Measurement of the refining degree of bamboo charcoal by an alternating current method

We investigated a method for measuring the refining degree of bamboo charcoal using an alternating current. The bamboo charcoal was made under heating conditions of 400°–900°C (set temperature) and 0—3 h (holding time at each set temperature). The qualities of the bamboo charcoal could not be estimated from the yield, and electric tests were required. The effect of the variation in sample thickness on the impedance could be ignored. Attaching two plate electrodes to the same surface of a specimen enabled high accuracy and practical use. The impedance was found to be a suitable index for estimating the refining degree of the bamboo charcoal, such as the specific electric resistance. We believe that bamboo changes from an insulator to a conductor suddenly when processed at 600°–750°C for 0–2 h. It is possible that the integral of temperature with time in a specimen during heating is useful for approximately estimating impedance.     

Environmentally benign methods for producing green culms of ma bamboo (<Emphasis Type="Italic">Dendrocalamus latiflorus</Emphasis>) and moso bamboo (<Emphasis Type="Italic">Phyllostachys pubescens</Emphasis>)

The objective of this study was to find an effective method for treating ma bamboo (Dendrocalamus latiflorus) and moso bamboo (Phyllostachys pubescens) using new water-based reagents containing copper. The effects of green-color protection using various treatments on bamboo culms were examined in this study. Two methods were used: heating in a water bath and ultrasonic dipping. The results revealed that excellent green-color protection (a* value of −6.2) was obtained when ma bamboo culms were treated with 0.25% ammoniacal copper quaternary compound-type B (ACQ-B) in a water bath at 100°C for 2 h. It was also found that the wettability of bamboo epidermis increasedsignificantly after pretreatment in a mixture of 1% KOH and surfactant in a water bath at 100°C for 30 min. Furthermore, pretreated moso bamboo culms exhibited excellent green-color protection after they were treated with 0.25% ACQ-B at 100°C for 2 h (a* value of −8.2). This novel treatment method definitely endows the bamboo culms with a fascinating green skin color and consequently could increase the economic value of bamboo products. No improvement in green-color protection was found when ultrasonic energy was added to the water bath at ambient temperature.     

Study of Cr(VI) adsorption onto nitrogen-containing activated carbon preparation from bamboo processing residues

Nitrogen-containing bamboo charcoals were prepared using bamboo processing residues, and modified by melamine or urea. The iodine value of the products we obtained was analyzed, and two samples were chosen for the Cr(VI) adsorption. The experimental results show that under the KOH and carbon ratio of 3:1 (w₁/w₂), activation temperature 800 °C and activation time 1 h, the activated carbons modified by melamine boasted the iodine value of 1144 mg/g and the activated carbons modified by urea boasted the iodine value of 1263 mg/g. In addition, the equilibrium adsorption capacity is 95.3 mg/g for the activated carbons modified by melamine with the adsorbent dosage of 1.0 g/L at an initial pH 2 in the presence of 100 mg/L K₂Cr₂O₇ at 30 °C for 180 min and it is 94.2 mg/g for the activated carbons modified by urea in the same reaction condition. The pseudo-second-order kinetic model can better reflect the two kinds of nitrogen-containing activated carbons adsorption kinetic process of Cr(VI). The adsorption process conforms to the Langmuir model, indicating that the process is single molecular layer adsorption.     

Carbonization of bamboo and consecutive low temperature air activation

Raw moso bamboo (Phyllostachys pubescens) was examined to optimize the carbonization and the consecutive air activation procedure. Influence of sample size, nitrogen flow rate, heating rate and final temperature on the carbon yield and the pore structure was investigated for the raw bamboo. The short length cutting along bamboo trunk and the increase in heating rate to 40°C/min and nitrogen flow rate up to 500 ml/min was found to be advantageous for the carbonization of raw bamboo at 500°C, resulting in a surface area of 230 m²/g with a bamboo char yield of 25% on dry base. In the next step, effects of air treatment temperature, ash content and its composition on the pore development were studied for the prepared bamboo char in comparison with coconut shell char. Additional increase in surface area by 200 m²/g with 97% yield could be achieved conducting the 2-hour air treatment at 280°C for the bamboo char, whereas only a 100 m²/g rise in surface area was attained for the coconut shell char, partly due to the difference in K₂CO₃ content in the char.     

