稀土离子(Gd~(3+),Ce~(3+)/Ce~(4+),Eu~(3+))对Tb~(3+)掺杂硅酸盐玻璃发光性能的影响

研究了(Gd3+,Ce3+/Ce4+,Eu3+)对Tb3+掺杂硅酸盐玻璃发光性能的影响.结果表明:Tb3+掺杂硅酸盐玻璃可以发出弱蓝光(400～460 mm)和较强的绿光(480～600mm).Gd3+对Tb3+的发光起敏化作用,可提高TB3+掺杂硅酸盐玻璃的发光强度.在空气中熔制的玻璃中Ce3+和Ce4+同时存在,Ce3+对Tb3+发光起敏化作用;而Ce4+对Tb3+发光起淬灭作用.由于Ce4+比例比较高,CeO2加入导致TB3+发光强度降低,同时也缩短了Tb3+发光余辉.加入Eu2O3时,Eu3+自身发光分散了激发Tb3+发光的能量,使Tb3+的特征发射强度降低.     

Bi_4Ge_3O_(12):TR(TR=Pr,Eu,Ce)晶体的吸收和发光光谱

测量了Bi_4Ge_3O_(12)(BGO):Pr、Eu和Ce的吸收、激发和发光光谱。掺杂BGO吸收和激发带相应于pr~(3+)、Eu~(3+)和Ce~(3+)离子特征跃迁。Xe灯中不同波长激发所得到掺杂BGO的发光光谱可通过Bi~(3+)心和掺杂材料之间能量传输过程加以解释。Bi~(3+)心400—600mm发射强度因受到Ce杂质影响变弱,这现象在高Ce浓度晶体里更为显著。     

Ce,Tb:YAG单晶的生长及光谱性能

采用提拉法生长了白光LED用的Ce和Tb共掺杂YAG(Ce,Tb:YAG)单晶。通过X射线粉末衍射分析了晶体样品的晶相结构,通过吸收光谱、激发和发射光谱对晶体的发光特性进行了表征。结果表明:所生长的单晶为立方晶相的YAG结构;在波长为460nm蓝光激发下,得到了发光中心位于546nm处的宽发射峰,较Ce:YAG单晶有明显的红移。同时,对不同厚度的晶体切片的光电参数进行了研究,发现厚度为0.5mm的晶体切片的光电参数最好。     

镥铝石榴石晶体的性能及其应用

镥铝石榴石(LuAG)晶体是一种性能优异的激光和闪烁基质材料,具有广泛的应用前景.本论文主要综述了LuAG晶体的结构、晶体的物理化学性能、晶体的存在形式及制备技术,并阐述了稀土掺杂LuAG晶体的发光机理、闪烁性能及其潜在的应用.     

Gd_(3(1-x))Al_5O_(12)∶RE_(3X)分立材料芯片制备及发光性能研究

将组合材料芯片技术中四元组合法应用于新型发光材料Gd3(1-x)Al5O12∶RE3X的RE激活剂和敏化剂种类优选.由Gd3Al5O12基体材料芯片获得如下的研究结果:1)在紫外激发下(254 nm)Gd3(1-x)Al5O3∶Eu3x材料具有红色荧光性能;2)Pr(n(Pr)∶n(Eu)<1∶10)、Ce(n(Ce)∶n(Eu)<1∶10)共掺杂时会降低发光强度.光谱分析表明:Pr、Ce能级嵌入,使得激活剂和敏化剂发生共振能量传递,是Gd3Al5O12∶Eu(简称为GAG∶Eu)发光效率降低的主要原因.筛选结果得到柠檬酸盐硝酸盐溶胶凝胶法制备粉体筛选实验结果验证.实验结果表明组合法在发光材料开发上具有高效性.     

