AIN在SiC—AIN—Y2O3复相陶瓷中的作用

氮化铝相在ＳｉＣ－ＡＩＮ－Ｙ２Ｏ３复相陶瓷中起着至关重要的作用。在２０５０℃高温时，ＡＩＮ颗粒表面发生固相蒸发现象，并聚集到ＳｉＣ颗粒周围最终形成固溶体，改善了ＳｉＣ颗粒周围最终形成固溶体，改善了ＳｉＣ陶瓷的晶界结构，使该复相材料具有良好的机械性能，其室温抗折强度为６１０ＭＰａ，这一强度可持续至１４００℃高温，断裂韧性达到８．１ＭＰａ．ｍ＾１／２。     

Si_3N_4－ZrO_2陶瓷中ZrN的生成及其对性能的影响

研究了ＺｒＮ在Ｓｉ＿３Ｎ＿４－ＺｒＯ＿２复相陶瓷中的形成及其对材料性能的影响，结果表明：在１．５ＭＰａＮ２气压烧结条件下，ＺｒＮ的形成温度约为１６００℃，提高Ｎ＿２的压力有利于抑制ＺｒＮ的生成，以稳定的ｔ－ＺｒＯ＿２加Ｓｉ＿３Ｎ＿４基体中，对抑制ＺｒＮ的生成有明显作用。当复相陶瓷中生成一定量的ＺｒＮ时，力学性能明显下降，而ＺｒＯ＿２分布均匀且以ｔ－ＺｒＯ＿２，ｃ－ＺｒＯ＿２形式存在时，复相陶瓷具有较高的强度（７４０ＭＰａ）和断裂韧性（８．８ＭＰａ·ｍ￣（１／２））。     

AIN在SiC－AIN－Y_2O_3复相陶瓷中的作用

氮化铝（ＡＩＮ）相在ＳｉＣ－ＡＩＮ－Ｙ＿２Ｏ＿３复相同瓷中起着至关重要的作用。在２０５０℃高温时，ＡＩＮ颗粒表面发生固相蒸发现象，并聚集到ＳｉＣ颗粒周围最终形成固溶体，改善了ＳｉＣ陶瓷的晶界结构，使该复相材料具有良好的机械性能，其室温抗折强度为６１０ＭＰａ，这一强度可持续至１４００℃高温，断裂韧性达到８．１ＭＰａ·ｍ￣（１／２）。     

SiCw增韧Al2O3／TiB2陶瓷复合材料的研究

根据对晶须与基体材料的热胀失配的分析，计算得出了Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣｗ三元复合材料中ＳｉＣｗ的临界体积分数。采用ＴｉＢ２颗粒增韧和ＳｉＣｗ增韧两种途径来改善Ａｌ２Ｏ３的脆性，得到此复合材料的抗弯强度为７４０ＭＰａ，断裂韧性为７．７ＭＰａ·ｍ＾１／２。分析表明：当ＳｉＣｗ含量大于临界体积分数时，强度大幅降低的主要原因是由于致密度的降低和热残余拉应力的增大。     

Si3N4—ZrO2陶瓷中ZrN的生成及其对性能的影响

研究了ＺｒＮ在Ｓｉ３Ｎ４－ＺｒＯ２复相陶瓷中的形成及其对材料性能的影响，结果表明：在１．５ＭＰａ Ｎ２气压烧结条件下，ＺｒＮ的形成温度约为１６００℃，提高Ｎ２的压力有利于抑制ＺｒＮ的生成，以稳定的ｔ－ＺｒＯ２加入Ｓｉ３Ｎ４基体中，对抑制ＺｒＮ的生成有明显作用。当复相陶瓷中生成一定量的ＺｒＮ时，力学性能明显下降，而ＺｒＯ２分布均匀且以ｔ－ＺｒＯ２，ｃ－ＺｒＯ２形式存在时，复相陶瓷具有较高的强度（７４     

