006131   Verma P et al (NO, Solid State Physical Laboratory, Delhi-110 054) : Carbon nanotube-based cold cathode for high power microwave vacuum electronic devices: a potential field emitter. Def Sci J 2008, 58(5), 650-4.

Carbon nanotubes (CNTs) can be grown in the form of small, sharp spikes capable of carrying very high current densities which suggest great potential application of CNTs as cold cathode in high power microwave vacuum device applications. These cold cathode vacuum microwave devices are expected to be ideally suited for air-borne and space applications. Reports the initial efforts made in the development of cold cathode using PECVD grown vertically-aligned matrix of CNTs with uniform height and optimum tip density on silicon substrate. The high aspect ratio (of the order of 10,000) and novel electrical, mechanical, and thermal properties of the CNT are found to be very attractive characteristics for emission of large and stable current densities at reasonably low field. The field emission current voltage characteristics of a typical cathode gave emission current density in excess of 35 mA/cm² at reasonably low field. The emission current in most of the samples is found to be stable over long period of time but is greatly effected by the vacuum condition during measurement. The initial measured data suggests great promise for achieving high current densities at practical electric fields.

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006130   Vaidya S;Ahmed J;Ganguli A K (NO, Indian Institute of Technology, New Delhi-110 016) : Controlled synthesis of nanomaterials using reverse micelles. Def Sci J 2008, 58(4), 531-44.

Monophasic nanosized oxides were synthesised mainly from metal oxalate nanorods obtained using the reverse micellar method. Focuses on the methodology to obtain important metal oxides like tin dioxide, cerium oxide (CeO₂), zirconia, and zinc oxide. The effect of oxidation state of the metal ion on the morphology of the oxalates was studied. Nanorods of zinc (II) oxalate (120 nm in dia and 600 nm in length) were obtained while spherical particles of size 4-6 nm were obtained for cerium (III) oxalate. The decomposition of these precursors at higher temperature led to the formation of their respective oxides. Mixture of nanorods and nanoparticles of CeO₂ was obtained while 3-4 nm sized ZrO₂ nanoparticles were obtained by thermal decomposition of zirconium oxalate precursor. The dielectric constant and loss were highly stable with frequency (at room temperature) for both ceria and zirconia nanoparticles. ZnO nanoparticles (55 nm sized) were obtained by the decomposition of zinc oxalate nanorods. Three peaks corresponding to free excitonic emission, free-to-bound, and donor-acceptor transitions were observed in the photoluminescence studies at 20 K for ZnO nanoparticles.

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006129   Upadhyay T C;Kandpal B (Physics Dep, H N B Garhwal University, Srinagar (Garhwal), Uttarakhand-246 174, Email: trilokphys@yahoo.co.in) : Temperature dependence of microwave loss in rochelle salt crystal. Indian J pure appl Phys 2009, 47(2), 134-40.

Considering two-sublattice pseudospin lattice coupled mode model [Chaudhuri et al., J Phys Soc Jpn, 49(1980) 609] along with third-and fourth-order phonon anharmonic interaction terms and using double-time thermal Green's function method, expressions for shift, width, renormalized soft mode frequency, Curie temperature, dielectric constant and microwave absorption have been derived and discussed for rochelle salt crystal. By fitting model values of physical quantities, soft mode frequency, dielectric constant and microwave loss tangent have been calculated. Theoretical results compare well with experimental results of Sandy and Jones, Phys Rev, 168 (1968) 481.

006128   Upadhyay T C (Physics Dep, H N B Garhwal University, Srinagar (Garhwal), Uttarakhand-246 174, Email: trilokphys@yahoo.co.in) : Temperature dependence of microwave loss in antiferroelectric squaric acid crystal. Indian J pure appl Phys 2009, 47(2), 119-24.

A model of pseudospin for layers 1 and 2 of squaric acid (SQA) crystal proposed by Li and Qin, Ferroelectrics, 82 (1988), 69 has been modified to include pseudospin-phonon interaction and cubic and quartic phonon anharmonic interactions. With the help of double-time temperature dependent Green's function method and modified Hamiltonian, expressions for antiferroelectric soft mode frequency, dielectric constant and loss have been evaluated. By fitting model values of physical quantities in the theoretical expressions, temperature dependences of soft mode frequency and loss have been calculated. In the microwave frequency range, an increase in frequency is followed by increase in loss. The loss decreases with increase in temperature for SQA crystal in its paraelectric phase. This shows Curie-Weiss behaviour of the dielectric tangent loss. Theoretical results are compared with experimental results of Muser [Proc. 6th Int'l Meeting on Ferroelectricity, Kobe (1985)], Maier et al. [Phys Status Solidi (b) 89, (1978)], and Samara and Semmingsen [J Chem Phys 71 (3) (1979) 1401] which show a good agreement.

006127   Upadhyay T C (Physics Dep, H N B Garhwal University, Srinagar (Garhwal), Uttarakhand-246 174, Email: trilokphys@yahoo.co.in) : Temperature dependence of microwave loss in ADP-type crystals. Indian J pure appl Phys 2009, 47(1), 66-72.

By using four sublattice pseudospin lattice coupled mode model along with third and fourth-order phonon anharmonic interaction terms for ADP-type crystals, expressions for shift, width, renormalized soft mode frequency, dielectric constant and loss have been evaluated. The method of double-time thermal Green's function has been used for calculation. Fitting the values of model parameters in expressions, the temperature dependences of soft mode frequency and loss have been calculated. In the microwave frequency range, an increase in frequency is followed by increase in loss. The loss decreases with increase in temperature for ADP crystal in its paraelectric phase. This shows Curie-Weiss behaviour of the dielectric tangent loss. Theoretical results are compared with experimental results of Nagamiya [Progr Theor Phys, 7 (1952) 275] and Busch, Helv Phys Acta, 11 (1938) 269]. A good agreement has been found.

006126   Tiwari S;Sharma Y K (Applied Physics Dep, Bhilai Institute of Technology, Durg, Chhatisgarh-491 001, Email: samit_tiwari@rediffmail.com) : CDDM noise characteristic of spherical current flow in low mobility insulator at low and high injection level of current. Natn Acad Sci Lett 2007, 30(5-6), 173-5.

