Advanced Materials and Processes Research Institute
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Rheology of LCP/PET Blends at Solid and Molten States of LCP
No full textLiquid crystalline polymer (LCP) and polyethylene terephthalate (PET) were blended in an elastic melt extruder\ud
to make samples having different volume fractions of constituent polymers. Shear stress, shear viscosity, first\ud
normal stress difference at different shear rates under steady state conditions of these blends were evaluated\ud
at two different temperatures 265 and 285˚C. The LCP was in solid state at 265˚C and in melt state at 285˚C and\ud
was dispersed in molten matrix of PET at both temperatures. Shear viscosity of blend increased with addition\ud
of LCP in PET matrix. A maxima was observed in viscosity versus composition plot. Blends containing more than\ud
50 vol. % of LCP in the blend show higher viscosity as compared to the constituent polymers. First normal stress\ud
difference, N1, increased with LCP content in the blend at 285˚C when ploted against shear stress whereas at\ud
265˚C this trend was opposite. The increased value of N1 with shear rate was explained assuming a tendency of\ud
asymmetric particles to rotate under velocity gradient of suspending medium. At 285˚C N1 varied with shear\ud
stress in two stages. First stage was characterized with high sensitivity of N1 with shear stress, which reduced in\ud
second stage on plastic deformation of LCP droplets
Effect of SiC concentration and strain rate on the compressive deformation behaviour of 2014Al-SiCp composite.
No full textThe compressive deformation behaviour of 2014Al-SiCp composites containing varying amount of SiCp has been studied at different strain rates (10−3 to 10−1 s−1). The composite materials were prepared through stir-casting (vortex) method. The yield stress, Young's modulus, percentage elongation and fracture stress were measured from the true stress–true strain plots. The Young's modulus of the materials was found to increase with increase in SiCp content. But the yield stress and the fracture stress do not follow any definite relationship with SiC content. The composite, containing 15 vol.% SiCp, exhibits minimum stress values irrespective of strain rates. The composite, containing either less or greater than 15 vol.% SiCp, exhibited almost same yield stress as that of the alloy. The elongation, in general, decreases with increase in SiCp. It was further found that the above parameters do not follow any definite trend of variation with strain rate for any investigated materials. The strain-hardening exponent and the strain rate sensitivity were determined for each of the materials at different strain rates. It was noted that the plastic strength coefficient also follows the same trend of variation with SiCp content irrespective of strain rate; but the strain-hardening exponent increases marginally with increase in SiCp content. The strain-hardening exponent also remains invariant to strain rate. The strain rate sensitivity is noted to be very low. However, within this variation, the composite containing 15 vol.% SiC exhibits the minimum value of strain rate sensitivity. This also suggests that at room temperature, the cast alloy and/or composites are almost insensitive to strain rate.\u
Radionuclide Sorption onto Low-Cost Mineral Adsorbent.
No full textThis paper investigates the underlying mechanism of the removal of hexavalent uranium radionuclides from\ud
aqueous solution via a low-cost mineral adsorbent. Batch adsorption studies were performed for the concentration range of 50-4000 mg/L. The effects of contact times in the range of 10-3600 min (60 h), solution pHs in the range of 1-11, initial concentrations of metal ions in the range of 50-4000 mg/L, and interfering cations (such as Pb2+, Cu2+, Fe2+, Cd2+, Ni2+, Th4+, Ca2+, Na+, and K+) and interfering anions (such as SO4 -, CO3-, NO3-, and Cl-) were studied by equilibrating different concentrations of uranium\ud
solutions. Pseudo-first-order and pseudo-second-order rate expressions have been used to test the experimental\ud
data. The rate constants of adsorption for both the kinetic models have been calculated. The pseudo-secondorder\ud
rate reaction provides the best correlation of the data. The values of adsorption data were fitted to Freundlich, Langmuir, and Dubinin-Radushkorich (D-R) adsorption isotherms. The mean energy of adsorption was calculated to be 10.10 kJ/mol from the D-R adsorption isotherm. The probable mechanism of radionuclide removal was its dissolution, followed by subsequent precipitation. X-ray diffractograms of the radionuclidesorbed mineral adsorbent indicates the precipitation of new compound at a higher radionuclide concentration (>100 mg/L)
Effect of temperature on electrical behavior of flyash-filled epoxy gradient composites
No full textFunctionally gradient composites of epoxy resin having different weight percentages of flyash were prepared under centrifugal force to obtain gradient in density, hardness, and electrical properties. Effect of temperature and frequency variation on dielectric constant (ε′), tan δ, and ac conductivity was determined by using a 4274 A Multi-Frequency LCR meter. Electrical measurements were carried out in a temperature range from 40 to 180°C and in a frequency range from 1 to 100 kHz. It was observed that the dielectric constant and tan δ increased with increase in temperature and decreased with increase in frequency. The ac conductivity increases with increase in temperature and frequency. The increased weight percentage of flyash increased the compaction of flyash particle in the flyash-rich phase of graded composites, which would have increased the dielectric constant (ε′), tan δ, and ac conductivity. Shore D hardness and density of the functionally gradient composites has also been determined and reported. A continuous increase in the hardness from 69 to 76 and density from 1.287 to 1.41 g/cc has been observe
