast Li ion diffusion coefficient [10].Specifically, in this work, we study the effect of surface morphology of lithiophilic Sn deposited on copper CC by testing Li deposition/stripping behavior for a LMAs. For different morphology, a direct current electrodeposition (DC) and pulsed electrodeposition (PED) were used. Fig.1 is FE-SEM images of Cu@Sn with DC growth and PED growth. Fig.1 (a) shows Sn particles are growing without filling the pores. However, Fig.1 (c) shows Sn particles are growing with filling the pores. At Fig.1 (b) and (d), the morphology difference is conspicuous between DC and PED growth. Fig.1 (b) presents island growth in which nuclei grow on existing nuclei because there is only Ton without relaxation time. While, Fig.1 (d) shows that after rearrangement of deposited atom at Toff, new nucleation sites are created by continuously applying pulses, thereby obtaining the coalescence growth. At Fig.2, Cu@Sn (PED) shows the longer cycle life than bare Cu and Cu@Sn (DC) because Cu@Sn (PED) has an uniformly distributed nano Sn morphology, which provides more sites for Li nucleation to prevent dendritic growth.

Laser‐Directed Energy Deposition Additive Manufacturing of Nickel–Titanium Coatings: Deposition Morphology, Microstructures, and Mechanical Properties

To overcome the disadvantages of comparatively poor surface hardness and deprived resistance against wear of Ti–6Al–4V alloy, the protective NiTi coatings are fabricated at different processing parameters by laser‐directed energy deposition (LDED). This work presents a comprehensive study of deposition morphology, phase constituents, microstructural evolution, composition distribution, and mechanical properties of as‐fabricated NiTi deposition tracks. The relationship among processing parameters and deposition morphology, phase constituents, and mechanical properties is established. The microstructural evolution mechanism and the composition distribution on the cross section of deposition tracks are revealed. Results show that the deposition tracks are successfully formed under all laser processing parameters, and the dilution ratio increases with the increase in laser power and scanning speed. The deposition tracks consist of NiTi2, NiTi, and α–Ti. According to the microstructural analysis, planar crystals are formed between the substrate and the deposition tracks, and columnar and equiaxed dendrites are found in the deposition tracks. The average microhardness increases continuously with the increase in laser power. The deposition track prepared at laser power of 1400 W has the highest average microhardness of 732.45 HV0.2. The deposition track at this laser power exhibits excellent wear properties, with a wear rate of 2.25 × 10−6 mm3 Nm−1.

Offset impacting of a liquid aluminum droplet train on a molten pool on a horizontally moving substrate during TIG-assisted droplet deposition manufacturing

Internal metallurgical defects and poor mechanical properties and surface quality of the formed parts are the most important challenges of metal micro-droplets deposition manufacturing technology. Lack of strong coalescence between neighboring droplets and the blocking effects of periodic ripples on the fusion process are major sources of abovementioned problems. To address this issue, a tungsten inert gas (TIG) welding arc was introduced to pre-melt the material below the droplet impacting location, thus, one droplet train will be deposited on a curved molten pool surface to fabricate deposited layers in an additive approach. In the present work, a numerical model based on the computational fluid dynamics (CFD) method was developed to investigate the dynamic behaviors of successive droplets’ impact and coalescence on the molten pool created by a tilted TIG welding arc, and focuses on the effect of the offset distance between the impacting point of droplet and the longitudinal plane of molten pool on the deposition morphology and the impact-induced molten pool behaviors. The simulated tracks exhibit regular scaly shapes at different offset distances, which is validated against the corresponding experiments. The results indicated that as the lateral offset distance increases, the symmetric spreading and recoiling of the subsequent droplets on the pre-existing bead will be broken due to the inclined and curved solidification front morphologies, the inclined front morphologies are caused by the increased growth rate of the solidification front at the impact zone. With an increased lateral offset distance, the volume of the molten pool decreases, the width of the rear molten pool increases slightly. The calculated solidification parameters are found to be dependent of the offset distance, and vary significantly at the onset of solidification at different portions of the molten pool. The scientific findings provide useful insights for further researches of TIG-assisted DDM.

