Nanostructured Layer Research Articles

Anodization of cast and sintered Fe40Al alloy in etidronic acid: Morphological and semiconductive properties of the oxide films

Fe40Al alloys produced by casting and sintering were anodized to form nanostructured oxide layers. Microstructural characterization revealed a lower grain size for the sintered alloy compared to the cast alloy. Anodizing was performed in four electrolytes with a constant etidronic acid concentration (0.3 M) and different ethylene glycol-water ratios. Different voltages (5–400 V) and treatment times (1–4 hours) were evaluated for cast and sintered Fe40Al alloys. Among the studied anodization regimes, only four anodic films formed on sintered Fe40Al were homogeneous. These films were annealed at 900°C and analyzed by conventional characterization techniques (SEM/EDS and XRD). Results indicated a non-self-ordered morphology and different content of P, Fe, and Al species as a function of the electrolyte composition. Annealing post-treatment led to the formation of Fe/Al oxides and spinels in selected anodic films. An additional peak of FePO4 was detected only in the anodic film formed in pure ethylene glycol. The band gap values (UV-Vis reflectance spectroscopy) of the anodic film formed in ethylene glycol decreased from 2.87 eV to 2.45 eV after annealing. This band gap decrease was associated with the preferential formation of conductive phases (Fe2O3 and FeAlO3) over insulating phases (γ-Al2O3 and FeAl2O4) after annealing.

Ambient Deposition of Single Atoms for Enhancement of Nanostructured Metal Oxide Electrode Catalytic Performance

Single-atom decoration represents cutting-edge technology for enhancing heterogeneous catalysis by utilizing the unique capabilities of catalysts at the atomic level. However, the high surface energy of single atoms often causes them to aggregate, forming nanoparticles [1]. To address this challenge, we first modify the surface structure by synthesizing nanostructured support layers, such as TiO2 nanotubes, TiO2 nanosheets, and NiO nanosponge. Especially TiO2 nanotubes and NiO nanosponge pose relevant support layers due to their favorable attributes, including a high surface-to-volume ratio, abundance, and excellent chemical stability, while TiO2 nanosheets serve as model system. Vertically aligned, well-ordered, self-organized oxide nanostructures can be conveniently fabricated through anodization, allowing precise control over the geometry of the nanotubes and nanopores [2,3]. Well-defined atomic-scale defects on the surface of the supports are generated to immobilize single-atom co-catalysts. Therefore, defect engineering techniques typically require high-temperature thermal reduction. We present more gentle defect-engineering approaches, including room-temperature sonochemical treatment or UV-light irradiation. By combining these approaches, we are able to effectively trap Pt and Ir single atoms.We present a direct method utilizing UV-light radiation to induce point defects, specifically Ti3+ and oxygen vacancies (VO) onto the surface of TiO2 nanosheets and efficiently decorate them with Pt single atoms [4]. Our findings demonstrate that sonochemically treated TiO2 nanotubes provide a remarkable substrate for single-atom decoration from dilute solutions, resulting in promising performance in H2 evolution catalysis and renewable energy conversion. Additionally, the role of V single-atom decoration in ultrasonic treatment of support materials is investigated.Thermal annealing in a reductive atmosphere induces the formation of numerous defects, facilitating the anchoring of single Ir atoms onto the surface of annealed NiO nanostructures. Additionally, the novel ultrasound-driven method stabilizes these Ir atoms within the porous structure. By employing both approaches, we effectively trap Ir single atoms, thereby enhancing the efficiency of the oxygen evolution reaction in electrocatalysis [5].The characterization of the electrodes is conducted using microscopy techniques (FESEM, TEM, and HAADF-STEM) and spectroscopy (XPS and ToF-SIMS) [6]. Gas chromatography is employed to evaluate the H2 photocatalytic performance of TiO2 electrodes, while linear sweep voltammetry is utilized to assess the H2 and O2 electrochemical activity of NiO electrodes [5]. Our findings highlight the significant enhancement of photo- and electrocatalytic efficiency of nanostructured oxide electrodes modified with highly stable single-atom co-catalysts by gentle treatments.

