Advanced Materials and Processes Research Institute
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Influence of microstructure and experimental parameters on the erosion–corrosion behavior of Al alloy composites.
No full textThe influence of material related parameters such as alloy composition and reinforcement volume fraction and the experimental parameters such as the slurry concentration and rotational speed on the erosion–corrosion behavior of SiC particle reinforced aluminum alloy composites in saline, acidic and basic environments is studied. It is observed that 2014–SiC composite exhibited better wear resistance than LM13–SiC composite in acidic and NaCl media. Further both the composites exhibited better wear resistance than their matrix alloys in these environments irrespective of the sand content in the slurry and the rotational speed. The wear rates increased with increasing sand content in both the media. Al/Si/precipitate interfaces were found to be the preferential sites for corrosive attack in both the alloys and composites. In basic media the trend was reversed with both the composites exhibiting lower wear resistance than their matrix alloys. Further 2014–SiC composite exhibited lower wear resistance than LM13–SiC composite in basic media
Sliding wear response of a cast iron under varying test environments and traversal speed and pressure conditions
No full textThis study pertains to the examination of sliding wear behaviour of a gray cast iron over a range of sliding speeds and applied pressures in dry and (oil and oil plus graphite) lubricated conditions. Wear properties characterized were wear rate and frictional heating. The cast iron revealed various forms and sizes of graphite particles in a matrix of pearlite and limited quantity of free ferrite. Different solidification patterns, as controlled by the chemical composition and/or carbon equivalent of the alloy and rate of cooling, were thought to be responsible for the varying morphology of the graphite phase formed in the material matrix. Occasional decohesion of graphite at ferrite/graphite interfacial regions was also observed.\ud
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The wear rate of the cast iron increased with the speed and pressure of sliding due to increasing severity of wear condition. The specimens tended to lose proper contact with the disc at larger pressures when slid dry. This was attributed to severe cracking tendency of the material. On the contrary, specimen seizure was noticed in the oil and oil plus graphite lubricated conditions; the seizure resistance (pressure) decreased with sliding speed in presence of the lubricants. The wear rate versus pressure plots attained different slopes, i.e. the rate of increase in wear rate with pressure, depending on the test environment. One slope and inappreciable effect of pressure on wear rate were noticed due to substantial cracking tendency of the cast iron when tested in dry condition. In the oil lubricated condition also, virtually one slope was observed but it was higher than that in dry condition indicating greater sensitivity of wear rate towards the applied pressure. Also, the samples attained lower wear rate in oil than in dry condition in view of suppressed cracking tendency causing more stable lubricating film formation in presence of the oil lubricant. Addition of graphite particles to the oil lubricant caused a further reduction in wear rate because of the enhanced possibility of a more stable lubricant film formation due to smearing of the graphite particles. In this case, the slope of the wear rate versus pressure plots was the least in the intermediate range of pressures irrespective of the sliding speed owing to more stable lubricating film formation.\ud
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A higher rate of temperature increase with test duration (intermediate sliding distance) in the beginning was attributed to the abrasive action of the hard debris generated through the fragmentation of the initially contacting asperities. A subsequently observed lower rate of increase at longer durations could be owing to the occurrence of mild wear condition in view of less stressing of the contacting asperities and increased stability of the lubricant film formed. Increase in the rate of frictional heating at still longer durations resulted from destabilization of the lubricating film.\ud
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Frictional heating increased with applied pressure and sliding speed in view of increasing severity of wear condition. The rate of increase in frictional heating was low initially up to a specific pressure followed by a higher rate of increase at still larger pressures when the tests were conducted in oil plus graphite at both the sliding speeds and in the oil lubricant at the lower speed. A constant (high) rate of increase in frictional heating with pressure was noticed in the dry condition at both the sliding speeds and in the oil lubricant at the higher speed. Low rate of frictional heating with pressure was attributed to the occurrence of mild wear condition while a higher rate of frictional heating with pressure resulted from the occurrence of severe wear condition. As far as the influence of test environment on frictional heating is concerned, least frictional heat was generated in the oil plus graphite lubricant mixture while the maximum was noticed in dry condition, intermediate response of the samples being observed in oil. Formation of more stable lubricating film was thought to be responsible for lower frictional heating in the lubricated conditions; the presence of graphite in the oil lubricant increased the extent of lubricating film formation and stability of the film so formed.\ud
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The wear response of the samples has been explained in terms of cracking tendency and lubricating effects of graphite, predominance of the counteracting effects of the two parameters over each other, and lubricating film formation by the external oil (plus graphite) lubricant on the sliding surfaces in specific test conditions. Characterization of wear surfaces, subsurface regions and debris particles of the material enabled to further substantiate the observed wear performance of the samples.\u
`Radioneuclide sorption onto low-cost mineral adsorbent’.
