纳米SiO2/TiO2复合粉体的制备及表征

以Na2SiO3为原料,采用非均匀成核法在纳米TiO2基体上制备了SiO2表面保护膜层,通过红外光谱、X射线光电子能谱、扫描电镜、粒径测量、BET比表面积测量分析,证实纳米TiO2颗粒表面包覆了一层均匀致密的SiO2纳米膜,而且两者是以化学键合方式结合在一起。分散性能测试表明:纳米SiO2/TiO2复合粉体的分散性能明显提高。     

SiO_2复合磁性纳米粒子的合成及表面性质的研究

采用溶胶凝胶法合成具有快速磁场响应能力的SiO2复合磁性纳米粒子。用表面电位仪研究了不同包覆层厚度对粒子表面性质的影响。用AFM对粒子的表面形貌进行了表征。并考察了不同SiO2包覆层厚度粒子的抗酸性。结果表明生长3层SiO2后复合粒子的表面完全被SiO2所包覆,粒子具有高的磁含量和快速的磁场响应能力,并具有高的抗酸性。     

用二氧化硅表面改性纳米二氧化钛的制备及表征

针对二氧化钛(TiO2纳米颗粒在水性涂料中极易团聚、分散性差的问题,以提高TiO2分散稳定性为目的,用并流中和法,以锐钛矿型纳米TiO2粉体为载体,硅酸钠(Na2SiO3)为包覆剂,用硫酸(H2SO4)调节pH值,成功地在纳米TiO2表面包覆致密的SiO2膜.借助Fourier变换红外光谱(Fourier transform infrared spectroscopy,FTIR)、X射线衍射技术(X-ray diffraction,XRD)和X射线能量散射谱(X-ray energy dispersive spectroscopy,EDS),表征样品的键合情况、相态结构、表面的化学成分,同时测定包覆改性前后的纳米TiO2比表面积和酸溶性.FTIR和EDS结果表明:该包覆方法可行,氧化硅(SiO2)以化学键合的方式沉积在纳米TiO2表面,在包覆层和纳米TiO2颗粒之间的界面上形成了Ti-O-Si键.酸溶实验分析和XRD结果证实:在TiO2纳米颗粒表面包覆了一层致密SiO2膜.比表面测定的结果显示:改性后TiO2的比表面积随质量分数m(SiO2):m(TiO2)增加而减小.     

纳米铝粉表面包覆及活性铝分析研究

铝是重要的金属燃料,纳米铝粉粒径小,表面能高,具有较高活性,在含能材料领域有很高应用价值。但其小尺寸效应使纳米铝表面很容易生成一层氧化铝薄膜,因此纳米铝表面包覆是国内外学者研究的热点。本文概述了近几年纳米铝粉的制备方法和表面包覆改性研究进展,分析了包覆材料、包覆工艺中包覆材料与纳米铝的比例、活性铝质量分数分析研究所取得的成果,指出了包覆纳米铝颗粒在体系中的分散性能、铝的氧化机理以及活性纳米铝质量分数分析将是接下来较长时间的研究主题。     

TiO_2包覆硅灰石填充对PA1010复合材料的影响

以硅灰石为原料,钛酸四正丁酯为包覆剂,采用溶胶-凝胶法制备了一种纳米TiO2包覆硅灰石复合颗粒,并用电子显微镜(SEM),红外光谱仪(FTIR)等对TiO2包覆硅灰石颗粒进行表征。结果表明:硅灰石表面均匀地包覆了一层厚度约为60nm的非晶态纳米TiO2,进而将TiO2包覆硅灰石复合颗粒填充尼龙1010(PA1010)。用差示扫描量热仪(DSC)对填充后复合材料的聚集态结构进行分析后发现,硅灰石表面包覆TiO2膜改善了硅灰石与尼龙基体的界面结合状况,同时对PA1010产生了诱导结晶作用。     

超重力场中纳米TiO2粒子表面包覆Al2O3膜及其表征

基于异相表面成核和撞击流-旋转填料床反应器的微观混合原理,以纳米水合氧化钛(TiO2·nH2O)粒子为固相基体,六水氯化铝溶液为包覆相,采用液相包覆-界面反应的方法在纳米TiO2前体颗粒表面包覆了纳米Al2O3膜,并对超重力场中纳米粒子表面包覆过程进行了初步分析。通过IR、TEM、Zeta电位分析和XRD分析,证实了纳米TiO2前体颗粒表面包覆了一层厚约5nm的致密海绵状膜。IR和XRD谱图表明,在Al2O3纳米膜层和纳米TiO2颗粒之间的界面上形成了Ti—O—Al键,包覆膜层的晶体结构以γ-Al2O3为主的混合晶型。     

