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Spark plasma sintering and thermoelectric evaluation of nanocrystalline magnesium silicide (Mg2Si)
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.ORCID iD: 0000-0001-5380-975X
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.ORCID iD: 0000-0001-5678-5298
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2013 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 48, no 5, 1940-1946 p.Article in journal (Refereed) Published
Abstract [en]

Recently magnesium silicide (Mg2Si) has received great interest from thermoelectric (TE) society because of its non-toxicity, environmental friendliness, comparatively high abundance, and low production material cost as compared to other TE systems. It also exhibited promising transport properties, including high electrical conductivity and low thermal conductivity, which improved the overall TE performance (ZT). In this work, Mg2Si powder was obtained through high energy ball milling under inert atmosphere, starting from commercial magnesium silicide pieces (99.99 %, Alfa Aesar). To maintain fine microstructure of the powder, spark plasma sintering (SPS) process has been used for consolidation. The Mg2Si powder was filled in a graphite die to perform SPS and the influence of process parameters as temperature, heating rate, holding time and applied pressure on the microstructure, and densification of compacts were studied in detail. The aim of this study is to optimize SPS consolidation parameters for Mg2Si powder to achieve high density of compacts while maintaining the nanostructure. X-Ray diffraction (XRD) was utilized to investigate the crystalline phase of compacted samples and scanning and transmission electron microscopy (SEM & TEM) coupled with Energy-Dispersive X-ray Analysis (EDX) was used to evaluate the detailed microstructural and chemical composition, respectively. All sintered samples showed compaction density up to 98 %. Temperature dependent TE characteristics of SPS compacted Mg2Si as thermal conductivity, electrical resistivity, and Seebeck coefficient were measured over the temperature range of RT 600 A degrees C for samples processed at 750 A degrees C, reaching a final ZT of 0.14 at 600 A degrees C.

Place, publisher, year, edition, pages
2013. Vol. 48, no 5, 1940-1946 p.
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-117633DOI: 10.1007/s10853-012-6959-0ISI: 000312906400010Scopus ID: 2-s2.0-84879797497OAI: oai:DiVA.org:kth-117633DiVA: diva2:602463
Funder
Swedish Foundation for Strategic Research
Note

QC 20130201

Available from: 2013-02-01 Created: 2013-02-01 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Nano-EngineeredThermoelectric Materials for Waste Heat Recovery
Open this publication in new window or tab >>Nano-EngineeredThermoelectric Materials for Waste Heat Recovery
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Energy crisis and thermal management related issues have been highlighted in the modern century due to escalating demands for energy consumption and global warming from fossil fuels. Sustainable and alternative energy sources are an ever growing global concern. Thermoelectric (TE) materials have gained significant interest, due to effective solid-state energy conversion from waste heat to useful electrical energy and vice versa.   Clean, noise-free, and environment-friendly operation of TE devices has triggered great attention in viable technologies including automotive, military equipment, aerospace, and industries to scavenge waste heat into power. To date, conventional TE materials have shown limited energy conversion efficiency, i.e. TE Figure of Merit (ZT). However, the concept of nanostructuring and development of novel TE materials have opened excellent avenues to improve significantly the ZT values. Nano-engineered bulk TE materials allow effective phonon scattering at the high density of grain boundaries, which offer a way of lowering the thermal conductivity. 

Large-scale synthesis of TE nanomaterials is a challenge for the TE industry because of expensive fabrication processes involved. This thesis reports several nano-engineering approaches for fabricating large quantities of bulk nanostructured TE materials. We have developed bottom-up chemical synthesis routes, as well as top-down mechanical alloying methodologies, to produce highly pure, homogenous and highly crystalline TE nanomaterials. State of the art chalcogenide, iron antimonide, and silicide based TE materials have been investigated in this thesis. Chalcogenide are the best candidates for TE devices operating at temperature range up to 450 K.  Iron antimonide (FeSb2) have shown attractive performance below room temperature. Earth abundant and environment friendly, silicide based materials have better ZT performance in the range of 600-900 K.  Spark plasma sintering (SPS) was utilized to preserve the nanostructuring and to achieve the highest compaction density. Comprehensive physiochemical characterizations were performed on as-prepared and SPS compacted samples. Detailed TE evaluation of the fabricated materials showed significant improvement in ZT for all categories of TE materials.

Place, publisher, year, edition, pages
Stockholm 2014: KTH Royal Institute of Technology, 2014. xi, 52 p.
Series
TRITA-ICT/MAP AVH, ISSN 1653-7610 ; 2014:12
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-151363 (URN)978-91-7595-210-9 (ISBN)
Public defence
2014-10-03, SAl B, Electrum 229, Isafajordsgatan 22, Kista, 14:00 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency, 36656-1EU, FP7, Seventh Framework Programme, 263167Swedish Foundation for Strategic Research , EM11-0002EU, FP7, Seventh Framework Programme, 228882
Note

QC 20140918

Available from: 2014-09-18 Created: 2014-09-18 Last updated: 2014-09-18Bibliographically approved

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Saleemi, MohsinToprak, Muhammet S.

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