Experimental Result on Heat Transfer during Quenching of Hot Steel Plate by Spray Impingement

The present article discusses the experimental results on cooling characteristics of a stationary hot steel plate by spray impingement. The experimental setup consisted of an electrically heated flat stationary steel plate of dimension 120 mm × 120 mm × 4 mm, spray setup, water supply, and air supply unit. The effects of various controlling parameters such as air-water pressures, water flow rate, nozzle tip to target distance and impingement density were determined and analyzed. The cooling rates were computed from the time-dependent temperature history and used to analyze the parametric effects. The results obtained in the study confirmed the higher efficiency of the spray cooling system and the cooling strategy was found advantageous over the conventional cooling methods available in the open literature.     

Propagation delay and power dissipation for different aspect ratio of single-walled carbon nanotube bundled TSV

Through-silicon vias (TSVs) have provided an attractive solution for three-dimensional (3D) integrated devices and circuit technologies with reduced parasitic losses and power dissipation, higher input-output (I/O) density and improved system performance. This paper investigates the propagation delay and average power dissipation of single-walled carbon nanotube bundled TSVs having different via radius and height. Depending on the physical configuration, a comprehensive and accurate analytical model of CNT bundled TSV is employed to represent the via (vertical interconnect access) line of a driver-TSV-load (DTL) system. The via radius and height are used to estimate the bundle aspect ratio (AR) and the cross-sectional area. For a fixed via height, the delay and the power dissipation are reduced up to 96.2% using a SWCNT bundled TSV with AR = 300 : 1 in comparison to AR = 6 : 1.     

Phase Evolution,Magnetic, Optical,and Dielectric Properties of Zr‐Substituted Bi0.9Gd0.1FeO3 Multiferroics

Polycrystalline BiFeO₃ (BFO) and Bi_0.90Gd_0.10Fe_1?xZr_xO₃ (x = 0.0–0.10; BGFZ_x) ceramics were synthesized by solid‐state reaction method. Rietveld analysis of X‐ray diffraction patterns showed that BFO and BGFZ_x = 0.0 samples are stabilized in rhombohedral structure (space group R3c), whereas a small fraction of orthorhombic phase (space group Pn2₁a) is observed for BGFZ_{x = 0.03–0.10} samples. Suppression and disappearance of some Raman modes indicated a structural phase transition with addition of Zr dopant at Fe site. Magnetic measurements exhibited weak ferromagnetic behavior of BGFZ_x samples with increasing Zr⁺⁴ concentrations. The insertion of Gd⁺³ ions at Bi⁺³ sites and nonmagnetic Zr⁺⁴ ions at Fe⁺³ sites in Fe–O–Fe network suppressed the spin cycloid structure of BFO which in turn enhanced the magnetization of these ceramics. Electron spin resonance spectra revealed the breaking of spin cycloid of BFO due to the development of free spins with addition of Zr⁺⁴ dopants at Fe sites. UV–Visible diffuse reflectance spectra showed one d–d crystal field transition and two charge‐transfer (C–T) transitions along with a sharp absorption of light in visible region for all samples. Almost frequency‐independent dielectric constant and dielectric loss along with very low values of dielectric loss indicated greatly improved dielectric properties for BGFZ_{x = 0.03–0.10} samples.     

Electrical behavior of dual‐morphology polyaniline

An attempt was taken to synthesize two types of polyaniline (PANI) with and without solvent followed by drying in air and vacuum oven conditions resulting different morphologies. The PANIs were prepared by chemical oxidative polymerization and studied with respect to their morphological features. Scanning electron microscopy, thermogravimetric analysis, X‐ray diffractometry, Fourier transform infrared spectroscopy, and ultraviolet–visible spectroscopy techniques were used for the characterization studies. The PANI synthesized with a solvent had a mixed morphology (fibrillar and granular), whereas PANI synthesized without a solvent had only a granular morphology. The direct‐current electrical conductivities of the samples were evaluated with an electrometer. We observed that the PANIs with mixed morphology (with solvent) were more electrically conducting than those with a single morphology (without solvent). On drying in vacuo, the conductivity of PANI decreased from 3.3 × 10^?2 to 0.3 × 10^?2 S/cm with solvent treatment, whereas it decreased from 0.1 × 10^?2 to 0.3 × 10^?3 S/cm without solvent treatment. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44091.     

