Asokamani Rajamanickam

Dhanalakshmi College of Engineering · Research and Development

Scientific and technological developments have revolutionized the field of medicine, especially in the field of biomedicine which attempts to replace the diseased organs to enhance the longevity of the human. Though for many decades, surgeons, materials scientist, and Engineers opted for available materials such as polymers, metals, and ceramics fo...

This paper presents the wear characteristics of the composite ceramic coating made with Al2 O3 -40wt%8YSZ on the biomedical grade Ti-6Al-4V alloy (grade 5) used for total joint prosthetic components, with the aim of improving their tribological behavior. The coatings were deposited using a plasma spraying technique, and optimization of plasma param...

licenses/by-nc-nd/3.0/). Selection and peer review under responsibility of the Gokaraju Rangaraju Abstract This paper deals with the fabrication of WC-12wt%Co and Yttria-stabilized Zirconia coatings fabricated using Atmospheric Plasma Spraying technique.The Microstructural Characterization of the coatings was carried out using Scanning electron mic...

The relative wear resistance of three candidate coatings for titanium alloy-based orthopaedic applications was compared using a reciprocating test method. Micrometer-sized powders of the following compositions were plasma sprayed onto Ti-6Al-4V (TAV) alloy: (i) Al2O3 (AO) (ii) 8 mol% yttria stabilized Zirconia (8YSZ) and (iii) Al2O3-40 wt%8YSZ (A4Z...

The bio-corrosion response of ultrafine-grained commercially pure titanium processed by different routes of equal-channel angular pressing has been studied in simulated body fluid. The results indicate that the samples processed through route Bc that involved rotation of the workpiece by 90 deg in the same sense between each pass exhibited higher c...

This paper reports the wear characteristics of the ceramic coatings made with Al2O3 and also with SiC which were performed using atmospheric plasma spraying technique on the Ti-6Al-4V biomedical alloy with the aim of improving their tribological behavior. The wear behavior of the coatings was evaluated using reciprocatory wear tester with coated su...

This paper reports on the methodology adopted for obtaining near spherical agglomerated Al2O3 powders which enables them to be coated by plasma spray technique on titanium alloys. An attempt was made on spray drying alumina slurries with polyethylene glycol as binder and sodium hexametaphosphate as a dispersant. The effect of pH on the stability an...

This paper reports on the corrosion and scratch behavior of TiO2 + 50%HAp nanoceramic coated Ti–13Nb–13Zr orthopedic implant alloy. An adherent thin coating was obtained using the electrophoretic deposition (EPD) technique at 30 V and sintering at 850 °C. The microstructure of the coated surfaces was characterized by optical microscopy, AFM, and SE...

This paper reports on the corrosion and scratch behavior of TiO2 + 50%HAp nanoceramic coated Ti–13Nb–13Zr orthopedic implant alloy. An adherent thin coating was obtained using the electrophoretic deposition (EPD) technique at 30 V and sintering at 850 °C. The microstructure of the coated surfaces was characterized by optical microscopy, AFM, a...

We report investigations on the texture, corrosion and wear behavior of ultra-fine grained (UFG) Ti–13Nb–Zr alloy, processed by equal channel angular extrusion (ECAE) technique, for biomedical applications. The microstructure obtained was characterized by X-ray line profile analysis, scanning electron microscope (SEM) and electron back scattered di...

- We report investigations on the texture, corrosion and wear behavior of ultra-fine grained (UFG) Ti–13Nb–Zr alloy, processed by equal channel angular extrusion (ECAE) technique, for biomedical applications. The microstructure obtained was characterized by X-ray line profile analysis, scanning electron microscope (SEM) and electron back scattered...

We report here the synthesis and characterization of a new superconducting oxide LaBaCa2Cu3Oy. The Tc value of the compound is measured to be 25 K. XRD studies reveal that the compound possesses orthorhombic structure.

