Ultra-Small High-Entropy Alloy as Multi-Functional Catalyst for Ammonia Based Fuel Cells.

Ammonia fuel cells using carbon-neutral ammonia as fuel are regarded as a fast, furious, and flexible next-generation carbon-free energy conversion technology, but it is limited by the kinetically sluggish ammonia oxidation reaction (AOR), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER). Platinum can efficiently drive these three types of reactions, but its scale-up application is limited by its susceptibility to poisoning and high cost. In order to reduce the cost and alleviate poisoning, incorporating Pt with various metals proves to be an efficient and feasible strategy. Herein, PtFeCoNiIr/C trifunctional high-entropy alloy (HEA) catalysts are prepared with uniform mixing and ultra-small size of 2 ± 0.5 nm by Joule heating method. PtFeCoNiIr/C exhibits efficient performance in AOR (Jpeak = 139.8 A g-1 PGM), ORR (E1/2 = 0.87 V), and HER (E10 = 20.3 mV), outperforming the benchmark Pt/C, and no loss in HER performance at 100 mA cm-2 for 200 h. The almost unchanged E1/2 in the anti-poisoning test indicates its promising application in real fuel cells powered by ammonia. This work opens up a new path for the development of multi-functional electrocatalysts and also makes a big leap toward the exploration of cost-effective device configurations for novel fuel cells.

Electromagnetic Interference Shielding and Joule Heating Properties of Flexible, Lightweight, and Hydrophobic MXene/Nickel-Coated Polyester Fabrics Manufactured by Dip-Dry Coating and Electroless Plating.

High-performance electromagnetic interference (EMI) shielding materials with high flexibility, low density, and hydrophobic surface are crucial for modern integrated electronics and telecommunication systems in advanced industries like aerospace, military, artificial intelligence, and wearable electronics. In this study, we present flexible and hydrophobic MXene/Ni-coated polyester (PET) fabrics featuring a double-layered structure, fabricated via a facile and scalable dip-dry coating process followed by electroless nickel plating. Increasing the dip-dry coating iterations up to 10 cycles boosts the MXene loading content (∼31 wt %) and electrical conductivity (∼86 S/cm) of MXene-coated PET fabrics, while maintaining constant porosity (∼95%). The addition of a Ni layer enhances hydrophobicity, achieving a high water contact angle of ∼114° compared to only MXene-coated PET fabrics (∼49°). Furthermore, the 30 µm thick MXene/Ni-coated PET fabric demonstrates superior electrical conductivity (∼113.8 S/cm) and EMI shielding effectiveness (∼35.7 dB at 8-12 GHz) compared to only MXene- or Ni-coated PET fabrics. The EMI shielding performance of the MXene/Ni-coated PET fabric remains more stable in an air environment than only MXene-coated fabrics due to the outer Ni layer with excellent hydrophobicity and oxidation stability. Additionally, the MXene/Ni-coated PET fabric exhibits impressive Joule heating performance, swiftly converting electrical energy into heat and reaching high steady-state temperatures (32-92 °C) at low applied voltages (0.5-1.5 V).

Silver Coated Multifunctional Liquid Crystalline Elastomer Polymeric Composites as Electro-Responsive and Piezo-Resistive Artificial Muscles.

Liquid crystalline elastomers (LCEs) are a class of shape-changing polymers with exceptional mechanical properties and potential as artificial muscles/polymer actuators. In this study, multifunctional LCE actuators with strain sensing and joule heating responsivity are developed. LCEs are successfully synthesized using the thiol-ene two-staged michael addition polymerization (TMAP) method. The LCE films are further functionalized via sequential polydopamine (PDA) and silver electroless coating. It is found that the PDA coating enabled the anchoring of the Ag particles to the LCE, thereby enabling the electrical conductivity of the Ag-LCEs (<0.1 Ω cm-1). The studies confirm that the Ag/PDA coated LCEs can sense up to ≈30% strain, sense their own actuation strokes, and actuate at a rate of 1.83% s-1 while lifting a weight ≈50 times its mass in response to a 12 V 2A DC current.

