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CONTENTS
Volume 2, Number 3, October 2013
 

Abstract
This paper aims to focus on the microwave processing of thick films which is a fast, cheap technique and could be the alternative to the currently used conventional high temperature processing technique. Microwave processing has gained worldwide acceptance as a novel method for heating and sintering a variety of materials, as it offers specific advantages in terms of speed, energy efficiency, process simplicity, finer microstructures and lower environmental hazards. Silver conducting thick films were prepared and processed in the household microwave oven. The films sintered at different time period by keeping the other parameter such as microwave power, film thickness etc constant. The microstructure analysis revealed that the surface morphology of the microwave processed films become compact with respect to the processing time. The sheet resistance for microwave sintered silver films is in the range of 0.003 to 1.207

Key Words
microwave; silver; thick films; conductor; sheet resistance

Address
Sunit Rane, Rushna Bhatkarb, Uttam Mulika and Dinesh Amalnerkara: Microelectronics and Thick Film Materials Group, Centre for Materials for Electronics Technology, Panchawati,Off. Dr. Bhabha Road, Pune-411008,India

Abstract
Nanocrystalline Barium niobate (BaNbO3) has been synthesized by a novel auto-igniting combustion technique. The X-Ray diffraction studies reveals that BaNbO3 posses a cubic structure with lattice constant a = 4.071 A. Phase purity and structure of the nano powder are further examined using Fourier-Transform Infrared and Raman spectroscopy. The average particle size of the as prepared nano particles from the Transmission Electron Microscopy is 20 nm. The UV-Vis absorption spectra of the samples are recorded and the calculated average optical band gap is 3.74eV. The sample is sintered at an optimized temperature of 1425OC for 2h and attained nearly 98% of the theoretical density. The morphology of the sintered pellet is studied with Scanning Electron Microscopy. The dielectric constant and loss factor of a well-sintered BaNbO3 at 5MHz sample is found to be 32.92 and 8.09 x 10-4 respectively, at room temperature. The temperature coefficient of dielectric constant was−179pp/oC. The high dielectric constant, low loss and negative temperature coefficient of dielectric constant was−179pp/oC. The high dielectric constant, low loss and negative temperature coefficient of dielectric constant makes it a potential candidate for temperature sensitive dielectric applications.

Key Words
combustion synthesis; raman spectroscopy; band gap: dielectric; BaNbO3

Address
S Vidya1, K C Mathai, Annamma John, K Joy and J K Thomas: Electronic Materials Research Laboratory, Department of Physics, Mar Ivanios College, Thiruvananthapuram 695015, Kerala, India
Sam Solomon: Dielectric Materials Research Laboratory, Department of Physics, St. John

Abstract
The study of the corrosion inhibition of armatures made of steel conceived for reinforced concrete by sodium phosphate is the aim object of our experimental tests. Gravimetric and electrochemical measurements were carried in three different Mediums contaminated by chlorides (3% NaCl) with addition of increasing concentrations of sodium phosphate. Inhibitory efficiency reached 80% at an optimal concentration of 7,5 x 10-3M, the results obtained using the gravimetric measurements are in good agreement with those obtained by electrochemical methods. However, the monitoring of the pH evolution after 24h shows in the three studied environments, that the pH decreases slightly at 24 hours from the initial pH at t0, due to the presence of corrosion products which change the state of the final solution. Also, scanning electron microscopy revealed the existence of layers of apatite on the metal surface previously treated with the sodium phosphate which confirms the formation of a protective film around the surface of the metal.

Key Words
concrete;corrosion; efficiency; inhibitory; phosphate.

Address
L. SAIL: Latefa SAIL, Abou Bakr Belkaid University, PB 230, Chetouane, Tlemcen, Algeri
F. GHOMARI: Fouad GHOMARI, Abou Bakr Belkaid University, PB 230, Chetouane, Tlemcen, Algeria
A. KHELIDJ: Abdelhafid KHELUDJ, IUT of Saint Nazaire, University of Nantes, France
A. BEZZAR: Adelillah BEZZAR, Abou Bakr Belkaid University, PB 230, Chetouane, Tlemcen, Algeria
O. BENALI: Omar BENALI, University Center of Saida, Algeria

Abstract
Lead-free complex perovskite ceramics NaMeO3 (Me = Nb, Ta) were synthesized using conventional solid state reaction technique and characterized by structural, FTIR and electrical (dielectric and ac conductivity) studies. The crystal symmetry, space group and unit cell dimensions were determined from the experimental results using FullProf software. XRD analysis of the compound indicated the formation of single-phase orthorhombic structure with the space group Pmmm (47). Dielectric studies showed the diffuse phase transition at 394C for NaNbO3 and 430C for NaTaO3. Ac conductivity in both the compounds follows Jonscher‟s power law.

Key Words
NaNbO3; NaTaO3; perovskite; dielectric properties; lead-free; electroceramic

Address
Sumit K. Roy: Department of Physics, St. Xavier\'s College, Ranchi – 834 001, India
S.N. Singh: University Department of Physics, Ranchi University, Ranchi – 834 008, India
K. Kumar: Refractory Division, RDCIS, SAIL, Ranchi – 834 002, India
K. Prasad: University Department of Physics, T. M. Bhagalpur University, Bhagalpur – 812 007, India


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