Layered Microstructures Research Articles

The discovery of two-dimensional (2D) ferromagnetic semiconductors holds significant promise for advancing Moore's law and spintronics in-memory computing, sparking tremendous interest. However, the Curie temperature of explored 2D ferromagnetic semiconductors is much lower than room temperature. Although plenty of 2D room-temperature ferromagnetic semiconductors have been theoretically predicted, there have been formidable challenges in preparing such metastable materials with ordered structures and high stability. Here, utilizing a novel template-assisted chemical vapor deposition strategy, we synthesized layered MnS2 microstructures within a ReS2 template. The high-resolution atomic structure representation revealed that monolayer MnS2 microstructures well crystallize into a distorted T-phase. Room-temperature ferromagnetism was confirmed through vibrating sample magnetometer measurements, microzone magnetism imaging techniques, and transport characterization. Theoretical calculations indicated that the room-temperature ferromagnetism originates from the Mn-Mn short-range interaction. Our observation not only offered the experimental confirmation of the intrinsic room-temperature ferromagnetism in layered MnS2, but also provided an innovative strategy for the growth of 2D metastable functional materials.

In the artificial fabrication of microstructured ceramics with platelets, precisely controlling the local alignment of microstructural units and constructing complex macroscopic geometries remain critical challenges. Herein, an inert film with microgrooves is introduced into the ceramic printing process, and a novel microgroove-assisted ceramic stereolithography approach is proposed. By combining microgroove geometry and layered printing, the local flow field generated during platform positioning through the interaction between the slurry and the microgrooves is harnessed to drive the orientation of alumina platelets and to form layered microstructures and non-flat interfaces between layers. The flow-driven orientation mechanism of the platelets is elucidated. After sintering, grain orientations are effectively controlled, and microgroove-scale textured microstructures are introduced within each layer. A gradient distribution of hardness is formed along the microgroove. The warpage in the sintered samples is reduced. These layered microstructures further influence crack extension and deflection. Printing results using films with pits and letter arrays demonstrate that this mechanism can form more complex microstructures. This approach provides a fast, stable, and effective flow-driven orientation mechanism for platelets in high-solid-content ceramic slurry, which controls the layered distribution of designed microstructure patterns within the 3D-printed ceramics.

Biological materials such as seashell nacre exhibit extreme mechanical properties due to their multilayered microstructures. Collaborative interaction among these layers achieves performance beyond the capacity of a single layer. Inspired by these multilayer biological systems, we architect materials with free-form layered microstructures to program multistage snap-buckling and plateau responses-accomplishments challenging with single-layer materials. The developed inverse design paradigm simultaneously optimizes local microstructures within layers and their interconnections, enabling intricate layer interactions. Each layer plays a synergistic role in collectively achieving high-precision control over the desired extreme nonlinear responses. Through high-fidelity simulations, hybrid fabrication, and tailored experiments, we demonstrate complex responses fundamental to various functionalities, including energy dissipation and wearable devices. We orchestrate multisnapping phenomena from complex interactions between heterogeneous local architectures to encode and store information within architected materials, unlocking data encryption possibilities. These layered architected materials offer transformative advancements across diverse fields, including vibration control, wearables, and information encryption.

Cement-based materials are the foundation of modern buildings but suffer from intensive energy consumption. Utilizing cement-based materials for efficient energy storage is one of the most promising strategies for realizing zero-energy buildings. However, cement-based materials encounter challenges in achieving excellent electrochemical performance without compromising mechanical properties. Here, we introduce a biomimetic cement-based solid-state electrolyte (labeled as l-CPSSE) with artificially organized layered microstructures by proposing an insitu ice-templating strategy upon the cement hydration, in which the layered micropores are further filled with fast-ion-conducting hydrogels and serve as ion diffusion highways. With these merits, the obtained l-CPSSE not only presents marked specific bending and compressive strength (2.2 and 1.2 times that of traditional cement, respectively) but also exhibits excellent ionic conductivity (27.8 mS·cm-1), overwhelming most previously reported cement-based and hydrogel-based electrolytes. As a proof-of-concept demonstration, we assemble the l-CPSSE electrolytes with cement-based electrodes to achieve all-cement-based solid-state energy storage devices, delivering an outstanding full-cell specific capacity of 72.2 mF·cm-2. More importantly, a 5 × 5 cm2 sized building model is successfully fabricated and operated by connecting 4 l-CPSSE-based full cells in series, showcasing its great potential in self-energy-storage buildings. This work provides a general methodology for preparing revolutionary cement-based electrolytes and may pave the way for achieving zero-carbon buildings.

