Research Articles

It has been reported that a conductivity of 100 S/cm of carbonized cellulose is obtained when the carbonization temperature is higher than 2000 °C. However, such high temperatures require expensive equipment and are energy consuming. In this study, carbonized multi-walled carbon nanotubes (MWCNTs)/cellulose composites fibers with a conductivity of 105 S/cm were prepared. They were prepared based on cellulose (in the carbonization temperature 1000 °C), a naturally abundant and low-cost material. The mechanism of improving electrical conductivity was studied. The MWCNTs played the role of a conductive bridge between the nano-carbonization cellulose blocks. As the template of cellulose graphitization, MWCNTs not only can improve the degree of cellulose graphitization but can also change the microstructure of carbonization cellulose from nano-spheres to sheets. This preparation method can be applied to other carbon materials to make highly conductive fibers or various conductive structure materials, such as a conductive film or an aerogel. This study broadens the application of cellulose in the field of electricity. The obtained conductive fibers have great potential in a range of applications, such as wearable electronics and low-cost energy storage.

Initial water leaching affects were studied relative to the rot resistance of 21 tropical wood species to the brown-rot fungus Coniophora puteana and the white-rot fungus Trametes versicolor. The rot resistance of tropical woods, determined by their weight loss (∆m) at 6-weeks fungal attack, was differently influenced by the initial water leaching, as follows: in the 1st group of eight durable species (dark red meranti, macassar ebony, cerejeira, merbau, santos rosewood, zebrano, wengé, and karri) there occurred a very significant decrease of their high rot resistance (with statistical confidence in the range 99 to 99.9% for different species); in the 2nd group of 10 durable species (ipé, yellow balau, doussié, bubinga, ovengol, padouk, iroko, blue gum, maçaranduba, and makoré) there did not occur a decrease of their high rot resistance; and in the 3rd group of three less durable species (okoumé, tineo, sapelli) a weaker rot resistance did not change due to leaching. The durable tropical woods (18 species from the 1st and 2nd groups) were more resistant to the brown-rot fungus (∆mC.p.-average = 0.72%) than the white-rot fungus (∆mT.v.-average = 1.07%). However, this phenomenon was no longer apparent after water leaching (∆mC.p.-Leached-average = 2.61%; ∆mT.v.-Leached-average = 2.32%).

A high-speed milling test was performed with a self-developed wood-plastic composite using uncoated and coated carbide cutting tools. The nose width was used to represent the tool wear. An advanced tool measurement system was adopted to measure the wear of each tool. The influence of some cutting parameters, including spindle speed, feed rate, axial cutting depth, and radial cutting depth, on the tool wear was analyzed using a single factor test method. Scanning electron microscopy was used to observe the wear morphology on the rake and clearance face of the tool before and after the tool was worn. The results showed that the tool nose width increased with increased axial cutting depths or spindle speeds, while the radial depth under the condition of the same cutting length decreased with an increase in the feed rate. Moreover, the main form of tool wear was abrasive wear and coating peel-off when the wood-plastic composites were machined with high-speed milling.

An ultraviolet (UV) aging test chamber was used to analyze the aging behaviors of wood flour-poly (lactic acid) (PLA) 3D printing filaments under different temperatures. The materials were granulated using a twin-screw extruder, and the filaments were prepared using a single-screw extruder. The aging resistance was determined by comparing the color, tensile strength, scanning electron micrographs, and water absorption rate of the filaments before and after being processed. The aging behaviors tended to be stable when tested at 40 °C for 80 h, or 50 °C for 60 h, or 60 °C for 40 h. At this status, the tensile strength of the filaments was reduced by 44% compared to the originals; the internal structure of the filaments was severely damaged from the SEM images, and obvious porosities can be identified. The water absorption rate was greatly improved. The chromatic degradation (△E*) increased to 10.8 when tested at 40 °C, while this value increased to 10.9 at 50 °C and 10.8 at 60 °C. Therefore, the increase of aging temperature accelerated the UV aging process. It is recommended to add some ultraviolet absorbent into the filaments in order to improve the UV resistance of the materials.

The ability of woody plant species to remediate heavy metals contaminated soils was investigated with the addition of sewage sludge. Jatropha curcas, Hibiscus cannabinus, Acacia mangium, and Syzygium cumini growth was monitored on an Oxisol- and an Ultisol-treated soil with sewage sludge at a level of 0% w/w, 5% w/w, or 10% w/w. The sewage sludge was found to enhance soil fertility, as shown by an increase in soil pH, cation exchange capacity, exchangeable bases (potassium, calcium, and magnesium), available phosphorous, total carbon, and total nitrogen. However, zinc and copper accumulated in soils at toxic levels; thus, they had to be removed before being used for crop production. The concentration of the two heavy metals in Jatropha curcas and Hibiscus cannabinus at harvest were higher than those of Acacia mangium and Syzygium cumini. The high uptake of zinc and copper by the first two plant species was the result of their high translocation factor, although the bio-concentration factor was low. Thus, Jatropha curcas and Hibiscus cannabinus were considered tolerant to zinc and copper toxicity and able to remove the metals efficiently from the contaminated soils.

