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1

Electrical activity, mode of incorporation and distribution coefficient of group V elements in Hg 1?x Cd x Te grown from tellurium rich liquid phase epitxial growth solutions  

Microsoft Academic Search

Hg1?xCdxTe films were grown liquid phase epitaxially from tellurium rich solutions containing up to 10 at. % of the group V elements\\u000a P, As, Sb, and Bi. Chemical analysis of the Te growth solutions and the films was carried out in conjunction with extensive\\u000a Hall effect measurements on the films subsequent to various annealing treatments under Hg rich and Te

H. R. Vydyanath; J. A. Ellsworth; C. M. Devaney

1987-01-01

2

Catalyst Activity Maintenance for the Liquid Phase Synthesis Gas-to-Dimethyl Ether Process.  

National Technical Information Service (NTIS)

At the heart of the single-step liquid phase syngas-to-DME process (LPDME) is a catalyst system that can be active as well as stable. In the Alternative Fuels I program, a dual-catalyst system containing a Cu-based commercial methanol synthesis catalyst (...

X. D. Peng

2002-01-01

3

Kinetics of Adsorption from Liquid Phase on Activated Carbon.  

National Technical Information Service (NTIS)

The kinetics of adsorption in activated carbon are investigated and single solute kinetic parameters are used to describe (predict) multisolute kinetics. This is achieved by studying the overall rate of adsorption of several organic compounds from dilute ...

M. S. Kouyoumdjiev

1992-01-01

4

Liquid Phase Adsorption of ?-Tocopherol by Activated Carbon  

NASA Astrophysics Data System (ADS)

?-Tocopherol or commonly called vitamin E can be found in major commercial vegetable oils such as soya oil and palm oil. However the existence in these oil is in low concentration. The recovery of low concentration of ?-tocopherol from palm oils is increasingly popular. Adsorption technique for the recovery of ?-tocopherol from palm oil is believed to be much lower in cost and more effective. As a case study in this work, activated carbon is chosen as the adsorbent and ethanol as the solvent. The adsorption equilibria of ?-tocopherol onto activated carbon was conducted in batch and the concentration of ?-tocopherol was identified by LCMS. Langmuirian monolayer adsorption theory was used for the analysis of the isotherm equilibria. The adsorptivity of ?-tocopherol onto activated carbon was identified. The adsorption equilibria at low concentration found to be linear. The breakthrough curve was then generated using model assuming isothermal, single transition trace component with intraparticle diffusion. Sensitivity test on the curve indicated that the system is very sensitive to changes in diffusitivity and passive to changes on the equilibrium constant.

Bono, Awang; Ming, Chu Chi; Sundang, Murni

5

Phase-behavior and solid–liquid phase-transfer catalytic activity of tetrabutylammonium bromide  

Microsoft Academic Search

The addition of water to tetrabutylammonium bromide (TBABr)\\/benzene\\/sodium bromide ternary component systems induced the separation of TBABr-rich liquid phase (L phase) prior to the appearance of an aqueous phase (W phase). The L phase was assumed to be a bicontinuous phase similar to a microemulsion based on the phase composition. TBABr catalyzed the “solid–liquidphase-transfer reaction of decyl methanesulfonate with

Noritaka Ohtani; Tsuyoshi Yamashita; Tomoaki Ohta; Yasuhiro Hosoda

2005-01-01

6

CATALYST ACTIVITY MAINTENANCE FOR THE LIQUID PHASE SYNTHESIS GAS-TO-DIMETHYL ETHER PROCESS PART II: DEVELOPMENT OF ALUMINUM PHOSPHATE AS THE DEHYDRATION CATALYST FOR THE SINGLE-STEP LIQUID PHASE SYNGAS-TO-DME PROCESS  

Microsoft Academic Search

At the heart of the single-step liquid phase syngas-to-DME process (LPDME{trademark}) is a catalyst system that can be active as well as stable. In the Alternative Fuels I program, a dual-catalyst system containing a Cu-based commercial methanol synthesis catalyst (BASF S3-86) and a commercial dehydration material (γ-alumina) was demonstrated. It provided the productivity and selectivity expected from the LPDME process.

Xiang-Dong Peng

2002-01-01

7

Liquid-Phase Adsorption Fundamentals.  

