{"id":927,"date":"2026-06-09T15:50:58","date_gmt":"2026-06-09T13:50:58","guid":{"rendered":"https:\/\/segdielectriques.com\/en\/non-classe\/ceramic-fillers-thermal-composites-bn-aln-alumina\/"},"modified":"2026-06-09T15:50:58","modified_gmt":"2026-06-09T13:50:58","slug":"ceramic-fillers-thermal-composites-bn-aln-alumina","status":"publish","type":"post","link":"https:\/\/segdielectriques.com\/en\/article\/ceramic-fillers-thermal-composites-bn-aln-alumina\/","title":{"rendered":"Ceramic Fillers for Thermal Composites: BN, AlN and Alumina"},"content":{"rendered":"<p>To simultaneously achieve high thermal conductivity and impeccable electrical insulation, ceramic fillers are essential. An overview of the three best-performing candidates, their properties and their application limits.<\/p>\n<h2>Boron nitride (BN), the &#8220;white graphite&#8221;<\/h2>\n<p>Boron nitride is an inorganic solid whose hexagonal (h-BN) and cubic (c-BN) structures are the most stable. Its hexagonal structure is similar to that of graphite, earning it the nickname &#8220;white graphite&#8221;.<\/p>\n<h3>Key properties<\/h3>\n<ul>\n<li>Thermal conductivity: up to 300-400 W\/m\u00b7K in the layer plane<\/li>\n<li>Electrical resistivity: 10\u00b9\u00b3 Ohm.cm (excellent electrical insulator)<\/li>\n<li>Thermal stability: up to 1000 \u00b0C in air, 1950 \u00b0C in inert gas<\/li>\n<li>Non-toxic (advantage in terms of industrial handling)<\/li>\n<\/ul>\n<p><strong>Key result \u2014 BN in epoxy:<\/strong> According to Xiao and Xue Du, the thermal conductivity of an epoxy composite increases from 1.5 W\/m\u00b7K with untreated BN to 2.69 W\/m\u00b7K when BN is treated by admicelle, a treatment promoting the interfacial adhesion of BN to the resin.<\/p>\n<h2>Aluminium nitride (AlN)<\/h2>\n<p>A refractory and semi-conducting material, AlN is both an electrical insulator and has exceptional thermal conductivity, which can reach 1800 W\/m\u00b7K for the purest forms. Its main limitation is its sensitivity to hydrolysis in the presence of water.<\/p>\n<h3>Key result of silane-treated AlN in epoxy<\/h3>\n<ul>\n<li>With 60 vol.% of silane-treated AlN particles, thermal conductivity reaches 11.0 W\/m\u00b7K<\/li>\n<li>An increase of +97% compared to untreated AlN<\/li>\n<li>The improvement is due to the reduction in thermal contact resistance at the interface<\/li>\n<\/ul>\n<h2>Alumina (Al\u2082O\u2083), the general-purpose filler<\/h2>\n<p>Part of the oxide family, alumina is the hardest natural material after diamond (&gt; 18 GPa Vickers). It is particularly used for its wear resistance, biocompatibility and excellent performance-to-cost ratio.<\/p>\n<ul>\n<li>Thermal conductivity: 8-30 W\/m\u00b7K (depending on purity)<\/li>\n<li>Dielectric strength: up to 40 kV\/mm<\/li>\n<li>With 80 vol.%: epoxy composite thermal conductivity reaching 4.5 W\/m\u00b7K<\/li>\n<\/ul>\n<h2>Comparative table of effective conductivities (literature)<\/h2>\n<figure class=\"wp-block-table\">\n<table>\n<thead>\n<tr>\n<th>Configuration<\/th>\n<th>Volume fraction<\/th>\n<th>\u03bb effective (W\/m\u00b7K)<\/th>\n<th>Treatment<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Pure epoxy (reference)<\/td>\n<td>&#8211;<\/td>\n<td>~0.2<\/td>\n<td>&#8211;<\/td>\n<\/tr>\n<tr>\n<td>Epoxy + untreated BN<\/td>\n<td>Variable<\/td>\n<td>1.5<\/td>\n<td>None<\/td>\n<\/tr>\n<tr>\n<td>Epoxy + admicelle BN<\/td>\n<td>Variable<\/td>\n<td>2.69<\/td>\n<td>Admicelle<\/td>\n<\/tr>\n<tr>\n<td>Epoxy + Al\u2082O\u2083<\/td>\n<td>80 vol.%<\/td>\n<td>4.5<\/td>\n<td>&#8211;<\/td>\n<\/tr>\n<tr>\n<td>Epoxy + silane-treated AlN<\/td>\n<td>60 vol.%<\/td>\n<td>11.0<\/td>\n<td>Silane<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p><strong>Note: graphite and graphene.<\/strong> Although graphite and graphene have very high intrinsic thermal conductivities, they are also electrically conductive. Their use is therefore incompatible with dielectric insulation applications.<\/p>\n<p><em>Do you want to select the right ceramic filler for your thermal composite? Contact our technical team at <a href=\"mailto:sales@segdielectriques.com\">sales@segdielectriques.com<\/a> for tailored support.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Boron nitride, aluminium nitride and alumina compared: properties, conductivity values and application limits for high-performance dielectric insulation.<\/p>\n","protected":false},"author":1,"featured_media":926,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"pdf_url":"","secteur":"","cta_label":"","footnotes":""},"categories":[16],"tags":[],"class_list":["post-927","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-article"],"_links":{"self":[{"href":"https:\/\/segdielectriques.com\/en\/wp-json\/wp\/v2\/posts\/927","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/segdielectriques.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/segdielectriques.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/segdielectriques.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/segdielectriques.com\/en\/wp-json\/wp\/v2\/comments?post=927"}],"version-history":[{"count":0,"href":"https:\/\/segdielectriques.com\/en\/wp-json\/wp\/v2\/posts\/927\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/segdielectriques.com\/en\/wp-json\/wp\/v2\/media\/926"}],"wp:attachment":[{"href":"https:\/\/segdielectriques.com\/en\/wp-json\/wp\/v2\/media?parent=927"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/segdielectriques.com\/en\/wp-json\/wp\/v2\/categories?post=927"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/segdielectriques.com\/en\/wp-json\/wp\/v2\/tags?post=927"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}