Tapas Debnath - Academia.edu (original) (raw)

Papers by Tapas Debnath

Research paper thumbnail of Machinability Study of Rubber using USM for Microdrilling

Research paper thumbnail of Selective Etching of Aluminium 6068 Using Photochemical Machining

Research paper thumbnail of Synthesis and Characterization in the New System BI2(AL/GA)4O9 and 18O/16O Exchange Experiments

ABSTRACT Compositions in the new system BÍ2(GaxAli.x)409 (x = 0, 0.1, ...., 1) having mullite-typ... more ABSTRACT Compositions in the new system BÍ2(GaxAli.x)409 (x = 0, 0.1, ...., 1) having mullite-type structure were synthesized using precursor gels obtained from the solution of corresponding nitrates in glycerin. The effects of Ga/Al substitution were characterized by IR absorption ...

Research paper thumbnail of Fabrication of Ultrathin Sheet Using Wire-EDM

Techno-Societal 2018, 2019

Generally, sheet products (coins, gears, washers etc.) are fabricated using blanking and punching... more Generally, sheet products (coins, gears, washers etc.) are fabricated using blanking and punching operations. These are very time-consuming processes, and wastage is more. In this paper, coins of ultrathin sheets have been manufactured using wire electrical discharge machining (Wire-EDM). While machining, the effect of control parameters on the performance measures have also been studied. After experimentation, with the different combinations of the control variables, the sheet thickness has been found in the range of 47 μm to 154 μm. While machining, lower spark energy causes higher machining time, but the relatively better surface finish has been observed.

Research paper thumbnail of Proficiency of Electrical Discharge Machining in Fabrication of Microstructures

Research paper thumbnail of Performance analysis of an array of square micro-fins

IOP Conference Series: Materials Science and Engineering, 2018

Array of micro pin fin heat sinks shows higher thermal efficiency in high heat flux and critical ... more Array of micro pin fin heat sinks shows higher thermal efficiency in high heat flux and critical devices such as aerospace, microelectronic etc. In this work, an array of micro square pin fins has been designed and for this copper is selected as workpiece material. Moreover, a numerical investigation of thermal performances and mechanical behavior of the designed fins has been carried out. The effects of Reynolds numbers on velocity profile and heat transfer performance have also been studied. Additionally, the equivalent (von-Mises) stress along with the structural and total deformations have been observed at the desired pressure applied on the surface of the pin fins. Numerical simulations with similar parametric conditions have also been conducted on a plate having the same dimensions without fins, and a comparison has been made with a plate having micro-fins. It has been observed that the array of square micro pin fins gives a better thermal performance than that of without fins.

Research paper thumbnail of Machinability study of 430 stainless steel using tap water in EDM

Materials Today: Proceedings, 2020

Abstract The present paper studies the variation of response measures with the variation in the i... more Abstract The present paper studies the variation of response measures with the variation in the input parameters during electric discharge machining (EDM) of 430 stainless steel using brass tool. The dielectric medium used in this study is tap water. Various types of toxic gases are evolved due to the use of conventional hydrocarbon oil in EDM. To reduce these toxic emissions and make the process sustainable, tap water is used as an alternative of hydrocarbon oil. The trend of variation of the response measures is investigated with the changes occurred in the input variables. MRR and TWR increase with increase in current. Whereas, MRR increases and TWR decreases with increase in pulse-on time. Surface roughness increases with increase in current and pulse-on time. Micrographs are studied to understand the surface texture of the workpiece. ANOVA is performed to know the percentage contribution of the variable parameters on the output performance measures.

Research paper thumbnail of Machinability assessment of titanium grade 2 alloy using deionized water in EDM

Materials Today: Proceedings, 2020

This paper aims to investigate the effect of input process parameters on the output parameters du... more This paper aims to investigate the effect of input process parameters on the output parameters during electrical discharge machining (EDM) of titanium grade 2 alloy. The electrode material and the dielectric fluid used in this experimental study are copper and deionized water respectively. Effect of current and pulse-on time on material removal rate, tool wear rate and surface roughness have been studied. Various types of toxic gases are evolved due to the use of conventional hydrocarbon oil in EDM. To reduce these toxic emissions and make the process sustainable, deionized water is used as an alternative of hydrocarbon oil. The trend of variation of the response measures is investigated with the changes occurred in the input variables. MRR and TWR increase with increase in current. Whereas, MRR increases and TWR decreases with increase in pulse-on time. Surface roughness increases with increase in current and pulse-on time. Micrographs are studied to understand the surface texture of the workpiece. ANOVA is performed to know the percentage contribution of the variable parameters on the output performance measures.

