Sheet Structure Research Articles

The effects of sheet and network solid structures of similar TPMS scaffold architectures on permeability, wall shear stress, and velocity: A CFD analysis.

Triply periodic minimal surface (TPMS) is known mathematically as a surface with mean curvature of zero and replicated in three directions infinitely. Providing the pore combination in porous structures with surface connections, they provide large surface areas. This study aims to determine the effects of the network solid and sheet solid structures in the three different TPMS architectures on bone regeneration. Evaluation is made for Diamond, Gyroid, and I-WP structures, which are widely preferred architectures in terms of mechanical strength. Scaffolds are modeled as both network solid and sheet solid unit cells with similar porosities (60%, 70%, and 80%). Flow analyses are performed with the Computational Fluid Dynamics method to determine of potential for bone cell development of scaffolds. The permeability, wall shear stress on the surfaces, and the flow velocity distribution of the scaffolds are obtained with these analyses. The permeability value of 18 scaffolds is between the permeability values determined for trabecular bone. The permeability of network solid TPMS scaffolds for the same architectures is higher than sheet solid TPMS scaffolds due to the low pressures generated. The maximum wall shear stress in scaffolds decreases as porosity increases. Since the maximum wall shear stresses occur in less than 0.1% area on the scaffold surfaces, it is more appropriate to examine distribution of these stresses on the scaffold surfaces. Sheet solid structures within TPMS are more advantageous for biomechanical environments due to their greater surface area at similar porosities, wall shear stress, and permeability values.

Study on the properties of the MgCO3@2Mn1−xMxCO3 carbonate composite material as a cathode electrode in the aqueous zinc-ion battery and the effect of Ag ion doping at the manganese site

With the international background of advocating green environmental protection and sustainable development, the aqueous zinc ion battery has attracted researchers’ attention because of its many advantages. The application of a manganese-based material as a positive electrode in the aqueous zinc ion battery has broad development prospect. In this paper, the composite materials of manganese carbonate and magnesium carbonate were synthesized by the hydrothermal method. Metal ions were doped at the manganese site of the composite materials to synthesize MgCO3@2Mn1−xMxCO3 materials. By comparing the electrochemical performance test results, it can be seen that the MgCO3@2Mn0.995Ag0.005CO3 material showed better magnification performance and its capacity can reach 282.6 mAh/g at 50 mA/g current density. Moreover, its electrochemical performance is also better than that of other doped materials. Through the scanning electron microscopy image analysis of the material, it can be seen that the material is mainly in a cubic structure of different sizes and the small cube structures are crosslinked together to form a sheet structure, which can further increase the closeness of the particle connection. By energy dispersive spectroscopy and x-ray photoelectron spectroscopy analysis, it can be found that the corresponding valence states of Mn, C, O, and Mg elements in the material are consistent with those in the MgCO3@2Mn0.995Ag0.005CO3 material. In the XRD test, the crystallinity of the material is good, and no obvious impurity peak is found.

Insight into the Structural Ambiguity of Actinide(IV) Oxalate Sheet Structures: A Case for Alternate Coordination Geometries.

Invited for the cover of this issue is the group of Amy Hixon at the University of Notre Dame. The image depicts the newly identified structure of a PuIV oxalate sheet compared to the historically assumed structure. Read the full text of the article at 10.1002/chem.202301164.

Enhanced Flexural Performance of Diamond Latticed Triply Periodic Minimal Surface Sandwich Panels

The additively manufactured bio‐inspired lattice structures have various superior properties in comparison to their solid counterparts as they are lightweight and suitable for fabricating various parts in aerospace sectors. This study limits the investigation of triply periodic minimal surface (TPMS)‐based diamond sheet and solid cellular structures with varying densities (25%, 35%, 45%, and graded) under flexural loading conditions. The sandwich panel structures are made using acrylonitrile butadiene styrene material utilizing the fused filament fabrication (FFF) process. In‐plane flexural performances of the FFF fabricated bio‐inspired TPMS diamond sandwich panels are investigated for the first time. The panels are created to investigate how density and unit cell geometry affect stiffness, strength, and energy absorption. The digital image correlation approach is used to visualize the deflection of the panels subjected to three‐point bending. Also, a theoretical analysis is done to find out the deflection of the sandwich panel structures. An Ashby chart shows the comparison of the specific energy absorption of the TPMS diamond sandwich panels used in this study with several other cellular core sandwich panels available in the literature. This study provides a valuable contribution to the improved energy absorption performance of additively manufactured cellular materials.

