பொருள் அறிவியல் & பொறியியல் இதழ்

A new theory for 180° domain wall in ferroelectric perovskite material is presented in this work. The effect of flexoelectric coupling on the domain structure is analyzed. We show that the 180° domain wall has a mixed character of Ising and Bloch type wall and that the polarization perpendicular to the domain wall is not zero though it is very small compared to the spontaneous polarization in the case of tetragonal Barium Titanate. Finally, we present the effect of the new finding on the domain wall interaction with defects in the material.

Jute fibres (Corchorus olitorious L.), an environmentally and ecologically friendly product, were chemically modified and treated as surface treatment which was carried out by mercerizing jute fabrics with aqueous solutions of NaOH (5,10 and 20%) at different soaking times (30, 60 and 90 minutes) and temperatures (0, 25 and 50°C). These mercerized jute fabric reinforced polypropylene composites were fabricated by composition molding technique and equated with virgin jute fabric reinforced polypropylene composites, fabricated by same technique. The above composite samples ware compared by evaluating the mechanical parameters such as tensile strength, tensile modulus, bending strength, bending modulus. The effect of mercerization on weight and dimension of jute fabrics was studied. Mechanical properties of mercerized jute-PP composites ware measured and found highest at 20% NaOH at 0°C for 60 min soaking time. Alkali treatment helped in the development of hydrophobicity and reduction in volume fraction of the porosity. This may be due to the better fibre matrix interface adhesion caused due to the fibre surface treatment by alkali. The optimized formulation was irradiated by γ radiation at different dosage (100, 150, 200, 250 & 500 Krad). Among them 250 Krad showed highest mechanical properties

A single phase of metallic glassy Zr90Ni6Pd4 powders was synthesized by mechanical alloying approach of the elemental powders, using a low-energy ball mill. The solid-solution hcp-ZrNiPd phase obtained after 25 h of the milling time transformed into a single amorphous phase upon ball milling for 100 h to 150 h. This synthesized amorphous alloy transformed into a metallic-glass at a glass transition temperature of 552.8°C. A small volume fraction of this glassy phase transformed into a mixture of two metastable phases of i-phase + big-cube upon annealing at 649.1°C. The supercooled liquid region of the metallic glassy Zr90Ni6Pd4 alloy powders was 69.7°C. A complete crystallization was achieved at a temperature ranged from 649.1°C to 682.2°C through a sharp exothermic reaction with an enthalpy change of crystallization of -76.3 J/g. After this temperature, the formed metallic glassy phase was transformed to polycrystalline mixture of tetragonal Zr2Ni and Zr2Pd phases. The powders obtained after 150 h of milling were subsequently consolidated at 600°C, using spark plasma sintering technique. The sizes of the obtained bulk metallic glassy buttons ranged were 15 mm and 50 mm in diameter with different thicknesses in the range between 0.25 mm to 20 mm. This consolidation step led to the formation of full-dense buttons with relative densities laid in the range between 99.23% to 99.76% without precipitations of any medium- or long-range ordered phase (s). Nanoindentation approach was employed to identify the nanohardness and Young’s modulus that were in the range between 7.74 to 9.32 GPa, and 135.26 to 151.15 GPa, respectively.

Automatic guided vehicle systems are now well known and recognized in automated material handling systems, FMS and also in container handling applications. It improves response time for material movement. It is an efficient, dependable and versatile material handling solution. AGVs consist of one or more computer-controlled wheel based load carriers that run on the plant floor without the need for a driver. These are designed to perform their operations without direct human guidance and are used in a wide variety of industrial applications. This paper presents a review on design and control of automated guided vehicle systems. The paper present a methodology to unify various lines of research related to AGVs and to suggest directions for future work for most key related issue i.e., including vehicle scheduling. Various types of scheduling problems are solved in different job shop environments, vehicle routing, guide-path design, vehicle dispatching. The prior objective of this paper is to extend previous research by examining the effects of scheduling rules and routing flexibility on the performance of a constrained and utilization of AGVs and machines.

It is widely known that two-way memory effect (TWME) is not an inherent property of shape memory alloy. The development of TWME requires thermomechanical training. Experimental study showed that undergoing partial reverse transformation in the course of training leads to the emergence of temporal two-step transformation, which was traditionally observed in the calorimetry measurement of an arrested stress-free heating cycle. The present work introduces a macromechanical approach to explain the mechanism of two-step transformation and its associated effects on stress-assisted two-way memory effect (SATWME) and TWME. The appearance of two-step transformation was observed to be a one-time only phenomenon and it clearly disappeared in the next full transformation. The disappearance of two-step transformation highlighted the occurrence of microstructural rearrangement driven by the internal stress field in the successive training cycles. A strain comparison demonstrated that the dominance of retransforming stress-assisted martensite (SAM) during cooling promoted the formation of internal back stress. This makes the accommodation process of deformation-induced martensite generated via pre-straining and SAM difficult, owing to which immobilizes the dislocations movement in the forward transformation direction, and causes detrimental effect on the TWME.