Influence of combined hydro-thermal treatments on selected properties of Turkey oak (Quercus cerris L.) wood

A combined effect of steaming and heat treatment was imposed on green Turkey oak wood, both for sapwood and heartwood. Steaming was carried out in an autoclave at 100–120–130°C whereas heating was carried out in an oven for 2?h at 120–180°C. Equilibrium moisture content at dry, intermediate and moist state both in desorption and adsorption, swelling, cup, twist, color change, and spectral reflectance measures were registered. Swelling and water absorption decreased due to the hydro-thermal treatment. During adsorption, heartwood showed a higher hygroscopic inertia compared to sapwood and this difference increased with temperature. Cup increased with temperature in the steaming process. Twist seemed to be affected more by quality of original trunks than treatments. The wood color was more sensitive at a steaming temperature of 130°C combined with heat treatment at 180°C. Transitional treatments assured more reliable results on homogenization of hue between sapwood and heartwood.     

Improvement of softening treatment technology of bamboo

In order to improve the efficiency of softening bamboo block when manufacturing bamboo veneer, chemistry reagents such as NaHCO₃ are often adopted during bamboo softening treatment. But the results of Fourier transform infrared spectroscopy (FTIR) showed that the band intensity at 1,733 cm⁻¹, assigned to C=O stretching vibration in xylan, was reduced in the spectrum of softening-treated bamboo with NaHCO₃ compared with that of not softening-treated bamboo and softening treatment of bamboo without NaHCO₃. That is to say, that the hemicellulose of bamboo was destroyed after softening treatment with NaHCO₃, which meant that softening treatment of bamboo with NaHCO₃, is not a perfect softening treatment method. Thus, in this paper a softening technology at 120°C for 30 min in a closed container was adopted. The results of FTIR show that there was almost no difference in FTIR spectra between no softening treatment of bamboo and softening treatment of bamboo at 120°C for 30 min, which meant that softening treatment at 120°C for 30 min had no effect on the composition of bamboo. The results of dynamic mechanical analysis (DMA) show that T _g of not softening-treated bamboo was 120°C, while T _g of softening-treated bamboo at 120°C for 30 min was 88°C. T _g of softening-treated bamboo at 120°C for 30 min decreased by 26.7% compared with that of not softening-treated bamboo. The results of hardness show that the hardness of bamboo strip after a softening treatment for 30 min at 120°C decreased by 42.0–54.6% compared with that of not softening-treated bamboo. The results of hardness and DMA show that the effect of softening treatment of bamboo at 120°C for 30 min was resultful.     

Green color protection of bamboo culms using one-step alkali pretreatment-free process

This study evaluated the protection effectiveness of alcohol-borne reagents for the green color of ma bamboo (Dendrocalamus latiflorus Munro) and moso bamboo (Phyllostachys pubescens Mazel). The results show that the types and concentrations of alcohol-borne reagents, the kinds of solvent, and the conditions of treatment greatly affected the green color of these two bamboo species. Without alkali pretreatment, an excellent green color protection (a* = −14.5) was obtained when the ma bamboo culms were treated with 0.5% methanol-borne copper chloride (CuCl₂) at 60°C for 30 min. Similar results were also obtained when ma bamboo culms were treated with 0.5% methanol-borne copper nitrate [Cu(NO₃)₂] at 60°C for 2 h (a* = −13.5). For moso bamboo, an attractive green color in the bamboo culms was achieved by treating the specimens with 1% methanol-borne copper acetate [Cu(CH₃COO)₂] at 60°C for 30 min. The a* value of treated specimens was −13.3. In addition, results demonstrated that ultrasonic treatment was more effective on green color protection than conventional water bath treatment. When moso bamboo was treated with 1% copper acetate at 60°C in an ultrasonic bath for only 15 min, a remarkable green color with an a* value of −13.6 was obtained on the bamboo epidermis.     

Investigation of changes in compressed moso bamboo (<Emphasis Type="Italic">Phyllostachys pubescens</Emphasis>) after hot-press molding

In this study, molding moso bamboo strips to a curved shape using hot-press molding operation was explored. Bamboo strips with different thickness and moisture content (MC) were subjected to press molding under 120–210 °C for different time. Changes in the chemical components of bamboo were analyzed by Fourier-transform infrared spectroscopy (FTIR). Effect of MC on thermal mechanical behavior of bamboo was investigated using dynamic mechanical analysis (DMA). Results showed that the influencing degree of four variables on compression and recovery ratios decreased as: temperature?>?time?>?thickness?>?MC. Compression ratio increased and recovery ratio decreased dramatically when pressing temperature exceeded 180 °C. FTIR analysis indicated that polysaccharide (especially hemicelluloses) underwent a progressive thermal degradation during compression at 180 and 210 °C for 40 min, whereas relative content of lignin increased. DMA results showed that bamboo samples with a higher MC had a lower storage modulus value, confirmed water had a plasticizing effect. The loss factor of bamboo with higher MC (12 and 16%) exhibited two major transitions centred around 100 °C (α₁) and 50 °C (α₂), respectively. The temperature of these α transitions kept almost unchanged as moisture level increased from 12 to 16%. These findings provide fundamental information for the future preparation of curved bamboo as profiled components in engineered products.     

