Browsing by Author "O.P. Sinha"

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A review on nickel-free nitrogen containing austenitic stainless steels for biomedical applications
(2013) Mohd Talha; C.K. Behera; O.P. Sinha
The field of biomaterials has become a vital area, as these materials can enhance the quality and longevity of human life. Metallic materials are often used as biomaterials to replace structural components of the human body. Stainless steels, cobalt-chromium alloys, commercially pure titanium and its alloys are typical metallic biomaterials that are being used for implant devices. Stainless steels have been widely used as biomaterials because of their very low cost as compared to other metallic materials, good mechanical and corrosion resistant properties and adequate biocompatibility. However, the adverse effects of nickel ions being released into the human body have promoted the development of "nickel-free nitrogen containing austenitic stainless steels" for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also much improves steel properties. Here we review the harmful effects associated with nickel and emphatically the advantages of nitrogen in stainless steel, as well as the development of nickel-free nitrogen containing stainless steels for medical applications. By combining the benefits of stable austenitic structure, high strength, better corrosion and wear resistance and superior biocompatibility in comparison to the currently used austenitic stainless steel (e.g. 316L), the newly developed nickel-free high nitrogen austenitic stainless steel is a reliable substitute for the conventionally used medical stainless steels. © 2013 Elsevier B.V.
AFM studies of swift heavy ion-irradiated surface modification in Si and GaAs
(2003) P.C. Srivastava; V. Ganesan; O.P. Sinha
Atomic force microscopy (AFM) studies of Swift Heavy Ions (SHI ∼100 MeVSi7+ and Au7+) irradiated Si and GaAs surfaces have been performed for a variable fluence in the range of 1010-10 13 ions cm-2. The craters with piled up material, which is called hill, are clearly seen in the micrographs. A significant direct observation of amorphization (or melting due to SHI irradiation damage), plastic flow and subsequent recrystallization in the form of platelets has been made. The quantitative estimation of the features revealed that the volume of the craters for silicon ion irradiation is smaller than the gold ion irradiation. However, surface roughness has been found to be enhanced after the irradiation. Moreover, the GaAs surfaces were found to be less rough than the Si surface. The features are related to the difference in electronic energy loss of incident ions, thermal diffusivity, thermal conductivity and density of the target materials. © 2003 Elsevier Ltd. All rights reserved.
AFM study of swift gold ion irradiated silicon
(2002) P.C Srivastava; V. Ganesan; O.P. Sinha
AFM studies of swift (∼100 MeV) heavy ion (Au7+) irradiated crystalline p- and n-type silicon surfaces have been performed. The irradiation fluence has been varied from 1010 to 1012 ions cm-2. The studies have shown the formation of clear craters surrounding a hill for the irradiated p-type only whereas a hill on one side of the crater for the irradiated p- and n-type silicon surfaces has been observed. The surface roughness has been observed to be increased after the irradiation and the increase for n-type is significantly larger as compared to that for p-type. The quantitative estimate of the volume of the craters and hills has shown a larger volume (2.0-4.0 times) for the craters as compared to the hills. Moreover a larger volume for craters and hills for n-type as compared to p-type has been found. The observed features have been discussed as the radiation induced mass transfer from within the substrate to its surface and a fraction sputtered out due to the explosive evaporation as a result of heating due to electronic energy loss. The distinctly different features for n-type and p-type seem to be due to dopant dependent fault growth and shrinkage rates. © 2002 Elsevier Science B.V. All rights reserved.
Effect of cold working on biocompatibility of Ni-Free high nitrogen austenitic stainless steels using Dalton's Lymphoma cell line
(2014) Mohd Talha; Sanjay Kumar; C.K. Behera; O.P. Sinha
The aims of the present work are to explore the effect of cold working on in-vitro biocompatibility of indigenized low cost Ni-free nitrogen containing austenitic stainless steels (HNSs) and to compare it with conventionally used biomedical grade, i.e. AISI 316L and 316LVM, using Dalton's Lymphoma (DL) cell line. The MTT assay [3-(4,5-dimethythiazol 2-yl)-2,5-diphenyltetrazolium bromide] was performed on DL cell line for cytotoxicity evaluation and cell adhesion test. As a result, it was observed that the HNS had higher cell proliferation and cell growth and it increases by increasing nitrogen content and degree of cold working. The surface wettability of the alloys was also investigated by water contact angle measurements. The value of contact angles was found to decrease with increase in nitrogen content and degree of cold working. This indicates that the hydrophilic character increases with increasing nitrogen content and degree of cold working which further attributed to enhance the surface free energy (SFE) which would be conducive to cell adhesion which in turn increases the cell proliferation. © 2013 Elsevier B.V. All rights reserved.
