Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Evaporation

  • laser evaporation
  • pan evaporation
  • potential evaporation
  • slow evaporation
  • soil evaporation
  • solvent evaporation
  • thermal evaporation
  • water evaporation

  • Terms modified by Evaporation

  • evaporation method
  • evaporation process
  • evaporation rate
  • evaporation technique
  • evaporation techniques
  • evaporation time

  • Selected Abstracts

    An Approach to the Synthesis of Silicon Carbide Nanowires by Simple Thermal Evaporation of Ferrocene onto Silicon Wafers

    Jun-Jie Niu
    Abstract Scales of silicon carbide nanowires (SiC-NWs) with high quality were synthesized by direct thermal evaporation of ferrocene onto silicon wafers at high temperature. Ferrocene decomposed into iron and carbon, which was subsequently treated with silicon to form SiC-NWs at high temperature. The SiC-NWs possess small diameters of , 20 nm and lengths of several ,ms. Furthermore, the samples show a uniform morphology, crystalline structure, and a very thin oxide layer. The main crystal direction of [111] was confirmed by high-resolution field-emission-transmission electron microscopy (HR-FETEM). The Raman scattering spectra showed two peaks at , 796 (TO) and , 980 cm,1 (LO) with varying intensity ratios at different positions. The band line fluctuation was contributed to the Raman selection rules. With reference to the experimental results, we suggested a tentative growth model according to the vapor,liquid,solid (VLS) mechanism. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Matrix Assisted Pulsed Laser Evaporation (MAPLE) of Poly(D,L lactide) (PDLLA) on Three Dimensional Bioglass® Structures

    Valeria Califano
    Matrix assisted pulsed laser evaporation (MAPLE) was used to coat Bioglass-based tissue engineering scaffolds with poly(D,L lactide). The polymer penetrated to some extent from the surface producing a graded porous composite material. This structure can be beneficial for application in osteochondral tissue engineering, where composite scaffolds are required exhibiting two distinct regions, one for cartilage integration (biopolymer) and the other one for bone contact (bioactive glass). [source]

    Modelling lake stage and water balance of Lake Tana, Ethiopia

    Yirgalem A. Chebud
    Abstract The level of Lake Tana, Ethiopia, fluctuates annually and seasonally following the patterns of changes in precipitation. In this study, a mass balance approach is used to estimate the hydrological balance of the lake. Water influx from four major rivers, subsurface inflow from the floodplains, precipitation, outflow from the lake constituting river discharge and evapotranspiration from the lake are analysed on monthly and annual bases. Spatial interpolation of precipitation using rain gauge data was conducted using kriging. Outflow from the lake was identified as the evaporation from the lake's surface as well as discharge at the outlet where the Blue Nile commences. Groundwater inflow is estimated using MODular three-dimensional finite-difference ground-water FLOW model software that showed an aligned flow pattern to the river channels. The groundwater outflow is considered negligible based on the secondary sources that confirmed the absence of lake water geochemical mixing outside of the basin. Evaporation is estimated using Penman's, Meyer's and Thornwaite's methods to compare the mass balance and energy balance approaches. Meteorological data, satellite images and temperature perturbation simulations from Global Historical Climate Network of National Oceanographic and Atmospheric Administration are employed for estimation of evaporation input parameters. The difference of the inflow and outflow was taken as storage in depth and compared with the measured water level fluctuations. The study has shown that the monthly and annually calculated lake level replicates the observed values with root mean square error value of 0·17 and 0·15 m, respectively. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Moss beneath a leafless larch canopy: influence on water and energy balances in the southern mountainous taiga of eastern Siberia

    Kazuyoshi Suzuki
    Abstract The southern mountainous taiga of eastern Siberia has a sparse larch canopy and an understory dominated by a thick moss layer. The physiology of moss is very different from that of other plants, as mosses lack roots and vascular systems and take up water directly. During May 2002, we conducted hydrological and meteorological measurements in the taiga of eastern Siberia to investigate the role of understory moss on water and energy balances within a leafless larch forest. We found that below-leafless canopy net all-wave radiation partitions into 39% latent heat flux and 39% sensible heat flux, while the mean daily Bowen ratio is about 1. Ground heat flux on the moss surface is also an important factor, as it comprises 22% of net all-wave radiation. Evaporation from moss beneath the leafless canopy was 24 mm during the 1-month observation period, representing 23% of the water flux into the larch forest. This finding implies that moss intercepted 23% of the water flux into the larch forest. In addition, evaporation from the moss understory during May 2002 comprised 22% of total evapotranspiration previously estimated above the canopy (April,October 2001). We conclude that moss is an important component of the water and energy balance in larch forests in the taiga region. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    A new approach to measuring the aerodynamic resistance to evaporation within a northern peatland using a modified Bellani plate atmometer

