Indian Journal of Pure and Applied Physics

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Volume 46

                             Number 8

                                       AUGUST 2008

 

CODEN : IJOPAU 46 (8) 531- 602

                                                            ISSN : 0019-5596

 

 

 

CONTENTS

 

Atomic and Molecular Physics

 

 

New approach for the measurement of glass transition temperature of a polymer

535

M  S  Gaur*, Prashant Shukla, R  K  Tiwari, Anju Tanwar1 & S  P  Singh

 

 

Physics of Gases, Plasmas and Electric Discharges

 

 

Plasma treatment at low pressure for the enhancement of wettability of polycarbonate

540

D P Subedi*, D K Madhup, K Adhikari1 & U M Joshi

 

 

Condensed Matter:Structural , Mechanical and Thermal Properties

 

 

Experimental and predicted viscosities of binary mixtures of benzene and chloroalkanes at different temperatures using Isdale’s group contribution method

545

Anwar Ali*a, Mohammad Tariqb & Firdosa Nabia

 

Excess volumes and deviation in viscosities of binary mixtures of o-dichlorobenzene and o-chlorophenol with di-isopropyl ether, 1.4-dioxan, diphenyl ether and t-butylmethyl ether

552

R N Shelara, V S Savaleb, R Y Borseb, Mehdi Hasanc & A B Sawant* c

 

Synthesis and characterization of CdO and CdS nanoparticles        

561

K Manickathai* , S Kasi viswanathan** & M Alagar*

 

Performance criteria on different pressure ratios of an irreversible modified complex Brayton cycle

565

S   K   Tyagi1,2, Shengwei Wang1 & S   R   Park2

 


Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties


 

Superconducting transition temperature in the co-doped Y0.95Pr0.05Ba2(Cu1-xMnx)3O7-δ superconductors for x ≤ 0.02

575

Bhasker Gahtori*, R Lal & S K Agarwal ,Anirban Das1,  Tirthankar Chakraborty2& Ashok Rao3

 

 

Electric field  dependent microwave losses   in BaxSr1-xTiO3 perovskites                       

580

Ashish Kukreti*, Ashok Kumar &  U C Naithani

 

 

Role of binding energy in the generation of photocurrent in bulk heterojunction organic materials

588

S K Sharma, Chandra Bothra & G D Sharma

 

 

Interdisciplinary Physics and Ralated Areas of Science and Technology

 

 

Design, fabrication and characterization of microstrip square patch antenna array for x-band applications

593

Deepak Sood*, Gurpal Singh**, Chander Charu Tripathi, Suresh Chander Sood  &       Pawan Joshi

 

 

*The corresponding author has been indicated by (*) mark in case of papers with more than one author.

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, August 2008, pp. 535-539

 

New approach for the measurement of glass transition temperature of polymer

M S Gaur*, Prashant Shukla, R K Tiwari, Anju Tanwar1 & S P Singh2

Hindustan College of Science and Technology, Farah, Mathura (U P)

1 Govt R D Girls College, Bharatpur (Rajasthan)

2 National Physical Laboratory, New Delhi 110 012

*E-mail: mulayamgaur@rediffmail.com, Fax: +91-565-2763366

Received 19 February 2007; revised 16 January 2008; accepted 6 May 2008

Global thermally stimulated discharge current (TSDC) and partial thermally stimulated discharge current (PTSDC) spectra were recorded to investigate the molecular motions at glass transition temperature (Tg) level in both sided vacuum aluminized 30 µm thick poly (methyl methacrylate) samples. The calculated values of charge released, relaxation time and activation energy correspond to α and β relaxation processes. The TSDC peak occurred at a temperature, which is close to Tg of the polymer. This temperature is in agreement with the Tg determined using DSC technique.

