Basal Plane Research Articles

Decoding the Hume-Rothery Rule in a Bifunctional Tetra-metallic Alloy for Alkaline Water Electrolysis.

The 90-year-old Hume-Rothery rule was adapted to design an outstanding bifunctional tetra-metallic alloy electrocatalyst for water electrolysis. Following the radius mismatch principles, Fe (131 pm) and Ni (124 pm) are selectively incorporated at the Pd (139 pm) site of Mo0.30Pd0.70 nanosheets. Analogously, Cu (132 pm) alloys with only Pd, while Ag (145 pm) alloys with both Pd and Mo (154 pm). The face-centered cubic Mo0.30Pd0.35Ni0.23Fe0.12 nanosheets with 10-12 atomic layers, featuring in-plane compressive strain along the {111} basal plane, show 1/3 (422) reflection from local hexagonal symmetry. The more electronegative Pd attracts electron density from Ni/Fe in Mo0.30Pd0.35Ni0.23Fe0.12, synergistically boosting the mass activities for hydrogen and oxygen evolution reactions to 89 ± 5 and 38.6 ± 3.1 A g-1 at ±400 mV versus RHE, respectively. Full water electrolysis continues for ≥550 h, requiring cell voltages of 1.51 and 1.63 V at 10 and 100 mA cm-2, delivering 45 mL h-1 green H2.

Effect of dopants and surface oxides on the electronic properties of dislocations in p-type SiC

Abstract Understanding the electronic properties of dislocations is key to tailoring the properties of silicon carbide (SiC)-based electronic devices. By combining the Kelvin probe force microscopy (KPFM) analysis and first-principles calculations, we investigate the effect of aluminum (Al) dopants and surface oxides on the electronic properties of dislocations in p-type SiC. It is found that dislocations, including threading screw dislocations (TSDs), threading edge dislocations (TEDs), and basal plane dislocations (BPDs) create deep acceptor-like states in p-type SiC. The defect levels move upwards in the order of BPD, TED and TSD, which closely relates with the lattice distortion of dislocations. Interestingly, we find that the defect levels of dislocations are higher than that of Al in p-type SiC. First-principles calculations indicate that the defect formation energies of Al dopants at the cores of dislocations are higher than those in the perfect region of p-type SiC, as a result of the steric effect. This indicates that the concentration of Al acceptors at the dislocation cores is lower than that in the perfect region, resulting in the higher defect level positions of dislocations in p-type SiC. Additionally, we find that surface oxidation reduces the difference of defect-level positions between dislocations and the perfect region of p-type SiC, which paves the way for tailoring the electronic properties of dislocations in p-type SiC.

Unusual variability of isomers in copper(II) complexes with 1,8-bis(2-hydroxybenzyl)-cyclam.

Copper isotopes and their complexes are intensively studied due to their high potential for applications in radiodiagnosis and radiotherapy. Here, we study the CuII complex of 1,8-bis(2-hydroxybenzyl)-cyclam (H2L), which forms an unexpected variety of isomers differing in the mutual orientation of the substituents on the cyclam nitrogen atoms, the protonation of the phenolate pendant, and the ligand denticity. The interconversion of the isomers is rather slow, which made the isolation, identification and investigation of some of the individual species possible. The most stable and the most common form is the hexacoordinated trans-III isomer. However, several other forms were also observed in solution in the course of HPLC, UV-VIS and electrochemical measurements. The isomers present in solution were identified by comparison with the solid-state structures solved by X-ray diffraction analysis on single crystals and with the help of theoretical calculations. The phenolate pendant is coordinated both in the protonated and deprotonated state; however, the coordination in the axial position of the hexacoordinated trans-III complex is weak, especially in its protonated state. Conversely, the CuII ion is pentacoordinated in the cis-V isomer with only one phenolate strongly coordinated in the basal plane of the distorted tetragonal pyramid. The computational data showed that the phenolate groups might form strong intraligand hydrogen bonds competitive with the metal-phenolate bonds, stabilizing the structure of the complex. In addition, theoretical calculations revealed that several geometries are energetically close to the optimal one, which indicates possible dynamic behaviour of the complex in solution.

Infinite Organic Solid-Solution Semiconductors with Continuous Evolution in Film Morphology, Crystalline Lattice and Electrical Properties.

