Volume 15 Issue 1

A set of reformulated theoretical formulas was developed to measure the relationships between moisture content (MC) and stress wave propagation velocity, dynamic modulus of elasticity ( “E” _”d” ), and modulus of stress-resistograph of the wood. The theory of wood science, elastic mechanics, wave science, and stress wave propagation were used as the theoretical basis. Using larch as the material, both stress wave and micro-drilling resistance technologies were used to study the timber property changes under different moisture contents. The results showed that when the MC of wood did not reach the fiber saturation point (FSP), the wood property decreased sharply with increased MC. However, the study also found that when the MC of wood was higher than the FSP, the wood property decreased with increased MC. In addition, the experimental results showed that the variation trend calculated by the new set of theoretical formulas was consistent with the numerical variation trend measured by the experiment, and the coupling effect of stress wave and micro-drilling resistance was high. This set of theoretical formulas can provide a reference for the research on nondestructive testing and performance evaluation of ancient building timber.

The use of wollastonite as a natural additive for the welding of Scots pine improved the water resistance and shear strength of the welded joint. The X-ray computed tomography images revealed that the welding of Scots pine with wollastonite could postpone crack formation in the welded joints. The specimens welded for a longer time (5 s) had a more uniform distribution of wollastonite particles in welded joints. The microstructure of the wood and the thickness of the wood cell walls also had a great influence on the thickness and strength of the welded joints. Water immersion tests showed that the use of wollastonite in wood joints was able to meet the requirement of resistance to frequent short-term and long-term exposure to water.

The hydrochloric acid-catalyzed hydrothermal pretreatment of brown seaweed residues (Laminaria japonica) was optimized with respect to three operating factors: temperature, time, and the concentration of HCl, using response surface methodology (RSM). In order to confirm the significance of the quadratic model, an analysis of variance was performed, which resulted in an F-value of 11.09. Therefore, the regression model was highly significant. Additionally, the pareto chart was used to contrast the absolute values of the standardized effects. Response surface and contour plots were used to illustrate a surface with a maximum. The perturbation plot showed the sensitivity of the reducing sugars yield to the independent factors. Under the reaction conditions of 142 °C, 9 °C, 18.6 min, and 0.1 N HCl concentration, the experimental yield of 113.0 mg/g and the predicted yield of 107.5 mg/g were obtained.

Properties of Borneo sago starch reinforced poly-(lactic acid) (PLA) composites were evaluated, with attention to the effects of treatment with acrylic acid, benzene diazonium chloride, and tetrahydrofuran. The PLA-sago composites treated with tetrahydrofuran had the highest tensile strength, with a maximum value of 0.85 MPa at 20 wt%; whereas the PLA-sago composites treated with benzene diazonium chloride had the highest modulus of elasticity, with a maximum modulus of elasticity of 28 kPa at 5 wt%. Scanning electron microscopy images of the surfaces showed good interfacial contact between the PLA and the sago starch treated with benzene diazonium chloride. The Fourier-transform infrared spectra revealed the functional group characteristics of the chemicals composition of the materials. According to the thermogravimetric analysis results, all of the composites displayed thermal stability up to a temperature of 300 °C. The differential scanning calorimetry analysis revealed that the poly lactic acid-sago composites treated with benzene diazonium chloride had the highest melting point.

This work physically, mechanically, and chemically characterized the composites produced from Portland CP II-E32 cement and fresh Indian cedar wood particles previously treated by immersion in hot and cold water. Density values for wood particulate composites were around 50% lower compared with the wood-free control treatment, from 0.88 to 1.78 g/cm³. A larger swelling was observed for the composite material. The results of compressive strength and stiffness indicated that there is no need for particle treatment for composite production. Hot and cold water immersion treatments reduced the total Indian cedar wood extractives by 33% and 42%, respectively. Optical microscopy analysis was used to identify adhesion failures between the cement/wood interface of the composite produced with fresh particles, which presented a higher percentage of extractives. This result indicated that the greater concentration of total extractives partially inhibits the matrix-matrix interaction reinforcement. Despite the reduction in total extractives caused by the treatments, this process is not necessary for the composite production because there is no statistical difference between the treatments. The values obtained for the composite indicate the possibility of application in sealing blocks in light construction systems.