Research paper thumbnail of A comparative assessment of micro drilling in boron carbide using ultrasonic machining

Materials and Manufacturing Processes, 2019

In the present work, machining of boron carbide (B 4 C) has been performed using ultrasonic machi... more In the present work, machining of boron carbide (B 4 C) has been performed using ultrasonic machining (USM) with the same material as abrasive particles. A comparative assessment of machining of B 4 C with that of glass and brass has also been carried out by drilling microholes using USM. The experimentation has been conducted according to Taguchi L9 orthogonal array. The effect of feed rate, slurry concentration, and grit size has been evaluated on the performance measures such as material removal rate, overcut, circularity error, taper angle and tool wear rate. Additionally, overall evaluation criteria (OEC) has been formulated to evaluate the combined performance measures. After ANOVA feed rate became the most significant parameters affecting OEC for all the materials. The machining of B 4 C has been found to be possible but lacks in the machining rate in comparison with that of glass and brass. Least tool wear rate has been found in case of glass whereas minimum overcut, circularity error and taper angle have been observed for brass. The quality of the drilled holes in B 4 C is better as minimal surface chipping and burr formation has been observed.

Research paper thumbnail of Etching characteristics of aluminium while machining square cavity using photochemical machining

AIP Conference Proceedings, 2018

Photochemical machining (PCM) is one of the well-known non-traditional machining processes that o... more Photochemical machining (PCM) is one of the well-known non-traditional machining processes that offer the challenges of today’s manufacturing world. In this demanding world, PCM is useful for quick machining on any kind of material using suitable etchant. This work focuses on determining the etching characteristics of aluminium alloy (Al 6061) by PCM process using ferric chloride (FeCl3) as an etchant. Taguchi L9 orthogonal array is used to study the effect of process parameters like temperature, etching time and surface area to observe the effects on performance measures such as surface roughness and etching depth. An overall evaluation criterion (OEC) is formulated to optimize the etching characteristics which will yield in lower surface roughness and higher etching depth.Photochemical machining (PCM) is one of the well-known non-traditional machining processes that offer the challenges of today’s manufacturing world. In this demanding world, PCM is useful for quick machining on any kind of material using suitable etchant. This work focuses on determining the etching characteristics of aluminium alloy (Al 6061) by PCM process using ferric chloride (FeCl3) as an etchant. Taguchi L9 orthogonal array is used to study the effect of process parameters like temperature, etching time and surface area to observe the effects on performance measures such as surface roughness and etching depth. An overall evaluation criterion (OEC) is formulated to optimize the etching characteristics which will yield in lower surface roughness and higher etching depth.

Research paper thumbnail of Machinability study on German silver using wire-EDM

AIP Conference Proceedings, 2018

Research paper thumbnail of Concept development for fabricating threaded micro-pin using wire-EDM

Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2019

Nowadays miniaturization with precision is an important requirement in the field of medical devic... more Nowadays miniaturization with precision is an important requirement in the field of medical devices and high-end applications. This work introduces the concept of 3D complex geometry fabrication in microscale using typical 2-Axis wire-cut electric discharge machine (WEDM). In this regard, the threaded profile micro-pin has been chosen in the present study. Synchronizing the workpiece rotating speed with feed rate along with a suitable depth of cut is the required condition for fabricating a screw. A separate attachment has been developed and used to rotate the workpiece at different speeds. Further, a CNC code has been generated to design the tool path with the required tool feed and depth of cut. Initially, turning operation has been performed which results in reduction in the tool diameter into the desired dimension along with the elimination of the eccentricity of the rotating rod. Consequently, the thread cutting operation has been accomplished with the adjusted set of parameters. Besides, the surface topography and material characteristics of the fabricated screw fin have also been observed based on scanning electron microscopic images and energy-dispersive X-ray analysis. Finally, the established process has been escalated further to fabricate screws of minimum possible dimension using the WEDM.

Research paper thumbnail of Fabrication of an array of micro-fins using Wire-EDM and its parametric analysis

Materials and Manufacturing Processes, 2019

The fabrication of micro-fin is very critical due to its higher debility nature. In this paper, a... more The fabrication of micro-fin is very critical due to its higher debility nature. In this paper, a simple methodology is proposed for fabricating an array of micro-fins using 2-Axis wire electric discharge machining process, which gives a faster production rate with good accuracy. Arrays of 625 (25 × 25) micro-fins have been fabricated on stainless steel and copper square rods. The average height of the fabricated fins is 850 µm. The effects of process parameters such as pulse-on-time, pulse-off-time, current, and table feed on performance measures like material removal rate, overcut, and cutting rate have been studied. Taguchi L 16 orthogonal array has been employed to conduct the experimentation. Analysis of variance (ANOVA) has been applied to observe the significant process parameters and their contribution to the responses. Moreover, the overall evaluation criteria (OEC) have also been formulated to obtain the best parametric combination. The characterization of fabricated micro-pin-fins has been carried out using scanning electron microscope and energy dispersive X-ray techniques.