Synchrotron radiation dynamic imaging technology combined with the static characterization method was used to study the microstructural evolution and the growth kinetics of intermetallic compounds (IMCs) at the liquid Al/solid Cu interface. The results show that the interfacial microstructure can be divided into layered solid diffusion microstructures (AlCu3, Al4Cu9, Al2Cu3 and AlCu) and solidification microstructures (Al3Cu4, AlCu and Al2Cu) from the Cu side to the Al side. Meanwhile, the growth of bubbles formed during the melting, holding and solidification of an Al/Cu sample was also discussed, which can be divided into three modes: diffusion, coalescence and engulfment. Moreover, the growth of AlCu3 and (Al4Cu9 + Al2Cu3) near the Cu side is all controlled by both interfacial reaction and volume diffusion. The growth of Al3Cu4 adjacent to the melt is mainly controlled by the interfacial reaction, which plays a major role in the growth of the total IMCs.

Bioceramics are widely used in bone tissue repair and regeneration due to their desirable biocompatibility and bioactivity. However, the brittleness of bioceramics results in difficulty of surgical operation, which greatly limits their clinical applications. The spicules of the marine sponge Euplectella aspergillum (Ea) possess high flexibility and fracture toughness resulting from concentric layered silica glued by a thin organic layer. Inspired by the unique properties of sponge spicules, flexible bioceramic-based scaffolds with spicule-like concentric layered biomimetic microstructures were constructed by combining two-dimensional (2D) bioceramics and 3D printing. 2D bioceramics could be assembled and aligned by modulating the shear force field in the direct ink writing (DIW) of 3D printing. The prepared spicules-inspired flexible bioceramic-based (SFB) scaffolds differentiated themselves from traditional 3D-printed irregular particles-based bioceramic-based scaffolds as they could be adaptably compressed, cut, folded, rolled and twisted without the occurrence of fracture, significantly breaking through the bottleneck of inherent brittleness of traditional bioceramic scaffolds. In addition, SFB scaffolds showed significantly enhanced in vitro and in vivo bone-forming bioactivity as compared to conventional β-tricalcium phosphate (β-TCP) scaffolds, suggesting that SFB scaffolds combined both of excellent mechanical and bioactive characteristics, which is believed to greatly promote the bioceramic science and their clinical applications.

