Glow Discharge Optical Emission Spectroscopy Research Articles

Exploring microstructural evolution, nitrogen depth profile, and dry wear performance in 31CrMoV9 steel through combined severe shot peening and plasma nitriding

The present study investigates the influence of severe shot peening (SSP) on the plasma nitriding behavior and sliding wear performance of 31CrMoV9 steel. Initially, the steel was austenitized at 880 °C, followed by oil quenching, and tempering at 520 °C for one hour. These samples were shot peened using high-carbon steel shots, resulting in an enhancement in surface hardness up to 447 HV, gradually converging to the initial martensitic hardness after 140µm depth. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) scrutinized the initial and surface treated martensitic samples. Afterward, the plasma nitriding treatments were carried out at temperatures of 400 °C, 450 °C, and 500 °C for 8hours in a 30% N2 + 70% H2 atmosphere and 300Pa pressure. Microhardness testing, SEM, XRD, and glow-discharge optical emission spectroscopy (GDOES) evaluated both plasma nitrided (PN) and severe shot peened/plasma nitrided (SSP-PN) samples. Cross-sectional SEM observations revealed compound layer thicknesses of approximately 2.8µm, 5.0µm, and 6.3µm for PN samples at 400 °C, 450 °C, and 500 °C, respectively. SSP-PN samples exhibited a substantial increase — roughly 71%, 44%, and 33% increase, respectively, compared to PN samples. GDOES analysis supported this trend and indicated enhanced nitrogen diffusion depth, particularly evident in SSP-PN samples at consistent temperatures. The XRD results showed the stability of Fe4N, Fe2-3N, and CrN phases at all three nitriding temperatures. Furthermore, the intensity of these phases increases with temperature and is augmented by the application of the SSP. Microhardness measurements indicated hardness escalation: from 775 HV to 980 HV at 400 °C, 932 HV to 1096 HV at 450 °C, and 1011 HV to 1205 HV at 500 °C due to SSP. Finally, the wear performance was investigated between the non-nitrided, SSP, PN, SSP-PN, samples. Initially, SSP led to decreased wear performance up to 500m, followed by improved behavior up to 1500m. At 400 °C, the SSP-PN sample exhibited a 12% lower wear rate than PN. At 450 °C and 1500m, the SSP-PN sample displayed a 24% reduction, while at 500 °C, it showed a 27% reduction compared to PN. SEM observations indicated abrasion as the primary wear mechanism across all samples. The overall results indicated a significant similarity in the nitrogen depth profile, hardness depth, and wear performance between the SSP-PN sample at 450 °C and the PN sample at 500 °C. The fact suggested a potential reduction of approximately 50 °C in the typical plasma nitriding temperature for 31CrMoV9 steel as a result of the SSP process.

Depth profiling of W[sbnd]Ta based fusion-relevant samples using picosecond laser ablation

This study presents a detailed picosecond LIBS analysis of WTa coatings on Molybdenum substrate with varying layer thicknesses for fusion relevant applications. Ps-LIBS is performed on three WTa layers; two without deuterium (∼7 μm thickness) and one with deuterium (∼1 μm thickness). The LIBS measurements are conducted under argon gas flow at 5±0.2 mbar pressure with different laser pulse energies (1 mJ, 3 mJ) and 100 spectra are recorded consecutively at one spot on the sample for different set of gate delay/gate width (200/200 ns, 300/300 ns, 450/450 ns). The obtained LIBS and Glow-Discharge Optical Emission Spectroscopy (GDOES) depth profiles are compared with the confocal microscopic measurements showing good agreement. Additionally, the ablation rate and layer thickness are calculated for different experimental conditions. The Calibration-Free LIBS approach is used for elemental analysis and the results are compared with GDOES results. The capability of ps-LIBS to quantify Ta in WTa alloy is explored for 2 at.% of Ta. However, due to higher ablation rate of laser and thin coating in WTaD sample, the layer is irradiated in few laser pulse and therefore, CF-LIBS analysis is not performed for it.

