木基电磁屏蔽/吸波材料研究进展

生命健康、精密仪器和国防信息等领域对电磁屏蔽/吸波材料均有迫切的需求,但传统金属基电磁屏蔽/吸波材料存在屏蔽效能质量比低、易造成二次环境污染和屏蔽机理单一等不足,而新型碳基纳米电磁屏蔽/吸波材料制备烦琐、价格昂贵。木材及其衍生品具有多级孔结构、强重比高、绿色低碳、易加工、可再生等天然优势,开发轻质、环境友好的木基电磁屏蔽/吸波材料逐渐成为研究热点。系统分析和讨论了国内外木基电磁屏蔽/吸波材料的研究进展,介绍了电磁屏蔽材料的基本概念和原理,对比了涂层型、填充型、碳化型3种制备方法的特点及适用范围,总结了制备工艺、孔隙结构、导电/磁性填充组分等因素对电磁屏蔽和吸波性能的影响,并分析了木基电磁屏蔽/吸波材料中的电磁屏蔽机理和吸波机制,以及木质材料的各向异性结构对屏蔽性能的调控机制,最后对木基电磁屏蔽/吸波材料的未来发展趋势和研究重点进行了展望,可为木基电磁屏蔽/吸波材料的研发提供一定参考。     

木基复合材料研究现状

木基复合材料具有良好的机械性能和可加工性，是现阶段我国木材科学与技术领域开发和研究的主要对象。首先根据不同的组合形式和应用总结出3种木基复合材料，即木塑复合材料、木基陶瓷材料和木材无机纳米复合材料。同时，梳理了其在生物可降解材料、新型环保材料、新型阻燃材料、生物基热塑性等领域的研究进展，并针对现有木基复合材料制备和应用方面存在的问题，展望其研究趋势和应用前景，旨在为进一步提高木基复合材料的研究提供科学依据。     

木基发光材料研究进展

随着资源的消耗以及人类可持续性发展意识的增强,木材等绿色资源的功能化改性及应用日益受到人们关注。木基发光材料综合了木基复合材料和发光材料的优势,以木材为载体,通过浸渍发光材料获得具有发光性能的功能性木材,其在一定程度上保留了木材的基本结构特征,并改善了木材的尺寸稳定性、防腐防潮性和力学性能等,还可以通过添加其他功能性材料开发磁性、储能等新功能。文中从制备木基发光材料所需的原辅材料、功能性添加剂等方面综述目前国内外木基发光材料的相关研究成果,主要对其所使用的发光材料进行分类,分析总结各研究成果的制备工艺包括对木材的不同预处理方式等;同时对木基发光材料在照明装饰、储能材料等领域的应用前景进行展望;并从材料、工艺和功能性添加剂等方面提出一些深入研究的建议,旨在进一步提升木基发光材料的性能,为其在家居、储能、照明等领域得到更广泛的应用提供思路。     

木基相变蓄热材料研究进展

相变蓄热材料有助于节能和能源的可持续利用,缓解能源危机。木材虽具有调节温度的功能,但远未达到作为相变蓄热材料的要求,因此通常需要与其他相变材料进行复合制备木基相变蓄热材料。文中介绍了几种常与木材复合的相变材料（石蜡、聚乙二醇、脂肪酸）,并对这些材料的特性和应用范围进行了比较;在此基础上概述了木基相变蓄热材料的研究现状,包括实木相变蓄热材料、木质复合相变蓄热材料和木塑相变蓄热材料,并阐述了各类材料的制备方法、性能特点和应用领域;对木基蓄热相变材料未来研究方向进行了展望。     

聚合法制备木基聚苯胺半导体薄木的主要特性

通过对木质单板真空浸渍苯胺单体,然后使其在氧化剂和不同浓度的掺杂剂磷酸的作用下发生原位聚合反应而制备成木基聚苯胺半导体材料,此复合材料既具有聚苯胺的导电性,又具有木质材料的天然特征。光学电镜和扫描电镜显示,聚苯胺均匀地分散在木质基材中。木材的质量增加率和体积膨胀率分别为16.13%和6.21%,而且吸水率显著降低。傅里叶变换红外光谱显示苯胺单体在木质基材中发生了原位聚合反应,而且氨基与木材的羟基发生了接枝反应,与木材基质形成了紧密的界面结合。X-射线衍射分析发现,木质纤维素晶区的晶格并未遭到破坏,而木质纤维素的相对结晶度有所增加。通过改变掺杂剂的浓度,木基聚苯胺复合材料的电导率可达2.57×10-5~9.23×10-3S/cm,完全符合制备电磁屏蔽材料的电导率要求。     

