Hexagonal Ferrite Magnetic Powder for Uniform Dispersion
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Solution Overview
Problem
Magnetic recording media face issues with the incorporation of coarse aggregates of magnetic particles during dispersion treatment, leading to increased error rates and reduced reliability, particularly when dealing with small primary particle sizes or hard secondary particles, which existing techniques fail to adequately address.
Innovation Solution
The implementation of Al-containing hexagonal ferrite magnetic powder with controlled particle size distribution, achieved through 'finishing pulverizing' and adherence of a hydroxide of aluminum, ensures uniform pulverization and suppression of large aggregates, utilizing a laser diffraction particle size distribution analyzer to optimize dispersion pressure and particle size ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the primary particle size of magnetic powder is reduced to improve recording density, then the recording density is improved, but uniform pulverization during dispersion treatment becomes difficult and coarse aggregates form
Solution Approach 1:
The patent applies preliminary action by controlling the particle size distribution before the dispersion treatment step. Specifically, the magnetic powder is pre-treated to ensure that particles larger than a predetermined size are reduced, so that when dispersion treatment occurs during coating material preparation, uniform pulverization is achieved and coarse aggregates are prevented from forming.
Solution Approach 2:
The patent changes the particle size distribution parameters of the magnetic powder by implementing a preliminary size reduction process. The particle size distribution is controlled so that the volume ratio of particles larger than a predetermined size is within a specific range, which enables the magnetic powder to be uniformly pulverized during subsequent dispersion treatment without forming coarse aggregates.
2Reliability
If the magnetic powder has small primary particle size or hard secondary particles, then the magnetic properties are improved, but sufficient pulverization during dispersion treatment cannot be achieved
Solution Approach 1:
The patent applies preliminary action by performing a size reduction treatment on the magnetic powder before it is used in the coating material preparation. This preliminary treatment ensures that even particles that are small and hard to pulverize will be uniformly ground during the subsequent dispersion treatment, preventing the formation of coarse aggregates while maintaining the improved magnetic properties.
Solution Approach 2:
The patent changes the particle size distribution parameters by controlling the volume ratio of large particles to be within a specific range. This parameter control ensures that the magnetic powder, regardless of its initial hardness or small size, achieves sufficient pulverization during dispersion treatment while maintaining the durability associated with small primary particle size and hard secondary particles.
3Ease of manufacture
If conventional magnetic powder is used without preliminary size control, then the production process is simple, but coarse aggregates are incorporated into the film
Solution Approach 1:
The patent introduces a preliminary size control step in the production process. Magnetic powder is produced with controlled particle size distribution where the volume ratio of particles larger than a predetermined size is within a specific range. This preliminary control ensures uniform pulverization during subsequent dispersion treatment while adding minimal complexity to the overall manufacturing process.
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 results in stable and reliable magnetic recording media with low error rates by ensuring uniform refinement of magnetic powder, effectively preventing the incorporation of large aggregates and enhancing durability.
Implementation Method 1
particle size distribution as measured by a laser diffraction particle size distribution analyzer
Data Source
AI summary
Provided is an Al-containing hexagonal ferrite magnetic powder which produces an excellent durability-improving effect on a magnetic recording medium, wherein uniform pulverization of the magnetic powder can be easily achieved by dispersion treatment in preparation of a magnetic coating material even in cases where the magnetic powder has a small primary particle size or has a composition which is likely to produce hard secondary particles. The magnetic powder for a magnetic recording medium is an Al-containing hexagonal ferrite magnetic powder having an Al/Fe molar ratio of 0.030 to 0.200, and has a particle size distribution in which the volume ratio of particles having a particle size of 30 μm or more as measured by a laser diffraction particle size distribution analyzer with a dispersion pressure of 100 kPa is 5.0% or less, and an activation volume Vact of 1800 nm3 or less.