5. Miscellaneous Publications
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/13843
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Item Item Review of microstructure evolution in hypereutectic Al-Si alloys and its effect on wear properties(2014) Vijeesh V.; Prabhu K.N.Al-Si alloys with silicon content more than 13 % are termed as hypereutectic alloys. In recent years, these alloys have drawn the attention of researchers due to their ability to replace cast iron parts in the transportation industry. The properties of the hypereutectic alloy are greatly dependent on the morphology, size and distribution of primary silicon crystals in the alloy. Mechanical properties of the hypereutectic Al-Si alloy can be improved by the simultaneous refinement and modification of the primary and eutectic silicon and by controlling the solidification parameters. In this paper, the effect of solidification rate and melt treatment on the evolution of microstructure in hypereutectic Al-Si alloys are reviewed. Different types of primary silicon morphology and the conditions for its nucleation and growth are explained. The paper discusses the effect of refinement/modification treatments on the microstructure and properties of the hypereutectic Al-Si alloy. The importance and effect of processing variables and phosphorus refinement on the silicon morphology and wear properties of the alloy is highlighted. © 2013 Indian Institute of Metals.Item Review on microstructure evolution in Sn-Ag-Cu solders and its effect on mechanical integrity of solder joints(2013) Sona M.; Prabhu K.N.The use of Pb-bearing solders in electronic assemblies is avoided in many countries due to the inherent toxicity and environmental risks associated with lead. Although a number of "Pb-free" alloys have been invented, none of them meet all the standards generally satisfied by a conventional Pb-Sn alloy. A large number of reliability problems still exist with lead free solder joints. Solder joint reliability depends on mechanical strength, fatigue resistance, hardness, coefficient of thermal expansion which are influenced by the microstructure, type and morphology of inter metallic compounds (IMC). In recent years, Sn rich solders have been considered as suitable replacement for Pb bearing solders. The objective of this review is to study the evolution of microstructural phases in commonly used lead free xSn-yAg-zCu solders and the various factors such as substrate, minor alloying, mechanical and thermo-mechanical strains which affect the microstructure. A complete understanding of the mechanisms that determine the formation and growth of interfacial IMCs is essential for developing solder joints with high reliability. The data available in the open literature have been reviewed and discussed. © 2013 Springer Science+Business Media New York.Item Reactive wetting, evolution of interfacial and bulk IMCs and their effect on mechanical properties of eutectic Sn-Cu solder alloy(2011) Satyanarayan; Prabhu K.N.Lead free solders are increasingly being used in electronic applications. Eutectic Sn-Cu solder alloy is one of the most favored lead free alloys used for soldering in electronic applications. It is inexpensive and principally used in wave soldering. Wetting of liquid solder on a substrate is a case of reactive wetting and is accompanied by the formation of intermetallic compounds (IMCs) at the interface. Wettability of Sn-0.7Cu solder on metallic substrates is significantly affected by the temperature and the type of flux. The wettability and microstructural evolution of IMCs at the Sn-0.7Cu solder/substrate interfaces are reviewed in the present paper. The reliability of solder joints in electronic packaging is controlled by the type and morphology of interfacial IMCs formed between Sn-0.7Cu solder and substrates. The formation and growth mechanisms of interfacial IMCs are highlighted. Mechanical behavior of bulk solder alloy and solder joint interfaces are analyzed. The characteristics of the IMCs which have marked effect on the mechanical properties and fracture behavior as well as reliability of solder joints of the alloy are discussed. An attempt has also been made to discuss the effect of cooling rate and strain rate on shear strength, tensile properties and creep resistance of the solder alloy. It is recommended that future work should focus on evolving a standard procedure involving sequential assessment of wetting behavior, evolution of IMCs and mechanical properties. © 2011 Elsevier B.V.Item Preparation, characterization and performance study of poly(isobutylene- alt-maleic anhydride) [PIAM] and polysulfone [PSf] composite membranes before and after alkali treatment(2011) Padaki M.; Isloor, A.M.; Belavadi G.; Prabhu K.N.Recently, nanofiltration (NF) membranes have been drawing much attention in the field of filtration and the purification process of water/industrial effluents, because of their energy efficiency and low cost. Although reverse osmosis (RO) membranes are widely used in present desalination units, NF membranes are considered as "future membranes" for desalination, because of the low operating pressure. In the present paper, we hereby report the synthesis of a new composite NF membranes of poly(isobutylene-alt-maleic anhydride) (PIAM) with polysulfone, using a diffusion-induced phase separation (DIPS) method. The anhydride groups were converted to acid group by alkaline treatment. Newly prepared composite membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) studies. The membranes were tested for salt rejection and water swelling. The resulted NF membranes exhibited significantly enhanced water permeability while retaining high salt rejection. The flux and rejection rate of the NF membrane to Na2SO4 (500 ppm) reached to 11.73 L/(m2 h) and 49% rejection under 1 MPa and also 70:30 composition of the membrane showed 54% water swelling; contact angle measurement, ion exchange capacity, and water uptake of the membrane were recorded. © 2011 American Chemical Society.