On the Construction of a Calibration Curve Using a Glow Discharge Emission Spectrometer for Measuring the Hydrogen Content in Zirconium Alloys

One of the main directions of modern activity of metrology researchers is to provide the real sector of the economy of the Russian Federation with reference materials that have no analogues in the country. The article discusses the research of highly efficient materials for fuel cladding (fuel elements) in the active zones of thermal reactors, the scope of which is wide. The purpose of the study is the development of samples of the composition of the zirconium alloy to establish and control the stability of the calibration curves of spectrometers when determining the mass fraction of hydrogen, provided that the metrological and technical characteristics of the reference material meet the requirements of the measurement procedure. The main methods for determining the hydrogen content in materials are analyzed. It has been established that the method of glow discharge optical emission spectroscopy has found the widest application. It has also been established that zirconium alloys are chosen as the main material in most cases.The need to create samples for constructing a calibration curve for spectrometers for measuring the hydrogen content in a zirconium alloy is noted. Samples of zirconium alloy Zr-1Nb (grade Э110) have been developed to construct a calibration curve using a glow discharge emission spectrometer for measurements with a mass fraction of hydrogen from 0.034 to 0.498 %. Calibration is carried out using the developed samples to obtain a calibration curve using the example of an emission glow discharge spectrometer of the GD Profiler2 type. The relative error of the hydrogen mass fraction obtained during calibration does not exceed ± 10 %.The practical significance of the study lies in the development of samples that can be used to calibrate spectrometers based on the method of glow discharge optical emission spectroscopy.

Addition of molybdate ions to the anodizing bath to improve the corrosion resistance of clad 2024-T3 alloy anodized in tartaric-sulfuric acid

In the present investigation molybdates ions (MoO4−2) were added to a tartaric‑sulfuric acid (TSA) bath, which was employed to anodize AA2024-T3 clad samples. The incorporation of Mo into the anodized layer was investigated by different techniques: X-ray photoelectron spectroscopy (XPS), glow-discharge optical emission spectroscopy (GDOES), Rutherford backscattering spectrometry (RBS) and scanning electron microscopy (SEM), while the corrosion resistance was evaluated by electrochemical impedance spectroscopy (EIS) techniques in neutral (0.5 M) and acidic (0.1 M, pH = 4.0) NaCl solutions. The different characterization techniques indicate that small amounts of the modifier were incorporated into the anodized layer, while the SEM analysis confirmed that the morphology of the layer was not changed, although it was thicker when anodized in the Mo containing bath. Evaluation of corrosion resistance by EIS in both media showed that samples anodized in the molybdate containing bath were more corrosion resistant and durable. Fitting results of the electric equivalent circuit indicate that this may be a consequence of a thicker barrier layer for these samples.

Formation of Li-Al LDH conversion layer on AA2024 alloy for corrosion protection

AA2024 aluminium alloy is widely used in the aerospace industry. However, it is known to be highly susceptible to localised corrosion, which is related to its complex microstructure, mainly the presence of numerous Cu-rich intermetallic particles. One of the effective solutions to increase their corrosion resistance relies on the formation of layered double hydroxide (LDH) based conversion coatings (CC). This investigation aims to understand how the conditions of in situ Li-Al LDH-CO32-/OH– CC growth affect their further protective ability. For that purpose, concentration of reactants (0.05–0.15 M Li2CO3), pH of the electrolyte (10–12), temperature (30–50 °C) and treatment time (15 min-30 h) were systematically varied. Additionally to that, NH4OH was applied as a chelating agent for the synthesis of Li-Al LDH-CO32-/OH– as well as for the pH control. The obtained protective coatings were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), glow discharge optical emission spectroscopy (GDOES), Raman spectroscopy, salt spray test (SST) and electrochemical impedance spectroscopy (EIS). Among all varied parameters, involvement of chelating agent was found to be the most efficient for the formation of a coating with the highest level of corrosion protection. This is attributed to the formation of soluble complexes between NH4OH and Cu, resulting in dissolution of the intermetallics. It also prevents further redeposition of Cu species and consequently, the formation of new highly active Cu cathodes on the AA2024 alloy surface.

