Platinum-Tungsten Sensor Wire for High-Temperature Strength
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Solution Overview
Problem
Dispersion-hardened platinum wires used for electrical contacting of temperature sensors face inadequate mechanical properties and high production costs, particularly under extreme conditions like car exhaust systems where high temperatures and mechanical stress are prevalent.
Innovation Solution
A platinum composition with at least 50% platinum, 2% to 3.5% tungsten, up to 47.95% noble metals like rhodium, gold, or palladium, and 0.05% to 1% oxides of zirconium, aluminum, or scandium, which is dispersion-hardened to improve mechanical strength and processability, is used to create wires with high tensile strength and elongation at break.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dispersion-hardened platinum is used for electrical contacting of temperature sensors, then corrosion resistance is improved, but mechanical properties are inadequate
Solution Approach 1:
The patent creates a composite material by combining dispersion-hardened platinum with a copper core. The platinum outer layer provides excellent corrosion resistance for use in exhaust gas atmospheres, while the copper core contributes superior mechanical properties including tensile strength and elongation. This composite structure resolves the contradiction by allowing each material to contribute its advantageous properties to the overall wire performance.
Solution Approach 2:
The patent modifies the compositional parameters of the wire by introducing a multi-layer structure with specific thickness ratios. The platinum layer thickness is controlled at 1-10 μm while the copper core provides the remaining cross-section. This parameter optimization ensures the platinum provides sufficient corrosion protection while the copper maintains adequate mechanical strength, resolving the contradiction between corrosion resistance and mechanical properties.
2Reliability
If traditional platinum compositions are used, then corrosion resistance is maintained, but production costs are high
Solution Approach 1:
The patent replaces expensive platinum with a more economical copper core for the bulk of the wire structure, using platinum only as a thin protective outer layer (1-10 μm). This approach maintains the necessary corrosion resistance for the application while dramatically reducing the amount of precious metal required, thereby lowering production costs while preserving the essential corrosion-resistant functionality.
Solution Approach 2:
The composite wire structure combines inexpensive copper with a minimal amount of platinum coating. The copper provides the bulk mechanical structure at low cost, while the thin platinum layer provides the necessary corrosion protection. This composite approach resolves the contradiction by achieving the required reliability at a fraction of the cost of solid platinum wires.
3Strength
If wire strength is increased through dispersion hardening, then mechanical properties improve, but elongation at break decreases
Solution Approach 1:
The patent uses a composite structure where the copper core provides high ductility and elongation capability, while the platinum outer layer provides dispersion hardening for increased strength. The copper's inherent ductility compensates for the brittleness introduced by dispersion hardening in the platinum layer, resolving the contradiction between strength and elongation at break.
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 resulting wires exhibit tensile strengths of at least 300 MPa and elongation at break of at least 12%, maintaining mechanical properties even at temperatures over 1300°C, making them suitable for extreme conditions in car exhaust systems while reducing material costs.
Implementation Method 1
oxidized in a subsequent oxidation process to zirconium oxide (ZrO 2 ), yttrium oxide (Y 2 O 3 ) and scandium oxide (SC 2 O 3 )
Implementation Method 2
maintaining mechanical properties even at temperatures over 1300°C
Data Source
AI summary
The invention relates to a wire for the electrical contacting of temperature sensors, wherein the wire consists of at least 50 wt% of a platinum composition, the platinum composition containing between 2 wt% and 3.5 wt% tungsten, up to 47.95 wt% of at least one precious metal selected from the group consisting of rhodium, gold, iridium, and palladium and mixtures thereof, between 0.05 wt% and 1 wt% oxides of at least one non-precious metal selected from the group consisting of (i) zirconium, (ii) aluminum, and (iii) zirconium and at least one element selected from aluminum, yttrium, and scandium, and the remainder being at least 50 wt% platinum including impurities. The invention also relates to a temperature sensor with such a wire and to a method for producing such a wire and such a temperature sensor.