High pressure studies using two-stage diamond micro-anvils grown by chemical vapor deposition

Ultra-high static pressures have been achieved in the laboratory using a two-stage micro-ball nanodiamond anvils as well as a two-stage micro-paired diamond anvils machined using a focused ion-beam system. The two-stage diamond anvils’ designs implemented thus far suffer from a limitation of one diamond anvil sliding past another anvil at extreme conditions. We describe a new method of fabricating two-stage diamond micro-anvils using a tungsten mask on a standard diamond anvil followed by microwave plasma chemical vapor deposition (CVD) homoepitaxial diamond growth. A prototype two-stage diamond anvil with 300?µm culet and with a CVD diamond second stage of 50?µm in diameter was fabricated. We have carried out preliminary high pressure X-ray diffraction studies on a sample of rare-earth metal lutetium sample with a copper pressure standard to 86?GPa. The micro-anvil grown by CVD remained intact during indentation of gasket as well as on decompression from the highest pressure of 86?GPa.     

Disintegration of flows of superheated liquid films and jets

This paper represents results on investigating the dynamics of boiling and disintegration of superheated liquid films and jets. The first part deals with experimental study of boiling liquid outflow through short cylindrical and slit channels. Evolution of disintegration of a hot water jet flow is observed both at low and moderate superheating and at high and limit superheating, and also for vaporization mechanisms corresponding to these superheatings. Peculiarities of disintegration of jets through slit and cylindrical channels are noticed. Results on measuring the reactive thrust of the jet through a slit channel under different geometrical conditions behind the channel outlet are represented. The 1/f fluctuations in transient regimes of superheated liquid boiling and in transient regimes of behavior of the jet shape are found. The second part of this article represents results on experimental investigation of nonsteady heat transfer and dynamics of the development of crisis phenomena at boiling of a falling subcooled liquid film in the conditions of stepwise heat release. The experimental data were obtained using synchronized high-speed infrared thermography and video. It is shown that with growth and condensation of vapor bubbles, on the liquid film interface appear large-amplitude waves that lead to considerably increasing local intensity of heat transfer. New data on the boiling incipience temperature in a subcooled liquid film, depending on the heat flux density, are obtained. It is found that the development of boiling crisis is a result of appearance of local dry patches and their subsequent growth by the mechanism of longitudinal thermal conductivity in the heat transfer wall as the equilibrium heat flux density is exceeded.     

Control of Alq3 wetting layer thickness via substrate surface functionalization

The effects of substrate surface energy and vapor deposition rate on the initial growth of porous columnar tris(8-hydroxyquinoline)aluminum (Alq3) nanostructures were investigated. Alq3 nanostructures thermally evaporated onto as-supplied Si substrates bearing an oxide were observed to form a solid wetting layer, likely caused by an interfacial energy mismatch between the substrate and Alq3. Wetting layer thickness control is important for potential optoelectronic applications. A dramatic decrease in wetting layer thickness was achieved by depositing Alq3 onto alkyltrichlorosilane-derivatized Si/oxide substrates. Similar effects were noted with increasing deposition rates. These two effects enable tailoring of the wetting layer thickness.     

Using atmospheric pressure plasma for enhancing the deposition of printing paste on cotton fabric for digital ink-jet printing

Atmospheric pressure plasma (APP) treatment was applied as a pretreatment process to enhance the deposition of printing paste in order to improve the final colour properties of digital ink-jet printed cotton fabrics. Three printing pastes containing natural polymers, i.e. (1) sodium alginate, (2) chitosan and (3) sodium alginate-chitosan mixture, were prepared separately. After APP treatment, cotton fabric was padded with different printing pastes prior to digital ink-jet printing. Experimental results showed that APP pretreatment could increase the colour yield of the digital ink-jet printed cotton fabric significantly even after washing. In addition, other properties such as colour fastness to crocking, colour fastness to laundering, outline sharpness and anti-bacterial properties were also improved when compared with those of the control cotton fabric printed without APP pretreatment. However, the influence of printing paste on the colour properties of the digital ink-jet printed cotton fabrics depended very much on the composition of the printing paste. The scanning electron microscope images evidenced that the APP treatment could enhance the deposition of printing paste on the cotton fabric surface as proved qualitatively by both the contact angle and wetting time measurement as well as quantitatively by both the X-ray photoelectron spectroscopy and carboxyl group/nitrogen content analysis.     

Current-driven resonances in magnetic multilayers

We describe complex variations in resistance of a Co/Cu multilayer, generated by injection of an adjustable dc current density ( approximately 10(9) A/cm(2)) via a point contact. We attribute these variations to coupling of current-induced spin waves to lattice vibrations, leading especially to current-driven resonant excitations of phonons. We propose a simple model to explain the observed structured behavior of the variations as a function of the applied current and magnetic field.     

The nature of in-plane skeleton Raman modes of P3HT and their correlation to the degree of molecular order in P3HT:PCBM blend thin films

The nature of main in-plane skeleton Raman modes (C=C and C-C stretch) of poly(3-hexylthiophene) (P3HT) in pristine and its blend thin films with [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) is studied by resonant and nonresonant Raman spectroscopy and Raman simulations. Under resonant conditions, the ordered phase of P3HT with respect to its disordered phase is identified by (a) a large shift in the C=C mode peak position to lower wavenumber (~21 cm(-1) shift), (b) a narrower fwhm of the C=C mode (~9 cm(-1) narrower), (c) a larger intensity of the C-C mode relative to the C=C mode (~56% larger), and (d) a very small Raman dispersion (~5 cm(-1)) of the C=C mode. The behavior of the C=C and C-C modes of the ordered and disordered phases of P3HT can be explained in terms of different molecular conformations. The C=C mode of P3HT in P3HT:PCBM blend films can be reproduced by simple superposition of the two peaks observed in different phases of P3HT (ordered and disordered). We quantify the molecular order of P3HT after blending with PCBM and the subsequent thermal annealing to be 42 ± 5% and 94 ± 5% in terms of the fraction of ordered P3HT phase, respectively. The increased molecular order of P3HT in blends upon annealing correlates well with enhanced device performance (J(SC), -4.79 to -8.72 mA/cm(2) and PCE, 1.07% to 3.39%). We demonstrate that Raman spectroscopy (particularly under resonant conditions) is a simple and powerful technique to study molecular order of conjugated polymers and their blend films.     

Existence ofdensities for functionals of the single jump process

By considering an integration-by-parts formula for functionals of a single jump process, conditions under which the densities of such functionals exist are given. A criterion under which the density to be in L^Pwith respect to the Lebesgue measure is also stated     

Stochastic dynamics of a Josephson fluxon in an inhomogeneous junction

A study is made of fluxon motion in a long Josephson junction with a local inhomogeneity (microresistor) in the presence of an alternating external current. Nonlinear resonances in the fluxon dynamics are considered. The process by which a fluxon trapped at an inhomogeneity is stochastically depinned under the influence of a periodic current is investigated analytically and numerically. Zh. Tekh. Fiz. 67, 57–61 (August 1997)     

Organic electroluminescence using polymer networks from smectic liquid crystals

We report the synthesis of a red light-emitting and photopolymerizable smectic liquid crystal (reactive mesogen). We investigate the suitability of polymer networks formed from smectic reactive mesogens for use in organic light-emitting diodes (OLEDs). The use of mixtures of smectic reactive mesogens is shown to lower the processing temperature for the fabrication of OLEDs to room temperature. We also report efficient energy transfer from a nematic polymer network host to a smectic light-emitting dopant and polarized emission from a polymer network formed from an aligned smectic reactive mesogen.