On Mechanism of Oxide Formation in Electrodeposited Co-based Films with Columnar Structure

An investigation of the Co oxides formation and distribution dependent on preparation conditions during electrodeposition of hcp Co-based films with perpendicular magnetic anisotropy has been made. It has been shown that the [100] oriented columnar crystallites promote some regularity in impurity distribution and orientation in the film plane, whereas the [001] oriented ones- non-regular distribution. Such a behaviour is associated with the difference in the impurity incorporation for these two cases: preferably crystalline and intergranular, respectively, and atomic bonds saturation, and influence on the mechanical and magnetic properties of the investigated films.     

On Mechanism of Internal Stresses Formation in Electrodeposited Co-based Alloy Films with Columnar Structure

The internal stresses formed in electrodeposited Co-based alloy films with columnar structure have been investigated. It is shown that the sign and the value of the stresses are determined by the texture, amount of the adsorbed impurities (CoO and Co(OH)₂) and character of their incorporation in the deposit. A preferable crystallite incorporation of the impurities promotes the formation of the tensile stresses through the substraction stacking faults formation. With the crystalline incorporation decreasing, the compression stresses mechanism, caused by the crystallization pressure prevails.     

对柱状多晶硅薄膜的制备研究

在多晶硅薄膜(Poly-Si)生长理论的基础上,用等离子体化学气相沉积(RF-PECVD)系统,配合快速光热退火装置(RTP),在玻璃衬底和石英衬底上制备了柱状结构的多晶硅薄膜.借助于扫描电子显微镜(SEM)等测试手段,对薄膜的表面形貌和断面形貌进行了分析.结果发现:(1)柱晶的形成对薄膜的厚度有一定要求,而且薄膜越厚,柱晶直径越容易长得更大.本实验中,薄膜厚度达到2.5μm左右时,柱晶直径达到了1.5μm以上;(2)再结晶过程是从靠近光源的薄膜表面开始进而到薄膜内部的.再次说明RTP中再结晶的发生,与光和物质的相互作用密切相关.     

Columnar grain growth pattern with fluid flowing in molten pool

A coupled model was used to simulate columnar grain growth in TIG (tungsten inert‐gas) molten pool of nickel base alloy. The cellular automaton algorithm for dendritic growth is incorporated with solute transport model to take fluid flow into consideration. The results indicate that shear flow changes the solute distribution at the S/L (Solid/Liquid) interface, leading to asymmetrical growth of columnar grains. The dendrite arms on the upstream side grow fast, while the growth of dendrite arms on the downstream side is much delayed. However, dendrite arms on both sides are not as well‐developed as the grain growth without flow. With inlet flow velocity increasing, the phenomenon becomes more obvious. In addition, shear flow also results in more severe coring segregation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the Influence of Twinning Processes on Columnar Crystallite Growth in Electrodeposited Films

An investigation of columnar crystallite growth during the electrodeposition of fcc Ni and hcp Co-W films has been made. It has been shown that the twinning processes not only promote the transformation of the initial orientation to the growth texture, but also lead to the change of the orientation of long columnar axes, the twinning processes in the fcc metal films exerting more significant influence on the columnar growth character than in the hcp ones.     

Landau Theory of Transitions from the Drd Phase of Columnar Liquid Crystals

Possible symmetry patterns of disordered columnar phases associated with the continuous symmetry breaking of the D_rd (pgg) phase are given. The results may be used to predict new mesophases which are as yet undiscovered and should be of aid in identifying unconfirmed phases. The universality classes of the possible transitions are also given.     

Sodium diffusion in boroaluminosilicate glasses

Understanding the fundamentals of alkali diffusion in boroaluminosilicate (BAS) glasses is of critical importance for advanced glass applications, e.g., the production of chemically strengthened glass covers for personal electronic devices. Here, we investigate the composition dependence of isothermal sodium diffusion in BAS glasses by ion exchange, inward diffusion, and tracer diffusion experiments. By varying the [SiO₂]/[Al₂O₃] ratio of the glasses, different structural regimes of sodium behavior are accessed. We show that the mobility of the sodium ions decreases with increasing [SiO₂]/[Al₂O₃] ratio, revealing that sodium is more mobile when it acts as a charge compensator to stabilize network formers than when it acts as a creator of non-bridging oxygens on tetrahedrally-coordinated silicon and trigonal boron. The impacts of both the addition of iron and its redox state on the sodium diffusivity are explored in terms of the structural role of ferric and ferrous ions. By comparing the results obtained by the three approaches, we observe that both the tracer Na diffusion and the Na–K interdiffusion are significantly faster than the Na inward diffusion. The origin of this discrepancy could be attributed to the fact that for sodium inward diffusion, the charge compensation for electron holes is a rather slow process that limits the rate of diffusion.     

