Thermal, Electrical and Thermoelectrical Characterisation of Laminates of 2d Materials

• Main Author: Pinter, Gergo
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2022
• Subjects: Analytical chemistry; Annealing; Chemistry; Electric properties; Electromagnetics; Electromagnetism; Expected values; Generators; Gold; Graphene; Graphite; Heat conductivity; Laminates; Lasers; Magnetic fields; Optics; Physics; Scanning electron microscopy; Spectrum analysis; Thermodynamics; Wire
• ISBN: 9798352642429

Methods for exfoliating materials down to atomically thin planes have been revolutionary in scientific research and industrial applications. Such methods can be used to exfoliate materials in a solution and then reconstruct the exfoliated nanosheets into flexible thin laminate films with advantageous properties.Reconstructed laminates of exfoliated 2D materials are particularly applicable for thermoelectric applications, converting between thermal and electrical energies.Flexible laminates of bulk high-performance thermoelectric materials can recover waste heat from ubiquitous sources. In this way, body heat, which would otherwise be lost to the surroundings, becomes a recoverable power source, enabling a future with selfpowered, energy-autonomous and connected wearable electronics.In this study, state-of-the-art brittle bulk thermoelectrics were reconstructed into flexible energy recovery devices. A single module, consisting of two different elements demonstrated a recovery power density of 0.65 mW/cm2 and peak output power of 1.95 µW across a 30 ◦C thermal difference. The addition of more modules increased the overall recovery. These methods demonstrate a scalable, low-temperature and solution-processable method of retaining high thermoelectric performance in a flexible form factor that allows for simple scaling of thermal energy recovery.Exfoliation methods were also used to create graphene paper samples with annealingtemperature-dependent thermoelectric properties. The resultant laminates were arranged into a highly sensitive thermocouple temperature sensor comparable to conventionally used wire variants. These flexible graphene paper thermocouples have potential applications in conformal temperature measurements above 1 000 ◦C in industrial machinery, amongst other uses.Due to their large specific surface area, the measurement of the thermal properties of high thermal conductivity thin laminate films is often challenging. Here, a self-heating 3ω thermal property measurement system was devised. Based on methods to measure thermal properties in wires, an adapted methodology, suited for thin laminate films, was achieved. Experimental requirements were rigorously defined and measurement sample geometries were comprehensively improved, leading to optimum thermal property measurements.Each of the explored areas, all concerning the thermal, electrical and thermoelectrical properties of thin laminate films of 2D materials, demonstrated numerous characterisation techniques and exceptional material properties, stimulating many further avenues for improvements and applications.