    Nicholas Kettridge
    Abstract This study considers evaporation from northern peatlands, which are important global stores of soil carbon. Evaporation is commonly simulated using the Penman,Monteith model. The model incorporates the aerodynamic resistance to vapour transfer (ra), which can currently only be measured using expensive, labour intensive micro-meteorological methods. A new approach to measuring ra is presented. The approach involves accurately measuring the evaporation from a modified Bellani plate atmometer, of known surface resistance and temperature. With knowledge of basic meteorological parameters, ra can then be calculated. The approach is compared to modelled resistances within a northern peatland: no significant difference was found between modelled and measured ra. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Desorption kinetics of model polar stratospheric cloud films measured using Fourier Transform Infrared Spectroscopy and Temperature-Programmed Desorption

    Birgit G. Koehler
    This study combines Fourier transform infrared (FTIR) spectroscopy and temperature-programmed desorption to examine the evaporation kinetics of thin films of crystalline nitric acid hydrates, solid amorphous H2O/HNO3 mixtures, H2O,ice, ice coated with HCl, and solid HNO3. IR spectroscopy measured the thickness of each film as it evaporated, either at constant temperature or during a linear temperature ramp (temperature-programmed infrared, TPIR). Simultaneously, a mass spectrometer measured the rate of evaporation directly by monitoring the evolution of the molecules into the gas phase (temperature-programmed desorption, TPD). Both TPIR and TPD data provide a measurement of the desorption rate and yield the activation energy and preexponential factor for desorption. TPD measurements have the advantage of producing many data points but are subject to interference from experimental difficulties such as uneven heating from the edge of a sample and sample-support as well as pumping-speed limitations. TPIR experiments give clean but fewer data points. Evaporation occurred between 170 and 215 K for the various films. Ice evaporates with an activation energy of 12.9 ± 1 kcal/mol and a preexponential factor of 1 × 1032±1.5 molec/cm2 s, in good agreement with the literature. The beta form of nitric acid trihydrate, ,,NAT, has an Edes of 15.6 ± 2 kcal/mol with log A = 34.3 ± 2.3; the alpha form of nitric acid trihydrate, ,,NAT, is around 17.7 ± 3 kcal/mol with log A = 37.2 ± 4. For nitric acid dihydrate, NAD, Edes is 17.3 ± 2 kcal/mol with log A = 35.9 ± 2.6; for nitric acid monohydrate, NAM, Edes is 13 ± 3 kcal/mol with log A = 31.4 ± 3. The ,,NAT converts to ,,NAT during evaporation, and the amorphous solid H2O/HNO3 mixtures crystallize during evaporation. The barrier to evaporation for pure nitric acid is 14.6 ± 3 kcal/mol with log A = 34.4 ± 3. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 295,309, 2001 [source]

    Evaporation of a model skin lotion with beta-hydroxy acids

    A. Al Bawab
    Synopsis Two , -hydroxy acids, malic and salicylic acids were combined with a non-ionic surfactant, a commercial pentaoxyethylene sorbitan mono-oleate and water to form a simple model of a skin lotion and the phase diagrams were determined. One emulsion formulation with relative amounts of the three components similar to those in commercial lotions was used to observe microscopically the changes in the emulsion structure during evaporation. The microscope images were subsequently compared to the information from the phase diagram under equilibrium conditions. The results showed the behavior of the systems of the two acids to be distinctly different; as exemplified by that of a typical formulation with 3% by weight of acid and 5% of surfactant. The malic acid system consisted of vesicles, exclusively formed by the surfactant and water, in an aqueous molecular solution of the acid and the initial evaporation resulted in an increase of the acid concentration in the aqueous solution to reach 35.5%, before solid crystals of the acid solid solution appeared. The salicylic acid formulation, on the other hand, already at the beginning of the determination consisted of water, particles of the acid solid solution and surfactant vesicles. In both cases the remaining deposit after total evaporation was particles of a solid acid solution and liquid surfactant. Résumé Deux acides , -hydroxy malique et salicylique ont été combinés avec un surfactant non ionique, un pentaoxyethylene sorbitan mono-oleate commercial et de l'eau pour former un model simple de lotion pour la peau. Leurs diagrammes de phase ont été déterminés. Une formule d'émulsion avec une quantité relative des trois composantes similaire a celles des lotions commerciales a été utilisée pour observer les changements microscopiques dans la structure de l'émulsion au cours de l,évaporation. Les images du microscope ont été ensuite comparées aux informations des diagrammes de phase dans les conditions d'équilibre. Les résultats ont montré que le comportement des systémes des deux acides est clairement différent, comme le montre l'exemple d'une formulation typique à 3% du poids d'acide et 5% du surfactant. Le système d'acide malique est constitué de vésicules exclusivement formées du surfactant et d'eau, dans une solution aqueuse moléculaire de l'acide, et l'évaporation initiale a eu comme consèquence l'augmentation de la concentration de l'acide en solution aqueuse qui a atteint 35.5% avant l'apparition des cristaux de la solution de l'acide solide. D'autre part la formulation de l'acide salicylique des le début de la détermination fut constituée d'eau, de particules de solution de l'acide solide et des vésicules du surfactant. Dans les deux cas les restes déposés après l'évaporation totale ètaient constitués des particules de la solution solide d'acide et du liquide surfactant. [source]

