Spark Plasma Sintering Gap Control for Large Ceramic Density
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Solution Overview
Problem
Existing methods struggle to produce large sintered ceramic bodies with high density, purity, and mechanical strength, particularly for use in plasma processing chambers, due to challenges in controlling temperature gradients during spark plasma sintering and the use of sintering aids that compromise purity and alter material properties.
Innovation Solution
A method involving a spark plasma sintering tool with a specific gap between the die and punch system, along with controlled temperature management, to produce large sintered ceramic bodies with uniform density and reduced breakage risk, using graphite materials and ceramic powders with controlled specific surface area and resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If pressureless vacuum sintering is used at temperatures of 1600°C and greater for extended periods, then the ceramic body can be processed, but the resulting sintered ceramic has lower density and higher porosity which degrades performance
Solution Approach 1:
The patent applies pressureless sintering with controlled temperature profiles and extended time parameters to achieve high density without requiring high pressure. The process uses temperatures in the range of 1600-1800°C for extended periods (1-24 hours) to enable densification through diffusion mechanisms, achieving densities of 95% or more of theoretical density without the need for hot pressing or other high-pressure techniques.
2Manufacturing precision
If sintering aids are used to promote densification, then density improves, but purity decreases and material properties are altered in undesirable ways
Solution Approach 1:
The patent extracts or removes sintering aids from the formulation entirely, relying instead on optimized sintering parameters (temperature, time, atmosphere) to achieve densification. The ceramic composition consists of pure ceramic powder without added sintering aids, thereby maintaining high purity (99.9% or greater) while still achieving the required density through parameter-optimized pressureless sintering.
3Length of stationary object
If ceramic materials are prepared at large dimensions of 100 mm to 200 mm and greater, then the component size requirement is met, but the risk of breakage increases due to brittleness and defects
Solution Approach 1:
The patent performs preliminary actions during the sintering process to prevent defects that would lead to breakage. This includes using controlled heating and cooling rates, maintaining optimal atmosphere conditions, and applying gradual densification to avoid thermal shock and internal stresses. These preliminary controls during processing ensure that large-dimension ceramics (100-200 mm and greater) develop uniform microstructures without defects, thereby achieving the required reliability and breakage resistance.
4Manufacturing precision
If extended sintering time is used to improve density, then density increases, but production efficiency decreases
Solution Approach 1:
The patent optimizes the balance between temperature and time parameters to achieve high density without excessive processing time. By using temperatures in the range of 1600-1800°C with controlled heating rates and holding times of 1-24 hours, the process achieves densities of 95% or more of theoretical density while maintaining reasonable production efficiency. The optimized parameter combination prevents both under-densification and excessive processing time.
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 production of large sintered ceramic bodies with densities above 98% of theoretical, minimal density variation, and high purity, suitable for plasma processing chambers without breakage, and reduces erosion and corrosion resistance.
Implementation Method 1
spark plasma sintering tool with a specific gap between the die and punch system, along with controlled temperature management, to produce large sintered ceramic bodies with uniform density
Implementation Method 2
moving at least one of the upper punch and the lower punch to apply pressure to the ceramic powder while heating the ceramic powder to a sintering temperature
Data Source
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 μm 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.