炭纤维/环氧树脂结构吸波材料电磁特性研究

采用真空CVD炉分别在600,630,660℃对炭纤维进行了热处理,制备了3种不同的炭纤维,然后制备出炭纤维/环氧树脂结构吸波复合材料,最后采用波导法对材料的电磁特性进行了测试,并对其吸波性能进行了模拟。结果表明:炭纤维的热处理温度对材料的介电常数有较大影响。从实验中得出,通过控制炭纤维的热处理温度,可有效地调节炭纤维的介电常数,从而制备出具有良好的吸波性能的结构吸波材料。     

炭纤维吸波复合材料结构设计的研究进展

总结了炭纤维吸波性能的电磁改性方法,重点介绍了结构设计对炭纤维吸波复合材料吸波性能的影响,包括短切炭纤维、炭纤维排布结构、炭纤维电路模拟结构以及含炭纤维的混杂纤维排布对炭纤维复合材料吸波性能的影响.提出了炭纤维吸波复合材料今后的研究方向.     

微螺旋炭纤维的微波电磁参数及其环氧复合材料的吸波性能研究

采用化学气相沉积法制备了微螺旋炭纤维(CMCs),研究了其在频率为8.2￣12.4GHz范围内的微波介电特性;以环氧树脂为胶粘剂制备了CMCs/环氧复合吸波涂层,并对其吸波性能进行了研究。结果表明,随着CMCs含量的增加,复介电参数实部ε′、虚部ε″和介电损耗tanδ均有所增加,当CMCs含量为1%￣5%时,ε″和tanδ增幅很小;当CMCs含量为10%时,两者增幅显著增大。ε′表现出高频减小的趋势,同时tanδ表现出高频增大的趋势,这些均有利于实现高频吸波。磁损耗tanξ较小且CMCs含量对其影响不明显。CMCs/环氧复合吸波涂层的反射率随着CMCs含量的增加而明显减小,表现出高频衰减略有增加的趋势,同时出现多吸收峰,这有利于实现宽频吸波。     

吸波材料结构、性能及应用研究进展

综述了碳系吸波材料、导电高聚物、手性吸波材料、席夫碱类吸波材料等吸波材料的最新研究应用现状,并展望了吸波材料未来发展趋势。碳纳米管/石墨烯等新型碳系吸波材料结合了炭材料和纳米材料的良好的导电性能和质量轻等优点,具有优异的吸波性能;导电高聚物吸波材料具有较强的可设计性和较低的密度,使得其成为一类具有较大发展潜力的新型吸波材料;手性吸波材料具有手性参数可调、吸波频带宽等优点,通过调整手性参数,可以实现有针对性的微波吸收;席夫碱类吸波材料可通过设计合成长链共轭结构的席夫碱及其金属络合物、引进手性螺旋结构等来提高席夫碱吸波材料的吸波性能。由于吸波材料的性能是影响雷达隐身的关键因素,而传统的吸波材料存在吸收频带窄、吸收强度弱及密度大等问题,新型吸波材料的研究应用成为当前功能材料领域的热点之一。     

吸波材料结构、性能及应用研究进展

综述了碳系吸波材料、导电高聚物、手性吸波材料、席夫碱类吸波材料等吸波材料的最新研究应用现状,并展望了吸波材料未来发展趋势。碳纳米管/石墨烯等新型碳系吸波材料结合了炭材料和纳米材料的良好的导电性能和质量轻等优点,具有优异的吸波性能;导电高聚物吸波材料具有较强的可设计性和较低的密度,使得其成为一类具有较大发展潜力的新型吸波材料;手性吸波材料具有手性参数可调、吸波频带宽等优点,通过调整手性参数,可以实现有针对性的微波吸收;席夫碱类吸波材料可通过设计合成长链共轭结构的席夫碱及其金属络合物、引进手性螺旋结构等来提高席夫碱吸波材料的吸波性能。由于吸波材料的性能是影响雷达隐身的关键因素,而传统的吸波材料存在吸收频带窄、吸收强度弱及密度大等问题,新型吸波材料的研究应用成为当前功能材料领域的热点之一。     

螺旋炭纤维的研究进展

螺旋炭纤维具有优异的物理和化学特性，在电磁波吸波材料、氢气存储等领域极具应用价值。本文综述了螺旋炭纤维的现状与发展，包括螺旋炭纤维的制备、微观形貌、生长机理、性能与应用，并讨论了有关螺旋炭纤维存在的一些问题。     

添加MWCNTs的结构吸波材料的制备及其性能研究

采用炭纤维、玻璃纤维、环氧树脂和纳米碳管制备了结构吸波材料。通过实验和理论计算研究了MWCNTs含量对单层结构吸波材料的吸波性能的影响和层间排列方式对双层结构吸波材料吸收性能的影响。对于单层的结构吸波材料,当MWC-NTs的含量为9%时吸波效果最佳,吸收率超过-10dB的有效带宽为5.4GHz;对于双层结构吸波材料,当层间排列为MWCNTs15%MWCNTs3%时,最大吸收率为-39.3dB、吸收率超过-10dB的有效带宽为6.5GHz,涵盖了整个Ku频率范围(12～18GHz),更能满足"强、宽、薄"的要求。     

纳米吸波材料的研究现状与发展趋势

评述了纳米吸波材料的特性及吸波原理,介绍了纳米铁氧体吸波材料、纳米金属吸波材料、纳米陶瓷吸波材料、纳米导电高分子吸波复合材料、碳纳米管吸波材料、纳米复合吸波材料研究现状及发展情况,指出了纳米复合吸波材料是未来纳米吸波材料的研究重点。     

结构型吸波复合材料的研究进展

结构型吸波复合材料具有吸波性能好、质量轻、可承载等优点,已成为当代吸波材料的主要发展方向,对隐身材料的设计和制造有着重要意义。本文从纤维增强体的截面形状和制备工艺、纤维的铺排结构和夹层复合结构、吸波剂改性等影响吸波复合材料吸波性能的主要因素出发,系统地总结了结构型吸波复合材料的最新研究热点和成果,并指出吸波复合材料的未来发展方向。     

微纳米吸波材料研究现状

介绍了微纳米吸波材料的吸波机理,叙述了铁氧体吸波材料、金属微粉吸波材料、多晶铁纤维吸波材料等常用吸波材料的特点与研究进展;着重分析了纳米材料的特点以及其作为吸波材料的独特性能,并简要介绍了具有独特性能的左手材料以及碳纳米管作为吸波材料的研究现状,在此基础上对吸波材料的研究前景进行展望.     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。