ERIC Educational Resources Information Center

Describes an experiment developed and used in the unit operations laboratory course at the University of Wyoming. Involves the liquid-phase adsorption of an organic compound from aqueous solution on activated carbon, and is relevant to adsorption processes in general. (TW)

Cooney, David O.

1987-01-01

8

Liquid-phase adsorption of dyes and phenols using pinewood-based activated carbons  

Microsoft Academic Search

Physical properties of activated carbons prepared from pinewood at different activation times (0.5, 1.5, 2.7, and 4.0 h) in steam at 900°C were studied. The adsorption equilibria and kinetics of three dyes and three phenols (phenol, 3-chlorophenol, and o-cresol) from aqueous solutions on such carbons were then examined at 30°C. The adsorption isotherms of phenols could be well fitted by

Ru-Ling Tseng; Feng-Chin Wu; Ruey-Shin Juang

2003-01-01

9

Characterization and use of activated carbons prepared from bagasses for liquid-phase adsorption  

Microsoft Academic Search

The adsorption of two commercial dyes and phenol from water on activated carbons was investigated at 30°C. The carbons were prepared from bagasses and were activated by steam with different extents of burn-off by varying the temperature in the range of 750–840°C. Pore structures of the carbons were characterized by the t-plot method based on N2 adsorption isotherms. Three simplified

Ruey-Shin Juang; Feng-Chin Wu; Ru-Ling Tseng

2002-01-01

10

Activities and stabilities of heterogeneous catalysts in selective liquid phase oxidations: recent developments  

Microsoft Academic Search

Different strategies for the heterogenization of redox-active elements in solid matrices are reviewed. These include framework-substituted molecular sieves, amorphous mixed oxides by grafting or sol–gel methods, grafting or tethering to the inner walls of mesoporous molecular sieves, encapsulation by ship-in-a-bottle or other techniques and ion exchange in layered double hydroxides. The different approaches are illustrated by reference to recent developments

I. W. C. E. Arends; R. A. Sheldon

2001-01-01

11

Liquid-phase adsorption and desorption of phenol onto activated carbons with ultrasound  

Microsoft Academic Search

The effect of 48-kHz ultrasound on the adsorption and desorption of phenol from aqueous solutions onto coconut shell-based granular activated carbons was studied at 25°C. Experiments were performed at different carbon particle sizes (1.15, 2.5, 4.0mm), initial phenol concentrations (1.06–10.6mol\\/m3), and ultrasonic powers (46–133W). Regardless of the absence and presence of ultrasound, the adsorption isotherms were well obeyed by the

Ruey-Shin Juang; Su-Hsia Lin; Ching-Hsien Cheng

2006-01-01

12

Preparation of activated carbons from unburnt coal in bottom ash with KOH activation for liquid-phase adsorption.  

PubMed

In this work, unburnt coal (UC) in bottom ash from coal-fired power plants was soaked in KOH solution and activated for 1 h at 780 degrees C. The yield of activated carbons varied from 47.8 to 54.8% when the KOH/UC weight ratio changed from 2 to 4. Pore properties of these activated carbons including the BET surface area, pore volume, pore size distribution, and pore diameter were characterized based on N(2) adsorption isotherms. It was shown that the isotherms for the adsorption of methylene blue, acid blue 74, and 4-chlorophenol from aqueous solutions on these activated carbons at 30 degrees C were well fitted by the Langmuir equation (correlation coefficient r(2) > 0.9968). The adsorption capacities of methylene blue, acid blue 74, and 4-chlorophenol were obtained to be 2.40-2.88, 0.57-1.29, and 2.34-5.62 mmol/g, respectively. Moreover, the adsorption kinetics could be suitably described by the Elovich equation. PMID:20116919

Wu, Feng-Chin; Wu, Pin-Hsueh; Tseng, Ru-Ling; Juang, Ruey-Shin

2010-05-01

13

Microstructural evolution in the partial transient liquid phase diffusion bonding of Zircaloy4 to stainless steel 321 using active titanium filler metal  

Microsoft Academic Search

Microstructural evolution of the partial transient liquid phase diffusion bonded Zircaloy-4 and stainless steel 321 using an active Ti-base interlayer were studied at different temperatures. Additionally, simple analytical models were developed to predict the evolution of the interlayer and intermetallics during the bonding operation. Bonds were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. Precision measurement of the

M. Mazar Atabaki

2010-01-01

14

Opposite photocatalytic activity orders of low-index facets of anatase TiO2 for liquid phase dye degradation and gaseous phase CO2 photoreduction.  