Rapid Release of Silicon by Ultrafast Joule Heating Generates Mechanically Stable Shell-Shell Si/C Anodes with Dominant Inward Deformation.

As a promising anode material, silicon-carbon composites encounter great challenges related to internal stress release and contact between the composites during lithiation. These issues lead to material degradation and concomitantly rapid capacity decline. Here, we report a type of shell-shell silicon-carbon (SS-Si/C) composite, which consists of a carbon shell tightly coated with a silicon shell. The mechanical analysis unveils that the dominant inward expansion of the Si shell is achieved through the synergistic effect of the outer carbon shell and the inner hollow structure. Benefiting from the well-tailored shell-shell structure, the SS-Si/C anode exhibits exceptional performance, boasting a high specific capacity (1690.3 mA h g-1 after 550 cycles at 0.5 A g-1), a high areal capacity (2.05 mA h cm-2 after more than 400 cycles at 0.5 mA cm-2), and an extended cycling life (1055.6 mA h g-1 after 1000 cycles at 8 A g-1), far exceeding commercially available Si/C anodes. Using the well-designed SS-Si/C anode, full cells assembled with LiCoO2 (LCO) or LiFePO4 (LFP) cathodes achieve favorable rate capability and cyclic stability. Notably, at a high rate of 6 C (1 C = 170 and 270 mA g-1 for LFP and LCO, respectively), these full cells deliver high specific capacities of 79.5 mA h g-1 and 64.9 mA h g-1 when using LCO and LFP, respectively, demonstrating the potential of SS-Si/C anodes for practical applications. The straightforward and safe synthesis method in this work enables the rational design of hollow structures with distinct properties.

Self-Healable Interfaces with Improved Mechanical Properties Induced by Dynamic Network Reconfiguration in Carbon Fiber-Reinforced Epoxy Laminates.

Interfacial failure in carbon fiber-reinforced epoxy (CFRE) laminates is a prominent mode of failure, attracting significant research attention. The large surface-energy mismatch between carbon fiber (CF) and epoxy results in a weaker interface. This study presents a facile yet effective method for enhancing the interfacial adhesion between CF and epoxy with self-healable interfaces. Two variants of a designer sizing agent, poly(ether imide) (PEI), were synthesized, one without a self-healing property termed BO, and the second one by incorporating disulfide metathesis in one of its monomers that renders self-healing properties at the interface-mediated by network reconfiguration, termed BA. 0.25 wt % of CF was found to be the optimum amount of BO and BA sizing agents. The surface free energy of CF drastically increased and became quite close to the surface energy of epoxy after the deposition of both sizing agents and the higher surface roughness. The improved surface wettability, presence of functional groups, and mechanical interlocking worked in tandem to strengthen the interface. The interlaminar shear strength (ILSS) and flexural strength (FS) of CFRE laminate sized with BO consequently increased by 35% and 22% and of CFRE laminate sized with BA increased by 26% and 19%, respectively. Fractography analysis revealed outstanding bonding between epoxy and PEI-CF, indicating that matrix fracture is the predominant mode of failure. The self-healable interfaces due to the preinstalled disulfide metathesis in the sizing agent resulted in 51% self-healing efficiency in ILSS for BA-sized CFRE laminate. Interestingly, the functional properties, deicing, and EMI shielding effectiveness were not compromised by modification of the interface with this designer sizing agent. This study opens new avenues for interfacial modification to improve the mechanical properties while retaining the key functional properties of the laminates.

Computational modelling of micropolar blood-based magnetised hybrid nanofluid flow over a porous curved surface in the presence of artificial bacteria.

This work provides a brief comparative analysis of the influence of heat creation on micropolar blood-based unsteady magnetised hybrid nanofluid flow over a curved surface. The Powell-Eyring fluid model was applied for modelling purposes, and this work accounted for the impacts of both viscous dissipation and Joule heating. By investigating the behaviours of Ag and TiO2 nanoparticles dispersed in blood, we aimed to understand the intricate phenomenon of hybridisation. A mathematical framework was created in accordance with the fundamental flow assumptions to build the model. Then, the model was made dimensionless using similarity transformations. The problem of a dimensionless system was then effectively addressed using the homotopy analysis technique. A cylindrical surface was used to calculate the flow quantities, and the outcomes were visualised using graphs and tables. Additionally, a study was conducted to evaluate skin friction and heat transfer in relation to blood flow dynamics; heat transmission was enhanced to raise the Biot number values. According to the findings of this study, increasing the values of the unstable parameters results in increase of the blood velocity profile.

