Metallurgical & Materials Engineering

Geometric shape function, f(a/W), is a correction factor that accounts for finite specimen size in calculation of stress intensity factor (SIF). Pin-loading tension method is suitable for fracture toughness testing of axially cracked thin-walled tubular specimens. But unique expression for f(a/W) of such specimens does not exist as it is sensitive to tube geometry. In this work, a generalized form of geometric shape function has been derived through a detailed finite element analysis and the outcome is validated with actual experimental results. Using the general shape function, SIF for any axially cracked thin-walled tube having dimensions within the range can be predicted.

This document is the author's post-print version, incorporating any revisions agreed during the peer-review process. Some differences between the published version and this version may remain and you are advised to consult the published version if you wish to cite from it.

In the present study, laser surface alloying of aluminium with WC+Co+NiCr (in the ratio of 70:15:15) has been conducted using a 5 kW continuous wave (CW) Nd:YAG laser (at a beam diameter of 0.003 m), with the output power ranging from 3-3.5 kW and scan speed from 0.012 m/s to 0.04 m/s by simultaneous feeding of precursor powder (at a flow rate of 1×10 -5 kg/s) and using He shroud at a gas flow rate of 3×10 -6 m 3 /s. The effect of laser power and scan speed on the characteristics (microstructures, phases and composition) and properties (wear and corrosion resistance) of the surface alloyed layer have been investigated in details. Laser surface alloying leads to development of fine grained aluminium with the dispersion of

The present study concerns studying the isothermal oxidation behavior of compositionally graded thermal barrier coating (TBC) consisting of 100% CoNiCrAlY as bond coat developed by high velocity oxyfuel (HVOF) spraying on Inconel 718 substrate followed by several layers of CoNiCrAlY and YSZ in the weight ratios of 70:30, 50:50, 30:70, and 0:100 by plasma spraying. The kinetics of growth of the thermally grown oxide (TGO) layer developed due to oxidation of compositionally graded TBC was compared to the same grown during oxidation of conventional duplex TBC. The mechanism of oxidation was established. The residual stress developed on the surface before and after oxidation was studied in details.

Different amounts of Co-doped TiO 2 powders and thin films were prepared by following a conventional co-precipitation and solegel dip coating technique, respectively. The synthesized powders and thin films were subjected to thermal treatments from 400 to 800 C and were thoroughly investigated by means of X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive analysis with X-rays, FT-infrared, FT-Raman, diffuse reflectance spectroscopy, ultravioletevisible spectroscopy, BET surface area, zeta potential, flat band potential measurements, band-gap energy, etc. The photocatalytic ability of the powders was evaluated by methylene blue (MB) degradation studies. The thin films were characterized by photocurrent and ultravioletevisible (UVeVis) spectroscopy techniques. The characterization results suggest that the Co-doped TiO 2 powders synthesized in this study consist mainly anatase phase, and possess reasonably high specific surface area, low band gap energy and flat band potentials amenable to water oxidation in photoelectrochemical (PEC) cells. The photocatalytic degradation of MB over Co-doped TiO 2 powders followed the LangmuireHinshelwood first order reaction rate relationship. The 0.1 wt.% Co-doped TiO 2 composition provided the higher photocurrent, n-type semi-conducting behavior and higher photocatalytic activity among various Co-doped TiO 2 compositions and pure TiO 2 investigated.

Different amounts of Ni-doped TiO 2 (Ni = 0.1 to 10%) powders and thin films were prepared by following a conventional coprecipitation and sol-gel dip coating techniques, respectively, at 400 to 800 • C, and were thoroughly characterized by means of XRD, FT-IR, FT-Raman, DRS, UV-visible, BET surface area, zeta potential, flat band potential, and photocurrent measurement techniques. Photocatalytic abilities of Ni-doped TiO 2 powders were evaluated by means of methylene blue (MB) degradation reaction under simulated solar light. Characterization results suggest that as a dopant, Ni stabilizes TiO 2 in the form of anatase phase, reduces its bandgap energy, and adjusts its flat band potentials such that this material can be employed for photoelectrochemical (PEC) oxidation of water reaction. The photocatalytic activity and photocurrent ability of TiO 2 have been enhanced by doping of Ni in TiO 2 . The kinetic studies revealed that the MB degradation reaction follows the Langmuir-Hinshelwood first-order reaction relationship.

