Engineering the Interlayer Spacing by Pre-Intercalation for High Performance Supercapacitor MXene Electrodes in Room Temperature Ionic Liquid

MXenes exhibit excellent capacitance at high scan rates in sulfuric acid aqueous electrolytes, but the narrow potential window of aqueous electrolytes limits the energy density. Organic electrolytes and room-temperature ionic liquids (RTILs) can provide higher potential windows, leading to higher energy density. The large cation size of RTIL hinders its intercalation in-between the layers of MXene limiting the specific capacitance in comparison to aqueous electrolytes. In this work, different chain lengths alkylammonium (AA) cations are intercalated into Ti₃C₂T_x, producing variation of MXene interlayer spacings (d-spacing). AA-cation-intercalated Ti₃C₂T_x (AA-Ti₃C₂), exhibits higher specific capacitances, and cycling stabilities than pristine Ti₃C₂T_x in 1 m 1-ethly-3-methylimidazolium bis-(trifluoromethylsulfonyl)-imide (EMIMTFSI) in acetonitrile and neat EMIMTFSI RTIL electrolytes. Pre-intercalated MXene with an interlayer spacing of ≈2.2 nm, can deliver a large specific capacitance of 257 F g⁻¹ (1428 mF cm⁻² and 492 F cm⁻³) in neat EMIMTFSI electrolyte leading to high energy density. Quasi elastic neutron scattering and electrochemical impedance spectroscopy are used to study the dynamics of confined RTIL in pre-intercalated MXene. Molecular dynamics simulations suggest significant differences in the structures of RTIL ions and AA cations inside the Ti₃C₂T_x interlayer, providing insights into the differences in the observed electrochemical behavior.     

Fabrication of a <Emphasis Type="Italic">p</Emphasis>–<Emphasis Type="Italic">n</Emphasis> Heterojunction Using Topological Insulator Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript>–Si and Its Annealing Response

A junction device has been fabricated by growing p-type Bi₂Te₃ topological insulator (TI) film on an n-type silicon (Si) substrate using a thermal evaporation technique. Annealing using different temperatures and durations was employed to improve the quality of the film, as confirmed by microstructural study using x-ray diffraction (XRD) analysis and atomic force microscopy (AFM). The p–n diode characteristics of the junction devices were studied, and the effect of annealing investigated. An improved diode characteristic with good rectification ratio (RR) was observed for devices annealed for longer duration. Reduction in the leakage or reverse saturation current (\( I_{\rm{R}} \)) was observed with increase in the annealing temperature. The forward-bias current (\( I_{\rm{F}} \)) dropped in devices annealed above 400°C. The best results were observed for the sample device annealed at 450°C for 3 h, showing figure of merit (FOM) of 0.621 with RR ≈ 504 and \( I_{\rm{R}} \) = 0.25 μA. In terms of ideality factor, the sample device annealed at 550°C for 2 h was found to be the best with \( n \) = 6.5, RR ≈ 52.4, \( I_{\rm{R}} \) = 0.61 μA, and FOM = 0.358. The majority-carrier density \( \left( {N_{\rm{A}} } \right) \) in the p-Bi₂Te₃ film of the heterojunction was found to be on the order of 10⁹/cm³ to 10¹¹/cm³, quite close to its intrinsic carrier concentration. These results are significant for fundamental understanding of device applications of TI materials as well as future applications in solar cells.     