PVDF Hybrid Nanocomposites with Graphene and Carbon Nanotubes and Their Thermoresistive and Joule Heating Properties.

In recent years, conductive polymer nanocomposites have gained significant attention due to their promising thermoresistive and Joule heating properties across a range of versatile applications, such as heating elements, smart materials, and thermistors. This paper presents an investigation of semi-crystalline polyvinylidene fluoride (PVDF) nanocomposites with 6 wt.% carbon-based nanofillers, namely graphene nanoplatelets (GNPs), multi-walled carbon nanotubes (MWCNTs), and a combination of GNPs and MWCNTs (hybrid). The influence of the mono- and hybrid fillers on the crystalline structure was analyzed by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). It was found that the nanocomposites had increased amorphous fraction compared to the neat PVDF. Furthermore, nanocomposites enhanced the ß phase of the PVDF by up to 12% mainly due to the presence of MWCNTs. The resistive properties of the nanocompositions were weakly affected by the temperature in the analyzed temperature range of 25-100 °C; nevertheless, the hybrid filler composites were proven to be more sensitive than the monofiller ones. The Joule heating effect was observed when 8 and 10 V were applied, and the compositions reached a self-regulating effect at around 100-150 s. In general, the inclusion in PVDF of nanofillers such as GNPs and MWCNTs, and especially their hybrid combinations, may be successfully used for tuning the self-regulated Joule heating properties of the nanocomposites.

Considering Joule heating in coupled electroporation and electrodeformation modeling of glioblastoma cells.

Cells exposed to a pulsed electric field undergo electroporation(EP) and electrodeformation(ED) under electric field stress, and a coupled model of EP and ED of glioblastoma(GBM) taking into account Joule heating is proposed. The model geometry is extracted from real cell boundaries, and the effects of Joule heating-induced temperature rise on the EP and ED processes are considered. The results show that the temperature rise will increase the cell's local conductivity, leading to a decrease in the transmembrane potential(TMP). The temperature rise also causes a decrease in the dynamic Young's modulus of the cell membrane, making the cell less resistant to deformation. In addition, GBM cells are more susceptible to EP in the middle portion of the cell and ED in the three tentacle portions under pulsed electric fields, and the cells undergo significant positional shifts. The ED of the nucleus is similar to spherical cells, but the degree of ED is smaller.

Changes in Current Transport and Regulation of the Microstructure of Graphene/Polyimide Films under Joule Heating Treatment.

The excellent electrical properties of graphene have received widespread attention. However, the difficulty of electron transfer between layers still restricts the application of graphene composite materials to a large extent. Therefore, in this study, graphene/polyimide films were subjected to a Joule heating treatment to improve the electrical conductivity of the film by ~76.85%. After multiple Joule thermal cycle treatments, the conductivity of the graphene/polyimide film still gradually increased, but the increase in amplitude tended to slow down. Finally, after eight Joule heat treatments, the conductivity of the graphene/polyimide film was improved by ~93.94%. The Joule heating treatment caused the polyimide to undergo atomic rearrangement near the interface bonded to the graphene, forming a new crystalline phase favourable for electron transport with graphene as a template. Accordingly, a model of the bilayer capacitive microstructure of graphene/polyimide was proposed. The experiment suggests that the Joule heating treatment can effectively reduce the distance between graphene electrode plates in the bilayer capacitive micro-nanostructures of graphene/polyimide and greatly increases the number of charge carriers on the electrode plates. The TEM and WAXS characterisation results imply atomic structure changes at the graphene/polyimide bonding interface.

Recyclable Polymer Composites with a Wrinkled Core-Shell Structure for Highly Efficient EMI Shielding and Low Reflection.