PubMed

We firstly demonstrate the opposite photocatalytic activity orders of low-index facets of anatase TiO2 in the liquid phase for rhodamine B (RhB) photocatalytic degradation and in the gaseous phase for the photoreduction of CO2 to CH4. The photocatalytic activity order in the liquid phase for RhB photocatalytic degradation is revealed as {001} > {101} > {010}, whereas the photocatalytic activity order {010} > {101} > {001} is found in the gaseous phase for the photoreduction of CO2 to CH4. The atomic arrangement of the different facets, UV-vis diffuse reflectance spectra, photoluminescence spectra and attenuated total reflectance Fourier transform infrared spectroscopy analysis show that the photoactivity order in the gas phase for the photoreduction of CO2 to CH4 mainly depends on the CO2 molecule adsorption properties on the different exposed facets, and the separation efficiency of the photo-generated carriers determines the photoactivity order for the dye degradation reaction in the liquid phase. These findings also provide a new direction to design efficient photocatalysts and the tuning of their photoreactivity for environmental and energy applications. PMID:24960436

Ye, Liqun; Mao, Jin; Peng, Tianyou; Zan, Ling; Zhang, Youxiang

2014-07-01

15

CATALYST ACTIVITY MAINTENANCE FOR THE LIQUID PHASE SYNTHESIS GAS-TO-DIMETHYL ETHER PROCESS PART II: DEVELOPMENT OF ALUMINUM PHOSPHATE AS THE DEHYDRATION CATALYST FOR THE SINGLE-STEP LIQUID PHASE SYNGAS-TO-DME PROCESS  

SciTech Connect

At the heart of the single-step liquid phase syngas-to-DME process (LPDME{trademark}) is a catalyst system that can be active as well as stable. In the Alternative Fuels I program, a dual-catalyst system containing a Cu-based commercial methanol synthesis catalyst (BASF S3-86) and a commercial dehydration material ({gamma}-alumina) was demonstrated. It provided the productivity and selectivity expected from the LPDME process. However, the catalyst system deactivated too rapidly to warrant a viable commercial process [1]. The mechanistic investigation in the early part of the DOE's Alternative Fuels II program revealed that the accelerated catalyst deactivation under LPDME conditions is due to detrimental interaction between the methanol synthesis catalyst and methanol dehydration catalyst [2,3]. The interaction was attributed to migration of Cu- and/or Zn-containing species from the synthesis catalyst to the dehydration catalyst. Identification of a dehydration catalyst that did not lead to this detrimental interaction while retaining adequate dehydration activity was elusive. Twenty-nine different dehydration materials were tested, but none showed the desired performance [2]. The search came to a turning point when aluminum phosphate was tested. This amorphous material is prepared by precipitating a solution containing Al(NO{sub 3}){sub 3} and H{sub 3}PO{sub 4} with NH{sub 4}OH, followed by washing, drying and calcination. The aluminum phosphate catalyst has adequate dehydration activity and good stability. It can co-exist with the Cu-based methanol synthesis catalyst without negatively affecting the latter catalyst's stability. This report documents the details of the development of this catalyst. These include initial leads, efforts in improving activity and stability, investigation and development of the best preparation parameters and procedures, mechanistic understanding and resulting preparation guidelines, and the accomplishments of this work.

Xiang-Dong Peng

2002-05-01

16

Extremely flat surfaces by liquid phase epitaxy  

Microsoft Academic Search

By analysis of liquid phase epitaxial (LPE) growth experiments of GaAs multilayer structures, the incorporation rates at elementary growth steps (kinetic coefficients) are estimated. Conditions are presented to prepare large singular surfaces with several micrometers distances between regular elementary steps. Such quasi atomically flat surfaces may become important for applications in semiconductor and superconductor technologies, in surface physics and catalysis,

A. A. Chernov; H. J. Scheel

1995-01-01

17

Individual Activity Coefficients of Ionic Species.  

National Technical Information Service (NTIS)

Research investigations on an attempt to measure the absolute magnitude of activity coefficients of individual ionic species have been continued. In support of this objective, experimental measurements were made of the non-isothermal temperature coefficie...