Thermal-death kinetics of the bark beetle (Dendroctonus armandi; Coleoptera: Scolytidae)

Data on thermal-death kinetics of bark beetles are essential to develop phytosanitary heat treatments for pine wood and pine wood packaging materials. Using a heating block system, effects of different heating rates between 44 and 50°C at 2°C intervals on destruction of Dendroctonus armandi adult insect were examined. Heat resistance of the insects was found to increase at low heating rates (0.1 or 0.5°C/min). Therefore, the thermal-death kinetics of the beetles were determined at a high heating rate of 5.0°C/min which simulated the rapid dielectric heating of wood products. Results showed that the thermal death curve of D. armandi followed a zero-order reaction kinetic model, indicating the heat destruction rate of the beetle at different treatment temperatures to be independent of their population size. The required thermal holding times to result in destruction of the entire population were 40, 8, 4, and 2?min at 44°C, 46°C, 48°C, and 50°C, respectively. The evaluated thermal-death kinetic data are useful in developing effective beetle elimination quarantine protocols for the wood. A 50°C ?2?min heat treatment with a heating rate of ～5°C/min can be effectively used for disinfesting bark wood materials.     

Thermal-softening properties and cooling set of water-saturated bamboo within proportional limit

Thermal-softening properties and cooling set of water-saturated bamboo were investigated using stressrelaxation measurements in heating and cooling processes, followed by residual deflection measurement. In the heating process, an obvious decrease in relative relaxation modulus due to thermal-softening of lignin was found at around 60°C. On the other hand, no clear change in the relative relaxation modulus was recognized in the cooling process. After the cooling process, about 65% and 75% of residual set was measured when the specimen was loaded on the epidermis and endodermis side, respectively. Also, residual set depended on the maximum temperature reached in the heating process and the unloaded temperature in the cooling process. From these results, it was deduced that the glass transition of lignin from the rubbery to glassy state is important to fix the deformation. Comparing thermal-softening behavior between bamboo and wood, the relative relaxation modulus of wood decreased steeply at higher temperatures than for bamboo. On the other hand, while about 75% of residual set was also found for wood, almost the same as for bamboo, the recovery of deformation with time was larger for wood than for bamboo. Part of this article was presented at the 53rd Annual Meeting of the Japan Zairyou Society, Okayama, May 2004     

Effects of high temperature kiln drying on the practical performances of Japanese cedar wood (Cryptomeria japonica) I: changes in hygroscopicity due to heating

The effect of heating on the hygroscopicity of Japanese cedar wood was investigated as a simple evaluation of thermal degradation in large-dimension timber being kiln-dried at high temperatures (>100°C). Small wood pieces were heated at 120°C in the absence of moisture (dry heating) and steamed at 60°, 90°, and 120°C with saturated water vapor over 2 weeks, and their equilibrium moisture contents (M) at 20°C and 60% relative humidity (RH) were compared with those of unheated samples. No significant change was induced by steaming at 60°C, while heating above 90°C caused loss in weight (WL) and reduction in M of wood. The effects of steaming were greater than those of dry heating at the same heating temperature. After extraction in water, the steamed wood showed additional WL and slight increase in M because of the loss of water-soluble decomposition residue. The M of heated wood decreased with increasing WL, and such a correlation became clearer after the extraction in water. On the basis of experimental correlation, the WL of local parts in large-dimension kiln-dried timber was evaluated from their M values. The results indicated that the thermal degradation of inner parts was greater than that of outer parts.     

