Surface Degradation Mechanisms Research Articles

Ni-Cu Alloyed Austempered Ductile Iron Resistance to Multifactorial Wear

The paper provides a discussion on the results of studies of the effect exerted by combined degradation factors typical of four types of wear: abrasion, impact–abrasion, tribocorrosion, and impact–abrasion–corrosion, conducted for chain wheels made of Ni-Cu alloyed austempered ductile iron. The studies consisted of determining the content of retained austenite in the structure of the cast irons in question, establishing the measures of wear following wear testing, and identifying the basic surface degradation mechanisms observed in the chain wheels tested following multifactorial wear processes. The chain wheels made of ADI were found to have sustained the greatest damage under the impact–abrasion–corrosion (three-factor) wear scenario, while the wear was least advanced in the abrasion (one-factor) wear case. Another observation derived from the studies is that the combined effect of dynamic forces, corrosion, and quartz sand-based abrasives causes increased surface degradation in the cast iron grades taken into consideration compared to processes characterised by a reduced number of degradation factors (i.e., one- or two-factor wear processes). Additional hardness tests and XRD analyses revealed that a distinctive effect attributable to combined degradation factors on the surface hardness increased value and implied that bench testing was followed by phase transition.

Dynamical evolution of CO2 and H2O on garnet electrolyte elucidated by ambient pressure X-ray spectroscopies

Garnet-type Li6.5La3Zr1.5Ta0.5O12 (LLZO) is considered a promising solid electrolyte, but the surface degradation in air hinders its application for all-solid-state battery. Recent studies have mainly focused on the final products of the LLZO surface reactions due to lacking of powerful in situ characterization methods. Here, we use ambient pressure X-ray spectroscopies to in situ investigate the dynamical evolution of LLZO surface in different gas environments. The newly developed ambient pressure mapping of resonant Auger spectroscopy clearly distinguishes the lithium containing species, including LiOH, Li2O, Li2CO3 and lattice oxygen. The reaction of CO2 with LLZO to form Li2CO3 is found to be a thermodynamically favored self-limiting reaction. On the contrary, the reaction of H2O with LLZO lags behind that of CO2, but intensifies at high pressure. More interestingly, the results provide direct spectroscopic evidence for the existence of Li+/H+ exchange and reveal the importance of the initial layer formed on clean electrolyte surface in determining their air stability. This work demonstrates that the newly developed in situ technologies pave a new way to investigate the oxygen evolution and surface degradation mechanism in energy materials.

A Perspective on the Requirements of Ni‐rich Cathode Surface Modifications for Application in Lithium‐ion Batteries and All‐Solid‐State Lithium‐ion Batteries

AbstractThe increasing adoption of Ni‐rich cathode active materials in commercial liquid electrolyte Lithium‐ion batteries (LIBs) is testament to the improvements in the cathode stability through various surface modification strategies. The development of a deeper understanding of the cathode/electrolyte interface in LIBs has resulted in coatings capable of mitigating both surface and bulk cathode degradation mechanisms. However, due to increasing demands for safe and high energy density cells, a large portion of the research has now shifted towards applying Ni‐rich cathode active materials in inherently safer all‐solid‐state Lithium‐ion batteries (ASSLBs), with the resulting cathode surface modification strategies evolving differently. In this regard, a review outlining the surface modification strategies of Ni‐rich cathode materials applied in both LIB and ASSLB systems is provided. Within, a review of the traditional, advanced and specialized surface modification strategies of each system is discussed, along with a final perspective on the likely future direction of research regarding the design of system‐specific Ni‐rich cathode‐based surface modification strategies.

Synthesis of bio‐based poly(butylene carbonate‐co‐glycolic acid) with tunable degradation rate and mechanical properties

AbstractBio‐based copolymers with excellent mechanical properties and biodegradability are highly desired for packaging and agricultural applications. In this work, a series of high molecular weight bio‐based poly(ester‐carbonate)s are synthesized using glycolic acid (GA), dimethyl carbonate (DMC), and 1,4‐butanediol (BDO). The intrinsic viscosity ([η]) of these copolymers ranges from 0.70 to 1.11 dL/g. The tensile strength, elastic modulus, and elongation at break of PBCGA10 are 19.69 ± 2.40 MPa, 151.20 ± 37.17 MPa, and 1173 ± 142%, respectively, which are superior to the mechanical properties of PBAT. The degradation weight loss of PBCGA10 and PBCGA20 after 30 days can reach 8% and 40%, respectively, indicating excellent degradation performance of the copolymers. Moreover, copolymers undergo degradation through a surface degradation mechanism. The main products of copolymer degradation are BDO, CO2, and H2O, which do not cause harm to organisms and the environment.

