Surface preparation of wooden samples for scanning electron microscopy

Izbrali smo nekaj tipičnih predstavnikov iglavcev in difuzno ter venčasto poroznih listavcev. Preizkusili smo različne metode predpriprave in rezanja površin lesa ter ugotovili optimalno tehniko priprave vzorcev lesa za opazovanje z vrstičnim elektronskim mikroskopom (SEM). Vzorci so bili pred rezanjem ali suhi, namočeni v vodo in zamrznjeni, prepojeni s parafinom ali pa zgolj z navlaženo površino. Analizirali smo površine lesa, pridobljene s cepljenjem, žaganjem, skobljanjem in brušenjem ter odrezovanjem na drsnem mikrotomu s klasičnim ali zamenljivim nožem. Najboljše rezultate smo dobili pri odrezovanju predhodno navlažene površine lesa na drsnem mikrotomu z zamenljivim nožem ter površino dodatno naprašeno z zlatom. Optimalna metoda priprave v okviru preverjenih metodologij tehnično ni zahtevna, časovno ni zamudna, dobljeni rezultati pa v celoti zadoščajo preučevanju anatomije lesa. Primerjava svetlobne in SEM mikroskopije je pokazala dobro primerljivost tehnik pri manjših povečavah in bistveno prednost SEM pri večjih povečavah. S SEM smo dosegli dobre rezultate pri povečavah do 8000-krat. Uporaba SEM mikroskopa odpira nove razsežnosti preiskovanja zgradbe in lastnosti lesa. V okviru naloge smo pripravili navodila za optimalno pripravo vzorcev in podali teoretično in praktično podlago za nadaljnje preiskave anatomije lesa z uporabo SEM na Oddelku za lesarstvo.Some typical softwoods as well as ring and diffuse porous hardwood species were chosen. We tested various methods for the preparation and cutting of wood surfaces and we determined an optimal technique for preparing wood samples for observation on a Scanning Electron Microscope (SEM). The samples had been either dried, soaked in water and frozen, impregnated with paraffin, or simply with a moistened surface before they were cut. We analysed wood surfaces obtained by splitting, sawing, planning, grinding and cutting on a sliding microtome with a conventional or replaceable knife. Best results were obtained by cutting pre-moistened wood surface on a sliding microtome with a replaceable knife, and the surface additionally dusted with gold. The optimal method of preparation is technically not demanding or time consuming, and the obtained results satisfy all the needs for researching wood anatomy. Comparison of the light microscopy and SEM microscopy showed good comparability of techniques at smaller magnifications and a significant advantage of SEM in larger magnifications. With SEM good results were achieved even at magnitudes up to 8000 times. It was demonstrated that the use of the SEM opened new scope in the investigation of the wood structure and properties. In the framework of this thesis, guidelines for the optimal preparation of samples were prepared and theoretical and practical basis for further investigations of wood anatomy using SEM at the Department of wood science were provided