Objective  To achieve the value-added utilization of wood after high energy density microwave treatment, crack-filled type microwave puffed wood based metal composites (WMC) was prepared, which provided a reference for the efficient utilization of planted solid wood treated by microwave.

  Method  Tin-bismuth low melting point alloy (LMA) was used to impregnate microwave puffed Pinus radiata wood to prepare WMC by vacuum impregnation method. The micro-morphology, thermal stability, surface contact angle and other properties of WMC were characterized and analyzed by SEM, EDS, CT, DMA, TG, DSC, XRD, FTIR, etc. Meanwhile, the compound mechanism of LMA and microwave puffed wood was discussed.

  Result  LMA was filled in the cracks of the microwave puffed wood and formed a mechanical interlocking meshing structure with wood, making it tightly combined at the cracks and improving the interface bonding strength. The mass percentages of Sn and Bi in WMC were 25.97% and 31.13%, respectively. The CT scan image reconstructed the spatial distribution of LMA in WMC, realized three-dimensional rendering of WMC visualization, and showed its unique texture. Compared with the untreated wood sample, WMC had higher storage modulus, loss modulus and char yield, and the thermal stability was improved. In addition, there were no new functional group characteristic peaks such as esters and ethers in WMC. The crystal structure of WMC was not destroyed, and the crystallinity of WMC showed an upward trend, increasing from 25.9% of the untreated wood sample to 38.6%. The surface contact angle was 172% higher than that of the untreated wood sample at 60 s, and the hydrophobicity was significantly improved.

  Conclusion  In this study, a crack-filled microwave puffed wood based metal composites was prepared, the distribution of tin-bismuth alloy in microwave puffed wood was observed and modeled, and thermal stability and surface contact angle were characterized, which provided a new idea for the development of new wood products based on high energy density microwave treatment of wood.