The withdrawal strength of plain dowels with nominal diameter of 8 mm was compared with the spiral dowels manufactured from beech (Fagus sylvatica L.) and oak wood (Quercus robur L.). The test specimens were tested after conditioning at relative humidity (RH) 25%, 45%, 65%, and 85% at a constant temperature of 20 °C. Therefore, the influence of relative humidity (respective moisture content), dowel structure, and wood species of the dowels on the withdrawal strength was determined. The structure and low humidity (RH 25%) caused the highest strength (8.6 MPa) of spiral dowels. Compared to plain dowels, the higher withdrawal strength of spiral dowels was statistically significant. Adversely, the lowest withdrawal strength was found for plain beech dowels (3 MPa), which, in addition to higher relative humidity (RH 85%), was also caused by a combination of plain structure and greater diameter of the dowels, thereby decreasing the amount of adhesive in the bonded joint. The influence of the wood species of the dowels was not statistically significant overall.

To investigate the influencing mechanisms of calcium and magnesium on the solid products of biomass torrefaction, cellulose was selected as the feedstock in this article. The experiments were conducted in the holding temperature range of 200 °C to 300 °C under the atmosphere of nitrogen. Based on the impregnation methods (chlorides, hydroxides, and acetates of Ca and Mg), the results showed that the solid product yield of torrefacted cellulose impregnated with calcium or magnesium salts was lower than that of raw cellulose torrefaction at 200 °C to 275 °C. However, at 300 °C, the solid product yield of impregnated cellulose torrefaction was higher. During torrefaction, the CaCl2 had a stronger effect than other calcium salts. The Mg(CH3COO)2 had less of an effect than other magnesium salts. The crystallinity of the torrefied cellulose with impregnated calcium or magnesium salts was considerably reduced from 51.1% (raw cellulose) to 7.7% (addition of CaCl2), 34.8% (addition of Ca(OH)2), 28.6% (addition of Ca(CH3COO)2), 9.2% (addition of MgCl2), 13.6% (addition of Mg(OH)2), and 12.0% (addition of Mg(CH3COO)2). The results of the thermal gravimetric analysis showed that the impregnated calcium or magnesium salts dramatically reduced the activation energy of the torrefaction.

The possibility of replacing the rye flour commonly used as a filler for urea-formaldehyde resins was investigated for plywood production with birch bark characterized by various particle dimensions. The effects on the curing and rheological properties of the adhesives were investigated. Moreover, the plywood was tested to evaluate the formaldehyde emissions, bonding quality, modulus of elasticity, and bending strength. The results showed that the size of the bark particles had a significant effect on the viscosity of the adhesives but did not affect other properties of the resin. Replacing the flour with the bark significantly decreased the formaldehyde release, but there was no clear correlation with the dimensional fraction of the bark powder. The particle size had notable effects on bonding quality and mechanical properties. The best results were obtained for a sieve with square holes whose inside lengths were 0.315; however, all plywood samples achieved shear strength values exceeding the requirements of EN 314-2 (1993).

Thermal flow molding of wood powder was carried out with a natural binder consisting of sucrose and citric acid (SC binder) for fabricating wood products without synthetic resins. The testing of thermal flow and molding of the wood powder with SC binder was done to analyze the effect of added SC binder, as well as to optimize the molding conditions, such as temperature, binder content, and mixture ratio of the sucrose and citric acid. The wood powder with SC binder flowed successfully at an optimum temperature of 180 °C in the thermal flow test. In addition, it was possible to form a composite wood plate by molding with thermal flow, and the moldability was improved by increasing the sucrose ratio in the SC binder. Density, bending strength, and thickness swelling after water immersion of the plate molded under the optimum molding conditions were 1.4 g/cm3 to 1.5 g/cm3, 28 MPa to 37 MPa, and 7% to 10%, respectively. These results indicated a possibility

A Ni/Zr-MOF catalyst supported on Zr-metal organic framework (Zr-MOF) was prepared by a homogeneous precipitation method and was used in the co-gasification of wet sludge and straw. The Ni/Zr-MOF catalyst was characterized via thermogravimetric, X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and Brunauer-Emmett-Teller analyses. The experimental results illustrated that the Zr-MOF crystals were an octahedral structure with a specific surface area of 806 m2/g, and had mesoporous structure. Nickel was uniformly dispersed on the surface of the catalyst, and most of the Ni/Zr-MOF crystals maintained an octahedral morphology. Compared with non-catalyst biomass gasification, the H2 yield increased from 0.39 mol/kg to 11.87 mol/kg using the Ni/Zr-MOF catalyst at 500 °C. After 10 instances of reuse, the H2 yield was still as high as 10.11 mol/kg. The Ni/Zr-MOF catalyst exhibited high catalytic activity and stability for biomass gasification at low-temperature.