Band 71, Heft 5

Wood-derived activated carbon fibers (WACF) with large mesopore volumes have been developed, which were prepared only by H 3 PO 4 as the activator (WACF-P). By carefully controlling the H 3 PO 4 concentration at the 10% level and activation temperature at 700°C, the contribution of mesopore to the total pore volume of WACF reached 87%, which is much higher than those obtained in previous studies on ACF. The porosity development mechanism of WACF-P was interpreted based on the data of pore characteristics, crystallite structure, surface elemental constituents, and surface functional groups. The activation effect of H 3 PO 4 seems to be mainly relied on the enlargement of the existing defects in the fibers, which are developing to mesopores. Based on the large mesopore volume, the WACF-P have an excellent adsorption property for xylenol orange (XO). In general, the WACF-P are suitable for the adsorption of macromoleculses.

Active functional groups and interactions involved in the sorption of Li + ions from an aqueous LiCl solution onto the Norway spruce sapwood (sW) flour have been investigated. To this purpose, sW was delignified by peracetic acid (PAA) treatments and the resulting holocelluloses (HC 6 h , HC 24 h , HC 51 h , HC 72 h , where the lower case data indicate the PAA treatment time) with various lignin contents were immersed in aqueous solution of LiCl and the sorption effects were studied by flame atomic emission spectroscopy (FAES), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). The Brunauer- Emmett-Teller (BET) specific surface area increased from 1.5±0.0 m 2 g −1 to 2.4±0.1 m 2 g −1 for HC 6 h , and from 1.6±0.03 m 2 g −1 to 2.7±0.6 m 2 g −1 for HC 72 h upon LiCl treatment. It was found that Li + /Cl − retention occurs predominantly via O-containing functionalities and the carbohydrate-rich samples sorbed more Li + . Upon LiCl treatment, the mobility and accessibility of the wood matrix was enhanced, possibly by interference of the introduced ions with the existing intermolecular bonds.

A research group on forest products from School of Agriculture – Sao Paulo State University. Brazil developed a portable hardness tester for wood, which is based on a displacement transducer and an embedded electronic processor for dynamic evaluation of hardness. This paper presents the results of calibration tests of the equipment, carried out on seven species of Eucalyptus . A new methodology for dynamic hardness calculation has been introduced, which relays on the reaction force of the indentation, while the measurements of indentation depth are performed under load. A moderate to strong linear correlation to Janka hardness and its variations were found. This new approach avoids the classical problems of Brinell hardness test in terms of “sinking-in” (causing diffuse edges) and elastic recovery of the indentation.

Investigations of quasi-static and fatigue failure in glued wooden joints subjected to tensile shear loading are presented. Lap joints of beech wood ( Fagus sylvatica L.) connected with four different types of adhesives, i.e. polyurethane (PUR), melamine urea formaldehyde (MUF), bone glue and fish glue, were experimentally tested until the specimens failed. The average shear strengths obtained from the quasi-static test ranged from 12.2 to 13.4 MPa. These results do not indicate any influence of the different adhesive types. The influence of the adhesives is only visible from the results of the fatigue tests, which were carried out under different stress excitation levels between 45% and 75% of the shear strength. Specimens bound with ductile adhesive (PUR) showed a slightly higher number of cycles to failure ( N f ) at low-stress levels and lower N f at high-stress levels in comparison to more brittle adhesives (MUF, fish glue). In general, the performances of animal glues and MUF were similar in both quasi-static and fatigue loading under dry conditions.

Wood poles are a critical part of the electrical transmission system in North America. Wood poles are normally selected on the basis of visual features such as knots, slope of grain or other defects, but there is currently no simple, nondestructive bending (NDB), pre-flexural testing for sorting poles prior to use. In the present paper, the potential for NDB based on bending below the proportional limit was examined to calculate modulus of elasticity (MOE) and thereby predict actual modulus of rupture as determined by destructive bending (MOR DB ). The investigation was performed on 92 full length 13.3-m long Douglas-fir pole sections. Pre-flexural testing was reasonably correlated with MOE DB , but less well correlated with MOR DB . The testing also revealed that visual selection of the best face of a pole, which is used to select a pole oriented to line direction (the “best face”), was poorly correlated with pre-flexing. Increasing the number of NDB tests did not noticeably improve the prediction. The results suggest that pre-flexing might be useful for identifying poles’ performance in service, if more data are available.

