Team of Scientists from NUST MISIS and Merzhanov Institute of Structural Macrokinetics and Materials Science developed a technology that would eliminate the use of toxic beryllium powder in the production of bronze for use in microelectronics and high-precision sensors, such as motion and vibration sensors. The article is published in Journal of Alloys and Compounds.
Today, beryllium bronze (copper-beryllium alloy) is widely used for manufacturing contacts in microelectronics and high-precision sensors. Copper demonstrates excellent electrical conductivity, and the addition of beryllium increases the plasticity of the material: it becomes more malleable and wear-resistant. However, beryllium powder is toxic in production: when inhaled, it can cause poisoning and chronic disease. Alternatively, titanium bronze (copper-titanium alloy) can be used. This alloy is non-toxic, also wear-resistant, but has low electrical conductivity.
Scientists from NUST MISIS and Merzhanov Institute of Structural Macrokinetics and Materials Science proposed a method to increase the electrical conductivity of titanium bronze while maintaining its high mechanical properties.
“Titanium bronzes are even stronger than beryllium ones. This strength can be explained by the aging of a supersaturated solid solution of titanium in copper. But the residual titanium dissolved in the copper matrix significantly reduces the electrical conductivity of the material. Therefore, our task was to exclude titanium from the copper matrix, while preserving the mechanical properties of the material. We knew that many scientific teams tried to achieve this effect by annealing the alloy in the atmosphere of hydrogen. However, the conductivity was still not high enough”, comments Stepan Vorotylo, engineer at NUST MISIS Center for Self-Propagating High-Temperature Synthesis.
This time the scientists used a new method. They added hydrogen at the beginning, not during the annealing process. In the planetary mill, particles of titanium hydride TiH2 were introduced into the copper powder. Next, the mixture was hot-pressed, during which TiH2 was decomposed into titanium and hydrogen to form strengthening ceramic nanoparticles of copper-titanium oxide Cu3Ti3O. As the result, a material with a fairly high level of strength (920 MPa; twice as high as stainless steel; 1.5 times higher than aluminum bronze) and electrical conductivity (42% of the electrical conductivity of pure copper) was manufactured. For comparison, in the works of other teams, the electrical conductivity of titanium bronze did not exceed 30%.
In addition, due to its low thermal conductivity, the developed material is especially promising for use in thermoelectric devices, such as refrigeration elements and high-temperature solar concentrators (solar towers).