{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T14:28:43Z","timestamp":1785421723085,"version":"3.56.0"},"reference-count":48,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2026,7,7]],"date-time":"2026-07-07T00:00:00Z","timestamp":1783382400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100012166","name":"National Key R&D Program of China","doi-asserted-by":"crossref","award":["2022YFA1203303"],"award-info":[{"award-number":["2022YFA1203303"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["52172089"],"award-info":[{"award-number":["52172089"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"award":["52172089"],"award-info":[{"award-number":["52172089"]}],"id":[{"id":"https:\/\/ror.org\/01h0zpd94","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Carbon nanotube (CNT) films prepared via floating catalyst chemical vapor deposition generally suffer from residual iron impurities, structural defects, and weak inter-tube interfaces, which severely limit their mechanical performance. Here, we propose a post-treatment approach, which is dominated by Joule heating, to substantially improve the mechanical properties of CNT films. Acid washing after Joule heating effectively removes iron catalyst and amorphous carbon, increasing the specific strength from 0.64 N\/tex to 2.96 N\/tex. Pre-stretching induces alignment of the CNTs along the stretching direction, further raising the specific strength to 5.57 N\/tex. Subsequent Joule heating not only raises graphitization degree and repairs lattice defects but also transforms the weak van der Waals contacts between tubes into continuous carbon networks, leading to network densification and locking of the aligned structure. The final specific strength reaches 7.04 N\/tex and true tensile strength 8.05 GPa, surpassing previous representative carbon materials. The purification mechanism of Joule heating depends on the initial iron content of the film: for high-iron films, iron melts, migrates and forms Fe\/Fe3C@C core\u2013shell particles, which can be converted into hollow carbon shells via acid etching; for low-iron films, iron is removed via atomic diffusion and evaporation. This work provides a fast, controllable and synergistic technical route for the preparation of high-performance CNT macrostructures.<\/jats:p>","DOI":"10.3390\/ma19132917","type":"journal-article","created":{"date-parts":[[2026,7,7]],"date-time":"2026-07-07T09:53:46Z","timestamp":1783418026000},"page":"2917","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Large Improvement of the Mechanical Strength of Carbon Nanotube Films by Joule Heating Dominated Post Treatments"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0009-0004-4295-6462","authenticated-orcid":false,"given":"Zujia","family":"Hu","sequence":"first","affiliation":[{"name":"School of Materials Science and Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yifan","family":"Feng","sequence":"additional","affiliation":[{"name":"School of Materials Science and Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Heng","family":"Zhang","sequence":"additional","affiliation":[{"name":"School of Materials Science and Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kangfei","family":"Liu","sequence":"additional","affiliation":[{"name":"School of Mechanical and Power Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xinran","family":"Cheng","sequence":"additional","affiliation":[{"name":"School of Materials Science and Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yunxiao","family":"Du","sequence":"additional","affiliation":[{"name":"School of Materials Science and Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2766-1904","authenticated-orcid":false,"given":"Jiannong","family":"Wang","sequence":"additional","affiliation":[{"name":"School of Mechanical and Power Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,7,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1624","DOI":"10.1016\/j.carbon.2006.02.038","article-title":"Small but strong: A review of the mechanical properties of carbon nanotube-polymer composites","volume":"44","author":"Coleman","year":"2006","journal-title":"Carbon"},{"key":"ref_2","first-page":"47","article-title":"Raman spectroscopy of carbon nanotubes","volume":"409","author":"Dresselhaus","year":"2005","journal-title":"Phys. Rep.-Rev. Sec. Phys. Lett."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"101763","DOI":"10.1016\/j.mtchem.2023.101763","article-title":"Recent advances in the mechanical and electrical performance of carbon nanotube fibers under various strain-rate loadings","volume":"34","author":"Zhou","year":"2023","journal-title":"Mater. Today Chem."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"5898","DOI":"10.3390\/ma15175898","article-title":"Synthesis, Sorting, and Applications of Single-Chirality Single-Walled Carbon Nanotubes","volume":"15","author":"Kharlamova","year":"2022","journal-title":"Materials"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1237","DOI":"10.1002\/smll.201203252","article-title":"The Road for Nanomaterials Industry: A Review of Carbon Nanotube Production, Post-Treatment, and Bulk Applications for Composites and Energy Storage","volume":"9","author":"Zhang","year":"2013","journal-title":"Small"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"3387","DOI":"10.1002\/adma.201100344","article-title":"Superstrong Ultra long Carbon Nanotubes for Mechanical Energy Storage","volume":"23","author":"Zhang","year":"2011","journal-title":"Adv. Mater."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"106359","DOI":"10.1016\/j.compositesa.2021.106359","article-title":"Continuous growth of carbon nanotube films: From controllable synthesis to real applications","volume":"144","author":"Wu","year":"2021","journal-title":"Compos. Part A Appl. Sci. Manuf."