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121.
122.
A method for the determination of the dynamic surface tension of surfactant solutions is presented which allows to cover adsorption times down to 10 seconds. This method is based on the determination of the pressure inside two communicating bubbles. There is no deformation of the solution/air interface during the experimental procedure. Hence, in evaluating the kinetic data no surface area enlargement has to be taken into account. An automatically operating procedure should allow to cover adsorption times down to approximately one second and should improve the measuring accuracy substantially. Experimental investigations with aqueous n-decanoic acid solutions using the method proposed provided evidence that decanoic acid is adsorbed by a diffusioncontrolled mechanism. 相似文献
123.
New copper(II) complexes of the hydrazone ligands H2salhyhb, H2salhyhp, and H2salhyhh, derived from salicylaldehyde and ω‐hydroxy carbonic acid hydrazides, have been synthesized and physically characterized. Two fundamental structures were found in solid state depending on the pH‐value of the reaction solution. Acidic conditions lead to the formation of the di‐μ‐phenoxo‐bridged dicationic complex dimers [{Cu(Hsalhyhb)}2]2+ ( 1a ), [{Cu(Hsalhyhp)}2]2+ ( 2a ), and [{Cu(Hsalhyhh)}2]2+ ( 3a ), isolated as perchlorate salts. The dimeric complexes show strong antiferromagnetic coupling with J = ?399 ( 1a ), ?410 ( 2a ), and ?311 cm?1 ( 3a ). Higher pH‐values resulted in the aggregation of neutral copper ligand fragments to the one‐dimensional coordination polymers [{Cu(salhyhb)}n] ( 1b ), [{Cu(salhyhp)}n] ( 2b ), and [{Cu(salhyhh)}n] ( 3b ). 3b has been examined by means of X‐ray crystallography and represents the first example of a structurally characterized neutral copper(II) N‐salicylidenehydrazide complex without additional ligands. The magnetic interactions in the polymers are also antiferromagnetic with J = ?125 ( 1b ), ?136 ( 2b ), and ?148 cm?1 ( 3b ), but strongly reduced compared to the corresponding dimeric complexes. The two basic structure types can be reversibly interconverted simply by pH‐control. 相似文献
124.
失效原子力显微镜硅针尖再生 总被引:2,自引:0,他引:2
原子力显微镜的传统商品硅针尖在使用过程中极易因磨损而失效,本文研究了一种在实验室条件下简易可行的回收利用失效硅针尖的方法。在原子力显微镜的敲击模式下使用曲率半径大于100 nm的失效硅针尖对生长单壁碳纳米管的样品表面进行扫描,把样品表面的单壁碳纳米管管束粘接到硅针尖上,可制得直径在5~20 nm的碳纳米管针尖。实验对碳纳米管针尖和新的商品硅针尖进行了成像对比,所制备的碳纳米管针尖不仅在成像分辨率而且在成像稳定性上都优于新的商品硅针尖。 相似文献
125.
Nitrogen ion implantation (24 keV, 4.6 × 1017 cm?2) into (100) a p‐type silicon wafer material and a subsequent electron beam annealing at 1100 °C for 15 s under high vacuum conditions leads to the formation of an uneven surface in the implanted region caused by nitrogen bubbles beneath the surface. Annealing at 1200 °C for 300 s results in surface cavities with a mean diameter of 350 nm and a surface coverage of 3–4% and an average depth of ~60 nm. Nuclear reaction analysis reveals that the nitrogen concentration in the as‐implanted state exceeds 57 at%, the value of stoichiometric Si3N4. Annealing at 1100 °C for 15 s slightly reduces the nitrogen peak concentration, whereas annealing at 1200 °C for 300 s induces a significant alteration to the shape of the nitrogen depth profile coupled with the lowering of the concentration close to the stoichiometry of Si3N4. The results present a new method of producing sub‐micrometre cavities embedded in a thin silicon nitride film on wafer silicon which may lead to novel micro‐electronic and biotechnology applications. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
126.
127.
AIBN/SmCl3/乳酸体系催化甲基丙烯酸甲酯的反向原子转移自由基聚合 总被引:5,自引:0,他引:5
利用稀土金属化合物三氯化钐(SmCl3)和二氯化钐(SmCl2)之间的单电子转移反应,以AIBN/SmCl3/乳酸作为反向原子转移自由基聚合(ReverseATRP)的催化体系,成功地实现了甲基丙烯酸甲酯(MMA)的反向ATRP,并考察了温度、溶剂和组分比对聚合反应的影响.MMA在该体系中的聚合反应是一级反应,所得PMMA的分子量与单体转化率成正比,聚合物的分子量分布较窄(Mw/Mn<1.5),具有活性聚合的特征. 相似文献
128.
Xiao‐Ping Chen Anne Buyle Padias H. K. Hall 《Journal of polymer science. Part A, Polymer chemistry》2002,40(12):1929-1936
A non‐olefinic monomer, methyl 1‐bicyclobutanecarboxylate (MBC), was successfully polymerized by the controlled/“living” atom transfer radical polymerization (ATRP) technique, resulting in a well‐defined homopolymer, PMBC, with only cyclobutane ring units in the polymer chain. An AB block copolymer poly(methyl 1‐bicyclobutanecarboxylate)‐b‐polystyrene (PMBC‐b‐PS), having an all‐ring unit segment, was also synthesized with narrow polydispersity and designed number‐average molecular weight in addition to precise end groups. The 1H NMR spectra, glass‐transition temperature, and thermal stability of PMBC, PMBC‐b‐PS, and PS‐b‐PMBC were investigated. The experimental results showed that the cyclobutane rings in the two block polymers improved their thermal stability. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1929–1936, 2002 相似文献
129.
Nitrido-Silicates. II. High Temperature Syntheses and Crystal Structures of Sr2Si5N8 and Ba2Si5N8 Pure Sr2Si5N8 and Ba2Si5N8 were obtained by reaction of silicon diimide with metallic strontium and barium, respectively. The reactions have been carried out under nitrogen atmosphere in a specially developed high-frequency furnace at temperatures between 1 550 and 1 650°C. Sr2Si5N8 (Pmn21, a = 571.0(2), b = 682.2(2), c = 934.1(2) pm, Z = 2, R = 0.037, wR = 0.021) and Ba2Si5N8 (Pmn21, a = 578.3(2), b = 695.9(2), c = 939.1(2) pm, Z = 2, R = 0.022, wR = 0.018) are isotypic and contain M2+ ions as well as a three-dimensional covalent network structure of corner-sharing SiN4 tetrahedra. Two sorts of N occur with molar ratio 1 : 1 which are bonded to two and three Si, respectively. Predominantly, the N which are bonded to two Si belong to the coordination spheres of the M2+ ions. 相似文献
130.
Z. M. Khakimov F. T. Umarova N. T. Sulaymonov A. E. Kiv A. A. Levin 《International journal of quantum chemistry》2003,93(5):351-359
New model of Si? H bond dissociation is proposed and tested in the cluster Si10H16 by the simulation approach that combines classic molecular dynamics method and the self‐consistent tight‐binding electronic and total energy calculation one. It is shown that the monohydride Si? H bond is unstable with respect to silicon dangling bond and bend‐bridge Si? H? Si bond formation when this cluster traps the single positive charge and that hydrogen migrates through a path involving rather rotation around the Si? Si bond than the center of this bond (the bond‐centered position). These results can be useful for understanding hydrogen‐related phenomena at surfaces, interfaces, and internal voids of various hydrogenated silicon systems: electronic devices, silicon solar cells, and nanocrystalline and porous silicon. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 351–359, 2003 相似文献