球形氧化锆的湿法制备过程研究

以氯氧化锆和碳酸氢铵为原料，采用连续反应沉淀法制备了微米级球形氧化锆前驱体，此前驱体在500℃下于空气气氛中煅烧2h得到球形氧化锆粉体。探讨了锆盐溶液浓度、加料速度、pH、反应时间对粉体颗粒粒径大小及其分布的影响。经SEN，XRD，TG—DSC和激光粒度测试仪分析，结果表明在最佳工艺条件下制备的氧化锆前驱体颗粒呈球形，分散性好，粒径分布在8—18μm。     

低温水热法制备纳米氧化锆粉体

本文以ZrOC12为原料、NH3·H2O为沉淀剂、CaC12为稳定剂,采用交叉喷淋法制备氧化锆前驱体,通过改变反应釜内前驱体浓度、矿化剂NaOH的加入及矿化剂NaOH浓度,采用低温水热法制备纳米氧化锆粉体.结果表明:反应釜内前驱体浓度降低有利于提高粉体的结晶度,矿化剂NaOH的加入可有效降低水热反应温度.当反应温度为110℃、保温时间2h、反应釜内前驱体的浓度为0.25 mol/L、矿化剂NaOH浓度为1 mol/L时,可制备平均粒径为26 nm的四方相氧化锆粉体.     

固相研磨法制备纳米二氧化锆及其机理初探

通过在研钵内研磨，使固相的氧氯化锆分别与固相的氢氧化钠或六次甲基四胺或氢氧化钠和碳酸锂的混合研磨物发生反应，生成纳米二氧化锆粉体的前驱体氢氧化锆，然后中温(400℃)烧结制得纳米二氧化锆粉体，粒径约为10nm。并研究了不同沉淀剂、不同干燥方式对产物的影响。该法既节省能源又不污染环境，是一条绿色合成方法，具有工业化生产潜力。     

聚乙二醇分子量对氧化锆粉体粒径的影响研究

为了控制纳米氧化锆粉体的粒径并降低制备成本,以不同分子量(MW)的聚乙二醇(PEG)作为分散剂,采用辅助溶胶-凝胶法制备纳米氧化锆粉体。利用傅里叶变换红外光谱对凝胶体进行了表征,采用激光粒度仪、X射线衍射仪和扫描电镜对纳米氧化锆粉体进行表征。实验结果证明,不同分子量的PEG具有不同的碳转化率,分解所得的碳颗粒所形成的碳隔离作用有助于控制粉体的团聚,纳米氧化锆的粒径与分散剂的碳转化率成反比。     

溶胶-胶水热合成法制备纳米CoAl2O4粉体

以仲丁醇铝和硝酸钴为原料,用溶胶-凝胶水热合成法制备了纳米CoAl2O4粉体,探讨了水热合成中前驱体的制备工艺条件,并用X射线衍射和扫描电镜等手段分析了水热系统中反应温度、反应时间对纳米CoAl2O4粉体的形成以及形貌的影响.结果表明:前驱体在250℃的水热系统中反应24 h,能制备出较纯净、结晶完整、粒度均匀、粒径小、尖晶石结构的纳米CoAl2O4粉体,其平均粒度约为50～60nm.     

室温固相合成球形氧化锆纳米晶体

用碳酸铵与氯氧化锆作原料，在适量表面活性剂聚乙二醇辛基苯基醚（OP乳化剂）的存在下，在室温下充分混合研磨得到反应混合物，洗去其中的可溶性无机盐后烘干得到前驱体，前驱体经热分解即可得到球形氧化锆纳米晶体。基于均匀设计、逐步回归分析及最优化计算，对纳米氧化锆的固相合成条件进行优化，所获取的优化工艺条件为：氯氧化锆取10mmol时，反应物碳酸铵与氯氧化锆的物质的量比等于1．4：1；表面活性剂用量40μL；研磨时间40min；热分解温度500℃及热分解时间120min。在此条件下合成的氧化锆晶体粉末颗粒均匀、团聚弱，其一次粒子的平均粒径约20nm，收率为95％。     

草酸铵沉淀法制备纳米氧化钕研究

以硝酸钕、草酸铵为原料,六偏磷酸钠为分散剂,采用沉淀法制备纳米氧化钕前驱体,将前驱体在空气中焙烧制备纳米氧化钕粉体。研究了反应温度、物料浓度等因素对粉体的影响,用激光粒度仪测得样品的粒度分布,用X射线衍射和扫描电镜对样品进行表征。实验表明,在最佳条件下可以制得平均粒径为100 nm的片状氧化钕粉体。     

ZrO2前驱体ZrO(OH)2的制备和表征

本报道了一种制备氧化锆前驱体的方法,并用XRD、DTA和SEM等手段鉴定了描述了这种前驱体的粉体特征及其在热处理中所发生的成分相态变化,实验表明用这种方法制备的ZrO(OH)2凝胶是制备氧化锆的一种经济实用的前驱体。     

草酸铵沉淀法制备纳米氧化钇研究

以氧化钇、浓硝酸为原料,草酸铵为沉淀剂,十六烷基三甲基溴化铵为分散剂,采用草酸铵沉淀法制备纳米氧化钇前驱体,将前驱体在空气中焙烧制备纳米氧化钇粉体。用差热-热重分析确定了前驱体分解温度,用 X射线衍射和扫描电镜对样品进行表征,用激光粒度仪测量不同反应物物质的量比所得产品的粒度分布,得到制备纳米氧化钇最佳条件。实验表明,在最佳条件下可以制得平均粒径为40 nm的氧化钇粉体,其形貌为椭球形。     

纳米ATO粉体的制备及性能研究

采用非均相成核法制备了粒径为数十纳米的ATO导电粉体,运用XRD,TEM,粉体表面zeta电位测定等手段对粉体进行了表征.结果表明:粉体均为四方金红石结构,粒径在20nm左右.前驱体的等电点在pH=1～2之间,适当调整反应pH值,可制得分散均匀的纳米粉体.     

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.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

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.