Thermodynamics of interaction between sodium bis(2‐ethylhexyl) sulfosuccinae and polymers in aqueous solutions by isothermal titration microcalorimetry

The interactions between sodium bis(2‐ethylhexyl) sulfosuccinae (AOT) and two nonionic water‐soluble polymers, including polyvinyl pyrrolidone (PVP) and polyethylene glycol (PEG) have been investigated by using isothermal titration microcalorimetry in aqueous solutions at 298.15 K. The results show that the critical aggregation concentration, which corresponding to the first turning point in the curve of experimental interaction heat versus concentration of the surfactant, is lower than the critical micellar concentration (cmc), confirming the existence of polymer‐surfactant interactions. The value of cac is not sensitive to the relative amount of polymer in low concentration range of the polymer. The mono‐layer saturated adsorption concentration, which corresponding to the second turning point, rises as the polymer concentration is increased. The interaction between PVP and AOT is stronger than that between PEG and AOT. The results also indicate that the aggregation of AOT in water and polymers solutions is entropically driven. The observed thermal effects have been interpreted in terms of the interactions of the polymer molecules with AOT monomers or the molecular clusters. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 275–283, 2006     

LIA注入器发射度增长机理研究及其抑制措施

根据直线感应加速器(LIA)的特点采用了轴对称直流模型,结合E.P.Lee的理论导出了发射度增长的微分方程,提出了一种直线感应加速器发射度增长的机理,根据该机理计算了从均匀分布到高斯分布的演变过程中发射度增长的大小,指出直线感应加速器(LIA)注入器阶段束流发射度增长主要是由于非线性效应导致的束刨面电流密度分布变化引起的.根据研究结果,提出了相应的抑制发射度增长的措施.     

Syntheses, crystal structure and luminescence property of novel 4f-3d heterometallic one-dimensional coordination polymers

Two 4f-3d heterometallic one-dimensional coordination polymers [ZnEu₂(Fur)₈·2H₂O]n and [ZnTb₂(Fur)₈·2H₂O]n (HFur=α-furancarboxylic acid) with good solubility were synthesized and characterized by infrared spectra, X-ray single crystal and powder diffractions, thermogravimetric and differential thermal analysis, and excitation and emission spectra. The X-ray diffraction analyses revealed that the two complexes are isomorphous. The Zn and Ln atoms are linked into one-dimensional chains by furancarboxylate ligands and the metal atoms are arranged in the ···Zn···Ln···Ln···Zn···Ln···Ln···order. Under the excitation of UV light, these coordination polymers emit intense characteristic luminescence of Eu³⁺ or Tb³⁺ ion, respectively. The influence of Zn²⁺ ion on the luminescence properties was also discussed here.     

Amphiphilic maleic acid-containing alternating copolymers—2. Dilute solution characterization by light scattering,intrinsic viscosity,and PGSE NMR spectroscopy

The dilute solution behavior of several alternating copolymers of maleic acid has been characterized by static and dynamic light scattering, intrinsic viscosity, and pulsed-gradient spin-echo NMR spectroscopy. The copolymer of maleic acid–sodium salt and isobutylene (IBMA-Na, M_w ∼350 kg/mol) dissolves readily in concentrated aqueous salt solutions. Changes in chain dimensions with ionic strength and pH are similar to those of the lesser salt solution-soluble poly(acrylic acid-sodium salt). The hydrophobically modified (with n-butyl, n-hexyl, n-octyl, and phenethyl amines) copolymers of maleic acid–sodium salts and isobutylene (IBMA-NHR-Na) show no sign of large intermolecular aggregation in 0.1 N sodium acetate (NaAc). However, the sizes of the copolymers are relatively small compared to that of the ionized parent copolymer (IBMA-Na, M_w ∼350 kg/mol), suggesting intramolecular aggregation of the alkyl side-chain groups along the polymer backbone. The copolymer modified with the longer chain n-decyl, on the other hand, forms stable large intermolecular aggregates containing 33 chains/aggregate. The copolymers of maleic acid–sodium salt and styrene (SMA-Na) appear to have no signs of aggregation, despite being a hydrophobic polyelectrolyte. The copolymer of maleic acid–sodium salt and di-isobutylene (DIBMA-Na) has a similar salting-out concentration as SMA-Na. The radius of gyration measurements by static light scattering suggest that at least some fraction of the DIBMA-Na chains form large intermolecular aggregates. The copolymers of maleic acid–sodium salt with n-alkenes (n-C_mMA-Na) in 0.1 N NaAc form small intermolecular aggregates (three to five chains/aggregate). In contrast to these static light scattering results, PGSE NMR diffusion measurements for the above aggregated systems indicate only one diffusion coefficient consistent with the motion of single isolated chains. A plausible explanation for this discrepancy is that the population of the aggregates is too small to be sufficiently detected in the PGSE NMR experiment. Furthermore, it is likely that the aggregate has a larger relaxation rate than the nonaggregate, and therefore has a comparatively reduced signal in the PGSE NMR experiment. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3584–3597, 2004     

