{"id":90530,"date":"2025-07-24T07:06:44","date_gmt":"2025-07-24T05:06:44","guid":{"rendered":"https:\/\/www.linseis.com\/unkategorisiert\/heat-accumulators-in-the-high-temperature-range-materials-with-constant-capacity-over-many-cycles\/"},"modified":"2025-07-24T15:04:12","modified_gmt":"2025-07-24T13:04:12","slug":"heat-accumulators-in-the-high-temperature-range-materials-with-constant-capacity-over-many-cycles","status":"publish","type":"post","link":"https:\/\/www.linseis.com\/en\/wiki\/heat-accumulators-in-the-high-temperature-range-materials-with-constant-capacity-over-many-cycles\/","title":{"rendered":"Heat accumulators in the high-temperature range: materials with constant capacity over many cycles"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"90530\" class=\"elementor elementor-90530 elementor-90466\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-d57f291 e-flex e-con-boxed e-con e-parent\" data-id=\"d57f291\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-b851da7 elementor-toc--minimized-on-tablet elementor-widget elementor-widget-table-of-contents\" data-id=\"b851da7\" data-element_type=\"widget\" data-e-type=\"widget\" data-settings=\"{&quot;headings_by_tags&quot;:[&quot;h2&quot;],&quot;exclude_headings_by_selector&quot;:[],&quot;no_headings_message&quot;:&quot;No headings were found on this page.&quot;,&quot;marker_view&quot;:&quot;numbers&quot;,&quot;minimize_box&quot;:&quot;yes&quot;,&quot;minimized_on&quot;:&quot;tablet&quot;,&quot;hierarchical_view&quot;:&quot;yes&quot;,&quot;min_height&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_tablet&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_mobile&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]}}\" data-widget_type=\"table-of-contents.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<div class=\"elementor-toc__header\">\n\t\t\t\t\t\t<h4 class=\"elementor-toc__header-title\">\n\t\t\t\tTable of Contents\t\t\t<\/h4>\n\t\t\t\t\t\t\t\t\t\t<div class=\"elementor-toc__toggle-button elementor-toc__toggle-button--expand\" role=\"button\" tabindex=\"0\" aria-controls=\"elementor-toc__b851da7\" aria-expanded=\"true\" aria-label=\"Open table 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9.317-33.901-.04l-22.667-22.667c-9.373-9.373-9.373-24.569 0-33.941L207.03 130.525c9.372-9.373 24.568-9.373 33.941-.001z\"><\/path><\/svg><\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<div id=\"elementor-toc__b851da7\" class=\"elementor-toc__body\">\n\t\t\t<div class=\"elementor-toc__spinner-container\">\n\t\t\t\t<svg class=\"elementor-toc__spinner eicon-animation-spin e-font-icon-svg e-eicon-loading\" aria-hidden=\"true\" viewBox=\"0 0 1000 1000\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M500 975V858C696 858 858 696 858 500S696 142 500 142 142 304 142 500H25C25 237 238 25 500 25S975 237 975 500 763 975 500 975Z\"><\/path><\/svg>\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-1919de7 elementor-widget elementor-widget-heading\" data-id=\"1919de7\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Heat storage for high-temperature processes<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-b225df0 elementor-widget elementor-widget-text-editor\" data-id=\"b225df0\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>In the course of industrial decarbonization, the efficient use of thermal energy is increasingly becoming the focus of energy technology. Particularly in the area of <b>concentrating solar power plants (CSP)<\/b> and in the <b>metalworking industry<\/b>, there is a considerable need to store <b>high temperatures (&gt;600 \u00b0C)<\/b> for hours or days &#8211; both to smooth out fluctuating energy sources and to recover industrial waste heat. In metal processing, for example, the waste heat generated during heat treatment can be temporarily stored in storage materials and later reused to <b>preheat materials<\/b> or in drying processes.  <\/p><p>Heat accumulators are used for this purpose, which absorb thermal energy either sensitively (via temperature increase), latently (via phase change) or chemically (via reversible reactions). <b>High-temperature applications<\/b> are particularly demanding, as they require storage materials that remain <b>mechanically, thermally and chemically stable<\/b> &#8211;<strong> over<\/strong> <b>several hundred charging and discharging cycles<\/b>. The main challenge is to identify materials whose heat storage capacity remains constant over many cycles.  <\/p><p>Particular attention is paid to <b>solids<\/b> such as <b>graphite, ceramic insulators<\/b> or <b>composite systems<\/b> consisting of these components. Such materials offer a wide range of applications as heat carriers, structural materials or matrices for other functional phases (e.g. salts, oxides). However, their performance cannot be assessed by chemical composition or melting points alone &#8211; the <b>long-term behavior under cyclic thermal stress<\/b> is decisive.  <\/p><p>For the systematic evaluation of these properties, material characterization uses <a href=\"https:\/\/www.linseis.com\/en\/methods\/differential-scanning-calorimetry\/\" data-auto-event-observed=\"true\"><strong>Differential Scanning Calorimetry (DSC)<\/strong><\/a> is used in material characterization. As a thermal analysis method, it enables the exact determination of heat capacity, transition temperatures and enthalpy changes over repeated temperature cycles. DSC is therefore an indispensable tool for analyzing material systems with regard to their <b>cycle strength and thermal stability<\/b> in the high-temperature range.  <\/p><p>Recent studies show that targeted material combinations &#8211; such as ceramic-graphitic composites &#8211; can be used to develop systems that exhibit <b>constant thermal performance<\/b> despite high loads over hundreds of cycles (Yang et al., 2025; Ran et al., 2020). This article highlights the requirements for such heat storage materials, presents relevant material systems and shows how DSC contributes to the evaluation of their suitability for use. <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-089db90 elementor-widget elementor-widget-heading\" data-id=\"089db90\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Requirements for high-temperature heat accumulators<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-ffd63eb elementor-widget elementor-widget-text-editor\" data-id=\"ffd63eb\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>High-temperature heat accumulators must meet complex requirements in order to be used reliably on an industrial scale. Unlike storage tanks for low or medium temperatures, such as those used in building services, the main requirements here are <b>thermal load capacity, chemical resistance and mechanical integrity over many cycles<\/b>. The choice of material is significantly influenced by these multi-criteria decisions.  <\/p><h4>Thermal requirements<\/h4><p>The ability to efficiently absorb and release thermal energy is key. In the case of <b>sensible heat storage<\/b>, this is achieved by increasing the temperature of a material, with the <b>specific heat capacity (c\u209a)<\/b> determining the amount of energy stored. For high-temperature applications, materials are required whose c\u209a values remain as constant as possible over the entire temperature range. A high absolute heat capacity is desirable, but it is more important that it <b>does not drop over many charging cycles<\/b> &#8211; an aspect that can only be clearly assessed through repeated measurements.   <\/p><p><b>Thermal conductivity<\/b> also plays a decisive role: materials with low conductivity cannot distribute heat evenly throughout the volume, which leads to unwanted temperature gradients and material stresses. The integration of highly conductive components &#8211; such as graphite &#8211; can make a targeted contribution to homogenizing the temperature distribution.<\/p><h4>Chemical and mechanical stability<\/h4><p>Thermal accumulators in industrial high-temperature applications are often exposed not only to heat, but also to <b>reactive atmospheres<\/b>, pressure differences or material contact with metallic, oxidizing or corrosive media. <b>Resistance to chemical reactions<\/b> is therefore a basic requirement. Oxidation, hydrolysis or the formation of unstable intermediate phases can lead to the gradual degradation of the storage capacity.  <\/p><p>One example: graphite oxidizes in an oxygen atmosphere from around 600 \u00b0C &#8211; which limits its use in many applications without protective measures. Ceramics, on the other hand, especially those based on <b>SiC <\/b>or <b>Si\u2083N\u2084,<\/b> develop protective <b>SiO\u2082 layers<\/b> at high temperatures, which act as a <b>diffusion barrier<\/b> and prevent the penetration of oxygen. <\/p><p><b>Mechanical stability<\/b> is also crucial. Repeated heating and cooling processes lead to <b>thermal expansion and contraction<\/b>, which generate stresses in the material. Materials with low thermal expansion and high fracture toughness have an advantage here. Ceramics offer excellent dimensional stability, while flexible, porous structures such as expanded graphite can partially absorb material stresses.   <\/p><h4>Evaluation by differential scanning calorimetry (DSC)<\/h4><p>The above-mentioned requirements cannot be recorded using material data sheets alone. Only <b>cyclical thermal analyses<\/b> &#8211; such as those carried out with DSC &#8211; reveal how c\u209a, enthalpy or phase transitions change in real operation. Several heating\/cooling cycles are specifically simulated in DSC measurements. Deviations in the resulting calorimetry curves indicate a <b>drop in performance or structural changes<\/b> at an early stage.   <\/p><p>DSC is one of the few methods that can simultaneously record these multi-physical changes, particularly in the case of new material combinations such as composite systems made of ceramics, graphite and salts. Studies such as that of   <strong>Yang et al. (2025)<\/strong>  or  <strong>Ran et al. (2020)<\/strong>  show that DSC can be used to make reliable statements about the thermal reversibility and stability of material systems &#8211; an essential prerequisite for the development of durable heat storage systems.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-f78cc05 elementor-widget elementor-widget-heading\" data-id=\"f78cc05\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Graphite as heat storage and matrix material<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-e902ec9 elementor-widget__width-initial elementor-widget elementor-widget-image\" data-id=\"e902ec9\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" width=\"800\" height=\"534\" src=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/ENG_Isometrische-Darstellung-eines-keramisch-graphitischen-Kompositmaterials-1024x683.png\" class=\"attachment-large size-large wp-image-90540\" alt=\"\" srcset=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/ENG_Isometrische-Darstellung-eines-keramisch-graphitischen-Kompositmaterials-1024x683.png 1024w, https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/ENG_Isometrische-Darstellung-eines-keramisch-graphitischen-Kompositmaterials-300x200.png 300w, https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/ENG_Isometrische-Darstellung-eines-keramisch-graphitischen-Kompositmaterials-768x512.png 768w, https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/ENG_Isometrische-Darstellung-eines-keramisch-graphitischen-Kompositmaterials.png 1200w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Figure 1: Schematic representation of a ceramic-graphitic composite with porous graphite (gray), PCM inclusions (blue) and ceramic protective coating (white) for high-temperature heat storage.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-26582d2 elementor-widget elementor-widget-text-editor\" data-id=\"26582d2\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p><b>Graphite <\/b>is one of the most studied materials for heat storage in the high temperature range &#8211; not only because of its thermal properties, but also because of its structural flexibility. In porous or expanded form, graphite can serve as a <b>matrix material <\/b>for other storage substances such as salts or metal oxides, while at the same time contributing to <b>heat distribution <\/b>and <b>structural stability <\/b>. <\/p><h4>Thermal conductivity and temperature behavior<\/h4><p>A key feature of graphite is its <b>pronounced anisotropic thermal conductivity<\/b>, which is significantly higher in the basal plane (parallel to the layer plane) than perpendicular to it. This enables effective <b>lateral heat distribution<\/b>, which is particularly advantageous in modular or layered storage systems. The specific heat capacity of graphite is moderate compared to other solids, but increases continuously with increasing temperature &#8211; a property that can be used for sensitive heat storage.  <\/p><p>In operation, it has been shown that graphite remains <b>thermally stable<\/b> in an inert gas environment over many temperature cycles. Studies such as those by   <strong>Yang et al. (2025)<\/strong>  show that ceramically stabilized graphite composites maintain their storage capacity almost constantly over <b>several hundred thermal cycles<\/b>. The combination with ceramic materials protects the graphite against structural degradation and also has a temperature-stabilizing effect. <\/p><h4>Susceptibility to oxidation and protective measures<\/h4><p>In oxidizing atmospheres &#8211; especially in the presence of atmospheric oxygen &#8211; graphite begins to oxidize at temperatures of around <strong>600<\/strong><strong>\u00b0C<\/strong>. This severely limits its use in open systems. This severely restricts its use in open systems. In order to extend the application temperature ranges, <strong>passivating protective measures<\/strong> are often taken, for example:  <\/p><ul><li>Operation in <b>an inert gas atmosphere <\/b>(argon, nitrogen)<\/li><li>Embedding in <b>ceramic cladding structures<\/b> (e.g. Al\u2082O\u2083, SiC)<\/li><li>Use of <b>coating systems<\/b> with diffusion-inhibiting properties<\/li><\/ul><p>A practical example is the work of  <strong>Ran et al. (2020)<\/strong>in which <strong>expanded graphite<\/strong> was combined with eutectic salts and ceramic additives. The composites not only showed improved thermal conductivity compared to the pure salt systems, but also significantly increased <strong>cycle stability<\/strong>. The role of the graphite here was both to absorb the salt and to improve the heat distribution in the volume. Thermal analysis using DSC showed that the stored enthalpy remained largely constant over dozens of cycles.   <\/p><h4>Application scenarios and material integration<\/h4><p>In addition to its role as an active storage material, graphite can also serve as a <b>structural carrier <\/b>in more complex material composites. Particularly in module-based high-temperature storage systems, such as those used in CSP plants or industrial process heat systems, graphite can be used to create thermally conductive paths within an otherwise insulating system. <\/p><p>The integration of porous graphite structures also allows <b>impregnation with PCM components<\/b> or coupling with metallic storage media. Graphite acts as a shaping medium that combines thermal and mechanical functionality in one component. <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-1125964 elementor-widget elementor-widget-heading\" data-id=\"1125964\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Ceramic insulators: structure, protection and stability in high-temperature storage<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-89f66d3 elementor-widget__width-initial elementor-widget elementor-widget-image\" data-id=\"89f66d3\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"800\" height=\"534\" src=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/Mikrostrukturvergleich_Graphit_Keramik-1-1024x683.png\" class=\"attachment-large size-large wp-image-90481\" alt=\"\" srcset=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/Mikrostrukturvergleich_Graphit_Keramik-1-1024x683.png 1024w, https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/Mikrostrukturvergleich_Graphit_Keramik-1-300x200.png 300w, https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/Mikrostrukturvergleich_Graphit_Keramik-1-768x512.png 768w, https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/Mikrostrukturvergleich_Graphit_Keramik-1.png 1536w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Figure 2: Microstructure comparison of expanded graphite (left, layered-porous) and aluminum oxide (right, compact-granular). Differences in porosity and structure determine thermal conductivity and chemical stability. <\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-6a0e05a elementor-widget elementor-widget-text-editor\" data-id=\"6a0e05a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p><b>Ceramic materials <\/b>play a strategically important role in the context of thermal energy storage in the high-temperature range &#8211; not primarily as energy storage, but as <b>structural, thermal and chemical stabilization components<\/b>. They are used in the form of matrices, layers or functional embeddings and make a decisive contribution to the durability and safety of heat storage systems. <\/p><h4>Thermal properties and application limits<\/h4><p>Typical high-performance ceramics such as <b>aluminium oxide (Al\u2082O\u2083)<\/b>, <b>zirconium oxide (ZrO\u2082)<\/b> or <b>silicon carbide (SiC)<\/b> are characterized by their <b>extreme temperature resistance<\/b> (&gt;1500 \u00b0C), <b>low thermal conductivity<\/b> (typically &lt;10 W\/m-K) and very low thermal expansion. These properties make them ideal as <b>thermal insulators<\/b> in modular storage units, particularly for separating heat-conducting and heat-storing areas or for <b>shielding sensitive materials<\/b>. <\/p><p>The low thermal conductivity counteracts unwanted heat dissipation to the environment, while the high dimensional stability ensures mechanical integrity over many cycles. Under repeated thermal stress &#8211; as is typical in the charging\/discharging operation of high-temperature storage tanks &#8211; these materials show <b>no relevant structural changes<\/b>. <\/p><h4>Chemical stability: passivation and diffusion barrier<\/h4><p>Another advantage of ceramic insulators is their <b>chemical inertness <\/b>to oxidizing, corrosive or reactive media. This is particularly relevant when used in combination with materials such as graphite, which oxidizes on contact with oxygen above 600 \u00b0C. Under such conditions, ceramics such as <b>SiC <\/b>or <b>Si\u2083N\u2084<\/b> form <strong>passivating <\/strong><b>silicon oxide layers (SiO\u2082)<\/b> on their surface. These act as a <b>diffusion barrier against oxygen<\/b>, which can also protect adjacent materials from oxidation.   <\/p><p>In composite systems, such ceramics therefore take on a <b>dual function<\/b>: on the one hand, they act as a mechanical support structure and, on the other, as a <b>chemically inert shell<\/b> that shields graphite cores or PCM components from environmental influences, for example. This creates a controlled microenvironment that significantly extends the service life of the entire system. <\/p><h4>Structural function in composite materials<\/h4><p>Ceramics can be structured in a targeted manner &#8211; for example in the form of porous carrier materials, plates, honeycombs or bulk solids &#8211; and thus enable a precise design of the <b>heat flow<\/b> in the storage tank. In conjunction with thermally conductive components such as graphite, <b>hybrid systems<\/b> are created in which the advantages of both materials are functionally combined: <b>mechanical resistance<\/b> and <b>chemical stability<\/b> on the part of the ceramic, <b>heat distribution and energy storage<\/b> on the part of the graphite. <\/p><p>A successful example is provided by the work of  <strong>Ran et al. (2020)<\/strong>in which ceramic components were embedded in a salt-graphite system. The ceramic matrix ensured an even distribution of the storage material, reduced thermomechanical stresses and at the same time improved the oxidation resistance of the entire composite body. The long-term stability was confirmed by DSC measurements over many temperature cycles.  <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-063d490 elementor-widget elementor-widget-shortcode\" data-id=\"063d490\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"shortcode.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-shortcode\">\n<table id=\"tablepress-226\" class=\"tablepress tablepress-id-226\" aria-describedby=\"tablepress-226-description\">\n<thead>\n<tr class=\"row-1\">\n\t<th class=\"column-1\"><strong><hr3>Material<\/hr3><\/strong><\/th><th class=\"column-2\"><strong><hr3>Specific Heat c\u209a (J\/g\u00b7K)<\/hr3><\/strong><\/th><th class=\"column-3\"><strong><hr3>Thermal Conductivity (W\/m\u00b7K)<\/hr3><\/strong><\/th><th class=\"column-4\"><strong><hr3>Cycle Stability<\/hr3><\/strong><\/th><th class=\"column-5\"><strong><hr3>Chemical Stability<\/hr3><\/strong><\/th>\n<\/tr>\n<\/thead>\n<tbody class=\"row-striping row-hover\">\n<tr class=\"row-2\">\n\t<td class=\"column-1\">Graphite<\/td><td class=\"column-2\">0.7\u20131.0<\/td><td class=\"column-3\">>100<\/td><td class=\"column-4\">High<\/td><td class=\"column-5\">Low (oxidation-prone)<\/td>\n<\/tr>\n<tr class=\"row-3\">\n\t<td class=\"column-1\">Aluminum oxide (Al\u2082O\u2083)<\/td><td class=\"column-2\">0.8\u20131.1<\/td><td class=\"column-3\"><10<\/td><td class=\"column-4\">High<\/td><td class=\"column-5\">High<\/td>\n<\/tr>\n<tr class=\"row-4\">\n\t<td class=\"column-1\">Ceramic\u2013graphite composite<\/td><td class=\"column-2\">variable<\/td><td class=\"column-3\">medium to high<\/td><td class=\"column-4\">High<\/td><td class=\"column-5\">adaptable (via composition)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<span id=\"tablepress-226-description\" class=\"tablepress-table-description tablepress-table-description-id-226\"><em>Comparison of thermal and structural properties of typical high-temperature materials (data ranges are indicative, based on references from Ran et al., 2021 and Yang et al., 2025)<\/em><\/span>\n<!-- #tablepress-226 from cache --><\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-28ef146 elementor-widget elementor-widget-heading\" data-id=\"28ef146\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Differential scanning calorimetry (DSC): the key to evaluating cycle stability<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-e2b8233 elementor-widget elementor-widget-text-editor\" data-id=\"e2b8233\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>The development of cycle-stable heat storage materials for the high-temperature range depends on reliable analysis methods that precisely quantify thermal properties. <strong>Differential scanning calorimetry (DSC)<\/strong> has established itself as one of the central test methods in this respect. It makes it possible to determine <strong>phase transitions<\/strong>, <strong>enthalpy changes<\/strong> and the <strong>specific heat capacity (c<\/strong><strong>\u209a)<\/strong> of materials as a function of temperature and over repeated load cycles.  <\/p><p> <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-08e8a60 elementor-widget elementor-widget-heading\" data-id=\"08e8a60\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Principle of the DSC<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-64a2ed8 elementor-widget__width-initial elementor-widget elementor-widget-image\" data-id=\"64a2ed8\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"800\" height=\"534\" src=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/Prinzip-der-Differential-Scanning-Calorimetry-DSC-1-1024x683.png\" class=\"attachment-large size-large wp-image-90518\" alt=\"\" srcset=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/Prinzip-der-Differential-Scanning-Calorimetry-DSC-1-1024x683.png 1024w, https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/Prinzip-der-Differential-Scanning-Calorimetry-DSC-1-300x200.png 300w, https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/Prinzip-der-Differential-Scanning-Calorimetry-DSC-1-768x512.png 768w, https:\/\/www.linseis.com\/wp-content\/uploads\/2025\/07\/Prinzip-der-Differential-Scanning-Calorimetry-DSC-1.png 1536w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Figure 3: Principle of differential scanning calorimetry (DSC) - heat flow curve with endothermic and exothermic transitions.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-fcdc31c elementor-widget elementor-widget-text-editor\" data-id=\"fcdc31c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>DSC measures the difference in heat flows between a sample and a reference while both are heated or cooled to a defined temperature in a controlled manner. Changes in the heat flow indicate physical or chemical transitions in the sample, for example: <\/p><ul><li>Endothermic processes: e.g. melting, phase change<\/li><li>Exothermic processes: e.g. crystallization, reactions<\/li><li>Temperature-dependent c\u209a changes<\/li><\/ul><p><br><b>How these thermal properties change over many cycles<\/b> is particularly interesting for the evaluation of high-temperature heat accumulators. This is precisely where the strength of DSC lies: by repeating heating\/cooling cycles, it is possible to determine whether and how quickly a material loses performance &#8211; for example due to structural changes, oxidation or phase separation. <\/p><h4>Application on high-temperature materials<\/h4><p>For materials such as <b>graphite, ceramic-graphite composites<\/b> or PCM-containing composites, DSC can be used to analyze key parameters such as heat capacity and transition temperatures not only in the fresh state, but also <b>after many thermal cycles<\/b>. For example, it is possible to see whether the stored enthalpy decreases over time or whether the temperature range in which a phase transition occurs shifts. <\/p><p>In the work of  <strong>Yang et al. (2025)<\/strong>  ceramic stabilized graphite composites were tested in several heating\/cooling cycles. The DSC results showed stable thermal performance over <b>several hundred cycles<\/b>, with no significant drift in heat capacity or melting behavior. Such results not only prove the suitability of the material, but also the validity of DSC as a test method.  <\/p><p>A similar approach can be found in  <strong>Ran et al. (2020)<\/strong>which analyzed a eutectic salt-graphite-ceramic matrix. Here too, DSC was used to test the <b>reversibility of the thermal transitions<\/b> over repeated temperature stress &#8211; with positive results in terms of cycle strength. <\/p><h4>Significance and limits<\/h4><p>The advantages of DSC in material screening lie in:<\/p><ul><li><b>High sensitivity<\/b> to small thermal effects<\/li><li><b>Cycle-capable test protocols<\/b> for simulating real storage loads<\/li><li><b>Quantitative determination<\/b> of heat capacity and enthalpy<\/li><li><b>Wide temperature applicability<\/b> (up to &gt;1500 \u00b0C depending on the device)<\/li><\/ul><p><br>At the same time, there are limitations: Measurement inaccuracies can occur at extremely high temperatures or with very large samples, as well as with highly anisotropic materials with high thermal conductivity. In such cases, a combination with other methods &#8211; such as thermogravimetry (TG) or dilatometric measurements &#8211; makes sense. <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-4e89fc9 elementor-widget elementor-widget-heading\" data-id=\"4e89fc9\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Conclusion and outlook: Systematically