Ca2+掺杂对BiFeO3陶瓷结构和磁、介电性能的影响

以Bi(NO3)3·5H2O、Fe(NO3)3·9H2O和Ca(NO3)2·4H2O为原料、乙二醇甲醚为溶剂、柠檬酸为络合剂,采用溶胶–凝胶法制备Bi1–x Cax FeO3(x=0、0.05、0.10、0.15、0.20)陶瓷样品。结果表明:所有样品的主衍射峰与纯相BiFeO3相吻合,样品晶粒尺寸随Ca2+掺杂量的增加而减小,在室温下各样品均具有完整的磁滞回线,样品铁磁性显著提高。当x=0.10时,剩余比磁化强度达到最大值(0.11A·m2/kg)。在外加磁场为398 kA/m时,样品的比磁化强度在644 K附近出现明显的反铁磁相变,反铁磁相变温度TN随掺杂量的增加而升高。在300~900 K,样品顺磁相变温度TP,以及TN和TP处比磁化强度的差值随Ca2+的增加均呈现先上升,在x=0.10时达到最大值,之后又呈下降趋势。样品在850K时比磁化强度出现明显变化,变化幅度随Ca2+掺杂量的增加而减小,在x=0.10时最小,之后又增大。不同磁场下样品剩余比磁化强度随温度变化表明:Bi1–x Cax FeO3陶瓷样品存在变磁性,当x=0.10时,变磁性最为明显。磁电耦合效应观测结果表明:样品的磁电耦合系数为负值,介电常数随外磁场变化反应灵敏,在x=0.10时磁电耦合效应为–14.2%,是纯相BiFeO3(其磁电耦合效应为–5%)的近3倍,表明掺杂适量Ca2+可增强样品的磁电耦合性能。     

纳米颗粒对复合电刷镀过程中镀液特性及镀层沉积速度的影响

本文研究了特快镍刷镀液(TK-Ni)及两种不同纳米颗粒含量的纳米Al2O3／特快镍复合刷镀液(10n／TK-Ni和30n／TK-Ni，其中前者纳米颗粒含量较少)在刷镀过程中的温度和密度变化及复合镀层厚度的变化，解释了纳米颗粒的加入对镀液温度和密度的影响及对镀层沉积速率的影响。试验结果表明：刷镀过程中含纳米颗粒的复合镀液的温度和密度均较高，且二者均随纳米颗粒含量的增大而升高；随刷镀过程的进行，镀液温度升高，密度减小，复合镀液密度在刷镀时间达30min后出现回升现象；复合镀层沉积速度较快，且镀层沉积速度随镀液中纳米颗粒含量增加而增大。     

纳米复合材料Co0.5Ni0.5Fe2O4-SiO2的显微结构和磁性

采用溶胶-凝胶法制备了Co0.5Ni0.5Fe2O4-SiO2纳米复合材料.利用热重-差热分析表征了热处理过程中干凝胶的变化.用X射线衍射、透射电镜、振动样品磁强计和M(o)ssbauer效应研究了样品的结构、晶粒尺寸和磁性.结果表明:经900℃热处理后,形成了分布均匀的Co0.5Ni0.5Fe2O4-SiO2纳米复合材料,其中Co0.5Ni0.5Fe2O4-SiO2的晶粒尺寸为20 nm.随热处理温度的升高,样品的晶粒尺寸、比饱和磁化强度以及矫顽力均变大,并从超顺磁和磁有序的混合状态转变为完全的磁有序状态.     

化学共沉淀法合成CoFe2O4纳米颗粒及其磁性能

用共沉淀法合成磁性CoFe2O4纳米颗粒,并经过不同温度处理后,对合成的样品进行X射线衍射物相分析。用透射电镜观察样品的形貌,测量了样品的颗粒粒径并对其磁学性能进行研究。结果表明：随着热处理温度升高,颗粒长大。经100℃热处理后的颗粒粒径为10～12nm。经700℃热处理后的颗粒尺寸增大为10～40nm。样品的饱和磁化强度和剩余磁化强度也随着热处理温度的升高而增加。     

