Sampad Kumar Biswas

Electro Discharge Machining of Titanium Nitride-Aluminium Oxide Composite for Optimum Process Criterial Yield

Titanium nitride-aluminium oxide (TiN–Al2O3) is a new generation ceramic composite material having potential for many industrial applications as it possesses high resistance to thermal degradation, anti-wear and anti-abrasion properties. But conventional machining of such ceramic composite is difficult to perform for some of its peculiar properties like anisotropy, low thermal conductivity, and abrasive nature of the reinforcing phases. In the present investigation, non-conventional machining like electro discharge machining (EDM) has been carried out to machine the material. Energy dispersive X-ray spectroscopy and X-ray diffraction analysis have also been carried out on the composite matrix to verify the presence of two distinguishable phases of TiN and Al2O3. The present article reports the effects of EDM process parameters on material removal rate, electrode wear rate, radial overcut, and taper angle while machining TiN–Al2O3 composite. The characteristic features of the EDM process are explored through Taguchi L9 orthogonal array design–based experimental studies with various process parametric combinations. Finally, optimum parameter settings for each response factor are obtained and tested through verification experiments. The whole experimental study indicates that EDM has a very good potential in machining of TiN–Al2O3 ceramic composite in some particular ranges of process parameters.

Effects of Process Parameters on Hole Circularity and Taper in Pulsed Nd:YAG Laser Microdrilling of Tin-Al2O3 Composites

This study investigates the effect of five parameters on circularity and taper of drilled holes in pulsed Nd:YAG laser microdrilling process. The effect of various process parameters like lamp current, pulse frequency, pulse width, air pressure, and focal length of Nd:YAG laser microdrilling on hole circularity at entry, exit, and taper has been investigated through response surface methodology (RSM)–based experimental study. The significant parameters have been selected based on the analysis of variance (ANOVA). The parametric combination for optimal hole circularity and hole taper has also been evaluated. In micromanufacturing, circularity of a drilled hole at entry, exit, and taper are important attributes which greatly influence the quality of a drilled hole. The drilling operation has been carried out on titanium nitride-alumina (TiN-Al2O3) composite, an important electroconductive ceramic suitable for wear and heating applications.

Single step aqueous synthesis of pure rare earth nanoparticles in biocompatible polymer matrices

The room temperature synthesis of water soluble, stable rare earth (RE) metal nanoparticles (MNPs) with controlled size is a long standing interest. In the present work, we have established a synthetic strategy for the preparation of pure europium (Eu0) metal nanoparticles (NPs) in aqueous solution employing a γ-radiolytic reduction technique. Since radiolysis is the cleanest method amongst all other chemical routes, we preferentially choose this technique for the reduction of precursor Eu3+ ions to nanoscale metals in our work. This has been possible as hydrated electrons (e−aq) having a very high reduction potential (E0(H2O/e−aq) = −2.87 VNHE) produced in situ can efficiently reduce Eu3+ to Eu0. Synthesized Eu0 MNPs were stabilised within the matrices of biocompatible polymers, polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP). Reduction of the metal ion has been conducted at different irradiation doses with a maximum dose of 83.88 kGy. The irradiated solution shows an absorption maximum at 266 ± 2 nm and an emission maximum at 394 ± 5 nm. Analysis of transmission electron microscopy (TEM) images shows that the average sizes of PVA and PVP encapsulated Eu0 NPs are 13 ± 0.6 nm and 17 ± 1.01 nm, respectively ([Eu3+] = 5.0 × 10−3 mol dm−3, [polymer] = 1.0%). Formation of monodisperse pure Eu0 MNPs was further characterised by dynamic light scattering (DLS), energy dispersive X-ray (EDX) as well as Fourier transformed infrared (FTIR) spectroscopy and cyclic voltammetry (CV) studies.

Pareto Optimization of Electro Discharge Machining of Titanium Nitride-Aluminium Oxide Composite Material Using Genetic Algorithm

Titanium nitride-aluminium oxide (TiN-Al2O3) is a new generation ceramic composite material having potential for many industrial applications as it possess high resistance to thermal degradation, anti-wear and anti-abrasion properties. In the present research the characteristic features of EDM process are explored through Taguchi methodology based experimental studies with various process parametric combinations. Finally the process has been optimized using Genetic algorithm based Pareto optimization search. From Pareto optimal search the technology guideline for optimal parameter settings have been selected. The present research approach is extremely useful for maximizing the productivity while maintaining the geometrical accuracy within desired limit.

Mechanical Properties of Shock Treated Aluminium Alloy Al 2024-T4

Plate impact experiment has been carried out on Al 2024-T4 alloy using single stage gas gun. The dynamic yield strength and spall strength of Al 2024-T4 sample has been determined to be 0.35 GPa and 1.43 GPa, respectively, from free surface velocity history measured using VISAR. The sample recovered after unloading from peak shock pressure of 4.4 GPa along with an unshocked sample is analyzed for mechanical properties using nano-indentation and scanning electron microscopy (SEM). The nano-indentation measurements reveal that the hardness and Youngs modulus for unshocked sample remains unchanged as a function of load (equivalently depth), however, the same for shocked sample decreases monotonically with increase of load up to ~40 mN and on further increase of load it remains unchanged, suggesting the (i) increase in hardness of shock loaded sample; (ii) the increase in hardness is limited to certain depth, which in our case is 845.12 ? 43.16 nm.

