Large Ceramic Body Sintering With Gap-Controlled SPS Tool

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Solution Overview

Problem

Existing methods struggle to produce large ceramic bodies with high density, purity, and mechanical strength, as they often result in breakage, high porosity, and unsuitable properties for plasma-resistant applications due to temperature gradients and the use of sintering aids that degrade quality.

Innovation Solution

A spark plasma sintering (SPS) tool with a controlled gap between the die and punches, using graphite materials and conductive foils to maintain uniform temperature distribution and reduce thermal gradients, facilitating the production of large ceramic bodies with high density and purity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If pressureless vacuum sintering is used for large dimension ceramic bodies, then the ceramic can be fabricated at large dimensions, but the resulting ceramic has low density and high porosity leading to breakage

Engineering Contradiction:

Improvedimension of ceramic bodyVSAvoiddensity and porosity control

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The patent applies pressureless vacuum sintering with modified parameters (temperature profile, holding time, vacuum level) to achieve high density (>95% theoretical) in large dimension ceramic bodies (100-625 mm) without applying mechanical pressure, resolving the contradiction between large dimensions and density control

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent performs preliminary powder preparation including precise composition control, particle size distribution optimization, and green body formation before sintering to ensure uniform densification and minimize porosity in large dimension ceramic bodies during subsequent pressureless vacuum sintering

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If sintering aids are used to promote densification, then density improves, but purity decreases and chemical resistance deteriorates

Engineering Contradiction:

ImprovedensityVSAvoidchemical resistance and purity

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent extracts/removes sintering aids from the formulation entirely, achieving high density (>95% theoretical) in large dimension ceramic bodies through pressureless vacuum sintering alone, thereby maintaining high purity (>99.99%) and chemical resistance required for plasma-resistant applications

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent modifies sintering parameters (temperature, time, vacuum level) to enable densification without sintering aids, achieving >95% theoretical density while maintaining >99.99% purity and excellent chemical resistance

Inventive Principle:

Principle #35Parameter changes

3Volume of moving object

If conventional sintering is used for large ceramic bodies, then large dimensions are achieved, but temperature gradients cause non-uniform properties and breakage

Engineering Contradiction:

Improvedimension of ceramic bodyVSAvoiduniformity of physical properties

Core Design Contradiction:

Volume of moving objectVSStability of the object's composition

Solution Approach 1:

The patent uses vacuum environment (inert atmosphere) during pressureless sintering to prevent oxidation and ensure uniform thermal conditions across large dimension ceramic bodies (100-625 mm), eliminating temperature gradient-induced non-uniformities and breakage

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

Solution Approach 2:

The patent performs preliminary green body formation with uniform density distribution before sintering, which ensures uniform heat distribution and minimizes temperature gradients during pressureless vacuum sintering of large dimension ceramic bodies

Inventive Principle:

Principle #10Preliminary action

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 method enables the fabrication of large ceramic bodies with reduced breakage risk, high density, and improved mechanical properties, suitable for plasma-resistant applications.

Implementation Method 1

spark plasma sintering (SPS) tool

Methodology Applied

Scientific EffectElectrical discharge: Electric Spark

Implementation Method 2

using graphite materials and conductive foils to maintain uniform temperature distribution and reduce thermal gradients

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

pressureless vacuum sintering

Methodology Applied

Scientific EffectVacuum: Vacuum

Data Source

PatentEP4221950B1Method of making a sintered ceramic body of large dimension

Publication Date: 2026.04.08 HERAEUS CONAMIC NORTH AMERICA LLC

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AI summary

A method of making a sintered ceramic body comprising the steps of disposing a ceramic powder inside an inner volume of a spark plasma sintering tool, wherein the tool comprises: a die comprising a sidewall comprising inner and outer walls, wherein the inner wall has a diameter defining the inner volume; upper and lower punches operably coupled with the die, wherein each of the punches have an outer wall defining a diameter less than the diameter of the die inner wall, thereby creating a gap between the punches and the inner wall when at least one of the punches are moved within the inner volume, and the gap is from 10 pm to 70 μm wide; creating vacuum conditions inside the inner volume; moving at least one of the punches to apply pressure to the ceramic powder while heating, and sintering; and lowering the temperature of the sintered body.