金辅助化学腐蚀法制备多孔硅及其性能研究

近年来金属辅助化学腐蚀法制备多孔硅逐渐成为研究热点,但该方法存在金属颗粒易团聚、引入模板辅助刻蚀成本高昂等突出问题。为了优化多孔硅的制备技术,降低制备成本,本文研究了基于金颗粒辅助化学腐蚀的多孔硅制备方法。首先采用氯金酸还原法制备了粒径从18～80 nm的带负电荷金颗粒,3-氨基丙基三乙氧基硅烷修饰可以使单晶硅表面带正电荷,通过静电吸附实现了金在硅基底表面均匀、独立的沉积。在含H2O2和HF的刻蚀液中,硅基底被蚀刻成规则的孔状,多孔硅产物膜厚在添加N,N-二甲基乙酰胺作为表面活性剂时达到44. 45μm。此外,刻蚀液组成为ρ=70%(ρ=[HF]/([HF]+[H2O2]))时多孔硅刻蚀速率达到1. 23μm/min,对应的多孔硅/高氯酸钠复合含能材料爆炸光强最大,DSC放热量为1636 J/g。     

多孔硅支撑磷脂双层膜的制备与表征

制备了一种以多孔硅为基底的新型支撑磷脂双层膜,多孔硅具有良好的光反射干涉性能,在多孔硅表面构筑磷脂双分子层膜有望形成一类新型的生物传感器.通过电化学刻蚀法制备了孔径为35～45 nm,孔道深度约为15μm的多孔硅,并用电子显微镜观测了其孔道结构,经原子力显微镜检测,其表面均方根粗糙度(RMSR)仅为0.64nm.用挤出...     

多孔硅形成过程中的晶态转变

采用电化学阳极氧化法,对p型单晶硅施加30 mA/cm~2的恒定电流密度,在40%氢氟酸溶液中和氮气保护气氛下分别极化1、3和5 min,制备不同生长阶段的多孔硅样品,通过表面形貌观测及微观结构表征,获得从单晶硅到多孔硅形成过程所涉及的各种晶态组成的相对比例。结果表明:不同极化时间制得的单晶硅表面均形成了海绵状均匀分布的纳米孔洞结构。在多孔硅的形成过程中,单晶硅结构发生了显著的晶态转变和晶粒尺寸变化,导致大单晶、纳米晶和无定形态并存,晶粒直径从初期的1.41 nm减小到并保持在0.65 nm,而晶态的转变和晶粒尺寸的变化被认为与晶格畸变程度有关。     

氧化铁纳米薄膜自组装制备与原子力显微镜表征

单晶硅表面上自组装单层有机分子巯基硅烷单层膜,将这层巯基原位氧化成为磺酸基,在氢氧化铁溶胶形成过程中同时放入带有磺酸基层的硅基底进行薄膜组装,由于溶胶颗粒极小、分布均匀,可以得到表面粗糙度仅为0.164nm、颗粒小于10nm的均匀的氧化铁薄膜,并采用原子力显微镜(AFM)进行了表面形貌的表征.     

化学腐蚀法制备纳米多孔硅及其表面形貌表征

采用化学腐蚀法制备了纳米多孔硅粉.利用扫描电子显微镜对多孔硅粉的表面形貌进行了表征.结果表明,在HNO3浓度、反应时间和HNO3滴加时间3种因素中,HNO3浓度对硅粉的腐蚀效果影响最大;浓度过高或者较低时,均不能获得良好的硅粉形貌.HNO3质量分数以20％～25％为宜.反应时间对硅粉结构和形貌的影响比硝酸的滴加速率大.在较低HNO3浓度条件下,延长反应时间对硅粉进行腐蚀更为有效.     

