Microstructure Morphology Research Articles

Novel coated Si2N2O/SiO2 crucible for photovoltaic Si growth: Crystallization behavior and interaction with molten Si

The fused SiO2 crucible for photovoltaic (PV) Si growth can only be used once due to inevitable crystallization breakage and “Si ingot/crucible” adhesion, which lowers quality and yield of PV Si. In this work, novel Si2N2O/SiO2 crucible with α-Si3N4 coating was developed to realize inhibited crystallization and easy demolding. The results display that the high-temperature crystallization behavior was significantly inhibited by introducing 20 wt% Si2N2O into fused SiO2. After heating at 1450–1550 °C for 30min, the crystallinity of Si2N2O/SiO2 crucible was less than 8.85 wt%, which was at least 87.06 % lower than that of fused SiO2 crucible. After Si growth at 1550 °C for 1h, the crystallinity of Si2N2O/SiO2 crucibles was 79.23 % lower than that of fused SiO2 crucible. The above crystallization-inhibiting effect is attributed to the spatial barrier of Si2N2O and the in-situ formation of O-Si-N bonds with higher bind energy. Moreover, after Si growth, the coated Si2N2O/SiO2 crucible can maintain intact microstructure and macroscopic morphology due to inhibited crystallization and infiltration against molten Si. Therefore, this novel coated Si2N2O/SiO2 crucible has significant application prospects for re-usability in PV Si manufacture industry.

Analysis of Microstructural Changes, Morphology and Optical Properties of the Surface of Copper Oxide Thin Layers due to Annealing for Use in Optoelectronic Devices

Analysis of Microstructural Changes, Morphology and Optical Properties of the Surface of Copper Oxide Thin Layers due to Annealing for Use in Optoelectronic Devices

Research Paper on Analytical Investigation of the Effect of 3d Printing Process Parameters on Anisotropic Mechanical Behaviour of Additively Constructed Concrete

This research identifies key challenges in additively constructed concrete, including the need for understanding the scalability of mechanical behaviour from small to large structures, addressing variability in material properties, and predicting failure mechanisms. It highlights the need for improved finite element modelling for accurate 3DCP simulation, and further investigation into concrete foundation interactions and initial imperfections. The study acknowledges difficulties in simulating complex shapes and calls for refinement of the numerical model for better predictive accuracy. It also emphasizes the need to understand long-term behaviour, durability, and the impact of the 3DCP process on microstructural morphology and mechanical properties. The influence of pores and time gaps between layers on the overall capacity of the specimen, and the development of a model considering different properties of 3D concrete material are also identified as areas for future research.

A high-throughput statistical homogenization technique to convert realistic microstructures into idealized periodic unit cells

Abstract Metal alloys frequently contain distributions of second-phase particles that deleteriously affect the material
behavior by acting as sites for void nucleation. These distributions are often extremely complex and
processing can induce high levels of anisotropy. The particle length-scale precludes high-fidelity microstructure
modeling in macroscale simulations, so computational homogenization methods are often employed.
These, however, involve simplifying assumptions to make the problem tractable and many rely on periodic
microstructures. Here we propose a methodology to bridge the gap between realistic microstructures
composed of anisotropic, spatially varying second-phase void morphologies and an idealized periodic microstructure
with roughly equivalent mechanical response. We create a high-throughput, parametric study
to investigate 96 unique bridging methods. We apply our proposed solution to rolled AZ31B magnesium
alloy, for which we have a rich dataset of microstructure morphology and mechanical behavior. Our methodology
converts a μ-CT scan of the realistic microstructure to idealized periodic unit cell microstructures that
are specific to the loading orientation. We recreate the unit cells for each parameter set in a commercial finite
element software, subject them to macroscopic uniaxial loading conditions, and compare our results to the
datasets for the various loading orientations. We find that certain combinations of our parameters capture
the overall stress-strain response, including anisotropy effects with some degree of success. The effect of
different parameter options are explored in detail and we find that excluding certain particle populations
from the analysis can give improved results.

