Deposition of Thick SiO2 Coatings to Carbonyl Iron Microparticles for Thermal Stability and Microwave Performance

Abstract

Thick dielectric SiO2 shells on the surface of iron particles enhance the thermal and electrodynamic parameters of the iron. A technique to deposit thick, 500-nm, SiO2 shell to the surface of carbonyl iron (CI) particles was developed. The method consists of repeated deposition of SiO2 particles with air drying between iterations. This method allows to obtain thick dielectric shells up to 475 nm on individual CI particles. The paper shows that a thick SiO2 protective layer reduces the permittivity of the ‘Fe-SiO2—paraffin’ composite in accordance with the Maxwell Garnett medium theory. The protective shell increases the thermal stability of iron, when heated in air, by shifting the transition temperature to the higher oxide. The particle size, the thickness of the SiO2 shells, and the elemental analysis of the samples were studied using a scanning electron microscope. A coaxial waveguide and the Nicholson–Ross technique were used to measure microwave permeability and permittivity of the samples. A vibrating-sample magnetometer (VSM) was used to measure the magnetostatic data. A synchronous thermal analysis was applied to measure the thermal stability of the coated iron particles. The developed samples can be applied for electromagnetic compatibility problems, as well as the active material for various types of sensors.

Involvement of Acid-Leachable Inorganics in Pyrolysis of Pig Manure

“…After 800 °C, it still had a greater degree of weight loss, which was related to decomposition of CaCO 3 and Ca 3 (PO 4 ) 2 , as detected by XRD analysis (Figure b). Inorganics contained in the char produced from the acid-treated sample were mainly SiO 2 , which had good thermal stability …”

“…Inorganics contained in the char produced from the acid-treated sample were mainly SiO 2 , which had good thermal stability. 40 3.3.5. FTIR and Hydrophilic Analysis.…”

Influence of Hydrogen Reduction Stage Conditions on the Microwave Properties of Fine Iron Powders Obtained via a Spray-Pyrolysis Technique

“…The simultaneous thermal analysis (STA) instrument Netzsch STA 449 F3 Jupiter (Netzsch, Germany) was used to carry out the oxidation experiments [22]. The weight of iron powders taken for analysis was controlled at 10-20 mg to decrease the influence of the temperature gradient in the sample.…”