Molecular sieving behavior of carbonized wood: selective adsorption of toluene from a gas mixture containing α-pinene

The adsorption properties of wood carbonized at various temperatures were investigated using a mixed gas containing toluene and α-pinene. Hinoki (Chamaecyparis obtusa) samples carbonized at 500°–1100°C were exposed to gas mixtures of toluene and α-pinene at 20°C. The samples carbonized at 500°–700°C only adsorbed toluene, whereas those carbonized at 800°–1100°C adsorbed both toluene and α-pinene. Analysis of the surface structure of the carbonized wood by nitrogen adsorption at liquid nitrogen temperature indicated that the sample carbonized at 700°C had micropores mainly 0.6 nm in diameter and few mesopores, whereas the samples carbonized at 900°C and 1100°C had mesopores and micropores larger than 0.8 nm in diameter. With the sample carbonized at 700°C, the flat-shaped toluene molecules could probably penetrate into the narrower pores, 0.8 nm in diameter, whereas the bulky globular-shaped α-pinene molecules could not. Carbonization at temperatures higher than 900°C probably enlarged the pore size and thereby reduced the selectivity of adsorption. The results revealed that wood carbonized below activation temperature has a unique flat-pore structure that seems to work as a kind of molecular sieving carbon, successfully removing only the harmful volatile organic compound (VOC), toluene, and leaving behind a pleasant aroma of α-pinene in the atmosphere.     

Effects of extraneous substances,wood density and interlocked grain on fiber saturation point of hardwoods

Abstract

Samples of nine tropical hardwoods from Peru and sugar maple wood from Quebec were selected for moisture sorption and swelling tests at 25°C. These tests evaluated the fiber saturation point (FSP) by two methods: following adsorption over distilled water, and from the volumetric swelling intersection point. Cold-water and hot-water extractives, sequential cyclohexane, acetone and methanol extracts, ash content, wood density and interlocked grain were also determined on matched samples. The results indicated that adsorption tests over distilled water were not applicable for determining FSP in all wood species. Condensation of water vapor apparently occurred, even though temperature during adsorption was controlled to the nearest 0.01°C. The volumetric swelling intersection point method was judged more appropriate. FSP ranged from 15 to 25% for tropical hardwoods and was 30% for sugar maple wood. FSP was negatively correlated with wood density, acetone extracted fraction, interlocked grain and ash content. These parameters each exerted similar effects on variability in FSP.     

Effects of peeling and steam-heating treatment on basic properties of two types of bamboo culms (<Emphasis Type="Italic">Phyllostachys makinoi</Emphasis> and <Emphasis Type="Italic">Phyllostachys pubescens</Emphasis>)

Epidermal peeling (EPT) and steam-heating (SHT) treatments are two widely processing methods in bamboo industry. Moso bamboo (Phyllostachys pubescens Mazel) and makino bamboo (Phyllostachys makinoi Hayata) are important economical bamboo species in Taiwan and China. The subject of this study was to access the changes of chemical and mechanical properties in moso and makino bamboo culms, which were collected from Taiwan and China after EPT and SHT. As regard to chemical properties, the amounts of extractives and ash were increased both in moso and makino bamboos after EPT and SHT. In contrast, the contains of holocellulose and α-cellulose were decreased after EPT and SHT for two bamboos. Moso bamboo collected from China contained the lowest cellulose content but the highest amount of hemicellulose by SHT. The lignin contents of all samples were no significant different after SHT, and it might due to the structure of lignin did not destroy at 120 °C. For the mechanical properties, the density of all makino and moso bamboo samples was reduced after SHT; moreover, the decreasing trend of density was similar to the reducing of holocellulose, α-cellulose, hemicellulose, and equilibrium moisture content (EMC). All bamboo samples without EPT presented the highest modulus of elasticity (MOE) and modulus of rupture (MOR) whether SHT or not. Both MOE and MOR of all bamboo samples were decreased after SHT. The integrity of the bamboo skin is important for the dimensional stability of the bamboo, and the water absorption ability would be increased after EPT; however, SHT decreased the water absorption of bamboo.     

Microwave and steam injection drying of CO2 laser incised Sugi lumber

To investigate the effect of CO₂ laser incising under five drying methods on drying characteristics of Sugi lumber, the squares (120 mm × 120 mm) of Sugi lumber with length of 650 mm were used. A half of samples were incised by CO₂ laser with incising density of 2,500 holes/m². Five types of drying methods were used: microwave drying, steam injection drying, and three combinations of microwave heating and steam injection drying. Steam injection drying was conducted by injecting superheated steam of 120 °C through a perforated plate heated to 140 °C of an injection press. Microwave was irradiated with the power of 3 kW at frequency of 2.45 GHz. The results indicated that incising helps heat through a specimen and thus the whole temperature raised rapidly, which was up to threefolds compared to that of no-incised one. Incised specimens dried by a combination of microwave heating for 1 h and steam injection showed the highest drying rate, which was up to 5.3 %/h. Incising and microwave heating contributed positively to dry lumber under more uniform distribution of moisture content and to reduce surface and internal checks. Incised specimen dried by microwave showed the most uniform distribution of moisture content without surface and internal checks.     

