Copper-silver composite material
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Solution Overview
Problem
Existing composite materials of copper and silver struggle to balance mechanical strength with electrical conductivity, often introducing internal defects that reduce conductivity and requiring energy-intensive and costly processing methods.
Innovation Solution
A composite material with copper and silver grains of sub-micron size, less than 5% silver by volume, is created using a process involving dispersing particles in a non-solvent medium, drying, flash sintering, and cold drawing to achieve high electrical conductivity and mechanical strength without the need for repeated annealing or heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If copper-silver alloy with 24% silver by mass is used to improve breaking strength, then mechanical strength increases to about 1.5 GPa, but electrical conductivity decreases to about 65% IACS
Solution Approach 1:
The patent uses a composite material structure with copper matrix and dispersed silver particles (0.1-5% by volume) instead of a homogeneous alloy. This allows the copper to provide high electrical conductivity while the silver particles and nanocrystal structure provide mechanical strength, resolving the contradiction between conductivity and strength.
Solution Approach 2:
The patent creates local variations in structure with nanocrystal regions (10-100 nm) and dispersed silver particles throughout the copper matrix. This local structuring allows different regions to contribute different properties: the nanocrystal copper provides strength while the copper matrix maintains conductivity.
2Strength
If multiple heat treatment steps (500-700°C) and shaping steps are applied to manufacture copper-silver composite material, then breaking strength improves to approximately 970 MPa, but manufacturing complexity and energy consumption increase significantly
Solution Approach 1:
The patent performs preliminary actions during powder preparation by controlling particle size distribution and morphology before sintering. The copper powder is pre-treated to have specific surface characteristics that facilitate sintering at lower temperatures, eliminating the need for subsequent high-temperature heat treatments.
Solution Approach 2:
The patent changes the sintering parameters by using lower temperatures (below 500°C) combined with extended holding times and specific atmospheric conditions. This parameter modification achieves the desired density and strength without requiring multiple high-temperature cycles.
3Strength
If conventional sintering and multiple shaping steps are used to manufacture copper-silver composite, then mechanical properties improve, but internal defects such as grain boundaries and stacking faults are introduced, reducing electrical conductivity
Solution Approach 1:
The patent segments the material into very fine nanocrystals (10-100 nm) dispersed throughout the copper matrix. This segmentation creates numerous grain boundaries that strengthen the material while the extremely fine size and copper matrix continuity maintain electrical conductivity by providing short electron scattering paths.
Solution Approach 2:
The patent converts the typically harmful effect of grain boundaries into a beneficial strengthening mechanism. By creating ultra-fine nanocrystals, the grain boundaries provide strength through the Hall-Petch effect while the small size and copper continuity minimize their negative impact on electrical conductivity.
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 material achieves electrical conductivity greater than 75% IACS and breaking strength of at least 900 MPa, with a simple and economical process that avoids internal defects and energy-intensive steps, making it suitable for high-performance applications like pulsed magnets and high-voltage cables.
Implementation Method 1
a flash sintering step at a temperature of at most approximately 600°C, in order to obtain a composite solid mass
Implementation Method 2
The material achieves electrical conductivity greater than 75% IACS
Data Source
Figure 1a~1d
Figure 2~3
AI summary
The invention relates to a solid composite material comprising copper and a volume amount of silver of less than approximately 5% by volume, with respect to the total volume of said material, to a method for producing the material, and to the uses of said material in various applications.