电沉积纳米晶Co-B合金膜的影响因素

通过正交试验和单因素试验,发现电沉积纳米晶Co-B合金的镀速随镀液温度的升高、电流密度的增大、pH的增加而增大。在镀液稳定范围内,随硫酸钴、硼氢化钠质量浓度的增加而增大,随酒石酸钠质量浓度的增加而减小,当四硼酸钠达到一定质量浓度时,对镀速影响较小。在研究范围内所得合金膜全部为非晶态,扫描电子显微镜和扫描隧道电子显微镜观察发现,非晶镀层是由纳米相微粒构成微米级的二次颗粒,二次颗粒堆砌形成薄膜。     

Fe_3O_4纳米颗粒的磁后效研究

用Preisach磁滞模型模拟了Fe3O4纳米颗粒的磁后效行为,并与实验测量结果进行了比较。结果表明:理论计算和实验结果符合的较好。其磁化强度随时间单调减小,与时间的对数成线性变化,磁场越接近负的矫顽力时衰减越快。通过Preisach模拟得到体系的涨落场和激活体积,激活体积大于实验测得的平均颗粒尺寸,由此解释了Fe3O4纳米颗粒的反磁化机制。     

掺Dy3+铁氧体硅油基磁流体磁特性与温度的相关性研究

利用液相共沉淀法制备了纳米掺Dy3+铁氧体磁颗粒,用表面活性剂修饰后,在超声振荡下分散在硅油中制得磁流体.分别用TEM、XRF、XRD、SQUID分析手段对样品进行了表征,在203 ～358 K范围内,研究了温度变化对磁流体磁特性和粘度的影响.结果表明:制备的磁颗粒平均粒径约16.3 nm、物相主要是Fe2O3、Dy2O3,结构为面心立方尖晶石型.通过磁性能测试发现,磁流体的饱和磁化强度(MS)、矫顽力(HC)和粘度随温度(T)的降低,呈现出增大的变化规律;并且还发现,298 K≤T≤358 K时,温度降低对矫顽力和粘度的影响较小;T＜298 K时,温度降低,矫顽力和粘度明显增大.     

化学镀Co-B合金(Ⅱ)

纳米晶合金具有独特的物理性能.通过化学镀方法获得纳米晶Co-B合金,分别研究了沉积层厚度和热处理温度对其矫顽力和比饱和磁化强度的影响.结果表明,开始阶段,随着镀层厚度的增加,矫顽力逐渐减小,而当镀层厚度大于0.6 μm时,矫顽力随镀层厚度的增加而逐步升高;比饱和磁化强度则始终随镀层厚度增加呈上升趋势.开始阶段,随着热处理温度的上升,矫顽力上升,当热处理温度高于450℃时,矫顽力开始减小;热处理温度对比饱和磁化强度影响较为复杂.     

不同热处理温度对BiMnO3纳米颗粒成分及结构的影响规律

BiMnO₃因其铁磁性和铁电性共存的可能性倍受关注。然而,经过热处理后BiMnO₃纳米颗粒成分的变化过程尚不清楚。本文选用共沉淀法合成BiMnO₃纳米颗粒,将制备好的纳米颗粒在空气中以不同温度(300~600 ℃)热处理20 min。利用透射电子显微镜(TEM)、X射线衍射仪(XRD)以及X射线光电子能谱(XPS)系统地研究了BiMnO₃纳米颗粒的成分与晶体结构。TEM结果说明随着热处理温度的升高,BiMnO₃纳米颗粒尺寸逐渐增大。XRD谱显示当热处理温度高于500 ℃时,晶体结构由原来的单斜相转变为Pnma正交对称相。XPS结果证明氧缺陷会随温度的升高而减少。除此之外,XRD和XPS结果均说明,热处理温度达到600 ℃时BiMnO₃纳米颗粒会在空气中分解出Bi₂O₃。该研究结果有助于理解热处理对BiMnO₃纳米颗粒成分变化的影响。     

铁钴合金纳米颗粒体磁性的研究

利用溶胶法首次制备了粒状铁钴合金纳米颗粒体，并由X射线衍射（XRD）和透射电子显微镜（TEM）进行了物相分析和颗粒形貌的观察。利用振动样品磁强计（VSM）测量了铁钴纳米颗粒体在不同温度下的磁参数。结果显示，可以通过改变制备条件得到不同颗粒尺寸，不同铁钴比例，不同SiO2含量和矫顽力不同的粒状Fe－Co－SiO2纳米颗粒体，在113～773K的温度范围内，颗粒体的饱和磁化强度和矫顽力随温度的变化非常平缓，因此，粒状FeCo－SiO2纳米颗粒体有望成为在较大温度范围内使用的磁记录介质     

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。