Complete conductance noise characteristic has been studied for the steady state single injection spherical current flow in low mobility insulators at different injection level of currents. It is shown that the complete conductance noise characteristic starts from pure ohmic noise regime which finally merges into the space charge dominated noise regime after passing from a critical point.

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006125   Thomas M;George K C (Physics Dep, B C M College Kottayam, Kerala 686 001, Email: marykutythomas@yahoo.co.in) : Infrared and magnetic study of nanophase zinc ferrite. Indian J pure appl Phys 2009, 47(2), 81-6.

Nanophase zinc ferrite (ZnFe₂O₄) has been prepared by co-precipitation under stoichiometric conditions. The effect of reactant concentration on particle size has been studied using XRD, structural details using IR absorption spectroscopy, thermal properties using TG/DTA analysis and magnetic moment using SQUID magnetometer measurement. IR spectroscopy has been found to be an important tool for characterizing nanophase ZnFe₂O₄ particles size in the range 4 to 28nm. The positions of the absorption band are found to be particle size dependent. The large increase in magnetization with decrease in particle size may be due to super exchange interaction between Fe^{3+ ions on two sublattices A and B. The morphology of the sample has been investigated by TEM and selected area electron diffraction pattern.}

006124   Thirumaran S;Job Sabu K (Physics Dep(DDE), Annamalai University, Annamalainagar-608 002, Email: thiru_phymaran@yahoo.co.in) : Ultrasonic investigation of amino acids in aqueous sodium acetate medium. Indian J pure appl Phys 2009, 47(2), 87-96.

The ultrasonic velocity (U), density (ρ) and viscosity (η) measurements have been carried out for four amino acids namely L-alanine, L-leucine, L-valine and L-proline in aqueous sodium acetate solution as a function of composition at 303, 308 and 313K. Experimental data have been used to estimate the adiabatic compressibility (β), change in adiabatic compressibility (Δβ), relative change in adiabatic compressibility (Δβ/β₀), apparent molal compressibility (ϕ_K), apparent molal volume (ϕ_V), limiting apparent molal compressibility (ϕ^o_K ), limiting apparent molal volume (ϕ^o_V ) and the constants (S_K, S_V) and viscosity B-Coefficient. The results are discussed in terms of structure-making or structure-breaking effects of amino acids in the mixture.

006123   Subba Rao S V;Subramanyam B (NO, Satish Dhawan Space Centre SHAR, ISRO, Shriharikota-524 124) : Analysis of acoustic emission signals using wavelet transformation technique. Def Sci J 2008, 58(4), 559-64.

Acoustic emission (AE) monitoring is carried out during proof pressure testing of pressure vessels to find the occurrence of any crack growth-related phenomenon. While carrying out AE monitoring, it is often found that the background noise is very high. Along with the noise, the signal includes various phenomena related to crack growth, rubbing of fasteners, leaks, etc. Due to the presence of noise, it becomes difficult to identify signature of the original signals related to the above phenomenon. Through various filtering/thresholding techniques, it was found that the original signals were getting filtered out along with noise. Wavelet transformation technique is found to be more appropriate to analyse the AE signals under such situations. Wavelet transformation technique is used to de-noise the AE data. The de-noised signal is classified to identify a signature based on the type of phenomena.

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006122   Srivastava R K;Prakash S G (Electronics & Communication Dep, Allahabad Univ, Allahabad-211 002, Email: rks3e@rediffmail.com) : Electroluminescence of Sm doped ZnS luminophor. Natn Acad Sci Lett 2007, 30(3-4), 113-15.

In the study an attempt has been made to see the effect of Sm doping on electroluminescent properties of ZnS:Cu luminophors. The electroluminescent emission characteristics have been compared for four samples viz ZnS:Cu,CI, ZnS:Sm, ZnS:Cu,Sm and ZnS:Cu,Sm,Cl. In the presence of Sm the spectral curves show a shift of emission band towards lower wavelength side, whereas the frequency and voltage characteristics follow the universal law of emission. No intraband transition is observed.

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006121   Srivastava R;Chauhan G;Saxena K;Bawa S S; Srivastava P C;Kamalasanan M N (Center of Organic Electronics, Polymeric and Soft Material Section, National Physical Laboratory (CSIR), New Delhi-110 012) : Fabrication of white organic light-emitting diodes by co-doping of emissive layer. Indian J pure appl Phys 2009, 47(1), 19-23.

Efficient white light emission by mixing of red emission from (Ir-BTPA) [bis(2-(2'-benzothienyl) pyridinato-N,C^3') (acetyl-acetonate) iridium(III) and greenish blue from (FIrPic) [bis(2-(4,6-difluorophenyl)pyridinato-N,C^2') iridium(III)] has been studied. Ir-BTPA and FIrPic are co-doped into a 4, 4' bis 9 carbozyl (biphenyl) (CPB) host. The device emission colour is controlled by varying dopant concentration. Photoluminescence (PL), electroluminescence (EL) and colour coordinates have been studied as a function of applied voltage. The EL spectra of the devices with the co-doped emissive layer show three emission peaks at 469, 500 and 611 nm. Commission Internationale de I'Eclairage (CIE) coordinates of the devices are 0.27, 0.32 at 18 V and are well within the white region.

006120   Srinivasa Rao C;Eswara Reddy C (Mechanical Engineering Dep, PVP Siddhartha Institute of Technology, Kanuru, Vijayawada, Email: chepuri_srao@yahoo.co.in) : Finite element modeling of nanoindentation to extract load-displacement characteristics of bulk materials and thin films. Indian J pure appl Phys 2009, 47(1), 54-9.

The finite element modeling (FEM) technique has been applied to study the loading-unloading characteristics, stress and strain fields of the bulk materials such as titanium, iron, copper and thin films of titanium and copper subjected to Berkovich nanoindentation process. The loading and unloading curves obtained from numerical simulation results are compared with the curves obtained earlier through the experimental results and a good agreement has been found. The substrate effect is ignored and only thin film behaviour under indentation is considered. The thin films are indented within 5% thickness, rather than 10% rule of thumb.