Synthesis of air-quenched high-Tc superconductors Y0.8Sr0.2Ba2Cu3O6+x and Y0.8Ba2.2Cu3O6+x exhibiting transition temperatures of 90 K and 88 K respectively and the variation of their electrical resistivity at high pressure are reported here. X-ray powder diffraction of the above systems reveal tetragonal structure.

The electronic structure calculations of the perovskite oxides SrCrO3 and PbCrO3 performed both in the paramagnetic and antiferromagnetic phases are reported here. The calculations were carried out using the Linear Muffin Tin Orbital method within the Atomic Sphere Approximation. The quantitative results obtained are found to give a good descriptio...

The effect of Ca2+ substitution for Y3+ in Y2Ba4Cu7O14+y on the superconducting properties and the high pressure electrical resistivity behavior of the system at ambient temperature were studied. The samples were obtained for x = 0.1, 0.2 and 0.5. The susceptibility measurements showed a maximum Tc for the concentration x = 0.1. The high pressure s...

The band structure calculations of perovskite transition metal compound LaRhO3 performed using 'tight binding linear muffin tin orbital' (TB-LMTO) method within local density approximation (LDA) under ambient and high pressures are reported here. Our calculations are able to successfully explain the insulating nature of the system and the insulator...

Biomedical Ti alloys are prone to undergo degradation due to the combined effect of wear and corrosion. To overcome these problems, surface modification techniques are being used. In this paper, the biomedical Ti alloy Ti–13Nb–13Zr was plasma sprayed with nanostructured Al2O3–13wt%TiO2, yttria stabilized zirconia powders and bilayer containing alte...

In the area of materials science, corrosion of biomaterials is of paramount importance as biomaterials are required for the survival of the human beings suffering from acute heart diseases, arthritis, osteoporosis and other joint complications. The present article discusses various issues associated with biological corrosion of different kinds of i...

The effects of laser nitriding on surface hardness, corrosion and wear behavior of the conventional biomedical implants such as commercially available pure titanium and Ti–13Nb–13Zr alloy is reported. The influence of alloying elements such as Zr and Nb on nitride formation was also studied by nitriding the newly developed alloy (Ti–13Nb–13Zr). The...

Inspite of superior mechanical properties such as low modulus of elasticity, high strength to weight ratio and excellent biocompatibility among the biomedical titanium alloys, it suffers from poor wear resistance. The objective of this work is to enhance the wear resistance of the newly developed beta titanium alloy, gum metal (Ti-23Nb-0. 7Ta-2Zr-1...

The field of biomaterials has become a vital area, as these materials can enhance the quality and longevity of human life and the science and technology associated with this field has now led to multi-million dollar business. The paper focuses its attention mainly on titanium-based alloys, even though there exists biomaterials made up of ceramics,...

C.P. Titanium and Ti-13Nb-13Zr alloys are widely used in biomedical applications as dental and orthopedic implants. However these materials are vulnerable to Surface corrosion. The aim of this investigation is to enhance the corrosion resistance of the above alloys through laser nitriding technique. Laser nitriding was performed using Nd: YAG laser...

This paper describes the effect of thermomechanical processing on microstrucural evolution of three alloys, namely Ti–13Nb–13Zr (T1), Ti–20Nb–13Zr (T2) and Ti–20Nb–20Zr (T3), with an objective to develop equiaxed microstructure in all three alloys by subjecting them to appropriate hot-rolling conditions. The alloys were hot-rolled in α + β phase fi...

Solution treatment and ageing (STA) is an effective strengthening method for + β titanium alloys. This paper reports the effect of solution treatment and aging on the corrosion behaviour of Ti-6Al-7Nb alloy in a simulated body fluid (Ringer's solution). Ti-6Al-7Nb alloy is hot rolled in the + β field and subjected to solution treatment above and be...

This work reports the effect of heat treatment on the corrosion behavior of Ti–13Nb–13Zr alloy in Ringer’s solution. The microstructural evolution of various phases after beta solution treatment (βST) and alpha + beta solution treatment (α+β ST), is studied using optical microscope, electron probe microanalysis and XRD techniques. Corrosion behavio...

