弱外磁场诱导氧化沉淀法制备Fe3O4纳米粒子

通过弱外磁场诱导氧化共沉淀法合成Fe3O4纳米粒子,并采用XRD、SEM、VMS表征产物晶型、形貌和磁性能。结果表明,弱外磁场可诱导加速α-FeOOH向Fe3O4的相转变,产物粒子为尖晶石结构,且结晶良好;产物粒子在外加弱磁场诱导后更倾向于向多面体形貌生长,且粒度分布变窄、粒径变大;产品的磁性能由于粒子晶化程度、形貌、粒度分布的变化,其饱和磁化强度、矫顽力均变大。     

Fe_3O_4/PANI抗氧化水基磁流体的制备与表征

在无氮气保护条件下,用化学共沉淀法制备了四氧化三铁(Fe3O4)纳米颗粒,并通过表面原位合成法将颗粒用聚苯胺(PANI)包裹,由此获得兼具磁性和导电性能的纳米四氧化三铁/聚苯胺(Fe3O4/PANI)材料。作者称其为Fe3O4/PANI抗氧化水基磁流体。透射电子显微镜(TEM)分析表明,该法制备的Fe3O4/PANI复合粒子的粒径在30~50 nm,其分散性能比包裹前的Fe3O4粒子明显改善。红外光谱(FTIR)和X射线衍射(XRD)测试结果发现,Fe3O4粒子及Fe3O4/PANI复合粒子具有不同的物态和晶相结构。对纳米复合粒子的抗氧化性能和磁性能的检测证实,原位合成的Fe3O4/PANI复合粒子不仅能有效防止在空气中被氧化,还可在磁场环境中实现快速富集、定位,为Fe3O4/PANI纳米复合粒子在生物医学领域的应用提供了可能。     

弱磁场辅助氧化共沉淀法合成正八面体和六方体型Fe3O4纳米颗粒

采用弱磁场辅助氧化共沉淀法制备正八面体型和六方体型形貌的Fe3O4纳米粒子.X射线衍射结果表明:产物具有尖晶石结构,结晶良好且纯度高.扫摇电子显微镜观察结果表明:产物Fe3O4纳米粒子均为二次粒子,由更小的粒子生长而成.经振动样品磁强计测定,各种形貌的Fe3O4纳米粒子都具有良好的磁性能.由于六方体型Fe3O4纳米晶形状的各向异性,其饱和磁化强度小于正八面体型形貌的Fe3O4纳米粒子.同时,初探了弱磁场影响不同形貌的Fe3O4纳米粒子的形成机制.     

弱磁场对EP/MWCNTs–Fe_3O_4复合材料结构与性能的影响

采用均匀沉淀法制备了多壁碳纳米管–四氧化三铁(MWCNTs–Fe3O4)复合粒子,并将复合粒子与环氧树脂(EP)复合,在弱磁场(0.2~0.3 T)下固化制备了EP/MWCNTs–Fe3O4复合材料。采用X射线衍射仪、扫描电子显微镜和震动样品磁强计对复合粒子的结构和磁性能进行了表征,重点考察了弱磁场对该复合材料结构、电性能与压缩性能的影响。结果表明,复合粒子表现出顺磁性,其中Fe3O4和MWCNTs彼此相对独立,能够较均匀地分散在EP中;在外磁场作用下,复合粒子在EP中的分布表现为磁流体的特征,沿磁场方向定向排列形成链状结构;随复合粒子含量增加,复合材料的介电常数、导电性和压缩强度总体上呈上升趋势,压缩弹性模量先升高后降低;磁场诱导对复合材料性能的影响与粒子含量密切有关,当复合粒子质量分数不高于2%时,磁场诱导下的复合材料介电常数和导电性高于未施加磁场的复合材料,当复合粒子质量分数不高于5%时,前者的压缩强度高于后者,在考察的含量范围内,前者的压缩弹性模量始终高于后者。     

Fe_3O_4磁性纳米粒子的共沉淀法制备研究

叙述了以液相共沉淀法制备纳米磁性Fe3O4粒子的工艺,研究了反应搅拌速度、n(Fe3+)/n(Fe2+)的比例、pH值和熟化温度对制备纳米Fe3O4粒子的影响,并利用透射电镜表征观察Fe3O4纳米粒子的形貌。研究结果表明,在搅拌速度较快的情况下制备纳米级Fe3O4颗粒的最佳合成工艺条件为:n(Fe3+)/n(Fe2+)为1.8∶1(摩尔比),熟化温度70℃,熟化时间30 min,以氨水作沉淀剂最佳pH值是9左右,可制得纯度较高,粒径小于10 nmFe3O4磁性粒子。     