Keywords: TSDC, DSC, PTSDC, α-relaxation, β-relaxation, Poly (methyl methacrylate), Glass transition temperature

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, August 2008, pp. 540-544

 

Plasma treatment at low pressure for the enhancement of wettability of polycarbonate

D P Subedi*, D K Madhup, K Adhikari1 & U M Joshi

Department of Physics, Kathmandu University, Dhulikhel, Nepal

1.Central Department of Physics, Tribhuvan University, Kathmandu , Nepal

Received 24 April 2007; revised 4 January 2008; accepted 12 May 2008

The dc glow discharge plasma at low pressure was used for the treatment of polycarbonate surface to investigate the improvement in wettability. The effect of treatment time, applied power and sample- electrode distance on wettability and etching was studied. The surface energy of the sample was found to increase from 29.73 to 64.69 mJ/m2 with 40s of treatment time. The results showed that wettability and etching of the sample depend strongly on treatment time, applied power and distance from the electrode. The relation for the wettability of the sample as a function of the sample-electrode distance has been found. It was found that dc glow discharge produced at a low pressure air can effectively etch a polycarbonate sample at the rate in the order of 10-9 g/cm2/s. The stability of the modified surface by measuring the contact angle at different storage time has been investigated.

Keywords: Glow discharge, Polycarbonate, Contact angle, Surface energy, Wettability , Etching.

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, August 2008, pp. 545-551

 

Experimental and predicted viscosities of binary mixtures of benzene and chloroalkanes at different temperatures using Isdale’s group contribution method

Anwar Ali*a, Mohammad Tariqb & Firdosa Nabia

aDepartment of Chemistry, Jamia Millia Islamia (Central University), New Delhi 110 025

bLaoboratory of Molecular Thermodynamics;
Instituto de Tecnologia Quimicae Biologia, Universidade de Nova De Lisboa, Oeiras, Portugal

Received 7 November 2007; revised 23 April 2008; accepted 15 May 2008

Experimental viscosities, h of pure benzene, 1,2-dichloroethane (DCE), 1,1,2,2-tetrachloroethane (TCE) and those of their binary mixtures, having benzene as a common component, have been measured over the whole composition range at 298.15, 303.15, 308.15, 313.15 and 318.15 K. The experimental h data were then fitted to standard polynomial against composition. Using h values, the deviations in viscosities,  h , excess Gibbs free energies of activation of viscous flow, ∆G*E, entropies, ∆S* and enthalpies, ∆H* of activation of viscous flow have been calculated. The sign and magnitude of these parameters were found to be sensitive towards interactions prevailing in the studied systems. Further, the excess molar volumes, VE were calculated using data for both the binary mixtures. Moreover, Grunberg–Nissan and Isdale’s group contribution methods have been used to calculate the viscosities of mixtures and the results were discussed in terms of average percentage deviations (APD) in experimentally and theoretically calculated viscosities.

Keywords: Viscosities, Interactions, Liquid mixtures, Correlations, Group contribution

 

Indian Journal of Pure & Applied Physics

Vol. 46, August 2008, pp. 552-560

 

Excess volumes and deviation in viscosities of binary mixtures of
o-dichlorobenzene and o-chlorophenol with di-isopropyl ether, 1.4-dioxan, diphenyl ether and t-butylmethyl ether

R N Shelara, V S Savaleb, R Y Borseb, Mehdi Hasanc & A B Sawant* c

aDepartment of Physics, Arts, Science & Commerce College,  Dist Nashik, Maharashtra  423 204

bDepartment of Electronics, cP G  Department of  Chemistry, M S G  College,  Dist  Nashik, Maharashtra  423 105

E-mail: *absawant@rediffmail.com

Received  4 October 2007; revised 9 May 2008; accepted 5 June 2008

The densities and viscosities of binary mixture of o-dichlorobenzene and o-chlorophenol with d-isopropyl ether, 1.4-dioxan, diphenyl ether and t-butyl methyl ether have been measured at atmospheric pressure and in the temperature range 303-313K at the interval of 5K. The data have been utilized to compute the excess volumes and deviation in viscosities. The results have been interpreted in terms of molecular interactions existing between the components of the mixtures.