Research paper thumbnail of An Approach to Maximize Weld Penetration During TIG Welding of P91 Steel Plates by Utilizing Image Processing and Taguchi Orthogonal Array

Journal of The Institution of Engineers (India): Series C, 2016

P-91 is modified 9Cr-1Mo steel. Fabricated structures and components of P-91 has a lot of applica... more P-91 is modified 9Cr-1Mo steel. Fabricated structures and components of P-91 has a lot of application in power and chemical industry owing to its excellent properties like high temperature stress corrosion resistance, less susceptibility to thermal fatigue at high operating temperatures. The weld quality and surface finish of fabricated structure of P91 is very good when welded by Tungsten Inert Gas welding (TIG). However, the process has its limitation regarding weld penetration. The success of a welding process lies in fabricating with such a combination of parameters that gives maximum weld penetration and minimum weld width. To carry out an investigation on the effect of the autogenous TIG welding parameters on weld penetration and weld width, bead-on-plate welds were carried on P91 plates of thickness 6 mm in accordance to a Taguchi L9 design. Welding current, welding speed and gas flow rate were the three control variables in the investigation. After autogenous (TIG) welding, the dimension of the weld width, weld penetration and weld area were successfully measured by an image analysis technique developed for the study. The maximum error for the measured dimensions of the weld width, penetration and area with the developed image analysis technique was only 2 % compared to the measurements of Leica-Q-Win-V3 software installed in optical microscope. The measurements with the developed software, unlike the measurements under a microscope, required least human intervention. An Analysis of Variance (ANOVA) confirms the significance of the selected parameters. Thereafter, Taguchi's method was successfully used to trade-off between maximum penetration and minimum weld width while keeping the weld area at a minimum.

Research paper thumbnail of Synthesis and properties of mullite-type (Bi1−xSrx)2(M11−yM2y)4O9−x (M=Al, Ga, Fe)

Journal of the European Ceramic Society, 2011

ABSTRACT Mullite-type A2M4O9 phases (M = Al, Ga, Fe), representing promising oxygen conducting ma... more ABSTRACT Mullite-type A2M4O9 phases (M = Al, Ga, Fe), representing promising oxygen conducting materials for solid oxide fuel cells (SOFCs), were synthesized using the glycerine- and the EDTA/citric acid synthesis method. For strontium-doped material pure phases could be obtained only by washing the samples after the heating in both synthesis methods. Temperature dependent investigations were carried out to show the influence of the metal atoms on the structural stability and thermal expansion coefficients. Whereas the Sr-free phases show a quasi linear thermal expansion behavior in all three directions up to their incongruent melting points, a discontinuity in the measured range is observed for the investigated strontium doped dibismuth-nonaoxotetrametallate(III) caused by the decomposition into Bi2M4O9, strontium metallates and bismuthoxide. Big single crystals were only observed for the Sr-free compound, of which the structure of Bi2(Ga0.45Fe0.55)4O9 will be presented here in the Bärnighausen tree corresponding mullite-type setting.

Research paper thumbnail of Synthesis and characterization of niobium doped hexagonal tungsten bronze in the systems, CsxNbyW1−yO3

Journal of Materials Science, 2010

ABSTRACT Well crystallized niobium-doped TiO2 nanotube arrays (TiNbO-NT) were successfully synthe... more ABSTRACT Well crystallized niobium-doped TiO2 nanotube arrays (TiNbO-NT) were successfully synthesized via the anodization of titanium/niobium alloy sheets, followed with a heat treatment at 550 °C for 2 h. Morphology analysis results demonstrated that both the titanium/niobium alloy microstructure and the dissolution strength of electrolyte played major roles in the formation of nanotube structure. A single-phase microstructure was more favorable to the formation of uniform nanotube arrays, while modulating the dissolution strength of electrolyte was required to obtain nanotube arrays from the alloys with multi-phase microstructures. X-ray diffraction (XRD) and X-ray photoelectron (XPS) analysis results clearly demonstrated that niobium dopants (Nb5+) were successfully doped into TiO2 anatase lattice by substituting Ti4+ in this approach.

Research paper thumbnail of The Effects of Oxidation States and Spin States of Chromium Interaction with <i>Sargassum Sp</i>.: A Spectroscopic and Density Functional Theoretical Study

Green and Sustainable Chemistry, 2021

The study of various oxidation states of chromium with Sargassum sp. is of particular interest si... more The study of various oxidation states of chromium with Sargassum sp. is of particular interest since hexavalent chromium is reduced to trivalent chromium in an aqueous solution. In this study, a systematic density functional theory (DFT) calculations were performed to study the interactions of transition metal chromium ion with different oxidation states and spin states with the Sargassum sp. decorated with carboxylate (acetate) at the wB97XD/6-311++ G(d,p) level of theory. The structures and binding energies of chromium metal-carboxylate complexes at various oxidation states and spin states in gas phase were examined. The coordination strength of Cr(VI) with the acetate ligand was predominantly the strongest compared to the other oxidation states. Vibrational frequency analysis, for the homoleptic monomers of tris [Cr III (AC) 3 ] 0 and [Cr VI (AC) 3 ] 3+ complexes, illustrate good harmony with the experimental and theoretical calculated frequencies. Using the time-dependent DFT (TD-DFT) at the level of CAM-B3LYP/6-311++G(d,p), the vertical excitation energies were obtained. The stabilization energies derived using the second order perturbation theory, E ij (2) , of NBO analysis confirmed the greater charge transfer for the observed trends in the metal binding. The calculated binding energies (ΔE) and interactions energies ΣE ij (2) favor the formation of [Cr VI (AC) 3 ] 3+ complexes. The findings of this study identify efficient electronic factors as major contributors to the metal binding affinities, with promising possibilities for the design of metal-ligand complexes and sensing of the metal ions.