006119   Singh A K (NO, Defence Institute of Advanced Technology, Pune-411 025) : Thermal conductivity of nanofluids. Def Sci J 2008, 58(5), 600-7.

Nanofluids are suspensions of nanoparticles in base fluids, a new challenge for thermal sciences provided by nanotechnology. Nanofluids have unique features different from conventional solid-liquid mixtures in which mm or μm sized particles of metals and non-metals are dispersed. Due to their excellent characteristics, nanofluids find wide applications in enhancing heat transfer. Research work on the concept, heat transfer enhancement mechanism, and application of the nanofluids is still in its primary stage. The study provides a review of research in this field with focus on thermal conductivity studies of nanofluids.

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006118   Shashi Bhushan;Oudhia A (School of Studies in Physics, Pt Ravishankar Shukla University, Raipur-492 010, Email: bhushan_312006@rediffmail.com) : Photoconductivity and photoluminescence studies of chemically deposited CdS-Se: CdCl₂, Ho/Nd films. Indian J pure appl Phys 2009, 47(1), 60-5.

Photoconductivity (PC) and photoluminescence (PL) emission spectra of different CdS-Se films doped with lanthanides Ho/ Nd, prepared by chemical bath deposition (CBD) method have been studied. The Scanning electron microscope (SEM), X-ray diffraction (XRD) and optical absorption spectral studies have been used for characterization. The PC studies show an enhancement in the photocurrent with the doping of flux and lanthanides. The PL emission spectra of undoped films show excitonic as well as donor-acceptor transitions, where as that of different doped films exhibit visible transitions between different energy levels of the impurities Ho and Nd.

006117   Sharma S;Pal K;Rajput S S;Mangotra L K;Jamuar S S (Physics and Electronics Dep, University of Jammu, Jammu-180 006, Email: susheelksharma@gmail.com) : Low-voltage variable current gain CCII based all-pass/notch filter. Indian J pure appl Phys 2009, 47(2), 149-52.

A second order low-voltage current conveyor type II (CCII) based filter circuit which can realize dual filter functions (all-pass/notch) depending on the current gain of CCII has been presented. The circuit employs equal valued components with all capacitors grounded and is more suitable for chip implementation. The circuit offers high input impedance, low output impedance and employs same type of active devices (CCII+). Theoretical results have been validated by PSpice simulations using 0.5 μm technology parameters at supply voltage of ± 0.75 V.

006116   Sharma A;Quamara J K (Applied Physics Dep, National Institute of Technology, Kurukshetra-136 119, Email: jkquamara@yahoo.com) : Pre-photoexcitation effects in 75 MeV oxygen ion irradiated kapton-H polyimide. Indian J pure appl Phys 2009, 47(2), 108-13.

The pre-photoexcitation effect measured in the form of dark polarization (I_d) under visible radiation in 75 MeV oxygen ion irradiated (Fluence: 1.8x10¹¹, 3.1x10¹² and 1.8x10^{13 ions/cm2) kapton-H polyimide has been investigated. The dependence of I_d on exposure (ranging from 0 to 10000 W/m2) and the time interval Δf (ranging from 0 to 7 min) between the end of illumination and the outset of the polarizing electric field have been studied at operating temperatures of 80° and 200°C under a biasing field of 240 kV/cm. The variation of I_d with exposure shows a transitory saturation followed by a gradual descent. The band-band transition and the conversion of trapping sites into recombination centers have been held responsible for such behaviour. The ion irradiated samples, in general, show a decrease in I_d as compared to pristine samples. The effect of fluence on I_d is mainly associated with the enhancement of charge trapping density and the charge carrier mobility.}

006115   Sarawadekar R G;Agrawal J P (NO, High Energy Materials Research Laboratory, Pune-411 021) : Nanomaterials in pyrotechnics. Def Sci J 2008, 58(4), 486-95.

Pyrotechnics consist of metallic powders as fuels and different oxidisers which generally have particle size of > 5 μ. The use of nano materials is expected to increase intimate contact between fuel oxidiser, and therefore, development of nano pyrotechnics based on nano fuels oxidizers along with their synthetic routes is considered of great interest. Methods for the preparation of powders of nanometals: aluminium (Al), nickel (Ni), copper(Cu), titanium(Ti), iron (Fe), silver (Ag), and cobalt (Co) and; metallic oxides: molybdenum trioxide (MoO₃), tungsten trioxide (WO₃), iron (III) oxide (Fe₂O₃), copper (I) oxide (Cu₂O), antimony trioxide (Sb₂O₃), nickel oxide (NiO), manganese dioxide (MnO₂), and zirconium dioxide (ZrO₂) along with their characterisation are discussed. Some nano oxidisers such as PbCO₃, Mg(OH)₂, NH₄ClO₄, NH₄NO₃ have also been reported. Further, some nano pyrotechnic formulations Al-MO₃, Al-WO₃, Al-Fe₂O₃, Al-AP, Al-Bi₂O₃, Al-CaO based on nanofuels oxidisers have also been formulated.

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006114   Saravanan P;Gopalan R;Chandrasekaran V (NO, Defence Metallurgical Research Lab, Hyderabad-500 058) : Synthesis and characterisation of nanomaterials. Def Sci J 2008, 58(4), 504-16.

Development of synthesis protocols for realising nanomaterials over a range of sizes, shapes, and chemical compositions is an important aspect of nanotechnology. The remarkablesize-dependent physico-chemical properties of nanoparticles have fascinated and inspired research activity in this direction. Describes some aspects on synthesis and characterization of nanoparticles of metals, metal alloys, and oxides, either in the form of thin films or bulk shapes. A brief discussion on processing of two-phase nanocomposite magnets is also presented.

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006113   Rukmangad A;Aynyas M;Sanyal S P (Physics Dep, Sadhu Vaswani College, Bhopal-462 030, Email: aditi.rukmangad@yahoo.co.in) : Structural and elastic properties of rare-earth nitrides at high pressure. Indian J pure appl Phys 2009, 47(2), 114-8.