先驱体转化法制备ZrC木质陶瓷及其性能分析

以松木为原料,经炭化制得松木炭,以有机锆聚合物(PZC)为先驱体浸渍松木炭后进一步高温热处理制备得到ZrC木质陶瓷。采用XRD、SEM、FT-IR、TG-DSC分别对样品的物相变化、组成和微观结构进行了表征,研究了热处理温度和杂化材料质量增加率对木质陶瓷显气孔率与力学性能的影响。结果表明:有机锆先驱体裂解过程中生成ZrO_2,进一步可以在1 400℃通过碳热还原反应转化为ZrC相。ZrC木质陶瓷由立方相ZrC和无定形碳组成,生成的木质陶瓷较好地保留了松木模板的管状孔洞结构,部分ZrC相沉积在孔洞内部。木质陶瓷材料显气孔率随着热处理温度的升高而升高,随质量增加率的增加而降低;力学性能随热处理温度和质量增加率的增加而提高,质量增加率为278%的杂化材料在热处理温度为1 400℃时制备的ZrC木质陶瓷具有良好的力学性能,弯曲强度和断裂韧性分别为158 MPa和1.8 MPa·m~(1/2)。     

木基电热材料电热性能分析及板面温度模拟

为了提高木质材料的导热性能,获得一种板面温度分布均匀、节能降耗的地面采暖材料,选取木质材料为基材,碳素材料为导热材料,采用碳纳米技术和人造板技术相结合的工艺制备木基电热材料,并对其电热性能和板面温度进行分析和模拟。研究分析了碳素材料的涂覆形式、功率对木基电热材料的电热性能和板面温度的影响,并借助fluent软件模拟木基电热材料板面温度均匀性以及板面升温的情况,并对模拟数据与实测数据进行了对比分析。结果表明:在相同功率情况下,不同涂覆形式碳素材料发热情况不相同,碳素材料S型涂覆的电热材料发热性能最好,板面温度分布较均匀;不同功率情况下,通电15 min左右材料表面温度均达到35℃以上,所以优选碳素材料S型涂覆形式作为电热材料的内置发热层形式。在此基础上,采用Fluent软件对木基电热材料板面的升温过程的动态仿真进行了模拟,且模拟仿真结果与试验测试数据差值百分比在5%以内,所以仿真模型是有效的。     

木陶瓷的开发应用

木陶瓷（WOOD CERAMIC）是木材、木质材料或制成的复合材料在无氧状态下，经高温慢速炭化处理得到的炭化物，它具有炭固有的质轻、吸附性强又具有陶瓷般的高硬度、高耐热性、高耐蚀性等。通过对木陶瓷制造工艺及应用的介绍，为开发多功能的科技产品提供了新途径。     

基于SolidWorks的木基陶瓷模具CAD软件开发

基于SolidWorks的参数化设计思维,针对木基陶瓷材料模压成形特点,开发出木基陶瓷模压成形模具CAD软件;在阐述该软件总体结构与关键开发技术的同时,给出软件的运行实例.     

木基衍生炭活化过硫酸盐降解污水污染物的研究进展

基于硫酸根自由基的高级氧化技术在处理水中有机污染物领域受到广泛关注,利用炭材料活化过硫酸盐可解决传统过渡金属/过硫酸盐体系降解污染物过程中的金属离子溢出问题。木基衍生炭是一种天然绿色、成本低廉、制备工艺简单、可持续的非金属炭材料催化剂,并且具有应用于环境修复领域的潜能。木基前驱体经热解后可生成具备发达孔结构和丰富官能团的炭材料,有利于过硫酸盐活化。木基衍生炭具有的丰富孔径结构也为水体中有机污染物的吸附提供了可能。概述了近年来木基衍生炭/过硫酸盐体系在污水处理领域的研究进展,重点介绍了自由基高级氧化技术原理、木基衍生炭材料的制备技术与性能特点以及基于炭材料的自由基高级氧化作用机制和技术特点,同时详细总结了非金属杂原子改性对木基衍生炭材料性质及其活化过硫酸盐能力的影响,归纳分析了木基衍生炭催化剂在水环境处理中的作用机制与应用前景。研究结果也为森林可燃物处理、木材加工剩余物及废弃改性木材的高值化利用提供了新的思路。     

