Interplay Between Superconductivity and Antiferromagnetism in HoNi2B2C

A microscopic theory of interplay between superconductivity and antiferromagnetism in rare-earth nickel boride, HoNi₂B₂C is developed from first principles. Self-consistent equations for the superconducting order parameter Δ and magnetic order parameter Γ are derived using a Green’s function technique and an equation of motion method. The theory is applied to explain the experimental results in the antiferromagnetic superconductor HoNi₂B₂C. The present model explains the true coexistence of superconductivity and antiferromagnetism in this system. The behavior of the superconducting order parameter (Δ), the magnetic order parameter (Γ), the specific heat, the density of states, the free energy and critical field (H _c) is also studied for the system HoNi₂B₂C. Distinct features of the coexistence region are discussed. There is the convincing evidence that the theory is fully compatible with the key experiments.     

Application of fly ash as a catalyst for synthesis of carbon nanotube ribbons

The larger diameter-based carbon nanotube (CNT) ropes and ribbons are currently synthesized by catalytic decomposition of hydrocarbons with transition metal-based catalysts e.g., Co, Ni, Fe and Mo at 1100-1200 °C, using chemical vapour deposition (CVD) and electric arc methods. We produced CNT ribbons by fly ash (FA) catalyzed pyrolysis of a composite film of poly (vinyl alcohol) (PVA) with FA at 500 °C for 10 min under a nitrogen flow of 2 L/min. Different geometrical structures, e.g.; knotted and twisted, U- and spiral-shaped CNT ribbons were observed in the images of scanning and transmission electron microscopy. The widths of the CNT ribbons measured varied in the ranges 18-80 nm. X-ray photoelectron spectroscopy analysis showed five types of carbon binding peaks, C-C/C-H (∼77%), C-O-H (∼9%), -C-O-C (∼5%), CO (∼5%) and -O-CO (∼3%). The ratio of intensities of G and D bands, IG/ID was 1.61 analysed by Raman Spectroscopy. CNT ribbons grown on the surface of FA have potential for the fabrication of high-strength composite materials with polymer and metal.     

Exergy analysis of small DI diesel engine fueled with waste cooking oil biodiesel

ABSTRACT

This study investigates the merits of exergy analysis over energy analysis for small direct injection (DI) diesel engine using the blend of waste cooking oil biodiesel and petroleum diesel. Taguchi’s “L’ 16” orthogonal array has been used for the design of experiment. The engine tested at different engine speeds, load percentages, and blend ratios, using the waste cooking oil biodiesel. Basic performance parameters and fuel input exergy, exergetic efficiency (second law efficiency), exergy associated with heat transfer, exergy associated with the exhaust gas and destruction of exergy are calculated for each blend of waste cooking oil biodiesel and diesel. Results show that the optimum operating conditions for minimum brake-specific fuel consumption (BSFC) and exergy destruction are achieved when engine speed at 1900 rev/min, load percentage is 75%, and the engine is fueled with B40.     

Kinetics and mechanism of corrosion of laboratory hot briquetted iron

While considerable work has been reported in the literature on the corrosion behavior and products of direct reduced iron and sponge iron, very little has been published on hot briquetted iron (HBI). The present article reports the kinetics and mechanism of HBI corrosion. As corrosion is an electrochemical process, measurements using electrochemical techniques have been made and these are compared to data gained by measuring mass changes in the briquettes over time. Similar trends were seen in data from both techniques, and the corrosion extent predicted by electrochemical measurements in saline solution was very close to the mass gain result obtained. Kinetic analysis of the data from mass gain over time trials was conducted. The activation energy for corrosion at temperatures between 25 °C and 80 °C has been calculated. The values of activation energy obtained indicate that corrosion was predominantly controlled by diffusion of oxygen in the liquid state. The internal structure of the briquettes was observed by microscopy both before and after corrosion in distilled water.     

Biofilter in water and wastewater treatment

Biofilter is one of the most important separation processes that can be employed to remove organic pollutants from air, water, and wastewater. Even though, it has been used over a century, it is still difficult to explain theoretically all the biological processes occurring in a biofilter. In this paper, the fundamental of biological processes involved in the biofilter is critically reviewed together with the mathematical modeling approach. The important operating and design parameters are discussed in detail with the typical values used for different applications. The most important parameter which governs this process is the biomass attached to the medium. The relative merits of different methods adopted in the measurement of the biomass are discussed. The laboratory-and full-scale applications of the biofilter in water and wastewater treatment are also presented. Their performances in terms of specific pollutant removal are highlighted.