Keywords: Excess molar volume, Viscosity deviation , o-Dichlorobenzene,  o-Chlorophenol, Ethers 

 

Indian Journal of Pure & Applied Physics

Vol. 46, August 2008, pp. 561-564

 

Synthesis and characterization of CdO and CdS nanoparticles

 

K Manickathai* , S Kasi Viswanathan** & M Alagar*

*Department of Physics, Ayya Nadar Janaki Ammal College, Sivakasi 626 123

**Department of Physics, Indian Institute of Technology Madras, Chennai 600 036

Received 5 July 2007; revised 5 March 2008; accepted 13 May 2008

Cadmium oxide and cadmium sulphide particles in the nanometer size regime have been synthesized using chemical routes. CdO nanoparticles are prepared by using ethylene glycol as a capping agent and CdS nanoparticles were prepared with H2S gas. Variety of techniques like X-ray diffraction (XRD), UV-Vis absorption spectroscopy and Scanning Electron Microscopy (SEM) are used to carry out structural characterization of the nanoparticles. The optical band gap of these materials has been determined in order to establish a relationship between energy band gap of bulk and nanomaterials.

Keywords: Nanoparticles, Cadmium oxide, Cadmium sulphide

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, August 2008, pp. 565-574

 

Performance criteria on different pressure ratios of an irreversible modified complex Brayton cycle

S K Tyagi1,2*,  Shengwei Wang1 & S R Park2

1Department of Building Services Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong

2Unutilized & Geothermal Energy Center, Korea Institute of Energy Research, PO Box 103, Yuseong, Daejeon, 305-343, South Korea

Received 15 January 2007; revised 19 June 2007; accepted 3 January 2008

The irreversible cycle model of a regenerative modified complex Brayton cycle has been established for the finite heat capacities of external reservoirs. The power output and efficiency have been optimized with respect to the cycle temperatures and the optimum performance parameters are calculated for a typical set of operating condition. It is found that there are optimal values of the intercooling, reheat and cycle pressure ratios at which the cycle attains the maximum performance. The optimal performance parameters are also found to be increasing function of the effectiveness of different heat exchangers, components efficiency and the heat capacitance rates of the external fluids, while it is found to be reversed in the case of the working fluid heat capacitance rate. The optimum operating parameters, the intercooling, reheat and cycle pressure ratios etc corresponding to the different performance parameters are obtained and discussed in detail. The results obtained here are general and some of the important conclusions in the relevant references can be obtained directly from this paper.

Keywords: Modified complex Brayton cycle, Intercooling,  Isothermal heat addition, Regeneration, Irreversibility

 

Indian Journal of Pure & Applied Physics

Vol. 46, August 2008, pp. 575-579

 

Superconducting transition temperature of co-doped
Y0.95Pr0.05Ba2(Cu1-xMnx)3O7-δ superconductors for x ≤ 0.02

Bhasker Gahtori*, R Lal & S K Agarwal

Superconductivity Division, National Physical Laboratory, New Delhi 110 012

and

Anirban Das1, Tirthankar Chakraborty2& Ashok Rao3

1Sikkim Manipal Institute of Technology, Sikkim

2Department of Electronics and Telecommunication Engineering,

Jadavpur University, Kolkata

3Manipal Institute of Technology, Manipal

*E-mail: bhaskergahtori@yahoo.co.in

Received 4 March 2008; accepted 5 June 2008

Values of the superconducting transition temperature Tc extracted from the resistivity and ac susceptibility of Y0.95Pr0.05Ba2(Cu1-xMnx)3O7-δ (x ≤ 0.02) are found to follow the same qualitative variation with the Mn content. Both lead, in particular, to lower Tc for the x=0.005 sample than those of the x=0.0, 0.0075 and 0.01 samples. Comparing Tc with difference of resistivities with and without Pr for various x, it has been argued that electronic effects dominate over the potential scattering in suppressing Tc below x=0.02. Superconducting volume fraction fg (as deduced through imaginary part χ″ of the ac susceptibility at the peak temperature) when considered in conjunction with the average grain size for the x=0.005 sample, indicates that the smaller size of the grains in x=0.005 sample leads to stronger fluctuations. This is an additional source for the larger Tc degradation in the x=0.005 sample.