The structural and elastic properties of rare earth nitrides (REN) [RE=Tb, Ce] under high pressure have been investigated by using two body inter ionic potential theory with modified ionic charge (Z_m^e) to include Coulomb screening effect. The present theoretical approach has predicted pressure-volume relationship curves which show that TbN and CeN exhibit a NaCl type structure at an ambient pressure and undergo a structural phase transition from NaCl into CsCl phase at 136 GPa and 88 GPa, respectively. The Second order elastic constants (SOECs), Third elastic constants (TOECs) and second order pressure derivatives for these compounds have also been reported. The variation of elastic constants (C₁₁, C₄₄) with pressure is also presented.

006112   Raji Reddy S;Srihari K (Mathematics Dep, Mahathama Gandhi Institute of Technology, Gandipet, Hyderabad, Email: kotagirisrihari@yahoo.com) : Numerical solution of unsteady flow of a radiating and chemically reacting fluid with time-dependent suction. Indian J pure appl Phys 2009, 47(1), 7-11.

The numerical solution of unsteady laminar, boundary layer flow of a viscous incompressible, electrically conducting fluid along a semi-infinite vertical plate, in the presence of thermal and concentration buoyancy effects has been obtained, using implicit finite difference method for velocity, temperature and concentration fields. The results for the velocity, temperature shear stress, Nusselt number and Sherwood-numbers have been obtained and discussed for different flow parameters such as Sc, K_r, Gr, Gm, N_R and Pr. It has been found that an increase in the chemical reaction leads to decrease in the velocity and concentration boundary layer, but, an increase in the thermal radiation increases the velocity and temperature boundary layer. These results are found to be in good agreement with the previous results.

006111   Patra M K;Manzoor K;Manoth M;Negi S C;Vadera S R;Kumar N (NO, Defence Laboratory, Jodhpur-342 011) : Nanotechnology applications for chemical and biological sensors. Def Sci J 2008, 58(5), 636-49.

Recent discoveries indicate that when the materials are brought down to sizes in the range 1-100 nm, these exhibit unique electrical, optical, magnetic, chemical, and mechanical properties. Methods have now been established to obtain the monodisperse nanocrystals of various metallic and semiconducting materials, single-walled and multi-walled nanotubes of carbon and other metallic and non-metallic materials together with organic nanomaterials such as supra-molecular nanostructures, dendrimers, hybrid composites with tailored functionalities. The high surface-to-volume ratio with an added element of porosity makes these highly potential candidates for chemical and biological sensor applications with higher degree of sensitivity and selectivity as compared to their bulk counterparts. Reviews the recent developments and applications of chemical and biological sensors based on nanomaterials of various structural forms.

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006110   Parashar J (Applied Physics Dep, Samrat Ashok Technological Institute, Vidisha-464 001) : Resonant second harmonic generation in a plasma filled parallel plane waveguide. Indian J pure appl Phys 2009, 47(2), 103-7.

A TE mode electromagnetic radiation propagating through plasma filled parallel plane guide in the presence of a density ripple, produces resonant second harmonic radiation in the TM mode. The ripple provides the phase matching. The required density ripple wave number increases with the plasma density. The amplitude of the ripple also needs to be non-uniform to produce net time average second harmonic power. The power conversion efficiency of harmonic scales is ω₁^-6, the frequency of the pump.

006109   Panwara O S;Khana M A;Basu A;Kumar S;Kumar S (Plasma Processed Materials Group, National Physical Laboratory, New Delhi-110 012, Email: ospanwar@mail.nplindia.ernet.in) : Analysis of dielectric constants to determine sp<. Indian J pure appl Phys 2009, 47(2), 141-8.

The carbon bonding ratio and optical properties have been studied by spectroscopic ellipsometry of as grown tetrahedral amorphous carbon (ta-C) films, deposited using an S bend filtered cathodic vacuum arc (FCVA) process. First, the carbon bonding ratio in ta-C films has been estimated from imaginary part of dielectric constant (ε₂) spectra obtained by spectroscopy ellipsometry. A method has been developed to find out the fractions of sp³and sp² bonded carbon atoms from the Wemple-Didomenico plot. Second, the effect of varying negative substrate bias on the optical properties and sp³/sp² ratio of as-grown ta-C films has been made. The values of the optical constants evaluated are found to increase with the increase of the negative substrate bias in the as-grown ta-C films but the values of sp³/sp² ratio and the optical band gap (E_g) evaluated increase up to -200 V substrate bias and beyond -200 V substrate bias the values of sp3/sp2 ratio and E_g decrease. Application of substrate bias is, thus, found to increase the sp3 bonding and E_g up to -200V substrate bias and beyond -200V substrate bias there is reversal of the trend.

006108   Oza A T;Vinodkumar P C (Physics Dep, Sardar Patel University, Vallabh Vidyanagar388 120, Email: ajayozat@yahoo.com) : Theory of high pressure studies on low-dimensional conductors. Indian J pure appl Phys 2009, 47(1), 32-42.

The behaviour of the experimentally observed electrical resistivity of organic semiconductors, single crystals of poly-iodide chain complexes and the nickel organo metallic compounds under pressure have been explained theoretically by considering various physical processes related to these compounds. The pressure dependence of the various transport parameters such as the mobility, effective mass of the charge carriers and the mean collision time etc are also deduced from the experimental behaviour through the theoretical modeling.

006107   Om Kumar;Yamini Singh;Rao V K;Vijayaraghavan R (NO, Defence Research and Development Establishment, Gwalior-474 002) : Carbon nanotubes: detection of chemical and biological warfare agents. Def Sci J 2008, 58(5), 617-25.

Discovery of carbon nanotubes has great impact on the development of newer methodologies and devices useful for the analysis of various types of chemicals. The functionalisation of CNTs with biomolecules related to chemical and biological warfare agents makes these useful for the detection of these agents. The detection sensitivity can be increased manyfold. Various types of chemical and biological sensors were developed using various type of carbon nanotubes as well as nano particles of different metals.

