烧结工艺对Ca3Co4O9基热电氧化物电性能的影响

采用溶胶-凝胶化学法合成了Ca3Co4O9热电氧化物粉末,分别采用陶瓷烧结工艺方法和放电等离子烧结(Spark Plasma Sintering,SPS)的方法制备了Ca3Co4O9热电氧化物块体材料.利用X射线衍射XRD、扫描电子显微镜SEM和电输运参数测试仪分析了所得样品的物相、微观组织结构、晶粒取向度和电输运性能.结果表明,不同制备方法均可得到纯相的Ca3Co4O9热电氧化物块体材料;通过陶瓷烧结工艺方法制备的Ca3Co4O9热电氧化物块体晶粒取向度较低,但随着成型压力的增加而提高;SPS烧结的方法制备的Ca3Co4O9热电氧化物块体晶粒取向度最高;试样电性能随着晶粒取向度的提高逐渐提高,其中SPS烧结方法制备的块体材料电性能最高,在测试温度最高点700℃时功率因子达3.85 μWmK-2,远高于普通烧结试样.     

Ca_(2.7)Sr_(0.3)Co_4O_9 和 Ca_(0.95)Sm_(0.05)MnO_3 热电材料的性能及器件(英文)

为了构造具有一定实用性能的氧化物热电器件,对 p 型 Ca3Co4O9和 n 型 CaMnO3过渡金属氧化物半导体进行研究,结果表明:Ca2.7Sr0.3Co4O9和 Ca0.95Sm0.05MnO3的热电性能良好。Ca2.7Sr0.3Co4O9陶瓷的微观形貌呈片层状及尖锐的(00?)相,说明具有高度织构,Ca0.95Sm0.05MnO3陶瓷为单一相正交晶系。分析了样品形成的化学反应过程。热电参数测试结果表明:Ca2.7Sr0.3Co4O9为 p 型半导体,空穴导电机制,Ca0.95Sm0.05MnO3为 n 型半导体,电子导电机制。两种材料的电阻均较低,在 870 K,Seebeck 系数分别为 170 μV/K 和–167 μV/K。在测量温度范围内,热导率变化很小,并计算出热电优值。利用此两种材料构造热电器件,并对其性能进行测试。     

Ca3Co4O9陶瓷的制备和热电性能

氧化物半导体陶瓷材料是新型的中、高温热电材料。采用传统固相合成法和溶胶－凝胶法成功地制备了Ca3Co4O9陶瓷。对它们的显微结构和热电性能（Seebeck系数、电导率和热导率）进行了研究。实验结果表明，由两种方法制备得到的Ca3Co4O9陶瓷具有类似的热电性能。Ca3Co4O9陶瓷为取向无规则片状结构，属于p型半导体热电材料，其热电品质因子随温度升高而增大。Ca3Co4O9陶瓷具有大的Seebeck系数和低的热导率，但它的电导率仍然偏低，导致了它的热电品质因子比传统热电合金的热电品质因子低。     

Ca3Co4O9陶瓷的固相法制备及分析

本实验采用固相合成法成功地制备了Ca3Co4O9热电材料。通过对样品的显微结构与物相组成等进行分析研究,优化了制备工艺。实验结果表明:由固相法制得的Ca3Co4O9为取向无规则的片状组织;适当提高煅烧温度、延长保温时间有利于片状组织的生长。     

掺杂金属离子对Ca3Co4O9的热电性能的影响

采用溶胶-凝胶法,在常压空气中,经850℃烧结4h制备了Ca3Co4O9掺杂不同金属离子M(Na ,Ag ,La2 )的(Ca1-xMx)3Co4O9热电材料.通过X射线衍射、扫描电镜等对材料的微结构进行了表征,重点考察了掺杂不同金属离子对Ca3Co4O9中温热电性能参数Seebeck系数、电导率和功率因子的影响.结果表明:金属掺杂的(Ca1-xMx)3Co4O9热电材料具有致密的内部结构,并能够明显改善Ca3Co4O9的热电性能,尤其是掺杂Na 样品的热电性能有较为明显的提高,并且掺杂离子浓度对改善热电性能也有一定影响,组成为(Ca0.90Na0.10)3Co4O9时的功率因子提高最明显.     

