Woodceramics Prepared from Wood Powder/Phenolated Wood Composite

In this paper, composites were made from wood powder and its phenolated product, and then were carbonized into woodceramics. The effects of the content of the phenolated wood in the composites on the forming ability, size, density, compressive strength, volume electrical resistivity, and specific surface area of the woodceramics were investigated. It is suggested that in the preparation of woodceramics, phenolic resin can possibly be substituted totally by phenolated wood that is the main constituent of liquefied wood.     

Effect of Components upon the Surface Area of Woodceramics

The surface area of woodceramics, a novel porous material, plays an important role in catalysis, water treatment and air filtration etc. In the present study, the effect of components of the woodceramics, i.e., cellulose, lignin and phenolic resin, upon the surface area of woodceramics was investigated. The experimental results showed that cellulose, lignin and phenolic resin represented quite different carbonization ratios and surface areas during the carbonization. The results also indicated that lignin and phenolic resin were prone to carbon precipitation during heat treatment, compared with cellulose. It was deduced that the surface area of the woodceramcis depended on the amounts of the cellulose, lignin in the raw woody material, the amount of the phenolic resin and the carbonization temperature.     

酶解木质素改性木陶瓷制备与性能研究

以木粉和热固性酶解木质素改性酚醛树脂为原料,经1000℃高温真空炭化制得一种新型木陶瓷。研究了酶解木质素及其含量对木陶瓷碳得率、体积收缩率、表观密度、显气孔率、弯曲强度和压缩强度的影响,并且采用TGA技术对酶解木质素改性酚醛树脂的性能进行分析。结果表明,通过该工艺用酶解木质素改性制备木陶瓷是可行的,酶解木质素含量对木陶瓷的性能有较大影响。随着酶解木质素含量的增加,显气孔率、体积收缩率增加,而碳得率、表观密度、弯曲强度和压缩强度反而下降。并且酶解木质素的引入改变了酚醛树脂的性能,使其残碳率降低。     

Effect of carbonization temperature on the structural changes of woodceramics impregnated with liquefied wood

Structural inspection of carbonized woodceramics impregnated with liquefied wood was performed by dimensional shrinkage and weight loss, the content of carbon and oxygen with X-ray energy dispersive analysis (EDS), Raman scattering spectroscopy, laser microscope observation and X-ray diffraction. The results showed that with the increasing temperature, the dimensional shrinkage, weight loss and the ratio of carbon to oxygen in woodceramics increased, the (002) interplanar spacing of the crystalline component in woodceramics decreased and the value of R increased above 650°C. Woodceramics have a turbostratic structure with cracks, and internal stresses etc., especially for those carbonized at temperatures over 650°C.     

黄杨木制备SiC木质陶瓷的性能与表征

SiC木质陶瓷是近年来应用前景广阔的新型陶瓷材料,以绿色可再生的木材为原材料,通过反应烧结工艺制备出的陶瓷具有优良的高温力学性能。为探究影响生物质陶瓷性能的因素,将黄杨木在800 ℃氮气保护下热解形成生物质炭坯,然后在1 650 ℃和1 900 ℃两种高温下进行熔融渗硅制备SiC木质陶瓷。利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)研究SiC木质陶瓷的物相组成和微观结构,采用阿基米德排水法和三点弯曲法测定陶瓷的开孔率、密度和弯曲强度,再使用维氏硬度计测定SiC木质陶瓷的显微硬度。研究结果表明:在1 650 ℃下通过熔融渗硅可以得到微观结构均匀的SiC木质陶瓷,在1 650 ℃比在1 900 ℃下熔融渗硅制备陶瓷的力学性能更优异,陶瓷的密度更大,为2.27 g/cm³,此时弯曲强度为192.45 MPa;游离Si会提高SiC木质陶瓷的密度,增强陶瓷的弯曲强度。     

木焦油基活性碳的制备及其对亚甲基蓝的吸附性能研究

木焦油是木质生物质材料的高温裂解产物。以木焦油为碳源,以甲醛化处理后的木焦油为前体,通过碳化-活化制备木焦油基活性碳材料。并以制备的木焦油基活性碳为吸附剂,研究了其对模拟水体中亚甲基蓝的吸附性能。结果表明,以木焦油为前驱体经高温碳化活化制备的多孔活性碳,比表面积可达1373Sm_²?g_^-1,表面含有丰富的含氧官能团。木焦油基活性碳对亚甲基蓝具有良好的吸附性能,准二级动力学模型能更准确的描述木焦油基活性碳吸附亚甲基蓝的动力学过程。吸附等温线更符合Langmuir等温吸附模型,木焦油基活性碳对亚甲基蓝的最大吸附容量可达559 mg?g_^-1。热力学分析表明亚甲基蓝在木焦油基活性碳上的吸附是放热和自发的。利用木焦油制备的活性碳材料对亚甲基蓝具有较高的吸附容量,是一种具有潜在应用前景的吸附材料。     