Design, Processing, Testing and Characterizing for Orthodontics Material of Palm-Fibres Based Bio-Nanocomposite

Current research is carried out for newly developed of Bio-CPNC biomaterial nanocomposite for dentistry applications. The developed Bio-CPNC is invented of clay-based polymer CPNC and palm-tree micro-fibers, where CPNC is composed by nanotechnology of HDPE and MMT nanoclay. The research contains the methodology of design, processing, testing and characterization mainly focusing on mechanical and fracture properties, microstructure morphology and testing of thermal effect changes due to surrounding temperature changes. The necessity for finding new biomaterials and new techniques for dental materials for restoration and orthodontics with high biocompatibility with human bones and tissue are the aim for developing this natural bio-nanocomposites to be instead of using ceramics and metals like titanium. The new developed bio-CPNC dental material have special mechanical, thermal and fracture properties to resist the effects of occlusal loads of mastication with sustainability without expecting bad effects with orofacial esthetics and normal lingual ability because it is green. It can be applied for different types of orthodontics like crowns, bridges and dental implants. The study included processing, design, testing and characterization of different properties. The testing included detailed fundamental experimental work for investigation of the changes of mechanical and fracture properties based on fracture mechanics science. The results and comparison are promising where they are showing large enhancement of the mechanical, fracture and thermal properties of Bio-CPNC in comparison to the polymer material which encourage the researchers, dentists, and dental-companies for extra research to stabilize these natural green Bio-CPNC nanocomposite for dental applications with reducing the cost where all materials components are available locally in comparison to use of conventional ceramics materials or expensive zirconia composites.

Performance and mechanism of electrocatalytic oxidation of urea based on carbon-doped FeCoNiCrMn high entropy alloy film

The application and research of high entropy alloy electrodes in urea oxidation reactions (UOR) are significant. In this study, FeCoNiCrMn, FeCoNiCrMnO, and FeCoNiCrMnC high entropy alloy thin films were prepared by magnetron sputtering by controlling the sputtering power, varying the sputtering atmosphere, and using double target co-sputtering, respectively. The microstructure and surface morphology of the electrode were observed and analyzed by X-ray diffraction, scanning electron microscope, transmission electron microscope, and atomic force microscope. In addition, the chemical state of the elements on the electrode surface was analyzed by X-ray photoelectron spectroscopy (XPS) to clarify the mechanism related to the excellent UOR performance of the electrode. The study found that a small amount of carbon doping can greatly improve the UOR performance of this type of electrode. The amorphous FeCoNiCrMnC electrode has more potential UOR active sites than the face-centered cubic FeCoNiCrMn electrode. After cyclic voltammetry (CV), the potential active sites of the electrode are activated, and the active substances of these electrodes are increased, furthermore, the UOR performance of these electrodes has improved. Since it has 200 cycles of CV, the 10 mA cm−2 potential of FeCoNiCrMnC electrode for UOR is only 1.337 V. After 100 days of natural aging, the catalytic ability of the electrode not only did not decrease but slightly improved, with a potential of 1.321 V at 10 mA cm−2, reflecting the good stability of the catalytic electrode.

Influence of laser texturing on the properties of fusion joints between aluminum alloys and carbon fiber reinforced thermoplastic composites

Laser texturing is an effective method to enhance the fusion joining of aluminum alloy (Al) to carbon fiber reinforced thermoplastics composite (CFRTP). The enhancement effect is related to the morphology and spacing of the microstructures on Al surface. However, because of the correlation between the morphology and the spacing of the microstructures, excessive dense microstructures change the morphology, leading to a reduction in the enhancement effect, while sparse microstructures are also difficult to significantly enhance the joint. To this end, this paper proposes an improved laser texturing process to enhance fusion joints, through the investigation of the recast layer formation process during laser texturing on the Al surface, which comprehensively reveals the synergistic effects of microstructural morphology and spacing on joint properties. The results indicated that the increase of the number of laser processes and the microstructure spacing increased the height of the recast layer, with the difference that the microstructure spacing had less effect after increasing to a certain value. With the increase of microstructure spacing, the morphology of the microstructure on the Al surface transformed from the serrated microstructure to the double-scale microstructure, and finally to the independent microstructure, affected by the recast layer on sides of the microstructure. Once the dual-scale microstructures were formed on the Al surface, the shear strength of the Al/CFRTP fusion joint was the highest with a value of 25.05 MPa. The findings could provide a basis for laser texturing pretreatment for fusion joining.

