The amount of NCC was varied from 2 phr to 10 phr. Cure characteristics, mechanical properties, dynamic mechanical properties, thermal behavior, and transport properties of NBR-NCC composites were evaluated.
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NCC activated cure reaction upto 5 phr. The storage modulus E' increased up to 5 phr NCC loading; the reinforcing effect of NCC was seen in the increase of modulus which was more significant at temperatures above T g. The effect of nanofiller content and temperature on transport properties was evaluated. The solvent uptake decreased with NCC content. The mechanism of diffusion of solvent through the nanocomposites was found to be Fickian. Transport parameters like diffusion, sorption, and permeation constants were determined and found to decrease with nanofiller content, the minimum value being at 7.
Thermodynamic constants such as enthalpy and activation energy were also evaluated. The dependence of various properties on NCC was supported by morphological analysis using transmission electron microscopy. Tensile strength, stress at different elongations, flexural modulus, and abrasion resistance were analyzed and correlated with morphology. Finally different theoretical models were used to compare the experimental results with theoretical predictions. LaUma Devi, Bhagawan, S. The composite was fabricated at constant volume fraction of fiber 0. Keeping the volume fraction of matrix a constant 0.
Incorporation of 0. The tensile strength showed a further increase when the volume fraction is changed to 0.
A positive hybrid effect is observed for impact properties. Scanning electron micrographs of the fractured surfaces were examined to understand the fiber-matrix adhesion. This paper presents a method of frequency analysis for discrete signals using G-lets. From a group of transformations and representation theory, a finite basis of the signal space is obtained.
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The projections of the signal onto this basis are called G-lets. G-lets, due to the nature of transformations used, contain oscillations in such a manner that the difference between consecutive G-let coefficients is proportional to the local frequency. The signal frequency, in turn, is proportional to the difference in amplitude of the signal at any point.
Bidirectional charge-transfer behavior in carbon-based hybrid nanomaterials
A dilation operation is defined to capture the frequencies without use of a windowing function, by highlighting the highest frequency of the existing signal in a G-let. Considering features of a signal as a combination of frequencies, feature extraction of 1-D signals and images are examined. The beginning and end of each feature are identified by the spread of low frequencies in the neighborhood of a high frequency. Results are demonstrated using dihedral groups, for simple 1-D signals, an ECG signal, and 'Lena' image.
A qualitative comparison is provided with wavelets and Fourier analysis.
The morphology of the neat blends, microfibrillar blends and the corresponding microfibrillar composites based on low-density polyethylene and polyethylene terephthalate was analyzed. The tensile properties of the blends and microfibrillar composites increased with polyethylene terephthalate concentration up to an optimum level. The neat blends exhibited inferior tensile properties in comparison with the microfibrillar composites. As the polyethylene terephthalate concentration increased, the solvent uptake reduced. The diffusivity and permeability of the microfibrillar composites were lower than the corresponding blends.
The polyethylene terephthalate microfibrils in the microfibrillar composites offered a tortuous path for the diffusion of the solvent. Meera Balachandran, Dr. A Face Centred Central Composite Design FCCD with four factors and three levels was used to obtain the relationship between nanocomposite properties and levels of ingredients.
The factors considered in the design were silica content, nanoclay content, vulcanization system and dicumyl peroxide content. The nanocomposites were evaluated for tensile strength, modulus, elongation at break, oxygen permeation rate and effect of oil ageing on mechanical properties. Regression equations were generated to model the properties of interest and generate response surfaces and contour plots.
The predicted properties of the nanocomposites were in good agreement with the experimental results. The contour plots were overlaid within the applied constraints to identify the combination of factor ranges that gives the optimal performance of the nanocomposites for application in control system bladders for launch vehicle applications. The article describes the properties of nitrile rubber NBR -nanoclay composites prepared by a two-step method.
The tensile strength, elongation at break, modulus, storage modulus E' and loss modulus E" increased with the nanofiller content, reached the maximum value at 5 phr and decreased thereafter. The solvent uptake, diffusion, sorption and permeation constants decreased with nanoclay content with the minimum value at 5 phr nanoclay.