Electrochemical CO2 reduction (ECR) to value-added fuels and chemical feedstocks driven by renewable energy sources is one promising approach to alleviating the ever-increasing atmospheric CO2 concentration and the rapid fossil fuels consumption.1,2 Among various products formed, formate is a very attractive product due to its wide applications in textile and pharmaceutical industries, and in fuel cells as the hydrogen carrier. Bi in particular has been widely investigated as advanced catalyst for formate production because of their cost-effectiveness, low toxicity, and high activity. Up to date, various strategies including size, morphology, defect, grain boundary, and heterostructure engineering have been developed to improve the catalytic performances of Bi-based catalysts. Despite some exciting achievements, the performances over Bi-based catalysts still fall behind the commercial requirements. Most existing catalysts suffer from low formate production rate (in H-type cell) because high standard of catalytic activity and product selectivity could be hardly achieved simultaneously. On the other side, desirable formate faradaic efficiency (FE) of ˃90 % can be only achieved in a narrow potential window owing to the competing hydrogen evolution reaction (HER) at high potential. Therefore, developing Bi-based catalysts for formate production via ECR with high formation rate and current density over a broad potential window is a top priority but remains as great challenges. Electronic regulation of electrocatalysts via element doping has been regarded as a powerful strategy to enhance the electrochemical activity of ECR. The introduction of heteroatoms can regulate the electron density and thus, precisely modify the electronic structures of the active sites, resulting in optimal adsorption energy of the reaction intermediates. S modification of catalysts can modulate the electronic structure of catalysts, thus boosting the electrocatalytic activity for HER, 3 oxygen evolution reaction (OER),4 and oxygen reduction reaction (ORR).5 Moreover, S doping can increase the adsorption capacity of CO2 and decrease the energy barrier for the formation of *HCOO intermediate.6 To that end, S doping is expected to be an effective strategy to improve the catalytic performance of ECR by tuning the electronic structure. However, the studies on fine-tuning the electronic structure of Bi-based catalysts for ECR by S doping have rarely been reported so far; a comprehensive understanding of the S doping effect on the ECR activity is also lacking. The study demonstrates S doped Bi2O3 nanosheets coupled with carbon nanotube (S-Bi2O3-CNT) as catalyst for ECR to formate production. The prepared S2-Bi2O3-CNT with the S doping amount of 0.7 at % achieved high FE over a wide potential range, and also achieved high partial current density (48.6 mA cm-2) and good long-term stability. Experimental results and a series of characterizations highlighted the advantages of S doping which facilitates electron transfer, increases the adsorption of CO2 and offers more undercoordinated Bi sites. Moreover, DFT results reveal that S doping induced the electronic delocalization of Bi sites, which optimized the adsorption of *CO2 and *HCOO intermediates while hindering the adsorption of *H. Therefore, S doped Bi2O3 promotes the ECR to formate by supressing the competitive HER simultaneously. This work opens up an attractive avenue for developing highly efficient electrocatalyst for ECR at atomic level.References Nielsen, D. U.; Hu, X.-M.; Daasbjerg, K.; Skrydstrup, T., Chemically and electrochemically catalysed conversion of CO2 to CO with follow-up utilization to value-added chemicals. Nat. Catal. 2018, 1, 244-254.Ross, M. B.; De Luna, P.; Li, Y.; Dinh, C.-T.; Kim, D.; Yang, P.; Sargent, E. H., Designing materials for electrochemical carbon dioxide recycling. Nat. Catal. 2019, 2, 648-658.Yu, J.; Guo, Y.; Miao, S.; Ni, M.; Zhou, W.; Shao, Z., Spherical ruthenium disulfide-sulfur-doped graphene composite as an efficient hydrogen evolution electrocatalyst. ACS Appl. Mater. Interfaces 2018, 10, 34098-34107. Yu, L.; Wu, L.; McElhenny, B.; Song, S.; Luo, D.; Zhang, F.; Yu, Y.; Chen, S.; Ren, Z., Ultrafast room-temperature synthesis of porous S-doped Ni/Fe (oxy) hydroxide electrodes for oxygen evolution catalysis in seawater splitting. Energy Environ. Sci. 2020, 13, 3439-3446.Wang, Y. C.; Lai, Y. J.; Song, L.; Zhou, Z. Y.; Liu, J. G.; Wang, Q.; Yang, X. D.; Chen, C.; Shi, W.; Zheng, Y. P., S‐doping of an Fe/N/C ORR catalyst for polymer electrolyte membrane fuel cells with high power density. Angew. Chem., Int. Ed. 2015, 54, 9907-9910. 6. Tian, W.; Zhang, H.; Sun, H.; Suvorova, A.; Saunders, M.; Tade, M.; Wang, S., Heteroatom (N or N‐S)‐Doping Induced Layered and Honeycomb Microstructures of Porous Carbons for CO2 Capture and Energy Applications. Adv. Funct. Mater. 2016, 26, 8651-8661.

Report is devoted to investigations of graphene meta–surfaces for the transmission of radiation induced by plasmons in subTHz and THz ranges, cell of which consists of structures based on graphene ring and graphene nano–tape. It create regimes of radiation transmission – transparency windows induced by electric dipole resonances. Resonant frequency of transparency window can be dynamically tuned in wide band of subTHz and THz bands by changing the chemical potential (Fermi energy) of graphene by applying external electric field (gating) instead of re–fabricating of structures. Questions of possibilities of electronic controlled filters creating of subTHz and THz bands grounded on different configurations of graphene meta–surfaces are discussed; their characteristics and frequency dependencies are investigated. Mathematical modelling and electrodynamic calculation of the filters characteristics of subTHz and THz bands grounded on multilayer structures of “graphene–dielectric” type are carried out. From results of mathematical modelling it follows that periodic layered microstructures “graphene–dielectric” type can be used for creation of subTHz and THz bands broadband filters of planar construction, controlling by electric field and fast tuning at small changes in Fermi energy level of graphene.

