CVD碳化硅薄膜对炭纤维表面结构和性能的影响

以三氯甲基硅烷(CH3SiCl3,MTS)为碳化硅源,采用化学气相沉积(CVD)的方法,在去胶炭纤维表面沉积一层碳化硅薄膜。采用SEM及N2等温吸附观察的方法,分析了薄膜处理对炭纤维表面结构的影响。结果表明:CVD碳化硅薄膜能够修复炭纤维表面的微孔和裂纹等缺陷,使纤维表面更光滑,可以改变纤维的表面结构特性,使炭纤维的BET比表面积和BJH累积孔体积降低,从而降低炭纤维表面吸附能力。采用单丝拉伸试验机进行力学分析,通过干烧对比实验发现:在CVD过程中,考虑沉积气氛对纤维损伤的影响,炭纤维在CVD碳化硅薄膜修复后,抗拉强度和弹性模量分别提高了6.7%和8.2%。     

采用在SiC毡上CVD—SiC涂层提高C／C复合材料抗氧化性能

最近发展起来的SiC纤维复合涂层，也就是SiC/SiC层与化学气相沉积（CVD）SiC结合形成复合涂层，已能够在高温下提高C／C复合材料的抗氧化性。形成的SiC纤维复合涂层约300μm厚，生产时先将SiC毡覆盖在3D－C／C基体材料上，然后浸渍一种碳粉与硅粉均匀分散的料浆进行化学气要沉积。通过化学气相沉积（CVD）过程，在复合材料上形成致密的涂层。在CO2－H2O－N2组成的混合气体（CO2 9％、N273％、H2O18％），1700℃下进行5h氧化实验，结果发现有SiC毡增强复合涂层比没有SiC毡增强复合材料失重率低。SiC纤维毡复合涂层由双层结构组成，里层是多气孔的SiC/SiC纤维层，外层为致密的SiC涂层。由于SiC/SiC纤维层热膨胀系数介于C／C复合基体材料与CVD－SiC涂层之间，因此，SiC/SiC中间层在复合材料中起了重要作用，从而由于热膨胀系数不同产生的热应力致使涂层开裂降低到最低程度。涂层试样氧化后，采用缓冲冲床（MSP）测试其残余强度。MSP测试结果表明氧化后C／C复合材料强度值呈发散性，从纤维折断面看有z轴方向分布纤维存在。然而，这种方法仅适用于测试小尺寸试样。从这篇论文中，可看出涂层后的C／C复合材料有高的抗氧化性，其氧化后仍能保持高的残余强度。     

射频法涂层碳纤维的高温氧化性

国内外为提高碳纤维的高温氧化性，采用化学气相沉积法在碳纤维表面涂覆抗氧化涂层技术已广泛应用。本文采用低温射频法对碳纤维涂覆碳化硅涂层，并对涂层碳纤维进行800℃高温抗氧化性研究。热重分析发现，此种涂层碳纤维具有一定的抗氧化性，其氧化失重与时间和温度呈现抛物线规律变化。利用电子探针及透射电镜研究发现，涂层的表面致密化程度和界面结合情况是影响其抗氧化性的关键因素。     

稀释气体对化学气相沉积SiC涂层生长行为的影响

以CH3SiCl3-H2为反应气体,采用Ar和H2作为稀释气体。在1100℃、负压条件下,由化学气相沉积制备了SiC涂层,研究了稀释气体对涂层沉积速率、形貌以及晶体结构的影响。以Ar为稀释气体时,随着稀释气体流量的增加沉积速率迅速减小;用Ar作稀释气体制备的SiC涂层相对粗糙,随着Ar流量的增加,晶粒簇之间的空隙较大,涂层变得疏松。XRD分析表明：当稀释气体Ar流量超过200ml／min时,涂层中除了β-SiC外,还逐渐出现了少量的α-SiC。以H2为稀释气体时,当H2流量增加到400ml／min时,涂层的沉积速率迅速增大;以H2为稀释气体制备的SiC涂层致密、光滑,沉积的SiC涂层全部是β-SiC,且具有非常强的(111)晶面取向,涂层中无α-SiC出现。     