Water generation from atmospheric air by using different composite desiccant materials

In this communication, new composite desiccant materials having 37% concentration of CaCl₂ have been compared for water production from atmospheric air. The vermiculite–saw wood, jute and burnt-clay have been used as host materials and CaCl₂ as a hygroscopic salt. All the desiccant materials have been tested with the solar glass desiccant box type system (SGDBS) with a collector area of 0.36?m². Design parameters for water production are: height of the glass from the desiccant bed to be 0.22?m, an inclination angle of 30°, the effective thickness of the glass as 3?mm and the number of glazing is single. It has been found that on the experimental day, the maximum amount of fresh water generated by the vermiculite–saw wood/CaCl₂ is 130?ml/kg/day.     

Development of spark plasma sintered conductive SiC–TiB2 composites for electrical discharge machining applications

Highly dense electrically conductive silicon carbide (SiC)–(0, 10, 20, and 30 vol%) titanium boride (TiB₂) composites with 10 vol% of Y₂O₃–AlN additives were fabricated at a relatively low temperature of 1800°C by spark plasma sintering in nitrogen atmosphere. Phase analysis of sintered composites reveals suppressed β→α phase transformation due to low sintering temperature, nitride additives, and nitrogen sintering atmosphere. With increase in TiB₂ content, hardness increased from 20.6 to 23.7 GPa and fracture toughness increased from 3.6 to 5.5 MPa m^1/2. The electrical conductivity increased to a remarkable 2.72 × 10³ (Ω cm)^–1 for SiC–30 vol% TiB₂ composites due to large amount of conductive reinforcement, additive composition, and sintering in nitrogen atmosphere. The successful electrical discharge machining illustrates potential of the sintered SiC–TiB₂ composites toward extending the application regime of conventional SiC-based ceramics.     

Applicability of Field Plate in Double Channel GaN HEMT for Radio-Frequency and Power-Electronic Applications

Silicon - In the present communication, for the first time, applicability of Field Plate (FP) for Double Channel (DC) AlGaN/GaNHEMT is demonstrated. Impact of design space parameters such as field...     

Design of XNBR nanocomposites for underwater acoustic sensor applications: Effect of MWNT on dynamic mechanical properties and morphology

In this work, application of rubber‐MWNT nanocomposite for underwater acoustic sensors is explored. The nanocomposite is developed by incorporating multiwalled carbon nanotubes (MWNT) into carboxylated nitrile rubber by mechanical mixing. The addition of MWNT up to 10 phr is found to result in about 330% increase in tensile strength, 140% increase in modulus, and 160% increase in tear strength. Transmission electron microscopy and scanning electron microscopy analyses indicate uniform dispersion of nanotubes in the rubber matrix. Dynamic mechanical analysis shows that damping at ambient temperature gradually increases with increasing filler content. This is attributed to the augmented frictional energy loss at the interface. The damping peak position shifts upward with increase in MWNT concentration, which may be gainfully used to tune to the operational frequency range of underwater acoustic sensors. Payne effect is observed at higher filler concentration due to the breakage of aggregates formed by filler–filler interaction. The nanocomposite may find application for damping structural vibrations and thus to improve the performance of underwater acoustic sensors. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40752.     

Erosion behavior of SiC–WC composites

Dense silicon carbide (SiC) ceramics were prepared with 0, 10, 30 or 50 wt% WC particles by hot pressing powder mixtures of SiC, WC and oxide additives at 1800 °C for 1 h under a pressure of 40 MPa in an Ar atmosphere. Effects of alumina or SiC erodent particles and the WC content on the erosion performance of sintered SiC–WC composites were assessed. Microstructures of the sintered composites consisted of WC particles distributed in the equi-axed grain structure of SiC. Fracture surfaces showed a mixed mode of fracture, with a large extent of transgranular fracture observed in SiC ceramics prepared with 30 wt% WC. Crack bridging by WC enhanced toughening of the SiC ceramics. A maximum fracture toughness of 6.7 MPa*m^1/2 was observed for the SiC ceramics with 50 wt% WC, whereas a high hardness of 26 GPa was obtained for the SiC ceramics with 30 wt% WC. When eroded at normal incidence, two orders of magnitude less erosion occurred when SiC–WC composites were eroded by alumina particles than that eroded by SiC particles. The erosion rate of the composites increased with increasing angle of SiC particle impingement from 30° to 90°, and decreased with WC reinforcement up to 30 wt%. A minimum erosion wear rate of 6.6 mm³/kg was obtained for SiC–30 wt% WC composites. Effects of mechanical properties and microstructure on erosion of the sintered SiC–WC composites are discussed, and the dominant wear mechanisms are also elucidated.