Constructing a solid solution is an effective strategy for regulating the properties of composite organic semiconductors. However, there presents significant challenges in fabrication and understanding of organic solid-solution semiconductors. In this study, infinite solid-solution semiconductors are successfully achieved by integrating rod-like organic molecules, thereby overcoming the limitations of current organic composite semiconductors. Within these solid solutions, one type of molecule are incorporated into the crystalline lattice of another through random substitution. The continuous evolution in film morphology, crystalline lattice parameters and physical properties are observed as component ratios vary, accompanying with changes in the growth behavior of films. Molecular-level intercalation is evidenced by Davydov splitting, photoluminescence spectroscopy, and optical absorption analyses. Moreover, the continuous variation in ionization potential is demonstrated through organic Schottky diodes. This advancement in organic solid solutions can not only satisfy diverse requirements for device fabrication but also facilitate novel designs in device architecture.

Multiscale design optimization of lattice structures considering dynamic response minimization and reaction force uniformity

A multiscale design optimization model is proposed for a vibrating hierarchical lattice structure, considering minimization of vibration response and uniformity of reaction forces at the fixed boundary. Two different lattice unit cells are hybridized to improve the manufacturability and mechanical properties of the lattice structures. Lattice microstructures are designed and controlled by multiple design variables. Surrogate models are used to fit the equivalent performance with the design variables. An optimization formulation is established for minimizing the displacement response amplitude at specified locations of the structure. The variance and mean value of the reaction force are introduced as constraints for the uniform reaction force at the structure boundary. Sensitivities of the objective and constraint functions are derived with the adjoint method. Finally, the effectiveness of the method is verified by several numerical examples, and the influence of the variance constraint of the reaction force at the structure boundary is discussed.

Effect of Feature Size on Defects, Microstructure, and Mechanical Properties of Selective Laser Melted AlSi10Mg Lattice Structure

Selective laser melting lightweight lattice structures have broad application prospects in the aerospace field. Understanding the dependence of mechanical performance on feature size is crucial for structure design. This work optimized the process parameters based on large-size metal blocks (20 mm) and then fabricated submillimeter features with a size of 0.4~1.0 mm. The influence of feature size on the defects, microstructures, and mechanical properties was investigated. The results showed that the dimensional errors for all size features were above 15%. When matched with appropriate border offset, these features could be printed precisely. The densification of submillimeter features was more than 99%, demonstrating the applicability of the optimized process parameters for the fine features. The porosity and relative roughness decreased and tended to stabilize with increasing feature size. Due to having less defects, the thicker features exhibited better mechanical properties in terms of ultimate strength and elongation. After being processed with polishing treatment, the roughness was reduced below 1 μm and the tensile strength increased above 320 MPa. The elastic modulus, yield strength, and elongation were also significantly improved.

Integrated analysis of cellulose structure and properties using solid-state low-field H-NMR and photoacoustic spectroscopy

In this study, we explore the structural intricacies of cellulose, a polymer composed of glucose monomers arranged in a linear chain, primarily investigated through solid-state NMR techniques. Specifically, we employ low-field proton nuclear magnetic resonance (H-NMR) to delve into the diverse hydrogen atom types within the cellulose molecule. The low-field H-NMR technique allows us to discern these hydrogen atoms based on their distinct chemical shifts, providing valuable insights into the various functional groups present in cellulose. Our focus extends to the examination of anomeric protons of glucose units and protons linked to carbon atoms engaged in glycosidic linkages within cellulose chains, which exist in diverse crystalline and amorphous forms. Solid-state low-field H-NMR spectroscopy aids in characterizing the crystallinity degrees and amorphous regions within cellulose, revealing time-dependent changes in free induction decay (FID) signals. Complementing this, we investigate the photo-absorption properties of cellulose fibers under both continuous and modulated irradiation using reversed double-beam photoacoustic spectroscopy (RDB-PAS). This photoacoustic approach allows us to observe ultraviolet- and visible light-induced processes, including electron trap filling and reductive changes on the fiber surface. Our findings suggest that RDB-PAS is a feasible method for estimating the electron trap distribution, serving as a potential measure of the density of crystalline cellulose defects. This integrated approach of combining solid-state low-field H-NMR and RDB-PAS techniques offers a comprehensive understanding of cellulose structure and properties, enhancing our ability to characterize its diverse features.