Impact of LiF Particle Morphology on Overpotential and Structure of Li Metal Deposition

It has been widely suggested in literature that a lithium fluoride (LiF)-rich solid electrolyte interphase (SEI) affects Coulombic efficiency (CE) of the Li metal anode used with liquid electrolytes. Yet, the influence of LiF on Li metal deposition has been challenging to examine. Herein, we developed a method to synthesize LiF nanoscale particles with tunable sizes (30–300 nm) on Cu electrodes by electrochemical reduction of fluorinated gases under controlled discharge rates and capacities. The impact of LiF nanoparticles on overpotential and morphology of Li deposition was further studied in a conventional carbonate electrolyte. By cyclic voltammetry, Li plating overpotentials exhibit a clear correlation with the total surface area of LiF particles. Additionally, Li metal deposits (10 μAh cm−2) nucleated under galvanostatic conditions (0.5 mA cm−2) on Cu/LiF showed increasing feature sizes with a lower average LiF particle size and higher coverage of LiF. However, no significant improvement in CE was observed for LiF-coated Cu. Our findings provide evidence that a particle-based mode of SEI fluorination can influence early-stage Li nucleation to a modest degree, and this effect is maximized when LiF is uniformly and densely distributed. However, sparser and larger LiF have vanishing or even detrimental effect on cycling performance.

Electrochemical Sensing of Nitrofurazone and Semicarbazide on an Au-Ag Film Fabricating from a Deep Eutectic Solvent

A facile electrochemical sensor is reported for the highly selective and sensitive detection of nitrofurazone (NFZ) and its metabolites, semicarbazide (SC), by using an Au-Ag modified electrode. The Au-Ag film was produced on a Cu foil by electrodeposition in a choline chloride-urea-glycerol ternary deep eutectic solvent containing gold (III) ions and silver (I) ions. Cyclic voltammetry (CV) indicates that the co-deposition of Au-Ag would be feasible. The morphology, crystallinity, and composition of Au-Ag deposits were characterized via scanning electron microscopy (SEM), powder X-ray diffractometer, and X-ray photoelectron spectroscopy (XPS). Under the optimal condition, the Au-Ag modified electrode shows a wider linear concentration range of 1.99–643.49 μM with a low detection limit of 0.2 μM for NFZ. The corresponding linear range of SC is 7.94 to 482 μM, and the detection limit is 1.01 μM. It also demonstrated good anti-interference ability against various common interfering substances. Finally, the modified electrode was successfully applied in the real samples, and the average recoveries for NFZ and SC were 100.59% and 101.01%, respectively. The present electrochemical strategy is promising to broaden the practical electrochemical application in the environment.

The effect of electrophoretic deposition of carbon nanotubes onto carbon fiber on the interlaminar resistance of carbon reinforced aluminum laminates

Functionalized multi-walled carbon nanotubes were deposited on the carbon fabric using ultrasonic-assisted electrophoretic deposition. The effect of carbon nanotubes (CNTs) deposition time and morphology on the mode I interlaminar fracture resistance of carbon reinforced aluminum laminates (CARALL) was investigated. The formation of a proper network of CNTs on the carbon fabric favorably deviated the crack growth into the carbon fabric layer and intensified the fiber bridging during the delamination. The CNT coating on the carbon fiber in conjunction with the alkaline-acid treatment on the Al substrate significantly promoted the interlaminar fracture initiation and propagation energies and stabilized the fracture behavior.

Chromitite deposits of Ufaley ultramafic massif (South Urals)

Data on the morphology, composition, textural and structural features of chromite deposits of the Ufaley ultramafic massif are presented. The mineralogical and compositional features of the host ultramafic rocks allow us to interpret them as depleted restite from partial melting of mantle peridotites. Relatively wide variations in the composition of ore-forming chromian spinel grains (#Cr 0.6–0.8) and noticeable metamorphism of disseminated ores with replacement of chromite by Cr-magnetite are noted. It is assumed that chromitite bodies were initially formed under the conditions of the upper mantle by a rheomorphic mechanism, and then their structural and geochemical transformation took place in the collisional setting of the upper part of the crust. Flattened bodies of disseminated chromitites have been preserved near competent gabbroid blocks, while other deposits have been transformed into lenses and podiform bodies of densely disseminated and massive ores of smaller size. The “cold tectonics” of the crustal stage led to the disintegration of deposits and the simultaneous local enrichment of deformed chromitite bodies.