Microstructure – Property correlations for additively manufactured NiTi based shape memory alloys

Centimeter size BiSeI crystal grown by physical vapor transport method

Tribological contacts consume a significant amount of the world's primary energy due to friction and wear in different products from nanoelectromechanical systems to bearings, gears, and engines. The energy is largely dissipated in the material underneath the two surfaces sliding against each other. This subsurface material is thereby exposed to extreme amounts of shear deformation and often forms layered subsurface microstructures with reduced grain size. Herein, the elementary mechanisms for the formation of subsurface microstructures are elucidated by systematic model experiments and discrete dislocation dynamics simulations in dry frictional contacts. The simulations show how pre-existing dislocations transform into prismatic dislocation structures under tribological loading. The stress field under a moving spherical contact and the crystallographic orientation are crucial for the formation of these prismatic structures. Experimentally, a localized dislocation structure at a depth of ≈100-150 nm is found already after the first loading pass. This dislocation structure is shown to be connected to the inhomogeneous stress field under the moving contact. The subsequent microstructural transformations and the mechanical properties of the surface layer are determined by this structure. These results hold promise at guiding material selection and alloy development for tribological loading, yielding materials tailored for specific tribological scenarios.

Effective properties of layered auxetic hybrids

Charge transport and film microstructure evolution are investigated in a series of polyethylenimine (PEI)-doped (0.0-6.0 wt%) amorphous metal oxide (MO) semiconductor thin film blends. Here, PEI doping generality is broadened from binary In2O3 to ternary (e.g., In+Zn in IZO, In+Ga in IGO) and quaternary (e.g., In+Zn+Ga in IGZO) systems, demonstrating the universality of this approach for polymer electron doping of MO matrices. Systematic comparison of the effects of various metal ions on the electronic transport and film microstructure of these blends are investigated by combined thin-film transistor (TFT) response, AFM, XPS, XRD, X-ray reflectivity, and cross-sectional TEM. Morphological analysis reveals that layered MO film microstructures predominate in PEI-In2O3, but become less distinct in IGO and are not detectable in IZO and IGZO. TFT charge transport measurements indicate a general coincidence of a peak in carrier mobility (μpeak) and overall TFT performance at optimal PEI doping concentrations. Optimal PEI loadings that yield μpeak values depend not only on the MO elemental composition but also, equally important, on the metal atomic ratios. By investigating the relationship between the MO energy levels and PEI doping by UPS, it is concluded that the efficiency of PEI electron-donation is highly dependent on the metal oxide matrix work function in cases where film morphology is optimal, as in the IGO compositions. The results of this investigation demonstrate the broad generality and efficacy of PEI electron doping applied to electronically functional metal oxide systems and that the resulting film microstructure, morphology, and energy level modifications are all vital to understanding charge transport in these amorphous oxide blends.

Planar metal-supported cell designs provide cost-effective scaling-up of solid oxide fuel cells and electrolysers. Here, we report on the fabrication of a BaZr0.85Y0.15O3−δ–NiO (BZY15–NiO) composite electrode and BaZr0.85Y0.15O3−δ (BZY15) proton-conducting electrolyte films on metal and ceramic substrates using pulsed laser deposition (PLD). The results demonstrate successful sequential deposition of porous electrode and dense electrolyte structure by PLD at moderate temperatures, without the need for subsequent high-temperature sintering. The decrease in roughness of the metal substrate used for deposition by spray-coating intermediary oxide layers had significant importance to the fabrication of functional layers as thin films. Crystalline porous BZY15–NiO and dense BZY15 films were sequentially deposited at high substrate temperature on metal supports (MS) with or without an electron-conducting barrier oxide layer, e.g. MS/(BZY15–Ni)/(BZY15–NiO)/BZY15 and MS/CeO2/(BZY15–NiO)/BZY15. The different microstructures for electrode and electrolyte were achieved with deposition steps at different substrate temperatures (800, 600 °C) and a gradual decrease in the pressure of O2 in the deposition chamber.

The shape memory effect (SME) in alloys with a thermoelastic martensite transition opens unique opportunities for the creation of miniature mechanical devices. The SME has been studied in layered composite microstructures consisting of a Ti2NiCu alloy and platinum. It occurs upon a decrease in the active layer thickness at least to 80 nm. Some physical and technological restrictions on the minimum size of a material with SME are discussed.