No full textThis paper investigates the underlying mechanism of the removal of hexavalent uranium radionuclides from 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 solutions. Pseudo-first-order and pseudo-second-order rate expressions have been used to test the experimental data. The rate constants of adsorption for both the kinetic models have been calculated. The pseudo-second-order 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 radionuclide-sorbed mineral adsorbent indicates the precipitation of new compound at a higher radionuclide concentration (>100 mg/L)
Jarosite characteristics and its utilisation potentials
No full textDuring metallic zinc extraction from zinc sulphide or sulphide ore, huge quantity of jarosite is being released universally as\ud
solid residues. The jarosite mainly contains iron, sulphur, zinc, calcium, lead, cadmium and aluminium. Jarosite released from\ud
such industrial process is complex and its quality and quantity make the task more complex for safe disposal. Apart from water\ud
contamination, jarosite already accumulated and its increasing annual production is a major source of pollution for surrounding\ud
environment including soil, vegetation and aquatic life and hence its disposal leads to major concern because of the stringent\ud
environmental protection regulations.\ud
An attempt was made to evaluate the characteristics of Indian jarosite with an objectives to understand its potentials for\ud
recycling and utilising as raw materials for developing value added products. Sand and Coal Combustion Residues (CCRs) was\ud
used as an admixture to attain good workability and detoxify the toxic substance in the jarosite. Result revealed that jarosite is silty\ud
clay loam in texture having 63.48% silt sized and 32.35% clay sized particles. The particle size of jarosite (D90=16.21F0.20 Am)\ud
is finer than the CCRs (D90=19.72F0.18 Am). The jarosite is nonuniform in structure and shape as compared to the CCRs having\ud
spherical, hollow shaped and some of them are cenosphere in nature. The major mineral phase of jarosite is Potassium Iron\ud
Sulphate Hydroxide {KFe3(SO4)2(OH)6}and Iron Sulphate Hydrate {2Fe2O3SO3d 5H2O}. In CCRs the dominant phases are\ud
quartz {SiO2}, mullite {3Al2O3d 2SiO2} and hematite {Fe2O3}. The high electrical conductivity of jarosite (13.26F0.437 dS/m)\ud
indicates that the presence of cations and anions are predominant over CCRs (0.498F0.007 dS/m).\ud
The major portion of jarosite consists of iron (23.66F0.18%), sulphur (12.23F0.2%) and zinc (8.243F0.075%). But\ud
CCRs main constituents are silicon ( 27.41F0.74%), aluminium (15.167F0.376%) and iron (4.447F0.69%). The other\ud
constituents such as calcium, aluminium, silicon, lead, and manganese are also present in the range of 0.5 to 5%. Heavy metals\ud
such as copper, chromium, and cadmium are found higher in jarosite as compared to the CCRs. The statistically designed\ud
experimental trials revealed that the density, water absorption capacity and compressive strength of fired jarosite bricks are 1.51\ud
gm/cm3, 17.46% and 43.4 kg/cm2 respectively with jarosite sand mixture in the ratio of 3:1 indicating the potentials in\ud
developing building material
Effects of Heat Treatment on the Lubricated Sliding Wear Behaviour of Zinc–Based Alloy Containing Nickel under Varying Test Conditions
No full textA Comparative Assessment of the Behavior of Al–Cu Alloy and Its Composite
No full textAn Al–Cu alloy (corresponding to the 2014 series) is used to make a omposite by the addition of 15wt% SiC dispersoids adopting the liquid metallurgy route by stir casting. The alloy and the composite are subjected to solutionizing and\ud
aging to optimize the attainable properties. They are characterized for their physical, microstructural, hardness, tensile, dry sliding, and abrasive wear (under high stress\ud
conditions) properties under identical experimental conditions. The obtained results indicate that the formation of the composite does not always improve the properties.\ud