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006106   Narulkar V V;Prakash S;Chandra K (NO, Institute of Technology and Management, Gurgaon, Haryana) : Effects of temperature on tribological properties of Al₂O₃-TiO₂ coating. Def Sci J 2008, 58(4), 582-87.

Al₂O₃-TiO₂ coating for turbine blades is being used since long. During the last decades, a large number of papers have been published, but work on property assessment of Al₂O₃-TiO₂ coating on rotating component from tribological point of view is very less. Assesses the wear behaviour of Al₂O₃-TiO₂ coating on inconel 601. The Al₂O₃-TiO₂ coating on inconel 601 is deposited by plasma spray process. The SEM results show that above 300°C, the friction coefficient decreases due to softening of coating material. The wear rate increases with increase in temperature. The coating showed brittle fracture at higher temperature. Other test results have shown the drastic changes in property due to load and temperature.

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006105   Mukul Kumar;Ando Y (NO, Meijo University, Shiogamaguchi, 1-501, Tempaku-ku, Nagoya 468-8502, Japan) : Gigas growth of carbon nanotubes. Def Sci J 2008, 58(4), 496-503.

Exceptionally high yield of carbon nanotubes (CNTs) has been achieved by chemical vapour deposition (CVD) of camphor over zeolite support. A simple 30 min CVD of 12 g camphor over Fe-Co-impregnated zeolite at 650°C in an academic laboratory setup, yields 6 g multiwalled CNTs of dia ~10 nm with an as-grown purity of ~88 per cent. Owing to the enormous CNT growth, the zeolite bed inflates by 1000 wt per cent and 10,000 vol percent. Camphor-to-CNT production efficiency is 50 per cent and net carbon-to-CNT conversion efficiency is 61 per cent. These figures are incomparably higher than that of any CNT precursor by any method. Hence it is called `gigas growth'. The technique greatly complies with the principles o fgreen chemistry, and thus sets an example of an environment-friendly nanotechnology.

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006104   Mukhopadhyay K;Kanik Ram;Bhasker Rao K U (NO, Defence Materials and Stores Research and Development Establishment, Kanpur-208 013) : Carbon nanotubes and related structures. Def Sci J 2008, 58(4), 437-50.

Carbon nanotubes have attracted the fancy of many scientists worldwide. The small dimensions, strength, and the remarkable physical properties of these structures make them a unique material with a whole range of promising applications. The structural aspects, the advantages and disadvantages of different for their procedures synthesis, the qualitative and quantitative estimation of carbon nanotubes by different analytical techniques, the present status on their applications as well as the current challenges faced in the application field, national, in particular DRDO-DMSRDE status, and interest in this field, have been discussed.

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006103   Manocha S;Patel N;Manocha L M (NO, Sardar Patel University, Vallabh Vidyanagar-388 120) : Development and characterisation of nanoclays from Indian clays. Def Sci J 2008, 58(4), 517-24.

Indian clays are known for their smecticity. One such clay sample collected from Bhuj (Gujarat) was characterised and modified by successive sedimentation processes for different time intervals. The non-plastic components of clay, viz., quartz, illite, iron oxide, CaO, MgO, and organic matter were removed in different steps, as the heavy impurities in the clay-water suspensions, settle down during sedimentation. The free iron oxide present in clay suspension was reduced by giving sodium citrate-bicarbonate-dithionite treatment and iron content was further reduced from 12-15 per cent to 5-7 per cent respectively. The organic matter was removed by sodium cetate-₂O₂ treatment. The modified clay so obtained was characterised by thermal analysis, FTIR, and XRD, SEM and TEM. The cation exchange capacities of original and modified clays were determined both by methylene blue method and ammonium acetate ethod. The cation exchange capacity is found to enhance from 120-130 meq/100 g to 135-145 meq/100 g. Using the above procedure, 92 percent smecticity was obtained. Organophilisation of purified clay(smectite) was carried out by intercalation with alkyl ammonium salt. The XRD analysis showed enhancement of interlamellar spacingfrom 1.294 nm to 2.855 nm.

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006102   Lal K;Singh C P;Chauhan R S (Physics Dep, R. B. S. College, Agra-282002, Email: rvschauhan@yahoo.com) : Analysis of high pressure equations of state for solids. Indian J pure appl Phys 2009, 47(1), 28-31.

Four equations of state for solids with adjustable parameter K≈8, the pressure derivative of bulk modulus at infinite pressure have been studied. These equations are the Keane EOS, the Stacey reciprocal K≈ - EOS, the generalized Rydberg EOS and the Roy-Roy EOS. It is found that the Keane EOS and the Stacey EOS are very similar requiring K≈_∞ to be considerably larger than 5/3. The generalized Rydberg EOS yields satisfactory results with a value of K≈_∞ = 5/3. For the Roy-Roy EOS, K≈_∞ has been found to remain between 5/3 and 2. This has been demonstrated by calculating P, K and K≈ for hcp iron at different compressions.

006101   Kumaran V (Chemical Engineering Dep, Indian Institute of Science, Bangalore-560 012, Email: kumaran@chemeng.iisc.ernet.in) : Josiah willard gibbs. Resonance 2007, 12(7), 4-11.

The foundations of classical thermodynamics, as taught in textbooks today, were laid down in nearly complete form by Josiah Willard Gibbs more than a century ago. Presents a portrait of Gibbs, a quiet and modest man who was responsible for some of the most important advances in the history of science.

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006100   Kumar A;Agarwal P B;Sachin Kumar;Joshi B C; Sharma A K;Chander H (NO, Central Electronics Engineering Research Institute, Pilani-333 031) : Low-pressure chemical vapour deposition of silicon nanoparticles: synthesis and characterisation. Def Sci J 2008, 58(4), 550-58.