Research paper thumbnail of Structure, chemical composition and optical property relationship of alkali-metal tungsten oxides and niobium tungsten oxides

The relationship between chemical composition, structure and optical property in alkali metal tun... more The relationship between chemical composition, structure and optical property in alkali metal tungsten oxides (tungsten bronzes) and niobium tungsten oxides (block type compounds) was investigated using X-ray powder diffraction, optical microscopy, microprobe analysis, Raman and optical spectroscopic techniques. Substitution experiments of nominal compositions Na 0.8 Nb y W 1-y O 3 (y = 0.0-0.4) show a single phase cubic perovskite tungsten bronze (PTB c) type structure up to y = 0.07. Further increase in Nb content show an additional PTB c type phase up to y = 0.2. For nominal compositions y > 0.2 even a separation into three distinct colored crystallites with cubic perovskite type structure is obtained: (i) red-orange Na x WO 3 crystallites with slightly decreasing x (i.e. 0.8 to 0.72) with increasing nominal y, (ii) bluish crystallites of variable compositions Na x Nb y W 1-y O 3, and (iii) white crystallites of a new phase with composition Na 0.5 NbO 2.75. Substitution experiments of nominal compositions K 0.55 Nb y W 1-y O 3 show up to y = 0.07 tetragonal tungsten bronze (TTB) type single phase. Samples with nominal niobium content y > 0.07 show an additional cubic pyrochlore type phase. Na x WO 3 samples reveal coexisting phases of cubic perovskite tungsten bronze (PTB c), tetragonal tungsten bronze (TTB), and tetragonal perovskite tungsten bronze (PTB t) in the range of 0.15 ≤ x ≤ 0.4, which has been quantified. Pure PTB t and orthorhombic perovskite tungsten bronze (PTB o) appear for x = 0.1, and 0.05, respectively. Structural studies for single phase PTB c Na x WO 3 show that all compositions in the range of 0.4 < x < 0.9 can uniquely be refined using space group Im-3. The linear increase in lattice parameters with increasing x in PTB c Na x WO 3 is explained by increasing W-O bond length, suggesting an x independent tilt of about 3° of the WO 6 octahedra. For the PTB t phase it is shown that the puckering effect, i.e. the off centering of W along c-axis, is insufficient to explain the structure. Additionally the WO 6 octahedra show a tilt around the c axis, which is consistent with space group P4/ncc. The optical properties of the metallic compositions of the systems Li x WO

Research paper thumbnail of New series of vanadium-doped hexagonal tungsten bronze, Mx W1−y V y O3

Acta Crystallographica Section A Foundations and Advances, Dec 1, 2017

Attempts were taken to synthesize vanadium doped rubidium and cesium hexagonal tungsten bronze sa... more Attempts were taken to synthesize vanadium doped rubidium and cesium hexagonal tungsten bronze samples with nominal composition MxW1-yVyO3 (x =0.30, 0.25 and 0.0 ≤ y ≤ x). The samples were synthesized by solid state synthesis method at 700˚C in an evacuated silica glass tube. X-ray diffraction data of MxW1-yVyO3 reveal that pure hexagonal tungsten bronze (HTB) phase could be formed up to y = 0.18 and y = 0.15 for x = 0.30 and x = 0.25 series, respectively revealing 60% of replacement of W5+ by V5+. Rietveld structure refinement of XRD data also reveal the systematic incorporation of vanadium in the HTB lattice and shortening of the V/W-O bond distances within the xy plane and elongation in the crystallographic c direction. FTIR absorption spectra of the oxidized phases also support the XRD results. Moreover, there develop an absorption feature as a function of y and shows a significant increase of its intensity with gradual replacement of W5+ by V5+, indicating a significant decrease in the metallic like contribution and reveals nonmetallic nature of the compounds. Elemental analysis show excellent agreement with their nominal ones indicating that a systematic incorporation of vanadium in MxW1-yVyO3 system.

Research paper thumbnail of Oxygen Diffusion in Bi2M4O9 (M = Al, Ga, Fe) Systems and the Effect of Sr Doping in Bi2-2xSr2xM4O9-x Studied by Isotope Exchange Experiments and IR Absorption

Ceramic Engineering and Science Proceedings, 2010

ABSTRACT Compounds Bi2-2xSr2XM409.x (M = Al, Ga, Fe) possessing mullite type structure could be i... more ABSTRACT Compounds Bi2-2xSr2XM409.x (M = Al, Ga, Fe) possessing mullite type structure could be interesting candidates for the use as electrolytes in SOFCs at intermediate temperatures (600-800°C). A central role for enhanced oxygen diffusion could be related to the vacancy ...

