Dense Particle Shell Coatings via 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.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional coating methods (powder agitation, 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 and low-density
Solution Approach 1:
The patent applies preliminary action by first forming a slurry coating on the core particles before drying and sintering. The slurry is applied while the particles are in a fluid state, allowing better penetration and adhesion to the core particle surfaces. After drying removes the liquid carrier and sintering bonds the particles, the coating achieves both coverage and strong bonding without requiring high-temperature thermal expansion processes.
2Strength
If high-temperature processes are used to form coatings, then coating bonding is improved, but thermal expansion mismatch induces stress
Solution Approach 1:
The patent changes the bonding parameters from high-temperature thermal processes to lower-temperature sintering processes. The slurry coating is dried and then sintered at temperatures sufficient to bond the particles together but below the thermal expansion mismatch threshold that causes stress. This parameter change allows achieving strong coating bonds without inducing thermal stress from expansion differences between core and coating materials.
3Ease of manufacture
If loosely bonded coatings are formed on particles, then coating application is simple, but adherence during handling and processing deteriorates
Solution Approach 1:
The patent uses a liquid carrier or binder as an intermediary substance in the slurry coating process. This intermediary allows the coating particles to be uniformly distributed and applied to the core particles in a simple mixing process. During subsequent drying and sintering, the intermediary is removed or transformed, leaving behind a strongly bonded coating structure. This intermediary enables both simple application and reliable adherence.
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 and more uniform coating with improved adherence, reducing eddy current losses and enhancing properties like electrical resistivity and oxidation protection in soft magnetic composites.
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
The pressing medium fills shell particle gaps and covers their outer surfaces, which allows pressure to be effectively applied on the shell particles
Implementation Method 3
removing the pressing medium from the pressed powder... heating the pressing medium containing the pressed powder to an evaporation temperature at an evaporation pressure such that the pressing medium evaporates from the pressed powder
Data Source
AI summary
Methods of forming a coating are presented. For example, a method for forming a coating on particles may include mixing an initial powder with a pressing medium, the initial powder comprising a plurality of core particles having an initial shell coating thereon; isostatic pressing the initial powder within the pressing medium to densify the initial shell coating on the plurality of core particles to form a pressed powder, the pressed powder comprising a densified shell coating on the plurality of core particles; and thereafter, removing the pressing medium from the pressed powder.