Effect of Impurities on the Compatibility of Steels in Supercritical CO2 at 450°–650°C

Abstract Direct-fired supercritical CO2 (sCO2) power cycles are a pathway to low-CO2 fossil energy but contain O2 and H2O in the sCO2 from combustion. The effect of impurities on structural steels was investigated at 450°–650 °C in 30 MPa sCO2. The test matrix included 9 and 12%Cr ferritic-martensitic (FM) steels and conventional and advanced austenitic steels exposed for 1000–2000 h with and without additions of 1%O2 and 0.1%H2O to simulate the cycle after water removal. For FM steels, the mass gains and scale thicknesses were similar with and without impurities with the formation of thick, duplex Fe-rich scales in all cases including the observation that Fe2O3 only formed with 1%O2. For the austenitic steels, higher mass gains were observed at all temperatures with increased formation of Fe-rich oxides when impurities were added. Carbon ingress was assessed by bulk combustion analysis, glow discharge optical emission spectroscopy (GDOES) and measuring postexposure room temperature tensile properties. Bulk C content was strongly increased at 650 °C but not at 450° or 550 °C.

Effect of the Substrate Materials in the Fabrication of an Electrode Based on Mixed Nickel‐Iron Oxide Electrocatalyst

AbstractThe effect of different substrate materials in the fabrication of an electrode intended for use in the water oxidation reaction is investigated. The electrocatalyst is nickel‐iron oxide (NiFeOx) which is deposited by chronoamperometry on nickel, iron, titanium, and stainless steel substrates. The process of electrodeposition is optimized to achieve the lowest overpotential for the water oxidation reaction. The four electrodes are characterized by scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and glow‐discharge optical emission spectroscopy (GDOES) to describe the effect of the substrate on the nature of the electrocatalyst layer. Electrochemical tests in 1 m NaOH are applied on the four electrodes to assess the stability and the retention of the electrocatalytic properties of the whole electrode. All electrodes show similar overpotential of ≈0.3 V at 10 mA cm−2 implying that the substrate do not affect the electrocatalytic activity of the NiFeOx. After use, the overpotential increases in a range of 30–50 mV for nickel, iron, and titanium substrates, while stainless steel retains the lowest overpotential with an increase of 10 mV. This limited variation can be the effect of smaller NiFeOx nanoparticles compared to other substrates. XPS analysis reveals that after galvanostatic electrolysis, the oxidation state of Fe shifts slightly from Fe(II) to Fe(III), likely Fe3O4 and Fe2O3, while NiO/Ni2O3 change partially to Ni(OH)2.

Corrosion of Stainless Steel in Simulated Nuclear Reactor Primary Coolant-Experiments and Modeling.

In the present paper, the effect of the evolution of primary water chemistry during power operation on the corrosion rate and conduction mechanism of oxide films on stainless steel is studied by in situ impedance spectroscopy at 300 °C/9 MPa during 1-week exposure periods in an autoclave connected to a recirculation loop. At the end of the exposure period, the samples were anodically polarized in a wide range of potentials to evaluate the stability of the passive oxide. Separate samples of the same steel were simultaneously exposed to the coolant and subsequently analyzed by glow discharge optical emission spectroscopy (GDOES) in order to estimate the thickness and the in-depth composition of the formed oxides. Impedance data were quantitatively interpreted using the mixed-conduction model for oxide films (MCM) to estimate the rates of metal oxidation at the alloy/oxide interface, oxide dissolution and restructuring at the film/coolant interface, and ion transport in the protective corrosion layer.

Statistical methods for linking material composition to recombination losses in optoelectronic devices.

In light of the accumulation of characterization measurement data in the industrial production of solar cell devices, the investigation of a large amount of samples by statistical means lends itself to be a useful tool to gain further insights into how the data correlate with performance parameters. However, due to the multicollinearity among high-dimensional input parameters of compositional data, revealing the underlying patterns may prove to be a difficult endeavor. In this work, we present statistics consisting of 280 thin-film solar cell samples based on Cu(In,Ga)(S, Se)2 absorber layers whose depth-resolved composition was assessed by glow-discharge optical emission spectroscopy (GDOES). After parameterization of the features of [Ga]/([Ga] + [In])and[S]/([S] + [Se]) gradings, we employ two-way clustering in order to group samples and features by their similarity. In addition, using principal component analysis, information in the dataset, which is irrelevant to the problem, is removed by dimensionality reduction. In this way, it is possible to create a map that provides an overview of the GDOES data of all samples in their entirety, including correlations among features. More importantly, it also opens up a more precise way to plan further improvements in the compositional gradings by unveiling a path along which the experimenter can read the feature changes concerned with an improvement in the open-circuit voltage deficit or any other target parameter of interest. New samples can then be assigned to existing cluster centroids to predict what target parameter value they would assume.