In English

Carbon nanostructures (CNS) were synthesized by the electric arc plasma chemical method during the evaporation of a high-quality graphite electrode of the brand “fine-grained dense graphite” (FGDG-7) filled with a catalyst (Pt), which was evaporated in a helium environment. In the synthesis process, the following were synthesized: multi-walled (MWCNT) and single-walled carbon nanotubes (SWCNT), fullerenes, graphene packets and nanocomposites. A deposit in the form of growth on the cathode electrode was also synthesized. All synthesis products were analyzed at the micro- and nanolevels, which made it possible to analyze the influence of platinum vapors on the formation of carbon nanomaterials (CNM). The non-uniform distribution of catalyst atoms (platinum) in the products of electrochemical synthesis in a gas medium using FGDG-7 graphite was investigated. During the analysis, it was found that platinum is in the state of the face-centered cubic (FCC) lattice and is distributed in the synthesis products as follows: the core of the deposit is less than < 0.001 %, the shell of the deposit is less than < 1 %, the wall soot is more than > 1 %. The morphology and composition of the platinum deposit, which has a hexagonal graphite structure with an admixture of a rhombohedral graphite phase, was studied. In the studies, differential thermal analysis in air (TG, DTG, DTA) was carried out, which made it possible to identify the composition of the synthesis products. It is an established fact that the parts of the deposit with platinum are more heat-resistant compared to the deposit components that do not contain Pt. The resulting carbon nanotubes (CNTs) in diameter (5–25 nm) and length (1.5–2 μm) do not differ from those obtained without the participation of platinum, except for some anomalies. When studying the suitability of platinum-containing carbon nanostructures for 3D printing of CJP (ceramic printing) technology, it was found that for the use of platinum-containing carbon black, it is necessary to carry out a preliminary short-term treatment, namely, grinding in special “ball mills” or rubbing through a fine sieve with minimal effort to create uniformity product. Previous studies have shown that such platinum-containing carbon nanostructures can already be used in 3D printing of CJP technology, or to create new composites for 3D printing technologies of FDM, SLA.

Facile Electroless Plating Method to Fabricate a Nickel-Phosphorus-Modified Copper Current Collector for a Lean Lithium-Metal Anode.

The compatibility of current collectors with reactive Li is key to inducing stable Li cycling and prolonged cycle life of lean Li-metal batteries. Herein, a thin and uniform layer of Ni-P complex was built on the surface of a Cu current collector (NiP@Cu) via an efficient, controllable, and cost-effective electroless plating method. The thickness, morphology, composition, and roughness of the Ni-P deposition were successfully regulated. Lithiophilicity of the current collector was greatly improved by Ni-P deposition, which effectively reduced the Li nucleation overpotential and suppressed the Li dendrite growth. In addition, NiP@Cu promoted an inorganic LiF/Li3P-rich solid electrolyte interphase to facilitate interfacial charge transfer and eliminate excessive side reactions between Li and the electrolyte. As a result, the Coulombic efficiency of half-cells remained above 98.5% for more than 400 cycles at 0.5 mA/cm2 and 98.2% for more than 250 cycles at 1 mA/cm2. Full cells with NiP@Cu also showed superior performance compared to those with bare Cu. This work proposes a promising surface modification method to develop a stable, dendrite-free, and cost-effective anode current collector for high-energy-density lean Li-metal batteries.

(Digital Presentation) Influence of Pulse Electrolytic Conditions on Deposition Morphology of Electrolytic Aluminum Foil Using Chloroaluminate Ionic Liquids

We have investigated the influence of additive agent on the deposition morphology of the electrolytic Al foils using the AlCl3–1-ethyl-3-methylimidazolium chloride (EMIC) (molar ratio 2 : 1) bath. The electrolytic Al foils were prepared by the pulse electrolysis. The morphology and the surface roughness of the electrolytic Al foils were characterized by FE-SEM, AFM, and XRD. The surface roughness and the crystallite size of the electrolytic Al foils were decreased by increasing the pulse frequency and the addition of 1,10-phenanthroline (OP). It was found that the OP addition had more greatly influence on the surface roughness of the electrolytic Al foil than the pulse frequency.