杉木基木材陶瓷的结构及表征

用杉木纤维(木粉)/PF树脂复合材料高温烧结制备杉木基木材陶瓷。XRD分析表明:当烧结温度升高,杉木基木材陶瓷的(002)晶面的Bragg衍射角右移,d_(002)值减小,g值增大,可石墨化程度增加;SEM分析显示:木材陶瓷的结构与PF树脂的含量和杉木纤维(木粉)的结构及分布情况有关,树脂含量的增加有助于木材陶瓷形成三维网状结构;杉木纤维(木粉)作为天然植物模板而存在,且保持着其自然形态,使木材陶瓷成为一种植物纤维生态陶瓷。     

Preparation and crosslinking of oligoesterified woods based on maleic anhydride and allyl glycidyl ether

Summary Oligoesterification of wood was investigated by alternately adding esterification reactions of wood with maleic anhydride and allyl glycidyl ether. The products obtained consisted of acetone-insoluble and soluble parts. The insoluble parts were novel oligoesterified woods with oligoester chains having polymerizable double bonds. The oligoester chain length showed a tendency to decrease with increase in wood content in feed. The soluble parts were free oligoesters which were not linked with the wood matrix. The products (the oligoesterified wood-containing mixtures), when subjected to hot-pressing in the presence of a peroxide, gave plasticized crosslinked wood boards whose surfaces are smooth, glossy, and plasticlike. In this case, the free oligoesters which were hardening worked as a plasticizer for the wood components and were combined, by the crosslinking, with the oligoesterified woods, resulting in the formation of the network structure. The crosslinked wood boards exhibited outstanding properties in heat distortion temperature (>165°C) and compressive strength (ca. 1,600–2,300 kg/cm²).     

Method for measuring viscoelastic properties of wood under high temperature and high pressure steam conditions

A method for measuring the viscoelastic properties of wood under high temperature and high pressure steam was developed using a testing machine with a built-in autoclave. A newly developed load cell capable of resisting a steam pressure of 16kgf/cm² and a temperature of 200°C was installed in the autoclave. This load cell could be used to determine precisely the loads while steaming at temperatures from 100°C to 200°C. In addition to load-detection problems, it was necessary to avoid the nonuniform thermal degradation of wood during the measurement process under steaming at high temperatures. This nonuniform degradation could be minimized by shortening the time required for the wood to attain thermal equilibrium using specimens conditioned to the fiber saturation point. According to this method, a stress relaxation curve for sugi (Cryptomeria japonica D. Don) wood being compressed while steaming at 180°C was obtained. The stress was seen to decrease rapidly with time, reaching almost zero at 3000s.     

预压缩处理施胶技术提高杨木重组木尺寸稳定性的研究

高性能重组木制造技术可将速生材制造成具有高强度和天然木材纹理结构的新型木材,从而提高速生材的附加值。然而,采用此技术制备的重组木虽然尺寸稳定性显著高于传统工艺制备的重组木,但是仍不能满足室外用材的需求。为提高室外用重组木的尺寸稳定性,采用预压缩处理施胶技术对木单板施胶后制备高性能重组木,通过扫描电镜、压汞仪、激光共聚焦显微镜和超景深显微镜,研究了预压缩处理施胶技术对木单板和重组木的形貌和胶液分布的影响,及其对重组木尺寸稳定性和力学性能的影响。研究结果表明:预压缩处理施胶技术增大了木单板的比表面积,使胶液在单板和重组木中分布更均匀,而且显著降低了重组木的吸水厚度膨胀率(TSR)和吸水宽度膨胀率(WSR)。在63℃/24 h的水煮测试中,TSR和WSR相比未处理材分别降低43.34%和12.82%;在28 h循环测试中,TSR和WSR相比未处理材分别降低50.94%和51.48%。因此,采用预压缩处理施胶技术制备的重组木尺寸稳定性相比未处理材显著提高。同时,重组木的静曲强度、弹性模量和剪切强度相比未处理材分别提高1.63%,12.15%和21.34%。     

Effect of steam pretreatment on wood moisture content and characteristics of vacuum drying

The effects of high temperature steam pretreatment on the change in wood moisture content (MC) and characteristics of vacuum drying were investigated in this study. Poplar and manchurian walnut woods were pretreated with high temperature steam at 100°C and 140°C, prior to vacuum drying. A comparison of the characteristics of vacuum drying between steam pretreated wood and untreated wood was carried out. The results show that during steam pretreatment, the MC of wood decreased within a few hours. The reduction of MC varied with the temperature; the higher the temperature, the faster the MC dropped. During the vacuum drying stage, the rates of drying of pretreated samples were higher than those of untreated samples when MC was below the fiber saturation point. Furthermore, the total drying time of samples treated at a steam temperature of 140°C was lower than that of untreated samples. Therefore, a vacuum procedure after steam pretreatment can effectively shorten the drying time when drying wood.     

