Morphology Evolution Mechanism Research Articles

Mechanistic Insights into the Formation of Dumbbell-Shaped Carbonate Minerals: A microscale study

Dumbbell-shaped carbonate minerals are widely recognized as a distinctive morphology induced by microorganisms. Understanding their morphological evolution and growth mechanisms is essential for elucidating bacterial-mediated carbonate mineralization processes. In this study, we used the mineralizing bacterium Curvibacter sp. strain HJ-1 to induce the formation of dumbbell-shaped carbonate minerals within a rapid crystallization system with a Mg/Ca ratio = 5. A range of microscale analytical techniques, including scanning electron microscopy, focused ion beam, and transmission electron microscopy, were employed to systematically investigate the morphological changes and crystallographic orientation of these minerals. The results reveal that the formation process involves the aggregation of Ca-Mg nanoparticles at both ends of the structure, with bacterial cells acting as a template. These findings offer preliminary insights into the formation mechanisms of dumbbell-shaped minerals and provide a scientific basis for biogenic analysis of field samples.

The Pseudo-Bilayer Bulk Heterojunction Active Layer of Polymer Solar Cells in Green Solvent with 18.48% Efficiency

Planar heterojunction (PHJ) is employed to obtain proper vertical phase separation for highly efficient polymer solar cells (PSCs). However, it heavily relies on the choice of orthogonal solvent in the production process. Here, we fabricated a pseudo-bilayer bulk heterojunction (PBHJ) PSC with cross-distribution in the vertical direction by preparing two layers of PM6 and BTP-eC9 blends in an o-XY solution with different dilution ratios to study the morphological evolution of PBHJ film. We found that the PBHJ film exhibits more uniform and suitable continuous interpenetrating network morphology and proper phase separation in the vertical direction for the formation of p-i-n structure. This provides an effective channel for exciton dissociation and charge transport, which is confirmed by both exciton generation simulations and charge dynamics measurements. The PBHJ devices can effectively inhibit trap recombination and accelerate charge separation and transfer. Based on good active layer morphology and balanced charge mobility, all-green solvent-processed PSCs with champion power conversion efficiencies (PCEs) of 18.48% and 16.83% are obtained in PM6:BTP-eC9 and PTQ10:BTP-eC9 systems, respectively. This work reveals the potential mechanism of morphological evolution induced by the PBHJ structure and provides an alternative approach for developing solution processing PSCs.

Enhanced visible-light photocatalytic performance of hollow Bi/Bi4Ti3O12 microspheres assembled with Bi4Ti3O12 nanosheets and Bi nanodots synthesized by hydrothermal method

Enhanced visible-light photocatalytic performance of hollow Bi/Bi4Ti3O12 microspheres assembled with Bi4Ti3O12 nanosheets and Bi nanodots synthesized by hydrothermal method

Research on Ni-WC Coating and a Carbide Solidification Simulation Mechanism of PTAW on the Descaling Roll Surface

The descaling roll is a critical component in a hot-rolling production line. The operating conditions are significantly impacted by water with high-pressure and dynamic shocks caused by high-temperature steel slab descaling. Roll surfaces often experience wear and corrosion failures. This is attributed to a combination of high temperatures, intense wear, and repeated thermal, mechanical, and fluid stresses. Production costs and efficiency are significantly affected by the replacement of descaling rolls. Practice shows that the use of plasma cladding technology forms high-performance coatings. Conventional metal surface properties can be significantly improved. In this study, a Ni-WC composite coating was prepared on the descaling roll surface by plasma-transferred arc welding (PTAW) technology. The microstructure and phase composition of the welding overlay were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results show that the WC hard phase added to the molten pool dissolves, and subsequently M7C3 and W2C phases are formed. To further explore the morphological evolution mechanism of the hard phase, numerical simulations were performed using a phase-field method to model M7C3 phase precipitation. The evolution from nucleation, rod-like growth, to eutectic structure formation was revealed. Experimental and simulation results show high consistency, validating the established phase-field model. In this study, a theoretical foundation for designing and preparing high-performance coatings is provided.

Temperature effects on low cycle fatigue deformation of powder metallurgy superalloy FGH95

Temperature effects on low cycle fatigue deformation of powder metallurgy superalloy FGH95

Modification mechanism of Te and morphology evolution of primary Mg2Si in an Al-20Mg2Si alloy

In the present work, the modification effect of Te and the corresponding growth process of Mg2Si were clarified. With 0.5wt% Te addition, the dendritic primary Mg2Si transformed to polygons, accompanied by a reduction in size from over ∼165μm-∼18μm. However, 2.0wt% Te addition resulted in degradation of modification effect, and the morphology of Mg2Si changed to dendrite. Three-dimensional morphology of primary Mg2Si indicated that Te altered the morphology of primary Mg2Si from dendrites to polyhedrons surrounded by {111} and {100}. The modification mechanism of Te can be attributed to the heterogeneous nucleation and the doping of Te during the growth process of primary Mg2Si, which greatly contributed to dimension decrease and morphology evolution of primary Mg2Si respectively. With Te corporation, the relative surface energy between the {100} and {111} (r) drops, contributing to the exposure of {100}. Our work shows that the solute concentration under non-equilibrium solidification plays an important role in determining the final morphology of Mg2Si. The local segregation of Mg and Si solutes results in the degradation of dendrite arms along certain directions during the initial stage of crystal growth. Combined with the modifying effect of Te, which alters the surface energy of the crystal, the final crystal morphology deviates from its equilibrium state. Our study demonstrates that ultimate morphology and dimensions of primary Mg2Si can be determined simultaneously with the addition of certain modifiers, which can be achieved by regulating the growth and nucleation of Mg2Si at the same time.

