Electrical and Structural Properties and Facile Synthesis of Alumina Modified by Metal Nanoparticles
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Electrical and Structural Properties and Facile Synthesis of Alumina Modified by Metal Nanoparticles Mohamed M. Gomaa1, Heba M. Gobara2 Abstract: Alumina catalysts modified by platinum and nickel nanoparticles were prepared by chemical reduction and microwave stimulated techniques, and their relationship to electrical properties was studied. The structural and textural properties of such nanocatalysts were examined by XRD, DSC-TGA, N2 physisorption and TEM. The electrical properties of nanoparticle catalysts as functions of the increase of metal concentration are discussed. The electrical measurements were performed in the frequency domain. Three mechanisms are suggested for the electrical behaviour of all systems. The increment observed in conductivity with extra amounts of metal may be due to the expansion in the movement ability of uncontrolled transporters that disperse in the pores of the material. Upon arrival at the electrodes, these transporters evacuate their charge and, accordingly, increase the dispersion impedance. The results show high thermal stability up to 1000 °C. The isotherms obtained display almost the same behaviour for samples prepared by both the microwave and the chemical method. This may be linked to high-dispersion particles and their nanoscale metal concentration. The XRD results exhibit small diffraction line characteristics. Keywords: conductivity, dielectric constant, nanocatalyst, microwave method, chemical reduction method
1. Introduction A few studies in the literature have reported facile and rapid synthesis of Pt and Ni nanoparticle-supported catalysts. Metal nanoparticles have very wide applications in the fields of physics, chemistry, electronics and biology, because they have singular chemical, electrical, optical and photo-electrochemical attributes [1–9]. These attributes are highly determined by the volume and form of grains. Nanoparticles generally have a high surface area and a high surface-to-volume ratio. There are many applications for catalysts in nano structure metals, optoelectronics and microelectronics. Nanometre nickel powders have specific properties in magnetism, thermal resistance and chemical activity. Nickel nano powders have wide applications in batteries, hard alloys, catalysts and electricity (cellular phones and mobile computers) [10, 11]. There are many techniques used for the preparation of metal nanoparticles, such as
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the chemical reduction method [11–18], the electrochemical reduction method [19, 20], the photochemical reduction method [21, 22], the sonochemical method [23], the microemulsion method [24], the polyol process method [25, 26], the alcohol reduction method [27], the heat evaporation method [28, 29] and many others [30, 31]. Physical methods need vacuum and expensive equipment and a temperature above 1000 °C [29]. The conditions needed for the chemical methods are not sophisticated and not so critical. The chemical reduction method is a common method to fabricate colloidal metal particles due to it being easy to control, its conven
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