{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T10:10:02Z","timestamp":1760004602167,"version":"build-2065373602"},"reference-count":36,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2025,10,2]],"date-time":"2025-10-02T00:00:00Z","timestamp":1759363200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Guangxi Science and Technology Plan Project","award":["Gui Ke AB22035043"],"award-info":[{"award-number":["Gui Ke AB22035043"]}]},{"name":"Guangxi Industrial Technology Research Project","award":["CYY-HT2023-JSJJ-0033"],"award-info":[{"award-number":["CYY-HT2023-JSJJ-0033"]}]},{"name":"Guangxi Industrial Technology Research Project","award":["CYY-HT2023-JSJJ-0034"],"award-info":[{"award-number":["CYY-HT2023-JSJJ-0034"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Micron-sized near-spherical \u03b1-Al2O3 powders are widely used as thermal fillers due to their high thermal conductivity, high packing density, good flowability, and low cost. During the high-temperature calcination, the resulting \u03b1-Al2O3 powders often exhibit an aggregated worm-like morphology owing to limitations in solid-state mass transfer. Researchers have employed various mineralizers to regulate the morphology of \u03b1-Al2O3 powders; however, the preparation of micron-sized highly spherical \u03b1-Al2O3 powders via solid-state calcination is still a great challenge. In this work, micron-sized near-spherical \u03b1-Al2O3 powders were synthesized through high-temperature calcination using hydratable alumina (\u03c1-Al2O3) as precursor with water-soluble mineralizer ammonium fluoroborate (NH4BF4). \u03c1-Al2O3 can undergo a hydration reaction with water to form AlO(OH) and Al(OH)3 intermediates, serving as an excellent precursor. With the addition of 0.1 wt% NH4BF4, the product exhibits an optimal near-spherical morphology. Excessive addition (&gt;0.2 wt%), however, significantly promotes the transformation of \u03b1-Al2O3 from a near-spherical to a plate-like structure. Further studies reveal that the introduction of NH4BF4 not only modulates the crystal morphology but also effectively reduces the content of sodium impurities in the powder through a high-temperature volatilization mechanism, thereby enhancing the thermal conductivity of the powder. It is shown that the thermal conductivity of the micron-sized \u03b1-Al2O3\/ epoxy resin composites reaches 1.329 \u00b1 0.009 W\/(m\u00b7K), which is 7.4 times that of pure epoxy resin.<\/jats:p>","DOI":"10.3390\/ma18194589","type":"journal-article","created":{"date-parts":[[2025,10,2]],"date-time":"2025-10-02T16:18:33Z","timestamp":1759421913000},"page":"4589","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Preparation and Properties of Micron Near-Spherical Alumina Powders from Hydratable Alumina with Ammonium Fluoroborate"],"prefix":"10.3390","volume":"18","author":[{"given":"Yi","family":"Wei","sequence":"first","affiliation":[{"name":"College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 401331, China"},{"name":"Institute of New Functional Materials, Guangxi Institute of Industrial Technology, Nanning 530200, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6455-8896","authenticated-orcid":false,"given":"Jie","family":"Xu","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Solidification Processing, MIIT Key Laboratory of Radiation Detection Materials and Devices, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi\u2019an 710072, China"},{"name":"Shaanxi Shuimu Xusheng New Material Technology Co., Ltd., Xi\u2019an 710116, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jie","family":"Jiang","sequence":"additional","affiliation":[{"name":"Guangxi Key Laboratory of Information Materials, School of Materials Science and Engineering, Guilin University of Electronic Technology, Engineering Research Center of Electronic Information Materials and Devices, Ministry of Education, Guilin 541004, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tairong","family":"Lu","sequence":"additional","affiliation":[{"name":"Institute of New Functional Materials, Guangxi Institute of Industrial Technology, Nanning 530200, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zuohua","family":"Liu","sequence":"additional","affiliation":[{"name":"College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 401331, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,10,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"215706","DOI":"10.1088\/0957-4484\/19\/21\/215706","article-title":"Carbon nanotube thermal interface material for high-brightness light-emitting-diode cooling","volume":"19","author":"Zhang","year":"2008","journal-title":"Nanotechnology"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1049\/hve.2016.0008","article-title":"Review of high thermal conductivity polymer dielectrics for electrical insulation","volume":"1","author":"Xiao","year":"2016","journal-title":"High Volt."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"36","DOI":"10.1007\/s42114-021-00208-1","article-title":"Flexible thermally conductive and electrically insulating silicone rubber composite films with BNNS@Al2O3 fillers","volume":"4","author":"Yan","year":"2021","journal-title":"Adv. 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