The mechanism of solvent diffusion through the nanocomposites was found to be Fickian. The dependence of various properties on nanoclay content was correlated to the morphology of the nanocomposites. George, E Jose, T. Commingling method was used to prepare the composites wherein the Polypropylene yarn PP yarn and jute yarn were wound together onto a metal plate in a particular configuration and then compression moulded. The mechanical properties of the composites prepared from chemically treated jute yarn were found to increase substantially compared to those of untreated ones.
The surface morphologies of the fracture surfaces of the composites were recorded using scanning electron microscope SEM. The SEM micrographs reveal that interfacial bonding between the treated jute yarn and the matrix has improved significantly by chemical treatments. The various chemical treatment mechanisms have been supported by FT-IR spectra. Theoretical modelling was used to predict the tensile properties and was found to be in accordance with the experimental results.
ACS Applied Nano Materials
Pramod Upadyayula and Rangarajan, M. V and Dr. Murali Rangarajan, and P, S. Different signal processing transforms provide us with unique decomposition capabilities. Instead of using specific transformation for every type of signal, we propose in this paper a novel way of signal processing using a group of transformations within the limits of Group theory. For different types of signal different transformation combinations can be chosen. It is found that it is possible to process a signal at multiresolution and extend it to perform edge detection, denoising, face recognition, etc by filtering the local features.
Without any approximation using Group theory it is seen that one can get close to this finite basis from different viewpoints. Dihedral groups have been demonstrated for this purpose. Meera Balachandran, Bhagawan, S.
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The mechanical behavior of acrylonitrile butadiene copolymer NBR -organomodified layered silicate nanoclay was modeled using design of experiments approach. A Box-Behnken design with three factors and three levels was used to model the relationship between properties of NBR nanocomposites and the ingredients. The factors considered in the design were silica content, nanoclay loading, and dicumyl peroxide content.
The nanocomposites were evaluated for tensile strength, modulus, elongation at break, oxygen permeation rate, and effect of oil and heat aging on mechanical properties. The contour plots were overlaid within the applied constraints to identify the combination of factor ranges that gives the optimal performance of the nanocomposites for application as control system bladders in satellite launch vehicles. Suresh, Maruthamuthu, S.
The changes in mechanical and surface properties were studied using tensile strength, elongation at break, wettability, surface morphology using SEM, surface topology by AFM, functional groups by FTIR spectroscopy, absorbance spectra by UV-Vis spectroscopy.
The thermally aged films with pro-oxidant additive added polyethylene PE exhibited a higher level of oxidation as revealed by increase in their carbonyl index than the pristine PE. The SEM micrograph reveals the increase in the size of cracks and grooves, according to the increase in the concentration of pro-oxidant additive. The surface roughness also supports the same through AFM image. The increase in the wettability and surface free energy of the thermally aged samples were attributed to the formation of hydrophilic groups on the polymer surface by thermo-oxidation.
The pro-oxidant additive offers a new insight into the thermo-oxidation strategy for PE and can be widely used in packaging industry. Nanocomposites were obtained from a masterbatch of acrylonitrile-butadiene copolymer NBR; nitrile rubber and organomodified layered silicate nanoclay prepared in an internal mixer followed by mixing with neat NBR and other compounding ingredients on a two-roll mill.
Addition of nanoclay reduced the cure time and the vulcanization kinetics closely fitted a first-order model. The morphology was investigated by X-ray diffraction and transmission electron microscopy. Sathiyan, Dr. Murali Rangarajan, and Ramachandran, S. Experimental studies were conducted in a spiral plate heat exchanger using the liquid-liquid two-phase system of water-diesel in different volume fractions and flow rates as the cold fluid. Experiments were conducted by varying the volumetric flow rate and temperature, keeping the volumetric flow rate of hot fluid constant.
The data obtained from fresh experiments were compared with the predictions of the obtained correlation.