Influence of surfactant on conductivity, capacitance and doping of electrodeposited polyaniline films

The electrodeposition of polyaniline films is usually carried out in acid solutions such as hydrochloric acid, perchloric acid or sulfuric acid, and more rarely in organic acids such as camphorsulfonic acid (CSA). In this study, the impact of the presence of a surfactant in the electrolytic solution based on hydrochloric acid or CSA was evaluated by successively using anionic (sodium dodecyl sulfate, SDS), cationic (cetyltrimethylammonium bromide, CTAB), and non-ionic (Tritonx100) surfactants. Whatever the surfactant and the acid used, the electrochemical oxidation of aniline has successfully led to the formation of a thick polyaniline (PANI) film through a quasi-reversible reaction controlled by the diffusion of aniline monomers. The nature of the surfactant was shown to affect physico-chemical properties of the film, in particular its morphological features (morphology, thickness, roughness), electrochemical activity, specific capacitance, and conductivity. For example, PANI films containing SDS had a spongy morphology when PANI films containing Tritonx100 had a more fibrous and compact structure. Glow Discharge Optical Emission Spectroscopy (GDOES) experiments also highlighted differences depending on the acid used since chloride anions, from HCl, were present only on the top surface of the PANI films when camphorsulfonate anions were present everywhere throughout the polymer film, which impacts the doping process and electrochemical activity of the films. Moreover, the specific capacitance of the PANI/CSA films is higher and more sensitive to current density variation than the one of PANI/HCl films. Finally, electrochemical impedance experiments evidenced that the conductivity of PANI films electrodeposited from CSA solutions was much higher than the one of PANI films prepared from HCl solutions, and highly dependent on the nature of the surfactant, the most conductive films being obtained in the presence of SDS and Tritonx100. Therefore, the originality of this work comes from the possibility of modulating the conductivity, capacitance and electroactivity of electrodeposited polyaniline films using surfactants of different polarity, and from the determination of the distribution of ions in the films using the GDOES technique, which is rarely used to characterise organic films.

Characterization and In Vitro Behavior of PEO Coated Mg Modified with Antibacterial Ag(I) and Cu(II) Complexes.

The use of Mg-based biomaterials with a number of their advantageous properties are overshadowed by uncontrollable metal corrosion. Moreover, the use of implants goes alongside with the threat of pathogens-associated complications. In this study, PEO coated Mg biomaterial loaded with antibacterial Ag(I) and Cu(II) complexes is produced and tested to meet both appropriate protective characteristics as well as sufficient level of antibacterial activity. To achieve a suitable level of anticorrosion protection phosphate and fluoride-phosphate electrolytes are used in the PEO process. Investigation of the surface thickness and morphology done by means of cross-section analysis and scanning electron microscopy (SEM), as well as electrochemical impedance spectroscopy (EIS) assay show precedence of the fluoride containing PEO coating and make it the material of choice for further modification with Ag(I) and Cu(II) complexes. The presence of the complexes on the PEO surface is confirmed by energy dispersive X-ray spectroscopy (EDX). X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and glow discharge optical emission spectroscopy (GDOES) are used to estimate the complexes' chemical state and depth of penetration in the coating surface. Based on the results of antibacterial assay, the modified coatings are found to be active against both Gram-positive and Gram-negative bacteria.

A new approach to three-dimensional microstructure reconstruction of a polycrystalline solar cell using high-efficiency Cu(In,Ga)Se2

A new method for efficiently converting electron backscatter diffraction data obtained using serial sectioning by focused ion beam of a polycrystalline thin film into a computational, three-dimensional (3D) structure is presented. The reported data processing method results in a more accurate representation of the grain surfaces, reduced computer memory usage, and improved processing speed compared to traditional voxel methods. The grain structure of a polycrystalline absorption layer from a high-efficiency Cu(In,Ga)Se2 solar cell (19.5%) is reconstructed in 3D and the grain size and surface distribution is investigated. The grain size distribution is found to be best fitted by a log-normal distribution. We further find that the grain size is determined by the [Ga]/([Ga] + [In]) ratio in vertical direction, which was measured by glow discharge optical emission spectroscopy. Finally, the 3D model derived from the structural information is applied in optoelectronic simulations, revealing insights into the effects of grain boundary recombination on the open-circuit voltage of the solar cell. An accurate 3D structure like the one obtained with our method is a prerequisite for a detailed understanding of mechanical properties and for advanced optical and electronic simulations of polycrystalline thin films.