E‐TDGO: An encrypted trust‐based dolphin glowworm optimization for secure routing in mobile ad hoc network

Mobile ad hoc networks (MANETs) are independent networks, where mobile nodes communicate with other nodes through wireless links by multihop transmission. Security is still an issue to be fixed in MANETs. Hence, a routing protocol named encrypted trust‐based dolphin glowworm optimization (DGO) (E‐TDGO) is designed using Advanced Encryption Standard‐128 (AES‐128) and trust‐based optimization model for secure routing in MANET. The proposed E‐TDGO protocol includes three phases, namely, k‐path discovery, optimal path selection, and communication. At first, k paths are discovered based on the distance and the trust level of the nodes. From the k paths discovered, the optimal path is selected using a novel algorithm, DGO, which is developed by combining glowworm swarm optimization (GSO) algorithm and dolphin echolocation algorithm (DEA). Once the optimal path is selected, communication begins in the network such that E‐TDGO protocol ensures security. The routing messages are encrypted using AES‐128 with shared code and key to offer security. The experimental results show that the proposed E‐TDGO could attain throughput of 0.11, delay of 0.01 second, packet drop of 0.44, and detection rate of 0.99, at the maximum number of rounds considered in the network of 75 nodes with attack consideration.     

Effects of SO2 and SO3 on the Na2SO4 induced corrosion of nickel

The effects of SO₂ and SO₃ in the environment on the hot corrosion behavior of Ni in the temperature range 750–950°C has been studied. Below the melting point of Na₂SO₄ (884°C), rapid corrosion takes place by formation of a Na₂SO₄-NiSO₄ melt, which can penetrate the porous oxide scale and give rise to sulfide information by coming in contact with the metal. The distribution of the sulfides depends on the SO₂ level in the ambient gas. Continued corrosion occurs by a sulfidation-oxidation mechanism. At temperatures above the melting point of Na₂SO₄, accelerated degradation occurs via dissolution of the surface scale, followed by reprecipitation of the oxide in a nonprotective form.Deceased     

The repassivation of nickel-copper alloys in sulphuric acid

The behaviour of freshly generated electrode surfaces of Ni, Ni-30Cu, Ni-50Cu and Ni-70Cu in 1.0 M H₂SO₄ has been investigated. At low potentials all metals grow a monolayer of film designated as MOH when M is Cu⁺ or Ni⁺. The kinetics of formation of this monolayer follows Tafel's equation. At higher potentials passivation of the metals occurs by film growth under high electric field, with two different sets of high field parameters for different film thicknesses. The rate of film growth for all metals is controlled largely by the nickel oxide component of the film.     

Processing and characterization of nanostructured Cu-carbon nanotube composites

Carbon nanotube (CNT) reinforced nanostructured Cu matrix composite with a grain size less than 25 nm has been successfully fabricated via a combination of ball milling and high-pressure torsion. CNTs were found to be homogeneously dispersed into the metal matrix, leading to grain refinement with a narrow grain size distribution and significant increase in hardness.     

Influence of glass fiber content on the morphology and mechanical properties in injection molded polypropylene composites

Propropylene was reinforced with various concentrations of glass fiber (0, 10, 20, 28, and 35 percent by weight) and standard test samples were prepared by injection molding under identical conditions. The influence of fiber concentration on the morphology and mechanical properties was investigated using polarizing microscope, scanning electron microscope, Instron universal testing machine, etc. Tensile strength, tensile modulus, and flexural strength were found to increase with glass fiber content, while impact strength was reduced. These observed changes in mechanical properties were explained in terms of alterations in skin-core morphology, spherulite size, transcrystallinity, etc. The efficiency of reinforcement factor (K) was calculated for all the composites. It was found that K decreases with the increase of fiber concentration. This study attempts to correlate fiber concentration and polymer morphology with mechanical properties and the overall efficiency of reinforcement. This would help in optimizing the fiber content to prepare molded composites with desired mechanical properties.     

Printed, flexible electrochromic displays using interdigitated electrodes

We describe herein some of our initial studies in pursuit of a simple, economical method of mass producing electrochromic displays. The approach we have taken is to print the display on polymer film utilizing commercially available conductive inks in an interdigitated electrode structure with a conductive metal oxide powder, dispersed in a polymer binder, as the electrode surface. A range of electrochromic materials suitable for use with an aqueous gel electrolyte have been explored and examples presented.