Papers by Keyword: Noble Metal

Abstract: The enhanced ammonia gas sensing properties of palladium decorated Co-SFO are demonstrated here. Pristine SmFeO₃ thick films fabricated by screen printing technique were surface modified with Co by dipping method (dipping time 3 min) and identified as Co-SFO thick films. They showed maximum sensitivity to 50 ppm ammonia at 200 °C. In order to further increase its sensitivity, Co-SFO thick film was dipped into Palladium nitrate solution for 1 min, 2 min and 3 min. Surface morphology of as-prepared thick films was studied by FE-SEM. Formation of PdO phase and its uniform distribution over Co-SFO surface was confirmed from EDAX spectra. Gas sensing results revel that the sensitivity of Pd decorated Co-SFO thick films towards 50 ppm ammonia was increased. Moreover, decrease in operating temperature was also observed. Pd decorated Co-SFO thick film with dipping time 3 min has maximum sensitivity at lower operating temperature. The improved sensitivity at low temperature was attributed to the sensitization of palladium which was discussed in details. Keywords: Co-SFO, Chemical sensitization, Noble metal, Gas Response, Reducing gas.

Abstract: Platinum (Pt), a noble metal, is known for its ability to regenerate and be recycled even without any reactivation procedure, and still demonstrated good stability. The cost of the noble metal can be reduced by incorporating the metal into the pores of catalyst support rather than using it individually. Hence, in this research study, 4 wt.% Pt supported on silica-alumina (SiO₂-Al₂O₃) and gamma-alumina (γ-Al₂O₃) was synthesized using wet impregnation method, then followed by catalyst calcination at 500 °C. The catalyst was then characterized using Thermogravimetric Analysis (TGA), Fourier-Transform Infrared Spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), and particle size analyzer where catalyst with high surface area and pore volume demonstrated an excellent performance for the catalytic reaction of cellulose. Experimental results showed that catalyst Pt/SiO₂-Al₂O₃ with the highest surface area and pore volume (466.4 m²/g and 0.1157 cm³/g, respectively) exhibited the highest catalytic performance with the conversion of cellulose up to 65.8% and 30.9% levulinic acid (LA) yield produced at the reaction temperature of 200 °C in a semi-batch reactor for 8 hrs.

Abstract: Scale surface and scale/alloy interface for alumina-forming (Fe-20Cr-4Al) alloys with noble metal (palladium, platinum) and yttrium were studied in oxidizing atmospheres (oxygen, oxygen-water vapor) for 18ks at 1473, 1573 and 1673K, by mass gain measurements, amount of spalled oxide, X-ray diffraction (XRD), scanning electron microscopy (SEM) and field emission-transmission electron microscopy/energy dispersive spectroscopy (FE-TEM/EDS). After oxidation at 1473K for 18ks in oxygen, the mass gains of the FeCrAl, FeCrAlPd and FeCrAlPt alloys showed almost the same values. Those of the FeCrAlY alloys decreased with increasing yttrium of up to 0.1% followed by an increase with the yttrium content. The mass gain of the FeCrAlPtY alloys with appropriate additions of platinum and yttrium were lower than that of the FeCrAlY alloy with 0.1mass% yttrium, and alumina/alloy interface of the alloy showed good coherency by TEM. The scale surface of the FeCrAl, FeCrAlPd and FeCrAlPt alloys were rough, however, those of the FeCrAlY and FeCrAlPtY alloys were smooth. After oxidation at 1673K for 18ks in water-vapor (47vol%), FeCrAlPt alloy with 0.5mass% platinum showed good oxide adherence. Platinum concentration was observed at alloy side of the alumina/alloy interface by FE TEM/EDS.

Abstract: This work describes atomic-scale, crystalline structure and size distribution for noble metal nanoparticles produced by water-based, environmental friendly technologies. The process was developed and implemented to produce noble metal nanoparticles to be used in water filters, sensors and cosmetics. The particles were investigated by TEM methods and particle size analysis. Growth process of the crystallites in sols made by chemical reduction in aqueous solutions is discussed. Comparison with growth models for vacuum deposited thin films is also identified.

Abstract: Nano-sized metal particles have recently attracted considerable interest owing to their application potential. Such particles can be synthesized using physical and chemical methods. In this study, nano-sized noble metals were synthesized through the reaction of metal oxides by ultrasonic. This means that the chemical reactions which take place under conventional conditions can be accelerated by ultrasonic cavitations. In general, the chemical effects of ultrasonic irradiation fall into three areas: homogeneous sonochemical efffects of liquids, heterogeneous sonochemical effects of liquid-liquid or liquid-solid systems, and sonocatalytic effects. It has been proposed that liquid-liquid systems are used for the fabrication of nano-metal particles in the past. In this study, the fabrication of nano-metal particles and supported composites was investigated for the liquid-solid system from a viewpoint of economy and ecology. By choosing suitable conditions, it is reasonable to expect that these simple ultrasonic processes can be extended to obtain nano-sized metal particles. Thus applications by using these reactions were investigated to prepare the nano-sized metal particle supported materials, and mechanisms were investigated.