Effective Design of Three New Layered Gradient Lattice Structures and Their Crashworthiness

Effective Design of Three New Layered Gradient Lattice Structures and Their Crashworthiness

Stiff, lightweight, and programmable architectured pyrolytic carbon lattices via modular assembling

Recent advances in additive manufacturing have enabled the creation of three-dimensional (3D) architectured pyrolytic carbon (PyC) structures with ultrahigh specific strength and energy absorption capabilities. However, their scalability is limited by reduced strength at larger sizes. Here we introduce a modular assembling approach to scale up PyC lattice structures while retaining strength. Three assembling mechanisms—adhesive, Lego-adhesive, and mechanical interlocking—are explored, demonstrating notably increased specific compressive strength and modulus as size increases, driven by energy release from assembly joint fractures. Practical application is demonstrated by using assembled PyC lattices as the core of an aerospace sandwich structure, significantly enhancing indentation resistance compared to conventional aramid paper honeycomb core. The method also enables versatile designs, including curved structures for space debris protection and bio-scaffold applications. This scalable approach offers a promising pathway for integrating PyC structures into large-scale engineering applications requiring superior mechanical properties and programmability in complicated shape design.

Deformation Behavior of Inconel 625 Alloy with TPMS Structure

Triply periodic minimal surfaces (TPMSs) are known for their smooth, fully interconnected, and naturally porous characteristics, offering a superior alternative to traditional porous structures. These structures often suffer from stress concentration and a lack of adjustability. Using laser powder bed fusion (LPBF), we have fabricated Inconel 625 sheet-based TPMS lattice structures with four distinct topologies: Primitive, IWP, Diamond, and Gyroid. The compressive responses and energy absorption capabilities of the four lattice designs were meticulously evaluated. The discrepancies between theoretical predictions and the fabricated specimens were precisely quantified using the Archimedes’ principle for volume displacement. Subsequently, the LPBF-manufactured samples underwent uniaxial compression tests, which were complemented by numerical simulation for validation. The experimental results demonstrate that the IWP lattice consistently outperformed the other three configurations in terms of yield strength. Furthermore, when comparing energy absorption efficiencies, the IWP structures were confirmed to be more effective and closer to the ideal performance. An analysis of the deformation mechanisms shows that the IWP structure characteristically failed in a layer-by-layer manner, distinct from the other structures that exhibited significant shear banding. This distinct behavior was responsible for the higher yield strength (113.16 MPa), elastic modulus (735.76 MPa), and energy absorption capacity (9009.39 MJ/m3) observed in the IWP configuration. To examine the influence of porosity on structural performance, specimens with two varying porosities (70% and 80%) were selected for each of the four designs. Ultimately, the mechanical performance of Inconel 625 under compression was assessed both pre- and post-deformation to elucidate its impact on the material’s integrity.

Two-Dimensional Square Lattice of Colloidal Particles Formed by Electrostatic Adsorption in Confined Space.

In this study, we demonstrate a novel and efficient fabrication methodology for nonclose-packed, two-dimensional (2D) colloidal crystals exhibiting square lattice structures. In our recent work, we detailed the formation of 2D colloidal crystals via the electrostatic adsorption of three-dimensional (3D) charged colloidal crystals onto oppositely charged substrates. These 3D colloidal crystals possessed a face-centered cubic (FCC) lattice structure with their (111) planes aligned parallel to the substrate, facilitating the formation of 2D crystals with triangular lattice arrangements upon adsorption. This work presents the synthesis of 2D crystals with square lattices─a configuration widely used in photonics. We prepared 3D colloidal crystals of silica particles with four-fold symmetry in a micrometer-scale gap between two coverslips. The bottom glass surface is modified with a cationic silane coupling reagent, aminopropyltriethoxysilane, generating pH-responsive charge characteristics with an isoelectric point (iep) near pH 8. When the pH is greater than iep, the surface is charged negatively. As pH decreases below iep, the sign of the surface charge reverses to positive. Controlled pH lowering below the iep induces adsorption of the lowermost lattice plane of 3D crystals onto the substrate, yielding 2D crystals with a distinct square lattice. We further synthesized three-layer body-centered cubic (BCC) structures by stacking alternating layers of the 2D square lattices of silica and polystyrene particles. By aligning the refractive index of the surrounding medium (aqueous solution of ethylene glycol) with that of silica particles, we successfully fabricated a structure that is optically identical to a simple cubic lattice. These findings advance the development of 2D crystalline materials for photonic and plasmonic applications.