GPSZrO_2-Si_3N_4复合材料性能的研究

本文研究了ＧＰＳＺｒＯ２－Ｓｉ３Ｎ４复合材料的烧结性能、相组成、显微结构和力学性能。ＺｒＯ２－Ｓｉ３Ｎ４复合材料在１７７０～１８００℃,氮气压力分别为１ＭＰａ,２ＭＰａ,３ＭＰａ下烧成,获得相对密度＞９５％烧结体。实验结果表明：少量的工业ＺｒＯ２对氮化硅有助烧作用,增大氮气压力有利于改善氮化硅陶瓷材料的烧结性能和力学性能;ＺｒＯ２可提高氮化硅基体的断裂韧性,在３ＭＰａ下烧成条件下,添加１５％ＺｒＯ２的Ｓｉ３Ｎ４复合材料断裂韧性可达８．０８ＭＰａ．ｍ１／２,与基体相比提高２１．５％,第二相粒子增韧和微裂纹增韧为主要增韧机理。     

反应合成AlN／TiB2复相陶瓷及残余应力分析

采用ＸＲＤ法研究了ＴｉＨ２，Ａｌ及ＢＮ反应过程中物相的生成机理，发现在不同温度下存在ＴｉＡｌ３，ＴｉＮ，－α－Ａｌ２Ｏ１等过渡相，但最终只有ＡｌＮ和ＴｉＢ２两相存在，并结合热力学分析，认为合成ＡｌＮ／ＴｉＢ２的反应温度应在１７００℃以上。通过反应热压法制备出了ＡｌＮ／ＴｉＢ２复相陶瓷，材料的三点弯曲强度为５３９ＭＰ，ＫＩＣ为５．０５ＭＰａ．ｍ＾１／２。     

Al2O3陶瓷基体中原位生成TiB2和Ti（C,N）研究

采用原位反应法结合热压工艺制备Ａｌ２Ｏ３－ＴｉＢ２－Ｔｉ（Ｃ，Ｎ）复相陶瓷，用ＴｉＯ２，Ｂ４Ｃ，ＢＮ，Ａｌ及Ａｌ２Ｏ３为原料，通过组成设计可以制备出不同相组成及碳氮比的复相陶瓷。由ＳＥＭ及ＴＥＭ发现在Ａｌ２Ｏ３晶粒中分布着亚微米至微米级的近圆形Ｔｉ（Ｃ，Ｎ）颗粒，而在ＴｉＢ２晶粒中分布着纳米级的板状Ｔｉ（Ｃ，Ｎ）晶体，并对这种显微结构的形成机理及化学反应过程作用初步分析。     

TiB2／SiCw复合材料增韧机理的微观分析

在ＴｉＢ２／ＳｉＣｗ基体中加入适量的ＳｉＣｗ可以明显地提高其断裂韧 性ＫＩＣ，其它机械性能也有不同程度的改善。ＳＥＭ、ＴＥＭ微观分析表明：在具有较高ＫＩＣ值的ＴｉＢ２／ＢｉＣｗ陶瓷复合材料中，ＳｉＣｗ与ＴｉＢ２晶粒之间有较适宜的界面结合，两相之间未发现有明显的界面化学反应用，当该复合材料发生断裂时，其内部出现晶须拔出，裂纹桥连，裂纹偏转三种增韧机制。     

C-B4C-SiC与Ti组分的原位反应及热压烧结

以炭黑、炭纤维、Ｂ４Ｃ、ＳｉＣ、Ｓｉ、ＴｉＯ２和ＴｉＣ为原料制备了不同ＴｉＯ２和ＴｉＣ含量的炭／陶复合材料,采用原位合成及热压技术研究了不同ＴｉＯ２和ＴｉＣ含量对多组分炭／陶复合材料的组成、结构和性能的影响。在烧结过程中ＴｉＯ２和ＴｉＣ与Ｂ４Ｃ反应原位生成ＴｉＢ２,Ｓｉ和ＴｉＯ２分别与Ｃ反应生成ＳｉＣ和ＴｉＣ,这些陶瓷相的生成对提高炭／陶复合材料的力学性能有显著作用。加入ＴｉＯ２能使炭／陶复合材料在较低的温度下实现致密化烧结,获得了抗弯强度达４３０ＭＰａ的炭／陶复合材料     

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.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.     

Highly moisture-proof polysilsesquioxane coating prepared via facile sol-gel process

A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by ¹H MAS NMR. For direct comparison purposes, an SiO₂ coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N₂ absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals.     

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.