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"125103","DOI":"10.1063\/5.0038937","article-title":"Strongly anisotropic field emission from highly aligned carbon nanotube films","volume":"129","author":"Fairchild","year":"2021","journal-title":"J. Appl. Phys."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"105101","DOI":"10.1063\/5.0033442","article-title":"Effects of the nanotube length and network morphology on the deformation mechanisms and mechanical properties of cross-linked carbon nanotube films","volume":"129","author":"Banna","year":"2021","journal-title":"J. Appl. Phys."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"545","DOI":"10.1080\/1536383X.2010.488073","article-title":"Modification of Single-Walled Carbon Nanotubes by Ammonium Sulfamate","volume":"18","author":"Lian","year":"2010","journal-title":"Fuller. Nanotub. Carbon Nanostruct."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"119317","DOI":"10.1016\/j.carbon.2024.119317","article-title":"Purification of carbon nanotubes for dissolution in chlorosulfonic acid","volume":"228","author":"Taylor","year":"2024","journal-title":"Carbon"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"97012","DOI":"10.1039\/C6RA21238G","article-title":"Effective enhancement of the mechanical properties of macroscopic single-walled carbon nanotube fibers by pressure treatment","volume":"6","author":"Hou","year":"2016","journal-title":"RSC Adv."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2200623","DOI":"10.1002\/admt.202200623","article-title":"A Facile Strategy to Densify Aligned CNT Films with Significantly Enhanced Thermal Conductivity and Mechanical Strength","volume":"7","author":"Wu","year":"2022","journal-title":"Adv. Mater. Technol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"349","DOI":"10.1002\/adem.201400045","article-title":"Strain-Induced Alignment Mechanisms of Carbon Nanotube Networks","volume":"17","author":"Downes","year":"2015","journal-title":"Adv. Eng. Mater."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"116290","DOI":"10.1016\/j.rser.2025.116290","article-title":"Joule heating for carbon material Synthesis: Mechanisms, material evolution, and sustainable prospects","volume":"226","author":"Pan","year":"2026","journal-title":"Renew. Sust. Energ. Rev."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2506","DOI":"10.1021\/acsnano.2c10125","article-title":"Tunable Hybridized Morphologies Obtained through Flash Joule Heating of Carbon Nanotubes","volume":"11","author":"Advincula","year":"2023","journal-title":"ACS Nano"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"193","DOI":"10.1016\/j.carbon.2020.06.068","article-title":"Rapid, efficient, and non-destructive purification of single-walled carbon nanotube films from metallic impurities by Joule heating","volume":"168","author":"Romanov","year":"2020","journal-title":"Carbon"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"4323","DOI":"10.3390\/ma15124323","article-title":"Joule-Heating Effect of Thin Films with Carbon-Based Nanomaterials","volume":"15","author":"Sanivada","year":"2022","journal-title":"Materials"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"124319","DOI":"10.1063\/1.3671069","article-title":"Joule heating and thermoelectric properties in short single-walled carbon nanotubes: Electron-phonon interaction effect","volume":"110","author":"Jiang","year":"2011","journal-title":"J. Appl. Phys."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1025","DOI":"10.1016\/j.carbon.2022.10.006","article-title":"Nanometer-level temperature mapping of Joule-heated carbon nanotubes by plasmon spectroscopy","volume":"201","author":"Cretu","year":"2023","journal-title":"Carbon"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"119059","DOI":"10.1016\/j.carbon.2024.119059","article-title":"Towards the preparation of single-walled carbon nanotubes with average diameter of 1.2 nm","volume":"224","author":"Qin","year":"2024","journal-title":"Carbon"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"22318","DOI":"10.1021\/jp0631883","article-title":"Purification and opening of carbon nanotubes using steam","volume":"110","author":"Tobias","year":"2006","journal-title":"J. Phys. Chem. B"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"3389","DOI":"10.1039\/c2nr30226h","article-title":"Fabrication and processing of high-strength densely packed carbon nanotube yarns without solution processes","volume":"4","author":"Liu","year":"2012","journal-title":"Nanoscale"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"4215","DOI":"10.1039\/c1nr10571j","article-title":"Continuous electrodeposition for lightweight, highly conducting and strong carbon nanotube-copper composite fibers","volume":"3","author":"Xu","year":"2011","journal-title":"Nanoscale"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"2662","DOI":"10.1016\/j.carbon.2009.05.020","article-title":"Improving the tensile strength of carbon nanotube spun yarns using a modified spinning process","volume":"47","author":"Tran","year":"2009","journal-title":"Carbon"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1217","DOI":"10.1002\/smll.200700998","article-title":"Macroscopic Fibers of Well-Aligned Carbon Nanotubes by Wet Spinning","volume":"4","author":"Zhang","year":"2008","journal-title":"Small"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"884","DOI":"10.1126\/science.1066996","article-title":"Direct Synthesis of Long Single-Walled Carbon Nanotube Strands","volume":"296","author":"Zhu","year":"2002","journal-title":"Science"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"243","DOI":"10.1016\/j.matlet.2017.09.119","article-title":"Mechanical properties enhanced by solid-state coupling reaction for molecular covalent bridges of carbon nanotube fibers","volume":"211","author":"Kim","year":"2018","journal-title":"Mater. Lett."