高能球磨时间对MgNb2O6陶瓷显微结构和微波介电性能的影响

采用高能球磨法制备粉体,研究了粉体球磨时间对MgNb2O6陶瓷显微结构和微波介电性能的影响,结果表明,1180℃烧结陶瓷,随球磨时间增加,平均粒径减小,气孔率降低,相对密度增大,介电常数增大;升高烧结温度到1220℃以上,不同球磨时间制备陶瓷样品相对密度达到95.8％以上,平均晶粒尺寸3.5m,εr为19.7,而Qxf值随球磨时间先增大后减小.高能球磨制备粉体能有效促进MgNb2O6陶瓷在1220℃下中温烧结,且具有优良的微波介电性能(εr=19.7,Q×f=28 744 GHz),有望成为新一代中温烧结高频微波介质基板材料.     

高能球磨对Pr_6O_(11)和Y_2O_3掺杂ZnO压敏电阻微观结构和电学性能的影响

利用高能球磨法制备Pr6O11、Y2O3掺杂ZnO压敏电阻,并对球磨时间对微观结构、物相组成及电学性能的影响进行了研究和分析。高能球磨有利于微观组织的均匀化和晶粒的细化,从而提高了电学性能。当球磨时间从0到10 h时,烧结后的ZnO晶粒尺寸变化从8.7到4.0μm,坯体烧结密度变化从5.40到5.62 g/cm3。最佳的制备工艺为球磨时间为7.5 h,烧结温度为1100℃,其对应的电学性能分别为:电位梯度(V1mA)是542 V/mm,漏电流(IL)是2.88μA,非线性系数(α)是47。     

CaTiO3添加剂对氧化铝陶瓷烧结、显微结构及微波介电性能的影响

CaTiO3添加剂通过湿法球磨与Al2O3粉料混合,并通过无压烧结制备了氧化铝陶瓷,研究了CaTiO3添加剂对氧化铝陶瓷烧结性能、相组成、显微结构和微波介电性能的影响.CaTiO3可以使Al2O3的烧结温度降低至1450℃,但在该温度下烧结的样品由于CaTiO3的加入会产生CaAl12O19第二相.样品中存在大、小两种晶粒,根据EDS能谱分析,大晶粒主要是CaAl12O19,而小晶粒为Al2O3和CaAl12O19的混合相.添加CaTiO3有利于Al2O3陶瓷介电常数的提高,1450℃下掺杂2.5wt％ CaTiO3的氧化铝陶瓷具有较好的烧结性能和微波介电性能,相对密度可达到97.74％,εr～10.86,Q×f～ 8061 GHz.     

ZnO片式压敏电阻厚膜中Cr_2O_3含量的优化(英文)

研究三氧化二铬(Cr2O3)对氧化锌(ZnO)片式压敏电阻厚膜物相结构、微观结构和电性能的影响。X衍射分析表明:Cr2O3降低Bi4Ti3O12相的分解温度,并最终影响陶瓷厚膜的致密度、晶粒尺寸及电性能。当烧结温度为880℃时,Cr2O3摩尔(下同)掺量为0.3%的陶瓷厚膜能够得到良好性能:体积密度ρv=5.52g/cm3,晶界势垒Φb=0.116eV,非线性系数α=24.8。研究烧结温度与片式压敏电阻微观结构和电性能的关系,Cr2O3掺量为0.3%的片式压敏电阻在880℃烧结时,能够获得最佳电性能:压敏电压V1mA=25V,α=23.6,漏电流Il=2.8μA。该片式压敏电阻的低烧结温度和高非线性在工业生产中具有很大优势。     

莫来石助剂对氧氮化铝透明陶瓷显微结构及光学性能的影响

以自制AlON粉体为原料、莫来石为烧结助剂,结合无压烧结与热等静压烧结在相对较低的温度下(分别为1 880℃和1 800℃)制备了AlON透明陶瓷,研究了莫来石含量对无压烧结和热等静压烧结AlON陶瓷的显微结构以及光学性能的影响。结果表明,莫来石含量在0.02%～0.20%(质量分数)时,无压烧结AlON陶瓷为纯AlON相,其Raman光谱相似。随着莫来石含量增加,AlON陶瓷无压预烧体的致密度先增加后减小,而其晶粒尺寸逐渐变大。热等静压烧结后,所有样品的致密度均高于理论密度的99.2%且晶粒长大;其致密度、晶粒和透过率随莫来石含量增加呈现出先增大后减小的趋势。最终,0.05%莫来石AlON透明陶瓷致密度为3.67 g/cm³,平均晶粒尺寸为80.4μm,其透过率最高,4 mm厚样品在2 000 nm处达到81.9%。     

