Browsing by Author "White, Alvin Orbaek"

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    Enhanced thermoelectricity in Bi-sprayed bismuth sulphide particles
    (Elsevier, 2023) Mulla, Rafiq; Kiani, Sajad; White, Alvin Orbaek; Dunnill, Charles W.; Barron, Andrew R.
    Bismuth sulphide (Bi2S3), an n-type semiconductor that critically demonstrates the Seebeck effect with Seebeck coefficients of about 300 μVK−1. However, its poor electrical conductivity makes it unsuitable for thermoelectric applications. In this study, we present a facile preparation method for fabricating Bi-sprayed Bi2S3 particles that alters their thermoelectric properties. Samples were created with differing Bi concentrations into the Bi2S3 compound to test for enhanced thermoelectric properties of the resulting Bi/Bi2S3 composites. The incorporation of excess Bi into Bi2S3 significantly improves the compound's electrical conductivity and optimises overall thermoelectric performance. The electrical conductivity of the Bi/Bi2S3 composites improved from 6.5 Scm−1 (for pristine Bi2S3) to 154 Scm−1 (for highest Bi added Bi2S3). Although the Seebeck coefficient of samples decreased with Bi incorporation, a high power factor (∼390 μWm−1K−2) has been achieved for an optimised composition of the composite. Incorporation of metallic Bi has led to an increase in the thermal conductivity of the samples, but the increase is not significant for the optimised composition of the composites where a high thermoelectric performance has been observed. Therefore, enhanced power factor and moderate thermal conductivity have resulted in a peak ZT value of 0.11 at room temperature. The strategy proposed here improves the thermoelectricity in Bi2S3 and shows excellent potential for developing better-performing thermoelectric compounds with excess elemental contents.
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    The role of graphene in new thermoelectric materials
    (Royal Society of Chemistry, 2023) Mulla, Rafiq; White, Alvin Orbaek; Dunnill, Charles W.; Barron, Andrew R.
    Graphene has high electrical conductivity, making it an attractive material for thermoelectric applications. However, its high thermal conductivity is a major challenge, and initial studies indicate that using pristine graphene alone cannot achieve optimal thermoelectric performance. Therefore, researchers are exploring ways to improve thermoelectric materials by either leveraging graphene's high intrinsic electrical conductivity or compounding graphene with additives to reduce the intrinsic thermal conductivity of the materials. Therefore, the research focus is now being shifted to graphene composites, primarily with polymer/organic conductors. One promising avenue of research is the development of graphene composites with polymer or organic conductors, which have shown some improvements in thermoelectric performance. However, the achieved “dimensionless figure of merit (ZT)” values of these composites are still far lower than those of common inorganic semiconductors. An alternative approach involves incorporating a very small amount of graphene into inorganic materials to improve their overall thermoelectric properties. These new concepts have successfully addressed the detrimental effects of graphene's intrinsic thermal conductivity, with the added interfaces in the matrix due to the presence of graphene layers working to enhance the properties of the host material. The use of graphene presents a promising solution to the longstanding challenge of developing high-performance and cost-effective thermoelectric materials. This paper discusses these innovative research ideas, highlighting their potential for revolutionizing the field of thermoelectric materials.