N和硫属元素掺杂及共掺杂TiO_2第一性原理计算

采用密度泛函理论(DFT)计算了N、S、Se和Te掺杂及共掺杂金红石TiO2的电子结构。针对DFT方法存在对过渡金属氧化物带隙能的计算结果与实际值严重偏离的缺陷,采用DFT+U(Hubbard系数)方法对掺杂体系的电子结构进行了计算。优化结构的结果表明,掺杂造成二氧化钛的体积膨胀和晶格畸变很明显。相比较于其他元素而言,Te更难掺杂进二氧化钛中是由于其大的原子半径和较大的取代能。能带总态密度图和分态密度图的分析表明,Ti 3d和O 2d轨道与N 2p、S 3p、Se 4p和Te 5p强烈地杂化在一起。与S、Se、Te单掺杂后带隙能比较,由计算的结果(S:2.43;Se:2.42;Te:2.46)可以看出,N/S、N/Se和N/Te共掺杂能明显地改善材料的电子结构及带隙。DFT+U计算结果与实验测量结果较好地吻合。     

Co-C共掺金红石相TiO_2光学性质的第一性原理研究

基于密度泛函理论第一性原理研究了C、Co单掺杂以及Co/C共掺杂金红石相TiO_2的电子结构和光学性质,并探究了Co/C共掺杂时C原子替换不同位置O的两种原子位形(C-1和C-2)对TiO_2结构和性能的影响。结果表明:单掺Co和单掺C均会改变金红矿相TiO_2的能带结构和电子态密度;掺杂Co能有效减小TiO_2的禁带宽度。Co/C共掺杂的2种位形(Co/C-1、Co/C-2)的光谱吸收均优于Co、C单掺杂;当掺杂Co与C的位置互为次近邻关系(即位形Co/C-2)时,得到的带隙最小,其带隙宽度为1.740 e V。Co/C-2共掺杂带隙中存在4条杂质能级,其中2条来自于Co-3d态,另外2条来自于C-2p态;共掺后其带隙减小是C-2p态形成的杂质能级向价带移动的结果。Co/C-2共掺杂体系具有红移范围最广、吸收强度最大的光谱响应,增强了金红石相Ti O2的光吸收性能。     

N掺杂锐钛矿二氧化钛光响应红移的模拟计算

利用密度泛函理论(DFT),采用平面波超软赝势方法,模拟计算了掺N锐钛矿相TiO2对能隙、Fermi能级、态密度的影响,以探讨其可见光活性的机理。计算结果表明:表面HOMO和LUMO分别主要由Ti的3d轨道和O、N的2p轨道构成,掺杂出现的N2S态增加了N掺杂的稳定性。并发现N掺杂从两个方面使TiO2材料的带隙变窄:一为N掺杂使Fermi能级移入价带,使带隙变窄;二为在价带的上方引入了独立的能级,在导带下方引入一个宽为0.9 eV左右的能带,这两个掺杂能级使其禁带减小。     

Cu、N共掺杂锐钛矿型二氧化钛的理论研究

采用基于密度泛函理论(DFT)框架下的第一性原理平面波赝势(PWPP)方法,模拟计算了Cu、N共掺杂锐钛矿TiO2,讨论了Cu掺杂、N掺杂、Cu、N共掺杂对锐钛矿TiO2的晶体结构、能隙、态密度等的影响.结果表明Cu、N共掺杂锐钛矿TiO2晶体后,导带主要由N-2p和Ti-3d轨道上的电子构成,价带主要由O-2p和Cu...     

高氯酸铵电子结构第一性原理研究

基于密度泛函的第一性原理,分别运用局域梯度近似泛函(LDA)和广义梯度近似泛函(GGA)对NH4ClO4晶体结构进行了优化,分析了NH4ClO4的能带结构、态密度、Mulliken布居和电荷密度。结果表明,NH4ClO4是能隙值为5.517eV的绝缘体;导带部分主要由O-2p和Cl-3p轨道构成,价带部分由晶体内各原子轨道构成。NH4ClO4属于典型离子晶体,离子基团中心原子N与Cl采用sp3杂化轨道,分别与H和O原子结合形成共价键,晶体内存在弱氢键N-H…O。     

Gd2O2S电子结构及光学性质的第一原理研究

利用基于密度泛函理论的第一原理方法研究了Gd2O2S的电子结构及光学性质.能带结构分析表明:Gd2O2S是一种间接带隙的半导体材料,其间接带隙值为3.22 eV,且价带顶和导带底分别位于G点和M点.态密度计算表明价带顶部由O2p和S 3p态杂化而成,导带底部主要由Gd 5d态构成.在对带隙进行1.15 eV的剪刀修正后,通过第一原理方法研究了Gd2O2S的光学性质.计算并分析了Gd2O2S的介电函数、复折射率、吸收系数和透光率.其中,静态折射率的计算值与实验值吻合得很好,Gd2O2S在可见到红外区的理论透光率的计算值为76.5％.     

C掺杂对NaNbO3材料性质影响的原理研究

采用基于密度泛函理论的原理方法研究了纯NaNbO3和C掺杂NaNbO3的能带结构、态密度与吸收光谱。计算结果表明纯NaNbO3的价带主要由O 2p和Nb 4d电子占据;导带则主要由Nb 4d轨道构成;C掺杂NaNbO3后在禁带中形成了三条由C 2p轨道构成的杂质能级且费米能级通过杂质能级;纯NaNbO3仅在紫外光区有较强的光吸收;C掺杂NaNbO3的光吸收扩展了可见光区。     

N-Al/TiO2催化剂的制备及可见光降解染料

采用溶胶-凝胶法分别制备了N、Al单掺杂与N、Al共掺杂的TiO_2复合材料,考察了4种催化剂在可见光下对染料甲基橙、亚甲基蓝、罗丹明B的光降解效率。采用XRD、SEM、XPS、UV-Vis DRS、N2吸附-脱附手段对催化剂进行表征和评价。结果表明:N、Al共掺杂后的Ti O2骨架晶型仍保持为锐钛矿型,比表面积增加,团聚现象略有减少,且N、Al共掺杂TiO_2催化剂在可见光下对甲基橙的降解效果最佳,脱色率可达70%左右。     

CuInTe_2的电子结构、晶格振动及热电性质

使用第一性原理研究了黄铜矿型CuInTe_2材料的电子结构、晶格动力学和热电输运性质。从电子结构分析可知,价带顶由3条重带组成,空穴有效质量较大,表明CuInTe_2有望成为潜在的p型热电材料。Cu、Te原子在价带顶有效杂化,成为主要的电输运通道。晶格动力学研究表明可以在Cu、In或Te原子位置引入结构缺陷,增加低频区域声子散射降低晶格热导率。不同温度、载流子浓度下的热电输运性质表明,在900 K、载流子浓度为4.7×10~(19)cm~(–3)时,p型CuInTe_2的热电优值达到1.6,是一种极具发展潜力的高温热电材料。     

N掺杂6H-SiC电子结构的第一性原理计算

采用基于密度泛函理论的第一性原理平面波赝势方法,对本征6H-SiC和Si空位、C空位、N掺杂6H-SiC的电子结构及磁性进行了计算。计算结果表明:本征6H-SiC和单一的N掺杂6H-SiC均没有磁性,但可以通过Si空位的引入产生自旋极化。在N和Si空位共掺杂6H-SiC的结构中,Si空位近邻的C原子自旋向上与自旋向下的态密度图明显不对称,主要是由与Si空位近邻的C-2p轨道的自旋极化引起的。N和2个Si空位共掺杂6H-SiC的结构呈现反铁磁性。     

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。