Low thermal conductivity and enhanced zT values of porous and nanostructured Cu_1−xNi_x alloys

Battery is sealed inside the sensor of direct tire-pressure monitoring system (dTPMS) and cannot be replaced separately. Durable thermoelectric generators can convert heat to direct-current (DC) power and is therefore an option for energizing dTPMS. Cu-Ni alloys have good thermoelectric responses to the temperature difference and therefore could be applied to act as temperature sensors as well as power supply for sensors of dTPMS. In this study, two series of Cu_1−xNi_x alloys are synthesized using hydrothermal synthesis followed by consolidation using different methods: evacuating-and-encapsulating techniques and a combination of cold pressing and heat treatment in 550 °C for 6 h in a flowing mixture gas of 20% H₂ and 80% Ar gas. The resulting materials are characterized and analyzed by powder x-ray diffraction, field-emission scanning electron microscopy, high resolution transmission electron microscopy, inductively coupled plasma optical emission spectroscopy, and thermoelectric transport measurements. The zT = 0.30 at 563 K is attained for the x = 0.4 alloy consolidated at 550 °C for 6 h in a flowing mixture gas of 20% H₂ and 80% Ar gas. By sintering the x = 0.3 alloy in an evacuated-and-encapsulated Pyrex ampoule, zT = 0.47 is attained at 550 K.