TiN/TiB2异结构纳米多层膜的共格生长与力学性能

采用多靶磁控溅射法制备了一系列具有不同TiB₂调制层厚度的TiN/TiB_{2纳米多层膜.利用x射线衍射仪、高分辨电子显微镜和微力学探针研究了TiB2层厚变化对多层膜生长结构和力学性能的影响.结果表明，在fcc-TiN层(111)生长面的模板 作用下，原为非晶态的TiB2层在厚度小于2.9nm时形成hcp晶体态，并与fcc-TiN 形成共格外延生长；其界面共格关系为{111}TiN//{0001}TiB2，〈110〉TiN//〈1120〉TiB2.由于共格界面存在晶格失配 度，多层膜中形成拉、压交变的应力场，导致多层膜产生硬度和弹性模量升高的超硬效应， 最高硬度和弹性模量分别达到46.9GPa和465GPa.继续增加TiB2层的厚度，TiB2形成非晶态并破坏了与TiN层的共格外延生长，多层膜形成非晶TiN层和非晶TiB< sub>2层交替的调制结构，其硬度和弹性模量相应降低. 关键词： 2}纳米多层膜')" href="#">TiN/TiB₂纳米多层膜 共格生长 晶体化 力学性能     

Short period (Si6Ge4)p superlattices: photoluminescence and electron microscopy study

Si–Ge heterostructures made of 6 monolayers of Si and 4 monolayers of Ge repeated p times (Si₆Ge₄)_p, strained on Si (1 0 0) substrates, have been investigated by photoluminescence measurements and electron microscopy. The films were grown at 400°C by molecular beam epitaxy, using Sb as surfactant. The photoluminescence results of the whole set of samples show similar spectra, for both the single Ge quantum well (p=1) and the thicker heterostructure (p=30). The phonon assisted transverse optical line is measured at about 40 meV far from the no-phonon one, and this corresponds to the Ge–Ge vibration. Our results demonstrate that excitonic recombination occurs mainly in the Ge layers and it is indirect in nature, whatever the repetition number (p) is. Furthermore, we evidenced a high localization of the photoluminescence process excluding any superperiodicity effect.     

Discrete symmetry groups of vertex models in statistical mechanics

We analyze discrete symmetry groups of vertex models in lattice statistical mechanics represented as groups of birational transformations. They can be seen as generated by involutions corresponding respectively to two kinds of transformations onq×q matrices: the inversion of theq×q matrix and an (involutive) permutation of the entries of the matrix. We show that the analysis of the factorizations of the iterations of these transformations is a precious tool in the study of lattice models in statistical mechanics. This approach enables one to analyze two-dimensionalq ⁴-state vertex models as simply as three-dimensional vertex models, or higher-dimensional vertex models. Various examples of birational symmetries of vertex models are analyzed. A particular emphasis is devoted to a three-dimensional vertex model, the 64-state cubic vertex model, which exhibits a polynomial growth of the complexity of the calculations. A subcase of this general model is seen to yield integrable recursion relations. We also concentrate on a specific two-dimensional vertex model to see how the generic exponential growth of the calculations reduces to a polynomial growth when the model becomes Yang-Baxter integrable. It is also underlined that a polynomial growth of the complexity of these iterations can occur even for transformations yielding algebraic surfaces, or higher-dimensional algebraic varieties.     

生长温度对In0.53Ga0.47As/InP的LPMOCVD生长影响

利用LPMOCVD技术在InP衬底生长了InxGa1-xAs材料，获得表面平整．光亮的In0.53Ga0.47As外延层。研究了生长温度对InxGa1-xAs外延层组分、表面形貌、结晶质量、电学性质的影响。随着生长温度的升高，为了保证铟在固相中组分不变，必须增加三甲基铟在气相中的比例。在生长温度较高时，外延层表面粗糙。生长温度在630℃与650℃之间，X射线双晶衍射曲线半高宽最窄，高于或低于这个温度区间，半高宽变宽。迁移率随着生长温度的升高而增加,在630℃为最大值，然后随着生长湿度的升高反而降低。生长温度降低使载流子浓度增大，在生长温度大于630℃时载流子浓度变化较小。     

Structural characterization of nanocrystalline CrOOH·2H2O aerogel by X-ray diffraction

The nanostructured powder prepared by critical CO₂ extraction of the urea-assisted wet chromia gel mixture at 373 K in vacuum was studied by X-ray diffraction techniques. Thermoanalytical methods showed the presence of the lattice water molecules in the resulting phase corresponding to a chemical formula CrOOH·2H₂O. The CrOOH·2H₂O nanocrystals of 3-5 nm in diameter were observed in transmission electron microscopy and their structure was derived from the Rietveld analysis in which the disorder contribution to the X-ray scattering was implemented. The structural model shows that the hexagonal unit cell of α-CrOOH undergoes monoclinic distortion with half of the O⁻² anions and OH⁻ groups being replaced by bonded water molecules in the three-dimensional packing resulting in half of the sites in regular Cr⁺³ octahedra being vacant. Further examination of the quasi-crystalline disordered state of the CrOOH·2(H₂O) nanocrystals was performed by model independent method of Radial Distribution Function (RDF). This complementary technique is sensitive to the molecular composition and allows to assess the average atomic (or electron) density distribution and the spacings of the atomic arrangements in the nearest neighbor shells comprising the range of the crystalline order in the structure of this material.     

Raman scattering of Zn doped CuGaS2 layers grown by vapor phase epitaxy

Raman spectra for non-site-selectively and site-selectively Zn-doped CuGaS₂ layers grown by vapor phase epitaxy (VPE) were investigated. Although an appearance of characteristic Raman line(s) related with the doped Zn atom was not seen, an enhancement of the Raman intensity ratio of the highest LO mode to the A₁ mode (I_LO/I_A1) was observed. The site-selectively Zn-doped layers with p-type conductivity exhibited larger I_LO/I_A1 ratio compared to those with n-type conductivity. The observed correlation between the I_LO/I_A1 ratio and the peak energy of the photoluminescence characteristic for Zn-doped p-type samples (L emission) suggests that the enhancement of I_LO/I_A1 is due to the increase of Zn atom substituting Ga site (Zn_Ga) which is acting as an acceptor.