Dense Particle Shell Coating via Cold Isostatic Pressing
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Solution Overview
Problem
Existing coating methods result in loosely bonded and low-density coatings on particles, leading to poor adherence during handling and processing, and high-temperature processes induce stress due to thermal expansion mismatches.
Innovation Solution
A method involving isostatic pressing of a mixture of core particles with a pressing medium to densify the shell coating, followed by removal of the medium, ensuring a stronger bond and uniform coverage without thermal stress, using a cold process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional coating methods (powder agitation/vibration, acoustic mixing, or ultrasonic mixing) are used to apply smaller particles onto core particles, then coating coverage is achieved, but the coating becomes loosely bonded with low density
Solution Approach 1:
The patent applies preliminary action by first forming a slurry coating on the core particles before sintering. The slurry contains coating particles, binder, and solvent that are applied to the core particles in advance. During subsequent sintering, the binder burns out creating voids that allow coating particles to densify and bond strongly to the core particles, resolving the contradiction between coverage and bond strength.
Solution Approach 2:
The patent utilizes parameter changes by transforming the coating from a loose powder state to a densified state through controlled sintering. The sintering process changes temperature, pressure, and time parameters to densify the coating particles and strengthen their bonding to the core particles, achieving both coverage and strong bonding simultaneously.
2Temperature
If high-temperature processes are used to apply coatings, then coating formation is achieved, but thermal expansion mismatch induces stress
Solution Approach 1:
The patent applies local quality by using different materials with matched thermal expansion coefficients in different regions of the composite particle. The core particles and coating particles are selected to have compatible thermal expansion properties, so when the coating is applied at high temperature, minimal thermal stress is generated due to the matched local properties of adjacent materials.
3Ease of operation
If loosely bonded coatings are used on particles, then handling and processing is easier, but adherence deteriorates during handling and processing
Solution Approach 1:
The patent applies preliminary action by forming a slurry coating with binder materials before sintering. The binder holds the coating particles in place on the core particles during handling and processing. During subsequent sintering, the binder burns out creating voids that allow the coating particles to densify and bond strongly to the core particles, ensuring adherence is maintained throughout handling and processing operations.
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
Achieves a denser coating with improved adherence and electrical resistivity, reducing eddy current losses and maintaining magnetic properties in soft magnetic composites, suitable for high-frequency applications.
Implementation Method 1
isostatic pressing the initial powder within the pressing medium to densify the initial shell coating on the plurality of core particles
Implementation Method 2
mixing the initial powder with a pressing medium; isostatic pressing the initial powder within the pressing medium
Data Source
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AI summary
Methods of forming a coating are presented. For example, a method (200) for forming a coating on particles may include mixing (204) an initial powder (100) with a pressing medium (110), the initial powder comprising a plurality of core particles (102) having an initial shell coating (104) thereon; isostatic pressing (206) the initial powder within the pressing medium to densify the initial shell coating on the plurality of core particles to form a pressed powder (120), the pressed powder comprising a densified shell coating (122) on the plurality of core particles; and thereafter, removing (208) the pressing medium from the pressed powder.