Quantification of Hydrogen and Transition Metals in the Cathode Catalyst Layer of Anion Exchange Membrane Electrolyzer By Ion Beam Techniques

Anion Exchange Membrane Water Electrolyzer (AEMWE) has increased interest in H2 production at low cost and high scalability. The efficiency is strongly dependent on the membrane electrode assembly (MEA) with appropriate ionomer and catalyst layers. Herein, we report AEMWE with MoNi4-MoO2 cathode catalyst layer in ionomer-free Catalyst Coated Substrate (CCS) configuration. The optimized MEA for AEMWE demonstrated the superior performance of 225 mA/cm2 at 2V with more than 48 hours of durability. The X-ray diffraction confirmed the NiMoO4 phase transformation to MoNi4-MoO2 and SEM-EDS was used to study the morphology and elemental composition of the deposited catalyst. X-ray photoelectron Spectroscopy demonstrated the dominant metallic MoO2 formed after H2/Ar annealing. Rutherford Backscattering Spectroscopy (RBS) was also employed to measure the depth composition profile of the catalyst layer exhibiting the reduction of Ni concentration in the bulk after annealing. Further, we introduce hydrogen depth profiling by Nuclear Reaction Analysis (NRA) via the resonant 1H(15N,αγ)12C reaction as a versatile method for the highly depth-resolved visualization of hydrogen(H) in the near-surface region, including transitions of hydrogen between the surface and the bulk, and between shallow interfaces of the nanostructured cathode catalyst layer. The diffusion of the H atoms was observed with a 40% atomic percent of Hydrogen after H2/Ar annealing of the catalyst for 180 minutes (about 3 hours) and decreased to 10% atomic percent of hydrogen after 24 hours of electrolyzer operation. This technique also enabled the measurement of the zero-point vibrational energy of hydrogen atoms absorbed on the surfaces of the catalyst layer. Overall, this work better explains the cathode catalyst degradation effects and hydrogen diffusion in the cathode catalyst layer responsible for voltage and mass transfer losses in AEM electrolyzers.

Mangenese Copper Selenide Nanosheet Arrays Derived from Metal-Organic Frameworks for Efficient Solid-State Asymmetric Supercapacitors

Metal chalcogenide nanostructures, particularly metal selenides, have unique properties, such as high electrical conductivity, large specific surface area, exclusive porous networks, and exceptional electrochemical properties compared to traditional nanostructures.1 2 A novel strategy is proposed to design and fabricate hierarchical Manganese copper selenide nanosheet (MnCuSe NS) arrays from metal-organic frameworks (MOFs). The hierarchical MnCuSe NS arrays can deliver enriched electroactive sites and shorten the ion/electron diffusion pathways. When evaluated as positive electrodes for supercapacitor (SC), the MnCuSe NS electrode displayed remarkable electrochemical properties with ultra-high specific capacity of ≈350.4 mA h g− 1 and an areal capacity of ≈0.94 mA h cm− 2 at a current density of 3 mA cm− 2, exceptional rate capability (≈79.5% of the capacity retention at a higher current density of 50 mA cm− 2), and outstanding cyclic stability (≈95.4 % of capacity retention after 10 000 cycles). Most importantly, the assembled MnCuSe NS//FeMnO/NG solid-state asymmetric SC exhibited a wide operating potential window of 1.6 V with an ultra-high volumetric capacity of ≈2.4 mA h cm− 3 at a current density of 3 mA cm− 2, an excellent energy density of ≈71.6 Wh Kg− 1 at a power density of ≈794 W Kg− 1, and ultra-long cycle life (≈93.4 % of capacity retention after 10 000 cycles). This proposed method provides a general protocol to design and fabricate metal selenide nanosheet arrays with superior electrochemical energy storage properties and exceptional cyclic stability, holding significant potential for future energy storage devices in commercial aspects. Keywords: Hierarchical, Metal-organic frameworks, Metal chalcogenide, Energy density, Asymmetric supercapacitorsReference:(1) Han, J. H.; Kwak, M.; Kim, Y.; Cheon, J. Recent Advances in the Solution-Based Preparation of Two-Dimensional Layered Transition Metal Chalcogenide Nanostructures. Chem. Rev. 2018, 118 (13), 6151–6188. https://doi.org/10.1021/acs.chemrev.8b00264.(2) Karuppasamy, K.; Vikraman, D.; Hussain, S.; Kumar Veerasubramani, G.; Santhoshkumar, P.; Lee, S.-H.; Bose, R.; Kathalingam, A.; Kim, H.-S. Unveiling a Binary Metal Selenide Composite of CuSe Polyhedrons/CoSe2 Nanorods Decorated Graphene Oxide as an Active Electrode Material for High-Performance Hybrid Supercapacitors. Chemical Engineering Journal 2022, 427, 131535. https://doi.org/10.1016/j.cej.2021.131535.