Surface engineering for stable electrocatalysis.

In recent decades, significant progress has been achieved in rational developments of electrocatalysts through constructing novel atomistic structures and modulating catalytic surface topography, realizing substantial enhancement in electrocatalytic activities. Numerous advanced catalysts were developed for electrochemical energy conversion, exhibiting low overpotential, high intrinsic activity, and selectivity. Yet, maintaining the high catalytic performance under working conditions with high polarization and vigorous microkinetics that induce intensive degradation of surface nanostructures presents a significant challenge for commercial applications. Recently, advanced operando and computational techniques have provided comprehensive mechanistic insights into the degradation of surficial functional structures. Additionally, various innovative strategies have been devised and proven effective in sustaining electrocatalytic activity under harsh operating conditions. This review aims to discuss the most recent understanding of the degradation microkinetics of catalysts across an entire range of anodic to cathodic polarizations, encompassing processes such as oxygen evolution and reduction, hydrogen reduction, and carbon dioxide reduction. Subsequently, innovative strategies adopted to stabilize the materials' structure and activity are highlighted with an in-depth discussion of the underlying rationale. Finally, we present conclusions and perspectives regarding future research and development. By identifying the research gaps, this review aims to inspire further exploration of surface degradation mechanisms and rational design of durable electrocatalysts, ultimately contributing to the large-scale utilization of electroconversion technologies.

(Invited) Proton Surface Exchange Kinetics and Stability of Thin-Film Triple Conducting Oxides for Protonic Ceramic Electrolysis Cells

Protonic ceramic electrolysis cells (PCECs) have been attracting attention due to their ability to operate in the intermediate temperature (300 - 500 ˚C) sweet-spot. These temperatures enable fast kinetics, inexpensive materials (no precious metals; stainless interconnects), and lower operating voltage for producing green hydrogen, without the accelerated degradation that may be observed at higher temperatures. The steam electrodes often support triple conduction and thereby host the proton exchange / oxygen evolution process at the surface, where steam is split. Steam electrode materials development is at a relatively early stage, with open questions around the relationships among bulk composition, evolving surface chemistry, kinetic quantities, and degradation mechanisms. We are investigating the proton exchange surface coefficient (k) and its evolution over time on model thin film electrodes in order to ultimately develop highly active and long-term stable steam electrodes for PCECs.ABO3 perovskites with Ba on the A-site and nominally multivalent ions on the B-site are candidates for steam electrodes given the varied compositions in this class that can transport oxide ions, protons, and electronic species, and the lowering of hydration enthalpies by the basicity introduced by Ba. However, very few measurements of k exist for these materials, and the evolution of surface chemistry and thus k is poorly understood.In this work, we fabricated and compared two perovskite triple conducting oxides by growing geometrically well-defined films of Ba(Pr,Y)O3-x (BPY) and Ba(Co,Fe,Zr,Y)O3-x (BCFZY) with pulsed laser deposition. We examined the proton surface exchange coefficients (k-values) using simultaneous in-situ optical transmission relaxation and electrical conductivity relaxation measurements upon switching pH2O at a temperature of 400 ˚C, and continued these switches as a function of time to assess stability. To our knowledge, this is the first use of an optical transmission method to probe elevated temperature steam splitting kinetics, and we interpret the optical (and electrical) changes as indicative of redox during the hydrogenation process. The k-values of BPY thin films were approximately ten times higher than those of the BCFZY thin films, and BPY also retained higher k-values over time. The bulk and surface chemical compositions of BPY and BCFZY thin films before and after relaxation measurements were compared using Rutherford backscattering spectrometry, angle-resolved X-ray photoelectron spectroscopy, and scanning transmission electron microscopy with spectroscopy. Pronounced Ba enrichment and Si contamination (from the quartz tube) were evident at the surface of BPY by both S/TEM-EDS and XPS, whereas for BCFZY these surface chemical features were only detectable by XPS and absent in S/TEM-EDS. Implications for materials design of steam electrodes will be discussed, considering efficiency and lifetime.

