有机物对低温超强碱法制备纳米四方多晶氧化锆粉体性能的影响

利用低温超强碱法制备出了纳米四方多晶氧化锆粉体。为改善该粉体分散性较差、氧化钠含量较高的缺点 ,用有机物对粉体进行了表面改性处理 ,采用X射线荧光光谱、X射线衍射、透射电镜等对粉体性能进行了分析。结果表明 ,采用无水乙醇和柠檬酸铵对粉体进行改性处理 ,使得粉体粒度均匀、分布变窄 ,形态近球形 ,其中柠檬酸铵的处理效果尤为显著 ,使粉体平均粒径从 0 .6 9μm减小到 0 .5 4μm ;进一步的高分辨像分析结果表明 ,粉体颗粒多由 2～ 3个大小为 2 0～ 30nm的单晶组成 ,较大的团聚体较少 ,因此有机物对粉体的表面改性处理有利于获得分散性好、粒度均匀的高质量纳米氧化锆粉体。     

丙烯酸聚合改性氮化硅粉体的研究

为制备高固相含量氮化硅悬浮液,研究了不同分散剂（柠檬酸铵、四甲基氢氧化铵、聚丙烯酸铵和丙烯酸）对氮化硅粉体的表面改性作用。结果发现,柠檬酸铵、四甲基氢氧化铵、聚丙烯酸铵不能有效吸附于氮化硅粉体表面而改变粉体的表面特性;而丙烯酸聚合过程中链自由基的较高活性使聚丙烯酸分子链吸附于氮化硅颗粒表面,氮化硅粉体的等电点从pH≈4．3降低到pH≈21,通过这种表面改性方法提高了氮化硅粉体在水中的分散特,制备出了固相体积分数为50％的氮化硅悬浮液。这种表面改性方法不改变氮化硅粉体的化学组成,有利于制备氮化硅基陶瓷时化学成分及相组成的准确控制。     

钛酸镍水基浓悬浮体的制备及流变特性研究

测定了超细NiTiO3粉体的ζ-电位,并研究了分散剂聚甲基丙烯酸铵(NH4PAA)的用量对NiTiO3悬浮体粘度的影响。结果表明:超细NiTiO3粉体在水中的等电点约为5.0;悬浮体的粘度与分散剂的用量有关,并得出最佳用量约为粉体质量的0.4wt%;研究了不同水基浓悬浮体的流变特性,成功地制备出体积分数为60vol%的低粘度(0.75Pa·S,剪切速率为50S-1)悬浮体。     

分散剂对氧化锆晶型的影响

以氧氯化锆为原料、尿素为沉淀剂,采用不同表面活性剂为分散剂,制备超细氧化锆粉体。实验研究发现,其他条件相同,采用聚乙二醇和聚乙烯醇作分散剂,所制得的氧化锆粉体以单斜晶为主,同时有一定量的四方晶氧化锆生成,且添加聚乙二醇生成的四方晶氧化锆较添加聚乙烯醇时生成的多;采用Span80作分散剂,明显抑制了四方晶氧化锆的生成,可制得较纯的单斜晶氧化锆粉体。另外,采用不同分散剂所制得的产物颗粒形状不同,用聚乙二醇作分散剂可制得纺锤形氧化锆粉体,而用聚乙烯醇或Span80作分散剂则可制得椭球形氧化锆粉体。     

固态粒子烧结法制备YSZ超滤膜

以硝酸氧锆、硝酸钇为原料采用硬脂酸法制备3mol％钇稳定的氧化锆(YSZ)纳米粉体，X-射线衍射(XRD)分析表明，所制的YSZ粉体为四方晶相，透射电子显微镜(TEM)观察表明，900℃处理2h后YSZ粉体的平均粒径约为20nm。以聚丙烯酸铵(PAANH4)为分散剂，将所制备的纳米YSZ粉体分散后制备成稳定的悬浮液，通过浸浆成膜采用固态粒子烧结法制备YSZ膜，氮气吸附实验表明，YSZ膜的最可几孔直径为87nm。     

分散剂用量和pH值对纳米氧化锆水基浆料稳定性的影响

在氧化锆陶瓷制作过程中采用凝胶注模成型工艺时,为了获得高分散性、低粘度的浆料,试图使用聚丙烯酸铵(PAA-NH4)作为分散剂,主要研究了氧化锆悬浮体的3个指标:Zeta电位、流变学行为、沉降度,在不同p H值和分散剂用量下的变化规律,并分析其影响机理。试验结果表明:PAA-NH4的加入能够明显提高氧化锆浆料的Zeta电位,用氨水调节悬浮体p H为11的情况下,当添加3.0 wt%的分散剂聚丙烯酸铵PAA-NH4时,Zeta电位为负值,达到最小,粘度和沉降高度也均达到最小值,此时,ZrO2水基浆料的分散性、稳定性和流变学行为达到最佳。     

Ni-ZrO2复合电镀工艺的研究

研究了Ni-ZrO2复合镀液体系中微粒与镀液间的相互作用.镀液中的电解质NiSO4和NiCl2对ZrO2纳米微粒在复合镀液中的悬浮稳定性有很大影响.阴极极化曲线表明纳米微粒的加入改变了基质金属电沉积的过程.以高分子聚电解质作为分散剂,利用其在微粒之间形成的空间位阻效应,减弱镀液中离子对微粒的聚沉作用,得到了均匀分散的ZrO2纳米微粒的复合镀镍溶液,并对各种镀层的形貌和硬度进行了分析.     

纳米钛酸钡粉体的分散及水基悬浮体制备

通过测定超重力法制备的纳米钛酸钡悬浮体的Zeta电位和团粒尺寸分布,确定了纳米BaTiO3在水中稳定分散的基本条件,制备了不同体积分数的悬浮体并研究了其流变学特性. 该纳米BaTiO3在水中的等电点约为pH 2.8,加入分散剂PAA-NH4后,颗粒零电点向更低pH值移动;当分散剂用量为干粉量的1.2%(w)时,悬浮体中平均团粒尺寸最小,分散效果最佳. FT-IR分析证明颗粒表面上PAA-NH4的吸附为物理化学吸附. 制备了体积分数高达45%的纳米BaTiO3悬浮体,其流变特性表现为剪切变薄行为,流延成型的BaTiO3陶瓷生坯片具有较高的相对密度(55.4%).     

超细氧化铝水悬浮液分散稳定性研究

阴离子聚电解质分散剂(PAA)使α-Al2O3粉体的等电点降低;超声分散作用改善了分散剂在粒子表面的分布状态,因而使浆料的流变性有明显的改善;离子强度低于0.08mol/L时,浆料的粘度随离子强度提高而增加,稳定性降低.但在0.08～0.12mol/L的范围内,离子强度对浆料粘度的影响不明显;温度对浆料的粘度有显著的影响.分散剂添加量低于饱和吸附添加量时,温度升高,浆料粘度增加,稳定性下降.而在分散剂添加量高于饱和吸附添加量时,温度升高,粘度则降低.     

非均匀沉淀法制备黑色氧化锆陶瓷

以Y-TZP（氧化钇稳定四方多晶氧化锆）为原料、硝酸锰和硝酸铝为着色剂、PEG2000（聚乙二醇2000）为分散剂,采用非均匀沉淀法制备着色剂/氧化锆复合粉体,经成型、烧结后得到黑色氧化锆陶瓷。采用X射线衍射,扫描电子显微镜、X射线荧光分析和透射电子显微镜等对复合粉体和陶瓷的结构和性能进行表征,结果表明：着色剂/氧化锆...     

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.