A Ti-6Al-7Nb alloy was surface modified using pulsed plasma nitriding and nitrogen ion implantation in order to study its microstructural changes and corrosion performance. Pulsed plasma nitriding was performed for 30 h at 913 K in a gas mixture of 3:1 N2:H2 under a total pressure of 3 mbar. Nitrogen ion was implanted at 100 keV using a 150 keV acc...

The present paper reports on the microstructure, hardness, surface roughness, phases formed and corrosion behaviour of laser nitrided Ti-13Nb-13Zr biomedical alloy. Surface melting and nitriding of the alloy were carried out using a Nd:YAG laser in pulsed mode under dilute and pure nitrogen environments. Laser nitriding of the alloy resulted in a h...

The aim of this paper is to study the effect of N+ ion implantation on corrosion and phase formation on the implanted surfaces of Ti–6Al–4V and Ti–6Al–7Nb alloys. Nitrogen ion was implanted on Ti–6Al–4V and Ti–6Al–7Nb alloys at an energy of 70 and 100 keV, respectively using a 150 keV accelerator at different doses ranging from 5×1015 to 2.5×1017 i...

The site preference of Zr atoms in Ti 3Al and the phase stability of Ti2ZrAl are examined using first-principles electronic structure total energy calculations. Of the sixteen possible ways in which Ti, Zr and Al atoms can be arranged, in the lattice sites corresponding to D019 structure of Ti3Al, to obtain Ti2ZrAl, it is shown that Zr atoms prefer...

Titanium is a wonder metal, generally considered as one of the most biocompatible and corrosion resistant metals available for clinical applications. Since 1951, when Leventhal /1/ first published an article on the orthopaedic application of this metal, research activity and clinical experience resulted in new developments in the manufacturing and...

In the present investigation, surface modification of Ti–6Al–7Nb alloy with nitrogen ions is considered as a method to improve its performance with respect to corrosion. Nitrogen ion was implanted on Ti–6Al–7Nb alloy at an energy of 70 and 100 keV using a 150 keV accelerator at different doses between 1×1016 and 3×1017 ions/cm2. Gracing incidence X...

The site preference of Zr atoms in Ti3Al and the phase stability of Ti2ZrAl are examined using first-principles electronic structure total energy calculations. Of the 16 possible ways in which Ti, Zr, and Al atoms can be arranged, in the lattice sites corresponding to D019 structure of Ti3Al, to obtain Ti2ZrAl, it is shown that Zr atoms prefer to g...

This work describes the effect of mechanical working and heat treatment on the microstructure of the alloy Ti–13Nb–13Zr using X-ray diffraction and metallography. Lattice parameters of the constituent phases in as cast and different heat-treated conditions have been calculated. The β solution treatment and water quenching (WQ) results in the α′ mar...

Band structure calculations of ABC2 (A = Zn, B = Si, Ge, Sn, and C = P, As) ternary pnictides performed using the semi-relativistic ‘tight binding linear muffin tin orbital’ (TB-LMTO) method within local density approximation under ambient and high pressures are reported here. The energy gap at ambient pressure is found to be direct in all the case...

The detailed bandstructure of Mg having the HCP lattice structure has been calculated using the KKR method for the three different potentials Vs, VH and Vvs. The potential Vs includes only the exchange part through Slater's formula whereas the other two potentials VH and Vvs include exchange as well as correlation. The energy bands, density of stat...

Results of bandstructure calculations of Tc, which has a HCP lattice structure, are used to calculate the superconducting transition temperature Tc and the Fermi surface of the metal. The strong-scattering theory of Gaspari and Gyorffy (1972) is used in conjunction with McMillan's formula (1968) to calculate Tc in the spherical band approximation....

The self-consistent tight-binding linear muffin-tin orbital method was employed to calculate the electronic structure and the total energy of Ti2XAl (X=Nb, V, Zr) in B2, D019, and O (orthorhombic) phases and the results were used to study the phase stability and cohesive properties of these intermetallic compounds. Our theoretical calculation shows...