Front Cover: Insight into the Structural Ambiguity of Actinide(IV) Oxalate Sheet Structures: A Case for Alternate Coordination Geometries (Chem. Eur. J. 47/2023)

Front Cover: Insight into the Structural Ambiguity of Actinide(IV) Oxalate Sheet Structures: A Case for Alternate Coordination Geometries (Chem. Eur. J. 47/2023)

Additive Manufacturing of Cu Using Graphene-Oxide-Treated Powder.

Additive manufacturing of Cu is interesting for many applications where high thermal and electric conductivity are required. A problem with printing of Cu with a laser-based process is the high reflectance of the powder for near-infrared wavelengths making it difficult to print components with a high density. In this study, we have investigated laser bed fusion (L-PBF) of Cu using graphene oxide (GO)-coated powder. The powder particles were coated in a simple wet-chemical process using electrostatic attractions between the GO and the powder surface. The coated powder exhibited a reduced reflectivity, which improved the printability and increased the densities from ~90% for uncoated powder to 99.8% using 0.1 wt% GO and a laser power of 500 W. The coated Cu powders showed a tendency for balling using laser powers below 400 W, and increasing the GO concentration from 0.1 to 0.3 wt.% showed an increase in spattering and reduced density. Graphene-like sheet structures could be observed in the printed parts using scanning electron microscopy (SEM). Carbon-filled inclusions with sizes ranging from 10-200 nm could also be observed in the printed parts using transmission electron microscopy (TEM). The GO treatment yielded parts with higher hardness (75.7 HV) and electrical conductivity (77.8% IACS) compared to the parts printed with reference Cu powder.

Controlling Photoinduced H2 Release from Freestanding Borophane Sheets Under UV Irradiation by Tuning B–H Bonds

AbstractHydrogen boride (HB), a freestanding 2D hydrogenated‐borophene (borophane) polymorph, is synthesized via ion exchange. HB sheets with a B/H atomic ratio of 1.0 are confirmed to contain three‐center–two‐electron B–H–B bonds and two‐center–two‐electron terminal B–H bonds. The optical properties of HB sheets are expected to be tunable by changing the BHB/BH bond ratio, which alters the electronic structure of HB sheets; however, this is not yet achieved. This study demonstrates that controlling the BHB/BH bond ratio in the HB sheets is possible without altering the hydrogen content by adjusting the volume of ion‐exchange resin during synthesis, thus enabling the tuning of the photoinduced H2 release under UV irradiation. Furthermore, the fluorescence intensity correlates with the absorbance ratio of the BHB and BH vibrational modes. Increasing the BHB/BH bond ratio enhances the luminescence intensity, whereas reducing it enhances the photoinduced H2 release rate under UV irradiation. The ability to control the BHB/BH bond ratio of HB sheets provides new avenues for optimizing their properties for various applications, including hydrogen storage and photocatalysis.