Micropatterning MXene/TiO2 Nanocomposite Ink for Gas Sensing

This work describes the preparation, characterization and micropatterning of MXene (Ti3C2/TiO2) nanocomposite inks. The MXene nanopowder was oxidized to Ti3C2/TiO2 nanocomposite powder by stirring in air for 3 hours using air aging method. The Ti3C2/TiO2 nanocomposite powder was then dispersed into Dimethyl Sulfoxide (DMSO) solvent, and the Ti3C2/TiO2 ink was prepared by using 1% mass fraction of Polyvinylpyrrolidone (PVP) solution as dispersant. The two-dimensional layered nanostructure of MXene and the characteristic peaks of TiO2 were observed by Raman and XRD results. SEM and TEM results show the layered structure of MXene nanoparticles as well as TiO2 nanoparticles with a diameter of about 2 nm on a single layer of MXene. FTIR results confirms that Ti-O bonds and Ti-C bonds indicating that part of Ti3C2 was oxidized to TiO2. The results of Brunauer Emmett Teller (BET) test on Ti3C2/TiO2 nanocomposite ink show that the specific surface area of the ink is 10.7194 m²/g and the maximum adsorption of N2 is 32.039cm3/g. Thermogravimetric analysis (TGA) indicate that Ti3C2/TiO2 exhibited excellent thermal stability, with a mass loss of only 15% at 800°C. In order to achieve the optimal printing effect, plasma surface treatment was carried out on the gold-plated silicon wafers, Polyethylene terephthalate (PET), and glass substrates, which decreases the contact angle of the ink on these substrates. The printing of Ti3C2/TiO2 nanocomposite ink on the substrate using the atomized printing technique with a mask plate enables printing of straight lines with a line width of 5µm. Film thickness can be controlled by adjusting the distance between the printhead and the substrate, as well as the pressure of the atomized printing jet.

Mechanical milling promotes the preparation of catalyst lanthanum dodecyl sulfate and green solvent-free grinding for synthesis of N-heterocyclic derivatives

The lanthanum dodecyl sulfate catalyst (La(DS)3) was synthesized using a solvent-free mechanical ball method and applied in the preparation of solvent-free N-heterocyclic compounds. The preparation of the La(DS)3 catalyst and the synthesis of C-N bond series compounds only require brief ball milling of the mixed material at room temperature. Various analyses such as SEM, HRTEM, XRD, AFM, FT-IR, XPS, TGA, and DFT were conducted, which showed that the catalyst material synthesized by mechanical ball milling exhibited superior catalytic activity, thermal stability, and cyclic life compared to similar materials synthesized in an aqueous phase. The solvent-free catalytic synthesis of quinoxaline, dihydroacridin-1(2H)-one, and bis(indolyl)methanes derivatives achieved excellent target yields. Furthermore, the catalyst could be reused at least seven times without a significant decrease in activity after simple treatment. The catalyst also demonstrated gram scale scaling up in the model reaction. It exhibited weak hydrophilicity and a stable network-like layered nanostructure.

