“SmFeO<Subscript>3</Subscript>-Polyanaline Composite: Synthesis and Its Various Characterizations”

Polyaniline-SmFeO₃ composite are prepared by chemical oxidative polymerization method. Structural, vibrational, morphological, thermal, optical, magnetic and dielectric properties of the samples are explored by X-ray diffraction, Fourier Transform Infrared (FTIR), Scanning Electron Microscope (SEM), Thermo Gravimetric Analysis, UV–Vis, Vibrating Sample Magnetometer, and dielectric measurements. Crystalline nature of the composite has been obtained due to the presence of SmFeO₃ particles in polyaniline and retains orthorhombic structure with Pbnm space group. A noticeable impact on various parameters (grain size, stress and dislocation density) can be observed. FTIR analysis confirms the formation of polyaniline. The obtained vibrational bands of polyaniline structure changes due to the presence of SmFeO₃ particles. Surface/particle morphology of the composite has been observed from SEM micrographs. The thermal stability of polyaniline is considerably enhanced in composite format. From the evaluation of optical absorption data, a reduction in optical band gap (E_g) is observed. The real and imaginary part of dielectric constant was found to follow the universal dielectric response. From the ac conductivity investigations, charge carriers follow the correlated barrier hopping transport mechanism.     

Improving hydrocarbons production via catalytic co-pyrolysis of torrefied-biomass with plastics and dual catalytic pyrolysis

To increase the low yield and selectivity of aromatic hydrocarbons during the biomass pyrolysis process, we torrefied the biomass and then co-pyrolyzing with plastics such as high-density polyethylene (HDPE), polystyrene (PS), ethylene-vinyl acetate (EVA) and polypropylene (PP) and also single and dual catalyst layouts were investigated by Py-GC/MS. The results showed that non-catalytic fast pyrolysis (CFP) of raw bagasse (RBG) generated no aromatics. After torrefaction non-CFP of torrefied bagasse (TBG) generated low aromatic yield. Indicating that torrefaction would enhance the proportion of aromatics during the pyrolysis process. The CFP of TBG_200℃ and TBG_240℃ over ZSM-5 produced the total aromatic yield of 1.96 and 1.88 times higher, respectively, compared to non-CFP of TBG. Furthermore, the addition of plastic could increase H/Ceff ratio of the mixture, consequently, increase the yield of aromatic compounds. Among the various torrefied-bagasse/plastic mixtures, the CFP of TBG/EVA (7:3 ratio) mixture generated the highest the total aromatic yield of 7.7 times more than the CFP of TBG alone. The dual catalyst layout could enhance the yield of aromatics hydrocarbons. The dual-catalytic co-pyrolysis of TBG_200℃/plastic (1:1) ratio over USY (ultra-stable Y zeolite)/ZSM-5, improved the total aromatics yield by 4.33 times more than the catalytic pyrolysis of TBG_200oC alone over ZSM-5 catalyst. The above results showed that the yield and selectivities of light aromatic hydrocarbons can be improved via catalytic co-pyrolysis and dual catalytic co-pyrolysis of torrefied-biomass with plastics.     

Friction and wear characteristics of vegetable oils using nanoparticles for sustainable lubrication

The non biodegradability associated with the mineral oils, ever increasing global demand for lubricants and limited crude oil resources have led to a paradigm shift of focus from non-renewable to renewable. The problems of friction and wear being innate to engineering applications, further poses environmental hazards by way of more fuel consumption and wear debris. The present paper is aimed to highlight the research studies carried out to exploit the addition of nanoparticle additives in vegetable oils. The encouraging results obtained therein suggest that vegetable oils have a tremendous potential to be used as lubricating oils. Moreover, the issues which are limiting their use have also been presented in this paper.     

Mechanical and Tribological Properties of a Nano-Si3N4/Nano-BN Composite

The mechanical and tribological properties of a nano-Si₃N₄/nano-BN composite were studied. The composite was prepared via high-energy mechanical milling and subsequent spark plasma sintering. Y₂O₃ and Al₂O₃ were used as sintering additives. After sintering, the average crystalline size of Si₃N₄ and BN was 50 nm. Hardness (Vicker and Knoop) was evaluated under a high load of 0.05–2.0 kg for the nano/nano- and the micro/micro-Si₃N₄/BN composite with the same composition. The indentation fracture toughness values of both composites were also evaluated. Tribological studies were conducted to study the friction and wear behavior of both composites. A friction coefficient of 0.4–0.7 was obtained for the nano-S₃N₄/nano-BN composite under a normal load of 20–22 N, whereas, a friction coefficient of 0.37 was obtained for the micro-Si₃N₄/micro-BN composite. Specific wear coefficients of 0.418 × 10⁻⁴ and 0.625 × 10⁻⁴ mm³/N/m were obtained for nano-sized and micro-sized Si₃N₄/BN composites, respectively. Higher hardness, higher fracture toughness, and lower wear were observed in the nano-sized composite, as compared with the micro-sized composite.     

