The Fractal Evaluation of Wood Texture by the Triangular Prism Surface Area Method

Textures of the surfaces of fifteen wood species were characterized by fractal dimension of the triangular prism surface area method. Fractal dimension ranged from 2 to 3, and sharp lightness variation caused high fractal dimension, whereas low values related to smooth variation. Based on this index, wood specimens were generally divided into a hardwood group with value greater than 2.50 and a softwood group with value less than 2.50. Six types of fractal dimension distribution were explored in our experiments, including plane, inclined plane, concave, convex, zigzag distribution, and hilly distribution. From these both the features of local textures and the general variation tendency of the whole surface could be illustrated. It was strongly proposed that fractal dimension should be adopted to quantitatively evaluate wood texture with coarseness and evenness, because such variation was related to the number of grains, surface orientation, and location. For wood color matching, fractal dimension is of great importance in ensuring texture matching to achieve a constructed surface texture close to the features of natural variation. These distribution patterns were considered as a good reference previous to matching. Little variation of fractal dimension along the grain was observed, and this could be used to simplify texture matching by a very limited number of the indices. No significant relationship was found between fractal dimension and lightness, further implying that fractal dimension was independent of lightness

Wood Propionylation in the Presence of Catalysts

Effects of potassium and sodium salts as catalysts on propionylation of wood and on the color change of propionylated wood have been investigated. It was found that potassium acetate, sodium acetate, sodium propionate, and sodium thiosulfate as catalysts were effective for propionylation of wood, and the catalyst loadings (CLs) of them had an effect on weight percent gains. The color of propionylated wood catalyzed with potassium acetate, sodium acetate, or sodium propionate changed very slightly, while sodium thiosulfate-catalyzed wood changed greatly with the increase of CL. Otherwise, potassium sulfate and sodium sulfate showed little or no catalytic effect, and sodium tetraborate decahydrate showed a negative catalytic effect on propionylation of wood

Carbonization of Wood-Silica Composites and Formation of Silicon Carbide in the Cell Wall

Wood-mineral composites (WMCs) impregnated with silica (SiO2) were carbonized at high temperature to form silicon carbide (SiC) directly using carbon from the wood with the impregnated silica. Carbonized composites were investigated using X-ray diffraction and EPMA (electron probe X-ray microanalysis). Water-saturated sapwood specimens of sugi, Japanese cedar (Cryptomeria japonica), were diffuse-penetrated with a colloidal silica solution or a water glass solution followed by drying to fix silica gel for preparing wood-SiO2 composites. The composites were burned at 600°C, 1000°C, and 1300°C for 30-120 minutes in a furnace in nitrogen gas. X-ray diffraction showed that the peak of SiO2 was recognized at 20 = 22°, and the peak became greater with an increase in burning temperature. The peak at 1300°C became very sharp, revealing the change of crystalline structure of SiO2 (cristobalite). In addition, the occurrence of the peak around 20 = 35° at 1300°C appeared, which confirmed the formation of silicon carbide (β-SiC) in the carbonized composites. EPMA observation showed the distribution of silicon in the cell walls that were carbonized at 1300°C. In conclusion, we showed that SiC was produced in the cell walls and the crystalline structure-changed SiO2 (cristobalite) existed in the cell lumina