In Situ EC-AFM Study of the Initial Stages of Cathodic Corrosion of Pt(111) and Polycrystalline Pt in Acid Solution.

An atomic scale understanding of the surface degradation mechanism during cathodic corrosion of a platinum electrode is still lacking. Here, we present results of surface structural changes observed during cathodic polarization of a polycrystalline Pt electrode and single crystalline Pt(111) in acid electrolytes in the absence and presence of cations (Na+) by in situ electrochemical atomic force microscopy (EC-AFM) imaging. The electrolyte cation is proved to be a prerequisite to trigger cathodic etching of the polycrystalline Pt surface. Further examination of the evolution of electrochemical signals and distinct surface structural transformations of an atomically defined Pt(111) single-crystal electrode during cathodic corrosion reveals clearly that the roughening process commences at the under-coordinated sites of the Pt(111) surface. The created triangular-shape pattern, actually a 100-oriented pit in a 111-terrace, grows primarily laterally in the initial regime, while prolonged cathodic corrosion leads to the existing etching pits growing in depth until ultimately they coalesce with each other, generating a highly roughened surface.

Surface Rearrangement and Sublimation Kinetics of Supported Gold Nanoparticle Catalysts

Heterogeneous catalysts consisting of supported metallic nanoparticles typically derive exceptional catalytic activity from their large proportion of undercoordinated surface sites which promote adsorption of reactant molecules. Simultaneously, these high energy surface configurations are unstable, leading to nanoparticle growth or degradation and eventually a loss of catalytic activity. Surface morphology of catalytic nanoparticles is paramount to catalytic activity, selectivity, and degradation rates, however it is well-known that harsh reaction conditions can cause the surface structure to change. Still, limited research has focused on understanding the link between nanoparticle surface facets and degradation rates or mechanisms. Here, we study a model Au supported catalyst system over a range of temperatures using a combination of in situ transmission electron microscopy, kinetic Monte Carlo simulations, and density functional theory calculations to establish an atomistic picture of how variations in surface structures and atomic coordination environments lead to shifting evolution mechanisms as a function of temperature. By combining experimental results, which yield direct observation of dynamic shape changes and particle sublimation rates, with computational techniques, which enable understanding the fundamental thermodynamics and kinetics of nanoparticle evolution, we illustrate a two-step evolution mechanism in which mobile adatoms form through desorption from low-coordination facets and subsequently sublimate off the particle surface. By understanding the role of temperature in the competition between surface diffusion and sublimation, we are able to show how individual atomic movements lead to particle scale morphological changes and rationalize why sublimation rates vary between particles in a system of nearly identical nanoparticles.

A comparative study on the surface degradation mechanisms of arc melted and laser remelted CoCrFeNiAl0.5Nb0.5 HEA

In the current study, a CoCrFeNiAl0.5Nb0.5 high entropy alloy was manufactured via arc melting and exposed to laser surface remelting. The presence of Nb and Al was limited to the formation of single simple cubic phase formations. Both alloys are composed of four phases. Laser remelting did not change current phases, but it affected the microstructure. Hardness increased from 475 HV to 785 HV thanks to the change in phase ratios and grain refinement resulting from laser remelting. Wear resistance improved due to the increase in hardness, and volume losses decreased by 28 %. In short-term high-temperature oxidation, laser remelting enabled better oxidation resistance in alloy since it provided more paths for the diffusion of aluminum, which forms an alumina oxide scale. Interestingly, such a trend was not observed in the increased oxidation period. In the final oxidation stage, the depletion of B2 phases and the formation of inner oxides significantly worsened the oxidation resistance of LR alloy. Although Icorr, which expresses the corrosion resistance of the laser-melted alloy, was higher than before the laser-remelting process, the changes in the alloy's microstructure with rapid cooling caused a decrease in the passivation resistance of laser-remelted CoCrFeNiAl0.5Nb0.5 HEA.