    Two-stage kinetic analysis of fragrance evaporation and absorption from skin

    P. Saiyasombati
    Synopsis Human in vivo fragrance evaporation data from a previously published study are reanalysed in terms of compartmental pharmacokinetic models in which the microscopic rate constants are functions of the physicochemical properties of the fragrance components. According to the proposed analysis, which is restricted to low doses, absorption and evaporation of each component are first-order processes occurring from either the skin (one-compartment model) or the skin and a more rapidly depleted vehicle layer (two-compartment models). Evaporation rates of ingredients from a 12-component mixture containing a musk fixative followed single exponential decays that were well described by the one-compartment model. An otherwise identical mixture without fixative yielded evaporation rates that could be characterized as biexponential decays associated with loss from two compartments. This result shows that ingredient interactions qualitatively and quantitatively change evaporation rate profiles of fragrance components; however, an attempt to account for these interactions explicitly by means of activity coefficients inserted as multipliers for the microscopic rate constants was unsuccessful. Re-examination of this approach in the context of a diffusion/evaporation model is suggested. The developed models have potential utility for dermal risk assessment and for prediction of aroma evolution following topical application of complex fragrances. Résumé Des données d'une étude publiée précédemment sur l'évaporation de parfum de humaine in vivo sont réanalysées en utilisant des modèles pharmacocinétiques compartimentés dont les constants microscopiques de taux sont des functions des propriétés physio-chimiques des composants de parfum. Selon l'analyse proposée, qui est limitée aux petites doses, l'absorption et l'évaporation de chaque composant sont des processus de premier ordre se produisant l'un de la peau (modèle d'un compartiment), ou l'autre de la peau et d'une couche de véhicule plus rapidement épuisée (modèles de deux compartiments). Les taux d'évaporation d'ingrédients d'un mélange de 12 composants contenant un fixatif de musc suivi par des décompositions exponentielles uniques qui ont été bien décrites par le modèle d'un compartiment. Un mélange sans fixatif mais identique pour le reste a rapporté des taux d'évaporation qui pourraient être caractérisés commes des décompositions bi-exponentielles avec une perte de deux compartiments. Ce résultat montre que les interactions d'ingrédient changent qualitativement et quantitativement les profils de taux d'évaporation des composants de parfum. Cependant, une tentative d'expliquer précisement ces interactions au moyen des coefficients d'activité insérés comme multiplicateurs pour les constants microscopiques de taux n'a pas été réussie. Le réexamen de cette approche dans le contexte d'un modèle de diffusion/evaporation est suggéré. Les modèles développés ont une utilité potentielle dans l'évaluation des risques cutané et pour la prévision de l'évolution d'arome suivant l'application topique des parfums complexes. [source]

    Air temperature effect on spray evaporation in sprinkler irrigation,

    Dr Giulio Lorenzini
    évaporation aérienne; irrigation par arroseur; équipement expérimental Abstract The temperature effect of the surrounding environment on mean steady aerial water evaporation in sprinkler irrigation is investigated. An experimental set-up was designed and built to work at opportune operating conditions holding all the other variables constant to minimise the experimental error. One hundred and thirty-seven tests were performed for this work, of which 81 were considered valid for a statistical analysis of the data measured. Evaporation ranged from 4.15 to 7.73% as the air temperature varied from 21.0 to 27.0° C. Results show a clear dependence of sprinkler water evaporation on air temperature with a logarithmic relation. Further investigations will examine broader temperature intervals to improve the assessment and will consider the effects due to other parameters affecting the phenomenon. Copyright © 2002 John Wiley & Sons, Ltd. Résumé Les effets de la température de l'environnement sur l'irrigation par arroseur ont été examinés. Un eq,uipement expérimental a été conçu et créé pour fonctionner dans des conditions d'emploi propices, et on a travaillé aussi pour tenir les autres variables le plus possible constantes pour minimiser l'erreur expérimentale. On a réalisé 137 tests et seulement 81 ont été considérés bons pour l'analyse statistique. On a vu que l'évaporation change de 4.15 à 7.73 pour cent avec le changement de température de 21.0 à 27.0° C. Les résultats montrent une claire dépendance logarithmique de l'évaporation avec la température de l'air. On propose dans le futur d'étendre l'intervalle des températures pour confirmer les résultats déjà vus et aussi de tester les influences d'autres variables d'intérêt pour ce phénomène. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Evaporation of pyrolysis oil: Product distribution and residue char analysis