Ca3Co4O9热电陶瓷材料的制备与表征

本实验采用溶胶-凝胶法制备了Ca3Co4O9陶瓷,对样品的显微结构和热电性能进行了表征.实验结果表明,Ca3Co4O9为取向无规则层片状组织,制备工艺参数对样品的显微结构和热电性能有重要影响.     

制备工艺对La改性的Ca3Co4O9基陶瓷热电性能的影响

利用常压烧结、冷等静压成型后常压烧结及热等静压烧结3种不同制备工艺,合成了(Ca0.9La0.1)3Co4O9热电材料。XRD分析表明：不同工艺制备的样品均为Ca3Co4O9相。样品的SEM照片显示：晶粒为片状结构;热等静压烧结制备的样品,其片状结构不明显,但致密度较之另外两种工艺大幅度提高,其相对密度为95％。制备工艺对(Ca0.9La0.1)3Co4O9热电材料Seebeck系数影响不大,但热压烧结样品能大幅度提高(Ca0.9La0.1)3Co4O9电导率。在一定温度范围内,随温度升高,功率因子大幅度增加,对于热压烧结的样品尤为显著。     

Ca_3Co_4O_9陶瓷的热传输特性(英文)

采用溶胶-凝胶法,结合常压烧结工艺制备了Ca3Co4O9陶瓷.通过热重-差示扫描量热法(thermogravimetric-differential scanning calorimetry,TG-DSC)、X射线衍射(X-ray diffraction,XRD)和扫描电镜(scanning electron microscope,SEM)等测试手段探讨了Ca3Co4O9陶瓷的形成过程,分析了不同工艺参数对Ca3Co4O9陶瓷显微结构及性能的影响,研究了晶粒尺寸与热传输性能之间的关系.结果显示:Ca3Co4O9为取向无规则层片状结构,当煅烧温度为750～900℃时,能得到纯相Ca3Co4O9,Ca3Co4O9陶瓷的热导率(k)较低,且随着温度的升高而逐渐增大.晶粒尺寸的减小对其晶格热导率(k1)影响显著,当平均晶粒由92 nm减小到63 nm时,k1由1.529 W/(m·K)减小到0.959 W/(m·K),但对载流子热导率(kc)的影响很小.Ca3Co4O9陶瓷的k随晶粒尺寸的减小而降低,主要是由于kl随晶粒尺寸的减小而降低所致.     

Ca3Co4O9基氧化物热电材料研究进展

详细综述了提高Ca3Co4O9基氧化物热电性能的主要途径,包括制备工艺的改进、掺杂改性研究、热电性能的结构调控等,着重从Ca位掺杂和Co位掺杂两个方面介绍了Ca3Co4O9在掺杂改性方面的研究进展,并提出了该材料存在的问题和今后的发展方向。     

失配层钴酸盐与掺镧系列的电子结构与热电性能

用离散变分密度泛函方法(DFT-DVM)计算了失配层钴酸盐Ca3Co4O9及其掺La系列，讨论了电子结构、化学键等与热电性能之间的关系。计算结果表明，Ca3Co4O9的态密度费米能级附近的价带和导带主要由Ca3Co4O9层中的O2p和Co3d原子轨道贡献，Ca3Co4O9的热电性能主要由Ca3CoO3层决定，而与CoO2层无直接联系，这与一般的二元氧化物无热电性能，而三元氧化物可能有较好的热电性能的结论一致。随着掺La量的增加，费米能级处价带和导带之间的能隙首先减小，随之达到最小值，进而又增大。由于能隙直接影响材料的热电性能，因此，存在一个最佳掺杂量以达到热电性能的最佳改善，这与实验结论一致。     

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。