Hydrogen catalytic performance of hybrid Fe3O4/FeS2/g-C3N4 nanocomposite structures

In this work, Fe3O4/FeS2/g-C3N4 nanocomposites were developed for catalytic hydrogen generation from sodium borohydride. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and environmental scanning electron microscopy (ESEM) were used to analyze these nanocomposites. The XRD diffraction peaks of Fe3O4 and FeS2 cubic phase showed an average crystal size of calculation of 15 and 20 nm. ESEM micrographs showed a 2D broken up sheet structure having more edge sites. The BET surface areas for S@g-C3N4, 1.0, 2.0, and 3.0 wt% Fe3O4/FeS2 were 40, 109, 137 and 162 m2/g, respectively. Even though Fe3O4/FeS2 were incorporated into the nanosheet, the pore size was increased from 2.0 to 2.15 nm. S@g-C3N4 has an average band gap of 2.60 eV that decreased to 2.30, 2.21 and 2.18 eV at 1.0, 2.0 and 3.0 wt% of FeS2. In addition, Fe3O4/FeS2/g-C3N4 nanosheets showed an emission band at 460 nm. Moreover, the intensity of this band decreased as the content of Fe3O4/FeS2 reached 3.0 wt%. The rate of hydrogen production is accelerated as the percentage of Fe3O4/FeS2 increased from 1.0 to 3.0 wt%. The sample 3.0 wt% Fe3O4/FeS2 showed the best rate of hydrogen production (8480 mL/g·min).

Development of a Numerical Ice Tank Based on DEM and Physical Model Testing: Methods, Validations and Applications

The determination of ice loads on polar vessels and offshore structures is important for ice-resistant design, safe operation, and management of structural integrity in ice-infested waters. Physical model testing carried out in an ice tank/basin is usually an important technical approach for evaluating the ice loads. However, the high cost and time consumption make it difficult to perform multiple repetitions or numerous trials. Recently, the rapid development of high-performance computation techniques provides a usable alternative where the numerical methods represented by the discrete element method (DEM) have made remarkable contributions to the ice load predictions. Based on DEM simulations validated by physical model tests, numerical ice tanks can be developed as an effective complement to their counterparts. In this paper, a numerical ice tank based on 3D spherical DEM was established with respect to the small ice model basin of China Ship Scientific Research Center (CSSRC-SIMB). Based on spherical DEM with parallel bond model, the model tests of typical structures (vertical cylinder and inclined plate) in level ice sheets were established in the numerical ice tank, and the ice–structure interaction process under the same initial conditions was simulated. The accuracy of the simulations is verified by comparing the simulated ice loads with the measured ice loads from the model tests in the CSSRC-SIMB. Furthermore, the application of the numerical ice tank was extended to simulate the navigation of a Wass bow in level ice and broken ice conditions. The value of the break resistance of the Wass bow in level ice was evaluated, and the numerical ice tank produced results that were found to be consistent with those obtained from Lindqvist’s formula. The statistical properties of the bow load for different broken ice fields with the same initial physical conditions are analyzed by performing a repeatability test on the broken ice fields.

Review of the development of graphene and application in photocatalyst

Graphene was originally found as a thin sheet structure. Researchers have expanded their studies to include this 2D carbon structure in recent years. The paper aims to give a review of the development of graphene and its application in photocatalysts based on existing research literature and data. The result shows that, currently, graphene-based nanomaterials for medical applications are a popular research topic. In this paper, the structure, characteristics, synthesis and surface modification of graphene is classified into covalent and non-covalent approaches.

Carbon Quantum Dots-Doped Ni3Se4/Co9Se8/Fe3O4 Multilayer Nanosheets Prepared Using the One-Step Solvothermal Method to Boost Electrocatalytic Oxygen Evolution.

Oxygen evolution reaction is a momentous part of electrochemical energy storage and conversion devices such as rechargeable metal-air batteries. It is particularly urgent to develop low-cost and efficient electrocatalysts for oxygen evolution reactions. As a potential substitute for noble metal electrocatalysts, transition metal selenides still prove challenging in improving the activity of oxygen evolution reaction and research into reaction intermediates. In this study, a simple one-step solvothermal method was used to prepare a polymetallic compound carbon matrix composite (Co9Se8/Ni3Se4/Fe3O4@C) with a multilayered nanosheets structure. It exhibited good OER activity in an alkaline electrolyte solution, with an overpotential of 268 mV at 10 mA/cm2. In addition, this catalyst also showed excellent performance in the 24 h stability test. The composite presents a multi-layer sheet structure, which effectively improves the contact between the active site and the electrolyte. The selenide formed by Ni and Co has a synergistic effect, and Fe3O4 and Co9Se8 form a heterojunction structure which can effectively improve the reaction activity by initiating the electronic coupling effect through the interface modification. In addition, carbon quantum dots have rich heteroatoms and electron transferability, which improves the electrochemical properties of the composites. This work provides a new strategy for the preparation of highly efficient OER electrocatalysts utilizing the multi-metal synergistic effect.