    AICHE JOURNAL, Issue 8 2010
    Guus van Rossum
    Abstract The evaporation of pyrolysis oil was studied at varying heating rates (,1,106°C/min) with surrounding temperatures up to 850°C. A total product distribution (gas, vapor, and char) was measured using two atomizers with different droplet sizes. It was shown that with very high heating rates (,106°C/min) the amount of char was significantly lowered (,8%, carbon basis) compared to the maximum amount, which was produced at low heating rates using a TGA (,30%, carbon basis; heating rate 1°C/min). The char formation takes place in the 100,350°C liquid temperature range due to polymerization reactions of compounds in the pyrolysis oil. All pyrolysis oil fractions (whole oil, pyrolytic lignin, glucose and aqueous rich/lean phase) showed charring behavior. The pyrolysis oil chars age when subjected to elevated temperatures (,700°C), show similar reactivity toward combustion and steam gasification compared with chars produced during fast pyrolysis of solid biomass. However, the structure is totally different where the pyrolysis oil char is very light and fluffy. To use the produced char in conversion processes (energy or syngas production), it will have to be anchored to a carrier. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source]

    Nanoparticle formation through solid-fed flame synthesis: Experiment and modeling

    AICHE JOURNAL, Issue 4 2009
    W. Widiyastuti
    Abstract The preparation of silica nanoparticles through solid-fed flame synthesis was investigated experimentally and theoretically. Monodispersed submicrometer- and micrometer-sized silica powders were selected as solid precursors for feeding into a flame reactor. The effects of flame temperature, residence time, and precursor particle size were investigated systematically. Silica nanoparticles were formed by the nucleation, coagulation, and surface growth of the generated silica vapors due to the solid precursor evaporation. Numerical modeling was conducted to describe the mechanism of nanoparticle formation. Evaporation of the initial silica particles was considered in the modeling, accounting for its size evolution. Simultaneous mass transfer modeling due to the silica evaporation was solved in combination with a general dynamics equation solution. The modeling and experimental results were in agreement. Both results showed that the methane flow rate, carrier gas flow rate, and initial particle size influenced the effectiveness of nanoparticle formation in solid-fed flame synthesis. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

    Dryout phenomena in a three-phase fixed-bed reactor

    AICHE JOURNAL, Issue 1 2003
    Zhen-Min Cheng
    Understanding the mechanism of liquid-phase evaporation in a three-phase fixed-bed reactor is of practical importance, because the reaction heat is usually 7,10 times the vaporization heat of the liquid components. Evaporation, especially the liquid dryout, can largely influence the reactor performance and even safety. To predict the vanishing condition of the liquid phase, Raoult's law was applied as a preliminary approach, with the liquid vanishing temperature defined based on a liquid flow rate of zero. While providing correct trends, Raoult's law exhibits some limitation in explaining the temperature profile in the reactor. To comprehensively understand the whole process of liquid evaporation, a set of experiments on inlet temperature, catalyst activity, liquid flow rate, gas flow rate, and operation pressure were carried out. A liquid-region length-predicting equation is suggested based on these experiments and the principle of heat balance. [source]

    The Role of Ground Water in Generating Streamflow in Headwater Areas and in Maintaining Base Flow,

    Thomas C. Winter
    Abstract:, The volume and sustainability of streamflow from headwaters to downstream reaches commonly depend on contributions from ground water. Streams that begin in extensive aquifers generally have a stable point of origin and substantial discharge in their headwaters. In contrast, streams that begin as discharge from rocks or sediments having low permeability have a point of origin that moves up and down the channel seasonally, have small incipient discharge, and commonly go dry. Nearly all streams need to have some contribution from ground water in order to provide reliable habitat for aquatic organisms. Natural processes and human activities can have a substantial effect on the flow of streams between their headwaters and downstream reaches. Streams lose water to ground water when and where their head is higher than the contiguous water table. Although very common in arid regions, loss of stream water to ground water also is relatively common in humid regions. Evaporation, as well as transpiration from riparian vegetation, causing ground-water levels to decline also can cause loss of stream water. Human withdrawal of ground water commonly causes streamflow to decline, and in some regions has caused streams to cease flowing. [source]

    Electrospray: From ions in solution to ions in the gas phase, what we know now

    Paul Kebarle
    Abstract There is an advantage for users of electrospray and nanospray mass spectrometry to have an understanding of the processes involved in the conversion of the ions present in the solution to ions in the gas phase. The following processes are considered: Creation of charge droplets at the capillary tip; Electrical potentials required and possibility of gas discharges; Evolution of charged droplets, due to solvent evaporation and Coulomb explosions, to very small droplets that are the precursors of the gas phase ions; Production of gas phase ions from these droplets via the Ion Evaporation and Charge residue models; Analytical uses of ESIMS of small ions, qualitative and quantitative analysis; Effects of the ESI mechanism on the analysis of proteins and protein complexes; Determination of stability constants of protein complexes; Role of additives such as ammonium acetate on the observed mass spectra. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 28:898,917, 2009 [source]