Electrodeposition of crystalline Si in molten alkali metal fluoride–chloride mixtures: Comparative study of Li, Na, K, and Cs systems

A comparative study was conducted on the electrodeposition of Si using molten salts of AF–ACl–A2SiF6 (A = Li, Na, K, Cs, AF–ACl = 50:50 mol%) at 1073 K. Cyclic voltammetry revealed that the electrodeposition potential of Si was negative in the order of Na > K > Cs systems with reference to Cl2/Cl−, and almost the same as with reference to F2/F−. In the Li system, no cathodic current peak was observed, owing to the formation of the Li–Si alloy. In the Na and Li systems, the cathodic peak current density decreased with time owing to the decomposition of SiF62− ions. The differences in the Si electrodeposition and thermal stability of SiF62− ions can be explained by the interactions of alkaline cations and F− ions; smaller cations interact more strongly with F−, resulting in the reduced thermal stability of SiF62−. Electrodeposited Si was confirmed to be crystalline by XRD, and its morphology was film-like in the K and Cs systems, and whisker-like in the Na system. A difference in nucleation and growth was observed between the K and Na systems, which explains the difference in the morphology of the Si deposits.

A Descriptive Analysis of Patients Undergoing Cytoreductive Surgery for the First Peritoneal Recurrence from Adult Granulosa Cell Tumours: Focus on Disease Distribution, Morphology of Peritoneal Disease and the Role of HIPEC - a Retrospective Study by INDEPSO.

The aim of the present study was to report the clinical outcome and factors affecting survival in patients with first recurrence of AGC treated with cytoreductive surgery with or without HIPEC. The second aim was to study the disease distribution in the peritoneal cavity according to the peritoneal carcinomatosis index (PCI) and the morphology of peritoneal deposits. In this retrospective multicentric study, all patients of adult granulosa cell tumor with peritoneal recurrence were treated with CRS with or without HIPEC. Relevant clinical and demographic data were captured. Multivariable logistic regression was performed to evaluate the factors affecting recurrence after CRS ± HIPEC. Factors affecting survival and second recurrences were evaluated in addition to studying the disease distribution at first recurrence. In the period from January 2013 to December 2021, 30 consecutive patients of recurrent adult type granulosa cell tumor of the ovary undergoing CRS ± HIPEC were included in this study. The median follow-up duration was 55months [12-96months]. The median rPFS and rOS were both not reached. HIPEC (p = 0.015) was the only factor independently associated with a longer rPFS. CRS with or without HIPEC can be performed with an acceptable morbidity in patients with the first recurrence from adult granulosa cell tumours. The role of HIPEC, patterns of peritoneal spread and impact of other prognostic factors on the treatment outcome all need further evaluation in larger series of patients.

Ultrafast microwave-induced synthesis of lithiophilic oxides modified 3D porous mesh skeleton for high-stability Li-metal anode

The wide application of Li metal anodes is hindered by the inhomogeneous growth of Li dendrites. Herein, we propose an ultrafast microwave-induced synthesis method for a lithiophilic 3D porous mesh skeleton converted by commercial brass mesh. Due to the lithiophilic oxides (FeO and CuO) granular layer and 3D porous structure, this novel skeleton can be used as a current collector to achieve a high-stability of Li metal anode. A dendrite-free deposition morphology Li metal anode is obtained with noticeable cycling stability up to 1000 h (2500 cycles) at 5 mA cm−2 current density with 1 mA h cm−2 capacity. This skeleton is used to assemble the full-cell with the commercial LiCoO2 (LCO) cathode. A stable full-cell is obtained with 87.2 % capacity retention after 500 cycles at 0.5C. The microwave-induced synthesis method in this work can prepare 3D lithiophilic skeleton in a brief period, which provides guidance for the design of Li metal anode.

CORROSION RESISTANCE OF GALVANIC NICKEL DEPOSITS AND ELECTROCHEMICAL ACTIVITY OF THEIR CORROSION PRODUCTS

Background. Bright galvanic nickel coatings, with high sulphur content, are less corrosion resistant than matte. Bright nickel coatings are particularly susceptible to corrosion damage in conditions that simulate tropical humid climates and are characterized by the presence of acetic acid vapours. Objective. The purpose of the paper is to investigate: corrosion resistance of galvanic nickel deposits in concentrated acetic acid and its vapours, electrochemical activity of sulphide-containing corrosion products of bright nickel coatings. Methods. Potentiodynamic and cyclic volt-amperometry have been used to study the electrochemical activity of galvanic nickel deposits and their corrosion products. The corrosion rate of galvanic nickel deposits has been determined by gravimetric method. Investigation of surface morphology and composition of galvanic deposits were performed using scanning electron microscopy and X-ray fluorescence analysis. Results.The increased electrochemical activity of sulphide corrosion products of bright nickel coatings is evidenced by an order of magnitude higher cathodic current densities of CVA curves obtained in acetate buffer solutions, in comparison with bright and matte nickel galvanic deposits. It has been shown that at the deposition of sulphide corrosion products of bright nickel coatings on matte nickel foil the corrosion rate of last one increase at the exposition in concentrated acetic acid and its vapours. Conclusions. Significant intensifying effect of sulphur on the corrosion of galvanic nickel deposits in concentrated acetic acid and its vapours has been established. In particular, this can be explained by the decomposition of nickel sulphide (which incorporates in the coating) in acetic acid. Sulphur in the oxidation state (-2) interacts with passive oxide coatings to form an adsorbed monolayer, which leads to the transition of nickel to the active state. Further research will focus on a deeper study of the electrochemical properties of corrosion products of bright nickel coatings.