烧结温度对纯氧化钙性能的影响

研究了烧结温度对纯的氧化钙制品各性能(密度、晶粒度、抗水化性)的影响,并探讨了烧结温度对纯氧化钙制品抗水化性能的影响机理。研究表明,温度从1630℃升高到1720℃,纯氧化钙制品密度由2.88 g/cm3增加到3.13 g/cm3,晶粒尺寸由27μm左右增大到近60μm,制品水化增重率随烧结温度升高而减少。纯氧化钙制品抗水化性随烧结温度提高的机理,一方面是由于制品致密度的提高减少了水进入Ca O制品的通道;另一方面由于晶粒尺寸的增大,减少了水分与Ca O的接触面积。     

低温烧结Mg_4Nb_2O_9-0.75wt%V_2O_5-1.5wt%Li_2CO_3微波介质陶瓷及其性能研究

采用高能球磨法制备陶瓷,研究了0.75wt%V2O5和1.5wt%Li2CO3共掺杂对Mg4Nb2O9陶瓷的烧结性能和微波介电性能的影响。实验结果表明0.75wt%V2O5和1.5wt%Li2CO3共掺杂有助于Mg4Nb2O9陶瓷在烧结过程中形成液相,促进低温致密化烧结,进而降低陶瓷的烧结温度。900℃烧结Mg4Nb2O9陶瓷,结构致密、组织均匀,平均粒径0.75μm,εr=12.58,Q×f=5539 GHz。随烧结温度升高,晶粒长大,密度升高,εr和Q×f值增大。微波介电性能表征表明Mg4Nb2O9-0.75wt%V2O5-1.5wt%Li2CO3陶瓷在950℃下低温烧结,获得εr=13.07,Q×f=10858GHz的亚微米级陶瓷,其优良的微波介电性能使其有望成为新一代低温烧结低介高频微波介质基板材料。     

铝渣的烧结性能研究

以铬盐厂废弃的铝渣为原料,将其破碎,湿法球磨,烘干后以150 MPa压力压制成20 mm×10 mm的试样,然后经1 700℃煅烧3 h。按标准测定各试样的体积密度、显气孔率和吸水率。采用XRD检测煅烧前后铝渣中的物相组成;采用SEM观察试样的显微结构并结合能谱仪对微区成分进行分析。结果表明:经湿法球磨6 h后,铝渣的平均粒径由6.779μm降低到1.728μm,在1 700℃煅烧3 h可获得良好的烧结。烧结体主要物相为铬刚玉,其晶粒呈板片状结构,且晶粒间结合致密,部分晶粒已融合在一起,结合处的晶界已经消失,铬刚玉晶粒尺寸最大的可达15μm。     

掺杂ZnO-B2O3低温烧结BiNbO4介质陶瓷的研究

研究了烧结助剂ZnO-B2O3对BiNbO4陶瓷烧结特性及介电性能的影响.结果表明ZnO-B2O3形成晶界玻璃相存在于晶粒之间,促进烧结,大幅度降低BiNbO4陶瓷的烧结温度,促使瓷体晶粒尺寸均匀和致密;但ZB的质量分数大于3%,阻碍晶粒长大,破坏晶体结构和排列,导致材料的缺陷和本征损耗增加,从而降低材料的介电性能.ZnO-B2O3的掺杂量以1%为最佳,在880℃保温4h,可达到97%理论密度,在100MHz测试频率下,εr=42,tanδ＜1.5×10-3.     

高能球磨对YAG陶瓷制备的影响(英文)

通过高能球磨法处理Y2O3-Al2O3(yttrium aluminum garnet,YAG)混合粉体,对球磨产物进行煅烧、成型以及烧结,并对固相反应中的物相变化、YAG粉体形貌以及YAG陶瓷密度、力学性能及显微结构进行表征和分析,确定了最佳的球磨时间和粉体煅烧温度.研究表明:经过40h高能球磨,得到的球磨产物具有良好的活性.采用传统固相法制备的YAG粉体,需要在1 500℃煅烧,该方法处理的YAG粉体在1 200℃煅烧2 h,可以得到活性较高的YAG粉体,使粉体的煅烧温度下降了300℃.利用常压烧结在1 550℃烧结坯体2h,得到致密的YAG陶瓷,明显改善了YAG陶瓷制备技术.     

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。