    Nanocomposite AlTiNCO Coatings Deposited by Reactive Cathodic Arc Evaporation

    Jörg Vetter
    Abstract AlTiNCO coatings were deposited by the reactive cathodic arc evaporation. In addition, TiNC coatings with different carbon contents were deposited to compare the influence of carbon addition on the oxidation depth between TiNC and AlTiNCO coatings. Variations in microstructure, morphology, and chemical composition were correlated with mechanical properties. High-resolution transmission electron microscopy revealed that nanocrystalline phases are present. Higher carbon contents lead to the precipitation of free carbon resulting in a nanocomposite structure of AlTiNCO/C. Raman spectroscopy of the nanocomposite structure showed spectra typical of nanocrystalline carbon. It was shown that the additional carbon had a positive influence on the cutting performance in dry cutting. [source]

    Evaporation of solvent molecules by ultrafast heating: effect on conformation of solvated protein

    Saravana Prakash Thirumuruganandham
    Using molecular dynamics simulation, we compare two cases of ultrafast heating of a small water droplet containing a solvated protein (echistatin). If the water temperature after irradiation is above the critical temperature, explosive boiling liberates the protein within some 10,ps of its hydration shell, while its temperature remains relatively low. By comparing with the case where the water shell is heated to the same final temperature, but without complete evaporation, we demonstrate that the protein conformation is governed by the hydration shell rather than by the protein temperature. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Carbon and Oxygen Isotopic Composition of Surface-Sediment Carbonate in Bosten Lake (Xinjiang, China) and its Controlling Factors

    Chengjun ZHANG
    Abstract: Bosten Lake is a mid-latitude lake with water mainly supplied by melting ice and snow in the Tianshan Mountains. The depositional environment of the lake is spatially not uniform due to the proximity of the major inlet and the single outlet in the western part of the lake. The analytical results show that the carbon and oxygen isotopic composition of recent lake sediments is related to this specific lacustrine depositional environment and to the resulting carbonate mineralogy. In the southwestern lake region between the Kaidu River inlet and the Kongqi River outlet, carbon isotope composition (,13C) values of the carbonate sediment (,1, to ,2,) have no relation to the oxygen isotope composition of the carbonate (,18O) values (,7, to ,8,), with both isotopes showing a low variability. The carbonate content is low (<20%). Carbonate minerals analyzed by X-ray diffraction are mainly composed of calcite, while aragonite was not recorded. The salinity of the lake water is low in the estuary region as a result of the Kaidu River inflow. In comparison, the carbon and oxygen isotope values are higher in the middle and eastern parts of the lake, with ,13C values between approximately +0.5, and +3,, and ,18O values between ,1, and ,5,. There is a moderate correlation between the stable oxygen and carbon isotopes, with a coefficient of correlation r of approximately 0.63. This implies that the lake water has a relatively short residence time. Carbonate minerals constitute calcite and aragonite in the middle and eastern region of the lake. Aragonite and Mg,calcite are formed at higher lake water salinity and temperatures, and larger evaporation effects. More saline lake water in the middle and eastern region of the lake and the enhanced isotopic equilibrium between water and atmospheric CO2 cause the correlating carbon and oxygen isotope values determined for aragonite and Mg,calcite. Evaporation and biological processes are the main reasons for the salinity and carbonate mineralogy influence of the surface-sediment carbonate in Bosten Lake. The lake water residence time and the CO2 exchange between the atmosphere and the water body control the carbon and oxygen isotope composition of the carbonate sediment. In addition, organic matter pollution and decomposition result in the abnormally low carbon isotope values of the lake surface-sediment carbonate. [source]

    Evaporation of Water Microdroplets on Self-Assembled Monolayers: From Pinning to Shrinking

    CHEMPHYSCHEM, Issue 7 2004
    Hua-Zhong Yu Prof.
    The great escape: Mixed , -terminated self-assembled monolayers (SAMs) were explored as model surfaces to understand fundamental aspects of liquid evaporation phenomena on solids. The authors demonstrate that on these SAMs the evaporation of water microdroplets follows an exclusive trend. Despite the different wettabilities of the surfaces, the evaporation of water microdroplets switches from a constant contact area ("pinning") to a constant contact angle mode ("shrinking"). [source]

    Preparation, structure and photoluminescence properties of SiO2,coated ZnS nanowires

