Thermal decomposition of Fe(III) nitrate and its aerosol
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I. INTRODUCTION
To produce spherical ultrafine pure particles which can compact to uniform bodies and sinter in a controlled manner, aerosol techniques become valuable routes. In the aerosolization process, an appropriate solution is aerosolized and each droplet acts as a separate reactor in which reactions occur to get the required product. In this study, an aqueous solution of iron nitrate nonahydrate was used as the starting solution of the proposed aerosolization process to produce Fe2O3 powders which are required to form ceramic ferrites. Ferrites are used as soft or hard magnetic materials. Unlike metals, these ferrites combine high magnetic permeability with high electrical resistivity. These properties are especially critical in high frequency application since they promote low heat generation and low energy losses during electrical circuit operation. A series of thermal analyses were conducted using a variety of heating rates, in stagnant and flowing air, to study the thermal behavior of Fe(NO3)3-9H2O. The thermal results are necessary to understand the reactions occurring during pyrolysis of the aerosol formed from its solution and to assess the products obtained at various temperatures.
(EDS)3 technique. O'Holleran et al.3 reported that fine crystals of Fe2O3 with particle size 1.8 jam were obtained by decomposing the aerosol of 0.3 M iron nitrate solution at 850 °C. Sproson et al.A stated that well crystallized Fe2O3 having surface area 11.5 m2/g was produced by evaporative decomposition of 1 M iron nitrate solution at 1000 °C. In both studies the heating rates were not determined. III. EXPERIMENTAL TECHNIQUES A. Thermal analysis
A Netzsch Simultaneous Thermal Analyzer, STA 409, which is capable of performing differential thermal analysis (DTA) and thermogravimetric analysis (TG) simultaneously for the same sample, was used to carry out the study of the thermal behavior of Fe(NO3)3 • 9H2O in stagnant and flowing air (10.9 mL/min) using several different heating rates. Calcined kaolin was used as a reference material and alumina crucibles of 99.5% purity were used as sample holders. The starting material was iron nitrate nonahydrate of 98% purity and was purchased from AESAR. The intermediate phases and reactions were concluded from the information of TG, DTA, their first derivatives, and x-ray diffraction.
II. PREVIOUS WORK
In the thermal behavior of the salt, Wendlandt1 reported that iron nitrate nonahydrate began to lose its water of hydration at 35 °C in flowing air, when a heating rate of 5.4 °C/min was used. The thermal decomposition proceeded directly to Fe2O3, which was obtained at 445 °C. On the other hand, Mu and Perlmutter2 stated that this salt decomposed to Fe2O3 after heating up to 280 °C in flowing nitrogen at a heating rate of 1 cC/min. They reported that anhydrous iron nitrate exists as an intermediate phase during the decomposition. Pyrolysis of aerosols was reported to give fine spherical particles. This process is known as spray pyrolysis or evaporative decomposition of solution
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