Research paper thumbnail of Machinability Study of Rubber using USM for Microdrilling

Research paper thumbnail of Selective Etching of Aluminium 6068 Using Photochemical Machining

Research paper thumbnail of Synthesis and Characterization in the New System BI2(AL/GA)4O9 and 18O/16O Exchange Experiments

ABSTRACT Compositions in the new system BÍ2(GaxAli.x)409 (x = 0, 0.1, ...., 1) having mullite-typ... more ABSTRACT Compositions in the new system BÍ2(GaxAli.x)409 (x = 0, 0.1, ...., 1) having mullite-type structure were synthesized using precursor gels obtained from the solution of corresponding nitrates in glycerin. The effects of Ga/Al substitution were characterized by IR absorption ...

Research paper thumbnail of Fabrication of Ultrathin Sheet Using Wire-EDM

Techno-Societal 2018, 2019

Generally, sheet products (coins, gears, washers etc.) are fabricated using blanking and punching... more Generally, sheet products (coins, gears, washers etc.) are fabricated using blanking and punching operations. These are very time-consuming processes, and wastage is more. In this paper, coins of ultrathin sheets have been manufactured using wire electrical discharge machining (Wire-EDM). While machining, the effect of control parameters on the performance measures have also been studied. After experimentation, with the different combinations of the control variables, the sheet thickness has been found in the range of 47 μm to 154 μm. While machining, lower spark energy causes higher machining time, but the relatively better surface finish has been observed.

Research paper thumbnail of Proficiency of Electrical Discharge Machining in Fabrication of Microstructures

Research paper thumbnail of Performance analysis of an array of square micro-fins

IOP Conference Series: Materials Science and Engineering, 2018

Array of micro pin fin heat sinks shows higher thermal efficiency in high heat flux and critical ... more Array of micro pin fin heat sinks shows higher thermal efficiency in high heat flux and critical devices such as aerospace, microelectronic etc. In this work, an array of micro square pin fins has been designed and for this copper is selected as workpiece material. Moreover, a numerical investigation of thermal performances and mechanical behavior of the designed fins has been carried out. The effects of Reynolds numbers on velocity profile and heat transfer performance have also been studied. Additionally, the equivalent (von-Mises) stress along with the structural and total deformations have been observed at the desired pressure applied on the surface of the pin fins. Numerical simulations with similar parametric conditions have also been conducted on a plate having the same dimensions without fins, and a comparison has been made with a plate having micro-fins. It has been observed that the array of square micro pin fins gives a better thermal performance than that of without fins.

Research paper thumbnail of Machinability study of 430 stainless steel using tap water in EDM

Materials Today: Proceedings, 2020

Abstract The present paper studies the variation of response measures with the variation in the i... more Abstract The present paper studies the variation of response measures with the variation in the input parameters during electric discharge machining (EDM) of 430 stainless steel using brass tool. The dielectric medium used in this study is tap water. Various types of toxic gases are evolved due to the use of conventional hydrocarbon oil in EDM. To reduce these toxic emissions and make the process sustainable, tap water is used as an alternative of hydrocarbon oil. The trend of variation of the response measures is investigated with the changes occurred in the input variables. MRR and TWR increase with increase in current. Whereas, MRR increases and TWR decreases with increase in pulse-on time. Surface roughness increases with increase in current and pulse-on time. Micrographs are studied to understand the surface texture of the workpiece. ANOVA is performed to know the percentage contribution of the variable parameters on the output performance measures.

Research paper thumbnail of Machinability assessment of titanium grade 2 alloy using deionized water in EDM

Materials Today: Proceedings, 2020

This paper aims to investigate the effect of input process parameters on the output parameters du... more This paper aims to investigate the effect of input process parameters on the output parameters during electrical discharge machining (EDM) of titanium grade 2 alloy. The electrode material and the dielectric fluid used in this experimental study are copper and deionized water respectively. Effect of current and pulse-on time on material removal rate, tool wear rate and surface roughness have been studied. Various types of toxic gases are evolved due to the use of conventional hydrocarbon oil in EDM. To reduce these toxic emissions and make the process sustainable, deionized water is used as an alternative of hydrocarbon oil. The trend of variation of the response measures is investigated with the changes occurred in the input variables. MRR and TWR increase with increase in current. Whereas, MRR increases and TWR decreases with increase in pulse-on time. Surface roughness increases with increase in current and pulse-on time. Micrographs are studied to understand the surface texture of the workpiece. ANOVA is performed to know the percentage contribution of the variable parameters on the output performance measures.