Carbonization mechanism of bamboo（phyllostachys） by means of Fourier Transform Infrared and elemental analysis

Bamboo was carbonized at different temperatures ranging from 200℃ to 600℃.The dependence of the change of hemicellulose,cellulose,and lignin on the temperature was investigated by means of elemental analysis and Fourier Transform Infrared (FTIR) spectra of the residual solid products.The results showed:(1)Below 200℃,hemicellulose in bamboo wasdecomposed and a large amount of hydroxyl groups are dislocated from hemicellulose and cellulose,accompanied by the evolution of water to escape.(2)200℃-250℃,cellulose in bamboo was brastically decomposed whereas the net structure of lignin keep stable,with the except of the dislocation of methoxyl groups from lignin.(3)250℃-400℃,the net structure of lignin collapse,up to 400℃,followed by that the more position in aryl groups are substituted.(4)For bamboo carbonization,the aromatization of residual carbon has approximately completed at the temperature as high as 600℃.But the fusion of aromatic rings possibly does not occur.     

Lethal temperature for pinewood nematode, Bursaphelenchus xylophilus, in infested wood using radio frequency (RF) energy

We evaluated radio frequency (RF) dielectric heating for eradication of pinewood nematodes (PWN) in infested wood. Thirteen temperatures were tested (from ambient to 70 °C) on small wood samples (2.5 × 3.8 × 0.64 cm) to determine the minimum lethal temperature (100 % mortality), which was 56 °C [based on infra-red (IR) thermal images data 55.5–57.4 °C] with a 1 min hold time. We also used thermal probes inside the wood to confirm that temperatures were ≥56 °C. Thirty additional samples were tested bracketing the minimum lethal temperature using 54, 56 and 58 °C with additional replications to produce the minimum sample size equivalent of 100 % mortality of at least 93,616 nematodes to satisfy the Probit 9 efficacy requirement. This minimum lethal temperature was further verified by treating infested large wood blocks (10.2 × 10.2 × 25.4 cm). All samples that met or exceeded the 56 °C lethal temperature for the required 1 min hold time (as measured by probes inserted in the wood and on the wood surface by IR) produced 100 % mortality. The sample size required to show Probit 9 efficacy was also satisfied. This study supports the consideration of RF in addition to microwave (MW) dielectric heating as alternative treatments of wood packaging material for inclusion in ISPM No. 15, provided the treatment delivers the target lethal temperature throughout the profile of the material in industrial scale operations.     

Nickel-catalyzed carbonization of wood for coproduction of functional carbon and fluid fuels I: production of crystallized mesoporous carbon

Japanese larch wood loaded with nickel (1%–4%) alone or with nickel and calcium (0.25%–1.5%) was carbonized at 800°–900°C for 0–120min with a heating rate of 5°–20°C min⁻¹ in a helium flow of 5.8−46.4 ml STP cm⁻² min⁻¹ to examine the influence of these variables on the crystallization of carbon (the formation of T component) and the development of mesoporosity. From the obtained results, reaction conditions suitable for effective production of carbon with the dual functions of adequate electroconductivity and adsorption capacity in liquid phase were established, thereby explaining the factors that govern the process. It was also confirmed that mesopore having a diameter of about 4 nm was selectively produced at the cost of specific (BET) surface area in parallel with the formation of T component. This result provided good insight into how the simultaneous dual function could be realized.     

Color and surface chemistry changes of extracted wood flour after heating at 120 °C

To investigate the effect of heat on color and surface chemistry of wood flour (WF), unextracted, extracted and delignified samples of commercial WF were heated at 120 °C for 24 h and analyzed by colorimetry, diffuse reflectance visible (DRV), attenuated total reflectance Fourier transform infrared (ATR-FTIR) and Fourier transform Raman (FT-Raman) spectroscopies. Unextracted samples showed a slight increase in CIEL^*a^*b^* color coordinates, a ^* and b ^*. Compared with unextracted samples, color changes of the extracted samples varied with composition of the extraction solvents with generally smaller increases in a ^* and larger decreases in b ^* values. Delignified samples were marked by even larger increases in both a ^* and b ^* values. The color changes could be explained by analysis of the respective DRV, FTIR and FT-Raman spectra of the samples before and after heating. Heating of the extracted WF at 120 °C resulted in a red shift of the absorption at 430 nm and increase in absorption in the violet-blue spectral region of visible light. Delignified samples showed even more pronounced absorption in this spectral region after heating.