Cu2ZnSnS4 (CZTS) thin films have been electrochemically deposited from aqueous electrolyte containing CuCl2, ZnCl2, SnCl4 and Na2S2O3 onto fluorine doped tin oxide (FTO) coated glass substrates. A conventional three-electrode geometry consisting working, counter and reference electrodes was used to perform the electrochemical experiments. The films were deposited at - 1.1 V with respect to Ag/AgCl reference, which was optimized by cyclic voltammetry. CZTS layers were annealed in tubular furnace at 400°C for 15 minutes in vacuum. As-deposited and annealed CZTS films were characterized using range of characterization techniques to study the structural, optical, morphological, and compositional and optoelectronic properties. Annealed sample revealed (112), (220) and (312) planes corresponds to tetragonal kesterite CZTS structure and secondary peaks of CuZn alloy. The optical study shows that the band gap of the as-deposited CZTS film was found to be 1.68 eV. Upon annealing the optical band gap ~ 1.49 eV corresponds to CZTS were estimated from UV-Visible Spectroscopy and photoluminescence. Densely packed, void free and relatively uniform thin films were deposited by electrodeposition technique. The grain size has been increased upon the heat treatment. Copper and zinc rich off-stoichiometric films were deposited at -1.1 V. Current density-Voltage (J-V) measurements showed Schottkey behavior. The flat band potential and carrier concentration estimated by C-V measurement for annealed CZTS sample was 0.30 V and ~ 2.4 x 1016 cm-3 respectively.

The present work is an effort to study the effect of titanium and manganese powder addition in agglomerated flux, on the mechanical properties, of MS 1025 steel welds made by submerged arc welding. The effect of titanium and manganese powder addition on the agglomerated fluxes by varying the welding parameters like welding voltage and welding speed has been evaluated. Taguchi technique has been used for the design of experiments. The effects of flux, voltage and travel speed have been evaluated on the tensile strength and on the microstructure refining. The effect of all the input parameters on the output responses have been analyzed using the analysis of variance (ANOVA).

Mirtazapine is an antidepressant that was introduced in 1996 for the treatment of moderate and severe depression. Mirtazapine is the only tetracyclic antidepressant that is approved by the Food and Drug Administration to treat depression. Mirtazapine is devoid of most side effects but has antihistamine side effects of drowsiness and weight gain. Its bioavailability is only fifty percent. The low bioavailability and side effects can be improved by altering the pharmokinetic profile of the drug by controlling the release of the drug. The slow release of the drug will reduce the harmful affect it has on the cells decreasing the side effects, as well as the loading of the drug in the nanocarrier will allow for a longer residence time in the body before it is removed by the gastrointestinal tract. In this research paper the pharmokinetic profile of Mirtazapine will be altered by surrounding the drug with a biodegradable polymer called poly(propylene glycol) bis(2-aminopropylether) (PPG-NH2, MW _ 2000) chains. This profile will be done at different polymer concentrations, drug concentrations and solubilizer concentration to see how this will affect the release of the drug. In this research project it was found that using a lower concentration of poly(propylene glycol) bis (2-aminopropylether) (PPG-NH2, MW_2000) chains of 0.5 g/mL led to a slower release in comparison to the other polymer concentrations with an encapsulation of 10 mg of Mirtazapine. When the drug weight was increased but the polymer concentration stayed the same (0.95 g/mL) the release rate increased with drug concentration. Also when the stabilizer concentration was increased, but the polymer concentration and drug concentration remained the same (0.95 g/mL and 10 mg respectively) the release rate increased. Therefore in order to allow for a slower release rate one should use the lower polymer concentration of 0.95 g/mL, with the lower concentration of stabilizer. This will allow for a slower release of the drug Mirtazapine which will lower the side effects and increase the bioavailability percentage.

Review on Synthesis, Characterizations, and Electrochemical Properties of Cathode Materials for Lithium Ion Batteries

Natural fibres are now widely used for reinforcements of materials as they are a reliable resource and the cost is also less. One of the significant reasons of using natural fibres as reinforcements instead of polymers or other plastics is that they are degradable and don’t cause any harm to the environment. This article is particularly centered on polymer matrix composites made of Sisal fibre which was accessible locally and finding the composite’s mechanical property (tensile strength). A number of test samples of sisal fibre composite are fabricated by ASTM standards and made to undergo tensile tests in order to obtain the desired properties. In the later part of the work a comparison between the mechanical properties of a non-treated pure Sisal fibre composite and a NaOH treated Sisal fibre composite is carried out to check for any enhancements in the properties.