离子液体中合成Fe3O4/PANI复合纳米颗粒

以FeCl3.6H2O和FeCl2.4H2O为原料,以水为介质,利用化学共沉淀法,常温下反应合成了Fe3O4纳米粒子,并进一步以Fe3O4纳米粒子为原料,采用原位聚合法分别在H2O和氯代1-丁基-3-甲基咪唑([BMIM]Cl)离子液体中合成了Fe3O4/聚苯胺(PANI)纳米复合粒子,用透射电子显微镜(TEM)、X射线衍射仪(XRD)、热分析仪(TG)、电导率仪、多功能振动样品磁强计对样品的形貌、结构和电磁性能进行了表征。结果表明:在这两种介质中都可以得到核壳型复合颗粒,但离子液体中合成的复合颗粒粒度小、分散性好且聚苯胺的结晶程度高。在离子液体中制备的复合材料与水中相同条件下制得的复合材料相比,电导率及磁性能均有提高。在离子液体中制备磁性导电复合材料是一种绿色高效的工艺。     

超顺磁性Fe_3O_4纳米粒子化学合成及生物医学应用进展

综述了超顺磁性氧化铁纳米粒子合成方法和在生物医学领域中的研究进展,重点讨论了目前比较常用的化学合成方法对Fe3O4纳米粒子性能的影响,比较了各种方法的优劣,在此基础上,概述了超顺磁性Fe3O4纳米粒子在核磁共振成像、磁性靶向给药、磁性分离等方面的应用。通过综述,可望获得对Fe3O4纳米粒子的化学合成方法和生物医学应用的全面了解。     

超顺磁性Fe_3O_4纳米粒子化学合成及生物医学应用进展

综述了超顺磁性氧化铁纳米粒子合成方法和在生物医学领域中的研究进展,重点讨论了目前比较常用的化学合成方法对Fe3O4纳米粒子性能的影响,比较了各种方法的优劣,在此基础上,概述了超顺磁性Fe3O4纳米粒子在核磁共振成像、磁性靶向给药、磁性分离等方面的应用。通过综述,可望获得对Fe3O4纳米粒子的化学合成方法和生物医学应用的全面了解。     

聚丙烯/四氧化三铁纳米复合材料的制备、表征及磁性能研究

采用固态高速搅拌预混-熔融密炼过程制备了磁性聚丙烯(PP)/四氧化三铁(Fe3O4)纳米复合材料,并分别利用扫描电镜(SEM)、X射线衍射(XRD)、示差扫描量热仪(DSC)、热失重分析仪(TGA)和振动样品磁强计(VSM)对获得的复合材料的形貌、结构及磁性能进行了表征。结果显示:Fe3O4纳米粒子质量分数为5%时在聚合物基体中分散良好,基本呈单颗粒分散;随着Fe3O4含量的增加,粒子在PP基体中团聚程度加剧。Fe3O4和PP在复合材料中保持了各自的晶相结构,但是Fe3O4的加入降低了PP的结晶程度。同时,Fe3O4的加入提高了PP的热稳定性。振动样品磁强计(VSM)的结果表明:复合材料的饱和磁化强度(Ms)随Fe3O4含量的增加而增加,并呈线性的依赖关系;矫顽力(Hc)和剩余磁化强度(Mr)均很小,所制得的磁性纳米复合材料近似呈超顺磁性;该研究为磁性高分子纳米复合材料的制备提供了一种简单易行,Fe3O4纳米粒子在聚合物基体中良好分散,并且可以大批量生产磁性纳米复合材料的方法,并可能促进PP/Fe3O4纳米复合材料在电磁屏蔽和微波吸收等领域的应用。     

强磁性Fe_3O_4纳米粒子的制备及其性能表征

采用共沉淀法在无N2气保护下制备了比饱和磁化强度达到75 9emu g的强磁性Fe3O4纳米粒子。在用NaOH溶液沉淀Fe3+和Fe2+混合溶液的过程中,考察了n(Fe2+)∶n(Fe3+)、晶化时间、晶化温度、总铁浓度和NaOH溶液浓度等条件对Fe3O4纳米粒子的粒径分布及磁性的影响。当n(Fe2+)∶n(Fe3+)=5 5∶1 0,晶化时间为2h,晶化温度为50℃时,Fe3O4纳米粒子磁性最佳。所制得的Fe3O4粒子为结晶完整、具有较高纯度和粒径分布均匀的立方体形纳米颗粒;其相变温度随着Fe3O4纳米粒子粒径的减小而降低。Fe3O4纳米粒子的等电点约为pH=7 2。     

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。