Visualisation of Metals in Pine Treated with Preservative Containing Copper and Iron Nanoparticles

Abstract

In this study we compared the ability of conventional and field-emission scanning-electron-microscopy (FESEM) and energy-dispersive analysis of X-rays (EDX) to visualise and map inorganic nano and microparticles in Southern pine (Pinus sp.) treated with an aqueous dispersion of micronised copper-carbonate and iron oxide. Conventional SEM-EDX was able to detect areas of the wood microstructure that contained higher concentrations of copper and iron, but EDX maps were affected by drift and specimens suffered beam damage. The high brightness of the FESEM's electron beam at low accelerating voltages reduced beam damage and helped when mapping the distribution of copper and iron particles. The clarity of EDX maps was further improved by using drift-correction software and by mapping low energy X-rays. FESEM-EDX was able to resolve individual copper and iron microparticles. We conclude that FESEM-EDX shows promise as a means of resolving and mapping the distribution of inorganic metal particles in wood and that this may lead to greater use of the technology as interest in the treatment of wood with inorganic nano and microparticles grows.