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。     

硅酸钠在太阳能电池单晶硅表面织构化的作用

在单晶硅太阳电池的制备过程中,通常利用晶体硅[100]和[111]不同晶向在碱溶液中各向异性腐蚀特性,在表面形成类似于“金字塔”的绒面结构,使得入射光在硅片表面多次反射,提高入射光吸收效率,可提高单晶硅太阳电池的转换效率。实验探索了一种廉价的硅织构化腐蚀技术,即单独采用Na2SiO3代替传统的氢氧化钠和异丙醇溶液,以减少价格较高的异丙醇的用量,降低成本。不采用异丙醇或其他机械消泡的条件下,用质量分数为5％的Na2SiO3溶液在80℃腐蚀120min,单晶硅片表面可获得最佳反射率为12．56％的减反射绒面。虽然与传统的氢氧化钠和异丙醇溶液效果相比,单独使用Na2SiO3溶液腐蚀单晶硅片表面的反射率和均匀性略差,但在传统的氢氧化钠和异丙醇体系中加入质量分数为0．1％的Na2SiO3也会促进腐蚀反应的进行,获得更加均匀的减反射绒面。     

单晶硅表面微结构调节技术的改进

提出改变碱液腐蚀单晶硅表面特性的一个简单方法,即在碱液中加入活性剂改变碱液在硅表面的润湿性能从而改变其腐蚀特性。分别采用普通碱液、四甲基氢氧化铵（tetramethylammonium hydroxide,TMAH）溶液和加入阴离子有机氟表面活性剂的普通碱液腐蚀硅表面。结果发现：普通碱液和TMAH腐蚀液腐蚀的硅表面的金字塔大小差异大、有许多蜂窝状的小金字塔,反射率较高;用加入阴离子有机氟表面活性剂的普通碱液腐蚀的单晶硅表面,能形成比较规则的金字塔,金字塔尺寸为4～6μm、均匀性好、覆盖率高、表面反射率下降到12．65％。有机氟表面活性剂能提高硅在碱中腐蚀速率,有效调控单晶硅金字塔形貌、大小与分布,为精确调控单晶硅表面微结构提供了可能。     

氨基聚硅氧烷乳液的膜形貌及在棉织物上的应用性能

采用脂肪醇聚氧乙烯醚复配物为乳化剂,制备了氨基聚硅氧烷乳液(ASE),利用原子力显微镜和接触角测量仪等研究了ASE在单晶硅基质表面的膜形貌、亲疏水性能及应用性能.结果表明,制备的ASE外观透明,pH=6.55,固含量24.8%,粒径0.025 μm;ASE可在单晶硅基质表面成膜,该膜较粗糙,均方根粗糙度0.124 nm;水在ASK/单晶硅表面的接触角为97.5°;ASK/CSE(羧基聚硅氧烷乳液)整理织物较之空白织物柔软性能大大提升,当ASE和CSE等质量复配后整理织物,综合应用效果好.     

低应力多孔硅的制备及其含能材料爆炸性能研究

通过调控电化学阳极氧化条件获得表面平整、不龟裂的多孔硅,为制备性能良好的多孔硅/硝酸钆复合含能材料提供了稳定基底。本文首次报导了以质量分数40%氢氟酸和二甲亚砜的混合电解液制得的多孔硅为基底的复合含能材料的制备,并对其性能及寿命进行了探索研究。失重法、SEM、AFM、爆炸光谱、DSC-TG及高速摄像机分析结果表明:二甲亚砜电解液体系与传统的无水乙醇电解液体系相比,其稳定性更好,制备出来的多孔硅表面均匀、不龟裂,且具有更高的孔隙率和膜厚;当制备条件为电解液配比V(氢氟酸)∶V(二甲亚砜)=4∶1,氧化电流密度50 m A/cm~2,氧化时间35 min时,相对应的多孔硅孔隙率为38. 3%,平均膜厚为131. 3μm,表面粗糙度为81. 6 nm,最适宜与硝酸钆形成复合材料。此条件下制得的多孔硅/硝酸钆复合含能材料的爆炸色温为2632. 4 K,释放的能量为2012 J/g。在真空环境下存放360天后,多孔硅/硝酸钆复合含能材料仍然能够发生爆炸,且爆炸较剧烈。     

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.     

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.