Study Of Wood Pore Size Distribution Based On Time-Domain Nuclear Magnetic Resonance

The wood pore size is multi-scale distribution of micro to nanoscale, according to the principle of time-domain NMR T2 distribution characterization the pore size distribution of porous materials to divided the wood porous into mesoporous(1-100nm) and large pore (>100nm). Respectively using two standard samples to calculate the conversion factor C between T2 poreand wood pore diameter to characterize the wood pore size distribution because of the pore surface of the void ratio and different forms in mesoporous and large pore.The research results of this paper wear summarized as follows:1.72 distribution characterization of P. platyphylla sapwood and heartwood pore size distribution in the process of high temperature drying, when they were green wood, the pore size distribution in mesoporous of sapwood was 0.016-0.105μm, and the pore size distribution in mesoporous of heartwood was 0.016-0.037μm Mesoporous of heartwood and sapwood were both shrink in drying process. There were still a small amount of bound water in the cell walls when the wood oven dry and measured residual bound water in the sapwood pore diameter distribution was 0.001-0.013μ.m, in the heartwood pore diameter distribution was 0.001-0.022μm。2. After 2 hours in the condition of high temperature drying, average pore size of wood fiber in P. platyphylla sapwood and heartwood was diminished, the range of pore size distribution was diminished. Shrink of cell wall led to the wood fiber pore contraction and reduce big pores size of wood fiber, small pore size of wood fiber wad increased. For the vessel pore diameter was so big to get a long T2 weight(close to the water body relaxation time 2-3 s), it could not neglect water body relaxation effect in big pore.3. When P. platyphylla sapwood and heartwood were green wood, the vessel pore diameter of sapwood was 52.139-275.920μm and the vessel pore diameter of heartwood was 26.041-169.718μm, the vessel pore diameter of heartwood was less than sapwood.4. Pore size distribution in mesoporous of heartwood was 0.005-0.056μm when the Red Oak was green wood. At the beginning of the 40℃ drying, pore size distribution in mesoporous of heartwood was 0.002-0.043μm, mesoporous changed little. Red oak mesoporous still was detected residual water when it was oven dry. Pore size distribution in mesoporous of Red Oak heartwood was 0.001-0.006μm.5. The change of T2 distribution also could characterize pore size of wood fiber of red oak heartwood aperture changes, drying 2h later, pore size distribution changed little with it wad green wood. For the vessel of big pore, water was expelled so that could not get the pore size change in the process of drying.6. The little vessel pore size distribution was 22.665-62.450μm and big vessel pore size distribution was 90.863-194.910μm when the Red oak heartwood. The vessel pore size distribution was 26.041-169.718μm when P. platyphylla heartwood were green wood, contrasting them to observed that Red oak heartwood pore size distribution was greater than P. platyphylla heartwood and pore size of little vessel and big vessel had significant difference.