Evaluation of Solidification and Interfacial Reaction of Sn-Bi and Sn-Bi-In Solder Alloys in Copper and Nickel Interfaces

Although there are studies devoted to lower Indium (In) addition, Sn-Bi alloys containing 10 wt.% In or more have been barely investigated so far. Higher In contents may offer the potential for improved joint production, better control over the growth of interfacial layers, and enhanced mechanical strength. The present article focuses on the solidification, wettability, adhesion strength, and interfacial intermetallic growth in the Sn-40%Bi-10%In alloy soldered on Cu and Ni pads. SEM-EDS, wettability tests, and tensile tests were performed. The contact angles were measured in Cu and Ni as 24° and 26°, respectively. Indium addition promoted coarsening of the as-solidified microstructure due to an increase in the alloy solidification range. The Bi spacing was increased at least three times, with a strong segregation of Bi towards the interface. The formation and growth of alloy/Cu reaction layers were also evaluated under the different aging conditions of the as-soldered joints, simulating real service. A growth kinetics model of the reaction layer showed that In increases the activation energy, thereby reducing the layer growth. The adhesions of the formed intermetallics films in Cu and Ni were analyzed using tensile tests. It was observed that the alloy/Ni couple exhibited better adhesion. Premature fracturing appears to happen in the alloy/Cu joint due to the higher intermetallic compound’s (IMC) thickness, rough morphology, and coarser microstructure. Both ductile fracture features with dimples and cleavage zones associated with Bi, Cu6(Sn,In)5, and Ni3Sn4 intermetallics were observed.

The analysis of microstructure evolution process considering the dynamic solidification conditions and flow field in the oscillating laser welding of aluminum alloy

The oscillating laser welding (OLW) can improve the weld microstructure and the mechanical properties of the welded joints, which greatly improves the quality of laser welding. In this paper, a macro-micro coupling model for investigating the microstructure evolution process in the OLW of 6061 aluminum alloy is developed. The dynamic solidification conditions (SCs) and flow field are considered in the model. The microstructure evolution process under the effect of the oscillating laser beam is analyzed and discussed in detail based on the calculated results. The obtained weld cross section and microstructure morphology results agree well with the experimental results, which proves the validity of the developed model. It is found that the microstructure morphology is significantly influenced by the dynamic temperature gradient (TG) and solidification rate (SR). The solute concentration distribution is changed by the flow field, which affects the microstructure evolution process. The results demonstrate that the developed model is efficient for refining weld microstructure and hence improving mechanical properties of the welded joints.

Laser metal deposition of Al 7075: Effects of TiC nanoparticles

High-density defects in additively manufactured components cause poor mechanical properties and premature failure. The present paper aims in minimizing defects in laser metal deposition (LMD) of high-strength aluminium alloy 7075. The effects of different TiC nanoparticle contents on the defects (crack and porosity), microstructural (grain size and morphology) and mechanical (tensile strength and hardness) properties were investigated systematically. The sizes and densities of cracks and surface porosities were reduced by increasing TiC nanoparticle content. The grain areas were reduced and ultimate tensile strength increased by increasing the TiC nanoparticle content. The present results clearly prove that the TiC content plays a substantial role in tailoring microstructure and improving the reliability and mechanical properties of LMD Al alloy 7075.

