功能性连续碳化硅自由薄膜可量产

<正>厦门大学材料学院突破了具有光电特性的连续碳化硅(SiC)自由薄膜关键技术,制备出多种组分PCS先驱体,掌握了连续SiC自由薄膜不熔化交联预处理与高温裂解烧结     

由聚碳硅烷纤维通过化学气相交联法制备低氧含量碳化硅纤维

以环己烯和1-己炔作为反应气氛,对聚碳硅烷(polycarbosilane,PCS)纤维进行化学气相交联不熔化处理,研究不熔化过程中PCS纤维的反应程度,凝胶含量变化以及烧成纤维的组成结构和性能.结果表明:在不饱和烃不熔化过程中,PCS分子结构中的Si-H键参与反应,Si-H键反应程度和PCS纤维的凝胶含量均随不熔化温度的提高逐渐增加且逐渐趋于稳定.制得的SiC纤维中氧的质量分数降低到5%～6%,纤维的拉伸强度达到2.60 GPa.X射线衍射谱显示:与空气不熔化相比,化学气相交联法制备的SiC纤维具有更好的β-SiC微晶结构.     

添加少量聚碳硅烷对ZrB2-SiC陶瓷烧结和力学性能的影响

以ZrB2和SiC粉体为原料,加入适量的聚碳硅烷(PCS),通过热压烧结制备ZrB2-SiC复合陶瓷材料.结果表明:PCS的加入提高了ZrB2-SiC陶瓷的烧结性能和力学性能,而对于没有球磨过的ZrB2其性能并没有提高.     

微波烧结制备碳化硅粉体的研究

以乙炔炭黑和硅粉为原料,采用微波烧结技术合成制备了粒度不同的碳化硅粉体.研究了反应温度和保温时间对碳化硅粉体产率和粒度的影响.结果表明:在900℃反应30 min,所得产物的主要物相为β-SiC和仍残余少量金属Si.随着反应温度的升高,产物中SiC的含量不断增加,残余金属Si的含量则明显下降.当反应温度升高至1100℃以上时,则得到单相的β-SiC.在1200℃下反应5min,产物中主要物相为SiC,存在着少量未反应的金属Si,当反应时间延长到15 min时,即得到单相的β-SiC.     

哑铃形B-SiC晶须在Al2O3-ZrO2-C复合耐火材料中的形成

以传统工艺为基础,将碳结合材料、铝粉、硅粉、鳞片状石墨、碳黑及酚醛树脂相混合，压制成试样，然后在1200℃～1600℃之间的焦床上烧结。用XRD、SEM、EDX和TEM，确定和观察到了相组成和显微结构。显微结构变化及与温度之间的关系影响了体积密度、显气孔率和机械强度。在1200℃～1300℃之间SiC晶须和方晶石球的形成影响了初始机械性能。SiC晶须的增加与温度有关，然而，产生的SiC的形态在不同扭度下明显不同。在1200℃，1400℃．许多β-SiC晶须为哑铃形，在基质中分布良好。在1500℃以上，SiC晶须卷缩蛮粗并聚集。哑铃形β-SiC晶须可以在功能元件中原位产生，诸如水口或滑板系统中，或作为细粉加入到碳结合材料中，以改进Al2O3-ZrO2-C系统中复合碳结合材料并提高热机械性能。     

S2-掺杂对Ce3+-SiO2材料发光性能的影响

通过化学掺杂及气氛控制掺杂的手段对Ce3 -SiO2材料进行S2-掺杂改性,并对其光吸收和光致发光性能进行分析.研究阴离子掺杂对基体氧化硅材料缺陷态发光以及Ce3 的发光波长及强度的影响.结果表明:采用化学掺杂S2-可明显改变400～600 ℃热处理条件下344 nm和355 nm紫外发光强度与热处理温度的关系,但对Ce3 -SiO2材料在700～900 ℃热处理条件下产生的445 nm左右的蓝色发光影响不大;采用气氛控制手段实现S2-掺杂则可明显改变蓝色发光带的发光波长和发光强度,使发光波长由445 nm移向428 nm且发光强度为Ce3 -SiO2样品的十倍左右.     

稀土掺杂Sr3Al2O6红色发光材料的制备与表征

采用高温固相法制备了稀土掺杂的铝酸盐(Sr3Al2O6)红色发光材料.研究了样品的发光性能,讨论了灼烧温度、保温时间和稀土含量对样品发光性能的影响,结果表明,1350 ℃下灼烧2 h获得的样品为纯的Sr3Al2O6立方晶系,Pa-3空间群结构,样品的荧光发射峰位于在591 nm、611 nm、657 nm,激发光谱包含393 nm和468 nm处两激发峰.Eu离子的掺杂浓度为2.0at%,灼烧温度为1300 ℃,灼烧时间为2 h,样品的发光强度最高.     

Eu~(3+)掺杂MgO-A1_2O_3-SiO_2光致发光性能研究

采用溶胶-凝胶法制备稀土离子Eu~(3+)掺杂MgO-A1_2O_3-SiO_2堇青石基发光材料,通过应用差热分析(DSC)、X射线衍射仪(XRD)、荧光分光光度计(PL)对样品的晶体结构及光学性能进行测试。结果表明:添加烧结助剂5wt%B_2O_3,烧结温度为1200℃时,结晶度为85.93%;Eu~(3+)的添加使得晶格产生缺陷,当Eu~(3+)的添加量为4 wt%的发光强度最强,Eu~(3+)离子最强发射峰在613 nm处,发红色荧光。     

电泳沉积-烧结两步法制备C/SiC复合材料

采用电泳沉积法在石墨基体上制备厚度可控的Si涂层,考察了电泳沉积参数(电压、沉积时间、固含量及添加剂量)对涂层沉积量的影响。所制备的Si涂层通过烧结与石墨基体发生在位反应形成SiC涂层。涂层成分的XRD分析表明烧结后生成β-SiC。用SEM观察涂层烧结前后的形貌,烧结后Si渗入基体内部。孔径分布数据表明所形成的SiC涂层导致石墨孔径变小。1200℃的抗氧化实验表明涂层起到了良好的防护作用。实验提供了一种制备C/SiC复合材料的新方法。     

溶胶-凝皎-碳热还原法制备富碳β-SiC纳米粉体

采用溶胶-凝胶-碳热还原法,以正硅酸乙酯和蔗糖为原料,在0.1 MPaAr气气氛中碳熟还原合成β-SiC纳米粉体.通过x射线衍射,Raman光谱、扫描电镜和透射电镜对β-SiC纳米粉体的物相、微观结构及形貌进行了表征.结果表明:当合成温度为1 600℃时,已经开始生成β-SiC相,随着温度升高至1 700℃,完全生成了含有Csi缺陷的富碳β-Sic相.β-SiC纳米粉体表现为纳米级的团聚颗粒,平均粒径为40nm,并生成晶须.对β-SiC纳米粉体的碳热还原反应机理进行了分析,结果表明:溶胶-凝胶法明显降低了生成气态SiO控制反应的温度.     

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。