			Home About us Contact

Condensation Method (condensation + method)

Distribution by Scientific Domains

Polymers and Materials Science	80%

Selected Abstracts

Direct Condensation Method for the Preparation of Organic-Nanoparticle Dispersions

ADVANCED MATERIALS, Issue 24 2009
Stefan Köstler
Organic nanoparticle dispersions are prepared via a versatile technique. Particles are formed by evaporation of aromatic hydrocarbons (like pentacene, rubrene, and tetracene) in an inert atmosphere and condensation of the vapor in a liquid medium. This allows the preparation of stable and concentrated dispersions of organic nanoparticles, showing interesting optical properties and potential applications in organic electronics and sensors. [source]

A reduced-order modeling technique for tall buildings with active tuned mass damper

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2001
Zu-Qing Qu
Abstract It is impractical to install sensors on every floor of a tall building to measure the full state vector because of the large number of degrees of freedom. This makes it necessary to introduce reduced-order control. A kind of system reduction scheme (dynamic condensation method) is proposed in this paper. This method is iterative and Guyan condensation is looked upon as an initial approximation of the iteration. Since the reduced-order system is updated repeatedly until a desired one is obtained, the accuracy of the reduced-order system resulting from the proposed method is much higher than that obtained from the Guyan condensation method. Another advantage of the method is that the reduced-order system is defined in the subspace of the original physical space, which makes the state vectors have physical meaning. An eigenvalue shifting technique is applied to accelerate the convergence of iteration and to make the reduced system retain all the dynamic characteristics of the full system within a given frequency range. Two schemes to establish the reduced-order system by using the proposed method are also presented and discussed in this paper. The results for a tall building with active tuned mass damper show that the proposed method is efficient for the reduced-order modelling and the accuracy is very close to exact only after two iterations. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Well-Aligned ZnO Nanowire Arrays Fabricated on Silicon Substrates ,

ADVANCED FUNCTIONAL MATERIALS, Issue 6 2004
C. Geng
Abstract Arrays of well-aligned single-crystal zinc oxide (ZnO) nanowires of uniform diameter and length have been synthesized on a (100) silicon substrate via a simple horizontal double-tube system using chemical vapor transport and condensation method. X-ray diffraction and transmission electron microscopy (TEM) characterizations showed that the as-grown nanowires had the single-crystal hexagonal wurtzite structure with detectable defects and a <0002> growth direction. Raman spectra revealed phonon confinement effect when compared with those of ZnO bulk powder, nanoribbons, and nanoparticles. Photoluminescence exhibited strong ultraviolet emission at 3.29,eV under 355,nm excitation and green emission at 2.21,eV under 514.5,nm excitation. No catalyst particles were found at the tip of the nanowires, suggesting that the growth mechanism followed a self-catalyzed and saturated vapor,liquid,solid (VLS) model. Self-alignment of nanowires was attributed to the local balance and steady state of vapor flow at the substrate. The growth technique would be of particular interest for direct integration in the current silicon-technology-based optoelectronic devices. [source]

Electrostatic Charge Measurement and Charge Neutralization of Fine Aerosol Particles during the Generation Process

PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 5 2005
Chuen-Jinn Tsai
Abstract An aerosol charge analyzer has been constructed to measure the charge distribution of NaCl particles generated in the laboratory. A radioactive electrostatic charge neutralizer utilizing Po-210 was used to neutralize the electrostatic charge of the particles. The atomization technique was used to generate NaCl particles with diameters of 0.2 to 0.8 ,m, while the evaporation and condensation method was adopted to generate particles of 0.01 to 0.2 ,m in diameter. The experimental data demonstrates that the absolute average particle charge depends on the particle diameter, and is higher than that calculated by the Boltzmann charge equilibrium for particles within the range of 0.2 to 0.8 ,m. The charge increases with decreasing NaCl concentration. When these particles are neutralized using the Po-210 neutralizer, it is found that the electrostatic charge reaches the Boltzmann charge equilibrium. For 0.01 to 0.2 ,m NaCl particles generated using the evaporation and condensation method, test results show that the absolute average particle charge is higher than that calculated by the Boltzmann charge equilibrium for particles larger than 0.03 to 0.05 ,m in diameter, while it is lower than that predicted by the Fuchs theory [1], for particles smaller than 0.03 to 0.05 ,m. However, after charge neutralization, particles with diameter above 0.05 ,m reach the Boltzmann charge equilibrium condition, and the charges for particles with diameters of 0.010 to 0.05 ,m, agree well with Fuchs' theory. [source]

Mechanical properties of Al2O3/polymethylmethacrylate nanocomposites

POLYMER COMPOSITES, Issue 6 2002
Benjamin J. Ash
Alumina/polymethylmethacrylate (PMMA) nanocomposites were produced by incorporating alumina nanoparticles, synthesized using the forced gas condensation method, into methylmethacrylate. The particles were dispersed using sonication and the composites were polymerized using free radical polymerization. At an optimum weight percent, the resulting nanocomposites showed, on average, a 600% increase in the strain-to-failure and the appearance of a well-defined yield point when tested in uniaxial tension. Concurrently, the glass transition temperature (Tg) of the nanocomposites dropped by as much as 25°C, while the ultimate strength and the Young's modulus decreased by 20% and 15%, respectively. For comparison, composites containing micron size alumina particles were synthesized and displayed neither phenomenon. Solid-state deuterium NMR results showed enhanced chain mobility at room temperature in the nanocomposites and corroborate the observed Tg depression indicating considerable main chain motion at temperatures well below those observed in the neat polymer. A hypothesis is presented to relate the thermal and mechanical behavior observed in the composites to the higher chain mobility and Tg depression seen in recent ultrathin polymer film research. [source]