Research paper thumbnail of A comparative assessment of micro drilling in boron carbide using ultrasonic machining

Materials and Manufacturing Processes, 2019

In the present work, machining of boron carbide (B 4 C) has been performed using ultrasonic machi... more In the present work, machining of boron carbide (B 4 C) has been performed using ultrasonic machining (USM) with the same material as abrasive particles. A comparative assessment of machining of B 4 C with that of glass and brass has also been carried out by drilling microholes using USM. The experimentation has been conducted according to Taguchi L9 orthogonal array. The effect of feed rate, slurry concentration, and grit size has been evaluated on the performance measures such as material removal rate, overcut, circularity error, taper angle and tool wear rate. Additionally, overall evaluation criteria (OEC) has been formulated to evaluate the combined performance measures. After ANOVA feed rate became the most significant parameters affecting OEC for all the materials. The machining of B 4 C has been found to be possible but lacks in the machining rate in comparison with that of glass and brass. Least tool wear rate has been found in case of glass whereas minimum overcut, circularity error and taper angle have been observed for brass. The quality of the drilled holes in B 4 C is better as minimal surface chipping and burr formation has been observed.

Research paper thumbnail of Etching characteristics of aluminium while machining square cavity using photochemical machining

AIP Conference Proceedings, 2018

Photochemical machining (PCM) is one of the well-known non-traditional machining processes that o... more Photochemical machining (PCM) is one of the well-known non-traditional machining processes that offer the challenges of today’s manufacturing world. In this demanding world, PCM is useful for quick machining on any kind of material using suitable etchant. This work focuses on determining the etching characteristics of aluminium alloy (Al 6061) by PCM process using ferric chloride (FeCl3) as an etchant. Taguchi L9 orthogonal array is used to study the effect of process parameters like temperature, etching time and surface area to observe the effects on performance measures such as surface roughness and etching depth. An overall evaluation criterion (OEC) is formulated to optimize the etching characteristics which will yield in lower surface roughness and higher etching depth.Photochemical machining (PCM) is one of the well-known non-traditional machining processes that offer the challenges of today’s manufacturing world. In this demanding world, PCM is useful for quick machining on any kind of material using suitable etchant. This work focuses on determining the etching characteristics of aluminium alloy (Al 6061) by PCM process using ferric chloride (FeCl3) as an etchant. Taguchi L9 orthogonal array is used to study the effect of process parameters like temperature, etching time and surface area to observe the effects on performance measures such as surface roughness and etching depth. An overall evaluation criterion (OEC) is formulated to optimize the etching characteristics which will yield in lower surface roughness and higher etching depth.

Research paper thumbnail of Machinability study on German silver using wire-EDM

AIP Conference Proceedings, 2018

Research paper thumbnail of Concept development for fabricating threaded micro-pin using wire-EDM

Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2019

Nowadays miniaturization with precision is an important requirement in the field of medical devic... more Nowadays miniaturization with precision is an important requirement in the field of medical devices and high-end applications. This work introduces the concept of 3D complex geometry fabrication in microscale using typical 2-Axis wire-cut electric discharge machine (WEDM). In this regard, the threaded profile micro-pin has been chosen in the present study. Synchronizing the workpiece rotating speed with feed rate along with a suitable depth of cut is the required condition for fabricating a screw. A separate attachment has been developed and used to rotate the workpiece at different speeds. Further, a CNC code has been generated to design the tool path with the required tool feed and depth of cut. Initially, turning operation has been performed which results in reduction in the tool diameter into the desired dimension along with the elimination of the eccentricity of the rotating rod. Consequently, the thread cutting operation has been accomplished with the adjusted set of parameters. Besides, the surface topography and material characteristics of the fabricated screw fin have also been observed based on scanning electron microscopic images and energy-dispersive X-ray analysis. Finally, the established process has been escalated further to fabricate screws of minimum possible dimension using the WEDM.

Research paper thumbnail of Fabrication of an array of micro-fins using Wire-EDM and its parametric analysis

Materials and Manufacturing Processes, 2019

The fabrication of micro-fin is very critical due to its higher debility nature. In this paper, a... more The fabrication of micro-fin is very critical due to its higher debility nature. In this paper, a simple methodology is proposed for fabricating an array of micro-fins using 2-Axis wire electric discharge machining process, which gives a faster production rate with good accuracy. Arrays of 625 (25 × 25) micro-fins have been fabricated on stainless steel and copper square rods. The average height of the fabricated fins is 850 µm. The effects of process parameters such as pulse-on-time, pulse-off-time, current, and table feed on performance measures like material removal rate, overcut, and cutting rate have been studied. Taguchi L 16 orthogonal array has been employed to conduct the experimentation. Analysis of variance (ANOVA) has been applied to observe the significant process parameters and their contribution to the responses. Moreover, the overall evaluation criteria (OEC) have also been formulated to obtain the best parametric combination. The characterization of fabricated micro-pin-fins has been carried out using scanning electron microscope and energy dispersive X-ray techniques.