Oxygen-rich combustion behaviors and mechanisms of a new Ni-Cr-based superalloy fabricated by selective laser melting

The mechanical and combustion behavior of a new Ni-Cr-based superalloy, fabricated by selective laser melting in an atmosphere with an oxygen concentration greater than 99.5 %, was investigated through the analysis of microstructural morphology, elements distribution and combustion kinetics. The results show that heat treatment eliminated the anisotropy of the as-built microstructures and improved the tensile strength. The studied superalloy can be ignited with a combustion threshold of about 2.5 MPa–3 MPa. The burning length and burning rate increase with the increase of pressure. The selective combustion of Al, Ti, Nb, Cr, Fe, Mo, and Cu elements occurred, resulting in the dissolution of γ′, γ", and δ precipitates and formation of holes at the grain boundaries in the heat-affected zone. The microstructures exhibit large elongated grains in the melting zone and column grains in the heat-affected zone along the heat dissipation direction. The combustion products are a mixture of oxides exhibiting dendritic structures in terms of selective combustion, density, and melting point. The findings from this study enhance our comprehension of the combustion process in nickel-based superalloys, offering valuable data and guidance for the advancement of new oxygen-rich combustion-resistant superalloys.

Development of fishbone powder and carbon-jute fiber reinforced unsaturated polyester based novel green composites: investigation of tensile, impact strength, and morphology microstructure

In the last decade, hybrid composites have been the subject of significant advancements and study. This fast expansion necessitated the development of lightweight composite material with enhanced mechanical strength. In the past few years, the utilization of organic wastes from the food industry, like powder from cow bone, pig bone, and fishbone, has substantially improved the mechanical characteristics of composite materials. Owing to the increasing growth of the meat-based fisheries industry, fish bones are readily available. These bones are often thrown, causing environmental damage. Hence, a sustainable and unique hybrid composite was created employing fish bone powder (FBP) as filler in carbon/jute fibers reinforced polyester matrix. The hybrid composite was compression-molded. FTIR, SEM, and EDS studies were used to characterize the composite. The ASTM standard was used as a reference to explore the mechanical strength (tensile and impact). Additionally explored are the effects of alkali treatment of jute fiber on the above-mentioned processes. It was revealed that the inclusion of FBP and alkali treatment enhanced the mechanical characteristics of the composite. Fishbone powder with a particle size range of 200–250 μm and a weight percentage of 10 to 15% had significant fiber attachment which resulted in improved strength. The produced green composites have proven to be a viable choice for bio-waste treatment in the food sector.

Fabrication of Hierarchical Microstructures via Laser-Induced Shrinkage of Shape Memory Polymers for Flexible Pressure Sensing.

Hierarchical microstructures are widely recognized as one of the most effective components for enhancing the performance of flexible pressure sensors. However, the rapid and controllable fabrication of pressure sensing layers with hierarchical microstructures remains a significant challenge. In this study, we propose a method that utilizes laser-induced microscale shrinkage of shape memory polymers to enable rapid and controllable fabrication of hierarchical microstructures for high-performance pressure sensing. We systematically investigate the influence of UV laser fabrication parameters on the architecture and morphology of hierarchical microstructures. A flexible pressure sensor, equipped with optimized hierarchical microstructures, exhibits a high sensitivity larger than 15 kPa-1 and excellent linearity (R2 = 0.994) in a range from 0 to 200 kPa. It features response and recovery times of 57 and 62 ms, respectively, and maintains good stability, enduring over 5,000 cycles. The laser-induced shrinkage of shape memory polymers offers an effective method for the fabrication of hierarchical microstructures, holding great potential to boost the performance of flexible pressure sensors in applications within intelligent robotics and wearable healthcare.

Novel Fe-Mo intermetallic composite synthesized via diffusional-displacive mixed-mode transformation

