PTC Ceramic Feedstock for Complex Geometries
Solution Overview
Problem
Conventional methods for processing ceramic materials with a positive temperature coefficient of electrical resistance (PTC-ceramics) are limited in forming complex geometries and introduce metallic impurities during processing, which can degrade the electrical properties of the final ceramic product.
Innovation Solution
A feedstock for injection molding is developed, comprising a ceramic filler and a binding matrix with a melting point lower than the ceramic filler, processed using tools with tungsten carbide coatings to minimize metallic impurities, ensuring less than 10 ppm of Fe, Al, Ni, and Cr, allowing for the production of PTC-ceramics with low resistivity and a steep resistance-temperature curve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional processing methods (continuous casting or extrusion) are used to form PTC-ceramic bodies, then simple geometries like discs or rectangles can be formed, but complex geometries cannot be achieved
Solution Approach 1:
The patent changes the processing method from conventional continuous casting or extrusion to injection molding, enabling the formation of complex geometries while maintaining manufacturing efficiency. This parameter change in the processing technique directly resolves the contradiction between geometry complexity and ease of manufacture
Solution Approach 2:
The patent introduces a specifically formulated feedstock as an intermediary material that enables injection molding of PTC-ceramics. This feedstock serves as a mediator between the desired complex geometry and the manufacturing process, allowing complex shapes to be formed through injection molding while controlling impurity introduction
2Reliability
If conventional processing methods are used, then processing is simpler, but metallic impurities are introduced that degrade electrical properties
Solution Approach 1:
The patent converts the potential harm of metallic impurities by using a feedstock formulation and processing method that minimizes impurity introduction. The injection molding process with controlled feedstock composition transforms the situation where impurities would normally degrade electrical properties into a process that maintains low impurity levels (<10 ppm), thereby preserving reliability
Solution Approach 2:
The patent applies local quality control by specifically addressing the chemical composition of the feedstock and the impurity generation at tool-contact interfaces. By controlling the local chemical environment during processing and using coated tools, the patent prevents metallic impurity introduction while maintaining overall process simplicity
3Object-generated harmful factors
If tools with high abrasion are used during feedstock preparation, then tool wear is higher, but metallic impurities are introduced into the feedstock
Solution Approach 1:
The patent introduces a protective coating on tool surfaces as an intermediary layer that prevents direct contact between the tool substrate and the ceramic filler. This coating acts as a mediator that reduces abrasion of the underlying tool material, thereby minimizing metallic impurity generation while maintaining tool functionality
Solution Approach 2:
The patent employs a coating layer on tools that can be relatively easily replaced or renewed compared to replacing entire tools. This approach treats the coating as a consumable protective layer that prevents tool wear and impurity generation, offering an economical solution to maintaining low impurity levels in the feedstock
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 PTC-ceramics with maintained electrical properties and the ability to create complex geometries, ensuring low resistivity and a steep resistance increase with temperature, while minimizing impurity-induced degradation.
Implementation Method 1
the surfaces of the tools contactable with the ceramic filler comprise a hard coating comprising tungsten carbide
Implementation Method 2
preparation of a ceramic filler convertible by sintering into a ceramic with a positive temperature coefficient of its electrical resistance (PTC-ceramic)
Implementation Method 3
a matrix for binding the filler
Data Source
Figure 1~2
Figure 3
AI summary
A feedstock and a method for preparing a feedstock is presented, the feedstock being injection moldable and having a content of metallic impurities of = 10 ppm.