片状铝粉表面包覆SiO2薄膜的研究

采用溶胶-凝胶法在片状铝粉表面包覆SiO2薄膜，以改善其耐酸性能。分析了正硅酸乙酯（TEOS）水解一缩聚反应在粒子表面包覆SiO2膜的形成机理，并以此制备了SiO2／AI复合粒子。研究表明，最佳反应条件为：采用并流滴加TEOS、催化剂和蒸馏水的混合液的加料方式，msio2/mAl为20％，水硅比控制在30～50之间。采用IR、SEM、EDS及粒度分析等方法对包覆后的样品进行了分析与表征。     

包覆型CeO_2/SiO_2和CeO_2/聚苯乙烯复合磨料的制备及其化学机械抛光性能

以SiO2和聚苯乙烯(polystyrene,PS)微球为内核,采用液相沉淀工艺制备了具有包覆结构的CeO2/SiO2和CeO2/PS复合颗粒。利用X射线衍射仪、透射电子显微镜、场发射扫描电子显微镜、X射线光电子能谱仪、动态光散射仪和zata电位测定等手段对所制备样品进行了表征。将所制备的CeO2/SiO2和CeO2/PS复合颗粒用于硅晶片热氧化层的化学机械抛光,用原子力显微镜(atomic force microscope,AFM)观察抛光表面的微观形貌、测量表面粗糙度。结果表明:所制备的CeO2/SiO2和CeO2/PS复合颗粒呈球形,粒径在150～200nm,CeO2纳米颗粒在SiO2和PS微球内核表面包覆均匀。包覆的CeO2颗粒与SiO2内核之间形成了化学键结合。CeO2颗粒的包覆显著的改变了复合颗粒的表面电性。AFM测量结果表明:经CeO2/SiO2和CeO2/PS复合磨料抛光后的硅热氧化片表面在5μm×5μm范围内粗糙度值分别为0.292nm和0.180nm。     

纳米银的制备、修饰及与鲱鱼精DNA的作用

采用氧化还原法制备了纳米银粒子,在乙醇溶剂中,纳米银粒子表面成功包覆上了SiO2层.利用透射电镜、紫外可见吸收光谱、荧光光谱对纳米银及包覆结构(Ag为核,SiO2为壳,Ag@SiO2)进行了表征.实验表明:氨水的加入顺序对Ag@SiO2核壳结构具有一定的影响;随着SiO2壳层的不断加厚,纳米银的特征吸收峰红移,吸收强度降低,在本实验中当厚度大于50nm时,特征吸收峰发生蓝移,吸收强度增大.纳米银的发射光谱表明SiO2壳层的包覆使纳米银的发射强度降低.另外,采用光谱法考察了Ag@SiO2纳米粒子与鲱鱼精DNA的相互作用,结果表明:鲱鱼精DNA的吸收光谱及Ag@SiO2的发射光谱无明显变化,初步证明Ag@SiO2纳米粒子具有较好的生物兼容性,这为Ag@SiO2纳米粒子的毒理及其在生物医学上应用提供了重要依据.     

聚丙烯基纳米SiO2复合材料的流变性能研究

采用普通毛细管流变仪和高压毛细管流变仪，通过测定流变性能，研究不同表面处理工艺对PP基纳米SiO2复合材料的团聚，分散和界面性能的影响。结果表明，纳米SiO2采用偶联剂处理并包覆长链分子型分散剂后，可增加界面层厚度，形成相间缓冲层，由此增大纳米颗粒与颗粒间的距离，使纳米颗粒团聚体变得松散，摩擦阻力有所下降，熔体流动性损失减少，PP基纳米SiO2复合材料的熔融流动性基本随纳米SiO2用量的增加而下降；当纳米SiO2质量分数约为3%时，该复合材料的熔体流变性能近似于纯PP，并在挤出或注射成型的剪切速率范围内加工流动性未明显下降。     

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.     

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.     

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.     

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.