ACS Applied Engineering Materials最新文献

3D printing, particularly direct ink writing (DIW), offers a different approach to crafting intricate ceramic structures. Here, 3D printing technology (direct ink writing (DIW)) based on extrusion has been utilized to fabricate SiC ceramic structures. The particle size, binder composition, and printing conditions were optimized to fabricate high-strength green structures. The mechanical properties of the 3D-printed SiC green structure were infiltrated with the liquid precursor, which filled the porous part of the structure. The composite is fired at a higher temperature, which results in the formation of SiC from the liquid precursor, demonstrating improved surface morphology, strength, density, and thermal properties of the printed structures. The 3D-printed SiC composite structures show an increase in mechanical strength up to 600% stronger as compared to the pristine SiC structures. Furthermore, the infiltrated, sintered composite demonstrates superior thermal properties, notably improved heat dissipation, in contrast to noninfiltrated samples, rendering it well-suited for high-temperature applications. This method presents a promising avenue for manufacturing advanced SiC components with superior properties.

Commercialization of triboelectric nanogenerator (TENG) based self-powered sensors has become increasingly significant in the modern era, particularly within the realm of sustainable energy applications. However, the commercial viability of such self-powered sensors hinges on overcoming specific challenges, including the development of materials that excel in both durability and high charge transfer capabilities, addressing signal conditioning of high-amplitude voltage pulses, and integration with microcontrollers. Although rubber materials exhibit superior durability and are well-suited for high-load applications, their inherently low triboelectric performance limits their use in triboelectric sensors. Herein, highly durable and stretchable latex-compounded acrylonitrile butadiene rubber (NBR) based thin sheets are fabricated via the doctors’ blade technique to realize mechanical energy harvesting and to work as self-powered sensors such as speed sensors and direction sensors. The triboelectric positive material NBR offers good durability coupled with a high charge transfer density of 24 nC/cm² when paired with (indium tin oxide) ITO as a tribonegative material. The nitrile rubber is employed in a symmetric TENG structure to develop a road stud to perform self-powered speed-sensing applications. Integration with microcontrollers has enabled wireless speed monitoring, catering to high-speed applications with efficacy. Further, by leveraging NBR as an active tribopositive material, a highly responsive self-powered direction sensor is developed to detect forward and reverse human motions. Capacitor charging characteristics of TENG are utilized to address the challenges in controlling unregulated triboelectric voltage pulses, ensuring noise-free integration with microcontrollers, for real-time direction sensing. Finally, a triboelectric pedestrian crossing detector (PCD) integrating two triboelectric direction sensors was successfully demonstrated to count the number of passengers waiting to cross the road. Thus, the work appeals to highly demanded energy materials for high-energy impact applications and proposes a technology for conditioning unregulated high triboelectric voltage signals.

Frontal polymerization (FP) has emerged as a rapid and energy-efficient process for fabricating thermoset polymers and composites. In this process, a self-propagating reaction front cures the polymer rapidly by the exothermic heat of polymerization reaction instead of an external heat source. Design for FP-based manufacturing in commercial applications requires more comprehensive characterization and prediction of material evolution and residual deformation throughout the process. Here, we report experimental and numerical studies in response to this need. The experimental study focuses on measuring the temperature and cure-dependent properties of mono/poly dicyclopentadiene to capture the strain evolution during the frontal polymerization process. The experimentally measured elastic moduli, Poisson's ratios, and coefficients of thermal expansion and chemical shrinkage show strong dependence on the degree of cure. Based on the experimental output, a coupled thermo-chemo-mechanical model has been developed to capture the measured residual strains. The chemical shrinkage is closely related to the curing rate, leading to strong localization of residual strains in accelerated reaction regions, especially where two fronts merge. Preheating of the monomer (or gel) at the fronts merging area is suggested as an effective method to mitigate residual deformations.