Modeling, Design, and Laboratory Testing of a Passive Friction Seismic Metamaterial Base Isolator (PFSMBI)

This paper focuses on the theoretical and analytical modeling of a novel seismic isolator termed the Passive Friction Mechanical Metamaterial Seismic Isolator (PFSMBI) system, which is designed for seismic hazard mitigation in multi-story buildings. The PFSMBI system consists of a lattice structure composed of a series of identical small cells interconnected by layers made of viscoelastic materials. The main function of the lattice is to shift the fundamental natural frequency of the building away from the dominant frequency of earthquake excitations by creating low-frequency bandgaps (FBGs) below 20 Hz. In this configuration, each unit cell contains an inner resonator that slides over a friction surface while it is tuned to vibrate at the fundamental natural frequency of the building. This resonance enhances the energy dissipation capacity of the PFSMBI system. After deriving the governing equations for four selected lattice configurations (i.e., Cases 1–4), a parametric study is performed to optimize the PFSMBI system for a wide range of harmonic ground motion frequencies. In this study, we examine how key parameters, such as the mass ratios of the cells and resonators, tuning frequency ratios, the number of cells, and the coefficient of friction, affect the system’s performance. The PFSMBI system is then incorporated into the dynamic model of a six-story base-isolated building to evaluate its effectiveness in reducing the floor acceleration and inter-story drift under actual earthquake ground motion records. This dynamic model is used to investigate the effect of stick–slip motion (SSM) on the energy dissipation performance of a PFSMBI system by employing the LuGre friction model. The numerical results show that the optimized PFSMBI system, through its lattice structure and frictional resonators, effectively reduces floor acceleration and inter-story drift by leveraging FBGs and frictional energy dissipation, particularly when SSM effects are properly accounted for. Finally, a small-scale prototype of the PFSMBI system with two cells is developed to verify the effect of SSM. This experimental validation highlights that neglecting SSM can lead to an overestimation of the energy dissipation performance of PFSMBI systems.

Toward engineering lattice structures with the material point method (MPM)

Toward engineering lattice structures with the material point method (MPM)

High-strength of additive-manufactured PEEK and Ti6Al4V structure via warm isostatic pressing: applications in medical implants and injection moulds

ABSTRACT Polymer–metal hybrid structures offer synergistic benefits in mechanical property control and lightweight design, making them valuable across various industries. In this study, we designed and developed a warm isostatic pressing (WIP) to fabricate a hybrid structure using additive-manufactured polyetheretherketone (PEEK) and Ti-6Al-4V (Ti64) with an octet-truss lattice structure (OT). The effects of the WIP temperature on the mechanical properties of PEEK were examined by subjecting the parts to different temperatures during the WIP and performing tensile tests. Additionally, to confirm the mechanical properties of Ti64 with OT, we performed a compression test according to the unit cell size (1, 2, 3 mm) at a density of 30% before and after the WIP. Accordingly, we joined a PEEK with superior tensile strength and Ti64 with OT using a WIP under the condition (330°C and 90 bar). Furthermore, we confirmed the superior joint strength of approximately 71.6–74.8% in terms of the tensile and shear strengths of the PEEK-Ti64 hybrid structures compared to the warm isostatic pressed PEEK. Finally, we demonstrated the feasibility of applying PEEK-Ti64 hybrid structures to biomedical implants such as spinal cages and lightweight injection moulds highlighting the potential in advanced manufacturing.

Design for Additive Manufacturing of Lattice Structures for Functional Integration of Thermal Management and Shock Absorption

Design optimization through the integration of multiple functions into a single part is a highly effective strategy to reduce costs, simplify assembly, improve performance, and reduce weight. Additive manufacturing facilitates the production of complex structures by allowing parts consolidation, resulting in optimized designs, where multiple functions are integrated into a single component. This study presents a design for additive manufacturing method for integrating multiple lattice structures to achieve thermal management and shock absorption functions. The method follows modeling and simulation phases for dimensioning and optimizing solutions to deliver the design functions at different macro- and mesoscale levels. Hierarchical complexity was leveraged to design the two-levels structure in a single part, each delivering a specific function. Specifically, the external layer addresses energy absorption and thermal insulation, while the internal layer acts as a thermal battery by incorporating a phase change material. The design of a container carried by an unmanned aerial vehicle for the transport of healthcare and biological materials is presented. The container is shock-resistant and can maintain the content at 4 ± 2 °C for at least 1 h. As it operates passively without the need for additional energy-consuming devices, it is easy to operate and contributes to increased flight autonomy. A flight mission experiment for urgent transport of blood bags confirmed the capability of the container to preserve blood integrity. This case study demonstrates that the two-layer lattice structure design represents a highly efficient approach to multifunctional design optimization.

Comprehensive analysis of the compressive behavior of Fischer-Koch-S, F-RD, and neovius TPMS cellular structures in 3D-printed PLA specimens

This paper investigates the compression-tested mechanical properties of 3D Polylactic acid (PLA) printed Triply Periodic Minimal Surfaces (TPMS) lattice structures, exploring the impact of varying input parameters. The input parameters included in this study are cellular structure, printing speed, and unit cell size. This study serves as a valuable guide for achieving specific mechanical properties through the selection of optimal parameters. The three input parameters would have a major effect in the overall mechanical properties of the specimens. Four output parameters were studied in this experiment elastic modulus, yield stress, plateau stress, and toughness. A Desirability Function Analysis (DFA) was implanted to achieve the most optimal parameter combination and it was compared to the original parameters. By comparing the mechanical properties of the original nine samples against the predicted optimized parameter, the toughness was increased by 2.15%, elastic modulus increased by 108.33%, yield stress increased by 4% and plateau stress increased by 3.97%.