Laser ablation and chemical vapor deposition to prepare a nanostructured PPy layer on the Ti surface

Abstract The deposition of polypyrrole (PPy) on a Ti surface is commonly employed to enhance the material’s properties for different applications such as supercapacitors, biomedicine, and corrosion resistance. Instead of complex or costly polymerization procedures for the PPy synthesis on the Ti metal surface, we utilized the effect of a simple and inexpensive laser ablation of the Ti surface in the open-air environment to prepare a hydrophilic TiO2 surface. In this condition, a thin PPy layer with remarkable nanostructures such as nanorings (∼80 nm) and nanotubes (∼245 nm) was deposited on a selective and desired pattern of ablated Ti areas through the chemical vapor deposition process using ferric chloride (FeCl3) solution as a pyrrole oxidizer. Raman and X-ray photoelectron spectroscopy (XPS) analyses confirmed the PPy formation on the Ti surface. The creation of these nanostructures was due to the micro/nanomorphology of the ablated Ti substrate. Water contact angle (WCA) measurements indicated the hydrophobic behavior of the PPy/Ti surface by the aging effect after 24 weeks with the change of WCA from 20° to 116°. The change in the surface chemical composition upon adsorption of airborne organic compounds with the long-term storage of PPy/Ti surface in air was studied by the XPS test.

Generative Artificial Intelligence for Designing Multi-Scale Hydrogen Fuel Cell Catalyst Layer Nanostructures.

Multiscale design of catalyst layers (CLs) is important to advancing hydrogen electrochemical conversion devices toward commercialized deployment, which has nevertheless been greatly hampered by the complex interplay among multiscale CL components, high synthesis cost and vast design space. We lack rational design and optimization techniques that can accurately reflect the nanostructure-performance relationship and cost-effectively search the design space. Here, we fill this gap with a deep generative artificial intelligence (AI) framework, GLIDER, that integrates recent generative AI, data-driven surrogate techniques and collective intelligence to efficiently search the optimal CL nanostructures driven by their electrochemical performance. GLIDER achieves realistic multiscale CL digital generation by leveraging the dimensionality-reduction ability of quantized vector-variational autoencoder. The powerful generative capability of GLIDER allows the efficient search of the optimal design parameters for the Pt-carbon-ionomer nanostructures of CLs. We also demonstrate that GLIDER is transferable to other fuel cell electrode microstructure generation, e.g., fibrous gas diffusion layers and solid oxide fuel cell anode. GLIDER is of potential as a digital tool for the design and optimization of broad electrochemical energy devices.

Copper Oxide Electrochemical Deposition to Create Antiviral and Antibacterial Nanocoatings.

The impact of the reaction environment on the formation of the polycrystalline layer and its biomedical (antimicrobial) applications were analyzed in detail. Copper oxide layers were synthesized using an electrodeposition technique, with varying additives influencing the morphology, thickness, and chemical composition. Scanning electron microscopy (SEM) images confirmed the successful formation of polyhedral structures. Unmodified samples (CuL) crystallized as a mixture of copper oxide (I) and (II), with a thickness of approximately 1.74 μm. The inclusion of the nonconductive polymer polyvinylpyrrolidone (PVP) during synthesis led to a regular and compact CuO-rich structure (CuL-PVP). Conversely, adding glucose resulted in forming a Cu2O-rich nanostructured layer (CuL-D(+)G). Both additives significantly reduced the sample thickness to 617 nm for CuL-PVP and 560 nm for CuL-D(+)G. The effectiveness of the synthesized copper oxide layers was demonstrated in their ability to significantly reduce the T4 phage titer by approximately 2.5-3 log. Notably, CuL-PVP and CuL-D(+)G showed a more substantial reduction in the MS2 phage titer, achieving about a 5-log decrease. In terms of antibacterial activity, CuL and CuL-PVP exhibited moderate efficacy against Escherichia coli, whereas CuL-D(+)G reduced the E. coli titer to undetectable levels. All samples induced similar reductions in Staphylococcus aureus titer. The study revealed differential susceptibilities, with Gram-negative bacteria being more vulnerable to CuL-D(+)G due to its unique composition and morphology. The antimicrobial properties were attributed to the redox cycling of Cu ions, which generate ROS, and the mechanical damage caused by nanostructured surfaces. A crucial finding was the impact of surface composition rather than surface morphology on antimicrobial efficacy. Samples with a dominant Cu2O composition exhibited potent antibacterial and antiviral properties, whereas CuO-rich materials showed predominantly enhanced antiviral activity. This research highlights the significance of phase composition in determining the antimicrobial properties of copper oxide layers synthesized through electrodeposition.

