Synthesis and study of nanocrystalline Ni-Cu-Zn ferrites prepared by oxalate based precursor method

Nanocrystalline ferrites of compositions Ni_0.5+1.5xCu_0.3Zn_0.2Fe_2−xO₄ (0 ≤ x ≤ 0.5) have been synthesized by using oxalate based precursor method at very low temperature. The Ni-Cu-Zn ferrite powder particles were obtained at 450 °C and they exhibit a crystallite size of 16-24 nm. The lattice constants were found nearly equal in all these samples due to minute difference in the ionic radius between Ni²⁺ and Fe³⁺ ions. The thermal analysis has showed the ferrite phase formation at very low temperature 377 °C. The two main spectroscopic bands corresponding to lattice vibrations were observed in the wavelength range from 300 to 1000 cm⁻¹. The IR bands at 570 cm⁻¹ (v₁) and 390 cm⁻¹ (v₂) were assigned to tetrahedral (A) and octahedral [B] groups. The spectroscopic bands shift with the increase of doping concentration. The magnetization was found to decrease with increasing doping concentration. The dielectric constant (?′) and dielectric loss tangent (tan δ) decreased with increase of frequency. The dielectric constant and dielectric loss obtained for the nanocrystalline ferrite samples appeared to be lower than that of the ferrites prepared by other synthesis techniques.     

DC and analog/RF performance optimisation of source pocket dual work function TFET

We investigate a systematic study of source pocket tunnel field-effect transistor (SP TFET) with dual work function of single gate material by using uniform and Gaussian doping profile in the drain region for ultra-low power high frequency high speed applications. For this, a n⁺ doped region is created near the source/channel junction to decrease the depletion width results in improvement of ON-state current. However, the dual work function of the double gate is used for enhancement of the device performance in terms of DC and analog/RF parameters. Further, to improve the high frequency performance of the device, Gaussian doping profile is considered in the drain region with different characteristic lengths which decreases the gate to drain capacitance and leads to drastic improvement in analog/RF figures of merit. Furthermore, the optimisation is performed with different concentrations for uniform and Gaussian drain doping profile and for various sectional length of lower work function of the gate electrode. Finally, the effect of temperature variation on the device performance is demonstrated.     

DATA ACQUISITION SYSTEM FOR ARC-DRIVEN HF/DF CHEMICAL LASERS

The article focuses on the development of a data acquisition system (DAS) working in a noisy and hostile environment for an arc-operated hydrogen fluoride/deuterium fluoride (HF/DF) chemical laser. PC-based DAS has been configured using Advantech plug and play modules with fiber link connectivity. This article also focuses on implementation of an orifice-based precise gas flow control system. The plasma arc discharge in an arc heater/generator is essentially employed for inducing thermal dissociation of sulfur hexafluoride SF₆ for production of fluorine atoms, and DAS has been used for performance optimization of the composition of the lasing mixture by independently varying the flow rate, pressure, and temperature of its constituents. Since arc load is complex with high voltage transients and electromagnetic noise, an optical fiber link has been implemented for data transmission. This article also discusses digital output interface circuitry for various electro-pneumatic actuators/solenoid valves. The developed DAS has been used for monitoring and performance evaluation of parameters for 50 kW arc tunnel.     

Dynamic rheological,morphology and mechanical properties of compatibilized LLDPE/EMA blends

Blends of linear low density polyethylene (LLDPE) and ethylene-co-methyl acrylate (EMA) having 60/40 composition was studied with and without compatibilizing agent. The compatibilizing agent used was maleic anhydride grafted linear low density polyethylene (LLDPE-g-MA). The LLDPE backbones of the compatibilizer are compatible with LLDPE blend component, whereas the maleic anhydride is affinated with carbonyl groups of EMA. The effectiveness of the compatibilizing agent was evaluated using different techniques like mechanical, thermal, scanning electron microscopy and rheological studies. Best compatibilization effect was found in the blend at a loading of 3 wt% of compatibilizer since at this level of compatibilizer complex viscosity, tensile strength, modulus, elongation at break, impact strength was found to be higher. The increase in the melt viscosity, storage modulus and thermal stability of the compatibilized blends indicated enhanced interactions between the discrete LLDPE and EMA phases induced by the functional compatibilizer.     

Carboxymethyl guar: Its synthesis and macromolecular characterization

Guar gum was partially carboxymethylated by the reaction of the base polysaccharide with the sodium salt of monochloroacetic acid in presence of sodium hydroxide. The resulting products (carboxymethyl guar with different degrees of substitution) were characterized by a variety of material characterization techniques, such as intrinsic viscosity measurement, determination of molecular weight, elemental analysis, thermal analysis, ¹³C‐NMR spectra, and Fourier transform infrared analysis. Various grades of carboxymethyl guar gum, which were synthesized in the laboratory, were studied for their suitability as flocculants and viscosifiers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A Thermoplastic Polyurethane /Nanosilica Composite via Melt Mixing Process and its Properties

Silicon - This investigation reports the preparation and properties of thermoplastic polyurethane/silica nanocomposite prepared via melt mixing process. In this case, nanosilica at different...     

