Objective In order to solve the problems of liquid leakage and poor thermal conductivity faced by wood-based phase change energy storage materials, we heat-treated myristic acid impregnated wood using Sn-Bi alloy, and introduced it into the wood under the drive of heat.

Method Taking poplar wood impregnated with myristic acid as matrix, Sn-Bi alloy was combined with the matrix by alternating high and low temperature heat treatments to prepare energy storage wood with metal shells. Scanning electron microscope, Shore hardness tester, universal mechanics tester, thermal conductivity meter and differential scanning calorimeter were used to test the micro-morphology, surface hardness, compressive strength parallel to grain and thermal properties of the energy storage wood.

Result The mass gain of samples during heat treatment at 160−220 ℃ for 1−5 min was significant. The mechanical and thermal properties of samples were improved with the increase of heat treatment temperature and time. Compared with untreated wood, the compressive strength parallel to grain and surface hardness were increased by 120.02%−149.59% and 13.53%−46.93%, respectively, and the axial and radial thermal conductivity were increased by 34.18%−165.67% and 38.11%−80.70%, respectively. The Sn-Bi alloy was filled best when heat-treated at 190 ℃ for 5 min, with surface hardness, axial and radial thermal conductivity reaching the highest values of 62.65 HD, 0.5324 and 0.2987 W/(m·K). Retention of myristic acid within the wood ranged from 27.54% to 63.68%, and the highest energy storage density of 59.38 J/cm³ was achieved after heat treating at 160 ℃ for 3 min.

Conclusion Alternating high and low temperature heat treatment prompts the Sn-Bi alloy entering into the vessel of the wood, achieving different degrees of penetration. Three dimensional pore structures of wood and Sn-Bi alloy filled outside solves the problems of liquid leakage and poor thermal conductivity of phase change materials. The prepared energy storage wood combines the advantages of wood, metal and phase change materials, with better surface hardness, compressive strength parallel to grain and thermal properties, making it prospective for applications in building walls and energy-storage floors.