The kinetics of formation of calcium aluminates was studied by firing the reaction mixes in the temperature range 1200" to 1460°C for reaction times from 15 to 360 min. Phases formed were determined by taking X-ray diffractograms of the samples. It was observed that all stable calcium aluminates were formed and that monocalcium aluminate (CA) grew with calcium dialuminate (CA,) in a 1:2 reaction mix of CaO and A1203. CA reacted further with AIz03 to form CA,. The formation of CA, obeyed the rate law equation 1 -(1 -x)ln = Kt/rZ. The activation energy for the system (140 kJ-mol-' (33.4 kcal-mol-')) was determined by the Arrhenius equation. [

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Aluminium doped zinc oxide (AZO) thin films were prepared on glass substrate by spray pyrolysis technique and subsequently their structural, morphological and optical properties were investigated and analyzed as a function of annealing temperature. The films were deposited at 350°C and were annealed at temperature 350, 400, 450 and 500°C. X-ray diffraction (XRD) analysis confirms that both deposited and annealed films are polycrystalline in nature and have hexagonal wurtzite structure. The crystalline size as well as the crystalline quality of the film was found to increase with the increase of annealing temperature to a certain point. However, the dislocation density and the compressive stress induced in as-deposited AZO films reduce with annealing temperature. SEM image reveals that the deposited film has nanorope like morphology. The average diameter of the rope and the density of the morphology increases with the increase of annealing temperature. As the annealing temperature increases from 350°C to 450°C, the average transmittance of the films increases and the band gap value decreases from 3.25 eV to 3.17 eV. In addition, obtained results also show that urbach energy, extinction coefficient, refractive index, optical conductivity has changes noticeably with annealing temperature.

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A reduced size branch line coupler (BLC), which does not use bonding wires, lumped elements, or via holes, is reported in this article. The technique presented uses T-model approach, which is a combination of low-impedance and high-impedance quarter wave transmission lines for realizing the proposed structure. The coupler's operating frequency bandwidth is between 2.1 and 2.67 GHz, and its size has been reduced by almost 75.31% compared with the conventional BLC. The S-parameters and the phase difference between the output ports are simulated using CST microwave studio, and the simulation results have been compared with the measurements. The BLC has been designed to operate at 2.5 GHz and fabricated on flame resistance board (FR4 Board). The study shows that there is good agreement between the simulated and measured results. The proposed coupler has promising potentials for beam-forming network applications such as butler matrix due to its smaller size. V C 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:237-240, 2012; View this article online at wileyonlinelibrary.com.

The addition of copper oxide in cement raw mix is known to improve its burnability, with increase in formation of the alite phase. Copper slag, a by-product of the metallurgical industry, containing copper oxide can therefore be a useful additive in the manufacture of cement, particularly for hard burning raw mixes. This paper presents a study on the effect of addition of 1 . 5-2 . 5% of a typical by-product copper slag sample to cement raw mixes prepared from two different limestone samples, with free silica content of 5 . 52 and 10 . 97% and average grain sizes of 124 and 175 ìm. The clinker parameters such as limestone saturation factor, silica modulus and alumina modulus were in the ranges 0 . 91-0 . 92, 2 . 11-2 . 29 and 1 . 0-1 . 20, respectively. The fineness values of the raw mixes were 3 . 50-4 . 20 and 20 . 80-21 . 34% retained on 212 and 90 ìm sieves, respectively. Burnability studies of these raw mixes were conducted at temperatures of 1300, 1350, 1400 and 14508C, with retention time of 20 min, and showed increase in the rate of lime assimilation, acceleration in the formation and growth of C 3 S and lowering in clinkerisation temperature by 508C. The free silica was found to be completely assimilated at 14008C in mixes containing copper slag. The mineral phase developments and microstructures of laboratory clinker samples fired at 1400 6 58C were comparable to control clinker prepared at 1450 6 58C. Physical properties of ordinary Portland cement prepared using this clinker showed performance comparable with control cement. The copper slag contains heavy elements, therefore a leaching study was also conducted by immersing hardened cement pastes in distilled water for 6 months. The leachates, such as barium, copper and chromium, were found to be 0 . 032, 0 . 005 and 0 . 031 ppm, indicating fixation of these elements in the clinker mineral phases.