Effect of nitrogen and cold working on structural and mechanical behavior of Ni-free nitrogen containing austenitic stainless steels for biomedical applications
(Elsevier Ltd, 2015) Mohd Talha; C.K. Behera; O.P. Sinha
This investigation deals with the evaluation of structural and mechanical behavior of deformed (10% and 20% cold work) and annealed (at 1050 °C for 15 min followed by water quenching) Ni-free high nitrogen austenitic stainless steels (HNSs). The microstructure was observed by optical micrograph and the mechanical properties were determined by macrohardness and tensile tests. Both stress strain behavior and work hardening behavior were evaluated. HNSs have smaller grain size as compared to low nitrogen steels and no formation of martensite was observed after 20% cold working. Further, it was found that hardness; yield strength and ultimate tensile strength of the steels linearly increases and elongation decreased with nitrogen content and degree of cold working. The strength coefficient was observed to be higher for the high nitrogen steels; it decreased to some extent with degree of cold working. The work hardening exponent was also observed to decrease with degree of cold working. Influence of nitrogen on mechanical properties was mainly related to its effect on solid solution strengthening. X-ray diffraction analysis of annealed as well as deformed alloys further confirmed no evidence for formation of martensite or any other secondary phases. SEM fractography of the annealed and deformed samples after tensile tests indicates predominantly ductile fracture in all specimens. © 2014 Elsevier B.V. All rights reserved.
Electrical and XPS studies of 100 MeV Si 7+ ion irradiated Pd/n-GaAs devices
(Elsevier, 2004) O.P. Sinha; T. Shripathi; N.P. Lalla; P.C. Srivastava
The effect of Swift Heavy Ion (100MeV Si 7+ ) irradiation on electronic-transport of Pd/n-GaAs devices has been studied by I-V and C-V techniques. The chemical compositions of the interface have been studied by XPS/EDAX techniques. It is observed that the irradiated devices show a reduction in current and capacitance by few orders of magnitude. The C-V characteristics show a change in conductivity type from n- to p-type after the irradiation. On hydrogenation, the irradiated devices show a capacitance peak in C-V characteristics, which has been ascribed to As vacancies. The XPS studies of these devices, for various etching durations, show that the ratio of As:Ga has reduced after the irradiation, which indicates the formation of irradiation-induced As vacancies. This reduction in As:Ga ratio is also confirmed by EDAX measurement. The observed conductivity type change from n- to p-type (on the irradiation) seems to be due to the change of substitutional sites of dopant silicon atoms from Ga to As sites due to the irradiation-induced As vacancies. © 2004 Elsevier B.V. All rights reserved.
Evidence of plastic flow and recrystallization phenomena in swift (∼ 100 MeV) Si7+ ion irradiated silicon
(2004) P.C. Srivastava; V. Ganesan; O.P. Sinha
Surface modifications caused by a swift heavy ion irradiation on a crystalline p-type silicon crystal have been reported. ∼ 100 MeV Si 7+ ions from a 15UD Pelletron source has been employed with varying fluence of 1012 and 1013 ionscm-2. Atomic force microscopy has been extensively used to study these surface modifications. Significant observation includes the evidence for a plastic flow upon irradiation. Attempts have been made to explain the results on the basis of radiation-induced amorphization followed by recrystallization. The observation confirms the occurrence of these types of effects in such irradiations and is in line with the models based on thermal spike approach. © 2004 Elsevier B.V. All rights reserved.
High energy heavy ion irradiation in semiconductors
(Elsevier Science Publishers B.V., 1999) P.C. Srivastava; S.P. Pandey; O.P. Sinha; D.K. Avasthi; K. Asokan
Pd/n-Si and Pd/n-GaAs devices have been irradiated from high energy (approximately 100 MeV) heavy ions of Au7+ (gold) and Si7+ (silicon) to study the irradiation effects in these junction devices on semiconductor substrates. The devices have been characterized from I-V and C-V studies for electronic flow characterization. It has been found that the devices become high resistive on the irradiation and the substrates change the conductivity type from n- to p- on the irradiation of fluence of approximately 1012-1013 ions/cm2. The change in conductivity type has been understood as a result of creation of deep acceptors on the irradiation.
In situ I-V study of swift (∼100 MeV) O6+ ion-irradiated Pd/n-Si devices
(2002) P.C. Srivastava; O.P. Sinha; J.K. Tripathi; D. Kabiraj
An in situ I-V study of Pd/n-Si devices irradiated to swift (∼100 MeV) O6+ ions for a fluence of 1011-1013 cm-2 has been carried out. The devices have been irradiated at room and LN2 temperatures. The irradiated devices have been hydrogenated in ex situ condition by molecular hydrogen. It has been observed that resistivity increases after the irradiation and there is a progressive increase with the increase of irradiation fluence. On hydrogenation, the devices irradiated at LN2 temperature show that the irradiation-induced increased resistivity decreases back to the pre-irradiated condition, whereas the devices irradiated at room temperature do not show any change. The results have been understood in the realm of irradiation-induced defects.