Degradation of atrazine in river sediment by dielectric barrier discharge plasma (DBDP) combined with a persulfate (PS) oxidation system: response surface methodology, degradation mechanisms, and pathways.

Single degradation systems based on dielectric barrier discharge plasma (DBDP) or persulfate (PS) oxidation cannot achieve the desired goals (high degradation efficiency, high mineralization rate, and low product toxicity) of degrading atrazine (ATZ) in river sediment. In this study, DBDP was combined with a PS oxidation system (DBDP/PS synergistic system) to degrade ATZ in river sediment. A Box-Behnken design (BBD) including five factors (discharge voltage, air flow, initial concentration, oxidizer dose, and activator dose) and three levels (- 1, 0, and 1) was established to test a mathematical model by response surface methodology (RSM). The results confirmed that the degradation efficiency of ATZ in river sediment was 96.5% in the DBDP/PS synergistic system after 10min of degradation. The experimental total organic carbon (TOC) removal efficiency results indicated that 85.3% of ATZ is mineralized into CO2, H2O, and NH4+, which effectively reduces the possible biological toxicity of the intermediate products. Active species (sulfate (SO4•-), hydroxy (•OH), and superoxide (•O2-) radicals) were found to exert positive effects in the DBDP/PS synergistic system and illustrated the degradation mechanism of ATZ. The ATZ degradation pathway, composed of 7 main intermediates, was clarified by Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS). This study indicates that the DBDP/PS synergistic system is a highly efficient, environmentally friendly, novel method for the remediation of river sediment containing ATZ pollution.

Investigating the Biodegradation Mechanism of Poly(trimethylene carbonate): Macrophage-Mediated Erosion by Secreting Lipase.

Poly(trimethylene carbonate) (PTMC), as one of the representatives of biodegradable aliphatic polycarbonates, has been found to degrade in vivo via surface erosion. This unique degradation behavior and the resulting nonacidic products make it more competitive with aliphatic polyesters (e.g., polylactide) in clinical practice. However, this surface degradation mechanism is complicated and not fully understood to date despite the findings that several reactive oxygen species and enzymes can specifically degrade PTMC in vitro. Herein, the biodegradation mechanism of PTMC was investigated by using possible degradation factors, distinct cell lines, and the inhibitors of these factors. The results demonstrate that PTMC undergoes a specific macrophage-mediated erosion. Macrophages tend to fuse into giant cells and elicit a typical inflammatory response by releasing proinflammatory cytokines. In addition, macrophages are suggested to primarily secrete enzymes (lipase specifically) to erode the PTMC bulk extracellularly as inhibiting their activity effectively prevented this eroding process. The clarification of the biodegradation mechanism in this work suggests that the degradation of PTMC highly depends on the foreign body response. Thus, it reminds the researchers to consider the effect of the microenvironment on the degradation and drug release of PTMC-based implantation devices and localized drug delivery systems.

Applications and Developments of Thermal Spray Coatings for the Iron and Steel Industry.

The steel making processes involves extreme and harsh operating conditions; hence, the production hardware is exposed to degradation mechanisms under high temperature oxidation, erosion, wear, impact, and corrosive environments. These adverse factors affect the product quality and efficiency of the steel making industry, which contributes to production downtime and maintenance costs. Thermal spray technologies that circumvent surface degradation mechanisms are also attractive for their environmental safety, effectiveness and ease of use. The need of thermal spray coatings and advancement in terms of materials and spray processes are reviewed in this article. Application and development of thermal spray coatings for steel making hardware from the molten metal processing stages such as electric arc and basic oxygen furnaces, through to continuous casting, annealing, and the galvanizing line; to the final shaping process such as cold and hot rolling of the steel strips are highlighted. Specifically, thermal spray feedstock materials and processes that have potential to replace hazardous hard chrome plating are discussed. It is projected that novel coating solutions will be incorporated as awareness and acceptance of thermal spray technology grows in the steel making sectors, which will improve the productivity of the industry.

Early Spalling Analysis of Large Particles in High-Cr Steel during Thermal Fatigue: Relevant Mechanisms.