Columnar Mesomorphism of the Mixed Substituted Apolar Triphenylenes: Prognosis and Experimental Data

Abstract

The calculations of molecular parameters (MP) of triphenylene derivatives with the mixed substituents were carried out here. The prognosis of columnar mesomorphism (CM) for this series of compounds was made on the basis of the value of MP. The compounds Ia-If are synthesized, their thermotropic and lyotropic mesomorphism have been studied. The good agreement of calculation and experimental data has been found for a new series of triphenylenes.     

Co-Existent Biphasic Region of Nematic and Columnar Smectic Phases in Binary Mixture of Berberine and Alizarin Dye

We report the results of our studies on the optical and thermal properties of binary mixture of two compounds viz., berberine and alizarin dye. The mixture shows a very interesting co-existent biphasic region of nematic N + I and smectic C + I phases, sequentially when the specimen is cooled from its isotropic phase respectively at different concentrations of Alizarin dye in berberine molecule. The temperature variations of optical anisotropy, optical textures, and electrical conductivity have also been discussed. Aggregated molecular size has been confirmed by X-ray studies.     

Phase Transition and Optical Characterization of Mesophase Stability of Nematic and Columnar Biphasic Regions

We report the results of our studies on the optical and thermal properties of binary mixture of two compounds viz., abietic acid and alizarin dye. The mixture shows a very interesting co-existent biphasic regions of nematic (N + I) and columnar smectic (C + I) phases, sequentially when the specimen is cooled from its isotropic phase respectively at different concentrations of given molecule. The temperature variations of optical anisotropy, optical textures and electrical conductivity have also been discussed. Aggregated molecular size has been confirmed by X-ray studies.     

Preparation of Stable Anisotropic Films with Columnar Order from Polymerizable Star-shaped Supramolecular Liquid Crystals

We have fabricated new stable anisotropic films with columnar order using star-shaped supramolecular liquid crystals as photoreactive monomers. The polymerizable supramolecular liquid crystal exhibiting a hexagonal columnar mesophase has been prepared simply through hydrogen bonding between a phloroglucinol core and pyridine derivatives containing acrylate groups in the alkyl chain. Photopolymerization of the supramolecular monomer in the liquid crystalline state yielded cross-linked anisotropic polymer networks with columnar order. The controlled approach in the present study opens a new way to design and prepare stable anisotropic materials for potential electronic and optical applications.     

Sodium tracer diffusion in sodium boroaluminosilicate glasses

Sodium tracer diffusion coefficients, D*_Na, have been measured using the radioactive isotope Na-22 in sodium boroaluminosilicate (NBAS) glasses containing either a small amount of As₂O₃ or Fe₂O₃. The chemical compositions of the first type of glasses are given by the formula [(Na₂O)_0.71(Fe₂O₃)_0.05(B₂O₃)_0.24]_0.2[(SiO₂)_x(Al₂O₃)_1 ? x]_0.8 and those of the second type of glasses correspond to the formula [(Na₂O)_0.73(B₂O₃)_0.24(As₂O₃)_0.03]_0.18[(SiO₂)_x(Al₂O₃)_1 ? x]_0.82. Tracer diffusion measurements were performed at different temperatures between 198 and 350 °C. Pre-annealing of the glass samples at their glass transition temperatures in common air was found to lead to changes in the values of sodium tracer diffusion coefficients. For the NBAS glasses containing Fe₂O₃, after pre-annealing for 5 h, the activation enthalpy derived for the sodium tracer diffusion increases almost linearly from 57.5 to 71.3 kJ/mol with a decrease in the alumina content while the pre-exponential factor of the sodium tracer diffusion coefficient increases from 2.1 · 10^? 4 to 5.3 · 10^? 4 cm²/s. For the iron-free NBAS glasses pre-annealed for 5 h, the activation enthalpy varies between 63.9 and 71.4 kJ/mol while the pre-exponential factor varies between 1.5 · 10^? 4 and 1.2 · 10^? 3 cm²/s. In addition, it was observed that the considered glasses take up water when annealed at 300 °C in wet air with P_H2O = 474 mbar.     

