A new type of catalyst allows carbonyl iron powder to be coated with SiO2 for tuned microwave absorption

Wang, Hanqun; Wang, Meng; Zhang, Xiaochen; Lü, Zhiyao; Fu, Wenbo; Zhong, Bo; Wang, Chunyu; Zou, Jiaxin; Huang, Xiaoxiao; Wen, Guangwu

doi:10.1016/j.surfin.2020.100755

Cited by 10 publications

(10 citation statements)

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Section: Introductionmentioning

confidence: 99%

“…Iron powders are widely applied in power transformers, inductors, sensors [ 1 ], electromagnetic compatibility solutions [ 2 , 3 ], and materials designed to decrease electromagnetic pollution [ 4 , 5 ]. Commonly used is the carbonyl iron with spherical particles of 2 [ 5 , 6 ]–10 [ 4 ] micron in the mean diameter. Carbonyl iron possesses remarkable magnetic properties, although chemical stability and electromagnetic performance are still to be improved when embedded into composite materials.…”

Section: Introductionmentioning

confidence: 99%

“…Surface modification of iron particles with a chemically inert non-conductive coating may solve these tasks. Inorganic and polymer coatings suit well: MnO 2 , BaTiO 3 , carbon, PMMA, polyaniline [ 4 ], parylene C [ 7 ], ZnO, Fe 3 O 4 [ 8 ], etc. In addition, the SiO 2 is the most commonly used among others.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the SiO 2 is the most commonly used among others. Silica shell provides iron with oxidation resistance in the air [ 4 , 9 ] and corrosion resistance [ 6 ]. Modifying iron with these non-conductive shells prevents electric contact between particles and combines magnetic and dielectric losses in one material [ 8 ].…”

Section: Introductionmentioning

confidence: 99%

“…Mechanical milling also improves the adhesion of the silica coating to coarse iron powders [ 12 ]. Another technique to increase the uniformity of the SiO 2 is the use of L-lysine instead of ammonia solution [ 4 ].…”

Section: Introductionmentioning

confidence: 99%

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Deposition of a SiO2 Shell of Variable Thickness and Chemical Composition to Carbonyl Iron: Synthesis and Microwave Measurements

Dolmatov

Zezyulina²,

Osipov³

et al. 2021

Sensors

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Protective SiO2 coating deposited to iron microparticles is highly demanded both for the chemical and magnetic performance of the latter. Hydrolysis of tetraethoxysilane is the crucial method for SiO2 deposition from a solution. The capabilities of this technique have not been thoroughly studied yet. Here, two factors were tested to affect the chemical composition and the thickness of the SiO2 shell. It was found that an increase in the hydrolysis reaction time thickened the SiO2 shell from 100 to 200 nm. Moreover, a decrease in the acidity of the reaction mixture not only thickened the shell but also varied the chemical composition from SiO3.0 to SiO8.6. The thickness and composition of the dielectric layer were studied by scanning electron microscopy and energy-dispersive X-ray analysis. Microwave permeability and permittivity of the SiO2-coated iron particles mixed with a paraffin wax matrix were measured by the coaxial line technique. An increase in thickness of the silica layer decreased the real quasi-static permittivity. The changes observed were shown to agree with the Maxwell Garnett effective medium theory. The new method developed to fine-tune the chemical properties of the protective SiO2 shell may be helpful for new magnetic biosensor designs as it allows for biocompatibility adjustment.

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