Kinetics of the Phosphatizing reaction of carbonyl iron powders

Carbonyl iron powders were coated with iron phosphate using phosphating method and boehmite (γ -AlOOH) or silicon hydroxide (Si(OH) 4 ) nanoparticles derived from the hydrolysis of tri-sec-butoxide (Al(OC 4 H 9 ) 3 ) or tetramethylsilane (Si(OCH 3 ) 4 ) using sol-gel method. The coated powders were dried and calcined at 400• C for 3 h in air. Cross-section morphology of coated carbonyl iron powders were investigated by scanning electron microscopy energy dispersive X-ray analysis. Coated Fe micro-particles were spherical in shape with 'shell/core' structures. The shells consisted of an amorphous layer with varying thickness (100-800 nm) and the core represented a carbonyl iron.Gelatinous morphology of dried FePO 4 coating composed from nanoparticles of iron oxyhydroxides and hydrated iron phosphate with a shell thickness of ∼100 nm around iron particles was observed. In coatings based on alumina or silica xerogels with a thickness of ∼100-150 nm or ∼200-500 nm, the coatings were composed of iron oxyhydroxides and γ -AlOOH or Si(OH) 4 . The resulting XRD diffractograms revealed the hematite (α-Fe 2 O 3 ) and magnetite (Fe 3 O 4 ) that were formed in phosphated and sol-gel coated iron powders. The X-ray diffraction patterns did not verify the presence of phosphates, alumina or silica and indicate the amorphous or nanocrystalline structure of FePO 4 , γ -Al 2 O 3 and SiO 2 .

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…• C. [14] After TEOS hydrolysis, the Si(OH) 4 is adsorbed on the Fe particles rapidly. However, the conversion process of Si(OH) 4 into SiO 2 occurs very slowly.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The effect of iron phosphate, alumina and silica coatings on the morphology of carbonyl iron particles

Bruncková

Kabátová

Dudrová

2009

Determination of the oxidation kinetics of modified α‐iron substrate: correlation between TGA and AES

Grosseau-Poussard¹,

Panicaud²,

Dinhut³

et al. 2004

A conversion phosphating treatment has been performed on polycrystalline a-iron in order to modify its thermal oxidation behaviour. This has been studied by means of in situ thermogravimetric experiments and line profile nanoscale AES of the phosphated surface layer, both before and after the oxidation experiments. Modifications of the a-iron oxidation mechanisms and their correlations with the evolution of the oxidation kinetics of a-iron under the influence of phosphate films are evidenced in this work.

Development of methodology for surface analysis of soft magnetic composite powders

Oikonomou

Hryha

Nyborg

2011

Soft magnetic composites (SMCs) are designed for the sustainable industrial production of uniform isotropic components with three-dimensional magnetic properties. The nanocoating covering the surface of water-atomized iron powder is the paramount feature of SMC technology that gives the material the high resistivity needed for minimizing the negative effects of eddy currents. An analysis of its initial state/composition on a micro level and any changes during further compaction and heat treatment is thus of great importance. Therefore, a method for the evaluation of composition and thickness of such insulating coatings was developed in this study. High resolution imaging combined with surface analytical and depth profiling techniques (high resolution scanning electron microscopy (HR SEM) with energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy) were used. Analyses were performed on commercially available SMC powder grades having a phosphate-based coating. Depth profiling was carried out by ion etching and X-ray photoelectron spectroscopy analysis. The analyses revealed the presence of oxygen (O1s), iron (Fe2p), and phosphorous (P2p), indicating these elements as the main components of the insulating coating. Two approaches for the evaluation of the coating thickness were tested based on the relationship between the normalized intensity of the iron metal peak and etch depth where the phosphorus and oxygen intensities reach half the difference of their maximum and minimum values. Results indicate that the thickness of the coating extends to the~30 nm depth into the surface. For HR SEM imaging, utilization of an InLens detector for secondary electron imaging and a low acceleration voltage (~5 kV) is recommended for HR SEM + energy dispersive X-ray spectroscopy analysis of coating morphology and composition.