Exploring the performance of Co/Al2O3–ZrO2 nanocatalysts developed through the thermal evaporation method in dry reforming of methane

Abstract This study aimed to investigate the performance of the thin layer nanostructures of Co/Al2O3–ZrO2 in the dry reforming of methane (DRM) in a microchannel reactor. The nanostructures were prepared via utilizing the thermal evaporation method. Reactor tests were carried out at various coating times of 2, 3, and 4 min and temperatures of 700, 750, and 800 °C with a feed flow rate of 10 ml/min and a 1:1:8 ratio of helium, carbon dioxide, and methane. Also, grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDX) were used to identify catalyst features. According to the obtained results, the highest percentage of conversion in all samples was observed at 800 °C. The results of the reactor tests also revealed that the activity of catalyst layers highly depends on coating time. The findings demonstrated that raising deposition time improves the distribution of particle size and catalyst loading. Considering the nanostructure of Co/Al2O3–ZrO2, the sample undergoing 4 min coating time yielded the highest amount of primary methane conversion (89.3 %), primary carbon dioxide conversion (92.4 %), and H2/CO molar ratio (0.91). The stability test of the catalyst layers for 28 h at the optimum condition (P = 1 atm, T = 800 °C, t = 4 min deposition time, CH4/CO2 = 1, and GHSV = 48,000 mL g−1 h−1) showed that the catalysts prepared by this method had a good stability.

Femtosecond laser darkened copper surfaces: Characterization for possible application as laser beam blocker

This study focuses on the optical and mechanical properties of copper surfaces darkened by femtosecond laser irradiation, with regard to their applicability as laser beam blockers. Copper surfaces were processed with a Ti-Sapphire laser (1 kHz repetition rate, ∼100–600 mJ/cm2 fluence), while scanning parameters were optimized for low reflectivity and processing speed. A total reflectivity below 6 % was obtained for the 250–2500 nm wavelength range. SEM imaging and ion beam etching showed submicron period structures covered with high density nanoparticles, with a total depth of ∼3–4 μm. Numerical reflectivity simulations suggest that besides the structures, the formation of oxides also contributes to the observed darkening. Thermal and mechanical stability, chemical resistance and laser damage threshold were studied. Temperatures above 200 °C caused surface degradation. Scratch tests showed that the nanostructured layers could withstand ∼60 MPa contact pressure. The surfaces could resist 48 h treatment with various acids at 10−3 M concentration. The laser damage threshold for the applied femtosecond laser showed that the surface could withstand the unfocused beam of most high-frequency femtosecond lasers. The results indicate that laser darkened copper can be a promising candidate for use in laser beam blockers.