    Changhyun Jin
    Abstract It is essential to passivate one-dimensional (1D) nanostructures with insulating materials to avoid crosstalking as well as to protect them from contamination and oxidation. The structure and influence of thermal annealing on the photoluminescence properties of ZnS-core/SiO2 -shell nanowires synthesized by the thermal evaporation of ZnS powders followed by the sputter deposition of SiO2 were investigated. Transmission electron microscopy and X-ray diffraction analyses revealed that the cores and shells of the core-shell nanowires were single crystal zinc blende-type ZnO and amorphous SiO2, respectively. Photoluminescence (PL) measurement showed that the core-shell nanowires had a green emission band centered at around 525 nm with a shoulder at around 385 nm. The PL emission of the core-shell nanowires was enhanced in intensity by annealing in an oxidative atmosphere and further enhanced by subsequently annealing in a reducing atmosphere. Also the origin of the enhancement of the green emission by annealing is discussed based on the energy-dispersive X-ray spectroscopy analysis results. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Investigation of growth kinetics and morphology of sodium fluorosilicate ice-analogue crystals in solutions and gels

    M. J. Krasi
    Abstract The effect of growth method (solution or gel growth) and growth conditions on the morphology of ice analogue crystals (sodium fluorosilicate) has been studied. Many habits typical for atmospheric ice crystals (hexagonal columns, plates, different types of stars or dendrites) were obtained during experiments. The dependence of growth rate of basal and prism faces of columnar crystals on supersaturation was measured for crystals growing by evaporation of solvent. The experiments establish evaporation rate and growth rate ranges at which appearance of certain types of crystals is most probable. The experiments have also shown that good quality sodium fluorosilicate crystals can be obtained in TMS gel. These crystals were significantly bigger than those obtained in solution. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Growth and characterization of magneto-optical YFeO3 crystals

    Hui Shen
    Abstract The floating zone growth of magneto-optical crystal YFeO3 has been investigated. The polycrystalline feed rod was prepared by a pressure of 250MPa and sintering at about 1500°C. A crack- free YFeO3 single crystal has been successfully grown. The crystal preferred to crystallize along <100> direction with about 10° deviation. The X-ray rocking curve of the crystal has a FWHM of 24 arcsec, confirming the high crystal quality of the sample. The (100) plane was etched by hot phosphoric acid and the dislocation density was about 104/cm2. A thin outer layer with Y2O3 -rich composition was found at the periphery of as-grown crystals, which was attributed to the Fe2O3 evaporation during growth. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Effect of different metal ions on structural, thermal, spectroscopic and optical properties of ATCC and ATMC single crystals

    R. Perumal
    Abstract A novel metal-organic coordination complex nonlinear optical crystals, tri-allylthiourea cadmium chloride [(CdCl2(AT)3] and tri-allylthiourea mercury chloride [(HgCl2(AT)3] abbreviated as ATCC, ATMC (AT is Allylthiourea i.e.,CH2=CHCH2NHCSNH2) has been synthesized and grown as single crystals. It was synthesized in deionised water and further recrystallized to improve its purity. Single crystals of the allylthiourea co-ordination complex nonlinear optical crystals tri allylthiourea cadmium chloride (ATCC) with dimensions of 14x14x10 mm3 and tri allylthiourea mercury chloride (ATMC) with dimensions of 15x15x12 mm3 were grown successfully from aqueous solution by solvent evaporation as well as by temperature lowering method. It exhibits powder SHG efficiencies higher than that of a well known organic NLO crystal Urea. The solubility of the as grown crystals was estimated from the aqueous solution and the effect of different metal ions on the grown crystals, structural, thermal, spectral and optical properties were analyzed. XRD studies the reveals the same structure of both materials. Influence of the different central metal (Cd and Hg) atoms, changing the thermal properties of the materials when NLO complexes formed with the common ligand allylthiourea. The metal co-ordination was confirmed form the spectroscopic analysis. From the UV transmittance studies, red shift was from the transparency cut-off wavelengths. The value is 285nm for ATCC is and is 335nm ATMC, Non-linear an optical study confirms the suitabilities of the as grown crystals for the non linear optical applications. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Habit modification and improvement in properties of potassium hydrogen phthalate (KAP) crystals doped with metal ions

    S. K. Geetha
    Abstract Potassium hydrogen phthalate (KAP) single crystals were grown by slow evaporation and slow cooling techniques. The growth procedure like temperature cooling rate, evaporation rate, solution pH, concentration of the solute, supersaturation ratio etc., has been varied to have optically transparent crystals. Efforts were made to dope the KAP crystals with rubidium, sodium and lithium ions. The dopant concentration has been varied from 0.01 to 10 mole percent. Good quality single crystals were grown with different concentrations of dopants in the mother phase. Depending on the concentration of the dopants and the solution pH value, there is modification of habit. Rubidium ions very much improve the growth on the prismatic faces. The transparency of the crystals is improved with rubidium and sodium doping. The role of the dopants on the non-linear optical performance of KAP indicates better efficiency for doped crystals. The grown crystals were characterized with XRD, FT-IR, chemical etching, Vickers microhardness and SHG measurements. The influence of the dopants on the optical, chemical, structural, mechanical and other properties of the KAP crystals was analysed. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [source]