High Stress abrasive wear behavior of aluminium hard particle \ud composites: Effect of experimental parameters, particle size and volume fraction
No full textHigh stress abrasive wear behaviour of aluminium alloy (ADC-12)–SiC particle reinforced composites has been studied as a function of applied load, reinforcement size and volume fraction, and has been compared with that of the matrix alloy. Two different size ranges (25–50 and 50–80 μm) of SiC particles have been used for synthesizing ADC-12–SiC composite. The volume fraction of SiC particles has been varied in the ranges from 5 to 15 wt%. It has been noted that the abrasive wear rate of the alloy reduced considerably due to addition of SiC particle and the wear rate of composite decreases linearly with increase in SiC content. It has also been noted that the wear resistance of composite varies inversely with square of the reinforcement size. The wear rate of the alloy and composite has been found to be a linear function of applied load but invariant to the abrasive size; at critical abrasive size, transition in wear behaviour is noted. This has been explained through analytically derived equations and wear–surface examination.\ud
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Wear and electrochemical characterization of sol-gel alumina coating on chemically pre-treated mild steel substrate.
No full textIn the present investigation sol-gel based alumina coating was obtained using aluminium alkoxide as the precursor material. The coating was deposited on a mild steel substrate by a dip coating technique. Chemical pretreatment (phosphating) was done on one set of mild steel samples prior to deposition of the alumina coating in order to improve the bonding characteristics. After deposition of the coating, corrosion and wear properties of coated and uncoated mild steel surfaces were evaluated. In electrochemical characterization, open circuit potential (OCP) variation with time, potentiodynamic polarization and electrochemical impedance measurements were carried out in 3.5% NaCl solution at room temperature. Two body (high stress) abrasive wear tests were performed to measure the abrasion resistance of the coating. Microstructural and elemental composition of the coating was investigated by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDXS). The experimental results indicated the occurrence of significantly higher corrosion and wear resistance of pre-phosphated alumina coated samples as compared to alumina coated samples without pre-phosphating. Presence of phosphorus and zinc in the intermediate phosphating layer appears to increase the bonding and corrosion resistance properties of the outer alumina layer. Results have been discussed in terms of the observed data related to electrochemical and wear studies
Simulation of Compositional Profile in Functionally\ud Graded Materials.
No full textThe development of a polymer based functionally graded material (FGM) of desired composition profile by the centrifugation technique requires control on centrifugation, size, shape, and concentration of suspended particles, time, viscosity variation of polymerizing fluid, etc. A simulation was conducted to observe the compositional variations with time at different places of FGM, using a modified terminal velocity equation for particle movement in polymerizing fluid. It was further modified for the particles having different sizes. The simulation demonstrated two graded-composition profiles each one in low concentration region from where particles were moved to the other part of sample and second high concentration profile in which particles entered to increase the concentration. The third region situated between the two composition profiles was observed as that of uniform distribution of particles and the length of this region can be controlled by adjusting the size of the centrifuged sample. The simulation was compared with the experimental results of FGM having SiC particles in polysulphide epoxy resin.\u
Influence of alumina dispersoid and test parameters on erosive\ud wear behaviour of a cast zinc–aluminium alloy.
No full textObservations made pertaining to the erosive wear characteristics of a cast zinc-based alloy and its composite containing 10 wt.% (corresponding to 11.2 vol.%) alumina particles have been presented in this study. Matrix alloy has also been tested under identical test conditions in order to examine the role played by second phase alumina particles on the erosive wear resistance of the matrix alloy. Eroded surfaces and subsurface regions of the specimens were also characterized to understand the operating wear mechanisms.\ud
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The composite exhibited higher erosive wear resistance (inverse of erosive wear rate) than the unreinforced matrix alloy in general. Further, the wear rate increased with increasing impingement velocity as also evident from higher surface damage. Increasing angle of impingement at lower impinging velocity led to reduced erosive wear rate. On the contrary, the erosive wear rate increased initially with impingement angle, attained the peak and then decreased at still higher angles at the higher impingement velocity. The eroded surfaces showed more abrasion grooves at lower impingement angle and greater tendency of crater formation at higher angles of attack. In case of the composite, protrusion and fracture of the dispersoid phase was also noted. The composite also revealed less severe surface and subsurface damage than the matrix alloy.\u