Synthesis and thermoelectric properties of Fe-Ti-Al based alloys

Singh, Sukhwinder ORCID: https://orcid.org/0000-0002-4788-8292 2022. Synthesis and thermoelectric properties of Fe-Ti-Al based alloys. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Thermoelectric materials usually refer to the materials that can use temperature difference to generate electricity, which has potential to contribute to clean energy and environment. The drawback associated with the current thermoelectric materials is that these materials usually contain highly toxic, expensive and less earth-abundant elements, which limit their economic viability of large-scale applications. This study explores the possibility of developing economically viable thermoelectric materials based on Fe-Ti-Al alloys, which are low-cost, abundant, and less-toxic. The first stage of this research focused on establishing suitable preparation conditions (such as ball milling period, cold pressing pressure, and annealing temperature) that enables fabrication of Fe11Ti3Al6 alloys with satisfactory thermoelectric properties and offers a convenient route for substitution experiments. The samples prepared after 5 hours of ball milling, followed by cold pressing under 2200 MPa and annealing at 700 0C exhibit a power factor of 12x10-5 W/mk2 with a Seebeck coefficient of 32.3µV/K and electrical resistivity of 8.6µΩm. The second stage of the research investigates the possibility of further improving thermoelectric properties of Fe11Ti3Al6 alloy through elemental substitution. A systematic investigation was carried out by substituting Fe using an element from Group V-VII (V, Mn, Cr, W, Mo) or Group IX-X (Co and Ni). It is found that the substitution using Group V-VII element resulted in an increase in the Seebeck coefficient by 6 - 32% while the substitution using Group IX-X element led to a transition from p-type to n-type – a phenomenon normally associated with semiconductors only. The final stage of the research focused on preparation and characterisation of Fe10Cr1Ti3Al6 alloy (identified in the second stage of the research) using Spark Plasma Sintering (SPS), which facilitates preparation of high-density materials. The samples prepared using the SPS technique exhibit a significantly improved power factor of 64x10-5 W/mK2 , which is approximately 5 times higher than that prepared by cold pressing and annealing. The thermoelectric properties as a function temperature were also characterised. The results show that the peak ZT of 0.02 was achieved at 98 0C.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Engineering
Uncontrolled Keywords:	1). Intermetallic 2). Spark Plasma sintering 3). Thermoelectrics 4). Mechanical alloying
Date of First Compliant Deposit:	4 May 2023
Last Modified:	04 May 2024 01:30
URI:	https://orca.cardiff.ac.uk/id/eprint/159206

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