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"44","DOI":"10.1016\/j.carbon.2018.03.006","article-title":"Tensile properties of carbon nanotube fibres described by the fibrillar crystallite model","volume":"133","author":"Ridruejo","year":"2018","journal-title":"Carbon"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"689","DOI":"10.1016\/j.carbon.2020.07.058","article-title":"Improved properties, increased production, and the path to broad adoption of carbon nanotube fibers","volume":"171","author":"Taylor","year":"2021","journal-title":"Carbon"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"24","DOI":"10.1016\/j.carbon.2021.07.100","article-title":"Interfacial-bubbling-induced nondestructive expansion to reconstruct superstrong and multifunctional carbon nanotube fibers","volume":"184","author":"Wang","year":"2021","journal-title":"Carbon"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"4198","DOI":"10.1002\/adma.200700776","article-title":"Ultrastrong, Stiff, and Lightweight Carbon-Nanotube Fibers","volume":"19","author":"Zhang","year":"2007","journal-title":"Adv. Mater."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"eabn0939","DOI":"10.1126\/sciadv.abn0939","article-title":"Ultrahigh strength, modulus, and conductivity of graphitic fibers by macromolecular coalescence","volume":"8","author":"Lee","year":"2022","journal-title":"Sci. Adv."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"830","DOI":"10.1038\/nnano.2009.302","article-title":"True solutions of single-walled carbon nanotubes for assembly into macroscopic materials","volume":"4","author":"Davis","year":"2009","journal-title":"Nat. Nanotechnol."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"37112","DOI":"10.1021\/acsami.7b09287","article-title":"Purification and Dissolution of Carbon Nanotube Fibers Spun from the Floating Catalyst Method","volume":"9","author":"Tran","year":"2017","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"7948","DOI":"10.1021\/acsami.5b09912","article-title":"Post-Treatments for Multifunctional Property Enhancement of Carbon Nanotube Fibers from the Floating Catalyst Method","volume":"8","author":"Tran","year":"2016","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"7198","DOI":"10.1021\/am401524q","article-title":"Enhancing the Tensile Properties of Continuous Millimeter-Scale Carbon Nanotube Fibers by Densification","volume":"5","author":"Hill","year":"2013","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1402","DOI":"10.1016\/j.compscitech.2012.05.013","article-title":"Enhancement of carbon nanotube fibres using different solvents and polymers","volume":"72","author":"Li","year":"2012","journal-title":"Compos. Sci. Technol."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"2797","DOI":"10.1080\/01496395.2013.815628","article-title":"Recent Developments in Purification of Single Wall Carbon Nanotubes","volume":"49","author":"Makama","year":"2014","journal-title":"Sep. Sci. Technol."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"064514","DOI":"10.1063\/1.4960609","article-title":"Diameter-dependent hydrophobicity in carbon nanotubes","volume":"145","author":"Kyakuno","year":"2016","journal-title":"J. Chem. Phys."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"1477","DOI":"10.1016\/S0008-6223(03)00014-9","article-title":"Purification process for single-wall carbon nanotubes","volume":"41","author":"Strong","year":"2003","journal-title":"Carbon"},{"key":"ref_42","first-page":"129","article-title":"Sorting Carbon Nanotubes","volume":"Volume 375","author":"Zheng","year":"2017","journal-title":"Single-Walled Carbon Nanotubes"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"2429","DOI":"10.1021\/jp0142278","article-title":"Diameter-controlled synthesis of carbon nanotubes","volume":"106","author":"Cheung","year":"2002","journal-title":"J. Phys. Chem. B"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"452001","DOI":"10.1088\/1361-6528\/aa8ac9","article-title":"Recent progress on the structure separation of single-wall carbon nanotubes","volume":"28","author":"Cui","year":"2017","journal-title":"Nanotechnology"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"5844","DOI":"10.1021\/nl4026083","article-title":"Nanosoldering Carbon Nanotube Junctions by Local Chemical Vapor Deposition for Improved Device Performance","volume":"13","author":"Do","year":"2013","journal-title":"Nano Lett."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"329","DOI":"10.1016\/j.carbon.2019.09.069","article-title":"Controlled joule-heating of suspended glassy carbon wires for localized chemical vapor deposition","volume":"156","author":"Wardini","year":"2020","journal-title":"Carbon"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"085616","DOI":"10.1088\/2053-1591\/ab1e60","article-title":"Thermal conductivity enhancement of carbon@ carbon nanotube arrays and bonded carbon nanotube network","volume":"6","author":"Samani","year":"2019","journal-title":"Mater. Res. Express"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"1699","DOI":"10.1021\/nl0609910","article-title":"Real-time observation of tubule formation from amorphous carbon nanowires under high-bias Joule heating","volume":"6","author":"Huang","year":"2006","journal-title":"Nano Lett."}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/19\/13\/2917\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,7,9]],"date-time":"2026-07-09T04:27:53Z","timestamp":1783571273000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/19\/13\/2917"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,7,7]]},"references-count":48,"journal-issue":{"issue":"13","published-online":{"date-parts":[[2026,7]]}},"alternative-id":["ma19132917"],"URL":"https:\/\/doi.org\/10.3390\/ma19132917","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,7,7]]}}}