Determination of methyl parathion and fenitrothion on a Mg-Al layered double hydroxide/poly-m-amino-benzenesulfonic acid film-coated glassy carbon electrode (Mg-Al LDH/p-m-ABSA/GCE)

A novel nonenzymatic electrochemical sensor with high sensitivity for detecting organic phosphate (OPS) in medicinal herbs was fabricated based on a Mg-Al layered double hydroxide (Mg-Al LDH) nanocomposite glassy carbon electrode (GCE) modified with a poly-m-amino-benzenesulfonic acid (p-m-ABSA) film. Depositing Mg-Al LDH nanocomposites onto the surface of the p-m-ABSA composite resulted in an effective electrical response by increasing the electrode surface area and enhancing the electron transfer process, so the electrocatalytic activity was significantly enhanced. The research illustrated that the fabricated sensor (Mg-Al LDH/p-m-ABSA/GCE) exhibited strong affinity, high sensitivity, and selectivity towards methyl parathion (MP) and fenitrothion (FNT). Scanning electron microscopy (SEM) was used to characterize the surface morphology of the modified electrode and showed that the p-m-ABSA film and a few p-m-ABSA nanoparticles were coated on the surface. The surface area of the electrode was further enlarged by Mg-Al LDH owing to their layered nanostructure. Under optimal conditions, the anodic current had a linear relation equal to 0.1∼20.0 µM MP and 0.01∼50.0 µM FNT, with detection limits (S/N = 3) of 33.0 nM MP and 3.5 nM FNT, respectively. Furthermore, Mg-Al LDH/p-m-ABSA/GCE was successfully used for the detection of MP and FNT in Astragalus and Magnolia medicinal herb samples.

Full-colour-sorting metalens based on guided mode resonance

Full-colour-sorting metalens using few nanostructured layers have recently generated considerable interest as high-sensitivity colour image sensors because of their reliability and high resolution. Based on the guided mode resonance principle and propagation phase modulation, a full-colour-sorting metalens is designed, which can theoretically obtain any wavelength of light from the incident white light and realize arbitrary wavelength focusing with the same focal length in the visible range. Without the loss of generality, we propose a prototype of such metalens used for sorting blue, green and red light from the visible spectrum commonly used in practical applications. The maximum focussing efficiency is over 50% with a relatively high numerical aperture of 0.7. The proposed full-colour-sorting metalens can be used in many applications, such as colour mixing, colour holography, colour filtering, wavelength division multiplexing and so on.

An Ultralight Composite Current Collector Enabling High-Energy-Density and High-Rate Anode-Free Lithium Metal Battery.

Anode-free lithium (Li) metal batteries are promising alternatives to current Li-ion batteries due to their advantages such as high energy density, low cost, and convenient production. However, the copper (Cu) current collector accounts for more than 25 wt% of the total weight of the anode-free battery without capacity contribution, which severely reduces the energy and power densities. Here, a new family of ultralight composite current collectors with a low areal density of 0.78mg cm-2, representing significant weight reduction of 49%-91% compared with the Cu-based current collectors for high-energy Li batteries, is presented. Rational molecular engineering of the polyacylsemicarbazide substrate enables enhanced interfacial interaction with the sputtered Cu layer, which results in excellent interfacial stability, flexibility, and safety for the obtained anode-free batteries. The battery-level energy density has been significantly improved by 36%-61%, and a maximum rate capability reaches 5 C (10mA cm-2) attributed to the homogeneous Li+ flux and smooth Li deposition on the nanostructured Cu layer. The results not only open a new avenue to improve the energy and power densities of anode-free batteries via composite current collector innovation but, in a broader context, provide a new paradigm to pursue high-performance, high-safety, and flexible batteries.

Carbazole–pyrene-based nonvolatile solid additive to modulate the electronic structures of photodynamic devices

Modulating the nanostructures of the active layers of optoelectronic devices via various techniques is crucial for enhancing the performances of these devices. However, commonly used liquid additives pose challenges in ensuring device-to-device reproducibility due to their effects on polymer solubility and the restriction of kinetic dynamics during film formation. To address these challenges, designing and incorporating solid additives that are independent of dynamics yet possess properties conducive to efficient charge transport into morphology modulation are important. Herein, a novel small molecule (9-(heptadecan-9-yl)-3,6-bis(5-(pyren-1-yl) thiophen-2-yl)-9H-carbazole (Cb-Th-Py)) is synthesized by combining a carbazole derivative with pyrene in an A-D-A structure. The bulk-heterojunction (BHJ) PM6:Y6 comprising Cb-Th-Py exhibits a smooth morphology. Additionally, via energy-level regulation, a higher electron injection barrier at reverse bias is induced, contributing to effective reduction of dark current. Particularly, Cb-Th-Py demonstrates high miscibility with Y6, ensuring an efficient charge transport pathway via strengthened π–π stacking, leading to a dense BHJ surface. This improves the charge mobility, decreases the trap density, and enhances the photocurrent of BHJ in addition to considerably suppressing noise. These Cb-Th-Py BHJ-based devices offer a more reproducible and effective avenue for performance enhancement of optoelectronics.