G. Milazzo V. K. Sharma I. P. Reyftman

1969-01-01

18

Joining of Al 2O 3p\\/Al composites by transient liquid phase (TLP) bonding and a novel process of active-transient liquid phase (A-TLP) bonding  

Microsoft Academic Search

Transient liquid phase (TLP) bonding of Al2O3p\\/Al was performed using Cu, Al–Cu and Cu–Ti system interlayers. The reinforcement\\/metal (R\\/M) interfaces are classified into two types: primary R\\/M interfaces (as-prepared) and secondary R\\/M interfaces (after bonding). The shear strength of TLP bonded joint using Cu foil was restricted by the weakening of the secondary R\\/M interfaces, notch around faying surfaces and

Guifeng Zhang; Jianxun Zhang; Yi Pei; Siyu Li; Donglang Chai

2008-01-01

19

Microstructural evolution in the partial transient liquid phase diffusion bonding of Zircaloy-4 to stainless steel 321 using active titanium filler metal  

NASA Astrophysics Data System (ADS)

Microstructural evolution of the partial transient liquid phase diffusion bonded Zircaloy-4 and stainless steel 321 using an active Ti-base interlayer were studied at different temperatures. Additionally, simple analytical models were developed to predict the evolution of the interlayer and intermetallics during the bonding operation. Bonds were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. Precision measurement of the interlayer width was made as a function of the bonding temperature. The liquid film migration occurred as a result of chemical solubility differences between the stable and metastable phases. The formation and growth model of the intermetallic compounds at the interfaces of Zircaloy-4/Ti-base interlayer and stainless steel 321/Ti-base interlayer for controlling the bonding process was studied considering the diffusion kinetics and the thermodynamics. The evolution of the interlayer thickness indicated a good agreement between the calculation and experimental measurement. It was also demonstrated that the low isothermal solidification kinetic was not only due to the enrichment of the liquid phase with the base alloying elements such as Ti and Zr, but also the reduction of solid solubility limit of Cu in the base alloys contributed to the reduction of isothermal solidification kinetic.

Atabaki, M. Mazar

20

Liquid Phase Sintering  

NASA Technical Reports Server (NTRS)

Industry spends billions of dollars each year on machine tools to manufacture products out of metal. This includes tools for cutting every kind of metal part from engine blocks to Shuttle main engine components. Cutting tool tips often break because of weak spots or defects in their composition. Based on a new concept called defect trapping, space offers a novel environment to study defect formation in molten metal materials as they solidify. After the return of these materials from space, researchers can evaluate the source of the defect and seek ways to eliminate them in products prepared on Earth. A widely used process for cutting tip manufacturing is liquid phase sintering. Compared to Earth-sintered samples which slump due to buoyancy induced by gravity, space samples are uniformly shaped and defects remain where they are formed. By studying metals sintered in space the US tool industry can potentially enhance its worldwide competitiveness. The Consortium for Materials Development in Space along with Wyle Labs, Teledyne Advanced Materials, and McDornell Douglas have conducted experiments in space.

2004-01-01

21

Optimization of activity coefficient models to describe vapor-liquid equilibrium of (alcohol + water) mixtures using a particle swarm algorithm  

Microsoft Academic Search

A method to model the vapor–liquid phase based on a particle swarm algorithm is developed in this study. Two activity coefficient models (UNIQUAC and NRTL) were optimized with particle swarm optimization (PSO), and used to describe the isobaric vapor–liquid equilibrium of fifteen binary mixtures containing alcohol + water. The results were compared with the Levenberg–Marquardt algorithm, and show that the PSO algorithm

Juan A. Lazzús

2010-01-01

22

Characterization and use of high surface area activated carbons prepared from cane pith for liquid-phase adsorption.  

PubMed

Carbonaceous adsorbents with controllable surface areas were chemically activated with KOH at 780 degrees C from char that had been carbonized from cane pith at 450 degrees C. The pore properties including the BET surface area, pore volume, pore size distribution, and mean pore diameter of these activated carbons were characterized and derived using the t-plot method based on N(2) adsorption isotherms. The activated cane pith carbons, with KOH/char ratios of 2-6, exhibited BET surface areas ranging from 912 to 2299 m(2) g(-1). The scanning electron microscopic (SEM) observations revealed that the surface morphology of honeycombed holes on all activated cane pith carbons was significantly influenced by the KOH/char ratio. The adsorption kinetics and equilibrium isotherms of acid blue 74, methylene blue, basic brown 1, p-nitrophenol, p-chlorophenol, p-cresol, and phenol from water at 30 degrees C on the activated carbons were studied. The adsorption kinetics were suitably described by a simplified kinetic model, the Elovich equation. All adsorption equilibrium isotherms were in agreement with the Langmuir equation, and were used to compare the covered area (S(c)/S(p)) of the activated carbons at different KOH/char ratios. The high-surface-area activated carbons were proven to be promising adsorbents for pollution control and for other applications. PMID:16488539