The aim of this study was to investigate the surface deterioration of high-Cr roll steel caused by the spalling of larger particles during thermal fatigue. The mechanisms of surface deterioration due to spalling of larger particles are discussed. Using a laboratory thermal fatigue test that replicates hot rolling conditions, samples were tested cyclically (up to 4500 times) at maximum cycle temperatures of 500, 600 and 700 °C, followed by water cooling. Specimens with surface deterioration were selected for analysis, revealing important influencing parameters, i.e., the combination of test temperatures, chemical composition, thermal stress and microstructural properties, leading to oxidation-assisted crack growth in different directions and consequent surface deterioration due to early spalling of larger particles. Here, we describe the mechanisms of crack propagation, especially in the lateral direction, and their relation to the subsequent spalling of larger particles, which depend on the influence of the local chemical composition on the microstructural constituents, as well as their distribution and properties. The results obtained in this study can be used in the development of roll steel microstructures with improved resistance to the identified mechanisms of surface degradation.

Influence of Different Binders and Severe Environmental Conditions on the Tribological and Electrochemical Behaviour of WC-Based Composites

Cemented carbides are highly resistant to abrasion, erosion and sliding wear and are frequently used in drilling and cutting tool operations. In the present investigation, different submicrometric (0.8 µm) WC (tungsten carbide)-based composites were developed, containing various binders of Co, Ni, NiCr, NiMo, and NiCrMo. The main objective of the work was simultaneous tribological and electrochemical characterization to investigate the mechanisms of surface degradation when subjected to mechanical wear and how they interconnect with chemical or electrochemical processes and each other. By comparison with previous tribological tests, under dry sliding and the same contact conditions of load and frequency, it can be concluded that a synergistic effect was not observed and that the solution works mainly as lubrication, resulting in increased combined wear–corrosion resistance.

Reactive Molecular Dynamics Study for CO2 Electrocatalytic Conversion on Lmfcr (M= Sr, Ca) Perovskite-Based Solid Oxides