Green electromagnetic interference (EMI) shielding materials not only require high shielding effectiveness (SE) and low reflection but also need to be recyclable after damage; however, it is challenging to strike a balance in practice. Here, a polyacrylamide (PAM) composite composed of numerous chemically cross-linked PAM@carbon nanotube (cPAM@CNT) core-shell particles featuring rich wrinkled microstructures was prepared using an adsorption-drying-shrinking strategy. The wrinkled microstructures enable the incident electromagnetic waves (EMWs) to undergo attenuation within the composites, achieving an average EMI SE of 67.5 dB in the X band. Due to the hygroscopicity of hydrophobically associated PAM (hPAM, an adhesive for cPAM@CNTs core-shell particles), the average EMI SE of the composites further increased to 83.2 dB after exposure to 91% relative humidity for 24 h, with only a 2.7 dB low reflection. Additionally, the composites also demonstrated excellent Joule heating, photothermal performance, and recyclability, which exhibit substantial promise for advanced EMI shielding applications.

Grain Boundary Defect Engineering in Rutile Iridium Oxide Boosts Efficient and Stable Acidic Water Oxidation.

Proton exchange membrane water electrolysis (PEMWE) is considered a promising technology for coupling with renewable energy sources to achieve clean hydrogen production. However, constrained by the sluggish kinetics of the anodic oxygen evolution reaction (OER) and the acidic abominable environment render the grand challenges in developing the active and stable OER electrocatalyst, leading to low efficiency of PEMWE. Herein, we develop the rutile-type IrO2 nanoparticles with abundant grain boundaries and the continuous nanostructure through the joule heating and sacrificial template method. The optimal candidate (350-IrO2) demonstrates remarkable electrocatalytic activity and stability during the OER, presenting a promising advancement for efficient PEMWE. DFT calculations verified that grain boundaries can modulate the electronic structure of Ir sites and optimize the adsorption of oxygen intermediates, resulting in the accelerated kinetics. 350-IrO2 affords a rapid OER process with 20 times higher mass activity (0.61 A mgIr -1) than the commercial IrO2 at 1.50 V vs. RHE. Benefiting from the reduced overpotential and the preservation of the stable rutile structure, 350-IrO2 exhibits the stability of 200 h test at 10 mA cm-2 with only trace decay of 11.8 mV. Moreover, the assembled PEMWE with anode 350-IrO2 catalyst outputs the current density up to 2 A cm-2 with only 1.84 V applied voltage, long-term operation for 100 h without obvious performance degradation at 1 A cm-2.

Heat Dissipation Mechanisms in Hybrid Superconductor-Semiconductor Devices Revealed by Joule Spectroscopy.

Understanding heating and cooling mechanisms in mesoscopic superconductor-semiconductor devices is crucial for their application in quantum technologies. Owing to their poor thermal conductivity, heating effects can drive superconducting-to-normal transitions even at low bias, observed as sharp conductance dips through the loss of Andreev excess currents. Tracking such dips across magnetic field, cryostat temperature, and applied microwave power allows us to uncover cooling bottlenecks in different parts of a device. By applying this "Joule spectroscopy" technique, we analyze heat dissipation in devices based on InAs-Al nanowires and reveal that cooling of superconducting islands is limited by the rather inefficient electron-phonon coupling, as opposed to grounded superconductors that primarily cool by quasiparticle diffusion. We show that powers as low as 50-150 pW are able to suppress superconductivity on the islands. Applied microwaves lead to similar heating effects but are affected by the interplay of the microwave frequency and the effective electron-phonon relaxation time.

Graphene Derived from Municipal Solid Waste.

Landfilling is long the most common method of disposal for municipal solid waste (MSW). However, many countries seek to implement different methods of MSW treatment due to the high global warming potential associated with landfilling. Other methods such as recycling and incineration are either limited to only a fraction of generated MSW or still produce large greenhouse gas emissions, thereby providing an unsustainable disposal method. Here, the production of graphene from treated MSW is reported that including treated wood waste, using flash Joule heating. Results indicated a 71%-83% reduction in global warming potential compared to traditional disposal methods at a net cost of -$282 of MSW, presuming the graphene is sold at just 5% of its current market value to offset the cost of the flash Joule heating process.