Inherent Antibacterial Properties of Biodegradable FeMnC(Cu) Alloys for Implant Application.

Implant-related infections or inflammation are one of the main reasons for implant failure. Therefore, different concepts for prevention are needed, which strongly promote the development and validation of improved material designs. Besides modifying the implant surface by, for example, antibacterial coatings (also implying drugs) for deterring or eliminating harmful bacteria, it is a highly promising strategy to prevent such implant infections by antibacterial substrate materials. In this work, the inherent antibacterial behavior of the as-cast biodegradable Fe69Mn30C1 (FeMnC) alloy against Gram-negative Pseudomonas aeruginosa and Escherichia coli as well as Gram-positive Staphylococcus aureus is presented for the first time in comparison to the clinically applied, corrosion-resistant AISI 316L stainless steel. In the second step, 3.5 wt % Cu was added to the FeMnC reference alloy, and the microbial corrosion as well as the proliferation of the investigated bacterial strains is further strongly influenced. This leads for instance to enhanced antibacterial activity of the Cu-modified FeMnC-based alloy against the very aggressive, wild-type bacteria P. aeruginosa. For clarification of the bacterial test results, additional analyses were applied regarding the microstructure and elemental distribution as well as the initial corrosion behavior of the alloys. This was electrochemically investigated by a potentiodynamic polarization test. The initial degraded surface after immersion were analyzed by glow discharge optical emission spectrometry and transmission electron microscopy combined with energy-dispersive X-ray analysis, revealing an increase of degradation due to Cu alloying. Due to their antibacterial behavior, both investigated FeMnC-based alloys in this study are attractive as a temporary implant material.

Observation of preferential sputtering of Si/graphite anodes from Li-ion cells by GD-OES and its validation by neutron depth profiling

Although the loss of Li inventory (LLI) is a common aging mechanism in Li-ion batteries, there are only few methods capable of comprehensive depth profiling within the bulk of the electrode to locate the residual Li. Two post-mortem analytical methods, which can be used to obtain quantified Li depth profiles to depths greater than 10 μm from the electrode surface are neutron depth profiling (NDP) and glow discharge optical emission spectroscopy (GD-OES). In this work, the validation of GD-OES using NDP by examining the Si/graphite anodes of cylindrical 21700 cells is presented. One anode was in a pristine/fresh state, two anodes were aged to the state of health (SOH) 90% and 76% at 45 °C respectively, and suffered from heavy solid electrolyte interphase (SEI) growth, and the fourth anode was aged to SOH 60% at 0 °C and exhibited Li plating. It is demonstrated that Li plating leads to a faster sputter rate of the Li-rich anode surface. An adapted method is introduced to incorporate the changing sputter rate into the depth profile calculation. For the aged anodes, the progressive aging of the anodes leads to a higher amount of irreversibly bound Li on the anode surface.

Effect of Cu2+ on deposition mechanism and structure of ZrO2-based conversion coatings on AA6060 aluminium alloys and their susceptibility to filiform corrosion

Zirconium oxide-based conversion coatings (CCs) were prepared from hexafluorozirconic acid, H2ZrF6, with and without CuII as an additive. The CCs were prepared on primary and recycled AA6060. The deposition mechanism, structure, electrochemical properties and effectiveness in protection against filiform corrosion (FFC) have been explored. In presence of CuII additives, a two step deposition mechanism is observed, evidenced by open circuit potential measurements and in situ dynamic electrochemical impedance spectroscopy. Copper deposits predominantly as copper(II) hydroxyfluoride on the top surface, and metallic Cu0 at the metal/CC interface, as evidenced by x-ray photoelectron spectroscopy and glow-discharge optical emission spectroscopy. The presence of a CuII additive induces a different distribution of the ZrO2-based products. After deposition of a weak organic model coating, aluminium pretreated with the CuII-containing system shows a 10%–30% lower maximum filament length compared to the CuII-free system in FFC tests, despite a ca. one order of magnitude higher cathodic activity of the former.

Analysis of hydrogen in a hydrogenated, 3D-printed Ti–6Al–4V alloy by glow discharge optical emission spectroscopy: sample heating effects

In the analysis of hydrogen in a hydrogenated, 3D-printed Ti–6Al–4V alloy by GDOES, hydrogen diffuses from the depth due to sample heating, enters the plasma and affects the signal response. A model of heat conduction within the sample is presented.