CoFeSiB–Pd multilayers and co-deposited alloy films exhibiting perpendicular magnetic anisotropies after heat treatment up to 500 °C

Porous Carbon: Heteroatom (N or N‐S)‐Doping Induced Layered and Honeycomb Microstructures of Porous Carbons for CO₂ Capture and Energy Applications (Adv. Funct. Mater. 47/2016)

Increasing global challenges such as climate change, environmental pollution, and energy shortage have stimulated the worldwide explorations into novel and clean materials for their applications in the capture of carbon dioxide, a major greenhouse gas, and toxic pollutants, energy conversion, and storage. In this study, two microstructured carbons, namely N‐doped pillaring layered carbon (NC) and N, S codoped honeycomb carbon (NSC), have been fabricated through a one‐pot pyrolysis process of a mixture containing glucose, sodium bicarbonate, and urea or thiourea. The heteroatom doping is found to induce tailored microstructures featuring highly interconnected pore frameworks, high sp2‐C ratios, and high surface areas. The formation mechanism of the varying pore frameworks is believed to be hydrogen‐bond interactions. NSC displays a similar CO2 adsorption capacity (4.7 mmol g−1 at 0 °C), a better CO2/N2 selectivity, and higher activity in oxygen reduction reaction as compared with NC‐3 (the NC sample with the highest N content of 7.3%). NSC favors an efficient four‐electron reduction pathway and presents better methanol tolerance than Pt/C in alkaline media. The porous carbons also exhibit excellent rate performance as supercapacitors.

Thermoelectric materials can generate electricity by harnessing the temperature gradient and lowering the temperature through applying electromotive force. Lead chalcogenides based materials, especially PbTe-based ones, have shown extremely high thermoelectric performance. PbSe has a similar crystal structure and band structure to PbTe. Compared with the commonly-used PbTe, PbSe possesses a high melting point and has an abundant reserve of Se, making it attractive to high temperature thermoelectric applications. It has been theoretically proposed that Mn-doping in lead chalcogenide should be able to lower the temperature of band degeneracy, and experimental evidences have been represented in Mn-PbTe. However, such an experimental study as well as the investigations of influences of Mn on microstructure, mechanical, electrical and thermal properties has not been conducted in Mn-PbSe. In this work, Pb0.98-xMnxNa0.02Se (0 x 0.12) materials are prepared by the melting-quenching techniques combined with rapid hot-press sintering. Effects of Mn doping on the microstructures, mechanical and thermoelectric properties of PbSe samples are systematically studied. The refined lattice parameters from X-ray powder diffraction patterns show that the solubility of Mn in the matrix is in a range from 0 to 0.04. The back-scattered electron images and elemental maps reveal that the MnSe-rich impurity phases exist in the PbSe matrix, which makes the PbSe-MnSe system a nano-composite system. Pb0.96Mn0.02Na0.02Se has also such microstructures, implying that the solubility of Mn should be below 0.02. Cubic-phase MnSe-rich precipitates have the sizes ranging from 50 nanometers to 1-5 micrometers. They are well dispersed in the PbSe-rich matrix, as round or layered microstructures. The mechanical properties of the nanocomposites can be determined by micro-hardness measurements. Interestingly, the average Vickers hardness values of the PbSe-MnSe nanocomposites are significantly improved, which are 16.6% and 51.6% harder respectively in x= 0.02 and 0.06 samples than those of pristine PbSe. Smaller Mn content can optimize the figure of merit ZT due to the band convergence and additional phonon scattering by precipitates, while higher Mn content has little influence on ZT because of the saturated Seebeck coefficient and anomalous increase in lattice thermal conductivity. As a result, the highest figure of merit is 0.52 at 712 K, which is achieved in the Pb0.96Mn0.02Na0.02Se sample. By further adjusting the Na content from 2% to 0.7%, the carrier concentration is optimized. Thus, the Seebeck coefficient and power factor become higher. A figure of merit of 0.65 is achieved at 710 K in the PbSe-MnSe nano-composite with a nominal composition of Pb0.973Mn0.02Na0.007Se. We suggest that further optimizing the electrical properties may achieve a higher thermoelectric performance in the PbSe-MnSe system.

Mechanism of macroscopic shear band formation in plane strain compressed fine-grained aluminium