Morphological evolution mechanism of microstructures involved in shaping micro-pillar arrays into microlens arrays on fused silica surfaces by CO2 laser polishing

Morphological evolution mechanism of microstructures involved in shaping micro-pillar arrays into microlens arrays on fused silica surfaces by CO2 laser polishing

Study on the thermal runaway behavior and mechanism of 18650 lithium-ion battery induced by external short circuit

Study on the thermal runaway behavior and mechanism of 18650 lithium-ion battery induced by external short circuit

Glucose-assisted solvothermal synthesis of hierarchical micro-nano yolk–shell V2O3 microspheres as an anode material for lithium-ion batteries

Glucose-assisted solvothermal synthesis of hierarchical micro-nano yolk–shell V2O3 microspheres as an anode material for lithium-ion batteries

Interfacial engineering and vacancy design of quasi-2D NiCoAl-LDH/Kaolin hybrid for activating peroxymonosulfate to boost degradation of antibiotics

Interfacial engineering and vacancy design of quasi-2D NiCoAl-LDH/Kaolin hybrid for activating peroxymonosulfate to boost degradation of antibiotics

Phase field simulation of dendrites morphology evolution in sodium metal batteries

Phase field simulation of dendrites morphology evolution in sodium metal batteries

PH-dependent growth of alumina nanorods with a high aspect ratio for enhanced propane dehydrogenation performance

pH-dependent growth of alumina nanorods with a high aspect ratio for enhanced propane dehydrogenation performance

Formation Mechanism and Morphology Evolution of β-NaYF4 Single Microcrystals in Hydrothermal Process

Lanthanide-doped upconversion (Ln-doped UC) materials with predicable phase and geometry are attractive for their promising application in optics and biological. Herein, we report a facile strategy for deterministic synthesis of β-NaYF4 microcrystals by an ethylenediaminetetraacetic acid (EDTA) assisted hydrothermal process. The nucleation and growth process of the β-NaYF4 microcrystals have been experimentally revealed with different hydrothermal times. The phase and geometry of as-obtained crystals can be well manipulated by the experimental parameters such as pH values, precursors’ ratio, and reactant concentrations. The formation and morphology evolution mechanism of β-NaYF4 single microcrystals can be qualitatively analyzed using energy minimization principles under the thermodynamic and kinetic control. In addition, we presented the colour-changing up-conversion of Tm3+ and Yb3+ doped single β-NaYF4 microrod. Our work could help the understanding on crystal growth and design of rare earth fluoride mateirals at micro and nanoscale.

Crystal plane orientation-dependent surface atom diffusion in sub-10-nm Au nanocrystals.

Surface atom diffusion is a ubiquitous phenomenon in nanostructured metals with ultrahigh surface-to-volume ratios. However, the fundamental atomic mechanism of surface atom diffusion remains elusive. Here, we report in situ atomic-scale observations of surface pressure-driven atom diffusion in gold nanocrystals at room temperature using high-resolution transmission electron microscopy with a high-speed detection camera. The topmost layer of atoms on (001) plane initially diffuse in a column-by-column manner. As diffusion proceeds, the remaining atomic columns collectively inject into adjacent underlayer, accompanied by nucleation of a surface dislocation. In comparison, atoms on (111) plane directly diffuse to the base without collective injection. Quantitative calculations indicate that these crystal plane orientation-dependent atom diffusion behaviors contribute to the larger diffusion coefficient of (111) plane compared to (001) plane in addition to the effect of diffusion activation energy. Our findings provide valuable insights into atomic mechanisms of diffusion-dominant morphology evolution of nanostructured metals and guide the design of nanostructured materials with enhanced structural stability.

Taking a Tailored Approach to Material Design: A Mechanistic Study of the Selective Localization of Phase-Separated Graphene Microdomains.

To achieve multifunctional properties using nanocomposites, selectively locating nanofillers in specific areas by tailoring a mixture of two immiscible polymers has been widely investigated. Forming a phase-separated structure from entirely miscible molecules is rarely reported, and the related mechanisms to govern the formation of assemblies from molecules have not been fully resolved. In this work, a novel method and the underlying mechanism to fabricate self-assembling, bicontinuous, biphasic structures with localized domains made up of amine-functionalized graphene nanoplatelets are presented, involving the tailoring of compositions in a liquid processable multicomponent epoxy blend. Kinetics studies were carried out to investigate the differences in reactivity of various epoxy-hardener pairs. Molecular dynamics simulations and in situ optical photothermal infrared spectroscopy measurements revealed the trajectories of different components during the early stages of polymerization, supporting the migration (phase behavior) of each component during the curing process. Confirmed by the phase structure and the correlated chemical maps down to the submicrometer level, it is believed that the bicontinuous phase separation is driven by the change of the miscibility between various building blocks forming during polymerization, leading to the formation of nanofiller domains. The proposed morphology evolution mechanism is based on combining solubility parameter calculations with kinetics studies, and preliminary experiments are performed to validate the applicability of the mechanism of selectively locating nanofillers in the phase-separated structure. This provides a simple yet sophisticated engineering model and a roadmap to a mechanism for fabricating phase-separated structures with nanofiller domains in nanocomposite films.