Transition metal-based intermetallic materials are candidates for high-temperature structural applications. However, they are limited by their low fracture toughness at ambient temperature. Given Fe is a low-cost metal with a low environmental impact, it is necessary to design tough Fe-based intermetallic alloys. We report a novel ferrite-Fe2Mo intermetallic synthesized through arc melting and quenching of Fe0.78Mo0.22 alloy. Diffusional-displacive mixed-mode transformation of the parent ferrite phase resulted in the formation of nanocomposite microstructure. Two distinct microstructure morphologies of the product μ phase were observed: (i) allotriomorphic phase formation at the parent ferrite grain boundaries and (ii) formation of basket-weave Widmanstätten structures at the parent grain interior. Electron probe microanalysis (EPMA) revealed Mo partitioning across ∼800 nm wide Widmanstätten laths, establishing that it is a diffusional-displacive mixed-mode transformation. We performed atom probe tomography (APT) investigations to ascertain the nanoscale Mo solute partitioning. Based on the chemistry of the retained parent ferrite, the Mo partitioning temperature was estimated to be ∼865 °C. Mo partitioned Widmanstätten lath formation is clarified using a shear-assisted diffusional transformation model. APT studies further revealed that the composition of the product μ phase corresponds to stoichiometric Fe2Mo. It is an anomaly since stoichiometric Fe2Mo typically corresponds to λ C14 Laves phase. We explain the mechanism of μ phase formation with Fe2Mo stoichiometry. The nanocomposite exhibits a high hardness (HV2) of 7.54 GPa and excellent toughness (evidenced by resistance to indentation cracking).

Development of MOF-derived Co3O4 microspheres composed of fiber stacks for simultaneous electrochemical detection of Pb2+ and Cu2+

As an ideal transition metal oxide, Co3O4 is a P-type semiconductor with excellent electrical conductivity, non-toxicity and low cost. This work reports the successful construction of Co3O4 materials derived from metal-organic frameworks (MOFs) using a surfactant micelle template-solvothermal method. The modified electrodes are investigated for their ability to electrochemically detect Pb2+ and Cu2+ in aqueous environments. By adjusting the mass ratios of alkaline modifiers, the morphological microstructures of Co3O4-X exhibit a transition from distinctive microspheres composed of fiber stacks to rods. The results indicate that Co3O4-1(NH4F/CO(NH2)2 = 1:0) has a distinctive microsphere structure composed of stacked fibers, unlike the other two materials. Co3O4-1/GCE is used as the active material of the modified electrode, it shows the largest peak response currents to Pb2+ and Cu2+, and efficiently detects Pb2+ and Cu2+ in the aqueous environment individually and simultaneously. The linear response range of Co3O4-1/GCE for the simultaneous detection of Pb2+ and Cu2+ is 0.5–1.5 μM, with the limits of detection (LOD, S/N = 3) are 9.77 nM and 14.97 nM, respectively. The material exhibits a favorable electrochemical response, via a distinctive Co3O4-1 microsphere structure composed of stacked fibers. This structure enhances the number of active adsorption sites on the material, thereby facilitating the adsorption of heavy metal ions (HMIs). The presence of oxygen vacancies (OV) can also facilitate the adsorption of ions. The Co3O4-1/GCE electrode also exhibits excellent anti-interference ability, stability, and repeatability. This is of great practical significance for detecting Pb2+ and Cu2+ in real water samples and provides a new approach for developing high-performance metal oxide electrochemical sensors derived from MOFs.Graphical abstract

Research on the effect of tuff powder on the properties of moderate-heat portland cement-based materials and the methods for evaluating pozzolanic activity

Tuff powder (TP) has attracted significant attention due to its abundant resources, low carbon emissions, and potential enhancements in concrete property. This study investigates the effect of TP on the mechanical properties, hydration behavior, pore structure, microstructure morphology, economic and environmental analysis of moderate-heat portland cement (MHPC), comparing it with MHPC-based materials containing fly ash (FA). The synergistic morphological effect and micro-aggregate filling action of FA and TP result in higher early strength in the fly ash-tuff powder (FT) group mortar. The CH content and chemically bounded water content of TP paste are higher, showing a better early hydration promotion effect. The pore structure of the composite cement mortar is changed due to the addition of the admixture. Furthermore, the multi-factor response strength and strength activity index (SAI) model were developed based on response surface methodology (RSM), linking to TP specific surface area, dosage, and specimen curing age. This provides a reference for more accurate and comprehensive prediction of cement mortar property, quantification of effects, optimization of mix proportions, and evaluation methods for the activity of pozzolanic materials.

