PTC钛酸钡瓷中的晶界受主态

通过350℃下的氧化-还原处理所产生的PTC效应变化,研究了钛酸钡半导瓷中的晶界受主态。第一次从实验上直接证实了化学吸附氧是产生PTC效应的晶界受主态之一。EPR谱分析表明,试样中的Mn在室温时主要以Mn~(3+)的形式存在,接近Tc时捕获一个电子形成Mn~(2+),从而对PTC效应作出贡献。此外,EPR谱还表明,无论在TiO_2过量或BaO过量的试样中,在所测量的温度范围内都没有V'_B.顺磁信号。     

施、受主掺杂对高居里点BaTiO3基PTCR陶瓷材料性能的影响

以合成的(Ba_(0.6)Pb_(0.4))TO_3为主要原料,通过电性能测试、SEM、XRD等手段分析研究了施主Nb~(5 )掺杂以及施主Nb~(5 )、受主Mn~(2 )共掺对高居里点BaTiO_3基PTCR陶瓷材料性能的影响。结果表明,施受主掺杂不影响材料基体的晶体结构,适量的施主Nb~(5 )掺杂可降低材料的室温电阻率从而改善其性能,受主Mn~(2 )掺杂提高了施主Nb~(5 )掺杂的高居里点BaTiO_3基PTCR陶瓷材料的室温电阻率且只有极少量的Mn~(2 )掺杂才使材料的PTC效应稍有提高。     

Gd_2O_3掺杂对BaTiO_3陶瓷电性能的影响

采用溶胶-凝胶法制备了掺杂不同量Gd2O3(分别为0 001、0 002、0 003、0 005、0 007mol mol)的BaTiO3陶瓷,并对其电性能进行了研究。结果表明:Gd2O3掺杂使BaTiO3陶瓷的电阻率明显下降,当添加量为0 002mol mol时,电阻率最小,为1 27×105Ω·m;晶粒电阻随着温度的变化,呈现NTC效应,而晶界电阻随着温度的变化,呈现PTC效应,而且晶界电阻远远大于晶粒电阻,说明Gd2O3掺杂BaTiO3陶瓷的PTC效应是一种晶界效应;Gd2O3掺杂使BaTiO3陶瓷的介电常数和介电损耗在低频时明显增大,在高频时又明显降低。     

BaTiO3基PTCR中晶界氧元素的作用分析

采用柠檬酸盐溶胶-凝胶法制备出复合掺杂的BaTiO3粉体,然后成型烧结制备了PTCR试片.首先通过氩气气氛热处理试验,验证了氧能够有效地提高PTC效应,进而利用透射电镜对典型试片的晶界区和晶粒内部的元素成分进行能谱定量分析,表明晶界区的氧含量明显高于晶粒内部,甚至超过了施、受主含量的总和.分析了氧对晶界势垒的影响,用晶界层状氧吸附模型进行了解释.     

受主掺杂BaTiO_3陶瓷热敏电阻的研究

本文通过对试样ρ-T特性的测试,研究了CuO和Cu_2O掺杂对BaTiO_3陶瓷半导化及PTC效应的影响。在本实验条件下,确定了PTC热敏电阻的最佳组成和最佳烧成制度,并通过扫描电子显微镜(SEM)对典型试样显微结构的观察和分析,提出了优质PTC材料应具有的理想化显微结构模型。     

钛酸钡半导体陶瓷的显微结构分析

BaTiO_3半导体陶瓷广泛用做PTC热敏电阻和晶界层电容器。BaTiO_3半导体陶瓷是多晶材料,其性能不仅决定于化学组成,而且与其显微结构有着密切关系。BaTiO_3半导体陶瓷的电阻正温度系数效应(PTC效应)最先由W.Heywang提出的晶界势垒模型进行了解释。随后,又有一些作者对Heywang提出的晶界势垒模型进行了修正。为了能从直接的实验数据验证势垒模型,很多人研究了BaTiO_3PTC陶瓷的显微结构。这些有关BaTiO_3陶瓷显微结构     

掺镧钛酸钡陶瓷晶界的再氧化

掺La的BaTiO3陶瓷在H2和Ar（体积比1：99）的还原气氛下烧结后,在氧分压p（CO2）-260Pa的气氛（Ar和O2的混合气体）下进行氧化,测量了吸氧量不同时的复阻抗图谱,研究了再氧化过程中晶粒和晶界的吸附氧对电阻率的影响。结果表明：在还原气氛下烧结可以扩展有效施主掺杂浓度的范围,通过晶粒的异常生长．制备出高施主掺杂量（10％,摩尔分数）的半导性BaTiO3陶瓷。再氧化过程中,随氧化温度的升高（1017～1380℃）,晶界吸附氧的量增大,晶界处的晶界势垒包括两部分：外部晶界吸收氧原子充当表面受主态;内部晶界在氧化过程中被氧化形成正离子空位（Ti空位）充当受主态．从而提高了受主态密度,导致样品的正温度系数电阻效应增强。     

A508-3钢液对钢包用含碳耐火材料的侵蚀机理

采用感应炉浸渍实验法模拟钢包现场使用情况,借助X-射线衍射仪(XRD)、扫描电子显微镜(SEM)和热重分析设备(TGA)等分析手段,研究了含碳耐火材料的相组成、高温失重特性以及被钢液侵蚀后的显微组织。结果表明,在20～1 300℃加热阶段,MgO-C试样一直在减重,减重共计1.142 7mg,占试样总质量的16.93%,而Al2O3-MgO-C试样减重较少,减重共计0.441 4mg,占试样总质量的6.45%。加热温度在1 070～1 170℃,Al2O3-MgO-C试样少量增重。钢液对MgO-C和Al2O3-MgO-C耐火材料的侵蚀机理基本相同,均沿主相晶界侵入,晶界处有许多小孔洞,且晶界和晶内分布有许多小铁珠。     

HDPE/ PC/CB复合体系双逾渗行为的研究

以炭黑(CB)为导电填料,填充到2种不相容的高聚物高密度聚乙烯(HDPE)和聚碳酸酯(PC)基体中制备高分子基正温度效应(PTC)材料.研究表明,CB在HIRE中的逾渗阈值约为20%;HDPE/PC/CB三元复合体系形成了双逾渗行为,当HDPE/PC质量比为40/60时,三元复合体系具有较好的PTC及PTC重复性.     

接枝炭黑/聚乙烯导电复合材料正电阻温度系数(PTC)效应研究

用接枝炭黑作导电粒子研究了在聚乙烯基材中的正 (电阻 )温度系数 (PTC)效应。结果发现 ,甲基丙烯酸甲酯接枝的炭黑在高密度聚乙烯中能表现出较好的 PTC效应。从实验现象分析 ,接枝炭黑的 PTC效应是结晶熔融和体积膨胀双重变化共同作用的结果。     

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。