Concomitant ion matrix effects in SCGD-OES enhanced with formic acid

SCGD-OES is an attractive approach for on-line and in situ elemental analysis. This communication deals with concomitant ion matrix effects, especially if formic acid is added to improve sensitivity, and including a brief mechanistic discussion.

Deposition Mechanism, Structure and Corrosion Protection of ZrO2-Based Conversion Coatings on AA6060 Primary and Recycled Aluminum Alloys

Chemical conversion coatings (CC) are amongst the most common surface pretreatments for aluminium alloys before further organic coating steps. The presence of a conversion layer can increase the resistance towards underpaint corrosion such as filiform corrosion (FFC). Here we explore the deposition mechanism, structure and protective properties against FFC of a ZrO2-based CC on AA6060 aluminium alloy by means of electrochemical techniques as open circuit potential measurements, potentiodynamic polarization and dynamic electrochemical impedance spectroscopy (dEIS). Surface composition and elemental distribution are characterized by X-ray photoelectron spectroscopy (XPS), Glow Discharge Optical Emission Spectroscopy (GD-OES) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The variation of important parameters such as charge transfer resistance and capacitance during the conversion layer deposition gives insight into the deposition mechanism. GD-OES and XPS shed light into the structure and composition of the formed CC layer constituted of a mixture of Zr (hydr)oxides based products, redistribution of alloy elements and the nature of deposited additives. Finally, FFC tests reveal a comparable performance between primary and recycled alloys.

Analysis of Pre-Treatment Processes to Enable Electroplating on Nitrided Steel

Nitrided steel is being used to increase the lifetime and wettability of selective soldering nozzles. In this environment, the liquid solder wets to the surface of the nozzle to enable control of the solder flow during the soldering process. Pre-treatment is a key step in the processing of parts for electroplating. Pre-treatment usually involves degreasing and acidic pickling steps in order to remove adsorbed oil-based compounds and oxides respectively. These steps ensure a well-structured and adherent electroplated coating to the part.Surface treatments such as nitriding alter the surface composition of steels and thereby change the conductivity/surface activity. Typically, a nitrided surface contains a dual-phase surface layer followed by a diffusion zone consisting of the formed nitrides and finally a transition zone to the bulk material. Generally, this surface treatment is performed to harden materials without the risk of dimensional changes. For a selective soldering application, it reduces the dissolution of material into the solder during operation while also improving the wetting of the nozzle.The electroplated coatings for the selective soldering nozzles consist of 10 microns of nickel and 10 microns of tin. This structure allows for near-instant wetting and use of the nozzle. Furthermore, the electroplated layers provide corrosion protection for the nozzle ensuring no oxide or scale layers will form that may require flux for cleaning.A range of chemical and electrochemical pre-treatment steps were explored to prepare and optimally activate the nitride-hardened steel surfaces for electroplating. The processes included: hot degreasing and electrolytic degreasing with alkaline detergents; electrolytic descaling in a solution containing sodium hydroxide; chemical pre-descaling process with potassium permanganate; varying the compositions of pickling in inorganic acids; different formulations for nickel strike electrolytes for plating onto ferrous alloys.Mass loss measurements provided an estimation of the thickness of the material removed due to acid pickling. Scanning electron microscopy was employed to assess changes in the surface due to the pre-treatment. Open circuit potential measurements were applied to measure the surface activity before any pre-treatment and also the change in surface conductivity/activity post-treatment. Nanoindentation measurements were used to assess the change in surface hardness as a result of the nitriding treatment and also to check for the presence of the remaining hardened nitrided layer after pre-treatment. Glow discharge optical emission spectroscopy was utilised to study the elemental depth profile of the nitrided parts. Crystalline structure was studied through x-ray diffraction. After pre-treatment, a Woods nickel strike was applied to prepare the surface for further electroplating with bright tin. SEM analysis of the cross-sections of the coated specimens was used to analyse the coating microstructure. Thickness of the electrodeposited coatings were confirmed with x-ray fluorescence. Thermal shock tests were performed to confirm that the adhesion of the coating was sufficient.Approximately half of the nitrided layer was removed by pre-treatment in order to activate the surface for electroplating. More severe pre-treatment was required compared to electroplating non-hardened parts to activate the surface. Surface conductivity/surface activity was altered as measured by OCP resulting from the pre-treatment.This work has analysed the surface modification of nitride-hardened steels during the pre-treatment steps required to initiate electroplating and has shown that it is possible to prepare nitride-treated steels for electroplating. The results can be used to develop more optimal pre-treatment processes for electroplating nitrided steels.