Semiconductor nanostructures such as quantum wells, quantum wires or quantum dots exhibit superior properties in comparison to their bulk forms. Quantum dots are described as zero-dimensional electron gas system, as carriers are confined in all the three directions. Density of states is discrete function of energy. Allowed energy spectrum is discrete like in an atom. Energy band gap is broadened due to carriers confinement. Semiconductor quantum dots exhibit typical coulomb blockade characteristic which is exploited for development of new generation of nanoelectronic devices namely single-electron transistor, memories, etc, whose operation depends on quantum mechanical tunneling of carriers through energy barriers. These semiconductor nanostructures emit light in visible range upon excitation by optical means. In recent years, research has been focused on different nano-scale materials; metals (Au, Ag,Fe, Mn, Ni), metal oxides (SnO₂, ZnO₂), compound semiconductors (GaAs, GaAlAs, CdSe, CdS, GaN), and elemental semiconductors (silicon and germanium). As silicon is the most favoured material in the established integrated circuits manufacturing technology, research is being done for controlled synthesis and characterisation of Si nanoparticles. The Si nanoparticles have been synthesised on oxide and nitride layers over Si substrate by IC technology compatible low-pressure chemical vapour deposition technique. Atomic force microscopy (AFM) characterisation has been extensively carried out on the samples. It is shown that the tip radius and shape of tip lead to less accurate estimate of the actual size. The AFM images have been evaluated based on the real surface topography and shape of the tip. Photoluminescence (PL) studies have been performed to characterise the samples. The PL measurements showed visible light emission from synthesised silicon nanoparticles.

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006099   Kukreti A;Ashok Kumar;Naithani U C (Physics Dep, Garhwal University, Pauri Campus, Pauri(Garhwal), Uttarakhand-246 001) : Electric field dependence of specific heat in Ba_xSr_1-xTiO₃ ferroelectric perovskites. Indian J pure appl Phys 2009, 47(1), 43-8.

The electric field dependence of the specific heat of an anharmonic Ba_xSr_1-xTiO₃ ferroelectric crystal has been calculated in its paraelectric phase from the Silverman-Joseph Hamiltonian augmented with fourth order phonon co-ordinates using double time Green's functions. The electric field dependent soft mode contribution to the specific heat is described by appropriate Einstein terms. The variation of specific heat with temperature defect and electric field has been discussed. The specific heat decreases with increasing external electric field and increases with increasing temperature, in agreement with previous results. In the vicinity of Curie temperature, the Cochran soft mode is held responsible for the anomalous behaviour of specific heat.

006098   Khanna V K (NO, Central Electronics Engineering Research Institute, Pilani-333 031) : Nanoparticle-based sensors. Def Sci J 2008, 58(5), 608-16.

Nanoparticles exhibit several unique properties that can be applied to develop chemical and biosensors possessing desirable features like enhanced sensitivity and lower detection limits. Gold nanoparticles are coated with sugars tailored to recognise different biological substances. When mixed with a weak solution of the sugar-coated nanoparticles, the target substance, e.g., ricin or E.coli, attaches to the sugar, thereby altering its properties and changing the colour. Spores of bacterium labeled with carbon dots have been found to glow upon illumination when viewed with a confocal microscope. Enzyme/nanoparticle-based optical sensors for the detection of organophosphate (OP) compounds employ nanoparticle-modified fluorescence of an inhibitor of the enzyme to generate the signal for the OP compound detection. Nanoparticles shaped as nanoprisms, built of silver atoms, appear red on exposure to light. These nanoparticles are used as diagnostic labels that glow when target DNA, e.g., those of anthrax or HIV, are present. Of great importance are tools like gold nanoparticle-enhanced surface-plasmon resonance sensor and silver nanoparticle surface-enhanced portable Raman integrated tunable sensor. Nanoparticle metal oxide chemiresistors using micro electro mechanical system hotplate are very promising devices for toxic gas sensing. Chemiresistors comprising thin films of nanogold particles, encapsulated in monomolecular layers of functionalised alkanethiols, deposited on interdigitated microelectrodes, show resistance changes through reversible absorption of vapours of harmful gases. Reviews the state-of-the-art sensors for chemical and biological terror agents, indicates their capabilities and applications, and presents the future scope of these devices.

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006097   Kannappan V;Askar Ali S J;Abdul Mahaboob P A (Postgraduate and Research Department of Chemistry, Presidency College (Autonomous), Chennai-600 005) : Determination of stability constants of charge transfer complexes of iodine monochloride and certain ethers in solution at 303 K by ultrasonic method. Indian J pure appl Phys 2009, 47(2), 97-102.

Ultrasonic velocities (U), densities (ρ), and coefficient of viscosities ((η) have been measured for solutions containing iodine monochloride (ICl) and one of the following ethers in the equimolar concentration in the range 0.001-0.01M at 303 K. Diphenyl ether, 4-chloroanisole, anisole and 1,4-dioxane are used as donors. Dichloromethane, chloroform, carbon tetrachloride and n-hexane have been used as solvents. Acoustical parameters such as adiabatic compressibility ((β), absorption coefficient ((α/f²), internal pressure ((π_I) and cohesive energy (CE) values are calculated from the measured values of U, (ρ and (η. The trend in the acoustical parameters establishes the formation of charge transfer complexes between iodine monochloride (acceptor) and ethers (donors). The stability constants (K) are calculated for these complexes. The free energy changes (ΔG) for the formation of these complexes are also calculated from K values. Attempt has been made to correlate the formation constants with polarizability, dielectric strength and dipole moment of the donor and solvent molecules. The free energy of activation (ΔG ^#) and viscous relaxation time (τ) are found to be almost constant for these complexes indicating the formation of similar charge transfer complexes in these systems.

006096   Gunasekaran S;Sailatha E;Seshadri S;Kumaresan S (Spectrophysics Research Lab, Pachaiyappa's College, Chennai-600 030) : FTIR, FT Raman spectra and molecular structural confirmation of isoniazid. Indian J pure appl Phys 2009, 47(1), 12-8.