The results of the electronic band structure calculations performed on ternary chalcogenides ABX2 (A = Cu Ag; B = Ga, In; X = S, Se, Te) using the semi-relativistic Tight Binding Linear Muffin Tin Orbital method are reported. The equilibrium lattice constants and the bulk moduli obtained from the P–V curves agree very well with the experimental val...

The predicting capability of various parameters related to solids by performing their high pressure electronic band structures is discussed in detail. The studies on ground state crystal structure, magnetic structure and magnetic phase transitions under pressures,s-d electron transitions, bulk modulus, Debye temperature, elastic constants, insulato...

The first theoretical attempt to explain the role of interstitials in the superconducting behaviour of intermetallic compounds is reported here. Further, the often-quoted correlation between stability and superconductivity in intermetallic compounds is also confirmed. Band-structure results obtained from our calculations on La3X and La3XC are compa...

From the detailed electronic structure studies on intermetallic compounds, it has been found that these materials have low heat of formation and large glass-forming ability, if the Fermi level falls on the peak in the density of states (DOS) curve. On the other hand, if theE F falls on the pseudogap in the DOS curve, the ordering energy will be lar...

The self-consistent scalar relativistic band structure for AgGaX2 (X = S, Se, Te) performed in chalcopyrite structure using the TBLMTO method at various pressures are reported here. Empty spheres were introduced in the calculations as the chalcopyrite structure is loosely packed. From the total energy calculations, the equilibrium lattice constant...

Self-consistent scalar relativistic band structure calculations for NaI, KI and RbI performed both in NaCl (B1) and CsCl (B2) structures using the tight-binding linear muffin tin orbital (TB-LMTO) method are reported. The valence bandwidths were calculated and compared with the available experimental and theoretical results. From the total energy c...

This paper reports the effect of substitution of Nb on the physical properties of Ni3Al using the tight-binding linear-muffin tin-orbital method. The systematic total-energy studies made on Ni3Al and Ni3Nb in both L12 (Cu3Au) and DOa (beta-Cu3Ti) structures successfully explained the structural stability of these two compounds. In order to understa...

The authors report here the growth and single-crystal X-ray structure analysis of NdBaâCuâO{sub 6.88} with a tetragonal unit cell and a superconducting transition temperature of 63 K. Both a and b edge centers are partially occupied.

The band structure and the density of states (DOS) of YNi2B2C, YRh3B, and YNi4B are obtained using the tight-binding linear muffin-tin orbital method. From our studies, we have found that the Fermi level falls on one of the peaks in the DOS curves of both YNi2B2C and YRh3B and this is responsible for superconductivity in these compounds. In order t...

The compounds LaBaCa2Cu3Oy and La1.1 Ba0.9Ca2Cu3Oy are synthesised with Tc values 25.5 and 26 K. XRD studies reveal the orthorhombic structure for these compositions. The high pressure electrical resistivity studies performed at ambient temperature on the system show a sharp drop with increasing pressure.

We report here the magnetic and nonmagnetic electronic-structure calculations of the perovskite oxides LaM${\mathrm{O}}_{3}$ (M=Ti to Ni) and the orthorhombic ${\mathrm{LaScO}}_{3}$ performed using the tight-binding linear-muffin-tin-orbital method. Total-energy calculations for these systems reproduce the magnetic phases observed at low temperatur...

We report here the magnetic and nonmagnetic electronic-structure calculations of the perovskite oxides LaMO3 (M=Ti to Ni) and the orthorhombic LaScO3 performed using the tight-binding linear-muffin-tin-orbital method. Total-energy calculations for these systems reproduce the magnetic phases observed at low temperature. The calculations correctly ac...

Antiferromagnetic electronic-structure calculations of the perovskite fluorides KMF3 (M=Mn,Fe,Co,Ni) carried out using the linear muffin-tin orbital method are reported here. The calculations have successfully predicted the insulating gaps of the systems KMnF3 and KNiF3. However, in the cases of KFeF3 and KCoF3 the insulating gap could not be accou...