Tseng, Ru-Ling; Tseng, Szu-Kung

2006-08-25

23

Disease characterization of active appearance model coefficients  

NASA Astrophysics Data System (ADS)

We previously reported on 2D and 3D Active Appearance Models (AAM) for automated segmentation of cardiac MR. AAMs are shown useful for such segmentations because they exploit prior knowledge about cardiac shape and image appearance, yet segmentation of object borders might not be the only benefit of AAMs. An AAM represents objects as a linear combination of shape and texture variations applied to a mean object via Principal Component Analysis (PCA) to form an integrated model. This model captures enough shape, texture, and motion variations to accurately synthesize reconstructions of target objects from a finite set of parameters. Because of this, we hypothesize that AAM coefficients may be used for the classification of disease abnormalities. PCA is useful for reducing the dimensionality of vectors, however it does not produce vectors optimal for the separation of classes needed for disease classification. Discriminate analysis such as Linear Discriminate Analysis (LDA) and Kernel Discriminate Analysis (KDA) are dimension reducing techniques with the added benefit of supervised learning for the purpose of classification. Once AAM segmentation is complete, disease probabilities are computed from model coefficients via discriminate analysis. Preliminary results on model coefficients show tendency of disease separation for certain disease classes.

Mitchell, Steven C.; Lelieveldt, Boudewijn P. F.; Bosch, H. G.; Reiber, Johan H. C.; Sonka, Milan

2003-05-01

24

A thermodynamic model of mixed organic-inorganic aerosols to predict activity coefficients  

NASA Astrophysics Data System (ADS)

Tropospheric aerosols contain mixtures of inorganic salts, acids, water, and a large variety of organic compounds. Interactions between these substances in liquid mixtures lead to discrepancies from ideal thermodynamic behaviour. By means of activity coefficients, non-ideal behaviour can be taken into account. We present here a thermodynamic model named AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) that is able to calculate activity coefficients covering inorganic, organic, and organic-inorganic interactions in aqueous solutions over a wide concentration range. This model is based on the activity coefficient model LIFAC by Yan et al. (1999) that we modified and reparametrised to better describe atmospherically relevant conditions and mixture compositions. Focusing on atmospheric applications we considered H+, Li+, Na+, K+, NH+4, Mg2+, Ca2+, Cl-, Br-, NO-3, HSO-4, and SO2-4 as cations and anions and a wide range of alcohols/polyols composed of the functional groups CHn and OH as organic compounds. With AIOMFAC, the activities of the components within an aqueous electrolyte solution are well represented up to high ionic strength. Most notably, a semi-empirical middle-range parametrisation of direct organic-inorganic interactions in alcohol+water+salt solutions strongly improves the agreement between experimental and modelled activity coefficients. At room temperature, this novel thermodynamic model offers the possibility to compute equilibrium relative humidities, gas/particle partitioning and liquid-liquid phase separations with high accuracy. In further studies, other organic functional groups will be introduced. The model framework is not restricted to specific ions or organic compounds and is therefore also applicable for other research topics.

Zuend, A.; Marcolli, C.; Luo, B. P.; Peter, T.

2008-08-01

25

A thermodynamic model of mixed organic-inorganic aerosols to predict activity coefficients  

NASA Astrophysics Data System (ADS)