Mechanical Properties of Woodceramics: A Porous Carbon Material

The mechanical properties of woodceramics, which are new porous carbon materials utilizing the natural structure of wood, were investigated. The effects of burning temperature and amount of impregnated phenol resin on Young's modulus, compressive strength and fracture toughness were measured. The fracture morphology was then observed, and simplified mechanical models of the woodceramics were discussed to explain the mechanical properties. The fracture was initiated at the cell walls that were located in vertical direction against the applied stress. The effect of impregnated phenol resin on the Young's modulus and the compressive strength was reasonably explained by a wall-bending model.     

Preparation and hierarchical porous structure of biomorphic woodceramics from sugarcane bagasse

Biomorphic woodceramics with controllable pore structure were prepared from sugarcane bagasse impregnated with epoxy resin followed by sintering at different temperatures. The phase composition, chemical composition, morphology and pore texture of the products were characterized by XRD, FTIR, SEM, mercury porosimetry and N₂ adsorption. The biomorphic woodceramics are typical non-graphitizable carbon and display a hierarchical porous structure from micrometer (0.6–21 μm) to nanometer scale (3.1–9.3 nm). The woodceramics retain the tubular structures of sugarcane bagasse before calcination at 1100 °C. Furthermore, an increase in the sintering temperature results in the decrease of BET surface area, average pore diameter and pore volume in the mesopore scale. This work provides a simple, economical, and environmentally friendly method for the production of hierarchical porous woodceramics. The final products have their potential applications as adsorbents, catalyst supports and filters.     

Laser Beam Machining of Porous Woodceramics

Laser beam machining was tested as a practical method for machining porous woodceramics (WCS). A black carbonized layer is generally formed on the processed surface when woody materials are processed with laser beam machining. This problem does not occur on the WCS because they are burned. The processed surface temperature during laser beam machining can be estimated from the relationship between the burning temperature and C and O₂ component concentrations. Burning (scorching) on the processed surface decreases slightly as the feed speed of the workpiece increases. WCS are more easily processed with laser machining after being burned, using pulse oscillation to reduce the thermal influence.     

Porous properties of activated carbon produced from Eucalyptus and Wattle wood by carbon dioxide activation

This work focused on the preparation of activated carbon from eucalyptus and wattle wood by physical activation with CO₂. The preparation process consisted of carbonization of the wood samples under the flow of N₂ at 400°C and 60 min followed by activating the derived chars with CO₂. The activation temperature was varied from 600 to 900°C and activation time from 60 to 300 min, giving char burn-off in the range of 20/2-83%. The effect of CO₂ concentration during activation was also studied. The porous properties of the resultant activated carbons were characterized based on the analysis of N2 adsorption isotherms at −196°C. Experimental results showed that surface area, micropore volume and total pore volume of the activated carbon increased with the increase in activation time and temperature with temperature exerting the larger effect. The activated carbons produced from eucalyptus and wattle wood had the BET surface area ranging from 460 to 1,490 m²/g and 430 to 1,030 m²/g, respectively. The optimum activation conditions that gave the maximum in surface area and total pore volume occurred at 900°C and 60 min for eucalyptus and 800°C and 300 min for wattle wood. Under the conditions tested, the obtained activated carbons were dominated with micropore structure (∼80% of total pore volume).     