Thermal,fire, and mechanical properties of solvent‐free processed BN/boehmite‐filled prepregs

Within the scope of this research, platelet‐shaped hexagonal Boron Nitride (h‐BN) with a size of 2 and 12 μm, and oval‐shaped Boehmite (BT) with a size of 2 μm were incorporated in a glass fiber‐reinforced epoxy novolac matrix cured with a diamine‐based hardener. The effects of the platelet size (BN 2 and 12 μm) and filler nature (BT vs. BN) were correlated with the final thermal and fire‐related properties. The incorporation of the fillers shows that not only the thermal conductivity (σ) was increased from approximately 0.2 up to 1.04 W/mK (through‐plane) but also the flame retardancy was improved by using a hybrid combination. The time to ignition (t_ig) was increased by 48 s and the FIGRA value was decreased from 6.5 to 3.3 indicating a much lower fire hazard for the material. scanning electron microscopic micrographs of the laminate cross sections show that the fillers are distributed and oriented randomly in the fiber‐reinforced matrix, and also highlight the fiber wetting. Furthermore, the results show that the resulting 3D filler network and infiltration of the intratow regions is strongly dependent on lateral filler size and filler combination. With increasing the filler aspect ratio, the effect on thermal properties and filtration is more evident. Moreover, the hybrid combination of BN and Boehmite fillers has a strong effect on the network formation during processing, resulting in enhanced thermal and mechanical properties. A synergy was observed when using BN 12 μm in combination with Boehmite 2 μm as the larger platelets tend to assemble themselves in the intertow region (resin‐rich region) and the smaller particles infiltrate into the intratow regions. This leads to a formation of a thermal pathway throughout the glass fabric barrier. Considering the cost factor, the through‐plane (z‐direction) heat dissipation and the flame retardancy can be tailored by optimizing the size, aspect ratio/geometry, and nature of the fillers. POLYM. ENG. SCI., 59:1840–1852, 2019. © 2019 The Authors. Polymer Engineering & Science published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers.     

Room-Temperature Charpy Impact Property of 3D-Printed 15-5 Stainless Steel

In this study, the room-temperature Charpy impact property of 3D-printed 15-5 stainless steel was investigated by a combined experimental and finite element modeling approach. The experimentally measured impact energy is 10.85 ± 1.20 J/cm², which is comparable to the conventionally wrought and non-heat treated 15-5 stainless steel. In parallel to the impact test experiment, a finite element model using the Johnson–Cook material model with damage parameters was developed to simulate the impact test. The simulated impact energy is 10.46 J/cm², which is in good agreement with the experimental data. The fracture surface from the experimentally tested specimen suggests that the 3D-printed specimens undergo predominately brittle fracture.     

Structural tailoring of molybdenum disulfide by argon plasma for efficient electrocatalysis performance

This article describes the synthesis of molybdenum disulfide (MoS₂) nanowires using chemical vapor deposition (CVD) method. The MoS₂-nanowires converts into micro-flake structures with the help of argon (Ar) plasma for the better hydrogen evolution reaction (HER) activity. The MoS₂-nanowires treated by post-Ar plasma at different time of intervals (20 seconds, 40 seconds, 60 seconds, and 3 minutes). The plasma treatment significantly tailored the structure of pristine MoS₂-nanowires due to which additional active sites were produced at the surface of treated MoS₂. A notable HER activity were achieved by plasma-treated MoS₂. To boost the HER activity up to next level, visible light was used at the time of electrocatalysis which enhanced the electrocatalytic activity almost double, which is evident by the low overpotential (190 mV) at current density of 10 mAcm⁻².     

Fabrication of silicon nanohorns via soft lithography technique for photoelectrochemical application

Water splitting for H₂ production by absorbing sunlight is broadly used as a common technique to counter existing energy crisis and environmental problems, caused by extreme use of fossil fuels. We report a versatile and facile method to fabricate ordered Silicon nanohorns (SiNHs) by employing prefabricated metal nano-gap template on Si. The close-packed monolayer is used to develop the nanohole template, which enables the generation of SiNHs via metal-assisted controlled chemical etching. By varying monolayer parameters and etching sequences, SiNHs with desired dimensions were obtained. Growth along the crystalline plane of the base substrate ?100?, with a consistent bent at the tip of the SiNH, has been observed. The resulting SiNHs exhibited enhanced photoelectrochemical properties, with short-circuit photocurrent density more than four times higher than that of the planer Si along with enhanced trapping of photogenerated carriers. A photocurrent density of ~4.8 mA/cm² was observed at a potential of -1 V vs. RHE. Further, the electrochemical impedance study (EIS) was carried out to understand the photoelectrochemical activity and charge transfer kinetics of the SiNHs system. These nanostructures enhance light absorption and may be one of the low-cost alternatives for optical devices, sensors, and hydrogen evolution.