Morphology evolution and non-uniformity removal mechanism analysis of diamond nanocone arrays by reactive ion etching

Morphology evolution and non-uniformity removal mechanism analysis of diamond nanocone arrays by reactive ion etching

Overbank Flow, Sediment Transport, and Channel Morphology in the Lower Yellow River: A Review

As a prerequisite and foundation for studying the evolution mechanism of river channels, an in-depth understanding of the cross-sectional morphology adjustment is required. As a starting point, it is crucial to systematically summarize and generalize the research findings on channel morphological adjustment obtained to date, particularly in the context of the significant changes in the water and sediment conditions of large rivers that have occurred worldwide. This paper provides a comprehensive review of the research findings on the three following aspects of the Lower Yellow River: the transverse distribution of overbank flow velocity, the transverse distribution of suspended sediment concentration, and the morphological adjustment of the river cross-section. There are various equations available to predict the lateral depth–average flow velocity distribution. These equations are classified into the two following categories: empirical and theoretical formulas. Theoretical formulas are obtained through consideration of the cross-sectional morphology, accounting for inertial force terms caused by secondary flow, and momentum transfer between the main channel and its floodplain. Similarly, empirical equations and theoretical formulas for sediment concentration transverse distribution are also summarized, given the different influencing factors and assumptions. We also discuss the morphological adjustment of river cross-sections based on the analysis of measured data, mathematical model calculation, and the physical model test. In particular, we propose the idea of revealing channel cross-section morphology evolution mechanisms from the theoretical level of water and sediment movement and distribution. This review aims to enhance understanding of overbank flow, sediment transport, and channel morphology in the Lower Yellow River and may also serve to some extent as a reference for the evolution and management of channels in other rivers.

Evolution mechanism of subsurface damage during laser machining process of fused silica

The machining-induced subsurface damage (SSD) on fused silica optics would incur damage when irradiated by intense lasers, which severely restricts the service life of fused silica optics. The high absorption of fused silica to 10.6 µm makes it possible to utilize pulsed CO2 laser to remove and characterize SSD by layer-by-layer ablation, which improves its laser-induced damage threshold. However, thermal stress during the laser ablation process may have an impact on SSD, leading to extension. Still, the law of SSD morphology evolution mechanism has not been clearly revealed. In this work, a multi-physics simulated model considering light field modulation is established to reveal the evolution law of radial SSD during the laser layer-by-layer ablation process. Based on the simulation of different characteristic structural parameters, two evolution mechanisms of radial SSD are revealed, and the influence of characteristic structural parameters on SSD is also elaborated. By prefabricating the SSD by femtosecond laser, the measurements of SSD during CO2 laser layer-by-layer ablation experiments are consistent with the simulated results, and three stages of SSD depth variation under two evolution processes are further proposed. The findings of this study provide theoretical guidance for effectively characterizing SSD based on laser layer-by-layer ablation strategies on fused silica optics.

Dissolution behavior and kinetics of the γ′ precipitates within a novel powder metallurgy Ni-based superalloy

Dissolution behavior and kinetics of the γ′ precipitates within a novel powder metallurgy Ni-based superalloy

Impact of Electrostatic Interaction on Vertical Morphology and Energy Loss in Efficient Pseudo-Planar Heterojunction Organic Solar Cells.

Although a suitable vertical phase separation (VPS) morphology is essential for improving charge transport efficiency, reducing charge recombination, and ultimately boosting the efficiency of organic solar cells (OSCs), there is a lack of theoretical guidance on how to achieve the ideal morphology. Herein, a relationship between the molecular structure and the VPS morphology of pseudo-planar heterojunction (PPHJ) OSCs is established by using molecular surface electrostatic potential (ESP) as a bridge. The morphological evolution mechanism is revealed by studying four binary systems with vary electrostatic potential difference (∆ESP) between donors (Ds) and acceptors (As). The findings manifest that as ∆ESP increases, the active layer is more likely to form a well-mixed phase, while a smaller ∆ESP favors VPS morphology. Interestingly, it is also observed that a larger ∆ESP leads to enhanced miscibility between Ds and As, resulting in higher non-radiative energy losses (ΔE3). Based on these discoveries, a ternary PPHJ device is meticulously designed with an appropriate ∆ESP to obtain better VPS morphology and lower ΔE3, and an impressive efficiency of 19.09% is achieved. This work demonstrates that by optimizing the ΔESP, not only the formation of VPS morphology can be controlled, but also energy losses can be reduced, paving the way to further boost OSC performance.