We report here the ambient and high-pressure electronic-structure calculations of the potentially important ordered intermetallic alloy Zr3Al obtained using the self-consistent linear muffin-tin orbitals (LMTO) method. Further total-energy calculations were made using the tight-binding LMTO scheme in the L12 and DO19 phases in order to study its st...

The electronic structure calculations of the narrow gap IV-VI semiconducting compounds GeTe, SnTe and PbTe were performed for different reduction cell volumes employing the LMTO method. The theoretically calculated values of the superconducting transition temperature using McMillan’s formula were found to be in good agreement with the experimental...

High pressure band structure results obtained on isoelectronic solids such as Xe, CsI and BaTe as well as on other Ba chalcogenides, with the aim of understanding the phenomenon of Insulator to metal transition and possible superconductivity are discussed. The relative weighting of the factors such as the density of states at the Fermi energy, s→...

Barium neodymium copper oxide superconductors were synthesized. The samples were prepared by a single step process using high purity barium carbonate, neodymium oxide and copper oxide as starting materials. The powders were mixed, pelletized, sintered and characterized by X ray powder diffraction. The analysis showed that these ceramics exhibit str...

The first band structures and calculated electronic properties of the compounds LaSe and LaTe are reported. The energy band structure of lanthanum monochalcogenides are obtained using the self-consistent LMTO method within the atomic sphere approximation. The band structure outputs were used to calculate the physical properties such as the electron...

The first ever band-structure calculations performed for the intermetallic compounds ABi2 (A =K, Rb, Cs) using the Linear Muffin-Tin Orbital Method are reported in this paper. Metallicity in these compounds is found to be primarily due to the A-Bi bonding and the density of states at the Fermi energy is found to be mainly due to the Bi-6p electrons...

The band structures of the Laves phase systems YRh2 and LaRh2 determined using the LMTO method are reported here. The paramagnetic band structures and the DOS curves are compared with their counterparts YCo2 and LuCo2 which exhibit anomalous variation of susceptibility with temperature, while the rhodium compounds are Pauli paramagnetic. The band s...

We report the computation of electron energy bands of the intermetallic compounds BaRh2 and LaRu2. The energy bands were determined using the self-consistent linear muffin-tin-orbital method. The band-structure results were primarily used to calculate the electron-phonon coupling constant in order to explain the superconducting behavior. Further, t...

The electronic-structure calculations of the perovskite oxides SrFeO3 and SrCoO3 in the nonmagnetic and magnetic phases are reported here. The calculations were performed with use of the self-consistent linear muffin-tin-orbital method within the atomic-sphere approximation. The calculations show strong hybridization between the Fe and Co 3d and O...

In this paper, we report the high pressure band structure and superconductivity calculated for Bi at 9 GPa. The band structure calculation was performed using the LMTO method. The theoretically calculated value of superconducting transition temperature is found to be in good agreement with the experimentally observed value. It is concluded that the...

We report here metallization and possible superconductivity in Xenon when it is subjected to a pressure of the order of 137 GPa. The metal is found to be in the hcp phase at this pressure and our band structure calculations done using the linear muffin-tin orbital method show that the band gap closes around this pressure.

The electronic bandstructure of tellurium performed at 33 GPa, the highest pressure up to which experimental structural information is available and also its superconducting behaviour are reported here. The bandstructure calculation is done using the self-consistent Linear Muffin Tin Orbital (LMTO) method. The calculation shows a large d density of...

The electronic band structure of La2CuO4 is performed using self-consistent linear muffin-tin orbital method. The 17 band complex is found to arise mainly from the overlap between Cu-3d and O-2p wavefunctions. The calculated density of states at the Fermi energy (N E F), the conduction band-width and the electronic specific heat coefficient are giv...

The band structures of the perovskite oxides LaTiOâ and LaNiOâ are reported here. The band structures were done using the linear muffin tin orbital (LMTO) method. The Fermi energy, density of states at the Fermi energy and the number of electrons in the conduction band were all determined. These quantities were used to calculate the electronic spec...