Due to their mixed conducting properties as well as their electronic, crystallographic, and chemical versatility, perovskite-based oxides have been shown to be very promising electrocatalysts for CO2 conversion to syngas in high temperature (600 – 1000 °C) solid oxide electrolysis cells (SOECs) integrated with renewable energy resources. In addition to generating fuels and value-added chemicals, CO2 reduction (CO2RR) in SOECs serves to lower atmospheric CO2 emissions. La-based (1) perovskite oxides have been intensively used instead of precious metals and metal-cermet materials (e.g., Ni-YSZ, Ni-GDC) for CO2 electrolysis in high temperature SOECs. The effect of the dopant cations on the electrocatalytic performance and degradation have also been investigated since the segregation of dopants can reconstruct the surface (2). Our team has been actively developing the family of La0.3a0.7Fe0.7Cr0.3O3−δ (LMFCr, where M = Ca or Sr) for CO2 reduction (3,4) showing that CO2RR is more active than CO oxidation, and that the catalyst is also highly active on the air side. More recently, we have shown that Fe-Ni exsolved LCFCr significantly improves the rate of CO oxidation (5), while hardly changed CO2RR. However, a full atomistic scale understanding of the CO2 reduction mechanism and related degradation issues, such as dynamic changes of the surface composition as a function of operating conditions, does not yet exist. The oxygen vacancy concentration (V0) and surface termination of the perovskite material are important factors that affect the CO2RR, as shown recently (6) utilizing DFT methods.In this study, we used Density Functional Theory (DFT) to explore the energetics of the catalytic conversion of CO2 to CO on LMFCr (M = Sr, Ca) perovskite surfaces. The DFT calculations were then used to generate datasets of optimized lattice structures, including point defects, equations of state, surface energies, and surface CO2/CO interactions in order to develop reactive force fields (ReaxFF). The datasets were optimized by using an evolutionary algorithm, CMA-ES, and validated in order to explore the dynamics of the catalytic conversion process under varying conditions, such as temperature, inlet CO2/CO gas ratio, the perovskite surface composition and applied electrical field.Our results have shed light on reaction steps involving adsorption of CO2 at high temperatures, C=O bond activation, and the dominant intermediates as transition states during the conversion process and their role in generating CO. These observations will serve as a foundation to determine the elementary reaction steps involved in the CO2 splitting mechanism on LMFCr at high temperatures. Furthermore, this study will enable us to determine the optimal conditions for the reaction to occur and shed light on possible surface degradation mechanisms, allowing future optimization of the stability and catalytic activity of these promising perovskites.ACKNOWLEDGMENTSThis computational research was supported by the Canada First Research Excellence Fund (CFREF), while the platforms for this computational work were provided by Westgrid (https://www.westgrid.ca) and Compute Canada (https://www.computecanada.ca). Thanks are also extended to Oliver Calderon and Misha Pidburtnyi for helpful discussions.References Cao, Z., Wei, B., Miao, J., Wang, Z., Lü, Z., Li, W., Zhang, Y., Huang, X., Zhu, X., Feng, Q. and Sui, Y., (2016). Efficient electrolysis in symmetrical solid oxide electrolysis cell with highly active 3Sr0.7Fe0.7Ti0.3O3 electrode material. Electrochemistry Communications, 69, 80-83.Zhang, Y. Q., Li, J. H., Sun, Y. F., Hua, B., & Luo, J. L. (2016). Highly active and redox-stable Ce-doped LaSrCrFeO-based cathode catalyst for CO2 SOECs. ACS Applied Materials & Interfaces,, 8(10), 6457-6463.Addo, P. K., Molero‐Sanchez, B., Chen, M., Paulson, S., & Birss, V. (2015). CO/CO2 study of high performance La0. 3Sr0. 7Fe0. 7Cr0. 3O3–δ reversible SOFC electrodes. Fuel Cells, 15(5), 689-696.Molero-Sánchez, B., Morán, E., & Birss, V. (2017). Rapid and Low-Energy Fabrication of Symmetrical Solid Oxide Cells by Microwave Methods. ACS Omega, 2(7), 3716-3723.Ansari, H. M., Bass, A. S., Ahmad, N., & Birss, V. I. (2022). Unraveling the evolution of exsolved Fe–Ni alloy nanoparticles in Ni-doped La 0.3 Ca 0.7 Fe 0.7 Cr 0.3 O 3− δ and their role in enhancing CO 2–CO electrocatalysis. Journal of Materials Chemistry A.Kozokaro, V. F., Addo, P. K., Ansari, H. M., Birss, V. I., & Toroker, M. C. (2020). Optimal Oxygen Vacancy Concentration for CO2 Reduction in LSFCr Perovskite: A Combined Density Functional Theory and Thermogravimetric Analysis Measurement Study. The Journal of Physical Chemistry C, 124(50), 27453-27466.

Understanding the nucleation and growth of the degenerated surface structure of the layered transition metal oxide cathodes for lithium-ion batteries by operando Raman spectroscopy

• The surface degradation process of the lithium-layered transition metal oxide cathode is revealed by an operando Raman spectroscopy study. • The degradation process is visualized by Raman mapping with the spectral window of ∼600 cm −1 . • The degradation process not only involves the structural changes, but also the growth and merging between the degenerated layers on charge–discharge. • The present study offers crucial information to counter the capacity decay of the NMC batteries. The well-defined layered structure for Li + (de)intercalation of transition metal oxide cathodes plays a crucial role in delivering high capacity for lithium-ion batteries. Therefore, structural deformations of the layered structure are often considered as the evidence of deterioration in the battery performance and stability. In this study, the surface degradation mechanism of the layered LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode is examined on charge–discharge using an operando Raman cell. We revealed the surface degradation process of the cathode with the A 1g Raman spectral window (∼600 cm −1 ) in the voltage range of 2.8–4.35 V, and proposed the nucleation-merging mechanism. The spectral shifts and mappings have been compared between the early-stage and later-stage cycles (≥15 cycles). It has been identified that the degradation process not only involves the structural changes (i.e., nucleation of the degenerated layers), but also the growth/merging between the degenerated layers during charge and discharge. This observation provides key information on how the reconstructed surface can expand during cycling.