The thermal conductivity of fir and beech wood heat treated at 170, 180, 190, 200, and 212°C

Heat treatment changes the chemical, physical, and mechanical properties of wood. The properties of heat‐treated wood have been researched considerably, but the thermal conductivity of heat‐treated wood in various conditions has not been reported. In this study, the thermal conductivity of heat‐treated fir and beech wood at temperatures 170, 180, 190, and 212°C for 2 h with ThermoWood method were investigated. The results were compared with industrially kiln‐dried reference samples. The results show that heat treatment caused an important reduction on thermal conductivity of wood, the extend of which is depend upon temperature and wood species. Considering all heat treating temperatures, generally by increasing heat treatment temperature the thermal conductivity of wood decreased. The effect of heat treating temperature on thermal conductivity was identical for fir and beech wood. The highest decrease in thermal conductivity occurred at 212°C for both wood species. When compared with untreated wood, the decreases in thermal conductivity at 170°C, and 212°C for fir and beech wood were 2%, 9 and 2%, 16% respectively. Depending on heat treatment temperature, the decrease found out beech in high temperature is higher than that of fir. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

植物基活性炭孔隙调控研究进展

植物基活性炭具有原料来源广泛、价格低廉、制备时间短、工艺成熟、所得产品比表面积大、孔隙结构发达、杂元素含量低、热稳定性和化学稳定性优良等特点,在环保领域的使用量逐年上升。本文系统介绍了植物原料热解过程中三大组分(纤维素、半纤维素和木质素)对所制得的炭化料及活化料孔隙结构的影响,对比总结了制备植物基活性炭常用的物理活化法、化学活化法(KOH活化法、H₃PO₄活化法和ZnCl₂活化法)、催化活化法和热解自活化过程中成孔反应机理以及形成的孔结构特点,指出研究工作中存在的问题,并提出了植物基活性炭孔隙调控未来的研究方向。     

PEEK: An excellent precursor for activated carbon production for high temperature application

A series of activated carbons (AC) with high apparent surface area and very high micropore volumes were prepared from granulated PEEK (poly[oxy-1,4-phenylene-oxy-1,4-phenylene-carbonyl-1,4-phenylene]) by physical activation with CO₂ at different temperatures and different activation times. The carbonisation yields at 873, 1073 and 1173 K were 57, 52 and 51%. As the activation temperature increased, between 873 and 1173 K, the burn-off, the micropore volume and mean pore size increased too. Those prepared at 1173 K, with 74% burn-off, present an extremely high apparent surface area (2874 m² g^− 1) and a very high micropore volume (1.27 cm³ g^− 1). The presence of pyrone groups, identified by FTIR, on the AC surface corroborates the prevalence of a basic point of zero charge, always higher than 9.2. The thermal stability was checked by thermogravimetric analysis and as the carbonisation temperature increased the thermal stability of the char increased too. All AC obtained from PEEK by physical activation at 1173 K are thermally resistant, as at 1073 K the loss of the initial mass was less than 15%. The collective results confirm that PEEK is an excellent precursor for preparing AC with a high carbonisation yield, a high micropore volume and apparent surface area and a very high resistance at elevated temperature.     

Activation of carbon nanofibres for hydrogen storage

The present study was aimed to investigate different methods of activation of carbon nanofibres, CNF, in order to determine the beneficial effect on the hydrogen sorption capacities of increasing the surface area. Two activation systems were used: physical activation with CO₂ and chemical activation with KOH. A range of potential adsorbents were thus prepared by varying the temperature and time of activation. The structure of the CNF proved more suitable to activation by KOH than by CO₂, with the former yielding higher surface area carbons (up to 1000 m² g⁻¹). The increased surface area, however, did not correspond directly with a proportional increase in hydrogen adsorption capacity. Although high surface areas are important for hydrogen storage by adsorption on solids, it would appear that it is essential that not only the physical, but also the chemical, properties of the adsorbents have to be considered in the quest for carbon based materials, with high hydrogen storage capacities.     

Effectiveness of functionalized polyolefins as compatibilizers for polyethylene/wood flour composites

The effects of various types of compatibilizers on the mechanical properties of high‐density polyethylene/wood flour (HDPE/WF) composite were investigated. Functionalized polyolefins such as maleated and acrylic acid grafted polyethylenes, maleated polypropylene (PPgMA) and styrene‐ethylene/butylene‐styrene triblock copolymer (SEBSgMA) were incorporated to reduce the interfacial tension between the polyethylene matrix and the wood filler. Among them, it was found that maleated linear low‐density polyethylene (LLDPEgMA) gave maximum tensile and impact strength of the composites, presumably because of better compatibility with the HDPE matrix. Similar but less enhanced improvements in the mechanical properties, depending on the compatibilizer loading, were seen for the SEBSgMA system. Whereas acrylic acid grafted high‐density polyethylene (HDPEgAA) and maleated polypropylene (PPgMA) only slightly improved tensile modulus and tensile strength; and they both increased with increasing loadings of compatibilizers. A scanning electron microscopic study was employed to reveal the interfacial region and confirm these findings. In addition, dynamical mechanical thermal measurements also revealed the interaction between filler and matrix, and FTIR spectroscopy was used to assign the chemical fixation and the various chemical species involved at the surface of the wood fillers before and after surface treatment.     