evaluating heat storage<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-0a4ef7b elementor-widget elementor-widget-text-editor\" data-id=\"0a4ef7b\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>Targeted heat storage in the high-temperature range is a key issue for industrial processes and renewable energy systems. In applications such as <b>concentrating solar power (CSP)<\/b> or the <b>metalworking industry<\/b>, highly efficient storage solutions can help to <b>reduce energy losses, cushion peak loads and provide process heat in line with demand<\/b>. <\/p><p>The analysis shows: Neither graphite nor ceramic materials meet all requirements in isolation. However, their combination in <b>composite materials <\/b>allows thermal conductivity, storage capacity and chemical stability to be combined in a targeted manner. <b>Ceramics <\/b>offer structural strength and chemical protection, while <b>graphite <\/b>efficiently distributes and stores heat as a matrix or additive. <\/p><p><b>Cycle stability<\/b> is central to material selection: a heat accumulator is only suitable for practical use if it delivers <b>constant performance<\/b> over many charging and discharging processes. <b>Differential scanning calorimetry (DSC)<\/b> makes a decisive contribution here: it makes performance drops visible at an early stage, quantifies relevant characteristic values such as heat capacity and enthalpy, and allows the direct comparison of different material systems under realistic conditions. <\/p><p>The works cited by  <strong>Yang et al. (2025)<\/strong>  and  <strong>Ran et al. (2020)<\/strong>  show how <b>highly stable storage materials can be developed<\/b> through targeted material combinations and precise analysis. These findings are increasingly being incorporated into material development for industrial storage solutions. <\/p><h4>Perspectives<\/h4><p>Future developments will focus on the following aspects:<\/p><ul><li><b>Scalability<\/b> and production of cost-optimized composite materials<\/li><li><b>Standardized test methods<\/b> for comparable evaluation of cycle stability<\/li><li><b>Long-term tests under real operating conditions<\/b><\/li><li><b>Combination of DSC with other analysis methods<\/b> (e.g. TG, X-ray diffractometry)<\/li><\/ul><p><br>With a view to industrial implementation, it is clear that materials science can make a significant contribution to increasing the efficiency, durability and operational reliability of thermal storage systems with systematic analysis such as DSC. This makes it an integral part of sustainable energy systems &#8211; from laboratory scale to industrial scale. <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-45809a2 elementor-widget elementor-widget-text-editor\" data-id=\"45809a2\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p><strong>References<\/strong><\/p><ul><li>Yang, X. et al. (2025): <em>Self-heating ceramic-graphite composites with stable thermal energy storage capacity<\/em>, ACS Energy Letters, 10(3), 1234-1242. DOI: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/acsenergylett.4c03270\" target=\"_blank\" rel=\"noopener\">10.1021\/acsenergylett.4c03270<\/a>  <\/li><\/ul><ul><li>Ran, X., Wang, H., Zhong, Y., Zhang, F., Lin, J., Zou, H., Dai, Z., &amp; An, B. (2021). Thermal properties of eutectic salts\/ceramics\/expanded graphite composite phase change materials for high-temperature thermal energy storage. Solar Energy Materials and Solar Cells, 231, 111047. DOI: <a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0927024821000908?via%3Dihub\" target=\"_blank\" rel=\"noopener\">1016\/j.solmat.2021.111047<\/a>   <\/li><\/ul><p> <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>In the course of industrial decarbonization, the efficient use of thermal energy is increasingly becoming the focus of energy technology.<\/p>\n","protected":false},"author":3,"featured_media":90470,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[106],"tags":[],"class_list":["post-90530","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-wiki"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/posts\/90530","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/comments?post=90530"}],"version-history":[{"count":0,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/posts\/90530\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/media\/90470"}],"wp:attachment":[{"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/media?parent=90530"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/categories?post=90530"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/tags?post=90530"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}