Movable Susceptor for Uniform Zirconia Sintering
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Solution Overview
Problem
Existing sintering technologies, including microwave furnaces, struggle to achieve rapid and uniform sintering of dental ceramics like zirconia, particularly in minimizing heating time and ensuring homogeneity, translucency, and strength, while some ceramic materials do not effectively couple with microwaves, limiting their application.
Innovation Solution
A microwave furnace with a movable susceptor made of silicon carbide that couples with microwaves over a wide temperature range, allowing for selective positioning within and outside the furnace chamber, enabling efficient microwave energy transfer and minimizing heating time by using microwaves directly on the object, while maintaining uniform temperature gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional thermal sintering is used, then heating time is long, but temperature distribution is uniform
Solution Approach 1:
A susceptor made of silicon carbide is introduced as an intermediary component that absorbs microwave energy and converts it to thermal energy. The susceptor is positioned around the object to be sintered, acting as a mediator that transfers heat from microwaves to the object through thermal radiation and conduction, enabling rapid heating while maintaining temperature uniformity
Solution Approach 2:
The patent replaces conventional thermal conduction heating (which requires long heating times) with microwave electromagnetic field heating. The microwave source generates electromagnetic waves that directly interact with the susceptor, converting electromagnetic energy to thermal energy rapidly, thus substituting the traditional thermal diffusion process with a faster electromagnetic heating mechanism
2Loss of time
If microwave heating is used directly on ceramic materials like zirconia, then heating time is reduced, but the materials do not effectively couple with microwaves
Solution Approach 1:
The susceptor serves as a mediator between the microwave source and ceramic materials that do not couple well with microwaves. The susceptor material (silicon carbide) has high microwave coupling efficiency and absorbs microwave energy, then transfers this energy to the ceramic object through thermal radiation and conduction, enabling effective heating of materials like zirconia that would otherwise be difficult to heat with microwaves
Solution Approach 2:
The patent changes the heating mechanism parameter by introducing a susceptor with different electromagnetic properties than the ceramic material itself. The susceptor material is selected to have high dielectric loss tangent and electrical conductivity, transforming the heating approach from direct microwave heating of the ceramic to indirect heating via the susceptor, thereby overcoming the poor microwave coupling of certain ceramics
3Productivity
If a susceptor is used for microwave heating, then heating efficiency is improved, but additional heating systems and device complexity increase
Solution Approach 1:
The susceptor is designed to perform multiple functions: it acts as a microwave absorber, a heat transfer medium, and a structural support for the object. By combining these functions into a single component, the patent achieves high heating efficiency without proportionally increasing device complexity, as the susceptor integrates several roles that would otherwise require separate systems
Solution Approach 2:
The susceptor automatically adjusts its heating behavior based on its position relative to the microwave source and the object. When positioned close to the microwave source, it absorbs maximum energy and heats up, then transfers heat to the object through thermal radiation and conduction. This self-regulating behavior eliminates the need for complex control systems to manage heating parameters
4Manufacturing precision
If microwaves are used for sintering, then sintering quality and homogeneity are improved, but not all ceramic materials can be effectively sintered
Solution Approach 1:
The susceptor acts as a universal intermediary that enables microwave sintering of diverse ceramic materials including those with poor microwave coupling properties. The susceptor absorbs microwave energy and transfers it thermally to any material placed around it, making the system adaptable to various ceramic types (zirconia, alumina, dental ceramics, etc.) while maintaining the high sintering quality benefits of microwave heating
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 allows for rapid and uniform sintering of zirconia ceramics with enhanced homogeneity and translucency, reducing heating time and achieving strong, high-quality sintered materials without additional heating systems, and is particularly effective for materials that do not typically couple well with microwaves.
Implementation Method 1
The susceptor comprises or is formed of a material which over a temperature range of the material of at least 23° C. to 700° C. couples into microwaves
Implementation Method 2
microwave energy is typically converted by the susceptor into heat, which is emitted by the susceptor to the material to be sintered mainly by thermal radiation
Implementation Method 3
microwaves typically can penetrate into the object and thereby can heat up inner and outer portions of the object independently and simultaneously (volume heating effect)
Data Source
AI summary
A microwave furnace has a furnace chamber formed between a chamber housing and a sintering platform for an object to be sintered. A microwave source is arranged for emitting microwaves into the furnace chamber. The microwave furnace further has a susceptor that comprises a material which over a temperature range of the material of at least 23 C to 700 C couples into microwaves. The susceptor and the furnace chamber are movable relative to each other between a first position, in which the susceptor is positioned relative to the furnace chamber, and a second position in which the susceptor is positioned further retracted from the furnace chamber relative to the first position. The invention helps providing a zirconia material with a relative homogeneous material structure.