CaTiO3-LaAlO3 (CTLA) ceramics with Al2O3 nanoparticles were prepared by conventional two-step solid-state reaction, and the sintering behavior and the microwave dielectric proprieties were investigated. The results show that the doping of Al2O3 nanoparticles can promote the growth of uniform grain, increase the density and Q× f value, while it has no obvious influence on the dielectric constant (~45). CTLA ceramics with 0.05 wt% Al2O3 nanoparticles doping, sintered at 1420°C for 4h exhibited the optimal microwave dielectric properties, and CTLA ceramics with 0.2 wt% Al2O3 nanoparticles doping sintered at 1380°C for 4h exhibited the optimal microwave dielectric properties, respectively. A proper increase of Al2O3 nanoparticles content can reduce the sintering temperature.

Flixweed (Descurainia Sophia L.) seeds, known as an herbal medicine, for the first time are used as a promising pore-forming agent (pore-former) in ceramic technology. Flixweed seeds were selected because of their unique constant shape (oblong, 1.2 mm long with the aspect ratio of about 2) and narrow size distribution as well as their low-cost. Porous zirconia ceramics have been fabricated using flixweed seeds by tape casting technique. The dried tape-cast cut into disk-shaped pieces and were fired at 1400°C for 2h, resulting in porous zirconia disks with a bulk density of 3.96 g/cm3, total porosity of 34.6 ± 0.9% (open porosity 25.5 ± 0.7%, closed porosity 9.1 ± 0.3%) and a linear shrinkage of 21.5 ± 0.3%. The pore shape and size were similar in shape and size to the original pore-former.

Objective: The mechanical behaviour or the Young’s Modulus of the skin is measured as a ratio of the stress applied to the skin in vitro or in vivo over the skin deformation. The Young’s Modulus of skin is an important factor to estimate the characteristics of skin, to determine the course of a disease or to follow a cosmetic application. Methods: The mechanical behaviour of the skin is measured by changing the shape of skin by employing tensile, indentation, and suction and torsion tests. Results: Out of all the skin’s mechanical testing methods, suction tests are a common choice for skin testing, as they are easy to apply in vivo and consider both in-plane and normal loading conditions. Skin is found to be highly anisotropic and viscoelastic, with a range of Young’s Modulus between 5 kPa and 140 MPa. Conclusion: This paper reviews in vivo and in vitro reported values for Young’s Modulus of human skin for tensile, indentation, suction and torsion mechanical testing methods.

Low velocity single-bounce impact tests have been conducted on filament-wound glass fiber reinforced/vinylester and glass fiber reinforced/epoxy composite pipes. An instrumented drop weight testing system was used for the impact testing. The tests were performed on 300 mm long sections of 150 mm diameter pipes having 6 mm wall thickness. The impact energy required to just initiate the damage in glass fiber reinforced/epoxy pipes was found to be larger than the energy needed for glass fiber reinforced/vinylester pipe. The load-time curves also reveal that vinyl ester-based pipes exhibit a ductile failure under impact, whereas, in the epoxy-based pipes the failure was rather brittle in nature.

Strontium doped zirconium oxide (SZO) nano particles were synthesized by a hydrothermal particle growth technique and were employed for removal of Cu (II) from water. The synthesized nano adsorbents were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and UV-visible spectral studies. The adsorption experiments were affected in batch to establish the influence of pH, contact duration/time, temperature and initial metal ion concentration on adsorption efficiency. This work demonstrates the success of employing SZO nano adsorbents towards efficient removal of Cu (II) from water.

TiAlN and AlCrN coatings were deposited on mild steel (EN 353 steel) by cathodic arc evaporation technique. Coefficients of friction, critical load, adhesive and cohesive properties of these coatings were studied using scratch tester. Failure mode for coatings with thickness of 2 and 4 μm were studied using scratch channels and acoustic activities as basis. Studies presented relationship between progressive and in situ emission signals. AlCrN coating exhibited higher critical load as determined by the acoustic emission signal. Additionally wear mechanisms were analyzed. Analysis of the experimental results showed that load carrying capacity of AlCrN coating is better than TiAlN coating. Scratch wear test of AlCrN coated substrates showed reduction in cracking and spalling of coated layers.

First-principles calculations are used to investigate the structural, electronic, and magnetic properties of CdCr2O4 with magnetic Cr cations, focusing on the changes through the magnetic phase transitions which shows relief of the geometric frustration of the ferromagnetic and antiferromagnetic orderings on the pyrochlore lattice. We computed the structural and electronic properties for the paramagnetic, ferromagnetic and antiferromagnetic orderings in cubic ( F 3 dm) and tetragonal (I41 ⁄amd) structures of CdCr2O4. We optimized the crystal structures with the PM, FM and AFM orderings using a pseudopotential plane wave (PP-PW) method within the generalized gradient approximation (GGA), and computed the electronic properties to investigate the magnetic properties in the geometrically frustrated ferromagnetic and antiferromagnetic spinel CdCr2O4 based on density functional theory and understanding of the principles of Quantum ESPRESSO in magnetic materials. On the other hand, the effect of magnetism were obtained and analyzed on the basis of density of states (DOS), projected density of states (PDOS), and charge density distribution.