பொருள் அறிவியல் & பொறியியல் இதழ்

Manganese oxides (MnO₂) nanoparticles were synthesized using a co-precipitation technique. The as prepared nanopowder was used for further characterization. The size, structure and morphology of MnO₂ nanoparticles were characterized by X-ray diffraction (XRD) and SEM. The crystallite size of the synthesized MnO₂ nanoparticles was obtained from X-ray diffraction study using Debye-Scherer formula and it was found to be 22 nm. The surface morphology of prepared MnO₂ nanoparticles was analyzed by scanning electron microscope. The optical properties were analyzed using UV-studies. Dielectric studies were carried out for the pelletized sample of MnO₂ nanoparticles. The dielectric properties of MnO₂ nanoparticles were studied in the different frequency range of 50Hz-5MHz at different temperatures. The frequency dependence of the dielectric constant and dielectric loss is found to decrease with an increase in the frequency at different temperatures.

In last few years low power electronic devices have been increased rapidly. The devices are used in a large number to comfort our daily lives. With the increase in energy consumption of these portable electronic devices, the concept of harvesting alternative renewable energy in human surroundings arise a new interest among us. In this project I try to develop a piezoelectric generator. That can produce energy from vibration and pressure available on some other term (like people walking ). This project describes the use of piezoelectric materials in order to harvest energy from people walking vibration for generating and accumulating the energy. This concept is also applicable to some large vibration sources which can find from nature. This project also represents a footstep of piezoelectric energy harvesting model which is cost effective and easy to implement.

A membrane distillation process using solar energy has been studied. This system has been modelled to provide approximations of the flow of distillate, the thermal effectiveness and the quantities of heat exchanged by conduction and evaporation during the production process of water. Then, simulations have been carried out using MATLAB to highlight the transfers of mass and energy in a dynamic regime under the effect of variable solar radiation and to illustrate the temporal evolution of the parameters related to the operation of the membrane. So, to estimate the production of water, a polynomial approximation was used.A membrane distillation process using solar energy has been studied. This system has been modelled to provide approximations of the flow of distillate, the thermal effectiveness and the quantities of heat exchanged by conduction and evaporation during the production process of water. Then, simulations have been carried out using MATLAB to highlight the transfers of mass and energy in a dynamic regime under the effect of variable solar radiation and to illustrate the temporal evolution of the parameters related to the operation of the membrane. So, to estimate the production of water, a polynomial approximation was used.

Advances in material science have led to innovation of new materials having different properties. Functionally Graded Laminates (FGL) belong to this trend. In this work, an attempt has been made to fabricate Functionally Graded Carbon Nano Tube (CNT) reinforced Aluminium matrix laminates by an innovative powder metallurgy based cold compaction technique. The FGL composites have been prepared by incorporating CNT particles to aluminium metal matrix in different weight fractions, ranging from 0.1 to 0.5 wt%. The mechanical properties of these FGL composites have been studied in detail for assessing the effectiveness of the adopted fabrication technique. This method is an effective way to change the properties of the materials as required in different directions. The gradient layers here exhibited different microstructures and variation in hardness from one end to the other. Absence of Aluminium Carbide in the FGL composites is an important finding of this work highlighting the chemical stability of CNT in Al-matrix. An increase in the hardness by 129% was observed in the case of 0.5 wt.% of CNT in the formed laminates. Each layer demonstrated good adhesion after sintering process with no serious pores or microcracks.

In this research was study the dielectric properties of the epoxy composites as a function of a frequency, “weight fraction- particle size” of fillers. Composite plates were prepared by incorporating fiber glass and SiC Particles of 0.1 μm, 3 μm, 40 μm diameter sizes at 10, 20, 30 and 40 weight percent in epoxy matrix. The experiments were performed to measure the dielectric constant and electrical conductivity in range (10-2000) KHz.

The mathematical models of plant metabolic pathways are discussed. Kinetic modeling is the most detailed mathematical description of a metabolic network and constitutes an important branch in the growing fields of systems biology. This model is based on non-stationary diffusion equations containing a nonlinear term related to the Michaelis-Menten kinetics. An analytical expression of metabolic concentration was obtained for all values of parameters using new approach to Homotopy perturbation method. Our analytical results were compared with simulation results. Satisfactory agreement with simulation data is noted.

The paper presents the casting-deforming technology intended to produce cast aluminum composites and items from them (in-situ technology). In addition the investigation has been made of the effect of mechanical activation of a charge containing these carbon forms as well as of intensive plastic deformation on the possibility of their structure rearrangement and creation of new forms (glass carbon and diamond-like carbon particles) with the aim of their use in in-situ casting technologies.

The γ-phase polymorph of WO₃ has been established in the literature as a selective NO sensor. When processed at the nanoscale, this material shows high sensitivity to trace levels of NO gas. Thus, it is intended for use in breath monitors of NO in exhaled breath to diagnose asthma. Focusing on the economic and scalable synthesis of this material, this paper reports on the flame-spray processing of WO3 nanopowders of the monoclinic γ-phase. Structural and chemical characterization of as-sprayed and heat-treated nanopowders were carried out that revealed the conditions for tailored phase and particle size distribution suitable for the intended application of this material in breath-based diagnostics.

Fe-doped TiO₂ nanoparticles were synthesized by sol–gel method. The synthesized nanopowders were characterized by powder X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), Ultraviolet Visible (UV-Vis) and Dielectric studies. The crystallite size and phase were determined by X-ray diffraction (XRD) analysis. The morphology and particle size were studied using the scanning electron microscope (SEM) and transmission electron microscopy (TEM). There is a slight variation in numerical value of crystallite size measured by the two techniques: TEM and XRD peak broadening. The optical properties were obtained from UV-Vis absorption spectrum. The UV-Vis absorption spectrum demonstrated an absorption shift in Fe-doped TiO₂ nanoparticles to longer wavelengths, thus showing an enhancement of the absorption in the visible spectrum. The dielectric studies were carried out at different frequencies and at different temperatures for the prepared Fe-doped TiO₂ nanoparticles. The frequency dependence of the dielectric constant and dielectric loss is found to decrease with an increase in the frequency at different temperatures.