Keywords: Superconductors, Y0.95Pr0.05Ba2(Cu1-xMnx)3O7-δ

  

Indian Journal of Pure & Applied Physics

Vol. 46, August 2008, pp. 580-587

 

Electric field dependent microwave losses in BaxSr1-xTiO3 perovskites

Ashish Kukreti*, Ashok Kumar &  U C Naithani

Department of Physics, Garhwal University, Pauri Campus , Pauri(Garhwal), Uttarakhand, 246 001

*E-mail: ashishkukreti07@gmail.com

Received 29 January 2008, revised 7 May 2008; accepted 6 June 2008

The electric field dependent microwave loss of anharmonic BaxSr1-xTiO3  perovskites has  been calculated in its para electric phase from the Silverman Joseph Hamiltonoian augumented with fourth order phonon co-ordinates using double time Greens functions. The results are used to obtain an expression for the frequency  and temperature dependence  of dielectric  loss at microwave frequencies  due to impurity and anharmonic scattering. The loss tangent consists of a contribution which is quadratic in applied biasing and field independent. The variation of tand  with applied field is noticeable in the  vicinity of Curie temperature . In the higher temperature  region, the electric field effect ceases and the  increase in loss arises mainly due to higher order anharmonic terms.

Keywords: Anharmonicity, Softmode, Microwave loss tangent, Displacive ferroelectrics

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, August 2008, pp. 588-592

 

Role of binding energy in the generation of photocurrent in bulk heterojunction organic materials

S K Sharma, Chandra Bothra & G D Sharma

Department of Physics, J N V University, Jodhpur 342 005

Received 11 September 2007; revised 28 March 2008; accepted 2 May 2008

The role of binding energy of electron hole pair in the generation of photocurrent has been studied using Braun’s model based on Onsager theory. For the study, two bulk heterojunction devices namely poly (2-methoxy-5-(3′,7′- dimethyloctyloxy)-p-phenylene vinylene)(OC1C10-PPV) and poly (2-methoxy-5-(3′, 7′-dimethyloctyloxy)-1-4-phenylene vinylene) (MDMO-PPV) have been chosen. These materials act as electron donor in the bulk hetero-junctions and are based on intermixing of conjugate polymers and fullerene derivatives. Photocurrent has been calculated theoretically for different values of exciton binding energies. The variation of photocurrent with binding energy shows that a constant value of photocurrent is obtained up to a threshold value of 0.6 eV. When binding energy exceeds the threshold value, photocurrent diminishes rapidly. Thus, binding energy plays an important role in the generation of photocurrent and can be used as a primary parameter for the characterization of organic semiconductors in solar cell applications.

Keywords: Bulk hetereojunction, Binding energy, Photocurrent density, Polymer, Fullerene interface.

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, August 2008, pp. 593-597

 

Design, fabrication and characterization of microstrip square patch antenna array for X-band applications

Deepak Sood*, Gurpal Singh**, Chander Charu Tripathi, Suresh Chander Sood & Pawan Joshi

Electronics & Communication Department, Ambala College of Engineering & Applied Research

(Near Mithapur), Ambala Cantt., Haryana

**Computer Science Department, Baba Banda Singh Bahadur Engineering College,
Fathegarh Sahib, Punjab

*E-mail: deepaksood1980@yahoo.com

Received 9 August 2007; revised 20 March 2008; accepted 17 April 2008

Microstrip patch antenna array to be used for X-band short-range microwave applications has been introduced. This antenna maintains a maximum gain of 14.6 dB for far field region w.r.t paraboloidal rectangular aperture antenna. It is actually a probe (coaxial) fed antenna with quarter wave sections that are fabricated as an arrangement for impedance matching with 50 Ω coaxial cable. This antenna works well in the frequency range 8.45-9.33 GHz with a maximum at 8.53 GHz. It is basically a low cost, lightweight, medium gain and narrowband antenna and suited for short-range microwave applications such as a feeding element for other antennas and in research institutes as a reference antenna. It can also be used at the output of signal conditioning circuit for receiving signals from micro electromechanical sensors.

Keywords: Square patch, X-band, Antenna array