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Probe Method (probe + method)

Distribution by Scientific Domains

Polymers and Materials Science	50%
Physics and Astronomy	16%
Chemistry	16%

Selected Abstracts

Physical properties of Dy and La doped SnO2 thin films prepared by a cost effective vapour deposition technique

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2006
J. Joseph
Abstract Stannous oxide (SnO2) thin film is one of the most widely used n-type transparent semi-conductor films in electronics, electro-optics and solar energy conversion. By achieving controlled non-stoichiometry, we can get good transparency and high electrical conductivity simultaneously in SnO2 thin films. Dy and La doped SnO2 thin films have been prepared by a cost effective vapour deposition technique. The structural, photo-electronic, optical and electrical properties of the doped and undoped films were studied. The results of X-ray Diffraction studies reveals the polycrystalline nature of the films with preferential orientation along the (101), (211) and (301) planes and their average grain size variation for different deposition temperature. Photoconductivity and Photovoltaic studies of the films were also performed. The optical properties of these films were studied by measuring their optical transmission as a function of wavelength. The optical transmission is found to be increased on Dy doping and decreased on La doping. The band gap, refractive index and thickness of the films were calculated from U-V transmittance and Absorption graphs. The optical band gap of undoped film is found to be 4.08 eV, but on doping it shifts to lower energies and then increases on increasing the concentration of both dopants. Its electrical parameters such as sheet resistance, resistivity, mobility, Hall coefficient, and carrier concentration were determined by Four Probe, Van der Pauw and Hall Probe method. On doping with Dy, carrier conversion takes place from n-type to p-type and p-conductivity dominates. On La doping no carrier conversion takes place but resistivity decreases. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

A Phenomenological Probe Model of Fast Ion Measurement Using a Hybrid Directional Probe

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-7 2008
K. Nagaoka
Abstract A phenomenological probe model was developed for quantitative fast-ion-measurement using a hybrid directional probe (HDP), which is a directional probe to measure ion current and heat flux at the same position. The secondary electrons due to fast-ion-injection onto the probe surface enhances the ion-saturation-current, thus a thermal probe method was required for quantitative measurement of fast ions. The model gives a simple expression of the secondary electron yield as a function of ion currents and heat fluxes measured by the HDP, and can determine the net fast-ion-current without the calibrations of the thermal probe method. The model was applied to the experimental results of fast-ion-measurements using a HDP in CHS, and the secondary electron yield obtained by the model agrees with the calibration results of the HDP. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Silver Surface Iodination for Enhancing the Conductivity of Conductive Composites

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2010
Cheng Yang
Abstract The electrical conductivity of a silver microflake-filled conductive composites is dramatically improved after a filler surface treatment. By a simple iodine solution treatment, nonstoichiometric silver/silver iodide nanoislands form on the silver filler surface. Evidence of the decrease of surface silver oxide species is provided by TOF-SIMS and the redox property of the nanoclusters is studied using cyclic voltammetry and TOF-SIMS depth profile analyses. The redox property of the nanoclusters on silver flakes helps enhance the electrical conductivity of the conductive composites. The electrical resistivity of the improved conductive composites is measured by four-point probe method; the reliability of the printed thin film resistors is evaluated by both the 85 °C/85% relative humidity moisture exposure and the ,40 , 125 °C thermal cycling exposure. The conductive composite printed radio frequency identification (RFID) antennas with 27.5 wt% of the modified silver flake content show comparable performance in the RFID tag read range versus copper foil antennas, and better than those commercial conductive adhesives that require much higher silver content (i.e., 80 wt%). This work suggests that a surface chemistry method can significantly reduce the percolation threshold of the loading level of the silver flakes and improve the electrical conductivity of an important printed electronic passive component. [source]

Silver Surface Iodination for Enhancing the Conductivity of Conductive Composites

Temperature measurements near a heating surface at high heat fluxes in subcooled pool boiling