Isoniazid (INH) is a first-line anti-tuberculous medication used in the prevention and treatment of tuberculosis with molecular formula C₆H₇N₃O. The FTIR and FT Raman spectra of Isoniazid have been recorded in the region 4000 -400cm^-1 and 3500 - 50 cm^-1, respectively. A detailed vibrational analysis has been made on the fundamental modes of vibration. The normal coordinate analysis has been carried out for INH following the Wilson's FG matrix method on the basis of C₁ point group symmetry. A systematic set of potential constants has been evaluated using the method of kinetic constants and the evaluated potential constants have been compared with those of related molecules. To check whether the chosen set of vibrational frequencies contribute maximum to the potential energy associated with the normal coordinates of the molecule, potential energy distribution (PED) has been evaluated.

006095   Ghosal P;Sarkar R;Muraleedharan K;Chaturvedi P;Rawat J S B S;Harsh (NO, Defence Metallurgical Reserch Lab, Hyderabad-500 058) : Electron microscopy of multi-walled carbon nanotubes for display devices application. Def Sci J 2008, 58(5), 655-63.

Opportunity of creating and tailoring unprecedented and beautifully symmetric 3-D structures has propelled the science of carbon nanotubes to become one of the highly promising areas in the field of nanotechnology. The unique properties of carbon nanotubes have promoted research in the fabrication of devices composed of carbon nanotubes and in other applications. Characterisation tools are crucial in the study of these emerging materials to evaluate their full potential in applications and to comprehend their basic properties. The aim of this study was electron microscopy characterisation of the carbon nanotubes synthesized to fabricate display devices. Both thermal chemical vapour deposition (CVD) and plasma enhanced chemical vapour deposition routes were used to synthesise patterned and aligned carbon nanotubes. Several batches of CNTs were produced by varying the process parameters such as growth temperature, gas ratio, duration of growth, catalyst condition, etc. Characterisation of these CNTs have been done using scanning electron microscope, transmission electron microscope, high resolution transmission electron microscope, and electron energy loss spectrum. Structure, uniformity, chemistry, diameter, length, number of walls of the multi-walled nanotubes were characterised using various electron microscopes, which finally lead to the production of the display devices using CNTs.

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006094   Chaturvedi P;Verma P;Anand Singh;Chaudhary P K;Harsh;Basu P K (NO, Solid State Physics Laboratory, Timapur, Delhi-110 054) : Carbon nanotube-purification and sorting protocols. Def Sci J 2008, 58(5), 591-9.

Carbon nanotubes (CNTs) have shown extraordinary thermal, electrical, and electronic properties. Electronic properties of CNT are very sensitive to its diameter and chirality, making it metallic mechanical, or semiconducting, depending upon its chiral vector. The extraordinary properties of CNTs have led to demonstration of several applications but commercial realisation of these devices require consistent quality of CNTs, and these should be free of any impurity. For development of electronic devices, CNTs should not just be pure but also of similar length, diameter, and electronic behaviour. Such demanding requirements need development of elaborate purification and sorting protocols. A brief review of the existing technologies and the research done is presented.

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006093   Chandrasekhar M;Jagadeesh Chandra S V;Uthanna S (Physics Dep, Sri Venkateswara University, Tirupati-517 502, Email: uthanna@rediffmail.com) : Characterization of bias magnetron sputtered tantalum oxide films for capacitors. Indian J pure appl Phys 2009, 47(1), 49-53.

Tantalum oxide films have been deposited by sputtering of tantalum target in an oxygen partial pressure of 2x10^-4 mbar under various substrate bias voltages in the range from 0 to -150 V on glass and silicon substrates held at room temperature. The influence of substrate bias voltage on the chemical binding configuration, crystallographic structure, electrical and dielectric properties has been systematically studied. The X-ray photoelectron spectroscopic studies reveal that the films are stoichiometric. The X-ray diffraction and Fourier transform infrared spectroscopic studies indicate that the films deposited under unbiased condition are amorphous in nature, whereas those formed at substrate bias voltages ≥ -75 V are polycrystalline with orthorhombic β-phase. The electrical and dielectric properties of Ta₂O₅ films have been studied on the metal / insulator / metal (MIM) structure of Al/Ta₂O₅/Al. The dielectric constant of the films formed at unbiased condition has been found to be 15, while for those prepared at higher substrate bias voltage of -150 V has been found to be 23 due to the improvement in the crystallinity and packing density. The voltage - current measurements on the MIM structure indicate the decrease of leakage current density with the increase of substrate bias voltage.

006092   Bhattacharyya S R;Pal A K (NO, , Jadavpur University, Email: msakp2002@yahoo.co.in) : Grain boundary scattering in silicon doped polycrystalline gallium nitride films prepared by rf sputtering. Indian J pure appl Phys 2009, 47(2), 125-33.

Silicon doped polycrystalline gallium nitride films have been deposited at temperatures ranging from 300 to 623 K on fused silica and silicon substrates by radio frequency sputtering technique. The films are characterized by optical measurements while the microstructural information is obtained from scanning electron microscopy and atomic force microscopy. X-ray photoelectron spectroscopy studies indicate compositional information in these films. The bonding environment in the film has been revealed from Fourier transformed infrared studies. Grain boundary parameters like density of trap states and barrier height are also evaluated.

006091   Bari A R;Shinde M D;Deo V;Patil L A (Nanomaterials Research Lab, Physics Dep, Pratap College, Amalner-425 401, Email: plalachand_phy_aml@yahoo.co.in) : Effect of solvents on the particle morphology of nanostructured ZnO. Indian J pure appl Phys 2009, 47(1), 24-7.

Nanostructured ZnO thin films have been prepared by simple sol-gel dip coating technique. Zinc acetate, ammonium hydroxide, sodium hydroxide and ethanol are used as precursors. As prepared nanostructured films are annealed at 500°C and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX). The shapes of the particles are found spherical in nature having particle sizes in the range of 30 nm. With the change of solvent from ammonium hydroxide to sodium hydroxide, particle shapes have been changed from spherical to nanowires having average diameter of 60 nm.

005122   Singh A;Gosavi S W;Malek C K;Kulkarni S K (DST Unit on Nano Science, Physics Dep, Pune Univ, Pune-411 007, Email: skk@physics.unipune.ernet.in) : Soft lithography : inexpensive route for mass scale nanopatterning. Natn Acad Sci Lett 2007, 30(1-2), 15-30.