Additive manufacturing technology: laser material processing and functionally graded materials

Professor Akinlabi’s research and her team has focused on the field of advanced and modern manufacturing processes like Laser Additive Manufacturing (AM), in particular laser material processing. Her other research work is focused on laser metal deposition and functionally graded materials of titanium-based alloys and other materials. Some of the studies she has been involved in focus on cladding titanium with titanium carbide for enhanced wear properties, the cladding of titanium alloy biological implants with hydroxyapatite (HAP) for improved osteo-integration, and the cladding of Grade 5 titanium alloy with copper for improved corrosion properties for marine applications. Akinlabi focuses her investigations on the development of advanced metallic coatings on Ti-6Al-4V substrate using additive manufacturing technology for improved surface performance; with targeted applications in the aerospace, automotive, and shipbuilding industries. This work makes a substantial contribution to knowledge by bringing the theoretical clarity and experimental studies required for the effective assessment of surface degradation mechanisms in additive manufactured Ti-6Al-4V alloy. This is ascribed to the elimination of high residual stresses and crack formation through the optimization of laser processing parameters, leading to enhanced quality of the coatings, surface adhesion between the substrate and the reinforcement materials, microstructural evolution and thus improved mechanical properties. Her research was developed to produce advanced innovative corrosion-wear resistant coatings with enhanced hardness, tribological property, and sustainable anti-corrosion performance thereby, consequently lengthening the lifespan and durability of titanium and its alloys, eliminating material loss and equipment damage, minimizing cost of maintenance, and reduced failure of this material. Despite all the benefits derived from AM technology, there are still a lot of unresolved issues with the technology that has hindered its performance and commercialisation thereby limiting its application to high tolerant utilizations. Professor Akinlabi research on additive manufacturing techniques had produced near-net-shape, light weight and high strength components which has gradually revolutionized the manufacturing sector. The use of the technology is now providing sustainable production benefits, as ability to repair and manufacture components can now be employed to increase product life circle. Against this background, the Additive Manufacturing technology is in itself referred to as a technology of the future despite its versatile applications in the industry. On the other hand, Functionally Graded Materials (FGMs) are advanced materials usually developed for specific and tailored applications. The FGMs also referred to as materials of the future as its applications are not yet fully explored for tailored applications. In this talk, Prof Akinlabi shared some of her research endeavours in the field of AM and FGMs, and also shared the scope on the primary objectives of the joint project which was to be undertaken on FGM of Titanium alloy and Titanium Carbide.

Insights and Findings Following 11 Years of Test Road Exploitation

Road pavement is one of the most important components of road structure. Long-term monitoring changes in the state of road pavement under real conditions of load and climate allows to determine surface degradation mechanisms, select sustainable road building materials and their mixes, rationally employ asphalt paving technologies, and improve quality control. For a number of years, road pavement structures have been studied that should best meet the Lithuanian climate conditions and withstand the increasing impact of vehicle load. Thus, for that purpose, specially designed, constructed and tested roads or road sections for different pavement structures are most appropriate. One of those was constructed in 2007. The experimental road (hereinafter, the Test Road) consisted of 27 different pavement structures (PSs) produced of various materials. The study aims to evaluate the effect of different materials on variations in the bearing capacity of the pavement structure (PS), the sustainability of the structure, and the formation of ruts in 2007–2018. In this way, difference in bearing capacity, rutting depth between sections, and loaded and unloaded lanes was estimated. Further, the statistical analysis of these factors was conducted. Investigations have shown that the minimum bearing capacity of 754 MPa established after 11 years did not affect the formation of rut depth that was less than 1.0 cm. The PSs covered with the used asphalt granules, a larger asphalt base course on gravel, the sand mix base course, and granite aggregate mixed with sand base course were accepted as one of the PSs with the highest bearing capacity with PSs exceeding 929 MPa. The bearing capacity of the PS containing a 20 cm aggregate base course is on average higher by 30 MPa than PS holding a 15 cm aggregate base course.

