Toward an understanding of the turbidity measurement of fleterocoagulation rate constants of dispersions containing particles of different sizes

Our previous studies have shown that the determination of coagulation rate constants by turbidity measurement becomes impossible for a certain operating wavelength (that is, its blind point) because at this wavelength the change in the turbidity of a dispersion completely loses its response to the coagulation process. Therefore, performing the turbidity measurement in the wavelength range near the blind point should be avoided. In this article, we demonstrate that the turbidity measurement of the rate constant for coagulation of a binary dispersion containing particles of two different sizes (heterocoagulation) presents special difficulties because the blind point shifts with not only particle size but also with the component fraction. Some important aspects of the turbidity measurement for the heterocoagulation rate constant are discussed and experimentally tested. It is emphasized that the T-matrix method can be used to correctly evaluate extinction cross sections of doublets formed during the heterocoagulation process, which is the key data determining the rate constant from the turbidity measurement, and choosing the appropriate operating wavelength and component fraction are important to achieving a more accurate rate constant. Finally, a simple scheme in experimentally determining the sensitivity of the turbidity changes with coagulation over a wavelength range is proposed.

Directly synthesized strong, highly conducting, transparent single-walled carbon nanotube films

We report the direct synthesis of strong, highly conducting, and transparent single-walled carbon nanotube (SWNT) films. Systematically, tests reveal that the directly synthesized films have superior electrical and mechanical properties compared with the films made from a solution-based filtration process: the electrical conductivity is over 2000 S/cm and the strength can reach 360 MPa. These values are both enhanced by more than 1 order. We attribute these intriguing properties to the good and long interbundle connections. Moreover, by the help of an extrapolated Weibull theory, we verify the feasibility of reducing the interbundle slip by utilizing the long-range intertube friction and estimate the ultimate strength of macroscale SWNTs without binding agent.

Mn注入n型Ge单晶的特性研究

采用离子能量为100keV,剂量为3×1016cm-2的离子注入技术,室温下往n型Ge(111)单晶衬底注入Mn+离子,注入后的样品进行400℃热处理。利用X-射线衍射法(XRD)和原子力显微镜(AFM)对注入后的样品进行了结构和形貌分析,俄歇电子能谱法(AES)进行了组分分析,交变梯度样品磁强计(AGM)进行了室温磁性测量。结果表明原位注入样品的结构是非晶的,热处理后发生晶化现象。没有在样品中观察到新相形成。Mn离子较深的注入进Ge衬底,在120nm处Mn原子百分比浓度达到最高为8%。热处理后的样品表现出了室温铁磁特性。

The response of porous Al2O3 probed to nanoindentation

The response of porous Al2O3 to nanoindentation was investigated at microscopic scales (nm-mu m) and under ultra-low loads from 5 to 90 mN with special attention paid to the dependence of the load-depth behaviour to sample porosity. It was found that the load-depth curves manifest local responses typical of the various porous structures investigated. This is particularly clear for the residual deformation after load removal. Similarly, the limited mean pressure of the sample containing small grains and interconnected pores is consistent with its porous structure. By comparison, the samples with larger grain size and various porous structures exhibit higher pressures and smaller residual deformations that can be attributed to the mechanical response of the solid phase. (C) 2007 Elsevier B.V. All rights reserved.

Energy transfer between silicon-oxygen-related defects and Yb3+ in transparent glass ceramics containing Ba2TiSi2O 8 nanocrystals

We report on the conversion of near-ultraviolet radiation of 250-350 nm into near-infrared emission of 970-1100 nm in Yb3+-doped transparent glass ceramics containing Ba2TiSi2O8 nanocrystals due to the energy transfer from the silicon-oxygen-related defects to Yb3+ ions. Efficient Yb3+ emission (F-2(5/2)-> F-2(7/2)) was detected under the excitation of defects absorption at 314 nm. The occurrence of energy transfer is proven by both steady state and time-resolved emission spectra, respectively, at 15 K. The Yb2O3 concentration dependent energy transfer efficiency has also been evaluated, and the maximum value is 65% for 8 mol % Yb2O3 doped glass ceramic. These materials are promising for the enhancement of photovoltaic conversion efficiency of silicon solar cells via spectra modification.