Experimental study on ultrasonic vibration‐assisted drilling performance of carbon fiber polyetherketoneketone laminate

AbstractParts made from carbon fiber reinforced polyetherketoneketone (CF/PEKK) primarily use mechanical connections during assembly, where the quality of hole processing directly impacts the connection strength. However, defects like delamination, burrs, and fiber pull‐out frequently occur during drilling. While existing research focuses on optimizing conventional drilling (CD) and helical milling (HM), ultrasonic vibration‐assisted drilling (UVAD) shows superior performance in reducing thrust force and defects. This study experimentally evaluates the hole‐making performance of CF/PEKK using the UVAD method. It examines the effects of ultrasonic vibration on thrust force, drilling temperature, processing damage, chip morphology, and surface microstructure, and discusses the damage suppression mechanism. The results show that the UVAD method significantly reduces thrust force and drilling temperature compared to the CD method, with similar trends in delamination and burr damage. This study demonstrates that using the UVAD method for drilling CF/PEKK laminates effectively reduces thrust force, drilling temperature, and machining damage, thereby significantly improving processing quality. The material removal mechanism of UVAD was analyzed, offering substantial insights and practical guidance for the efficient drilling of CF/PEKK laminates.Highlights The drilling performance of CF/PEKK was studied. The drilling quality of UVAD and CD is compared by experiments. UVAD has a lower thrust force and drilling temperature. UVAD can reduce machining damage and improve machining quality.

MRI-Derived Modeling of Disease Progression Patterns in Patients With Temporal Lobe Epilepsy.

Temporal lobe epilepsy (TLE) is assumed to follow a steady course that is similar across patients. To date, phenotypic and temporal diversities of TLE evolution remain unknown. In this study, we aimed at simultaneously characterizing these sources of variability based on cross-sectional data. We studied consecutive patients with TLE referred for evaluation by neurologists to the Montreal Neurological Institute epilepsy clinic, who underwent in-patient video EEG monitoring and multimodal imaging at 3 Tesla, comprising 3D T1 and fluid-attenuated inversion recovery and 2D diffusion-weighted MRI. The cohort included patients with drug-resistant epilepsy and patients with drug-responsive epilepsy. The neuropsychological evaluation included Wechsler Adult Intelligence Scale-III and Leonard tapping task. The control group consisted of participants without TLE recruited through advertisement and who underwent the same MRI acquisition as patients. Based on surface-based analysis of key MRI markers of pathology (gray matter morphology and white matter microstructure), the Subtype and Stage Inference algorithm estimated subtypes and stages of brain pathology to which individual patients were assigned. The number of subtypes was determined by running the algorithm 100 times and estimating mean and SD of disease trajectories and the consistency of patients' assignments based on 1,000 bootstrap samples. Effect of normal aging was subtracted from patients. We examined associations with clinical and cognitive parameters and utility for individualized predictions. We studied 82 patients with TLE (52 female, mean age 35 ± 10 years; 11 drug-responsive) and 41 control participants (23 male, mean age 32 ± 8 years). Among 57 operated, 43/37/20 had Engel-I outcome/hippocampal sclerosis/hippocampal isolated gliosis, respectively. We identified 3 trajectory subtypes: S1 (n = 35), led by ipsilateral hippocampal atrophy and gliosis, followed by white-matter damage; S2 (n = 27), characterized by bilateral neocortical atrophy, followed by ipsilateral hippocampal atrophy and gliosis; and S3 (n = 20), typified by bilateral limbic white-matter damage, followed by bilateral hippocampal gliosis. Patients showed high assignability to their subtypes and stages (>90% bootstrap agreement). S1 had the highest proportions of patients with early disease onset (effect size d = 0.27 vs S2, d = 0.73 vs S3), febrile convulsions (χ2 = 3.70), drug resistance (χ2 = 2.94), a positive MRI (χ2 = 8.42), hippocampal sclerosis (χ2 = 7.57), and Engel-I outcome (χ2 = 1.51), pFDR < 0.05 across all comparisons. S2 and S3 exhibited the intermediate and lowest proportions, respectively. Verbal IQ and digit span were lower in S1 (d = 0.65 and d = 0.50, pFDR < 0.05) and S2 (d = 0.76 and d = 1.09, pFDR < 0.05), compared with S3. We observed progressive decline in sequential motor tapping in S1 and S3 (T = -3.38 and T = -4.94, pFDR = 0.027), compared with S2 (T = 2.14, pFDR = 0.035). S3 showed progressive decline in digit span (T = -5.83, p = 0.021). Supervised classifiers trained on subtype and stage outperformed subtype-only and stage-only models predicting drug response in 73% ± 1.0% (vs 70% ± 1.4% and 63% ± 1.3%) and 76% ± 1.6% for Engel-I outcome (vs 71% ± 0.8% and 72% ± 1.1%), pFDR < 0.05 across all comparisons. Cross-sectional MRI-derived models provide reliable prognostic markers of TLE disease evolution, which follows distinct trajectories, each associated with divergent patterns of hippocampal and whole-brain structural alterations, as well as cognitive and clinical profiles.