    Synthesis, structural and thermal studies of tetrathioureacopper(I) chloride crystals

    M. Dhandapani
    Abstract Tetrathioureacopper(I) chloride, hereafter abbreviated as TCC, was synthesised and single crystals were obtained from saturated aqueous solution by slow evaporation (solution growth) method at room temperature. The crystals obtained are bright, colourless and transparent having well defined external faces. The grown crystals were characterized through elemental analysis, single crystal X-ray diffraction study, thermal analysis, electron spin resonance spectroscopy and Fourier Transform infrared spectroscopy. The elemental analysis confirms the stoichiometry of the compound. The single crystal diffraction studies indicate that TCC crystallises in the tetragonal lattice and the unit cell parameters are a = b = 13.4082 Å, c = 13.8074 Å, V = 2482.29 Å3, , = , = , = 90°. Space group and the number of molecules per unit cell (Z) are found to be P41212 and 8 respectively. The TG curve of the sample shows a prolonged decomposition from 210 to 628.3 °C, from which the decomposition pattern has been formulated. The endothermic peaks in the DTA curve indicate melting and decomposition of the compound at 165.2 and 633.8 °C respectively. An exothermic peak in high temperature DSC indicates a phase transition in the compound at 274.8 °C. Thermal anomalies observed in the low temperature DSC at ,163.3, ,152.0, ,141.5, ,108.3, 1.0 and 12.1 °C in the heating run and ,157.1 and ,153.9 °C in the cooling run reveal first order phase transitions in the crystal. The peaks observed at ,146.2 °C in both the heating and cooling runs suggest occurrence of a second order phase transition in this compound. The IR spectroscopic data were used to assign the characteristic vibrational frequencies of various groups present in the compound. The ESR study confirms that the copper is in the +1 oxidation state in the complex. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Modelling rainfall interception loss in forest restoration trials in Panama

    ECOHYDROLOGY, Issue 3 2010
    Darryl E. Carlyle-Moses
    Abstract A modified Liu analytical model of rainfall interception (Ic) by tree canopies was evaluated using rainfall, throughfall and stemflow data collected from forest restoration trials in the Republic of Panama. The model uses an introduced approach to estimating the water storage capacities of tree boles, which has a more realistic physical basis than earlier iterations of the Liu model. Study species (Acacia mangium, Gliricidia sepium, Guazuma ulmifolia, Ochroma pyramidale, and Pachira quinata) were selected on the basis of differing leaf size and crown characteristics. Significant interspecific differences in both observed and simulated cumulative interception loss were found, with A. mangium intercepting more rainfall than other species. Errors between calculated and modelled cumulative Ic ranged from + 6·3% to + 30·5%, with modelled Ic always being the larger term. During-event evaporation rates from the study trees were positively related to tree height, crown area, and basal diameter. Crown area and the storage capacity of tree boles were negatively correlated. The results of a sensitivity analysis suggested that the modified model was most sensitive to variations in during-event evaporation rate. The implications of the model's sensitivity to during-event evaporation and the importance of this mechanism of interception loss are discussed, while suggestions are provided that may lead to further improvements to the analytical model. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Ecohydrology of a semi-arid forest: partitioning among water balance components and its implications for predicted precipitation changes

    ECOHYDROLOGY, Issue 2 2010
    Naama Raz Yaseef
    Abstract The distribution of precipitation inputs into different hydrological components of water-limited forest ecosystems determines water availability to trees and consequently forest productivity. We constructed a complete hydrological budget of a semi-arid pine forest (285 mm annual precipitation) by directly measuring its main components: precipitation (P), soil water content, evapotranspiration (ET, eddy covariance), tree transpiration (sap flux), soil evaporation (soil chambers), and intercepted precipitation (calculated). Our results indicated that on average for the 4-year study period, ET accounted for 94% of P, varying between 100% when P < 250 mm and 85% when P > 300 mm (with indications for losses to subsurface flow and soil moisture storage in wetter years). Direct measurements of the components of the ET flux demonstrated that both transpiration and soil evaporation were significant in this dry forest (45% and 36% of ET, respectively). Comparison between ecosystem ET (eddy covariance measurements) and the sum of its measured components showed good agreement on annual scales, but up to 30% discrepancies (in both directions) on shorter timescales. The pulsed storm pattern, characteristics of semi-arid climates, was sufficient to maintain the topsoil layer wet during the whole wet season. Only less often and intensive storms resulted in infiltration to the root zone, increasing water availability for uptake by deeper roots. Our results indicate that climate change predictions that link reduced precipitation with increased storm intensity may have a smaller effect on water availability to forest ecosystems than reduced precipitation alone, which could help forests' survival and maintain productivity even under drier conditions. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Ericaceous shrubs on abandoned block-cut peatlands: implications for soil water availability and Sphagnum restoration