Research paper thumbnail of An Approach to Maximize Weld Penetration During TIG Welding of P91 Steel Plates by Utilizing Image Processing and Taguchi Orthogonal Array

Journal of The Institution of Engineers (India): Series C, 2016

P-91 is modified 9Cr-1Mo steel. Fabricated structures and components of P-91 has a lot of applica... more P-91 is modified 9Cr-1Mo steel. Fabricated structures and components of P-91 has a lot of application in power and chemical industry owing to its excellent properties like high temperature stress corrosion resistance, less susceptibility to thermal fatigue at high operating temperatures. The weld quality and surface finish of fabricated structure of P91 is very good when welded by Tungsten Inert Gas welding (TIG). However, the process has its limitation regarding weld penetration. The success of a welding process lies in fabricating with such a combination of parameters that gives maximum weld penetration and minimum weld width. To carry out an investigation on the effect of the autogenous TIG welding parameters on weld penetration and weld width, bead-on-plate welds were carried on P91 plates of thickness 6 mm in accordance to a Taguchi L9 design. Welding current, welding speed and gas flow rate were the three control variables in the investigation. After autogenous (TIG) welding, the dimension of the weld width, weld penetration and weld area were successfully measured by an image analysis technique developed for the study. The maximum error for the measured dimensions of the weld width, penetration and area with the developed image analysis technique was only 2 % compared to the measurements of Leica-Q-Win-V3 software installed in optical microscope. The measurements with the developed software, unlike the measurements under a microscope, required least human intervention. An Analysis of Variance (ANOVA) confirms the significance of the selected parameters. Thereafter, Taguchi's method was successfully used to trade-off between maximum penetration and minimum weld width while keeping the weld area at a minimum.

Research paper thumbnail of Synthesis and properties of mullite-type (Bi1−xSrx)2(M11−yM2y)4O9−x (M=Al, Ga, Fe)

Journal of the European Ceramic Society, 2011

ABSTRACT Mullite-type A2M4O9 phases (M = Al, Ga, Fe), representing promising oxygen conducting ma... more ABSTRACT Mullite-type A2M4O9 phases (M = Al, Ga, Fe), representing promising oxygen conducting materials for solid oxide fuel cells (SOFCs), were synthesized using the glycerine- and the EDTA/citric acid synthesis method. For strontium-doped material pure phases could be obtained only by washing the samples after the heating in both synthesis methods. Temperature dependent investigations were carried out to show the influence of the metal atoms on the structural stability and thermal expansion coefficients. Whereas the Sr-free phases show a quasi linear thermal expansion behavior in all three directions up to their incongruent melting points, a discontinuity in the measured range is observed for the investigated strontium doped dibismuth-nonaoxotetrametallate(III) caused by the decomposition into Bi2M4O9, strontium metallates and bismuthoxide. Big single crystals were only observed for the Sr-free compound, of which the structure of Bi2(Ga0.45Fe0.55)4O9 will be presented here in the Bärnighausen tree corresponding mullite-type setting.

Research paper thumbnail of Synthesis and characterization of niobium doped hexagonal tungsten bronze in the systems, CsxNbyW1−yO3

Journal of Materials Science, 2010

ABSTRACT Well crystallized niobium-doped TiO2 nanotube arrays (TiNbO-NT) were successfully synthe... more ABSTRACT Well crystallized niobium-doped TiO2 nanotube arrays (TiNbO-NT) were successfully synthesized via the anodization of titanium/niobium alloy sheets, followed with a heat treatment at 550 °C for 2 h. Morphology analysis results demonstrated that both the titanium/niobium alloy microstructure and the dissolution strength of electrolyte played major roles in the formation of nanotube structure. A single-phase microstructure was more favorable to the formation of uniform nanotube arrays, while modulating the dissolution strength of electrolyte was required to obtain nanotube arrays from the alloys with multi-phase microstructures. X-ray diffraction (XRD) and X-ray photoelectron (XPS) analysis results clearly demonstrated that niobium dopants (Nb5+) were successfully doped into TiO2 anatase lattice by substituting Ti4+ in this approach.

Research paper thumbnail of The Effects of Oxidation States and Spin States of Chromium Interaction with <i>Sargassum Sp</i>.: A Spectroscopic and Density Functional Theoretical Study

Green and Sustainable Chemistry, 2021

The study of various oxidation states of chromium with Sargassum sp. is of particular interest si... more The study of various oxidation states of chromium with Sargassum sp. is of particular interest since hexavalent chromium is reduced to trivalent chromium in an aqueous solution. In this study, a systematic density functional theory (DFT) calculations were performed to study the interactions of transition metal chromium ion with different oxidation states and spin states with the Sargassum sp. decorated with carboxylate (acetate) at the wB97XD/6-311++ G(d,p) level of theory. The structures and binding energies of chromium metal-carboxylate complexes at various oxidation states and spin states in gas phase were examined. The coordination strength of Cr(VI) with the acetate ligand was predominantly the strongest compared to the other oxidation states. Vibrational frequency analysis, for the homoleptic monomers of tris [Cr III (AC) 3 ] 0 and [Cr VI (AC) 3 ] 3+ complexes, illustrate good harmony with the experimental and theoretical calculated frequencies. Using the time-dependent DFT (TD-DFT) at the level of CAM-B3LYP/6-311++G(d,p), the vertical excitation energies were obtained. The stabilization energies derived using the second order perturbation theory, E ij (2) , of NBO analysis confirmed the greater charge transfer for the observed trends in the metal binding. The calculated binding energies (ΔE) and interactions energies ΣE ij (2) favor the formation of [Cr VI (AC) 3 ] 3+ complexes. The findings of this study identify efficient electronic factors as major contributors to the metal binding affinities, with promising possibilities for the design of metal-ligand complexes and sensing of the metal ions.