Ultrafast-Loaded Nickel Sulfide on Vertical Graphene Enabled by Joule Heating for Enhanced Lithium Metal Batteries.

The design and fabrication of a lithiophilic skeleton are highly important for constructing advanced Li metal anodes. In this work, a new lithiophilic skeleton is reported by planting metal sulfides (e.g., Ni3S2) on vertical graphene (VG) via a facile ultrafast Joule heating (UJH) method, which facilitates the homogeneous distribution of lithiophilic sites on carbon cloth (CC) supported VG substrate with firm bonding. Ni3S2 nanoparticles are homogeneously anchored on the optimized skeleton as CC/VG@Ni3S2, which ensures high conductivity and uniform deposition of Li metal with non-dendrites. By means of systematic electrochemical characterizations, the symmetric cells coupled with CC/VG@Ni3S2 deliver a steady long-term cycle within 14 mV overpotential for 1800 h (900 cycles) at 1 mA cm-2 and 1 mAh cm-2. Meanwhile, the designed CC/VG@Ni3S2-Li||LFP full cell shows notable electrochemical performance with a capacity retention of 92.44% at 0.5 C after 500 cycles and exceptional rate performance. This novel synthesis strategy for metal sulfides on hierarchical carbon-based materials sheds new light on the development of high-performance lithium metal batteries (LMBs).

Bio-based epoxy resin/carbon nanotube coatings applied on cotton fabrics for smart wearable systems.

Electroactive coatings for smart wearable textiles based on a furan bio-epoxy monomer (BOMF) crosslinked with isophorone diamine (IPD) and additivated with carbon nanotubes (CNTs) are reported herein. The effect of BOMF/IPD molar ratio on the curing reaction, as well as on the properties of the crosslinked resins was first assessed, and it was found that 1.5:1 BOMF/IPD molar ratio provided higher heat of reaction, glass transition temperature, and mechanical performance. The resin was then modified with CNT to prepare electrically conductive nanocomposite films, which exhibited conductivity values increased by eight orders of magnitude upon addition of 5 phr of CNTs. The epoxy/CNT nanocomposites were finally applied as coatings onto a cotton fabric to develop electrically conductive, hydrophobic and breathable textiles. Notably, the integration of CNTs imparted efficient and reversible electrothermal behavior to the cotton fabric, showcasing its potential application in smart and comfortable wearable electronic devices.

Microheater Chips with Carbon Nanotube Resistors.

The specific and excellent properties of the low-dimensional nanomaterials have made them promising building blocks to be integrated into microelectromechanical systems with high performances. Here, we present a new microheater chip for in situ TEM, in which a cross-stacked superaligned carbon nanotube (CNT) film resistor is located on a suspended SiNx membrane via van der Waals (vdW) interactions. The CNT microheater has a fast high-temperature response and low power consumption, thanks to the micro/nanostructure of the CNT materials. Moreover, the membrane bulging amplitude is significantly reduced to only ∼100 nm at 800 °C for the vdW interaction between the CNTs and the SiNx membrane. An in situ observation of the Sn melting process is successfully conducted with the assistance of a customized flexible temperature control system. The uniform wafer-scaled CNT films enable a high level of consistency and cost-effective mass production of such chips. The as-developed in situ chips, as well as the related techniques, hold great promise in nanoscience, materials science, and electrochemistry.

Ruthenium-Based Binary Alloy with Oxide Nanosheath for Highly Efficient and Stable Oxygen Evolution Reaction in Acidic Media.

Traditional noble metal oxide, such as RuO2, is considered a benchmark catalyst for acidic oxygen evolution reaction (OER). However, its practical application is limited due to sluggish activity and severe electrochemical corrosion. In this study, Ru-Fe nanoparticles loading on carbon felt (RuFe@CF) is synthesized via an ultrafast Joule heating method as an active and durable OER catalyst in acidic conditions. Remarkably low overpotentials of 188 and 269 mV are achieved at 10 and 100 mA cm-2, respectively, with a robust stability up to 620 h at 10 mA cm-2. When used as an anode in a proton exchange membrane water electrolyzer, the catalyst shows more than 250 h of stability at a water-splitting current of 200 mA cm-2. Experimental characterizations reveal the presence of a Ru-based oxide nanosheath on the surface of the catalyst during OER tests, suggesting a surface reconstruction process that enhances the intrinsic activity and inhibits continuous metal dissolution. Moreover, density functional theory calculations demonstrate that the introduction of Fe into the RuFe@CF catalyst reduces the energy barrier and boosts its activities. This work offers an effective and universal strategy for the development of highly efficient and stable catalysts for acidic water splitting.