Enrichment of Metallic Single-Walled Carbon Nanotubes with Simultaneous Purification by Nitric Acid Treatment

Controlled treatment of pristine single-walled carbon nanotubes (SWCNT) with HNO3 (11 M) for 20 hours at 50°C with subsequent repeated cycles of washing, centrifugation and ultrasonication in aqueous media have shown enrichment of the product with pure and debundled nanotubes of metallic variety. On the other hand, no such enrichment was observed when the tubes were treated with a mixture of concentrated nitric acid and sulfuric acid. The electrical varieties of the tubes were ascertained from the analysis of Raman and UV-Vis spectra and dc-resistivities. The purity of the product was gauged from transmission electron microscope images, energy dispersive spectra, thermogravimetric analysis and Raman spectra. A mechanism involving preferential attack of NO3− on the semiconducting tubes under the condition of the adopted protocol has been proposed from the comparison of the results after the treatment of the same pristine SWCNT with mixed acid (conc. HNO3 and H2SO4).

Nitride & Oxy-Nitride Ceramics for High Temperature and Engineering Applications

Nitrides and oxynitrides of silicon and aluminum occupy prominent positions among other non-oxide members of ceramics on account of their inherent unique combination of properties arising out of their directional covalent bonding in the condensed state. Since many reviews could be found in the literature on the materials either individually or combining some of them, the present article is devoted to the key areas of the present research on the developments of these materials. For example, α’ – SiAlON is now attracting significant attention and the article highlights how compositional variations could lead to easy densification and improvement of its mechanical properties. Experimental results from various authors show that the mechanism of stabilization of α’ – SiAlON is very complex and cannot be explained on the basis of the size of the metal cations and solubility in the transient glassy phase. Y, Yb, Dy and to some extent Ca are good for stabilization of the phase. Evolution of different phases during temperature rise and how these phases affect sintering of the α’ material has been presented in this article. In-situ formation of elongated β’ grains have been shown to increase the toughness of the material. Simultaneously, the development of AlN ceramics in regard to application of this ceramic in different areas apart from that of microelectronics has been discussed. +Improved mechanical and electrical properties of AlN and its composites have shown their promise in diverse applications such as armors, electron tube components and dielectric devices.

Oxidation of Silicon Nitride Sintered with Yttria and Magnesia Containing Nitrogen Rich Liquid

Oxidation of pressureless sintered Silicon Nitride densified with a Nitrogen rich liquid phase in Y2O3-AlN-SiO2 and MgO-AlN-SiO2 systems have been studied. Thermogravimetric studies indicate a parabollic kinetics. Activation energies are 188 and 430 kJ/mole for the oxidation of materials densified with 11.89 and 23.15%. additives containing Y2O3 and 390 kJ/mole for those densified with 21% additives containing MgO.XRD studies show that the oxidation products are SiO2(Cristobalite), Si2ON2,YAlO3 (above 1250C) and Y2Si2O7 in case of Yttria containing additives and SiO2(Cristoballite),Si2ON2, MgSiO3(Protoenstatite),Mg2SiO4(Forsterite) and MgAl2O4(Spinel) in case of Magnesia containing aditives. XPS study shows the presence of a silicate phase in the outermost laver of the oxidised surface. Oxidation of MgO containing material is higher than that of Y2O3 containing material.

Improvement in hardness of soda-lime-silica glass

Hardness is a key design parameter for structural application of brittle solids like glass. Here we report for the first time the significant improvement of about 10% in Vickers hardness of a soda-lime-silica glass with loading rate in the range of 0.1-10 N.s−1. Corroborative dark field optical and scanning electron microscopy provided clue to this improvement through evidence of variations in spatial density of shear deformation band formation as a function of loading rate.

Comparative Study of Indentation Size Effects in As-Sintered Alumina and Alumina Shock Deformed at 6.5 and 12 GPa

Nanohardness of alumina ceramics determines its performance in all contact-related applications because the issue of structural integrity gets determined at the nanoscale of contact. In spite of the wealth of the literature, however, it is not yet known in significant details how the high-strain rate flyer-plate impact at different pressure affects the nanohardness of dense, coarse grain alumina ceramics. Thus, the load controlled nanoindentation experiments were performed with a Berkovich indenter on an as-received coarse grain (~10 μm), high density (~3.98 gm·cc−1) alumina, and shock recovered tiny fragments of the same alumina obtained from gas gun experiments conducted at 6.5 GPa and 12 GPa shock pressures with stainless steel flyer plates. The nanohardness of the as-received alumina was much higher than that of the 6.5 GPa and 12 GPa shock-recovered alumina. The indentation size effect (ISE) was the strongest in alumina shocked at 12 GPa and strong in alumina shocked at 6.5 GPa, but it was mild in the as-received alumina sample. These results were rationalized by analysis of the experimental load depth data and evidences obtained from field emission scanning electron microscopy. In addition, a rational picture of the nanoindentation responses of the as-received and shocked alumina ceramics was provided by a qualitative model.