Sodium acetate tri-hydrate whiskers

A new kind of whisker, which has not been previously reported in the literature, was grown on membranes which were in contact with a saturated aqueous solution of sodium acetate, using several techniques. Cellulose acetate membranes were used in all the cases and growth was successful at 25 ± 2°C and 45–55% relative humidity. A dense colony of whiskers, sometimes stuck together in bundles, usually up to 5 cm in length and ranging in width from 0.3–100 μm, developed within 72 h of growth. The whiskers were identified as sodium acetate tri-hydrate by means of Debye-Scherrer X-ray powder method. Laue transmission photographs indicated the existence of twin crystals within the individual single crystal whiskers as proved by electron diffraction in TEM. Some whiskers included internal and external channels, and there were several secondary effects, such as thickening in the middle of a whisker, formation of arrow-heads or spirals at the tips and various modes of branching. The whisker morphology and the various growth phenomena may be explained as a whisker growth process from their bases, when we consider a continuous crystallization from material which is supplied through and over the membrane.     

Supramolecular Discotic Columnar Liquid Crystals Built through Single Hydrogen Bonding between Carboxylic Acid and Pyridine Moieties

New self-assembled discotic columnar liquid crystals were prepared via single hydrogen bonding between the core molecule of 1,3,5-cyclohexanetricarboxylic acid and the peripheral units of stilbazole derivatives. The hydrogen-bonded liquid crystals exhibited rectangular columnar and hexagonal columnar mesophases depending on the number of alkyl chains in three arms of the discotic mesogen through dipole-dipole interactions between carbonyl groups along the column axis. The intermolecular hydrogen bonding between carboxylic acid and pyridine moieties provides an effortless methodology to prepare the ordered columnar liquid crystals for electronic applications.     

Sodium ion transport in high purity borosilicate glasses

²²Na diffusion coefficients and dc electrical conductivity were measured in 0.7 B₂O₃·0.3 SiO₂ (mole ratio) glasses containing small amounts of Na₂O (111 ppm to 2.6 mol%). Correlation factors near unity were obtained from the Nernst-Einstein equation for these glasses. These values are in agreement with a previously proposed free “interstitial” alkali ion diffusion mechanism in low alkali content glasses. It is concluded from the low values of the sodium diffusion coefficients and dc conductivity in these glasses (relative to similar silicate and germanate glasses) that the Na⁺ are bound strongly to the borate-rich glass network and that the number of dissociated Na⁺ at any given time is small.     

Structure of Sodium Cholate Micelles

Crystallography Reports - Sodium cholate is a bile acid salt, which is applied as a biological detergent. The mixed systems of phospholipid/sodium cholate are used to study the self-assembly of...     

Crystallization Kinetics of Sodium Perborate

Some basic physicochemical properties of aqueous sodium perborate solutions, essential in designing an effective control, were measured. The kinetics of primary nucleation was determined by the measurement of the metastable zone width. The differential method was applied for the determination of the crystal growth rate equation. It was found that the solubility and the nucleation rate constants are in very good agreement with the literature data whereas the parameters of the growth rate equation show an influence of the experimental conditions.     

Synthesis and Mesomorphic Properties of New Columnar Liquid Crystal Containing 1,3,5-triiminebenzene with Pendant 1,3,4-thiadiazole Group

A novel discotic liquid crystal series based on 1,3,5-benzenetrisazomethine derivatives with three pendant 2-amino-5-(4′-n-alkoxy)phenyl-1,3,4-thiadiazole has been synthesized, which is the first columnar molecules containing 1,3,4-thiadiazole moiety exhibiting a discotic liquid crystal. The molecular structure of compounds was confirmed by FT-IR, ¹H-NMR, and mass spectroscopy and elemental analysis. The electron excitation properties of these compounds were investigated by UV-vis absorption spectroscopy. Their liquid crystalline properties were studied by polarizing optical microscopy and differential scanning calorimetry. The formation of a columnar mesophase was found to be dependent on the number of methylene unit in alkoxy side chains.