Frontal polymerization (FP) has emerged as a rapid and energy-efficient process for fabricating thermoset polymers and composites. In this process, a self-propagating reaction front cures the polymer rapidly by the exothermic heat of polymerization reaction instead of an external heat source. Design for FP-based manufacturing in commercial applications requires more comprehensive characterization and prediction of material evolution and residual deformation throughout the process. Here, we report experimental and numerical studies in response to this need. The experimental study focuses on measuring the temperature and cure-dependent properties of mono/poly dicyclopentadiene to capture the strain evolution during the frontal polymerization process. The experimentally measured elastic moduli, Poisson’s ratios, and coefficients of thermal expansion and chemical shrinkage show strong dependence on the degree of cure. Based on the experimental output, a coupled thermo–chemo–mechanical model has been developed to capture the measured residual strains. The chemical shrinkage is closely related to the curing rate, leading to strong localization of residual strains in accelerated reaction regions, especially where two fronts merge. Preheating of the monomer (or gel) at the fronts merging area is suggested as an effective method to mitigate residual deformations.

In this study, we report a meticulously engineered electrocatalyst employing a multicomponent system consisting of Ce-doped NiMoO₄ nanorods as the primary component. The Ce-doped NiMoO₄ nanorods were primarily integrated with two-dimensional (2D) MoS₂ nanosheets and further modified with rGO, significantly enhancing the charge transport in the interfacial region of the hybrid nanoarchitecture (Ce-NiMoO₄/MoS₂@rGO). Cerium doping, combined with the multicomponent architecture, targeted toward enhancing the density of active sites and conductivity, which promoted efficient water decomposition. The synergistic effect of doping and heterostructure strategies resulted in efficient hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance of the Ce-NiMoO₄/MoS₂@rGO electrocatalyst. This electrocatalyst demonstrated impressive bifunctional activity with a low overpotential of 153 mV for the benchmark current of 10 mA cm^–2 and a Tafel slope of 82 mV dec^–1 for the HER. For the OER, an overpotential of 278 mV was observed for the cathodic current of 20 mA cm^–2 with a Tafel slope of 114 mV dec^–1. Additionally, our electrolyzer, utilizing Ce-NiMoO₄/MoS₂@rGO as electrodes, acquired a total current density of 10 mA cm^–2 at a full-cell voltage of 1.58 V. Moreover, the Ce-NiMoO₄/MoS₂@rGO heterostructure exhibited prolonged durability with minimal deactivation even after continuous operation for 24 h.

The directed propulsion of magnetic microrobots through structured environments often requires real-time feedback between external sensors and the applied field. This requirement, however, can be relaxed to enable self-guided propulsion by coupling field-driven motion to gradients in the local environment. We show that rotating fields direct the migration of ferromagnetic spheres up local gradients in the topography of a solid substrate. We quantify the speed and direction of particle migration as a function of the rotation frequency and incline angle. These observations are explained by a dynamic model that describes particle motion through the fluid due to the magnetic torque and gravitational force. We demonstrate how “topotaxis” can direct the simultaneous navigation of multiple particles on patterned arrays of concave bowls and convex domes without knowledge of the particle locations or the surface topography. These results highlight opportunities for designing time-varying fields to achieve other self-guided behaviors conditioned on local environmental cues.

Metal–organic frameworks (MOFs) represent a promising class of electrode materials for electrochemical energy storage systems due to their tunable morphology, high surface area, and chemical composition. However, the poor electron transport characteristics of MOFs have hindered their application in supercapacitor electrodes. Here, we report the seed-assisted synthesis of a freestanding composite featuring hydrangea flower-like Ni-MOF structures anchored on cobalt oxide (CoO_x)-embedded carbon nanofibers (Co-CNFs) as electrodes for superior asymmetric supercapacitors. The CoO_x nanoparticles serve as seeds that promote nucleation and modulate the growth of the Ni-MOF particles over the Co-CNF surface. The resulting Ni-MOF@Co-CNF composite exhibits a significantly high specific capacitance of 491 F g^–1 at a current density of 0.1 A g^–1 in a three-electrode system, surpassing the performance of both the individual components and the Ni-MOFs deposited onto the CNFs without any seed. This enhancement is accredited to the synergistic effect between Co-CNF and Ni-MOF, facilitating efficient dispersion of reaction active sites and promoting fast electron transfer through the conductive CNF matrix. The asymmetric supercapacitor (ASC) device with Ni-MOF@Co-CNF as a positive electrode demonstrates a specific capacitance of 126 F g^–1 (301 mF cm^–2) at a current density of 0.5 A g^–1. The ASC device exhibited a high energy density of 44.8 Wh kg^–1 (428.4 Wh cm^–2) at a power density of 0.4 kW kg^–1 (3.82 kW cm^–2). Furthermore, the quasi-solid-state ASC device (SASC) delivered a remarkable energy density of 35.6 Wh kg^–1 (340 Wh cm^–2) at a power density of 0.4 kW kg^–1 (3.82 kW cm^–2) with excellent cycling durability (∼89% capacitance retention after 10,000 charge/discharge cycles). This study highlights the significant potential of Ni-MOF@Co-CNF as electrodes in electrochemical energy storage applications.