Different amounts of Fe-doped TiO 2 (with 0.1 to 10 wt.% Fe) powders were prepared at temperatures in the range of 400 and 800 °C following a conventional co-precipitation technique and were thoroughly characterized by means of X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), Fourier-transform Raman (FT-Raman), diffuse reflectance spectroscopy (DRS), BET surface area, zeta potential and flat band potential measurements. Photocatalytic ability of Fe-doped TiO 2 powders was evaluated by means of methylene blue (MB) degradation experiments conducted under the irradiation of simulated solar light. Characterization results suggested that as a dopant Fe stabilized TiO 2 in the form of anatase phase, reduced its band gap energy and adjusted its flat band potentials in such a way that these powders can be employed for photoelectrolysis of water into hydrogen and oxygen in photoelectrochemical (PEC) cells. The 0.1 wt.% Fe-doped TiO 2 exhibited highest activity in the photocatalytic degradation of MB. The kinetic studies revealed that the MB degradation reaction follows the Langmuir-Hinshelwood first order reaction rate.

The Cu-doped TiO 2 (Cu = 0-50 wt.%) powders and thin films were prepared by following an homogeneous co-precipitation method and sol-gel dip coating technique, respectively, and were treated through 400° to 800°C, and then thoroughly investigated by following various characterization techniques. The characterization results suggest that the pure TiO 2 powder formed at 550°C is in rutile phase, whereas, the 0.1-10 wt.% Cu-doped TiO 2 powders formed at 550°C are mainly in anatase phase. These latter powders possess low bandgap energies (3.247-3.265 eV) and flat-band potentials amenable to water oxidation reaction. The 0.5 wt.% Cu-doped TiO 2 thin film formed at 550°C exhibited n-type semi-conducting behavior and considerable photocurrent among various investigated. The CO 2 reduction with a Faradaic efficiency of 82% and ~ 96% CO selectivity in a two-compartment electrochemical cell was noted at −2500 mV (vs. Ag/Ag + ) on pre-reduced (at −2000 mV vs. Ag/AgCl) 50 wt.% Cudoped TiO 2 thin film electrode in conjunction with an ionic liquid. The UV-light induced TiO 2 was found to be responsible for photocatalytic methylene blue (MB) degradation, and TiO 2 is not sensitized by MB. The in situ formed compounds of TiO 2 and CuO/Cu 2 O were found to absorb visible light but showed little visible light induced photocatalytic activity.

Nb-Si alloys have gained much attention over the last decade as the next generation alloys for high-temperature aero-engine applications due to their low density and improved mechanical properties. However, the microstructures of these alloys are quite complex and vary significantly with the addition of elements such as Ti and Hf. Hence, an improved understanding of the phase stability and the microstructural evolution of these alloys is essential for alloy design for advanced high-temperature applications. In the present paper, we describe the microstructural evolution modeling results of the dendritic and eutectic solidification of the binary Nb-16 at.% Si alloy, obtained using a Phase-Field simulations performed with MICRESS. The effect of parameters; such as heat extraction rate, the ratio of the diffusivity of the solute in liquid to solid, and the interfacial energy of liquid and solid interface, on the microstructural evolution during dendritic solidification is discussed in detail.

An in situ microbalance and infrared spectroscopic study of alternating exposures to Me2Au(S2CNEt2) and ozone illuminates the organometallic chemistry that allows for the thermal atomic layer deposition (ALD) of gold. In situ quartz crystal microbalance (QCM) studies resolve the nucleation delay and island growth of Au on a freshly prepared aluminum oxide surface with single cycle resolution, revealing inhibition for 40 cycles prior to slow nucleation and film coalescence that extends over 300 cycles. In situ infrared spectroscopy informed by first-principles computation provides insight into the surface chemistry of the self-limiting half-reactions, which are consistent with an oxidized Au surface mechanism. X-ray diffraction of ALD-grown gold on silicon, silica, sapphire, and mica reveals consistent out-of-plane oriented crystalline film growth as well as epitaxially directed in-plane orientation on closely lattice-matched mica at a relatively low growth temperature of 180 °C. A m...