Enhanced strength-ductility synergy in pure Cu through the design of alternating coarse-grained and nanostructured layers

Heterogeneous micro/nano laminated structure (HM/NLS) design has emerged as a promising strategy for circumventing the strength-ductility trade-offs in nanostructured metals. However, most of reported HM/NLSed metals are mainly prepared from two dissimilar metals, which make it challenging to fully understand the deformation mechanisms of HM/NLS due to the complicated coupling of microstructural and compositional difference between component layers. Here, a series of HM/NLSs, consisting of alternating coarse-grained (CGed) and nanostructured (NSed) layers with varied thickness ratio (RCGed/NSed) of CGed layers to NSed layers, have been designed and introduced into pure Cu, which aim to exclude the influence of compositional difference between component layers and investigate the effect of microstructural difference on the deformational behavior of HM/NLSed metals independently. The effects of RCGed/NSed on the mechanical property of HM/NLSed Cu were investigated and an optimized strength-ductility synergy was achieve when RCGed/NSed = 2:3. Loading-unloading-reloading tests and in situ EBSD characterization reveal that the huge microstructural discrepancy between the neighboring CGed and NSed layers promotes dislocations accumulation and produces strong back stress strengthening during plastic deformation, thereby achieving a high yield strength ∼296 MPa and large uniform elongation of ∼18%. The results of this work will provide a viable approach for fabricating high-performance HM/NLSed metals and deepen the understanding of the underlying deformation mechanisms of HM/NLSed metals.

Synthesis of integrated reduced graphene oxide‐polyaniline nanocomposite for enhanced supercapacitor performance

AbstractThe urgent need for sustainable energy storage solutions has spurred research on high‐performance and cost‐effective energy storage technologies. Supercapacitors (SCs) show great potential due to their capacity to provide significant capacitance, energy and power density. This study focused on the enhancement of electrically conductive reduced Graphene Oxide (rGO) reinforced with polyaniline (PANI) composites to fabricate the supercapacitors. Various characterization techniques, including SEM, EDAX, Raman spectroscopy, FTIR, PXRD, TGA, BET, and CV were employed for the examination of the materials. The findings demonstrate that the rGO/PANI composite displayed nanostructured layers characterized by flaky leaf‐like structures, a trigonal crystal system, and a notable specific capacitance of 410 Fg−1, along with capacitance retention rate of 85 after completion of 1000 cycles. This composite showcases outstanding electrochemical performance leads to the promising material to use in SCs manufacturing.Highlights Electrode showed pseudocapacitive behavior, capacitance of 392 F/g. PXRD pattern confirmed presence of benzenoid and quinonoid groups. BET analysis showed surface area of 16.850 m2/g, porous nature indicated. Electrode displayed good reversibility, with a‐b value of 0.6.