Multi-Length Scale Analysis of Individual NMC811 Particle Degradation Using X-Ray Computed Tomography

Due to issues with toxicity and price, many manufacturers are reducing the cobalt content within lithium-ion (Li-ion) batteries by moving towards nickel-rich cathode chemistries, such as layered nickel-manganese-cobalt-oxide LiNi0.8Nm0.1Co0.1O2 (NMC811). Increasing the Ni content is accompanied by higher theoretical capacities, as high as 275 mAh g-1. However, the complex degradation of this material is not fully understood (1)(2)(3) and consequently practical capacities can be significantly lower (~200 mAh g-1) and capacity retention can be low, e.g. ~70% over 100 cycles to 4.3 V vs. Li/Li+ (4). The cracking of electrode particles (5) is a prominent degradation mechanism, but in order to gain a more comprehensive understanding of its origins and propagation, a multi-scale approach is required (6).X-ray computed tomography (CT) has revolutionised the characterisation of energy materials as it enables the non-destructive imaging of microstructure in 3D (7) . In this work, the effect of cycle number, C-rate and upper cut-off voltage on the morphology of NMC electrodes and particles have all been investigated using lab-based X-ray CT. This was achieved through post-mortem 3D analysis of the samples using micro- and nano-CT to reveal the electrode and particle degradation across multiple length scales.The individual particles within the 3D tomograms (Figure 1) have been quantitatively and qualitatively assessed to build a comprehensive understanding of the electrode state of health for a wide library of electrochemical histories. This has been achieved through carrying out greyscale intensity analysis in 3D on individual particles, and comparing them across cycling conditions, size ranges and categorizing each particle through machine learning.Due to the number of particles assessed, this work presents unprecedented materials statistics with detail of the degradation of NMC811 from the electrode to sub-particle level. Here, we discuss the methodology and findings from the multi-length-scale study, investigating both the electrochemical and mechanical response due to the variations in voltage, C-rate and number of cycles, and the implications of this research on the Li-ion field. Birkl CR, Roberts MR, McTurk E, Bruce PG, Howey DA. Degradation diagnostics for lithium ion cells. J Power Sources 2017;341:373–86.Jung R, Morasch R, Karayaylali P, Phillips K, Maglia F, Stinner C, et al. Effect of Ambient Storage on the Degradation of Ni-Rich Positive Electrode Materials (NMC811) for Li-Ion Batteries. J Electrochem Soc. 2018;165(2):A132–41.Hwang S, Kim SY, Chung KY, Stach EA, Kim SM, Chang W. Determination of the mechanism and extent of surface degradation in Ni-based cathode materials after repeated electrochemical cycling. APL Mater 2016;4(9).Noh HJ, Youn S, Yoon CS, Sun YK. Comparison of the structural and electrochemical properties of layered Li[NixCoyMnz]O2 (x = 1/3, 0.5, 0.6, 0.7, 0.8 and 0.85) cathode material for lithium-ion batteries. J Power Sources. 2013;233:121–30.Tsai PC, Wen B, Wolfman M, Choe MJ, Pan MS, Su L, et al. Single-particle measurements of electrochemical kinetics in NMC and NCA cathodes for Li-ion batteries. Energy Environ Sci. 2018;11(4):860–71.Finegan DP, Tudisco E, Scheel M, Robinson JB, Taiwo OO, Eastwood DS, et al. Quantifying bulk electrode strain and material displacement within lithium batteries via high-speed operando tomography and digital volume correlation. Adv Sci. 2015;3(3):1–11.Shearing PR, Howard LE, Jørgensen PS, Brandon NP, Harris SJ. Characterization of the 3-dimensional microstructure of a graphite negative electrode from a Li-ion battery. Electrochem commun 2010;12(3):374–7. Figure 1

Microstructural influence of sigma phase on pitting corrosion behavior of duplex stainless steel/NaCl electrolyte couple

This study reports the effects of the sigma phase on pitting corrosion behavior of thermally-aged duplex stainless steel (DSS). Analysis via structural, morphological, and electrochemical characterizations was performed. The corrosion assessment includes a potentiodynamic test in 1 M NaCl solution at temperatures of 25, 40, and 65 °C. 3D roughness images were taken and compared for all the specimens before and after the corrosion test. The potentiodynamic test combined with the method of optical profilometry was found to be a successful approach to evaluate the evolution of surface degradation mechanisms due to pitting corrosion.