Ce:YAG系列荧光晶体的发光特性及其在发光二极管中的应用

稀土Ce~(3+)离子掺杂的钇铝石榴石(Ce:Y_3Al_5O_(12),Ce:YAG)晶体,其独特的光谱学特征非常适合用于460 nm蓝光激发的白光发光二极管(LED)。因而,基于Ce:YAG单晶,尤其是基于能量传递原理构建的YAG系列单晶在白光LED领域中将会成为一个备受关注的荧光材料。简要评述了近年来蓝光(460 nm)基白光LEDs用单晶系列的研究进展,重点阐述了基于Ce:YAG单晶的单掺杂体系,以及基于能量传递原理构建的双掺杂及三掺杂等单晶荧光材料在白光LED中的研究进展,展望了该材料在白光LED中的应用前景。     

白光LED用Ce,Re∶YAG单晶的研究进展

通过Ce,Re∶YAG单晶替代荧光粉与蓝光芯片产生白光是近几年发展起来的新方法.本文对Ce,Re∶YAG单晶的主要制备方法进行了说明.综述了目前国内外用于白光LED的Ce∶YAG系列单晶的研究进展,并对其研究成果进行了分析,给出了部分具有代表性的荧光光谱图.最后对晶片式白光LED的发展前景进行了展望.     

SPS烧结制备新型荧光玻璃材料

以实验室自制SiO2粉体和商用Ce∶YAG荧光粉为玻璃原料,采用放电等离子体烧结（SPS）技术,在1 200℃保温2 min烧结得到有望用于白光LED封装的Ce∶YAG荧光玻璃。用X射线衍射仪（XRD）、荧光光谱（PL）等方法对制备获得的荧光玻璃样品进行表征。结果显示,烧结并没有破坏Ce∶YAG荧光粉的晶体结构,且荧光玻璃主体相仍为玻璃体,该荧光玻璃在460nm具有强吸收峰,在此波长激发下发射出530 nm左右的黄光。研究结果表明,本实验制备的Ce∶YAG荧光玻璃是一种具有重要应用前景的LED封装用新型荧光材料。     

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。     

高显色白光LED用YAG：Ce^3＋，Ln^3＋荧光粉的研究进展

综述了YAG：Ce荧光粉的制备方法,着重介绍了高显色白光LED用YAG：Ce^3＋,Ln^3＋（Ln=Sm,Pr,Gd,Tb）荧光粉的最新研究进展和发光性能。YAG：Ce^3＋,Ln^3＋荧光粉的发射谱带发生红移,或在红光区增加尖锐的红光发射峰,从而提高了白光LED的显色性能。     

微波辅助沉淀法荧光粉体的制备及其用于白光LED的研究

本项目拟采用微波辅助共沉淀法制备Ce:YAG荧光粉体,接着通过高温真空烧结得到了Ce:YAG透明陶瓷。利用透明荧光陶瓷进行LED封装,使其在蓝光LED芯片照射下产生白光,实现"蓝光芯片+Ce:YAG透明荧光陶瓷"发光和外壳一体化。通过XRD、SEM等手段对粉体和陶瓷进行了表征和研究,优化纳米粉体制备条件和陶瓷烧结工艺,制备性能优良的透明荧光陶瓷。     

Ce:YAG微晶玻璃制备及光谱性能

在Y2O3-Al2O3-SiO2-Li2O-K2O-Na2O基质玻璃中掺入Ce,经过不同温度热处理,制备出白光LED用Ce∶Y3Al5O12(Ce∶YAG)微晶玻璃.利用X射线衍射仪、X射线光电子能谱仪、场发射扫描电子显微镜、荧光光度计等方法对微晶玻璃的晶相、所掺杂Ce的价态、微观形貌以及光谱性能进行了研究.结果表明:...     

稀土荧光高分子的制备及其荧光性能研究

以黄色Y3Al5O12:Ce、红色Ca Al Si N3:Eu发光材料和有机硅树脂为原料,通过模压法制备了不同Y3Al5O12:Ce含量的稀土荧光高分子,并进一步封装出白光LED。采用X射线衍射、荧光光谱仪、高精度快速光谱辐射计对荧光高分子样品和白光LED的晶型结构、荧光特性、波长转换效率、发光效率、光通量等光色参数进行了测试和计算。结果表明:发光材料的混合并未破坏其本身的晶型结构,X射线衍射谱图与标准卡一致;样品具有宽带激发光谱,峰值位于467 nm,发射光谱峰值548 nm,半波宽90.3 nm,适于宽光谱白光LED的制备,其发射强度随着Y3Al5O12:Ce质量分数的增加而提高。样品的波长转换效率与质量分数表现出正相关关系,但由于吸收饱和效应,其增幅逐渐降低。根据所封装白光LED中色坐标点分布和色温的综合分析结果,确定Y3Al5O12:Ce的最优用量为5.66%,对应的白光LED的发光效率为126 lm/W,色温为6 196 K,显色指数为62。不同电流下的光谱变化测试结果表明样品具有电流稳定性。此外,通过加入Ca Al Si N3:Eu,可将白光LED的显色指数提高至81,色温则变化至暖白区的2 726 K。     

掺Nd~（3＋）的［Y（Ca）］_3［Al（Zr）］_5O_（12）石榴石单晶

用激光加热基座法（ＬＨＰＧ）从粉末直接生长单晶光纤并对其光谱作了研究。结果表明：ＬＨＰＧ法生长出来的单晶光纤可替代大块晶体去研究光谱等性能；Ｃａ￣（２＋）和Ｚｒ￣（４＋）等量同时掺入到Ｎｄ：ＹＡＧ晶体中，其吸收谱与Ｎｄ：ＹＡＧ基本相同，但荧光分支比和荧光衰减规律发生显著变化。此外还探讨了Ｃａ￣（２＋），Ｚｒ￣（４＋）影响的原因。     

铈掺杂玻璃陶瓷的绝对光谱功率分布与荧光量子产率

采用直径10in积分球结合CCD(Charge Coupled Device)探测器测试系统,在蓝色半导体发光二极管激发下,对Ce3 掺杂的Y3Al5O12(YAG)玻璃陶瓷的荧光光谱进行表征,实现了以荧光发射特性绝对评价为目的的绝对光谱功率分布测定,为白色LED(Light Emitting Diode)荧光材料发射特性的精确测定提供了一种准确方法。荧光测试系统经标准卤素灯定标,辅助卤素灯校正积分球内环境变化,解析出样品发光的绝对光谱功率分布,并进一步计算出光量子数分布,求得荧光量子产率。实验结果表明,YAG高效玻璃陶瓷片的荧光量子产率高达33.7%,为新型高效LED照明发光材料的研制提供了新的标准和比照。     

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.     

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。     

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.