Modeling the effects of pulse plating on dendrite growth in lithium metal batteries

The formation of dendrites on lithium electrodes presents safety and cycling challenges for the development of high-performance, rechargeable lithium metal batteries. While a constant current (CC) charging protocol has been standard, recent studies have shown that a pulse plating (PP) charging protocol is effective at reducing dendrite growth and improving cycle life. In this study, dendrite growth at the anode-electrolyte interface was simulated using an Extended Butler-Volmer Smoothed Particle Hydrodynamics (eBV-SPH) model implemented in LAMMPS. Square waveform PP protocols were implemented and compared to CC results to understand the effect of charging protocols on lithium deposition and dendrite morphology. The charging conditions were controlled by the applied potential, as the model does not currently enforce galvanostatic conditions. Past studies compared CC and PP results at a single charging current density. In similar work on lithium-ion batteries, PP and CC results compared at the identical mean current resulted in little to no benefit to cycling performance. In this investigation, lithium anode PP protocols performed worse when compared with CC plating at the identical mean current. The PP and CC simulation results from the eBV-SPH model simulated the expected morphology and behavior found in experimental investigations and provide more detailed morphologies than previous computational simulations.

Analisis Penyebaran Aspal Buton Berdasarkan Data Bor Di Daerah Lawele

Buton asphalt is a natural asphalt on Buton Island, Southeast Sulawesi. To meet the target of Buton asphalt production, it is necessary to develop an area in the Lawele area as one of the asphalt producing areas on Buton Island. The purpose of this study was to determine the distribution of Buton asphalt and the form of asphalt deposits in the Lawele area, Buton Regency. The research methodology is divided into literature study, data collection, data processing, analysis and discussion and conclusions. The data used in this research is drill data which includes coordinates, elevation, lithology type, thickness, and depth of drill point. Data processing and analysis in this study was carried out through lithological correlation using RockWorks 17 software. Lithological correlation was carried out to determine the continuity of the asphalt layer from one drill point to another drill point. Based on the results of the analysis on the cross-sectional correlation that has been carried out, it can be concluded that the direction of distribution of asphalt deposits in the research area in line 1 and line 3 is from west to east with a tabular morphology of asphalt deposits, while on line 2 is single deposit and asphalt seepage is found.

Evaporative Deposition of Surfactant-Laden Nanofluid Droplets over a Silicon Surface.

Morphologies of evaporative deposition, which has been widely applied in potential fields, were induced by the competition between internal flows inside evaporating droplets. Controlling the pattern of deposition and suppressing the coffee-ring effect are essential issues of intense interest in the aspects of industrial technologies and scientific applications. Here, evaporative deposition of surfactant-laden nanofluid droplets over silicon was experimentally investigated. A ring-like deposition was formed after complete evaporation of sodium dodecyl sulfate (SDS)-laden nanofluid droplets with an initial SDS concentration ranging from 0 to 1.5 CMC. In the case of initial SDS concentrations above 1.3 CMC, no cracks were observed in the ring-like deposition, indicating that the deposition patterns of nanofluid droplets could be completely changed and cracks could be eliminated by sufficient addition of SDS. With the increase of the initial concentration of hexadecyl trimethylammonium bromide (CTAB), the width of the deposition ring gradually decreased until no ring-like structure was formed. On the contrary, with the increase of the initial Triton X-100 (TX-100) concentration, the width of the deposition ring gradually increased until a uniform deposition was generated. Moreover, when the initial TX-100 concentration was high, a "tree-ring-like" pattern was discovered. Besides, morphologies of evaporative pattern due to the addition of surfacants were qualitatively analyzed.