Hiva Roboubi; Yadollah Mortazavi; Abbas Ali Khodadadi
Abstract
For the first time, this research reports the formation of nanoporous layers of metals on the surface of metal substrates by Raney method and their conversion to corresponding porous perovskite layers. The noble metals doped perovskites are used as catalytic converter for reducing automotive pollutants. ...
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For the first time, this research reports the formation of nanoporous layers of metals on the surface of metal substrates by Raney method and their conversion to corresponding porous perovskite layers. The noble metals doped perovskites are used as catalytic converter for reducing automotive pollutants. The use of perovskite as a substrate for the noble metals can reduce the need for such metals by as much as 70%. The metal surface is treated by plastic deformation at high pressures or quenching to create microstructures, and then an aluminum-metal alloy layer is formed on the surface of the metal by its hot dip aluminizing at 750oC. At the same temperature, the aluminum is diffused into the metal surface layer as deep as 30nm for 1h. Subsequently the sample is gradually quenched or cooled and the aluminum is extracted by soda solution. Nanostructures of about 30 nm are obtained by combined Raney method together with the plastic deformation process. Quenching of the alloy creates even smaller nanostructures. The porous metal layer is impregnated with lanthanum nitrate for one or more times and calcined at 900oC to create the porous perovskite layer on the surface of the metal substrate as monolith. The perovskite completely converts CO and C2H6 (as representative of the exhaust unburned hydrocarbons).
Afsaneh Sheykh Mohammadi; Yadollah Mortazavi; Abbas Ali Khodadadi; Yousef Zeynali
Abstract
We report the development of different types of oxygen sensors based on yittria-stabilized zirconia (YSZ) as a solid electrolyte. The conventional oxygen sensor is a concentration cell with two porous Pt electrodes, one of which is exposed to air as a constant (reference) oxygen concentration and the ...
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We report the development of different types of oxygen sensors based on yittria-stabilized zirconia (YSZ) as a solid electrolyte. The conventional oxygen sensor is a concentration cell with two porous Pt electrodes, one of which is exposed to air as a constant (reference) oxygen concentration and the other is exposed to automobile exhaust gas of variable oxygen concentration, depending on the air-to-fuel (ATF) ratio injected into engine. The conventional sensor is miniaturized by using an oxide semiconductor instead of the reference air. This the response time and the sensitivity of the sensor significantly improved. Also the light-off time, during which most of large city pollutant are dramatically reduced. The transition response of above sensors occur at the stoichiometric ATF ratio, while recently lean-burn engines working at ATF ratios higher than that of stoichiometric are proffered. In addition to the above sensors, we have developed a new type of YSZ- based oxygen sensor, in which two oxides (e.g. TiO2, SnO2 and CeO2) with different semi conductive characteristics are applied on the tow Pt electrodes. This way the transition response of the sensor is shifted toward ATF ratios higher than the stoichiometric ones, suitable for lean-burn engines.