A method to measure the contact forces and deformations of mortise and tenon joints based on previous theoretical studies was proposed. The influence of the tenon fits and grain orientations on the contact forces and deformations of the mortises and tenons were studied using this method. The testing method and equations were all introduced in detail. The results showed that the contact force between the mortise and tenon with the tenon in the radial grain orientation was larger than that for the tenon in the tangential grain orientation with the same tenon fit. An exponential relationship between the contact force and tenon fit was found. Also, the deformation of the mortise was 3.6 times smaller than the tenon with a tangential grain orientation and 2.2 times smaller than the tenon with a radial grain orientation.

The spill of crude oil products into the environment has a negative impact on the ecosystem. Sorption materials are utilized as the means of their elimination. The sorption capacity of selected organic and inorganic natural sorbents, such as needles (Larix decidua, Abies alba, and Pinus sylvestris), sawdust from logging (Fagus sylvatica, Picea abies), leaf residues (Fagus sylvatica), moss (Ceratodon purpureus), soil, and synthetic sorbents Absodan Plus, expanded perlite, Eco-dry plus, and Reo Amos were all tested according to the standard ASTM F726 (2012). The natural sorbents were tested at various moisture contents (wet, air-dry, and dry) ranging from 0 to 82%. The pollutant used in the experiment was the low-viscosity engine oil 10W 40. The best sorption capacity among the wet sorbents was achieved with larch needles (11.1 g/g). Moss exhibited the best sorption capacity (25.2 g/g) among the air-dry sorbents. Regarding air-dry sorbents, larch needles, spruce sawdust, and beech sawdust showed the best results. When further dried, their sorption capacity decreased. Soil was the least efficient natural sorbent with a sorption capacity that ranged from 0.45 to 3.82 g/g. The best sorption capacity of 11.5 g/g among the synthetic sorbents was in Reo Amos. The sorption capacity of natural and synthetic substances was comparable.

To investigate the production of cellulases and hemicellulases from Aspergillus niger MTCC9931, solid state fermentation (SSF) was performed using 10 different lignocellulosic materials derived from agrowastes, i.e., rice straw, rice husk, wheat straw, corn cob, sugar cane bagasse, saw dust, banana stalk, Eichhornia, Parthenium stalk, and residual fruit pulp. Among these agrowastes, the maximum yield of reducing sugars (116.46 ± 2.56 g/mL) was observed with residual fruit pulp. Further, the same substrate showed the highest endoglucanase (389.1 ± 0.44 IU/g), MCC-adsorbable endoglucanase (3.4 ± 0.14 IU/g), cellulase (12.0 ± 0.13 IU/g), and FPase (4.9 ± 0.64 IU/g) activities. Sawdust showed the maximum xylanase activity (7478.0 ± 6.51 IU/g), and corncob showed maximum β-glucosidase activity (79.87 ± 1.15 IU/g). The maximum activities of all enzymes were observed at 72 h of SSF under shaking conditions. A. niger MTCC9931 can be concluded to be an important strain for potential applications in saccharification. The enzymatic hydrolysates of the agrowastes were used as substrates for ethanol production by Saccharomyces cerevisiae MTCC174. The maximum yield (35.34 g/L) of ethanol was obtained when residual fruit pulp was used as a substrate. This study has further demonstrated the feasible biotechnological conversion of agrowastes to produce ethanol using both A. niger and S. cerevisiae.

N-doped porous carbon materials derived from bamboo fibers (NBFCs) were synthesized through a simple simultaneous activation and carbonization method. The effects of the adsorbent dosage, absorption temperature, pH of the solution, initial concentration, and contact time on the absorption of methylene blue were investigated. The equilibrium, kinetics, isotherms, and thermodynamics of the adsorption process were also analyzed. The results showed that NBFC-800 had a good adsorption capacity of 816.0 mg/g and a high removal efficiency of 93.3% during the optimum absorption process with an adsorbent dosage of 0.8 g/L, adsorption temperature of 25 °C, initial concentration of 700 mg/L, and a solution pH of 9.0. The adsorption process included instantaneous adsorption or external surface adsorption, intraparticle diffusion, and an equilibrium process. Methylene blue adsorption of NBFC-800 agreed with the pseudo second-order model and belonged to the Langmuir isotherm model. The results will be useful for the development of high-performance NBFCs to efficiently remove methylene blue from wastewater.

Mechanical properties and chemical changes of wood dowel welding were studied using untreated and copper chloride (CuCl2)-treated Betula wood dowels. The effects of the welding times (3 s, 5 s, and 7 s) and the highest temperatures in the welding interface were also studied. The treated wood dowels with a welding time of 3 s and the highest temperature of 265.6 °C had the best pullout resistance. Wood constituents were pyrolyzed by the frictional heat generated from rotational welding to form oxygen-containing materials, most of which were C-O materials. With the extension of welding time, welding interface materials were pyrolyzed deeper, but the rate of pyrolysis decreased, which indicated that the pyrolysis of hemicellulose and cellulose might have occurred in the prior period of the welding process. Acid hydrolysis of hemicellulose and cellulose of the wood dowel treated with CuCl2 might have occurred during immersion, which promoted the formation of molten materials by the depolymerization and pyrolysis of wood constituents. With the same welding time, the content of oxygen-containing materials with treated samples was higher than with untreated samples, which might indicate that more pyrolysis and molten reactions occurred in the treated welding interface.