(Invited) Lithium Plating as a Critical Ageing Mechanism in Lithium-Ion Batteries – Detection by Advanced Methods and Mitigation

The cycle life of Li-ion batteries is limited by aging on the material and electrode level. Prolonging the battery life helps increasing sustainability, reducing the dependency from critical raw materials, and safes costs. The first step in extending battery life is to understand the underlying degradation mechanisms. Post-Mortem analysis of commercial and pilot-line made cells showed that Lithium plating is a very relevant and severe aging mechanism which can lead to high aging rates and decrease safety properties.1 In this talk, we analyse the aging mechanism of Lithium plating on cell and electrode level.On cell level, capacity fade per time yields aging rates, which are temperature dependent. This temperature dependency is analyzed via Arrhenius plots. The Arrhenius plots for cycling aging show a typical V-shape with a low and a high temperature branch.2–4 A minimum in the Arrhenius plot corresponds to the maximum cycle life of the battery, while the low temperature branch indicates Lithium plating. Interestingly, the minimum in the Arrhenius plot shifts with the charging C-rate, the battery type,3,4 and – in case of non-linear capacity fade curves – with aging.4 In the last years, our group developed new semi-quantitative methods based on glow discharge optical emission spectroscopy (GD-OES) depth profiling for detection of Lithium plating on graphite5 and on Si/graphite composite anodes.6 Furthermore, a new in situ optical microscopy method with cross-sectioned full cells allows direct observations of the electrodes during charging and discharging.7,8 The color change of lithiated graphite in combination with simultaneous electrochemical data gives insight into the charging behavior of anodes. Under slow charging conditions (0.1C), the lithiation of the anode is observed to be homogeneously. Most interestingly, at 1C transport limitations come into play and lithiation fronts moving from the anode surface to the current collector can be directly observed and quantified by image analysis. Our results of both methods5,6,8 and in full consistence with simulations by others9 show that Lithium is mainly deposited on the anode surface, i.e. near the separator (see Figure).Finally, we show that Lithium deposition can be prevented by avoiding anode potentials < 0 V vs. Li/Li+ in commercial cells and cells from our pilot-line. Interestingly, Si/graphite anodes in pouch full cells show a lower susceptibility to Lithium plating at low temperatures with increasing Si content and the same anode areal capacity and N/P ratio. This suggests that the transport limitations in the pores of these Si/graphite anodes are reduced due to lower anode coating thickness. References T. Waldmann, B.-I. Hogg, and M. Wohlfahrt-Mehrens, J. Power Sources, 384, 107–124 (2018).T. Waldmann, M. Wilka, M. Kasper, M. Fleischhammer, and M. Wohlfahrt-Mehrens, J. Power Sources, 262, 129–135 (2014).X.-G. Yang and C.-Y. Wang, J. Power Sources, 402, 489–498 (2018).G. Kucinskis et al., J. Power Sources, 549, 232129 (2022).N. Ghanbari, T. Waldmann, M. Kasper, P. Axmann, and M. Wohlfahrt-Mehrens, J. Phys. Chem. C, 120, 22225–22234 (2016).M. Flügel, K. Richter, M. Wohlfahrt-Mehrens, and T. Waldmann, J. Electrochem. Soc., 169, 050533 (2022).C. Hogrefe et al., J. Electrochem. Soc., 169, 050519 (2022).C. Hogrefe, T. Waldmann, M. Hölzle, and M. Wohlfahrt-Mehrens, J. Power Sources, 556, 232391 (2023).S. Hein and A. Latz, Electrochimica Acta, 201, 354–365 (2016). Acknowledgement The authors would like to acknowledge the Federal Ministry for Economic Affairs and Climate Action (BMWK) for financial support of the Structur.e project (03ETE018E), the German Federal Ministry of Education and Research (BMBF) for funding of the project CharLiSiKo (03XP0333A) and the TEESMAT project (Horizon 2020 E.U. Framework Program, Grant Agreement N° 814106, http://www.teesmat.eu). Figure 1