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 1 2010
Ayako Ono
Abstract In previous papers (Int J Heat Mass Transfer, 2008;50:3481,3489, 2009;52: 814,821), the authors conducted measurements of liquid,vapor structures in the vicinity of a heating surface for subcooled pool boiling on an upward-facing copper surface by using a conducting probe method. We reported that the macrolayer dryout model is the most appropriate model of the CHF and that the reason why the CHF increases with increasing subcooling is most likely that a thick macrolayer is able to form beneath large vapor masses and the lowest heat flux of the vapor mass region shifts towards the higher heat flux. To develop a mechanistic model of the CHF for subcooled boiling, therefore, it is necessary to elucidate the effects of local subcooling on boiling behaviors in the vicinity of a heating surface. This paper measured local temperatures close to a heating surface using a micro-thermocouple at high heat fluxes for water boiling on an upward-facing surface in the 0 to 40 K range of subcooling. A value for the effective subcooling, defined as the local subcooling during the period while vapor masses are being formed was estimated from the detected bottom peaks of the temperature fluctuations. It was established that the effective subcooling adjacent to the surface remains at considerably lower values than the bulk liquid subcooling. This suggests that, from nucleation to coalescence, the subcooling of a bulk liquid has a smaller effect on the behavior of primary bubbles than the extent of the subcooling would appear to suggest. An empirical correlation of the effective subcooling is proposed to provide a step towards quantitative modeling of the CHF for subcooled boiling. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20277 [source]

Ultraviolet curing of acrylic systems: Real-time Fourier transform infrared, mechanical, and fluorescence studies

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2002
Carmen Peinado
Abstract The photopolymerization of acrylic-based adhesives has been studied by Fourier transform infrared and fluorescence analysis in real time. Real-time infrared spectroscopy reveals the influence of the nature of the photoinitiator on the kinetics of the reaction. Furthermore, the incident light intensity dependence of the polymerization rate shows that primary radical termination is the predominant mechanism during the initial stages of the curing of the acrylic system with bis(2,4,6-trimethylbenzoyl) phenyl phosphine oxide (TMBAPO) as a photoinitiator. The fluorescence intensity of selected probes increases during the ultraviolet curing of the adhesive, sensing microenvironmental viscosity changes. Depending on the nature of the photoinitiator, different fluorescence,conversion curves are observed. For TMBAPO, the fluorescence increases more slowly during the initial stage because of the delay in the gel effect induced by primary radical termination. Mechanical tests have been carried out to determine the shear modulus over the course of the acrylic adhesive ultraviolet curing. In an attempt to extend the applications of the fluorescence probe method, we have undertaken comparisons between the fluorescence changes and shear modulus. Similar features in both curves confirm the feasibility of the fluorescence method for providing information about microstructural changes during network formation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4236,4244, 2002 [source]

Carbon Nanotube-Adsorbed Electrospun Nanofibrous Membranes of Nylon 6

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 2 2006
Hyun Suk Kim
Abstract Summary: A simple and mass-producible method was developed to densely assemble multiwalled carbon nanotubes (MWNTs) onto electrospun nylon 6 nanofibrous membranes. The process consists of dispersing the acid-treated MWNTs in surfactant solutions or organic solvents, and dipping the nanofibrous membranes in the resulting dispersion for only 60 seconds, followed by the extraction of the surfactants in pure water and drying. The conductivity of the MWNT-adsorbed nanofibrous membranes ranges from 2.2,×,10,2 to 1.5,×,10,1 S,·,cm,1, as determined by the four probe method, which implies that the MWNTs are adsorbed uniformly and densely along the nanofibrous membranes. Furthermore, the results suggest that there is a strong interaction between the acid-treated MWNTs and nylon 6. We also investigate the amount of MWNTs present in the membranes using thermogravimetric analysis. SEM images of the non-woven fibrous nylon 6 membranes after dip-coating in a dispersion of the MWNTs in surfactant-containing water. [source]

Reconstruction of cracks of different types from far-field measurements

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 8 2010
Jijun Liu
Abstract In this paper, we deal with the acoustic inverse scattering problem for reconstructing cracks of possibly different types from the far-field map. The scattering problem models the diffraction of waves by thin two-sided cylindrical screens. The cracks are characterized by their shapes, the type of boundary conditions and the boundary coefficients (surface impedance). We give explicit formulas of the indicator function of the probe method, which can be used to reconstruct the shape of the cracks, distinguish their types of boundary conditions, the two faces of each of them and reconstruct the possible material coefficients on them by using the far-field map. To test the validity of these formulas, we present some numerical implementations for a single crack, which show the efficiency of the proposed method for suitably distributed surface impedances. The difficulties for numerically recovering the properties of the crack in the concave side as well as near the tips are presented and some explanations are given. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Analysis of time-resolved X-ray scattering data from solution-state systems