A Multiscale Computational Modeling Framework to Quantify Microstructural Effects on Nucleation of Li Metal on Carbon Scaffold Architectures

Carbon materials with scaffold architecture have been shown to mitigate the non-uniform Li plating/stripping issues during cycling, which is critical for achieving significantly enhanced energy densities and improved safety of Li metal batteries. However, optimal design of the architecture and microstructure of the carbon materials requires fundamental understanding of the Li metal nucleation behavior at different length scales. In this poster, we present a multiscale computational modeling framework to quantify the microstructural effects of carbon materials on the tendency of Li metal nucleation during plating by integrating atomic-scale simulation, mesoscale microstructure-based homogenization, continuum-scale electrochemistry modeling, and classical nucleation theory. We modeled the architecture of the carbon scaffold and the electrochemistry of Li transport across the electrode and electrolyte by finite element simulation to determine boundary conditions for our mesoscale models. We then generated different porous microstructures of various carbon materials by stochastic and physics-based simulations informed from experiments and performed multiphysics-based simulations at mesoscale to identify the electro-chemo-mechanical hotspots which are sensitive to the microstructure morphology. We calculated the energy barriers for Li to form clusters on graphene surfaces as a function of local Li concentrations and electric fields by ab initio molecular dynamics simulations. The synergistic deployment of different models across scales allows us to theoretically estimate the Li metal nucleation tendency based on a modified classical nucleation theory for different microstructures under various electroplating conditions. Comparison of the theoretical predictions and experimental results will be briefly discussed. The insights obtained from this multiscale framework offer new understanding and strategies for the design of carbon scaffold architectures to mitigate the non-uniformity of Li plating and issues in Li metal anode deployment in solid-state batteries.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and 22-ERD-043.

Microstructure-Aware Mesoscale Modeling of Chemomechanical Stress Evolution during Cycling in Solid Electrolyte-Cathode Composite

The volume change of cathode active materials during charge-discharge cycling is responsible for the capacity fading of all-solid-state Li batteries due to mechanical degradation in the cathode such as delamination and crack formation. Many strategies to alleviate the chemomechanical stress buildup have been proposed in experiments but rationale of the stress release mechanisms at the mesoscale remain elusive. In this presentation, we present a microstructure-aware mesoscale model to quantitatively predict the stress distribution during cycling in a secondary particle agglomerate of the cathode active material embedded within a solid electrolyte matrix, taking the LiCoO2-Li7La3Zr2O12 (LCO-LLZO) as a model system. We find that the mechanical stress hotspots develop at different stages within the grain boundaries of the LCO agglomerate and the LCO-LLZO interfaces. We investigate the influences of microstructural morphology (columnar versus equiaxial), grain orientations (textured versus random), mechanical properties at the grain boundaries and heterogeneous interfaces, and anisotropy of chemical expansion on the stress hotspot evolution and provide optimal mitigation strategies. The theoretical results can help gain mechanistic understanding on cathode degradation and inform guidelines for experimental design of mechanically optimized cathode materials for long-life solid-state batteries.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and 22-ERD-043.