Hydrogen embrittlement (HE) has been identified as a critical problem that impedes the safe, efficient, and economical storage and transportation of hydrogen. Here, we introduce the topic and alleviation of HE specifically for pipelines and storage containers, while placing emphasis on technological advancements in H₂ barrier coatings via polymer nanocomposite (PNC) technology. PNCs prepared as an emerging coating are investigated for the mitigation of HE in steels to enable safe hydrogen transmission via pipeline. This technology aims to address the shortcomings of pure polymer films in industry by incorporating the exceptional gas barrier properties and mechanical strength of nanofillers to enhance the polymer performance. Introducing high aspect ratio fillers such as nanoclays or graphene creates a layered brick-like structure reducing free volume and increasing tortuosity. The resulting composite will have the desirable adhesion, scalability, and versatility of polymeric materials while also showcasing the increased tensile strength and impermeability provided by the nanofiller. Provided herein is an evaluation of material suitability for both polymers and fillers including PNC structures, synthesis, processing requirements, and outlook on subsequent research directions.

This research introduces an innovative approach to enhancing materials for supercapacitors, as well as hydrogen evolution reactions. The study involves synthesizing two-dimensional nickel metal–organic frameworks on nickel foam and the oxide-based materials derived from them and investigating the influence of various surfactants on structural architecture. Among the surfactants, sodium dodecyl sulfate (SDS) displayed the most effective outcomes. The SDS-assisted Ni-MOF-derived NiO demonstrated better electrochemical characteristics when served as one of the electrodes in a supercapacitor exhibiting a high specific capacity of 841.2 C·g^–1 (equivalent to 1682.4 F·g^–1) when tested at 1 A·g^–1, and maintained 92.9% of this capacity after 5000 charge–discharge cycles. This represents significant improvements over surfactant-free materials, with a 26% increase in specific capacitance. In an asymmetric supercapacitor setup, the material demonstrated an impressive energy density (67.89 Wh·kg^–1) coupled with a power density of 750 W·kg^–1. When applied to the hydrogen evolution reaction, it reached 10 mA·cm^–2 with an overpotential of only 87 mV. It also showed a consistent performance over 24 h. The findings highlight how surfactant-assisted synthesis of Ni-MOF and subsequent derivation resulted in interlinked nanoparticle assemblies arranged in a hierarchical, blossom-like superstructure, which significantly enhances both electrochemical and hydrogen evolution performance. The study underscores the potential of tailored MOF synthesis in developing advanced materials for sustainable energy applications.

Smart textiles represent a groundbreaking innovation in integrating advanced sensing capabilities into surfaces previously deemed inaccessible and mark an advancement in the ongoing evolution of highly durable and flexible electronic textiles. The development of e-textiles with electrical circuits capable of withstanding diverse environmental stimuli, alongside repetitive bending and elongation cycles, has remained a critical challenge. In this study, we introduce a transformative approach to versatile sensory e-textiles utilizing a network of copper-coated Kevlar fibers. This approach leverages the synergistic coordination between a printable copper precursor and Kevlar fibers, resulting in robust, long-lasting conductive networks. These networks demonstrate unprecedented long-term cyclability, superior oxidation, and corrosion resistance and maintain stability even in harsh, oxidative environments. Furthermore, they exhibit remarkable washability, ensuring durability in real-world applications. Beyond their durability, these e-textiles perform multifunctional roles, including precise strain sensing and emissivity tuning, achieved through direct current modulation. The strain sensing performance is distinguished by its reliability under repeated 40 wt % stretching cycles. The innovation lies in the multilayered conductive structure, which guarantees continuous percolation, driving enhanced performance in both strain detection and emissivity control. This breakthrough offers a significant leap forward in the development of next-generation smart textiles with wide-ranging applications in wearable electronics, adaptive materials, and beyond.