Room temperature synthesis of -Fe2O3 by sonochemical route and its response towards butane
I. Raya, S. Chakraborty a, A. Chowdhury b, S. Majumdara,
A. Prakash a, Ram Pyare b, A. Sena,∗
a Sensor and Actuator Division, Central Glass and Ceramic Research Institute, 196 Raja S.C. Mullick Road, Kolkata 32, India
b Department of Ceramic Engineering, Institute of Technology, Banaras Hindu University, Varanasi 221005, India
Abstract
Nanocrystalline gamma iron oxide (-Fe2O3) has been synthesized at room temperature through sonication-assisted precipitation technique.The key in obtaining -Fe2O3 at room temperature lies in exploiting high-power ultrasound (600 W). The gas-sensing properties to n-butane of pure -Fe2O3 were investigated by studying the electrical properties of the sensor elements fabricated from the synthesized powder. The maximum
response (∼90%) of the sensor to 1000 ppm n-butane at 300 ◦C can be explained on the basis of catalytic activity of the nanocrystallites. The response and recovery time of the sensor to 1000 ppm n-butane were less than 12 s and 120 s, respectively.
Keywords: Gamma iron oxide; Sonochemical; Gas sensor; Butane; Room temperature
1. Introduction
Gamma iron oxide (-Fe2O3) is a ferrimagnetic material that is widely used in audio and video recording [1] as a magnetic storage medium, magnetic refrigeration [2], bioprocess [3], etc. Recently, it has been studied as a gas-sensitive material because -Fe2O3 does not require costly noble metal catalyst to perform as a good sensor [4–8]. In gas-sensing applications nanosized powders have shown outstanding properties, especially sensors made with them showed low operating temperature, high sensitivity and high selectivity [9,10] because of their large surface to volume
ratio and the criterion imposed by the Debye length [11–15], such as vapour deposition (280 ◦C), sol–gel processing (300 ◦C), combustion processing (250 ◦C) and co-precipitation (400 ◦C). Currently, sonochemical technique has emerged as a cheap, simple and alternative route of nanopowder preparation [16]. The chemical effects of ultrasound arise from acoustic cavitation, which is the formation, growth and mplosive collapse of bubbles in a liquid [17,18]. The cavitation can generate a temperature of around 5000 ◦C and a pressure over 1800 kPa, which enable many unusual chemical reactions to occur easily [19]. In this study, nanosized -Fe2O3 powder has been prepared by a sonication-assisted precipitation route at around room temperature (∼70 ◦C). The gas-sensing characteristics of -Fe2O3 in the presence of n-butane have been investigated in detail keeping in view the presence of butane in LPG, the latter being used as a fuel in domestic, industrial and automobile sectors.
Synthesis
Ferric nitrate nanohydrate [Fe(NO3)3·9H2O] and hydrazine monohydrate [(NH2)2·H2O] were used as starting materials. First, 0.01Mferric nitrate was prepared by dissolving a required amount of Fe(NO3)3·9H2O (Merck, 99 % purity) in distilled
water. The solution was sonicated (ultrasonic processor, Sonics, 600W, 20 kHz, probe length 25 cm, diameter 20 mm, titanium alloy TI-6AL-4V) for 15 min at a time in a 250mL container.
