Ceramic Molded Body Warm Isostatic Pressing
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Solution Overview
Problem
Conventional methods for producing ceramic sintered bodies face challenges in reducing residual voids and internal stress, leading to diminished mechanical strength, thermal conductivity, and optical transparency, particularly when using thermoplastic resins in the molding process.
Innovation Solution
A method involving the preparation of a raw material powder slurry with a ceramic powder and a thermoplastic resin having a glass transition temperature higher than room temperature, followed by isostatic pressing at a temperature lower than the resin's glass transition temperature, and subsequent warm isostatic pressing above the glass transition temperature to achieve both pressure transmission and plastic flow, resulting in a dense ceramic molded body with reduced residual voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermoplastic resin is mixed with ceramic powder for press-molding, then shape retaining property and crushing strength are improved, but plastic flow is hindered and large internal residual stress is generated
Solution Approach 1:
The patent applies temperature parameter changes to resolve the contradiction. By heating the thermoplastic resin above its glass transition temperature during isostatic pressing, the resin transitions from a rigid state to a plastic state, enabling plastic flow while maintaining shape retention. This temperature parameter change allows the resin to simultaneously provide structural support and facilitate densification without generating excessive residual stress.
Solution Approach 2:
The patent introduces dynamic control of the resin's mechanical properties through temperature variation. The resin's behavior is dynamically adjusted: below glass transition temperature for shape retention during initial molding, and above glass transition temperature for plastic flow during densification. This dynamic property adjustment resolves the contradiction between maintaining shape and enabling plastic flow.
2Shape
If thermoplastic resin is mixed with ceramic powder for press-molding, then shape retaining property is improved, but plastic flow of raw material powder and granules is hindered
Solution Approach 1:
The patent uses temperature parameter changes to control the resin's mechanical properties. By heating above the glass transition temperature during the densification stage, the resin becomes plastic and allows powder flow while maintaining shape. This parameter change enables simultaneous achievement of shape retention and plastic flow.
Solution Approach 2:
The patent employs periodic action through multi-stage pressing with temperature variation. The process alternates between low-temperature pressing for shape formation and high-temperature pressing for densification. This periodic temperature and pressure control allows the resin to alternately provide shape retention and facilitate plastic flow, resolving the contradiction.
3Productivity
If conventional press-molding is used for thick ceramics, then high yield is achieved, but residual bubbles remain inside the sintered body
Solution Approach 1:
The patent applies temperature parameter changes during isostatic pressing to enable plastic flow of the thermoplastic resin. By heating above the glass transition temperature, the resin becomes more compliant and allows complete pressure transmission throughout the thick molded body, eliminating residual bubbles while maintaining high yield. This resolves the contradiction between productivity and molding precision.
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 effectively reduces residual voids and stress, enhancing the mechanical strength, thermal conductivity, and optical transparency of the ceramic sintered bodies, producing high-quality materials with improved properties.
Implementation Method 1
the temperature is raised to a temperature region in which the thermoplastic resin is thermally softened at the time of isostatic pressing
Implementation Method 2
a thermoplastic resin having a glass transition temperature higher than room temperature
Data Source
AI summary
A method of fabricating a ceramic molded body for sintering, which includes molding a raw material powder containing a ceramic powder and a thermoplastic resin having a glass transition temperature higher than room temperature into a predetermined shape by isostatic pressing and in which a raw material powder slurry is prepared by adding the ceramic powder and the thermoplastic resin to a solvent so that the thermoplastic resin is 2% by weight or more and 40% by weight or less with respect to a total weight of the ceramic powder and the thermoplastic resin, a cast-molded body is formed by wet-casting the raw material powder slurry into a predetermined shape, dried, and subjected to first-stage isostatic press molding at a temperature lower than the glass transition temperature of the thermoplastic resin to form a first-stage press-molded body, then this first-stage press-molded body is heated to a temperature equal to or higher than the glass transition temperature of the thermoplastic resin, and warm isostatic press (WIP) molding is performed as second-stage isostatic press molding to fabricate a ceramic molded body.