钴催化剂制备螺旋纳米炭纤维

以纳米钴粉为催化剂,采用化学气相沉积法制备了纳米螺旋炭纤维。重点探讨了气相沉积温度、碳源气体流量、气相沉积时间等参数对螺旋炭纤维形貌的影响。用SEM、XRD、拉曼光谱等对螺旋炭纤维的微观形貌和物相组成等进行表征。结果表明,随温度的升高,产品石墨化程度加剧,但会出现无定形碳等杂质,纤维直径变粗。气相沉积时间对纳米螺旋炭纤维直径有较大影响,适当的气相沉积时间是生成光滑螺旋纳米炭纤维的前提。在500℃,通入80 mL/min的乙炔,反应40 min,可获得纤维直径50~100 nm、表面光滑的纳米螺旋炭纤维。     

由化学改性粘胶丝快速制备连续炭纤维新工艺的研究

采用了一种新的高效化学改性法和相应的烧结工艺，可在较低温度下快速制得性能优良的连续化粘胶基炭纤维。对化学改性剂中混合多元胺、表面活性剂的作用作了探讨．对气氛、升温速率等工艺参数的影响作了研究。通过正交优化设计制定出合理的连续绕结工艺。此法可使纤维经约6小时处理后．1000℃时形成强度为1.8GPa，模量为75GPa的炭纤维。     

炭纤维表面原位反应制备TaC涂层及其形成机理研究

以金属钽粉为钽源,采用原位反应法在炭纤维表面成功制备出连续的TaC涂层,研究了涂层炭纤维的相组成、微观形貌和抗氧化性能,并探究了炭纤维表面连续TaC涂层的形成机理。结果表明,在温度为1000~1400℃时能在炭纤维表面制备出TaC涂层,反应温度和时间显著影响涂层厚度以及涂层与炭纤维基体的结合性能;反应温度为1200℃时制备的涂层均匀致密,与炭纤维基体结合较好,涂覆TaC涂层后炭纤维的起始氧化温度提高了200℃。从动力学角度分析了TaC涂层的生长机理,结果表明Ta原子沿炭纤维轴向发生表面扩散,Ta原子的表面扩散行为是连续TaC涂层形成的关键因素。     

YSZ涂覆碳纤维/环氧复合材料性能的研究

采用溶胶-凝胶法在碳纤维的表面涂覆了一层钇稳定氧化锆(YSZ)涂层，并研究了用其制备的碳纤维／环氧复合材料的性能。结果表明：涂层中粒子的粒经约为10nm，YSZ涂覆后复合材料的层间剪切强度(ILSS)、拉伸强度和弯曲强度分别提高了52．0％、6．5％和6．3％；YSZ涂覆后的碳纤维与环氧树脂基体的结合更加紧密，且在碳纤维表面形成的YSZ涂层在450～700℃能有效地减缓碳纤维／环氧复合材料的氧化失重速率。     

石墨表面CVD氮化硅涂层的制备与抗氧化研究

采用化学气相沉积法，以SiCl₄-NH₃-H₂为先驱体气体和载气，在等静压石墨表面制备了氮化硅涂层，沉积温度900～1 300℃,沉积压力1 000 Pa,并在600～1 000℃进行了空气气氛静态氧化实验。X射线衍射结果表明，900℃和1 100℃沉积的氮化硅为非结晶态，1 300℃沉积的为结晶的α-Si₃N₄。氧化增重结果表明，900～1 300℃沉积的涂层，对石墨氧化均有明显的防护作用，其中，1 100℃涂层防护效果最好，900℃涂层防护效果最差。采用SEM对氧化前后的涂层表面进行了观察，900℃涂层在800℃或更高温度的空气气氛中发生了明显的氧化现象；1 100℃和1 300℃涂层即使在1 000℃下也未发生明显的氧化现象。基底的氧化由涂层开裂导致，且α-Si₃N₄结晶涂层开裂更显著。     

空气氧化刻蚀提高PAN基炭纤维抗拉强度的研究

用空气氧化刻蚀（附浸渍预处理）的方法对通用级（类似T－300）PAN基炭纤维进行处理。以NaOH,HNO3,H2SO4,(H2SO4 KMnO4)为浸渍液，研究了直接空气氧化刻蚀中的氧化温度，氧化时间，浸渍液浓度等因素对炭纤维抗拉强度的影响。结果表明：在优化工艺条件下，炭纤维的抗拉强度可由3．73GPa提高到4．52GPa。     

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。