Designing Chiral Organometallic Nanosheets with Room-Temperature Multiferroicity and Topological Nodes.

Two-dimensional (2D) room-temperature chiral multiferroic and magnetic topological materials are essential for constructing functional spintronic devices, yet their number is extremely limited. Here, by using the chiral and polar HPP (HPP = 4-(3-hydroxypyridin-4-yl)pyridin-3-ol) as an organic linker and transition metals (TM = Cr, Mo, W) as nodes, we predict a class of 2D TM(HPP)2 organometallic nanosheets that incorporate homochirality, room-temperature magnetism, ferroelectricity, and topological nodes. The homochirality is introduced by chiral HPP linkers, and the change in structural chirality induces a topological phase transition of Weyl phonons. The room-temperature magnetism arises from the strong d-p spin coupling between TM cations and HPP doublet anions. The ferroelectricity is attributed to the breaking of spatial inversion symmetry in the lattice structure. Additionally, by adjusting the type of TMs, these nanosheets show rich and tunable band structures. Notably, all predicted materials are topologically nontrivial, featuring a quadratic nodal point around the Fermi level.

A preliminary study of linear accelerator-based spatially fractionated radiotherapy

PurposeThis study aimed to provide quantitative information for implementing Lattice radiotherapy (LRT) using a medical linear accelerator equipped with the Millennium 120 multi-leaf collimator (MLC). The research systematically evaluated the impact of varying vertex diameters and separations on dose distribution, peak-to-valley dose ratio (PVDR), and normal tissue dose.MethodsA cylindrical Virtual Water™ phantom was used to create LRT treatments using the Eclipse version 16.0 treatment planning system (Varian, Palo Alto, USA). The plans were optimized employing a 3 × 3 × 3 lattice structure with vertex diameters ranging from 0.5 to 2.0 cm and separations from 1.0 to 5.0 cm. The prescribed dose was 20.0 Gy to 50% of the vertex volume in a single fraction. Peak-to-valley dose ratio (PVDR) was calculated along three orthogonal axes, and normal tissue dose and monitor units (MU) were analyzed. Additionally, the modulation complexity score (MCS) was calculated for each plan to quantitatively assess treatment plan complexity.ResultsThe PVDR analysis demonstrated heterogeneous dose distribution, with optimal values below 30% in all directions for 5.0 cm separation. PVDR in the superior-inferior direction was consistently lower than in other directions. Normal tissue dose analysis revealed increasing mean dose with larger diameters and separations, while the volume receiving high doses decreased. MU analysis showed significant contributions from collimator angles of 315.0° and 45.0°. MCS values ranged from 0.02 to 0.17 for 0.5 cm vertex diameter and 0.08 to 0.20 for larger diameters (1.0-2.0 cm) across different separations, respectively.ConclusionsThis study demonstrates the technical feasibility of implementing LRT using a medical linear accelerator with Millennium 120 MLC. The findings provide insights into optimizing LRT treatment plans, offering a comprehensive quantitative reference for achieving desired dose heterogeneity while maintaining normal tissue protection.

Static and Dynamic Mechanical Behavior of Lattice Structures of Shape Memory Alloys

Static and Dynamic Mechanical Behavior of Lattice Structures of Shape Memory Alloys

A roadmap from the bond strength to the grain-boundary energies and macro strength of metals

Correlating the bond strength with the macro strength of metals is crucial for understanding mechanical properties and designing multi-principal-element alloys (MPEAs). Motivated by the role of grain boundaries in the strength of metals, we introduce a predictive model to determine the grain-boundary energies and strength of metals from the cohesive energy and atomic radius. This scheme originates from the d-band characteristics and broken-bond spirit of tight-binding models, and demonstrates that the repulsive/attractive effects play different roles in the variation of bond strength for different metals. Importantly, our framework not only applies to both pure metals and MPEAs, but also unravels the distinction of the bond strength caused by elemental compositions, lattice structures, high-entropy, and amorphous effects. These findings build a physical picture across bond strength, grain-boundary energies and strength of metals by using easily accessible material properties and provide a robust method for the design of high-strength alloys.