Optical properties of transparent alkali gallium silicate glass-ceramics containing Ni2+-doped beta-Ga2O3 nanocrystals

Broadband near-infrared (IR) luminescence in transparent alkali gallium silicate glass-ceramics containing N2+-doped beta-Ga2O3 nanocrystals was observed. This broadband emission could be attributed to the T-3(2g) (F-3) -> (3)A(2g) (F-3) transition of octahedral Ni2+ ions in glass-ceramics. The full width at half-maximum (FWHM) of the near-IR luminescence and fluorescent lifetime of the glass-ceramic doped with 0.10 mol% NiO were 260 nm and similar to 1220 mu s, respectively. It is expected that transparent Ni2+-doped beta-Ga2O3 glass-ceramics with this broad near-IR emission and long fluorescent lifetime have potential applications as super-broadband optical amplification media.

Broadband infrared luminescence from transparent glass-ceramics containing Ni2+-doped beta-Ga2O3 nanocrystals

Transparent Ni2+-doped beta-Ga2O3 glass-ceramics were synthesized. The nanocrystal phase in the glass-ceramics was identified to be beta-Ga2O3 and its size was about 3.6 nm. It was confirmed from the absorption spectra that the ligand environment of Ni2+ ions changed from the trigonal bi-pyramid fivefold sites in the as-cast glass to the octahedral sites in the glass-ceramics. The broadband infrared emission centering at 1270 nm with full width at half maximum (FWHM) of more than 250 nm was observed. The fluorescence lifetime was about 1.1 mu s at room temperature. The observed infrared emission could be attributed to the T-3 (2g) (F-3) -> (3)A (2g) (F-3) transition of octahedral Ni2+ ions. It is suggested that the Ni2+-doped transparent beta-Ga2O3 glass-ceramics with broad bandwidth and long lifetime have a potential as a broadband amplification medium.

Ce：Mn：LiNbO3晶体紫外记录研究

采用紫外光作记录光在Ce：Mn：LiNbO3晶体中实现非挥发全息记录，灵敏度可达0．0803cm／J，衍射效率（固定）为5．07％，比采用红光为记录光，紫外光为敏化光的非挥发双中心记录方案均提高了50多倍。分析表明，采用紫外光作为记录光，深能级电子被激发比例极大提高，参与光折变过程的电子平均运动周期变短．提高了衍射效率和灵敏度；深浅能级电子光栅的同相位，使得固定空间电荷场变强。文中还研究了退火对记录性能的影响。

新型光折变晶体Mn：YAP研究进展

Mn：YAP晶体是近年来发现的一种新型光折变晶体，在三维全息存储方向有广阔的应用前景。总结了Mn：YAP的晶体结构、光谱特征及其光折变模型，分析了它的优点和不足，并对其研究方向提出了设想。

Prescription for optimizing holograms in LiNbO3 : Fe : Mn

The photorefractive holographic dynamics of grating formation in photochromic doubly doped LiNbO3:Fe:Mn crystal is studied numerically and analytically in terms of the two-center model of Kukhtarev Et al. [Ferroelectrics 22, 949 (1979)]. The relations among the recorded and fixed space-charge fields and the doping densities, the oxidation-reduction states of the fields, and the intensities of UV-sensitizing and red recording beams are studied. Important conditions and effects are feued, and an optimal prescription for material doping and oxidation-reduction processing is suggested in which the crystal can be strongly oxidized and the Mn-doping density is smaller than the Fe-doping density. (C) 2000 Optical Society of America. OCIS codes: 050.7330, 190.5330, 090.2900.

双掺杂LiNbO3：Fe：Mn晶体局域光折变体全息光栅形成及衍射特性

将带输运模型与二维耦合波理论相结合，研究了双掺杂LiNbO3：Fe：Mn晶体中由两束有限宽度平面波干涉产生的局域光折变体全息的动力学机制及其衍射特性。采用三步法联立求解了双中心带输运物质波方程和二维耦合波方程。数值计算结果表明，局域光折变体全息光栅的空间电荷场在空间上呈不均匀分布。当光栅区域较小时空间电荷场较强，随着光栅区域的增大，空间电荷场急剧下降，并降低一个数量级。此外，在接近光束入射边界的区域，空间电荷场时空变化规律与一维无限大光折变体全息光栅的结果相似，随着光栅区域的扩大，边界效应对空间电荷场的影