工业木质素用于制造木陶瓷

以工业木质素为原料制造新型多孔炭材料木陶瓷,并对产品得率、强度及微观结构形态进行了研究。结果表明,随着酚醛树脂用量的增加,木质素陶瓷的质量得率和体积得率略有增加,抗弯强度大大提高,抗压强度也提高明显。当木质素与酚醛树脂质量比为1．33∶1时,木质素陶瓷的抗弯强度为1．88MPa,抗压强度达3．86kN/cm~2。微观结构分析表明,在木质素—酚醛树脂复合板中有团块状木质素夹杂出现,高温烧结后样品孔隙结构增多。高温烧结前后样品的比表面积分别为0．2448m~2/g和0．9742m~2/g。     

Vapor phase reaction of wood with maleic anhydride (I): dimensional stability and durability of treated wood

Reaction between maleic anhydride (MA) and wood specimens was carried out in a vapor phase reaction system. Reaction conditions such as the ratio of supplied MA to wood, initial moisture content, and reaction temperature were optimized. The MA supplied to the reaction system was effectively absorbed by the wood, and a satisfactorily high dimensional stability was achieved even at a low MA/wood ratio. The dimensional stability increased with rising initial moisture content. When the reaction was conducted at an elevated temperature (180°C), high dimensional stability was attained without remarkable weight increase and bulking. The mechanism of dimensional stabilization was discussed on the basis of the dimensional changes at high humidity and during repeated water soaking and drying. It was shown that the dimensional stabilization arises mainly from a decrease of hygroscopicity. When the reaction was conducted at 180°C, the formation of cross-links in the cell wall was apparent. Following the MA treatment, the antifungal property was remarkably enhanced and met the Japanese Industrial Standard K1571. Therefore, MA treatment in the vapor phase is an effective method to attain antifungal properties as well as high dimensional stability with a small amount of nontoxic reagent.     

High-temperature mechanical properties and thermal recovery of balsa wood

This article presents an experimental study into thermal softening and thermal recovery of the compression strength properties of structural balsa wood (Ochroma pyramidale). Balsa is a core material used in sandwich composite structures for applications where fire is an ever-present risk, such as ships and buildings. This article investigates the thermal softening response of balsa with increasing temperature, and the thermal recovery behavior when softened balsa is cooled following heating. Exposure to elevated temperatures was limited to a short time (15 min), representative of a fire or postfire scenario. The compression strength of balsa decreased progressively with increasing temperature from 20° to 250°C. The degradation rates in the strength properties over this temperature range were similar in the axial and radial directions of the balsa grains. Thermogravimetric analysis revealed only small mass losses (<2%) in this temperature range. Environmental scanning electron microscopy showed minor physical changes to the wood grain structure from 190° to 250°C, with holes beginning to form in the cell wall at 250°C. The reduction in compression properties is attributed mostly to thermal viscous softening of the hemicellulose and lignin in the cell walls. Post-heating tests revealed that thermal softening up to 250°C is fully reversible when balsa is cooled to room temperature. When balsa is heated to 250°C or higher, the post-heating strength properties are reduced significantly by decomposition processes of all wood constituents, which irreversibly degrade the wood microstructure. This study revealed that the balsa core in sandwich composite structures must remain below 200°–250°C when exposed to fire to avoid permanent heat damage.     

An investigation on the transition characteristics of the wood cell walls during carbonization

The structural changes of the cell wall and crystalline cellulose of Quercus variabilis wood in a pyrolysis system at several temperatures ranging from 250 to 500°C were investigated to examine the wood carbonization characteristics. The volume of the wood sample was decreased and the weight loss was increased by increasing the carbonization temperature. Vessels collapsed severely in tangential direction during the charring process above 350°C. SEM observation indicated that the layering structure of the walls in wood fibers and parenchyma cells were retained below 300°C. However, the cell walls above 350°C changed to an amorphous-like structure without cell wall layering. X-ray diffraction confirmed that the cellulose crystalline substance was still remained at the carbonization temperature of 300°C but was not detected above 350°C. It can be concluded that the transition from Q. variabilis wood to charcoal might occur at approximately 350°C.