Tropospheric aerosols contain mixtures of inorganic salts, acids, water, and a large variety of organic compounds. Interactions between these substances in liquid mixtures lead to discrepancies from ideal thermodynamic behaviour. By means of activity coefficients, non-ideal behaviour can be taken into account. We present here a thermodynamic model named AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) that is able to calculate activity coefficients covering inorganic, organic, and organic-inorganic interactions in aqueous solutions over a wide concentration range. This model is based on the activity coefficient model LIFAC by Yan et al. (1999) that we modified and reparametrised to better describe atmospherically relevant conditions and mixture compositions. Focusing on atmospheric applications we considered H+, Li+, Na+, K+, NH4+, Mg2+, Ca2+, Cl-, Br-, NO3-, HSO4-, and SO42- as cations and anions and a wide range of alcohols/polyols composed of the functional groups CHn and OH as organic compounds. With AIOMFAC, the activities of the components within an aqueous electrolyte solution are well represented up to high ionic strength. Most notably, a semi-empirical middle-range parametrisation of direct organic-inorganic interactions in alcohol + water + salt solutions strongly improves the agreement between experimental and modelled activity coefficients. At room temperature, this novel thermodynamic model offers the possibility to compute equilibrium relative humidities, gas/particle partitioning and liquid-liquid phase separations with high accuracy. In further studies, other organic functional groups will be introduced. The model framework is not restricted to specific ions or organic compounds and is therefore also applicable for other research topics.

Zuend, A.; Marcolli, C.; Luo, B. P.; Peter, Th.

2008-03-01

26

Individual Activity Coefficients of Ionic Species.  

National Technical Information Service (NTIS)

The theoretical considerations which apply in particular for the temperature coefficient of the electric tension of the Pt-H2/H(+) electrode including those concerning the correction terms for the pressure of the hydrogen gas are first discussed, followed...

G. Milazzo I. P. Reyftman V. K. Sharma

1970-01-01

27

Thermal expansion of glasses in the solid and liquid phases  

SciTech Connect

The thermal expansion of a number of mixed oxide glasses was measured in the solid and liquid regions by gamma densitometry. Lead borate glasses were examined in the range 27 to 42 mol % PbO. The liquid phase volumetric thermal expansion coefficient was observed to decrease with increasing PbO content, in contrast to the solid phase linear thermal expansion coefficients, which displayed some increase with increasing PbO composition. At 33.3 and 42 mol % PbO, these glasses displayed crystallization behavior during cooling from the melt, depending on the cooling rate. In soda-baria phosphate glasses (50 mol % P/sub 2/O/sub 5/), liquid phase volumetric expansion coefficients were found to vary as the solid phase linear expansion coefficients. For those phosphates with Na/sub 2/O, crystallization was observed on cooling from the melt. Measurements on a lithia-aluminosilicate glass ceramic were obtained by this method to approximately 400 C above the limit of conventional dilatometry, thereby allowing the measurement of the thermal expansion of high temperature crystalline phases, as well as the liquid phase density. The gamma densitometry technique can yield density, thermal expansion, T/sub g/ and crystallization information, and quenching rate dependence data on glasses to temperatures in excess of 1500/sup 0/C, and thus provides a means for high temperature characterization of glasses which complements conventional dilatometry, calorimetry, and thermal analysis.

Drotning, W.D.

1985-01-01

28

Liquid phase chromatography on microchips.  

PubMed

Over the past twenty years, the field of microfluidics has emerged providing one of the main enabling technologies to realize miniaturized chemical analysis systems, often referred to as micro-Total Analysis Systems (uTAS), or, more generally, Lab-on-a-Chip Systems (LOC) [1,2]. While microfluidics was driven forward a lot from the engineering side, especially with respect to ink jet and dispensing technology, the initial push and interest from the analytical chemistry community was through the desire to develop miniaturized sensors, detectors, and, very early on, separation systems. The initial almost explosive development of, in particular, chromatographic separation systems on microchips, has, however, slowed down in recent years. This review takes a closer, critical look at how liquid phase chromatography has been implemented in miniaturized formats over the past several years, what is important to keep in mind when developing or working with separations in a miniaturized format, and what challenges and pitfalls remain. PMID:22071425

Kutter, Jörg P

2012-01-20

29

Formation, structure, and evolution of boiling nucleus and interfacial tension between bulk liquid phase and nucleus  

Microsoft Academic Search

In this paper, the concept of the molecular free path is introduced to derive a criterion distinguishing active molecules from inactive molecules in liquid phase. A concept of the critical aggregation concentration (CAC) of active molecules is proposed to describe the physical configuration before the formation of a nucleus during vapor–liquid phase transition. All active molecules exist as monomers when

Xiao-Dong Wang; Xiao-Feng Peng; Yong Tian; Bu-Xuan Wang

2005-01-01

30

COMPARISON OF THE OCTANOL-AIR PARTITION COEFFICIENT AND LIQUID-PHASE VAPOR PRESSURE AS DESCRIPTORS FOR PARTICLE/GAS PARTITIONING USING LABORATORY AND FIELD DATA FOR PCBS AND PCNS  

EPA Science Inventory

The conventional Junge-Pankow adsorption model uses the sub-cooled liquid vapor pressure (pLo) as a correlation parameter for gas/particle interactions. An alternative is the octanol-air partition coefficient (Koa) absorption model. Log-log plots of the particle-gas partition c...