Application of a Response Surface Method for the Optimization of the Hydrothermal Synthesis of Magnetic NiCo2O4 Desulfurization Catalytic Powders

In this study, nickel cobaltate (NiCo2O4) powders are employed as a catalyst in conjunction with persulfate for the development of a catalytic oxidation system to enhance fuel desulfurization. The hydrothermal synthesis conditions of NiCo2O4 powders, which significantly influenced the desulfurization efficiency, were optimized using a response surface methodology with a Box–Behnken design. These conditions were ranked in the following order: calcination temperature > hydrothermal temperature > calcination time > hydrothermal time. Through the optimization process, the ideal preparation conditions were determined as follows: a hydrothermal temperature of 143 °C, hydrothermal time of 6.1 h, calcination temperature of 330 °C, and calcination time of 3.7 h. Under these optimized conditions, the predicted desulfurization rate was approximately 85.8%. The experimental results closely matched the prediction, yielding a desulfurization rate of around 84%, with a minimal error of only 2.1%. To characterize the NiCo2O4 powders prepared under the optimal conditions, XRD, SEM, and TEM analyses were conducted. The analysis revealed that the microscopic morphology of NiCo2O4 exhibited a rectangular sheet structure, with an average particle size of 20 nm. Additionally, fan-shaped NiCo2O4 particles were observed as a result of linear and bundle agglomerations. Thus, this work is innovative in its ability to synthesize nano-catalysts using hydrothermal synthesis in a controllable manner and establishing a correlation between the hydrothermal synthesis conditions and catalytic activity.

Wearable Strain Sensor With a Graphene Localized Warping Structure for Ultra-Wide Range Strain Detection and Bending Direction Recognition

The practical need for the accurate detection of human activities requires wearable flexible strain sensors that can detect subtle and large strains and recognize the bending direction of joints. However, it remains challenging to integrate these detection capabilities into a single strain sensor. Herein, we prepared flexible strain sensors with firmly attached locally warped graphene on the surface of anhydride-grafted styrene-butadiene-styrene triblock copolymer films using a swelling-self-assembly method. The unique localized warpage structure of graphene sheets gives the sensor excellent strain response performance and the ability to recognize the bending direction. The detection limit of the sensor to strain is independent of the sensitivity to strain, which allows it to detect ultralow (0.01%) and large strains (500%). Moreover, the sensor has a large linear response range (0~94%) and good test stability (3000 cycles of strain). The sensor can be used to recognize the bending direction by generating opposite response signals to different bending directions. The excellent response behavior allows the sensor to accurately monitor the joint bending angle, direction of the human body, and subtle tremors of the human skin, which makes it a potential application for wearable devices and smart prosthetics.

Reasonable thickness determination for implicit porous sheet structure using persistent homology

Porous structures are widely used in various industries because of their excellent properties. Porous surfaces have no thickness and should be thickened to sheet structures for further fabrication. For porous surfaces with implicit representation, sheet structures can be generated by extracting the region between two iso-surfaces. However, too small sheet thickness leads to extra small holes emerging on the sheet structure, and too large sheet thickness makes the pores closed. In this study, we propose a novel method for determining the sheet thickness for porous surfaces represented by implicit functions. Specifically, after calculating the persistent diagram (PD) of the scalar field dictated by the implicit function, the points in the PD are clustering into three clusters. Using these clusters, a topology control method is developed, which allows users to determine how many pores can be closed. Moreover, a reasonable thickness can be determined, by which all of the pores keep open, and the extra small holes are eliminated. Experimental results show the effectiveness of the developed method.