Thermoelectric Limitations of Graphene Nanodevices at Ultrahigh Current Densities.

Graphene is atomically thin, possesses excellent thermal conductivity, and is able to withstand high current densities, making it attractive for many nanoscale applications such as field-effect transistors, interconnects, and thermal management layers. Enabling integration of graphene into such devices requires nanostructuring, which can have a drastic impact on the self-heating properties, in particular at high current densities. Here, we use a combination of scanning thermal microscopy, finite element thermal analysis, and operando scanning transmission electron microscopy techniques to observe prototype graphene devices in operation and gain a deeper understanding of the role of geometry and interfaces during high current density operation. We find that Peltier effects significantly influence the operational limit due to local electrical and thermal interfacial effects, causing asymmetric temperature distribution in the device. Thus, our results indicate that a proper understanding and design of graphene devices must include consideration of the surrounding materials, interfaces, and geometry. Leveraging these aspects provides opportunities for engineered extreme operation devices.

Stretchable and Transparent Heaters Based on Hydrophobic Ionogels with Superior Moisture Insensitivity.

Flexible and stretchable transparent heaters (THs) have been widely used in various applications, including deicing and defogging of flexible screens as well as thermotherapy pads. Ionic THs based on ionogels have emerged as a promising alternative to conventional electronic THs due to their unique advantages in terms of transparency-conductance conflict, uniform heating, and interfacial adhesion. However, the commonly used hydrophilic ionogels inevitably introduce a moisture-sensitive issue. In this work, we present a stretchable and transparent hydrophobic ionogel-based heater that utilizes ionic current-induced Joule heating under high-frequency alternating current. This ionogel-based TH exhibits exceptional multifunctional properties with low hysteresis, a fracture strain of 840%, transmittance of 93%, conductivity of 0.062 S m-1, temperature resistance up to 165 °C, voltage resistance up to 120 V, heating rate of 0.1 °C s-1, steady-state temperature at 115 °C, and uniform heating even when bent or stretched (up to 200%). Furthermore, it maintains its heating performance when it is directly exposed to water. This hydrophobic ionogel-based TH expands the range of materials available for ionic THs and paves the way for their practical applications.

MHD free convection with Joule heating and entropy generation inside an H-shaped hollow structure.

In this research, a free convective flow of water inside an H-shaped hollow structure which is subjected to the existence of an exterior magnetic field and Joule heating is computationally investigated. The structure's right and left upright surfaces are maintained at invariant ambient thermal condition, while the top and bottom-most surfaces of the structure are in adiabatic condition. The rest of the inner walls are heated isothermally. Computational analysis is carried out for different configurations of the chamber by solving Navier-Stokes and heat energy equations via the finite element approach. Parametric computations are conducted by varying Hartmann numbers (0 ≤ Ha ≤ 20), Rayleigh numbers (103 ≤ Ra ≤ 106), width of the vertical sections (0.2 ≤ d/L ≤ 0.4, where L denotes the structure's reference dimension), and thickness of the horizontal middle section (0.2 ≤ t/L ≤ 0.4). To find out the impact of the governing parameters on thermal performance for different configurations, the mean Nusselt number along the hot walls, mean temperature of fluid, overall entropy generation, and thermal performance criterion are assessed. In addition, the variations in fluid motion and thermal patterns are reported in terms of streamlines, isotherms, and heatlines. With a larger mean Nusselt number and smaller thermal performance criterion, better heat transmission performance is found for thicker horizontal middle section and wider vertical sections. The maximum reduction in thermal performance criterion is found to be 87.8 % for increasing the width of the vertical sections. However, in the cases of Ha and d/L, there is an interesting transition in Nusselt number noticed for different Rayleigh numbers.