Spectroscopic and thermal properties of short wavelength metal (II) complexes containing alpha-isoxazolylazo-beta-diketones as co-ligands

Two new azo dyes of alpha-isoxazolylazo-beta-dilcetones and their Ni(II) and Cu(II) complexes with blue-violet light wavelength were synthesized using a coupling component, different diazo components and metal (II) ions (Ni2+ and Cu2+). Based on the elemental analysis, MS spectra and FT-IR spectral analyses, azo dyes were unequivocally shown to exist as hydrazoketo and azoenol forms which were respectively obtained from the solution forms and from the solid forms. The action of sodium methoxide (NaOMe) on azo dyes in solutions converts hydrazoketo form into azoenol form, so azo dyes are coordinated with metal (II) ions as co-ligands in the azoenol forms. The solubility of all the compounds in common organic solvents such as 2,2,3,3-tetrafluoro-1-propanol (TFP) or chloroform (CHCl3) and absorption properties of spin-coating thin films were measured. The difference of absorption maxima from the complexes to their ligands was discussed. In addition, the TG analysis of the complexes was also determined, and their thermal stability was evaluated. It is found that these new metal (II) complexes had potential application for high-density digital versatile disc-recordable (HD-DVD-R) system due to their good solubility in organic solvents, reasonable and controllable absorption spectra in blue-violet light region and high thermal stability. (c) 2004 Elsevier B.V. All rights reserved.

A new strategy of enhancing two-photon absorption in benzothiazole-containing fluorene molecules: Introduction of auxiliary donor-acceptor effects

A series of benzothiazole-containing fluorene molecules have been designed and their one- and two-photon absorption properties have been investigated theoretically by using the ZINDO method. The effects of electron-excessive/deficient heterocyclic bridges as auxiliary donors (auxD)/acceptors (auxA) on TPA cross-sections were studied. The results show that the molecules with D-pi-auxA-A, D-aux D-pi-A, or D-auxD-pi-auxA-A structure types have large TPA cross-section, which can be a valuable strategy in the design of two-photon absorption materials. Also, a linear relationship between the first hyperpolarizability and the TPA cross-section is observed. (c) 2006 Elsevier B.V. All rights reserved.

Spectroscopic, and thermal studies of some new binuclear transition metal(II) complexes with hydrazone ligands containing acetoacetanilide and isoxazole

A new chelating ligand, 2-(2-(5-tert-butylisoxazol-3-yl)hydrazono)-N-(2,4-dimethylphenyl)-3-oxobutanamide (HL), and its four binuclear transition metal complexes, M-2(L)(2) (mu-OCH3)(2) [M = Ni(II), Co(II), Cu(II), Zn(II)], were synthesized using the procedure of diazotization, coupling and metallization. Their structures were postulated based on elemental analysis, H-1 NMR, MALDI-MS, FT-IR spectra and UV-vis electronic absorption spectra. Smooth films of these complexes on K9 glass substrates were prepared using the spin-coating method and their absorption properties were evaluated. The thermal properties of the metal(II) complexes were investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC. Different thermodynamic and kinetic parameters namely activation energy (E

Nickel(II) and copper(II) complexes containing 2-(2-(5-substitued isoxazol-3-yl)hydrazono)-5,5-dimethylcyclohexane-1,3-dione ligands: Synthesis, spectral and thermal characterizations

Two new hydrazone chelating ligands, 2-(2-(5-methylisoxazol-3-yl)hydrazono)-5,5-dimethylcyclohexane-1,3-dione (HL1) and 2-(2-(5-tert-butylisoxazol-3-yl)hydrazono)-5,5-dimethylcyclohexane- 1,3-dione (HL2), and their nickel(II) and copper(II) complexes were synthesized using the procedure of diazotization, coupling and metallization. Their structures were postulated based on elemental analysis, H-1 NMR, ESI-MS, FT-IR spectra and UV-vis electronic absorption spectra. Smooth films of these complexes on K9 glass substrates were prepared using spin-coating and their absorption properties were evaluated. The thermal properties of the metal(II) complexes were investigated by thermogravimetry (TG) and differential thermogravimetry (DTG). Different thermodynamic and kinetic parameters namely activation energy (E