• Santosh Kumar

      Articles written in Bulletin of Materials Science

    • Precipitation hardening and hydrogen embrittlement of aluminum alloy AA7020

      Santosh Kumar T K G Namboodhiri

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      AA7020 Al–Mg–Zn, a medium strength aluminium alloy, is used in welded structures in military and aerospace applications. As it may be subjected to extremes of environmental exposures, including high pressure liquid hydrogen, it could suffer hydrogen embrittlement. Hydrogen susceptibility of alloy AA7020 was evaluated by slow strain-rate tensile testing, and delayed failure testing of hydrogen-charged specimens of air-cooled, duplexaged, and water-quenched duplex agedmaterials. The resistance to hydrogen embrittlement of the alloy was found to be in the order of air-cooled duplex aged alloy > as-received (T6 condition) > water quenched duplex aged material.

    • Dielectric behaviour of sodium and potassium doped magnesium titanate

      Vishnu Shanker Santosh Kumar T Surendar

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      Pure phase of magnesium titanate (MgTiO3) was obtained at 1100°C by both the conventional solid-state method as well as by the flux method starting from hexahydrated magnesium nitrate and titanium dioxide as the reactants. MgTiO3 doped with Na or K was also prepared by the solid-state route. Na and K doped compositions led to monophasic MgTiO3 below 5 mol% dopant concentration while biphasic mixture of MgTiO3 (major phase) and MgTi2O5 (minor phase) were obtained at higher dopant concentration. The dielectric constant and dielectric loss of MgTiO3 were found to be almost the same irrespective of the preparative method. MgTiO3 doped with 5 mol % of Na and K ions displayed optimum dielectric properties.

    • Characterization and in vitro and in vivo evaluation of cross-linked chitosan films as implant for controlled release of citalopram

      Patit P Kundu Santosh Kumar Jindal Manish Goswami

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      The aim of the present study is to develop cross-linked chitosan (CH) films that can release drug over an extended period of time and that too in a controlled manner. A solution of different percentages of CH, is prepared in 1% lactic acid, followed by addition of citalopram (CTP) and then reacted with increasing amounts of glutaraldehyde (GL) to obtain films with different cross-linking densities. Prepared films are characterized for their physical and mechanical properties. The films are then subjected to in vitro drug release studies using pH 7.4 phosphate buffer saline (PBS) as dissolution medium and cumulative amount of drug released is calculated. Kinetic analysis of drug release is performed using Power law model and Higuchi’s model.With increase in concentration of CH, water absorption capacity and mechanical strength are increased; whereas, water vapour permeability and elasticity of the films are decreased. The effect of cross-linking agent, GL, is such that with an increase in the amount of GL, water vapour permeability, water absorption capacity and elasticity of the films are decreased; whereas, mechanical strength increased to some extent and then decreased. In vitro release studies indicate that films containing 3% CH, cross-linked with 2–3% GL and films containing 4%CH, cross-linked 1%GL are able to sustain the drug release for a prolonged time along with releasing almost complete drug in a desired period. Out of these batches, films containing 3% CH, cross-linked with 2–3% GL are having sufficient strength, water vapour permeation, water absorption capacity and elongation at break for implantation purpose. The in vitro degradation studies and histopathological studies were carried out with a sample film (batch C3 as in table 1) in rabbit model. In vitro degradation study indicates that the films maintained their integrity for desired implantation. The histopathological studies under optical microscope indicates that on implanting, there is no evidence of any inflammation, any foreign body granuloma or any necrosis or hemorrhage. Tissue configuration remains unaltered after 30 days of implantation. So, it can be suggested that cross-linked CH films of above said composition can be used as implant for long term application in depression and related disorders.

    • Studies on thermo-optic property of chitosan–alizarin yellow GG complex: a direction for devices for biomedical applications

      Nidhi Nigam Santosh Kumar Pradip Kumar Dutta Tamal Ghosh

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      The optical parameters including the refractive index (𝑛) and thermo-optic coefficient, TOC (d𝑛/d𝑇), the dielectric constant (𝜀) and its variation with temperature, and the thermal volume expansion coefficient (𝛽) and its variation with temperature of chitosan–alizarin yellow GG (CS–AY GG) complex were examined. The dn/dT and 𝜀- values for the polymer derivative were in the range −2.5 × 10−4 to 1.2 × 10−4° C−1 and 2.2 to 2.3, respectively. The dn/dT values were larger than that of inorganic glasses such as zinc silicate glass (5.5 × 10−6° C−1) and borosilicate glass (4.1 × 10−6° C−1) and were larger than that of organic polymers such as polystyrene (−1.23 × 10−4 ° C−1) and PMMA (−1.20 × 10−4 ° C−1). The 𝜀-values are lower than optically estimated 𝜀-values of conventional polymer (3.00), aliphatic polyimide (2.5) and semi-aromatic polyamide (2.83). The obtained results of chitosan derivative are expected to be useful for optical switching and optical waveguide areas for devices of biomedical applications.

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    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

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      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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