Hexagonal Ferrite Magnetic Powder Surface Modification
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Solution Overview
Problem
Existing methods for manufacturing hexagonal ferrite magnetic powder face challenges in achieving high dispersion in magnetic coating materials without applying a large dispersion load, which can damage the magnetic powder and affect the quality of the magnetic layer in recording media.
Innovation Solution
The method involves surface-modifying hexagonal ferrite magnetic particles with a compound having anionic and hydrophobic groups, ensuring adequate positive charging and uniform adsorption of the surface-modifying agent, allowing for high dispersion in organic solvents and reducing the dispersion load during the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hexagonal ferrite magnetic powder is wet dispersed with a strong acid surface treatment agent (low pKa), then the dispersibility of magnetic powder is improved, but the magnetic powder may be damaged by the dispersion medium due to the large dispersion load required after solidification
Solution Approach 1:
The patent applies preliminary action by conducting surface modification with a fatty acid compound (having carboxyl groups) on the hexagonal ferrite magnetic powder before the wet dispersion step. This pre-treatment creates a protective organic layer on the particle surfaces, which prevents damage during subsequent high-shear dispersion processes while maintaining good dispersibility in the magnetic coating material
Solution Approach 2:
The patent changes the chemical parameter of the surface treatment by using a fatty acid compound with specific pKa characteristics (weaker acid compared to traditional strong acids) and controlling the treatment conditions. This parameter change allows effective surface modification that improves dispersibility without the harsh effects that would damage the magnetic powder particles
2Manufacturing precision
If a considerable load is applied to pulverize and disperse the solidified magnetic powder, then the magnetic powder can be dispersed in microparticulate form, but the magnetic powder may be damaged by the dispersion medium
Solution Approach 1:
The surface modification with fatty acid compound is performed as a preliminary action before the high-load dispersion process. This creates a protective interface layer that allows the magnetic powder to withstand the mechanical stresses of pulverization and dispersion without particle damage, enabling achievement of uniform microparticulate size distribution
Solution Approach 2:
The fatty acid surface treatment acts as a cushioning layer that absorbs and distributes the mechanical stress during dispersion. This beforehand cushioning protects the magnetic powder particles from direct damage while still allowing effective size reduction and uniform distribution to be achieved
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 enables the production of magnetic recording media with excellent electromagnetic characteristics by achieving high dispersion of hexagonal ferrite magnetic powder, reducing the dispersion load, and maintaining the integrity of the magnetic particles, thereby improving the quality and efficiency of the magnetic layer.
Implementation Method 1
uniform adsorption of the surface-modifying agent
Data Source
AI summary
An aspect of the present invention relates to a method of manufacturing hexagonal ferrite magnetic powder. The method of manufacturing hexagonal ferrite magnetic powder comprises wet processing hexagonal ferrite magnetic particles obtained following acid treatment in a water-based solvent to prepare an aqueous magnetic liquid satisfying relation (1) relative to an isoelectric point of the hexagonal ferrite magnetic particles: pH0−pH*≧2.5, wherein, pH0 denotes the isoelectric point of the hexagonal ferrite magnetic particles and pH* denotes a pH of the aqueous magnetic liquid, which is a value of equal to or greater than 2.0, adding a surface-modifying agent comprising an alkyl group and a functional group that becomes an anionic group in the aqueous magnetic liquid to the aqueous magnetic liquid to subject the hexagonal ferrite magnetic particles to a surface-modifying treatment, and removing the water-based solvent following the surface-modifying treatment to obtain hexagonal ferrite magnetic particles.