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

Abstract

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 .

A study of cytocompatibility and degradation of iron-based biodegradable materials

“…The materials produced from the phosphated carbonyl iron powder (Figure 1(e)) consisted of spheroidized iron (α-Fe phase, light grey, position 1) or of iron oxide compound (darker grey, position 2) particles, surrounded by a solidified liquid phase (darkest grey, position 3) composed of various ferric phosphate compounds resulting from eutectic reactions in the Fe 2 O 3 –P 2 O 5 system. 33,38–40 The materials produced from the mixture of phosphated iron powder and manganese powder (Figure 1(f)) contained spheroidized iron (α-Fe phase, light grey, position 4), manganese oxide compounds (light, position 5), and iron and manganese oxide compound (darker grey, positions 6 and 7) particles surrounded by a solidified liquid phase (darkest grey, position 8). The diffusion of Mn into Fe was visible in the cross sections of the Fe/P–Mn samples; however, the content of residual Mn remained high (Figure 1(f)).…”

Fe and Fe-P Foam for Biodegradable Bone Replacement Material: Morphology, Corrosion Behaviour, and Mechanical Properties

“…Two different methods were employed to produce an iron-phosphorus alloyed material. In the first method, the carbonyl iron particles were coated with phosphate layers [23].…”

Al2O3 “self-coated” iron powder composites via mechanical milling

“…Several wet chemistry and dry coating techniques have been developed for coating iron-alloy powder surfaces with protective layers of alumina; however, uncontrollable phase transformations often led to degraded magnetic properties. For example, the formation of maghemite (Fe 2 O 3 ) during the thermal decomposition of boehmite ( -AlOOH), a precursor to alumina, led to decreased volumes of iron, which thus decreased the magnetic permeability [23,24]. Alumina-coated iron nanocomposites were also synthesized by wet chemistry; however, the magnetization su↵ered due to the formation of FeAl 2 O 4 at reducing temperatures below 800 C [13].…”