    ECOHYDROLOGY, Issue 4 2009
    Kegan K Farrick
    Abstract Following harvesting by manual block-cut methods and subsequent abandonment, Cacouna bog has undergone a natural vegetation succession, with ericaceous shrubs covering more than 90% of the surface. The abundance of shrubs plays a major role in the soil water flux and availability at the site, impacting Sphagnum regeneration. From June 1 to August 22, 2007, field measurements indicate that transpiration represented the largest water loss from the shrubs at 1·7 mm day,1, comprising 142 mm (42%) of rainfall, compared to 93 mm of evaporation (28%) from bare soil. The rainfall interception from the canopy (62 mm) and litter (15 mm) accounted for 23% of seasonal rainfall. Thus after transpiration and interception losses are accounted for, only 115 mm of the 334 mm of rain (34%) remained available for other processes (recharge/soil evaporation). In the field, the litter layer prevented 17 mm from being lost over the summer as it reduced evaporation by 18%. Laboratory experiments using intact soil monoliths with and without shrubs and litter indicate that at depths below 10 cm the water content from the shrub monoliths decreased 27% versus 20% in the bare peat monoliths because of root water uptake. As a management prescription, raising the water table within 20 cm of the surface would provide water to the most active root uptake zones, reducing the need for extraction from the upper 10 cm of the peat. At this level sufficient water can be supplied to the surface through capillary rise, providing adequate water for the reestablishment/survival of Sphagnum. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Exploration of Stable Sonoelectrocatalysis for the Electrochemical Reduction of Oxygen

    ELECTROANALYSIS, Issue 12 2005
    Biljana S, ljuki
    Abstract A series of modified electrodes were prepared both via solvent evaporation and electrochemical cycling of azobenzene and derivatives and various quinones and assessed for their suitability as oxygen reduction electrocatalysts and sonoelectrocatalysts. Glassy carbon electrodes were modified via solvent evaporation with 1,2-dihydroxyanthraquinone and 1,2-diazonium-9,10-anthraquinone while edge plane and basal plane pyrolytic graphite electrodes were modified by the same procedure with 9,10-phenanthraquinone. The stability of the attached moiety was accessed in each case under ultrasound. For comparison the same electrode substrates were modified with 9,10-phenanthraquinone by electrochemical cycling and also exposed to ultrasound. The observed results suggest the use of the glassy carbon electrodes modified with azobenzene and derivatives via solvent evaporation as the optimal carbon based sonoelectrocatalysts for oxygen reduction in term of stability under insonation and high catalytic rate. [source]

    Voltametric and Flow Injection Determination of Oxytetracycline Residues in Food Samples Using Carbon Fiber Microelectrodes

    ELECTROANALYSIS, Issue 7 2003
    L. Agüí
    Abstract A voltammetric method for the determination of the antibiotic oxytetracycline (OTC) in food samples is reported. Carbon fiber microelectrodes (CFMEs), which allow voltammetric measurements to be performed in a small volume (1,mL) of the analyte extract from the samples, are employed. Repeatable electroanalytical responses were obtained with no need of applying cleaning treatments to the CFME. Under the optimized square-wave conditions, a linear calibration plot for OTC was obtained in the 1.0×10,6,1.0×10,4,mol,L,1 range, with a detection limit of 2.9×10,7,mol,L,1 (150,ng,mL,1) OTC. The determination of OTC by a flow-injection method with amperometric detection using a homemade flow cell specially designed to work with CFMEs, was also evaluated using pure acetonitrile as the carrier. The SW voltammetric method was applied to the determination of OTC in spiked milk and eggs samples, at 100,ng,mL,1 and 200,ng g,1 levels, respectively. The procedure involved the extraction of the analyte in ethyl acetate, evaporation of the solvent and reconstitution of the residue in acetonitrile ,5.0×10,4,mol,L,1 tetrabutylammonium perchlorate medium. Recoveries of 96±8 and 91±8% were obtained for milk and eggs, respectively, by applying the standard additions method. [source]

    Numerical simulation of thermal interaction between polymer and argon induction thermal plasma

    Yoshitaka Takeuchi
    Abstract Influence of polymer powder injection into Ar thermal plasmas was investigated by numerical approaches. Thermal plasma,polymer solid coupling phenomena such as melting and evaporation were considered to study plasma-quenching effect of polymer injection. Dominant process for decay of plasma temperature was examined by changing thermodynamic parameters such as melting, boiling temperatures and their latent heats of solid and liquid polymers. As a result, thermodynamic properties of evaporated polymer vapor directly affect plasma-quenching phenomena more markedly than the properties of liquid and solid which influence plasma quenching efficiency through the amount of evaporation. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(1): 24,33, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10226 [source]