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 2 2010
Kristoffer Haldrup
As ultrafast time-resolved studies of liquid systems with the laser pump/X-ray scattering probe method have come of age over the past decade, several groups have developed methods for the analysis of such X-ray scattering data. The present article describes a method developed primarily with a focus on determining structural parameters in the excited states of medium-sized molecules (~30 atoms) in solution. The general methodology is set in a maximum-likelihood framework and is introduced through the analysis of the photoactive platinum compound PtPOP, in particular the structure of its lowest triplet excited state (3A2u). Emphasis is put on structure determination in terms of model comparisons and on the information content of difference scattering signals as well as the related experimental variables. Several suggestions for improving the accuracy of these types of measurements are presented. [source]

The study of the miscibility and morphology of poly(styrene-co-4-vinylphenol)/poly(propylene carbonate) blends

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 8 2004
Furong Qiu
Abstract Blends of poly(propylene carbonate) (PPC) with copolymer poly(styrene-co-4-vinyl phenol) (STVPh) have been studied by electron spin resonance (ESR) spin probe method and Raman spectroscopy. The ESR results indicated that the nitroxide radical existed in a PPC-rich and an STVPh-rich micro domain in the blends, corresponding to the fast-motion and slow-motion component in the ESR spectra, respectively. And in the temperature dependence composite spectra, the fast-motion fraction increased with increasing the hydroxyl group content in copolymer STVPh. Moreover, the ESR parameter T5mT, rotational correlation times (,c) and activation energies (Ea) showed similar dependence on the hydroxyl group content as the fast-motion fraction. It resulted from the enhancement of the hydrogen-bonding interaction between the hydroxyl groups in STVPh and the carboxyl groups and ether oxygen in PPC. However, the distinct band shift and intensity change among the Raman spectra of pure polymer components and those of the blends were observed. In the carboxyl-stretching region, the band shifted to lower frequency with increasing the hydroxyl groups. Furthermore, the phase morphologies of the blends were obtained by optical microscopy. All could be concluded that the hydrogen-bonding interaction between the two components was progressively favorable to the mixing process and was the driving force for the miscibility enhancement in the blends. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Chemical and electrochemical synthesis of homopolymer and copolymers of 3-methoxyethoxythiophene with aniline, thiophene and pyrrole for studies of their gas and vapour sensing

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2001
S. Hossein Hosseini
Abstract Herein we report chemical and electrochemical formation of poly(3-methoxyethoxythiophene) and its copolymers with aniline, thiophene and pyrrole which give highly conducting polymeric materials. These are soluble in common organic solvents in the conducting state. The response mechanism of these compounds, to a selection of gases and vapours, was investigated using two techniques: measurement of conductance and mass changes using a four probe method and X-ray fluorescence (XRF) device, respectively. Prepared films were exposed to hydrogen halides, hydrogen cyanide, halogens, monochloroacetic acid (MCAA), 1-3-5 trichloromethylbenzene (TCMB), methylbenzyl bromide (MBB), bromoacetone (BA) and cyanogen bromide (CB). These gas sensors may have advantages compared to other sensors in their ability to operate at room temperature, low concentration, stability in air, sufficient diffusion and their selectivity. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Properties of 2,2,2-Trifluoroethanol/Water Mixtures: Acidity, Basicity, and Dipolarity

HELVETICA CHIMICA ACTA, Issue 2 2005
Paz Sevilla, Sierra
In this report, we focus our attention on the characterization of 2,2,2-trifluoroethanol(TFE)/H2O mixtures and describe their intrinsic parameters; i.e., solvent acidity (SA), solvent basicity (SB), and solvent dipolarity/polarizability (SPP), by the probe/homomorph-couple method for a range of mixtures from 0,100% (v/v) TFE. Variation of these parameters is not linear and has a singular and unpredictable behavior depending on the precise composition of the mixture. Based on these parameters, we describe the TFE-induced changes in some physical properties; i.e., viscosity (,), partial molar volume (V,), density (,), dielectric constant (,), vapor pressure (pv), and spectroscopic properties; i.e., NMR chemical shifts (,(1H)) of TFE Me group for all molar fractions studied. In addition, by means of CD studies, we report that formation of the secondary structure, as percentage of helical content, ,, of a polypeptide, poly(L -lysine), in several TFE/H2O mixtures is adequately described by these mixture parameters. SA, SB, and SPP of TFE/H2O mixtures provide an excellent tool for the interpretation of formation and stability of intramolecular H-bonds, and, thus, of secondary structures in polypeptides. [source]