A clear distinction can be made between the properties of alloys which can be improved by the formation of a composite. In other cases, the formation of a composite has resulted in deteriorating the properties of the alloy. The present study analyzes the causes for the behavior exhibited by the alloy and the composite and attempts to lay down conditions under which composites can be successfully used\ud
over their counterpart alloys and vice vers
Effect of SiC addition and running-in-wear on the sliding wear behaviour of Al–Zn–Mg aluminium alloy
No full textSliding wear behaviour of Al–Zn–Mg alloy and Al–Zn–Mg–SiC particle composite was studied under varying applied load. Effects of running-in-wear on sliding wear characteristics of the alloy and composite was studied giving emphasis on the parameters such as coefficient of friction, rise in temperature, wear rate and seizure pressure. The seizure pressure of composite was noted to be significantly higher than that of the alloy and is increased further due to running-in-wear prior to the test. The running-in-wear also improved the wear resistance and seizure pressure of the alloy, whereas both the coefficient of friction and temperature rise are reduced due to running-in-wear. However, the level of improvement in seizure pressure due to running-in-wear is relatively less in composite (22%) as compared to that in alloy (40%). These facts have been discussed on the basis of nature of worn surface produced after running-in-wear. The worn surface was studied in detailed through scanning electron microscopy, EDX analysis and X-ray diffraction measurement. Transfer of counter surface material, the formation and stability of mechanically mixed layer (MML) in the investigated materials were assessed indirectly through these analyses. The MML is noted to be more stable in running-in-wear samples as compared to the fresh samples both in alloy and composites
Thermal Stabilization of Metal Finishing Waste with Clay.
No full textThermal treatment of metal finishing waste with locally available clay, in their varying ratios, was carried out at 850°C and\ud
above temperatures. In the presence of 1:1 ratio of waste and clay a solidified product was obtained at 950°C. Measurement\ud
of an appreciably high compressive strength, ~ 500 kg cm-2 and a very small (0.4%) water absorption from the solidified\ud
product indicated its stable nature. Toxicity Characteristic Leaching Procedure (TCLP) test of the waste showed nearly 85 to\ud
90% decrease of leaching of Fe, Cu, Ni, Zn, Mn and Cr after thermal treatment compared to their leaching without\ud
treatment. No hexavalent chromium{Cr(VI)} was observed from the leachate of the solidified product. This indicates the\ud
absence of re-oxidation phenomena of chromium during thermal treatment up to 950°C. X - ray diffraction (XRD) of\ud
solidified product indicated the presence of hematite, and aluminum silicate as main phases of the solidified product.\ud
Involvement of the above waste metals with these phases during thermal treatment could be the reason for their\ud
immobilization
Influence of steady shear flow on dynamic viscoelastic properties of un-reinforced and Kevlar, glass fibre reinforced LLDPE
No full textAn experimental study was conducted to observe the effects of parallel-superposed flow condition\ud
on viscoelastic properties of LLDPE, Kevlar fibre reinforced LLDPE and hybrid of short glass fibre and Kevlar\ud
fibre reinforced LLDPE. Parallel-plate rheometer was employed for these tests. Rheological parameters\ud
such as loss modulus (G²) and dynamic viscosity (h¢) do not vary significantly on superposing steady state\ud
shear with oscillatory shear in the studied range of experiment at 185°C in un-reinforced LLDPE. Kevlar\ud
fibre reinforced LLDPE and Kevlar/glass fibre reinforced LLDPE showed significant changes in the flow\ud
behaviour under various sets of superposed conditions. Storage modulus (G¢), and G² become highly sensitive\ud
to low oscillatory angular frequencies (w) under superposed conditions. These curves show two different regions\ud
with increased w value. At low w values, parameters G¢ and G² change sharply reaching a certain value, thereafter,\ud
changes are moderate with increased w. In case of h¢ a maxima is observed, position of which, depends upon\ud
the value of steady shear rate. Maxima shifts towards higher frequencies with the increased steady shear rate