Resistive switching properties of a nanostructured layer of mixed ZrO2 phases obtained in low-pressure arc discharge plasma

The controlled vacuum-arc synthesis of zirconium dioxide (ZrO2) nanoparticles is considered, which makes it possible to regulate the percentage ratio of the monoclinic and tetragonal phases. The samples were characterized using XRD analysis, SEM, HRTEM analysis, FT-IR analysis, TG/DTA analysis and EPR spectroscopy. It has been established that the formation of the tetragonal phase is associated with the formation of a large number of oxygen vacancies formed due to high-speed quenching of nanoparticles. Reducing the operating gas pressure in a vacuum chamber from 180 Pa to 30 Pa makes it possible to obtain nanoparticles up to 2 nm in size. The synthesized ZrO2 nanoparticles do not contain foreign impurities and when heated, the weight loss is up to 7 %. The process of local resistive switching in the contact of an atomic force microscope (AFM) probe to a nanostructured ZrO(2-x) layer on a conducting substrate has been studied. Cyclic current-voltage characteristics demonstrate the existence of stable states of high and low resistance, switched by changing the polarity of the applied voltage. The coexistence of the m- and t-ZrO2 phases (and the resulting oxygen nonstoichiometry in the interboundary regions) provides conditions for the formation/destruction of a filament from oxygen vacancies, which determine the conductivity of the dielectric in the LRS state.

Flexible NH3 gas sensors based on ZnO nanostructures deposited on kevlar substrates via hydrothermal method

Owing to their flexibility and high thermal resistance, para-aramid based Kevlar™ fabric substrates are an ideal candidate for obtaining flexible gas sensors for new-generation wearable technologies. The morphology of the surface of the substrate where the target gas comes into contact directly affects the important features of the sensor such as detection limit, selectivity, and response. In this context, a feasible technique is introduced to enhance the efficiency of flexible gas sensors utilizing ZnO/Kevlar™, entailing the modification of ZnO morphology. ZnO based gas sensing layers were deposited on Kevlar™ fabric substrates by a two-stage method. Initially, seed layer was produced on Kevlar™ fabric using the ultrasonic bath method, with five different seed layer processing times ranging from 1 min to 20 min. In the nucleation, all nanostructured layers were deposited by hydrothermal method with constant parameters and under the same conditions. As the seeding time was increased, nanorods (1D) formed on the surface became flakes (2D), leading to considerable improvement in NH3 gas sensing properties. The sensor with a 5-min seeding time showed a sensitivity of 49 % at an optimal operating temperature of 190 °C, while the sensor produced in 20 min showed the best response performance with 169 % at 130 °C for 50 ppm NH3 gas. The increase in seeding time not only reduced the operating temperature of the gas sensor through the conversion from 1D nanostructure to 2D, but also significantly increased the sensor response. Under constant hydrothermal conditions and solution concentration, the density per unit area increases. However, after 10 min of seeding, the length of nanorods shortens and turn into a rod-flake hybrid morphology. A superior sensor performance was demonstrated for the samples examined. The obtained results also showed that flexible Kevlar™ fabric could be a feasible and interesting substrate for nanostructured ZnO-based NH3 gas sensors.

Formation of nanocrystalline and nanolaminate structures in a twinning induced plasticity Ti-12Mo alloy: The role played by {332} 〈113〉 twinning

Grain refinement is an effective strategy to strengthen metastable β titanium alloys. {332}<113> twinning, a typical deformation mode, its role on grain refinement still remains unelucidated. Here, we produced a gradient nanostructured layer with a depth of 800 μm in a metastable twinning induced plasticity β-Ti-12Mo (wt.%) alloy by means of surface mechanical rolling treatment. We found that {332}<113> deformation twinning, mainly dominated the deformation at moderate strain and strain rates, refining coarse grains into submicro-structures. With increasing strain and strain rates, dislocation slip instead of {332}<113> twinning prevailed. These dislocations were first arranged into extended boundaries and then into laminated structures to coordinate deformation. Eventually, shear banding and fragmentation of laminates result in the formation of nanocrystalline with size of 34 ± 8 nm. The nanostructured Ti-12Mo alloy exhibited the high hardness of 4.9 GPa at subsurface. The surface hardness decreased to 4.4 GPa which was mainly caused by the inhibition of stress-induced martensitic transformation α″ and the occurrence of its reversal transformation due to adiabatic heating induced by the high strain rate. This work expands our knowledge on strengthening β titanium alloys by {332}<113> twinning induced grain refinement at different deformation conditions.