Research Articles

Changes were determined for the values ​​of physical and mechanical properties resulting from hygroscopicity in some wood species after heat treatment (HT), and to reveal statistically the relationships between the properties. For this purpose, aspen (Populus tremula) and fir (Abies nordmanniana subsp. bornmuelleriana) species were evaluated for weight loss (WL) during HT as well as water thickness swelling (WTS) and weight and volume change rates upon water imersion. The amounts and density values ​​of longitudinal, radial, tangential, and volumetric contractions and expansions, static bending resistance (MOR) and static bending modulus of elasticity (MOE) were examined. From the results and correlation analysis, it was determined that while WL increased in all variations with HT, the WTS values ​​from the HT samples in water for 24 h decreased with the increase in temperature and time, while water retention was at similar rates in all variations, including UT. At the same time, HT resulted in significant decreases in all density values ​​and contraction and expansion values, and the dimensional stability improved. On the other hand, it was understood that HT did not negatively affect both MOR and MOE resistance values ​​at the 180 °C and 200 °C conditions. These results showed that heat-treated wood products can be a good alternative to avoid problems caused by hygroscopicity under the influence of intense water contact.

The shear resistance was measured for Scots pine (Pinus sylvestris) furniture joints assembled using straight, cross, and grooved-patterned dowels fabricated via 3D printing with Poly Lactic Acid (PLA), tough PLA, Poly Amide (PA), and tough resin. Results indicated that the highest shear value was given by the straight dowels joints produced from tough resin with an average value of 2845 N. This was followed by the shear resistance values ​​of grooved dowels with 2819 N and cross dowels with 2725 N. The shear performances of the Scots pine joints produced from tough resin dowels were followed by the shear performances of the joints with different patterns produced from tough PLA, PLA, and PA, respectively. No statistical difference was observed in the shear resistances of the joints produced from dowels with different surface patterns. The shear performance of the tough resin dowels joints was higher than those of the solid wood and PA dowels used in the market. Joints with tough resin and tough PLA dowels exhibited both glue line separation and wood rupture near the dowel edge, whereas PA and PLA dowels primarily failed due to glue line separation.

Effects of ammonia vapor and tannin treatments were studied relative to the properties of wood. The color change, surface roughness, and surface hydrophobicity of Persian oak (Quercus persica), Persian walnut (Juglans regia L.), Oriental beech (Fagus orientalis Lipsky), and Siberian pine (Pinus sibirica) were evaluated after treatments for 8 and 24 h. The color difference (ΔE*) values increased with prolonged exposure, with the highest changes observed in tannin-treated samples exposed to ammonia vapor for 24 h. Pronounced color changes were observed in Siberian pine samples, while beech and oak showed moderate color shifts. Walnut exhibited a more complex response, with an initial increase in yellowness followed by stabilization. Surface roughness measurements demonstrated a significant increase, particularly in maximum height (R_z), indicating substantial modifications to the wood surface. The most significant increase in roughness was observed in the samples treated with ammonia vapor and tannin after 24 hours of exposure, regardless of species type, although oak and walnut showed more controlled alterations. The surface hydrophobicity of the samples was increased after treatment, with the highest contact angle values after treatment for 24 h. This study highlights the potential of tannin and ammonia vapor treatments for improving the aesthetical and surface properties of wood.

The influence of SiO₂ on the properties of lignin spherical porous carbon (LSC) was examined. Evidence suggested that the presence of optimal SiO₂ contributed to stabilizing the spherical structure of LSC and significantly enhanced LSC’s ability to adsorb antibiotics. Lignin/SiO₂ composite microspheres, fabricated through co-precipitation with added sodium silicate, served as precursors for C/SiO₂ composite microspheres (LSC-Si⁽⁺⁾). LSC-Si⁽⁺⁾ demonstrated excellent adsorption capacity for ciprofloxacin (CIP), sulfadiazine (SDZ), and tetracycline hydrochloride (TC). Furthermore, LSC-Si⁽⁺⁾ exhibits excellent physicochemical stability and noteworthy recyclability, maintaining high adsorption capacity after five cycles of recycling. Given the benefits of low cost, ease of production, and excellent adsorption performance, LSC-Si⁽⁺⁾-20 holds promise for removing antibiotic contaminants from wastewater.

Indigofera tinctoria L. is known to produce economically valuable indigo dye. Recently, I. tinctoria has also been considered a potential species for establishing energy plantations because this species can rapidly produce large quantities of biomass. However, knowledge about its fuelwood properties is still limited. To optimize utilization of this biomass material as a source of energy, the fuelwood properties of this species were evaluated. In addition, the effect of radial growth rate on fuelwood properties in this species by mixed-effect modeling approaches were also evaluated. The productivity rate of above-ground biomass was found to be 7.4 tons ha^-1 year ^-1. The estimated average values in fresh weight, dry weight, moisture content, ash content, and carbon content were 7.4 kg, 3.7 kg, 53.4%, 0.90%, and 1.6 kg, respectively. According to the results of mixed-effect modeling, it is concluded that faster-growth characteristics of the tree did not always deteriorate the fuelwood properties of this species.

Nine-layer laminated veneer lumber (LVL) 1300 by 850 mm, in nominal thickness of 20 mm, was produced using beech veneer and reinforced LVL (RLVL), by inserting carbon fiber fabric between the veneer sheets. The research aimed to assess the enhancement of flexural properties, both in edgewise and flatwise bending, of beech LVL reinforced with carbon fiber fabric. Two types of reinforcements were made, using two types of adhesives: phenol-formaldehyde (PF) and polyurethane (PUR), in the industrial conditions. In the first group of samples (K1), the reinforcements were placed further from the neutral axis, and in the second group (K2) closer to the neutral axis. These groups were compared to the unreinforced control sample (K). Some physical properties, bending behavior parallel to the grain, and failure mode were determined and analyzed. Edgewise bending strength of the RLVL was about 11% higher than the control in the case of PF adhesive, while flatwise bending strength was about 40% lower than the control in the case of PUR adhesive. The experimental data were verified using the ANOVA model. The most important results of the study define different behavior and fracture mechanisms for each reinforcement and adhesive, highlighting the potential of RLVL for structural applications.