Simulation for the prediction of surface roughness in magnetic abrasive flow finishing (MAFF)

The final machining (or finishing) of precision parts with high level of surface finish and close tolerance is making the application of magnetic abrasive finishing technology increasingly important. Magnetic abrasive flow finishing (MAFF) is a new abrasive finishing process combining the features of abrasive flow finishing (AFF) and magnetic abrasive finishing (MAF). MAFF provides a high level of surface finish and close tolerances for wide range of industrial application. This paper focuses on the modeling and simulation for the prediction of surface roughness on the workpiece surface finished by MAFF process. A finite element model is developed to find the magnetic potential distribution in the magnetic abrasive brush formed during finishing action and then it is used to evaluate machining pressure, surface finish and material removal. The simulation results are compared with the experimental results available in the literature. The simulated workpiece surface roughness shows features similar in nature to the experimental results.     

TEM study of RTD structure fabricated with epi-Si/γ-Al2O3 heterostructure

Fabrication of γ-Al₂O₃/epi-Si/γ-Al₂O₃/Si-sub resonant tunneling diode structure has been performed and interfacial and crystalline quality of the fabricated RTD structure were characterized by high resolution transmission electron microscopy. Multiple layer structure formation with atomically flat interfaces was confirmed. The γ-Al₂O₃ layer on Si-sub was observed highly crystalline and oriented along the orientation of the Si substrate. But the epi-Si layer was not smoothly crystalline over the whole specimen and also crystallinity varies from place to place. The epitaxial Si layer was observed to be strained due to the difference in thermal expansion coefficient and the lattice mismatch between γ-Al₂O₃ and silicon.     

Silver nanoparticles: Large scale solvothermal synthesis and optical properties

Silver nanoparticles have been successfully synthesized by a simple and modified solvothermal method at large scale using ethanol as the refluxing solvent and NaBH₄ as reducing agent. The nanopowder was investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-visible and BET surface area studies. XRD studies reveal the monophasic nature of these highly crystalline silver nanoparticles. Transmission electron microscopic studies show the monodisperse and highly uniform nanoparticles of silver of the particle size of 5 nm, however, the size is found to be 7 nm using dynamic light scattering which is in good agreement with the TEM and X-ray line broadening studies. The surface area was found to be 34.5 m²/g. UV-visible studies show the absorption band at ∼425 nm due to surface plasmon resonance. The percentage yield of silver nanoparticles was found to be as high as 98.5%.     

Maintainability design and evaluation of mechanical systems based on tribology

Maintainability of mechanical systems based on tribology is suggested and evaluated in this paper. Tribo-features of mechanical systems, which characterise maintainability are identified and are modelled in terms of tribo-maintainability digraph. The nodes in the digraph represent the tribo-features and edges represent the degree of influence among the features. A matrix, one to one representation of the digraph, is defined to develop system maintainability expression (SPF-t) based on the tribology. It is also useful in comparing the various design alternatives from tribo-maintainability point of view. Maintainability is evaluated from the tribo-maintainability index, obtained from SPF-t (i.e. permanent of the matrix) by substituting the numerical values of the features and their interdependence. A higher value of the index implies better maintainability of the systems. The proposed methodology also guides designers in enhancing the maintainability of a system by appropriately incorporating tribo-features. An example to illustrate the methodology is also presented.     

Geometrical Modeling of Scattering Environment for Highways in Umbrella Cell Based MIMO Communication Systems

In this paper, we develop a three-dimensional (3D) eccentricity-based cylindrical geometrical channel model for nonisotropic multiple-input-multiple-output (MIMO) communication systems under umbrella macrocellular environment. We use elliptic cylindrical geometry to model the scattering phenomenon in streets, canyons and highways. The scattering objects like, high-rise building, trees and vegetation that lie along the roadside premises are modeled by the height of an elliptical cylinder. The proposed channel model targets fast moving vehicles on the highways in an umbrella-cell of cellular communication networks. We assume that both ends of the communication link are equipped with multiple antenna arrays, where, mobile-station antenna height is lower than base-station antenna. Utilizing the proposed MIMO communication channel model, we obtain closed-form expressions for the space–time correlation function among the MIMO antenna elements. The obtained theoretical expressions are plotted and analyzed for different values of channel parameters. Finally, we compare the proposed model with the existing models in the literature and prove that our model can be deduced to the existing two-dimensional and 3D channel models.     

Parametric study of a twisted aerosol-type singlet oxygen generator

A twisted aerosol singlet oxygen generator (TA-SOG), which is a new high-pressure SOG for the supersonic chemical oxygen-iodine laser (COIL), was developed. Its operational characteristics were compared to those of a conventional liquid-jet-type singlet oxygen generator. It was shown that TA-SOG is operated at an internal gas velocity of 85 m/s, which is three times higher than that of the jet-type SOG. Cl₂ utilization of 70% and singlet oxygen O₂ (¹Δ) yield of 85% were obtained under this condition. The results of our two-dimensional model calculation suggested that there must be some enhancement of a specific surface area in the reaction zone. The mechanism of this effect is discussed