Core-shell epsilon iron oxide particles for magnetic recording
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Solution Overview
Problem
Existing methods for synthesizing epsilon type iron oxide particles result in aggregated particles with high variation in primary particle diameter, affecting magnetic recording density and signal-to-noise ratio due to unsettled precursors in silica matrices during firing.
Innovation Solution
The development of core-shell particles with a core of iron oxyhydroxide or iron oxide compounds coated with a polycondensate shell of metal alkoxide, which are emulsified and fired to prevent aggregation, achieving a small coefficient of variation in primary particle diameter and improved signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If firing is performed with unsettled precursors in silica matrix, then epsilon type iron oxide can be synthesized, but particle aggregation occurs and primary particle diameter variation increases
Solution Approach 1:
The invention divides the particle system into core and shell segments. The core contains the iron oxide precursor particles with controlled size distribution, while the shell segment provides a protective silica matrix. This segmentation allows the precursors to maintain their individual identities and size uniformity during firing, preventing aggregation while enabling complete transformation to epsilon type iron oxide.
Solution Approach 2:
The invention performs preliminary actions by pre-forming the core particles with precise size control using reverse micelle methodology before embedding them in the silica matrix. The precursors are prepared in advance with settled and controlled characteristics, then encapsulated in the shell structure. This preliminary preparation ensures that when firing occurs, the particles transform uniformly without aggregation, achieving small primary particle diameter variation.
2Length of moving object
If average primary particle diameter is reduced to increase recording density, then signal-to-noise ratio may deteriorate due to high coefficient of variation
Solution Approach 1:
The invention changes the parameters of particle formation by controlling the reverse micelle synthesis conditions, including water-to-surfactant ratio, metal salt concentration, and aging time. These parameter changes enable precise control over the core particle size and size distribution. By optimizing these parameters, the invention achieves small average particle diameter (6-20 nm) with simultaneously small coefficient of variation (0.3 or less), resolving the contradiction between size reduction and uniformity maintenance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach produces epsilon type iron oxide-based compound particles with a small coefficient of variation in primary particle diameter, enhancing the signal-to-noise ratio and magnetic recording density by preventing aggregation and controlling particle size during firing.
Implementation Method 1
a shell which covers the core and includes a polycondensate of a metal alkoxide
Implementation Method 2
The development of core-shell particles with a core of iron oxyhydroxide or iron oxide compounds coated with a polycondensate shell of metal alkoxide, which are emulsified and fired to prevent aggregation
Implementation Method 3
a method of firing FeCo alloy powder included in a matrix formed of SiO2 has been known
Data Source
AI summary
A core-shell particle includes: a core including an iron oxyhydroxide compound represented by Formula A3a3Fe1−a3OOH (in which A3 represents at least one metal element other than Fe, and a3 satisfies 0<a3<1) or at least one iron oxide compound selected from the group consisting of Fe2O3, a compound represented by Formula A1a1Fe2−a1O3 (in which A1 represents at least one metal element other than Fe, and a1 satisfies 0<a1<2), Fe3O4, and a compound represented by Formula A2a2Fe3−a2O4 (in which A2 represents at least one metal element other than Fe, and a2 satisfies 0<a2<2); and a shell which covers the core and includes a polycondensate of a metal alkoxide.