Norway spruce ( Picea abies L. Karst.) and European beech ( Fagus sylvatica L.) samples were loaded in shear mode aimed at testing their elastic material characteristics applicable in finite element analysis (FEA). More precisely, experimental and numerical analyses of uniaxial tensile test parallel to grain in longitudinal-radial ( LR ) or longitudinal-tangential ( LT ) shear of plane are described. The elastic material models in the FEA are based on own experimental data and those of the literature. The verification of material characteristics was performed by 3D numerical models with the same parameters as for the experimental tests. The fully orthotropic elastic material model was applied in the uniaxial tensile tests. The digital image correlation (DIC) method served for verification of the numerical models with proposed elastic material characteristics. Good correlation was found between numerically predicted and experimentally measured data. The minor differences between the two data sets could be mainly attributed to certain natural wood characteristics, which were neglected in the proposed models, i.e. especially variation of earlywood and latewood density. The proposed elastic material models offer general data sets for the evaluation of mechanical response of timber structures and especially in timber connexions.

The adsorbed water influences significantly, the physical and mechanical properties of wood. In the present paper, the spatial distribution of adsorbed water in wood cell walls has been studied by μ-Fourier transform infrared (μ-FTIR) and confocal Raman spectroscopy. In situ μ-FTIR spectra were collected from three randomly selected areas in different cell wall regions, which were exposed to an environment with 0% to 96% relative humidity (RH). The water adsorption sites were easily detectable based on OH, C=O, and C-O group vibrations and it was shown that the adsorbed water concentration was not uniform in different regions. Confocal Raman spectroscopy images were collected from the cell corner (CC) and middle layer of the secondary wall (S2) and the non-uniformity of water distribution could also be confirmed by this approach. It was demonstrated that both μ-FTIR and confocal Raman spectroscopy provide valuable information about the spatial distribution of adsorbed water in morphologically distinct cell wall regions.

The focus of this study is the development of a specific drying model for the design and operation of drying systems for stacked lumber in drying chambers. Namely, a comprehensive three-dimensional (3D) mathematical model of heat and moisture transfer in stacked wood has been developed, where the wood was subjected to convective drying that accounts for the effect of the surrounding fluid flow. In developing the model, the characteristics of wood and fluid flow, i.e. velocity, pressure, temperature, relative humidity (RH) and moisture content (MC) are described by the conservation equations of mass, momentum and energy as well as thermodynamic relations. The model presented was solved numerically by means of the commercial software COMSOL Multiphysics. The simulation results were validated against experimental data under laboratory conditions. Air current circulation was found to be non-uniform during drying, which accounts for the different rates of temperature and MC in wood. At the initial stage of drying, this difference was relatively large but reduced gradually with the drying process. Meanwhile, the transient gathered phenomenon related to humidity around the stacked wood in the chamber was observed in response to air current circulation and evaporation rate of moisture. Finally, sources of error incurred in numerical calculations and actual detection were identified and discussed.

The genus Aureobasidium is wellknown as a wood-staining mold and as a black yeast-like fungi, which produces mainly dark spores or pigmented hyphae within the wood cell lumens. Nevertheless, few studies are dedicated to wood-colonizing Aureobasidium species and little is known about the wood degradation patterns of this genus. In the present study, four Aureobasidium species, including Aureobasidium melanogenum , Aureobasidium leucospermi , Aureobasidium pullulans , and an unknown Aureobasidium sp., were isolated and identified based on phylogenetic analysis. A. melanogenum and A . leucospermi were observed for the first time in Korea. The degradation pattern of Douglas-fir by Aureobasidium was observed for the first time by scanning electron microscopy (SEM). All tested Aureobasidium species except an unknown Aureobasidium sp. revealed soft-rot Type ΙΙ (erosion) in sapwood pine.

Silver-clay nanohybrids based on silver nanoparticles (AgNPs) with montmorillonit (MMT) and milled MMT, shortly AgMMT nano and AgMMT milled , have been prepared to improve the performance of antibacterial properties of paper. The results obtained by dynamic light scattering indicated the presence of silver particles in the nanometer range, which have a great accumulation tendency. The results of AAS and ICP-AES tests showed that nanosilver amount in the AgMMT milled was doubled compared to the AgMMT nano , but according to the EDX results, the amount of nanosilver in paper treated with the former was less than in the latter. FE-SEM images showed that the dimensions of deposited nanosilver on the surface of clay were smaller than in case of AgNPs alone. Papers treated with nanohybrids had better antibacterial properties compared to that prepared by naked nanosilver. It was also found that the antibacterial property of papers treated with AgMMT nano were more stable during three-stage tests compared to those with AgMMT milled . Nanohybrids with Ag conc. more than 15 ppm, especially hybrids with Ag conc. of 50 ppm, result in a significant improvement in antibacterial properties of paper. It can be concluded that silver-clay nanohybrid with a 25-ppm concentration of nanosilver could be the best and most economic antibacterial component.