High-performance and scalable wood-based solar-driven interfacial evaporator with corrugated structure for continuous desalination

Interfacial solar-driven evaporation of saline water is a promising technique that enables worldwide upscaling of freshwater with a minimum of carbon footprint. For this purpose, wood is demonstrating a desirable substrate due to its high porosity and low thermal conductivity. Despite much effort has been dedicated to improving the performance of wood evaporators, their scalability and reliability still restrict applications. Here we present a large-scale and highly-efficient wood-based evaporator with corrugated sheet structures using a facile mechanical processing strategy that utilizes the excellent processability of wood. The corrugated structure of the longitudinal wood block, transports water in the longitudinal direction and thereby increases the evaporation area. With the inclusion of a Chinese ink layer and hydrophobic treatment, the prepared wood-based evaporators exhibit a high evaporation rate (1.77 kg m−2 h−1 for spruce wood, 1.42 kg m−2 h−1 for beech wood) and efficiency (111.53% for spruce wood, 88.73% for beech wood) at 1 sun irradiation and continuous water desalination, which is superior to both reported longitudinal and most transverse wood-based evaporators. This work demonstrates a universal and economy strategy for preparing large-sized wood-based solar evaporators with processability, stable performance and high efficiency.

Influence of Fe–N–C morphologies on the oxygen reduction reaction in acidic and alkaline media

AbstractThe development of nonnoble metal oxygen reduction reaction (ORR) catalysts for fuel cells has been motivated by the high cost and limited supply of noble metals, as well as the desire to improve the performance and durability of this type of energy conversion device. In this study, nonnoble Fe–N–C catalyst was synthesized using a zeolitic imidazole framework (ZIF‐8), poly (aniline), and 10,10′‐dibromo‐9,9′‐bianthry as precursors to produce Fe–N–C with hollow sphere (HS), amorphous bulky structure (B), and sheet‐like thin sheet (N) structure. The Fe–N–C catalyst was analysed in terms of their shape, crystal structure, pore characteristics, and elemental composition. Among all the Fe–N–C catalysts, Fe–N–C_HS had the highest total surface area, followed by Fe–N–C_B and Fe–N–C_N. To evaluate their ORR catalytic activity, a half‐cell electrochemical experiment with .1 M KOH and .1 M HClO4 as the alkaline and acidic electrolytes was conducted. This study revealed that Fe–N–C_HS exhibited the highest onset potential but the Fe–N–C_B has the highest limiting current density in alkaline medium; meanwhile, in acidic media, Fe–N–C_HS shows the best ORR performance with the highest onset potential and limiting current. This highly porous Fe–N–C_HS catalyst also demonstrated active site activation and excellent stability compared with the other samples as well as commercial Pt/C in acidic electrolyte, which suggests its potential for application in proton exchange membrane fuel cells (PEMFCs).

Interaction of pristine and novel graphene allotropes with copper nanoparticles: Coupled density functional and molecular dynamics study

We combined the density functional theory and classical molecular dynamics to study the time evolution and thermal stability of copper nanoparticles wrapped in graphene flakes. We observed a strong attraction between nanoparticles and flakes, which was underestimated in many previous simulations. We found that the two-parameter Lennard-Jones potential with parameters ε = 0.074 eV and r0 = 3.310 Å reproduces DFT data better than other empirical potentials. We confirmed that a nanoparticle could be held reliable inside a graphene flake. The graphene-coated copper system remains stable over the temperature range of 300–1000 K. In addition to pristine graphene, we considered several strained allotropes containing pentagons, as well as heptagons, octagons, and nanometer-sized pores. Strained allotropes interact with copper nanoparticles approximately twice more strongly as compared to pristine graphene. Molecular dynamics revealed nanoparticle flattening due to strong interaction with graphene allotropes at elevated temperatures. The wettability of graphene with respect to copper strongly depends on the sheet structure and can vary significantly for different allotropes. The results may be useful for further research on copper-graphene composites, which are suitable for catalytic and biomedical applications.