Polyolefins comprise a major fraction of single-use plastics and yet their catalytic deconstruction/recycling has proven challenging due to their inert hydrocarbon connectivities. Here an electrophilic earth-abundant single-site organozirconium catalyst chemisorbed on a highly Brønsted acidic support and characterized by a broad array of experimental and theoretical techniques, is shown to mediate the rapid hydrogenolytic cleavage of molecular and macromolecular saturated hydrocarbons under mild conditions. For n-hexadecane, hydrogenolysis to light hydrocarbons proceeds with an activity of 690 mol n-hexadecane · mol Zr-1 · h-1 at 150°C/2.5 atm H2 pressure. Under similar solventless conditions, polyethylene, polyethylene-co- 1-octene, isotactic polypropylene, and a post-consumer sandwich bag are rapidly hydrogenolyzed to low molecular mass hydrocarbons via a turnover-limiting C-C scission pathway involving ßalkyl transfer rather than more common σ-bond metathesis.

X-ray standing wave (XSW) excited photoelectron emission was used to measure the site-specific valence band (VB) for 1/2 monolayer (ML) Pt grown on a SrTiO3 (001) surface. The XSW induced modulations in the core level (CL) and VB photoemission from the surface and substrate atoms were monitored for three hkl substrate Bragg reflections. The XSW CL analysis shows the Pt to have an fcc-like cube-on-cube epitaxy with the substrate. The XSW VB information compares well to a density functional theory calculated projected density of states from the surface and substrate atoms. Overall, this work represents a novel method for determining the contribution to the density of states by valence electrons from specific atomic surface sites.

X-ray standing wave (XSW) excited photoelectron emission was used to measure the site-specific valence band (VB) for ½ monolayer (ML) Pt grown on a SrTiO3 (001) surface. The XSW induced modulations in the core level (CL) and VB photoemission from the surface and substrate atoms were monitored for three hkl substrate Bragg reflections. The XSW CL analysis shows the Pt to have an fcc-like cube-on-cube epitaxy with the substrate. The XSW VB information compares well to a density functional theory calculated projected density of states from the surface and substrate atoms. Overall, this work represents a novel method for determining the contribution to the density of states by valence electrons from specific atomic surface sites.

Many attempts has been made to model performance parameters of EDM process using ANN. For modeling generally ANN architectures, learning/training algorithms and nos. of hidden neurons are varied to achieve minimum error, but the variation is made in random manner. So here a full factorial design has been implemented to achieve the optimal of above. From the ANOVA result the significance order also has been decided. After that optimal process modeling of MRR in EDM with the best of above
parameter has been performed

Electro chemical machining is a non conventional
machining process to machine conducting hard materials using
anodic dissolution. The process parameters are needed to be
optimized to get better result of material removal rate (MRR) and
surface roughness (SR). In this paper MRR and SR values are
optimized by Simulated Annealing (SA) and the effect of input
parameters are determined by Taguchi Design while machining
EN-19 tool steel.

Glass fibre reinforced plastics (GFRP) are having good weight to strength ratio, so they have wide range of application for
many purposes. Micro drilling of GFRP produces de-lamination in it. So it is always needed to optimize the process parameters
by minimizing thrust force and torque. The process parameters and response parameters values are used here for analysing and
optimizing the micro drilling of GFRP. The introduction of peck micro drilling in lieu of direct micro drilling was found to be
responsible for lower value of torque and thrust force. The optimized result of thrust force and torque was found to be 40000
and 5 of rpm and feed respectively for both direct and peck type of micro drilling.

Many attempts have been made to model and optimize performance parameters of Electrical Discharge Machining (EDM) process. In this investigation, the experimental design includes L9 orthogonal array based on the Taguchi methodology. The corresponding effect of input current, duty cycle and spark on time, on surface integrity, has been studied on AISI D2 tool steel. The residual stress measurement is done using X-ray diffraction method. The obtained output results regarding material removal rate, surface roughness, crack density, and residual stress have been modeled and optimized by regression equation and Genetic algorithm respectively. In this investigation, a metallurgical approach has been introduced towards the explanation of the resulted optimized response parameters.