Work

Multifunctional evaluation of inorganic PCMs with graphite and alumina: Thermophysical and rheological insights

Year: 2026

Type: article

Abstract: Potassium nitrate (KNO₃) is a potential high-temperature phase change material for solar thermal energy storage, but its low thermal conductivity and limited thermophysical performance restrict its practical use. In this study, graphite and aluminium oxide (Al 2 O 3 ) powders were blended with KNO₃ at 5-12.5 wt% to evaluate changes in melting point, latent heat, specific heat capacity, thermal conductivity, chemical stability, and phase behavior. Graphite showed the best overall improvement, increasing latent heat up to 134.5 kJ/kg thermal conductivity up to 1.9 W/m·K at 10 wt%, but maximum specific heat capacity achieved at 7.5 wt%. However, increasing graphite concentration caused agglomeration and reduced efficiency. Al 2 O 3 also improved performance, with 7.5 wt% increasing latent heat by 21.9% and specific heat capacity to 2.4 kJ/kg·K, while excessive addition led to clustering and degradation. The negative effect of microparticle addition on flowability helped in identifying the optimum composition, even though the additives improved the thermal properties. For graphite-based nitrate salts, the 10 wt% sample showed the highest latent heat (+31.9%) and thermal conductivity (+211.5%), but its flowability decreased because of the increased viscosity (4.15 mPa·s). In contrast, the 7.5 wt% graphite sample retained most of the thermal benefits (89% latent heat and 97% thermal conductivity gain), while also showing the highest specific heat capacity and a lower viscosity (2.10 mPa·s). The Al₂O₃ based samples showed a similar trend at higher blending ratios, therefore 7.5 wt% concentration for both graphite and Al₂O₃ was identified as the most balanced composition, offering the best thermal improvement.

Source: Results in Engineering

DOI: 10.1016/j.rineng.2026.112730

Authors: Atif Shazad, Muhammad Uzair, Ahmad Hussain, Abdul Shakoor, Abdullah Yassin

Institutions: Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, NED University of Engineering and Technology, University of Engineering and Technology Peshawar, Universiti Malaysia Sarawak

Language: English

Topic: Phase Change Materials Research

Subfield: Mechanical Engineering

Field: Engineering

Domain: Physical Sciences

SDG: Affordable and clean energy

Open Access status: gold

Estimated APC paid: $1,940