Recent advancements in “nano-technology” have been modifying our conventional concepts of material sciences and developments. Nano-technology also strongly influences natural biomass products. In general, hierarchical structures of bio-based materials are built up through self-assembly of molecules and are followed by nano-assembly further up to a higher-level structure. The key process for each step is formation of the interactions at the individual sizes. Nature usually performs such a bottom-up process to fabricate a product. On the contrary, we have another direction that is a top-down process. In fact, various methods are now under development as a downsized method. This review attempts to describe the trend of nanofiber technology for cellulose from the viewpoints of fundamentals and recent techniques. Further, our recent technique, nano-pulverization by the aqueous counter collision, successfully decomposes the interactions selectively without any damage to the molecular structure, and finally liberates the components at various sizes into water to provide a transparent and homogeneous component/water system. This method will also be briefly introduced.

View full abstract

In order to clarify the relations among the radial variation of wood fiber length, earlywood vessel lumen diameter and the process of diameter growth, the authors studied wood fiber length, earlywood vessel lumen diameter, and cumulative annual ring width for each ring number from the pith, using a total of 16 disks obtained from 4 parts at different stem heights from 4 individuals of Castanea crenata. The process of diameter growth was classified into the three stages : young stage, middle stage, and old stage, by applying the Gompertz growth function to the radial variation in cumulative annual ring width. The maturation ages of wood fiber length and earlywood vessel lumen diameter were estimated with the segmented nonlinear regression analysis method. As a result, it was found that the maturation age of wood fiber length is younger than that of earlywood vessel lumen diameter, and is near the age at the boundary between the young and middle stages of diameter growth in most cases. The maturation age of earlywood vessel lumen diameter is near the age at the boundary between the middle and old stage in many cases. These results indicate that there is some relation between the radial variation in wood fiber length and earlywood vessel lumen diameter and the process of diameter growth.

View full abstract

A practical earthquake-proof reinforcement of existing wooden houses was proposed. This study focused on deteriorated framing at the sills and columns of external walls of Japanese conventional houses. The proposed method of reinforcement is : (1) Deteriorated sills and the bottoms of columns are removed and replaced with new members. (2) Shear-resistant components with structural wood-based panels, similar to ordinary nailed shear walls used in light frame construction, are installed and nailed to the frame members. (3) The assembled shear walls are anchored to the foundation in the following ways. The bottoms of the columns are fixed to the foundation with steel plates and concrete screws to resist pull-out forces. The sills are fixed to the foundation with concrete screws to resist shear forces. We conducted full scale tests of the reinforced shear walls and single shear tests of column-to-foundation and sill-to-foundation anchor systems. The test results verified the practical applicability of the earthquake-proof reinforcement proposed in this study.

View full abstract

Moment-resisting hardwood dowel joints connecting two members at right angles to each other, such as post and beam joints, would easily fail by splitting of the member into which hardwood dowels are inserted perpendicularly to the grain. In this research, two methods were discussed to prevent the member from splitting ; one is to use long dowels for the joint dowels and the other is to use reinforcement dowels together with the joint dowels. Dowels 12 mm in diameter made of hard maple (Acer saccharum) were glued into post and beam or sill members of SPF glulam with polyurethane adhesives to make the above-mentioned two types of specimens. As a result of moment tests, both the two types were found to be effective in preventing the members from splitting. The observed maximum moments were more than 75% of the estimated values assuming that the joint specimens fail by withdrawal of the joint dowels. Racking tests of hardwood-dowel connected wall-frame specimens of 910 mm in width and 2730 mm in height using reinforcement dowels were conducted to verify the performance of the joints with the reinforcement dowels. As a result, the tested frame type was found to have comparatively large racking resistance ; the shear wall multiplier was evaluated to be 1.5.

View full abstract

According to the Building Standard Law of Japan, flame die-out of the specimen is required to certify fireproof wooden beams and columns in addition to structural strength in the ISO 834-1 fire test. In this study, we dealt with Japanese larch (Larix kaempferi) laminated lumber columns and presented a practical specification for flame die-out of wooden columns by using fire-retardant treated wood. This idea has been suggested but had not been applied successfully. We are attempting to develop wooden fireproof columns by putting fully fire-retardant impregnated wood as a flame die-out layer at appropriate positions in the glued laminated lumber. We used polyphosphatic carbamate as a fire-retardant. Japanese larch is classified among the less permeable species. We also showed how to make laminas whose content of fire-retardant chemicals ranges from 0 to more over 70 kg/m³ within a lamina. Incising treatment with a CO₂ laser was conducted for the flame die-out part and sealer was brushed on the core zone part of the lamina prior to the impregnation treatment. These fire-retardant-impregnated laminated lumber columns stopped burning after exposure to fire.

View full abstract

Rapid pyrolysis of sugi (Cryptomeria japonica) and lauan (Shorea sp.) in an argon atmosphere was performed using a cylindrical reactor equipped with an infrared gold image furnace at 500-1000°C. The reactor was operated at a heating rate of 30°C/s, and the evolved gases were analyzed by gas chromatography. The yield of char was hardly affected by the pyrolysis temperature and was approximately 10 wt% for both sugi and lauan. The gross yields of H₂, CO, CO₂, CH₄, C₂H₄, and C₂H₆ tended to increase as the pyrolysis temperature rose. At 1000°C, the proportion of H₂ in these low-molecular-weight gases was 28 mol% for sugi and 19 mol% for lauan. For enhancing the conversion into gases, zeolite, activated alumina, and kaolin were added to both woods as catalyst. As a result, production of both H₂ and CO were effectively increased for sugi with kaolin and lauan with activated alumina. The individual catalyst caused the amount of H₂ increase for sugi and lauan by factors of 1.7 and 3.2, respectively, at 1000°C.

View full abstract