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Zn 0.96 Al 0.02 In 0.02 O could be considered as a promising n-type thermoelectric material for high temperature applications.

In this study, the classic cam mechanism of a single cylinder, four-stroke, 6 hp spark-ignited engine was replaced by an electro-pneumatic rocker mechanism, which is designed and manufactured to open the intake valve at low (3.7 mm), normal (5.7 mm) and high (7.7 mm) lifts between engine speeds of 1600 rpm to 2200 rpm. An air compressor was used to feed 6 bar air pressure in order to have the plungers drive the cams in an orderly manner. A control panel was used to control plungers in order to modulate the valve lifts gradually. The volumetric efficiency, torque, power and specific fuel consumption with this operation were measured at full load and compared to the values with a classic cam mechanism. The results of the study showed that decreasing the valve lift at low engine speeds and increasing the lift at high speeds improve the engine performance. Moreover, it was concluded that the idle speed can be lowered by decreasing the valve lift at low engine speeds.

In this paper, Ca2.8Pr0.2Co4O9 powders were synthesized by sol-gel method and thermal and structural characterization of the powders were systematically examined for high temperature thermoelectric generator applications. Differential Thermal Analysis-Thermogravimetry (DTA-TG) was used to specify appropriate thermal regime of the powders for calcination process. Chemical structure and reaction type of intermediate temperature products were defined by Fourier Transform Infrared (FTIR) Spectroscopy. Structural properties of the powders were implemented by X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) was used to specify chemical composition and empirical formula of the elements existed within the powders. It can be seen from the phase spectrum that 2θ peaks of Ca2.8Pr0.2Co4O9 correspond to the literature and coincide with typical Ca3Co4O9 peaks. Seebeck coefficients of the samples are much higher than Ca3Co4O9 while they are closer to literature value of Ca2.8Pr0.2Co4O9. The highest Seebeck coefficient of Ca2.8Pr0.2Co4O9 is found to be 179 µV/K at 400 °C which is a little higher than the literature value. These results show that Pr is an effective dopant to increase the Seebeck coefficient values.

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