Epsilon-Phase Magnetic Powder With Controlled Coercivity Distribution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic powders containing ε-Fe2O3 used in magnetic recording media suffer from signal decay due to the presence of superparamagnetic components, which affect durability and magnetic properties, despite efforts to control particle size and magnetic properties through ultrafiltration and crystal structure management.
Innovation Solution
Development of magnetic powders with epsilon-phase iron oxide-based compounds, specifically ε-AaFe2-aO3, with controlled particle diameters and magnetic field ratios, and a manufacturing method involving trivalent iron ions, alkali agents, polyvalent carboxylic acids, and heat treatment to minimize amorphous components and enhance magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If particle size distribution is narrowed and magnetic properties are adjusted to meet specifications, then magnetic properties are improved, but signal decay occurs and durability deteriorates
Solution Approach 1:
The patent changes the physical and chemical parameters of the magnetic powder by controlling the crystal phase composition (specifically the ratio of epsilon-phase to other phases), particle size distribution (average diameter 8-25 nm with controlled fine particle content), and magnetic field ratios (Hc/Hc' between 0.6-1.0). These parameter changes achieve both improved magnetic properties and resistance to signal decay, resolving the contradiction between manufacturing precision and reliability.
2Manufacturing precision
If ultrafiltration is used to remove unnecessary ions, then purity is improved, but amorphous components increase and fine particles are generated
Solution Approach 1:
The patent controls the chemical composition parameters during synthesis to achieve the desired purity while minimizing amorphous content. By optimizing the ratio of crystalline phases and controlling the particle size distribution through controlled synthesis conditions rather than post-synthesis ultrafiltration, the method achieves both ion purity and reduced amorphous component generation.
Solution Approach 2:
The patent performs preliminary control of the synthesis conditions to pre-determine the crystal phase composition and particle size distribution before any purification steps. This preliminary action ensures that the magnetic powder achieves the desired properties during formation, avoiding the need for aggressive ultrafiltration that would generate amorphous components.
3Manufacturing precision
If trivalent iron ion compounds are used to form magnetic powder precursor, then magnetic properties are improved, but amorphous portion increases
Solution Approach 1:
The patent optimizes the chemical composition parameters by controlling the ratio of trivalent iron ions to other metal ions, the pH conditions during precipitation, and the heating temperature range (800-1400°C). These parameter changes enable the formation of desired magnetic properties through epsilon-phase crystal structure while minimizing amorphous content by ensuring complete crystallization.
Solution Approach 2:
The patent utilizes phase transition during heat treatment to convert the precursor material into the desired epsilon-phase crystal structure. By controlling the heating temperature and duration, the method ensures complete phase transformation from amorphous or other crystalline phases to the epsilon-phase, thereby reducing amorphous content while maintaining improved magnetic properties.
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
The solution effectively prevents signal decay and improves magnetic properties by reducing superparamagnetic components, ensuring durability and performance in magnetic recording media.
Implementation Method 1
subjecting the magnetic powder precursor to heat treatment at a temperature condition of 800° C. to 1,400° C.
Implementation Method 2
in a case where a crystal structure is focused, the amount of an amorphous portion of metal powder increases, in a magnetic powder precursor formed under the conditions of a step of forming metal powder including iron
Implementation Method 3
removing a silicic acid compound in the heat-treated magnetic powder precursor by using an alkali aqueous solution
Implementation Method 4
Magnetic powders containing ε-Fe2O3 used in magnetic recording media suffer from signal decay due to the presence of superparamagnetic components
Data Source
AI summary
Magnetic powder includes: an epsilon-phase iron oxide-based compound selected from ε-Fe2O3 or a compound represented by Formula (1). The magnetic powder has an average particle diameter of 8 nm to 25 nm, a ratio of Hc to Hc′ of from 0.6 to 1.0, and Hc′ satisfying Expression (II). Hc′ represents a magnetic field at which a value of Expression (I) becomes zeroin a magnetic field-magnetization curve obtained by performing measurement at a maximum applied magnetic field of 359 kA/m, a temperature of 296 K, and a magnetic field sweeping speed of 1.994 kA/m/s. M represents magnetization and H represents applied magnetic field. Hc represents a magnetic field at which magnetization becomes zero in the magnetic field-magnetization curve. In Formula (1), A represents at least one metal element other than Fe, and a represents a number that satisfies a relationship of 0<a<2.d2M/dH2 Expression (I)119 kA/m<Hc′<2380 kA/m Expression (II)ε-AxFe2-xO3 (1)