Friction and Wear of Woodceramics under Oil and Water Lubricated Sliding Contacts

Friction and wear properties of woodceramics were evaluated under oil and water lubricated sliding contacts. The experiment was conducted with a block on a ring wear tester. The block material was woodceramics (MDF-800) and and the ring was a forging steel (SF55). The sliding velocity and the load were varied in the ranges 1.0–19.0 m/s and 98–294 N, respectively. The ring temperature was measured using a thermocouple located at 1.0 mm below the frictional surface of the ring.In the oil lubrication, the coefficient of friction was small and constant at 0.12, irrespective of the sliding velocity. The specific wear rate of the woodceramics was also small and was in the range 5 × 10–7–2 × 10–6 mm3/Nm. With the increase in the load, the coefficient of friction and the specific wear rate of woodceramics decreased. It was found that low friction and low wear could be maintained at least until a ring temperature of 160°C.In the water lubrication, the coefficient of friction was small and constant at 0.16 until the sliding velocity of 12 m/s. The specific wear rate was also small and was in the range 3 × 10–7–2 × 10–6 mm3/Nm. As the sliding velocity increased further and the ring temperature became high, friction and wear increased.     

Porous carbon materials produced by the chemical activation of birch wood

It was established that the main factors responsible for the yield and specific surface area of porous carbon materials obtained by the chemical activation of the wood of birch are the nature of a modifying agent and the temperature of pyrolysis. The additional opening of the porous structure of the product of the chemical activation of wood occurs at the stage of its water treatment as a result of the removal of water-soluble compounds. The conditions of the carbonization of birch wood modified with H₃PO₄, KOH, and ZnCl₂ were chosen in order to provide the significant development of the porous structure of carbon materials. The porous carbon material with the highest specific surface area (more than 2560 m²/g) was obtained by the water washing of the product of the carbonization of birch wood modified H₃PO₄ at 400°C.     

木陶瓷的研究进展

介绍了木陶瓷从选料到机械加工的制备工艺,特别对碳木材陶瓷、氧化物木陶瓷、SiC木陶瓷的制备作了较为详尽的阐述,并且对碳木材陶瓷的一些特性也作了归纳.最后对木陶瓷的开发和环保意义进行了评述.     

Influence of the zeolite type on the mechanical–thermal properties and volatile organic compound emissions of natural‐flour‐filled polypropylene hybrid composites

The physicomechanical properties, thermal properties, odor, and volatile organic compound (VOC) emissions of natural‐flour‐filled polypropylene (PP) composites were investigated as a function of the zeolite type and content. The surface area and pore structure of the natural and synthetic zeolites were determined by surface area analysis and scanning electron microscopy, respectively. With increasing natural and synthetic zeolite content, the tensile and flexural strengths of the hybrid composites were not significantly changed, whereas the water absorption was slightly increased. The thermal stability and degradation temperature of the hybrid composites were slightly increased with increasing natural and synthetic zeolite content. At natural and synthetic zeolite contents of 3%, the various odors and VOC emissions of the polypropylene/rice husk flour and polypropylene/wood flour hybrid composites were significantly reduced because of the absorption of the odor and VOC materials in the pore structures of the natural and synthetic zeolites. These results suggest that the addition of natural and synthetic zeolites to natural‐flour‐filled thermoplastic polymer composites is an effective method of reducing their odor and VOC emissions without any degradation of their mechanical and thermal properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

中间相沥青微球的活化

用KOH为活化剂,在不同活化条件下对中间相青微球进行活化,制备出比表面积为3182m^2/g,总孔容为2．45mL/g,苯吸附值为1320mg/g的高比表面积活性炭微球。研究了了KOH配比、活性温度和活化时间对活性炭微球的收率、比表面积和苯吸附值的影响。研究表明：随着KOH配比量或活化温度的提高,活化收率下降,活性炭微球的比表面积和七吸附值升高到一定值后下降;延长活化时间使活化反应进行完全,活性炭微球的活化收率、比表面积和苯吸附值仅有轻微变化。