This paper aims at explaining the phenomenon of pressure induced superconductivity that has been experimentally observed in some of the elemental solids such as black phosphorus, tellurium and iodine. As xenon has been shown to become metallic recently at very high pressure, we predict possible superconductivity in Xe. Our calculations are based on...

This paper brings out one of the striking features exhibited by all oxide superconductors. It is found that irrespective of the values of T sub c, the average electronegativity, x of all the oxide superconductors lies between 2.5 and 2.65. This is in contrast to the elemental superconductors whose x values lie in a broad range from 1.3 to 1.9. Furt...

The Compton profiles of nickel are calculated using an ab initio, spin-polarized self-consistent linear combination of Gaussian orbitals band-structure method within the local-density-functional theory. The resulting anisotropies are compared with recent experimental results of Rollason et al. The present theoretical results, which include the corr...

Recent experimental observations show that metallic lithium becomes a superconductor at high pressure. Here the theoretically calculated band structure as well as the superconducting transition temperature for this metal at 247 kbar pressure are reported. The band structure was obtained using the APW method. The superconducting transition temperatu...

The effect of pressure on the band structure and superconducting behaviour of barium is reported. The band structure calculations were performed with the use of self-consistent linear muffin-tin orbital method. The calculations show s yields d electron transfer under pressure, and this is in conformity with Wittig's prediction with regard to pressu...

We report here the s → d electron transfer and superconductivity in Barium under pressure. The bandstructure was done by Linear Muffin-Tin Orbital method at zero and 40kbar pressures. The density of states at the Fermi energy N(EF) and the number of state functions n(EF) were calculated using the Tetrahedron method. It was found that the d-electron...

We report here the effect of pressure on the band structure and the superconducting behavior of the hcp metal lutetium. The present work shows that the average of the square of the phonon frequency is considerably increased under pressure and this effect is taken into account while calculating T/sub c/. The calculated T/sub c/ values are in fairly...

We report the effect of pressure on phonon frequency and its influence on the superconducting transition temperature in the case of lanthanum. The variation of phonon frequency with pressure is calculated through the thermodynamic Grüneisen parameter γG. The calculated Tc values are found to agree very well with the experimental results.

The electronic bandstructures of rare earth metal Praseodymium (Pr) have been calculated for a wide range of static pressures using RAPW method. The density of states and Fermi surface cross sections on the principal planes corresponding to various pressures are obtained. It is seen that, there is, 4f shell breakdown in Pr under pressure and format...

The detailed band structure and superconducting behavior of lutetium when subjected to high pressure are reported. This is the first theoretical calculation which gives evidence to the experimentally observed superconductivity in lutetium at high pressures. The theoretical value of T//c is in good agreement with the experimental value. The trends i...

The bandstructure of actinium (Ac) having f.c.c. lattice structure is reported for the first time. The bandstructures have been calculated using the RAPW method for two different crystal potentials, the one that includes the exchange term alone and the other that includes both the exchange and correlation parts.

The effect of correlation has been included in the bandstructure calculation for thorium and osmium using the RAPW method. The complete bandstructure and Fermi surface cross sections are obtained for both the metals using the two potentials, the one (Vs) which includes only the Slater exchange and the other (VH) which includes both the exchange and...

Results of first-principles, density-functional, TBLMTO -ASA calculations on the closely related ZrGa2 and HfGa2 structures of the reentrant phase TiAl2 intermetallic compound is reported. Theoretical calculations shows, that HfGa2 structure is more stable structure than ZrGa2 in agreement with experimentalists. However, the other structure is very...

In this paper, the electronic structure and ground state properties of the Titanium borides (Ti2B, TiB and TiB2 ) calculated using the self consistent Tight-Binding Linear Muffin-Tin Orbital method are reported. We have carried out a systematic electronic structure studies for these Titanium borides for different volumes . We deduced from the above...