Nd:GGG晶体的体缺陷研究

本文从宏观和微观上研究了Nd:GGG晶体的体缺陷,发现Nd:GGG晶体的体缺陷主要包括开裂、沉积物、空洞和包裹物等.扫面电镜及能谱分析结果表明,空洞中的物质分别为[Gd(Nd)]4Ga2O9、[Gd(Nd)]3GaO6 和[Gd(Nd)]GaO3.包裹物的主要是组分是Ga2O3,是由于晶体生长过程中原料挥发通过固-液界面进入晶体而形成的.     

石榴石闪烁材料的研究进展

稀土离子掺杂的石榴石闪烁材料是20世纪90年代以后发展出的新型氧化物闪烁体。以Ce~(3+)为发光中心的YAG与LuAG晶体是性能优良的闪烁体,具有纳秒级快衰减、高光产额等特性。而Pr~(3+)为发光中心的LuAG单晶以其更快的衰减时间,被认为是下一代的TOF-PET探测器用的关键材料之一。在此基础之上,由于YAG与LuAG陶瓷制备温度较低,有利于减少基质中的反位缺陷,从而实现对闪烁性能优化。而近年来,"缺陷工程"与"能带工程"两种新思想的提出,对石榴石单晶与陶瓷的优化提出新的思路,从而石榴石闪烁材料性能得到进一步提升。本文综合评述了石榴石单晶与陶瓷闪烁体的研究进展,着重介绍"缺陷工程"和"能带工程"两种思想在石榴石体系闪烁材料优化中的应用,最后对其发展前景进行了展望。     

CaF2掺杂钨酸铅晶体的生长与闪烁性能

采用坩埚下降法生长了CaF2掺杂钨酸铅(PbWO4,PWO)晶体,研究了掺杂对PWO晶体的透射光谱、X射线激发发射谱和光产额等发光性能的影响.结果表明:与未掺杂PWO晶体相比,CaF2掺杂的PWO晶体在320～360nm的透过率提高了35%;X射线激发发射强度和光产额比未掺杂PWO晶体高出1倍左右.CaF2掺杂引入了新的发光中心(WO3-F),被认为是导致PWO晶体发光增强的原因.     

石榴石闪烁材料的研究进展EI北大核心CSCD

稀土离子掺杂的石榴石闪烁材料是20世纪90年代以后发展出的新型氧化物闪烁体。以Ce^3＋为发光中心的YAG与LuAG晶体是性能优良的闪烁体,具有纳秒级快衰减、高光产额等特性。而Pr^3＋为发光中心的LuAG单晶以其更快的衰减时间,被认为是下一代的TOF-PET探测器用的关键材料之一。在此基础之上,由于YAG与LuAG陶瓷制备温度较低,有利于减少基质中的反位缺陷,从而实现对闪烁性能优化。而近年来,＂缺陷工程＂与＂能带工程＂两种新思想的提出,对石榴石单晶与陶瓷的优化提出新的思路,从而石榴石闪烁材料性能得到进一步提升。本文综合评述了石榴石单晶与陶瓷闪烁体的研究进展,着重介绍＂缺陷工程＂和＂能带工程＂两种思想在石榴石体系闪烁材料优化中的应用,最后对其发展前景进行了展望。     

Ce:LuAlO3晶体的热稳定性研究

铈掺杂铝酸镥(Ce:LuAlO3)晶体是一种具有钙钛矿结构的新型无机闪烁体.用提拉法试图从n(Lu2O3):n(Al2O3)=1:1的熔体中生长Ce:LuAlO3晶体.实验表明:在缓慢结晶条件下得到的不是Ce:LuAlO3晶体,而是镥铝石榴石[Lu3Al2(AlO4)3].只有急速降温才能够获得Ce:LuAlO3晶体.退火和差热分析表明:Ce:LuAlO3晶体只存在于高温条件下,当温度下降时,它会分解成Lu3Al2(AlO4)3,Lu4Al 2O9和Lu2O3.造成LuAlO3晶体在低温下结构不稳定的原因是Lu离子的半径太小,它只适应于配位数是8的石榴石结构,只有在高温下才能适应配位数是12的钙钛矿结构.     

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。