Soft lithography is a technique of replicating the patterns with feature sizes ranging from a few nanometers to micrometers. It was originally developed by Whitesides et al. and has gained tremendous attention due to its ease of operation, cost effectiveness, possibility of patterning non-planar surfaces etc. Soft lithography can be performed in a variety of ways like Micro Contact Printing (μCP), Micro Transfer Moulding (μTM), Micro Moluding in Capillaries (MIMIC), Replica Moulding (REM) and Solvent Assisted Micromoulding (SAMIM).

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005121   Reddaiah P;Prasada Rao D R V (Mathematics Dep, Gates Institute of Technology, N.H.-7, Gootyananthapuram, Village, GOOTY-515 401, Email: reddaiah123@yahoo.co.in) : Finite element analysis of convective flow through a porous medium in a rectangular duct. Bull pure appl Sci-Sect E 2008, 27(1), 229-42.

In this paper, analyze another the free convective flow and heat transfer in a heat generating viscous fluid in a saturated porous medium enclosed in a rectangular duct. The heat flux is maintained constant on the top and bottom walls of the duct The temperature on the vertical walls is taken as a power function of distance along the wall. The Darcy model is used for the momentum transport Making use of the incompressibility the stream function is defined and the governing non-dimensional momentum and energy equations are derived in terms of the stream function and temperature. The Galerkin finite element method with triangular elements is employed to obtain iterative solution of the said coupled non-inear equations. The temperature fields at different horizontal and vertical levels are obtained and their behavior is investigated for variations in the governing parameters. The local rate of heat transfer along the side wall is obtained and its variations for different parameters are discussed.

4 tables, 17 ref

005120   Karunakaran M;Gomathi S (Physics Dep, Rev. Jacob Memorial Christian College, Ambilikkai-624 612) : Photosensitivity of cadmium doped nickel oxide thin film. Int J chem Sci 2007, 5(3), 1301-5.

The film science has received tremendous attention in the recent years. Especially after the world war because of numerous applications of films in diverse field such as electronic industries, military, weapon system, space system, solar energy utilization and also as optical and superconducting film materials. A thin film has its dimensions in the microscopic scale. Its thickness is negligibly small, about six orders less than the order dimensions that is usually of the order of a few angstroms. The devices that resulted in the emission of electrons from a metallic surface when light waves are incident on the surface are called photoelectric devices. The apparatus used were measured in the enclosed air medium. The cadmium doped nickel oxide film is connected with the Keithley electrometer. The light sensitivity of the film and the resistance of the film at various intensity of light was measured for various doping concentration. The resistance of the film was found to increase with doping concentration and also with decrease in light intensity.

2 illus, 2 tables, 5 ref

004159   Vyas P;Thakur K (S.O.S. in Electronics, Pt. Ravi Shankar Shukla Univ, Raipur-492 010) : Micro controller based instrumentation system for study of solar cell. Acta Cienc Indica-Phys 2008, 34(2), 325-7.

Deals with battery powered, mobile, sophisticated, compact standalone microcontroller based measurement instrumentation system, which is used to simplify the analysis of the effect of atmospheric temperature into various solar cells. These measured values are displayed on the front panel and also sent to PC through an RS-232 serial port for data logging and display. To get accurate and smooth plotting of I-V curve of solar cell over this parameter automated system instead of manually operated system is necessary. So this requires a specific controller, analogue sensors and jnterface unit to satisfy stated objectives, Design and implementation scheme for the developed system is discussed. The system contain Atmel 89C52, temperature sensor, interface unit to connect to PC. The collected data will be useful to find suitable circumstances to enhance the performance.

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004158   Srivastava S K;Parasai M (Physics & Electronics Dep, Government Post Graduate College, Ambikapur-497 001) : Laboratory evaluation of scattering coefficients of dust particles in sand and dust storm. Acta Cienc Indica-Phys 2008, 34(2), 233-7.

An attempt has been made for estimation of Scattering coefficients of dust particles on the propagation of microwave and millimeter waves. The constituents of dust in storm are taken as sand, silt and clay particles. The scattering coefficients of sand, silt and clay particles have been measured at X Band frequency both for vertical and horizontal polarization. It is found that scattering coefficients are larger for vertical polarization in comparison to horizontal polarization. The shape of particle are taken as spherical as well as non-spherical.

3 tables, 6 ref

004157   Sreenivasulu A;Prasad T N V K V;Buddhudu S (Physics Dep, Sri Venkateswara Univ, Tirupati-517 502, Email: profsb_svuniv@hotmail.com) : Optical analysis of RE<. Proc Indian Natn Sci Acad 2008, 74(1), 1-4.

Ferroelectric materials Ba_0.95RE_0.05TiO₃ (RE=Eu³⁺ Sm³⁺ & Dy³⁺) containing certain rare-earth ions as the luminescent ions were prepared by a conventional solid state method. Structural analysis of these materials has been carried out by using both XRD and FTIR spectral measurements. By measuring the excitation, emission spectra and lifetimes of the prominent emission bands, luminescence performance of these optical materials has been investigated.

8 illus, 1 table, 22 ref

004156   Sree Bala Devi B (Anthropology Dep, Hyderabad Univ, Hyderabad, Andhra Pradesh) : Attitudes towards old age: a study of the self-image of aged. Indian J Gerontol 2007, 21(3), 294-303.

Ageing occurs in a societal context, ranging form the micro scale of the family to the macro scale of the society. This context includes the attitudes, stereotypes and age norms, which determine age appropriate behavior for the aged (Social-Image). Further, the aged have, an image of them selves (Self-image) and an image of how they feel, the 'others', in the society perceive them (Image of Social Image). The societal attitudes shape the social behavior towards the aged. The interactions of the aged in the social environment, result in the self-image of the aged being reinforced by the social-image. The present paper is an attempt to study the "self-image" of the aged, their "image of the social image" and the influence of "social image" on their "self- image".

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