Hexagonal Ferrite Magnetic Powder Ultrafine Particle Removal
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Solution Overview
Problem
Existing methods for manufacturing hexagonal ferrite magnetic powder by the glass crystallization method struggle to effectively remove ultrafine particles, which are superparamagnetic and destabilize magnetization, limiting the achievement of good magnetic characteristics in high-density magnetic recording media.
Innovation Solution
The process involves preparing a melt of hexagonal ferrite-forming and glass-forming components, rapidly cooling, heat treating, and then subjecting the product to acid treatment to dissolve glass components, followed by separation of ultrafine particles in an acidic aqueous solution, allowing for selective removal of these particles through decantation, thereby enhancing magnetic characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the glass crystallization method is used to manufacture hexagonal ferrite magnetic powder, then the desired single particle dispersibility and suitability to size reduction are achieved, but ultrafine particles that are superparamagnetic and destabilize magnetization are formed and difficult to remove
Solution Approach 1:
The patent extracts and removes the harmful ultrafine particles from the hexagonal ferrite magnetic powder through a two-stage process: first using an elutriation apparatus to separate particles by size, then using a hydrocyclone to further remove remaining ultrafine particles. This extraction principle directly addresses the technical contradiction by eliminating the superparamagnetic particles that destabilize magnetization while preserving the desired magnetic characteristics of the main particle population.
Solution Approach 2:
The patent replaces conventional mechanical sorting methods with a combination of elutriation (fluid dynamics-based separation) and hydrocyclone separation (centrifugal force-based separation). This substitution allows for more effective removal of ultrafine particles compared to traditional mechanical sorting, resolving the contradiction between maintaining single particle dispersibility and removing harmful ultrafine particles.
2Manufacturing precision
If hexagonal ferrite magnetic particles are used for high-density recording, then coercive force is maintained even when particle size is reduced, but ultrafine particles are formed that do not contribute to magnetic recording and destabilize magnetization
Solution Approach 1:
The patent applies extraction by removing ultrafine particles through elutriation and hydrocyclone separation. The elutriation apparatus separates particles based on size, and the hydrocyclone further removes remaining ultrafine particles, thereby achieving precise particle size control while eliminating the harmful superparamagnetic fraction that forms during the manufacturing process.
Solution Approach 2:
The patent changes the physical parameters of the particle separation process by using elutriation (controlling fluid flow rate and particle settling velocity) and hydrocyclone separation (controlling rotational speed and pressure differential). These parameter changes enable precise differentiation between desired fine particles and harmful ultrafine particles, achieving manufacturing precision while removing harmful factors.
3Productivity
If particle diameter is reduced for high-density recording, then recording density is improved, but ultrafine particles are formed that are affected by thermal fluctuation and destabilize magnetization
Solution Approach 1:
The patent extracts harmful ultrafine particles through a two-stage separation process: elutriation removes particles below a certain size threshold, and hydrocyclone separation removes remaining ultrafine particles. This extraction enables the use of reduced particle diameter for high-density recording while eliminating the thermally unstable ultrafine fraction that would otherwise destabilize magnetization.
Solution Approach 2:
The patent performs preliminary removal of ultrafine particles before the magnetic powder is used in high-density recording applications. By conducting elutriation and hydrocyclone separation in advance, the patent ensures that only stable, non-superparamagnetic particles remain, thereby maintaining magnetization stability even when small particle sizes are used for high recording density.
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 method enables the production of hexagonal ferrite magnetic powder with improved magnetic characteristics and thermal stability by selectively removing ultrafine particles, facilitating the creation of high-density magnetic recording media.
Implementation Method 1
rapidly cooling the melt to obtain a solidified product (amorphous material)
Implementation Method 2
Heat treating the solidified to cause hexagonal ferrite magnetic particles (referred to as 'hexagonal ferrite particles' or simply 'particles', hereinafter) and a glass component to precipitate out
Implementation Method 3
subjecting the heat-treated product to an acid treatment and a cleaning treatment to dissolve away the glass component
Implementation Method 4
separating the particles dispersed in the aqueous solution and the precipitated particles
Data Source
AI summary
An aspect of the present invention relates to a method of manufacturing hexagonal ferrite magnetic powder, which comprises preparing a melt by melting a starting material mixture comprising a hexagonal ferrite-forming component and a glass-forming component and rapidly cooling the melt to obtain a solidified product, heating the solidified product to precipitate hexagonal ferrite magnetic particles and glass components in the solidified product, subjecting the solidified product to an acid treatment following the heating to remove the glass components by dissolution, incorporating the hexagonal ferrite magnetic particles obtained following the acid treatment into an acidic aqueous solution, followed by separating the particles dispersed in the aqueous solution and the precipitated particles, and subjecting the precipitated particles to a cleaning treatment and then collecting the particles.