Long term and electrochemical corrosion investigation of cold worked AISI 316L and 316LVM stainless steels in simulated body fluid
(Royal Society of Chemistry, 2014) Mohd Talha; C.K. Behera; Sudershan Kumar; Om Pal; Gurmeet Singh; O.P. Sinha
AISI 316L and 316LVM stainless steels in annealed (solution quenched from 1050°C) and rolled (10% and 20% cold work) conditions were assessed for their long term and electrochemical corrosion behavior in simulated body fluid (SBF) at 37°C. The techniques used for the characterization of their corrosion resistance were the weight loss method, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. Scanning electron microscopy (SEM) was used to investigate the surface morphologies of the alloys after the polarization tests. Surface analysis of the films formed on the steels in SBF was carried out using X-ray photoelectron spectroscopy (XPS). The weight loss and corrosion rate decreased with increasing degree of cold working. The resistance of a passive film is directly related to the material's corrosion resistance and increases on cold working, indicating the formation of a larger protective oxide layer on the surface of cold worked samples. The corrosion current density (Icorr) decreased with increasing degree of cold working and, simultaneously, the corrosion potentials (Ecorr) became more positive. On observing the pit morphologies using SEM, shallower and smaller pits were associated with cold worked samples as compared to annealed samples. The XPS results indicated that the main elements in the passive oxide layer were Cr, Fe and Mo. The Cr-oxide (ox):Cr-hydroxide (hy) ratio and the Fe-oxide (ox):Fe-hydroxide (hy) ratio were observed to be higher for rolled materials than for annealed materials, indicating that the passive films on rolled materials are more protective and improve the corrosion resistance. This journal is © the Partner Organisations 2014.
Microcracks in ∼ 100 MeV Si7+-ion-irradiated p-silicon surfaces
(2004) O.P. Sinha; P.C. Srivastava; V. Ganesan
The p-silicon surfaces have been irradiated with ∼ 100 MeV Si 7+ions to a fluence of 2.2 × 1013 ions cm -2, and surface morphology has been studied with atomic force microscopy (AFM). Interesting features of cracks of ∼ 47 nm in depth and ∼ 103 nm in width on the irradiated surfaces have been observed. The observed features seemed to have been caused by the irradiation-induced stress in the irradiated regions of the target surface.
Surface modification by swift (∼100 MeV) Si7+ and Au 7+ ions irradiation in n-GaAs
(2006) O.P. Sinha; V. Ganesan; P.C. Srivastava
AFM studies of swift (∼100 MeV) heavy ions (of Si7+ and Au7+) irradiated n-GaAs have been performed for a variable fluence of 1010-1013 cm-2. The craters with a piled up material are clearly seen in the AFM micrographs. It is observed that the gold ions are inducing more damage than silicon ions as the estimated volume of craters and surface roughness are larger for gold ion irradiation than the silicon ion irradiation. The feature of overlapping craters has also been observed for n-GaAs surfaces. The observed features are related to the large electronic loss of the incident ions, thermal diffusivity and thermal conductivity of the target material. © 2005 Elsevier B.V. All rights reserved.
Utilization of iron ore slime and bottom ash: An overview
(Elsevier Ltd, 2021) R. Kumar; A.K. Mandal; Raj K. Dishwar; O.P. Sinha
Steel plants are the primary producer of solid waste materials like slags from blast furnaces and L.D. Plant with fly ash /bottom ash from the power plant, iron ore slimes from ore washing plant, coal/coke from coke ovens, etc. It is estimated that about 84% of total solid waste generation is in iron ore tailings (Fines/ Slimes), coal combustion residues (Fly Ash or Bottom Ash), and the remaining 16% constitute all others, including slag. The above wastes (Iron ore slime & Bottom ash/ Fly ash) are being used for landfilling and in few countries to get value-added products. However, the partial or bulk utilization of such waste is still an academic issue in India. The present paper reviews past and recent research work to utilize two significant unutilized waste (Iron ore slime & Bottom Ash). The promising areas for utilization of Iron Ore Slime and Bottom Ash are the making of bricks (constructional, insulation), use as bed filter materials, and Ferro / master alloys' production as a part of metal recovery using smelting reduction process. (e.g., Al, Si, etc.). © 2021 Elsevier Ltd. All rights reserved.