Research paper thumbnail of Structure, chemical composition and optical property relationship of alkali-metal tungsten oxides and niobium tungsten oxides

The relationship between chemical composition, structure and optical property in alkali metal tun... more The relationship between chemical composition, structure and optical property in alkali metal tungsten oxides (tungsten bronzes) and niobium tungsten oxides (block type compounds) was investigated using X-ray powder diffraction, optical microscopy, microprobe analysis, Raman and optical spectroscopic techniques. Substitution experiments of nominal compositions Na 0.8 Nb y W 1-y O 3 (y = 0.0-0.4) show a single phase cubic perovskite tungsten bronze (PTB c) type structure up to y = 0.07. Further increase in Nb content show an additional PTB c type phase up to y = 0.2. For nominal compositions y > 0.2 even a separation into three distinct colored crystallites with cubic perovskite type structure is obtained: (i) red-orange Na x WO 3 crystallites with slightly decreasing x (i.e. 0.8 to 0.72) with increasing nominal y, (ii) bluish crystallites of variable compositions Na x Nb y W 1-y O 3, and (iii) white crystallites of a new phase with composition Na 0.5 NbO 2.75. Substitution experiments of nominal compositions K 0.55 Nb y W 1-y O 3 show up to y = 0.07 tetragonal tungsten bronze (TTB) type single phase. Samples with nominal niobium content y > 0.07 show an additional cubic pyrochlore type phase. Na x WO 3 samples reveal coexisting phases of cubic perovskite tungsten bronze (PTB c), tetragonal tungsten bronze (TTB), and tetragonal perovskite tungsten bronze (PTB t) in the range of 0.15 ≤ x ≤ 0.4, which has been quantified. Pure PTB t and orthorhombic perovskite tungsten bronze (PTB o) appear for x = 0.1, and 0.05, respectively. Structural studies for single phase PTB c Na x WO 3 show that all compositions in the range of 0.4 < x < 0.9 can uniquely be refined using space group Im-3. The linear increase in lattice parameters with increasing x in PTB c Na x WO 3 is explained by increasing W-O bond length, suggesting an x independent tilt of about 3° of the WO 6 octahedra. For the PTB t phase it is shown that the puckering effect, i.e. the off centering of W along c-axis, is insufficient to explain the structure. Additionally the WO 6 octahedra show a tilt around the c axis, which is consistent with space group P4/ncc. The optical properties of the metallic compositions of the systems Li x WO

Research paper thumbnail of New series of vanadium-doped hexagonal tungsten bronze, Mx W1−y V y O3

Acta Crystallographica Section A Foundations and Advances, Dec 1, 2017

Attempts were taken to synthesize vanadium doped rubidium and cesium hexagonal tungsten bronze sa... more Attempts were taken to synthesize vanadium doped rubidium and cesium hexagonal tungsten bronze samples with nominal composition MxW1-yVyO3 (x =0.30, 0.25 and 0.0 ≤ y ≤ x). The samples were synthesized by solid state synthesis method at 700˚C in an evacuated silica glass tube. X-ray diffraction data of MxW1-yVyO3 reveal that pure hexagonal tungsten bronze (HTB) phase could be formed up to y = 0.18 and y = 0.15 for x = 0.30 and x = 0.25 series, respectively revealing 60% of replacement of W5+ by V5+. Rietveld structure refinement of XRD data also reveal the systematic incorporation of vanadium in the HTB lattice and shortening of the V/W-O bond distances within the xy plane and elongation in the crystallographic c direction. FTIR absorption spectra of the oxidized phases also support the XRD results. Moreover, there develop an absorption feature as a function of y and shows a significant increase of its intensity with gradual replacement of W5+ by V5+, indicating a significant decrease in the metallic like contribution and reveals nonmetallic nature of the compounds. Elemental analysis show excellent agreement with their nominal ones indicating that a systematic incorporation of vanadium in MxW1-yVyO3 system.

Research paper thumbnail of Oxygen Diffusion in Bi2M4O9 (M = Al, Ga, Fe) Systems and the Effect of Sr Doping in Bi2-2xSr2xM4O9-x Studied by Isotope Exchange Experiments and IR Absorption

Ceramic Engineering and Science Proceedings, 2010

ABSTRACT Compounds Bi2-2xSr2XM409.x (M = Al, Ga, Fe) possessing mullite type structure could be i... more ABSTRACT Compounds Bi2-2xSr2XM409.x (M = Al, Ga, Fe) possessing mullite type structure could be interesting candidates for the use as electrolytes in SOFCs at intermediate temperatures (600-800°C). A central role for enhanced oxygen diffusion could be related to the vacancy ...