{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,2]],"date-time":"2026-02-02T21:31:30Z","timestamp":1770067890809,"version":"3.49.0"},"reference-count":51,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2022,11,8]],"date-time":"2022-11-08T00:00:00Z","timestamp":1667865600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"FCT-Foundation for Science and Technology","award":["UID\/CTM\/00264\/2021 of 2C2T"],"award-info":[{"award-number":["UID\/CTM\/00264\/2021 of 2C2T"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>The thermoelectric properties, at temperatures from 30 \u00b0C to 100 \u00b0C, of melt-processed poly(ether ether ketone) (PEEK) composites prepared with 10 wt.% of carbon nanofibers (CNFs) are discussed in this work. At 30 \u00b0C, the PEEK\/CNF composites show an electrical conductivity (\u03c3) of ~27 S m\u22121 and a Seebeck coefficient (S) of \u22123.4 \u03bcV K\u22121, which means that their majority charge carriers are electrons. The origin of this negative Seebeck is deduced because of the impurities present in the as-received CNFs, which may cause sharply varying and localized states at approximately 0.086 eV above the Fermi energy level (EF) of CNFs. Moreover, the lower S, in absolute value, found in PEEK\/CNF composites, when compared with the S of as-received CNFs (\u22125.3 \u03bcV K\u22121), is attributed to a slight electron withdrawing from the external layers of CNFs by the PEEK matrix. At temperatures from 30 \u00b0C to 100 \u00b0C, the \u03c3 (T) of PEEK\/CNF composites, in contrast to the \u03c3 (T) of as-received CNFs, shows a negative temperature effect, understood through the 3D variable-range hopping (VRH) model, as a thermally activated hopping mechanism across a random network of potential wells. Moreover, their nonlinear S (T) follows the same behavior reported before for polypropylene composites melt-processed with similar CNFs at the same interval of temperatures.<\/jats:p>","DOI":"10.3390\/polym14224803","type":"journal-article","created":{"date-parts":[[2022,11,8]],"date-time":"2022-11-08T11:29:34Z","timestamp":1667906974000},"page":"4803","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["Thermoelectric Properties of N-Type Poly (Ether Ether Ketone)\/Carbon Nanofiber Melt-Processed Composites"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4688-5794","authenticated-orcid":false,"given":"Antonio Jose","family":"Paleo","sequence":"first","affiliation":[{"name":"2C2T-Centre for Textile Science and Technology, Campus Azurem, University of Minho, 4800-058 Guimar\u00e3es, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2892-1269","authenticated-orcid":false,"given":"Beate","family":"Krause","sequence":"additional","affiliation":[{"name":"Leibniz-Institut f\u00fcr Polymerforschung Dresden e.V. (IPF), Hohe Str. 6, 01069 Dresden, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1884-2380","authenticated-orcid":false,"given":"Delfim","family":"Soares","sequence":"additional","affiliation":[{"name":"CMEMS Research Center, Campus Azurem, University of Minho, 4800-058 Guimar\u00e3es, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1929-0477","authenticated-orcid":false,"given":"Manuel","family":"Melle-Franco","sequence":"additional","affiliation":[{"name":"CICECO\u2014Aveiro Institute of Materials, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4457-0817","authenticated-orcid":false,"given":"Enrique","family":"Mu\u00f1oz","sequence":"additional","affiliation":[{"name":"Facultad de F\u00edsica, Pontificia Universidad Cat\u00f3lica de Chile, Santiago 7820436, Chile"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6392-7880","authenticated-orcid":false,"given":"Petra","family":"P\u00f6tschke","sequence":"additional","affiliation":[{"name":"Leibniz-Institut f\u00fcr Polymerforschung Dresden e.V. (IPF), Hohe Str. 6, 01069 Dresden, Germany"}]},{"given":"Ana Maria","family":"Rocha","sequence":"additional","affiliation":[{"name":"2C2T-Centre for Textile Science and Technology, Campus Azurem, University of Minho, 4800-058 Guimar\u00e3es, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2022,11,8]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1573","DOI":"10.1002\/(SICI)1097-4628(19990620)72:12<1573::AID-APP10>3.0.CO;2-6","article-title":"Electrical properties of composites in the vicinity of the percolation threshold","volume":"72","author":"Foulger","year":"1999","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"377","DOI":"10.1023\/A:1006774318019","article-title":"The effect of particle size on electric conducting percolation threshold in polymer\/conducting particle composites","volume":"19","author":"Jing","year":"2000","journal-title":"J. Mater. Sci. 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