Insight into the structural ambiguity of actinide(IV) oxalate sheet structures: a case for alternate coordination geometries.

Plutonium(IV) oxalate hexahydrate (Pu(C2O4)2∙6H2O; PuOx) is an important intermediate in the recovery of plutonium from used nuclear fuel. Its formation via precipitation is well studied, yet its crystal structure remains unknown. Instead, the crystal structure of PuOx is assumed to be isostructural with neptunium(IV) oxalate hexahydrate (Np(C2O4)-2∙6H2O; NpOx) and uranium(IV) oxalate hexahydrate (U(C2O4)-2∙6H2O; UOx) despite the high degree of unresolved disorder that exists when determining water positions in the crystal structures of the latter two compounds. Such assumptions regarding the isostructural behavior of the actinide elements have been used to predict the structure of PuOx for use in a wide range of studies. Herein, we report the first crystal structures for PuOx and Th(C2O4)2·6H2O (ThOx). This data, along with new characterization of UOx and NpOx, has resulted in the full determination of the structures and resolution of the disorder around the water molecules. Specifically, we identify the coordination of two water molecules with each metal center, which necessitates a change in oxalate coordination mode from axial to equatorial that has not been reported in the literature. This work exemplifiesthe need to revisit previous assumptions regarding fundamental actinide chemistry, which are heavily relied upon within the current nuclear field.

Modulating the electronic structure of CoFeCNO 2D nanosheets via Ni incorporation for efficient electrochemical oxygen evolution

Electronic modulation of electrocatalytic active sites by heteroatom doping has been widely recognized as an effective synthetic strategy to further enhance the intrinsic activity of oxygen evolution electrocatalysts. Incorporation of heteroatoms with different atomic radius and electronegativity into the material's lattice helps to induce subtle distortions in the material's lattice and redistribution of electron density, thereby precisely changing the electronic structure at the atomic level and enhancing catalysis active. By adjusting the ratio of metal and non-metal elements, a series of CoFeNiCNO sheet-like oxygen evolution electrocatalysts were prepared. Electrochemical characteristics showed that the overpotential of bimetallic CoFeNiCNO catalysts corresponding to 10 mA cm−2 only needs 290 mV, the Tafel slope is 98 mV dec−1, and it also has superior electrochemical stability in alkaline solution compared with that of bimetallic CoFeCNO catalysts. The doping of Ni ions in the material is closely related to the two-dimensional sheet structure of the material. This work provides a new idea for the preparation of low-cost nanosheet electrocatalysts for oxygen evolution, which is expected to be applied on a large scale in production and life.

Effect of heat treatment on compression properties of the 316L diamond structure fabricated through selective laser melting

Designing a triply periodic minimal surface (TPMS) lattice structure is a new method for lightweight. Compared with the previous foam- and strut-based structure, the TPMS lattice structure has the advantages of precise control of mechanical properties and convenient modelling. In this paper, under a quasi-static compression load, the effect of solution and aging treatment on the mechanical properties and energy absorption capacity of graded skeleton diamond (GSKD), graded sheet diamond (GSHD), uniform skeleton diamond (USKD) and uniform sheet diamond (USHD) fabricated through selective laser melting (SLM) were studied. The experiment results show that the sheet structures have better mechanical properties (elastic modulus, yield strength, platform stress and energy absorption) than the skeleton structures, and that the uniform structures have a higher energy absorption capacity (WV, εd) than the gradient structures, with the WV,εd of the as-built USHD sample reaching 2.11 times that of the GSKD sample. Moreover, the mechanical properties of each structure have different degrees of sensitivity to heat treatment conditions. Heat treatment has the greatest influence on the platform stress and initial strain of densification of GSKD, on the Young's modulus of USHD and on the energy absorption of USKD.