31

Transient liquid phase ceramic bonding  

DOEpatents

Ceramics are joined to themselves or to metals using a transient liquid phase method employing three layers, one of which is a refractory metal, ceramic or alloy. The refractory layer is placed between two metal layers, each of which has a lower melting point than the refractory layer. The three layers are pressed between the two articles to be bonded to form an assembly. The assembly is heated to a bonding temperature at which the refractory layer remains solid, but the two metal layers melt to form a liquid. The refractory layer reacts with the surrounding liquid and a single solid bonding layer is eventually formed. The layers may be designed to react completely with each other and form refractory intermetallic bonding layers. Impurities incorporated into the refractory metal may react with the metal layers to form refractory compounds. Another method for joining ceramic articles employs a ceramic interlayer sandwiched between two metal layers. In alternative embodiments, the metal layers may include sublayers. A method is also provided for joining two ceramic articles using a single interlayer. An alternate bonding method provides a refractory-metal oxide interlayer placed adjacent to a strong oxide former. Aluminum or aluminum alloys are joined together using metal interlayers.

Glaeser, Andreas M. (Berkeley, CA)

1994-01-01

32

Infinite dilution activity coefficients in chemical, environmental and biochemical engineering  

Microsoft Academic Search

Here we briefly review several methods by which infinite dilution activity coefficients can be obtained, and then consider how such data can be used. In particular, we examine the accuracy of predictions of vapor-liquid equilibria over the complete concentration range, and over a range of temperatures based on infinite dilution activity coefficient data at a single temperature. Next, we review

S. I. Sandler

1996-01-01

33

Catalytic liquid-phase nitrite reduction: Kinetics and catalyst deactivation  

Microsoft Academic Search

Liquid-phase reduction using a solid catalyst provides a potential technique for the removal of nitrites from waters. Activity and selectivity measurements were performed for a wide range of reactant concentrations and reaction conditions in an isothermal semi-batch slurry reactor, which was operated at temperatures below 298 K and atmospheric pressure. The effects of catalyst loading and initial nitrite concentration on

Albin Pintar; G. Bercic; Janez Levec

1998-01-01

34

Liquid phase sintering in microgravity  

NASA Astrophysics Data System (ADS)

Liquid Phase Sintering (LPS) experiments have been conducted on four suborbital rockets, six Space Shuttle missions and two missions to the Mir Space Station by our research group. These missions began in 1989, spanning over 10 years. This paper will overview the many separate and interesting research and technical challenges faced in these missions and review the many published models developed to date by our group. The principle finding is that microgravity materials made using typical liquid phase sintering approaches are inferior to those made on earth. This results from pressing the green, presintered compact from their constituent powders, Fe and Co base materials with a Cu additive phase, producing composites that have solid volume fractions of 70-80%, with the balance either vacuum filled pores or entrapped gas. During LPS, the compact is processed above the melting point of the additive phase, producing a three-phase system. On earth, the entrapped gas is rapidly eliminated, and particle rearrangement is principally by buoyancy driven convection. In microgravity, this is not the case. In microgravity systems, all three phases exist concurrently, and the gas phase is not eliminated by buoyancy driven convection. Instead, the gas phase alters the free energy of the composite producing a variety of transport processes not typically seen in the earth based experiments, a positive result. Microgravity experiments slow down the typically fast acting rearrangement phase, permitting detailed study of the rapid processes taking place on earth in the first few seconds to minutes of LPS. Results from space processing have lead to a reconsideration of unit gravity models during the rearrangement stage. It has lead to a new model to explain the initiation of pore metamorphosis in LPS sample processed in microgravity, where pore breakup, coalescence and filling were found. Diffusion controlled grain growth in mutually soluble alloy phase systems, such as Co-Cu, was observed for the first time and a shrinking core model developed that successfully modeled this aspect of grain growth. In the absence of gravity, the grain coarsening model should follow the Lifshitz-Slyozov and Wagner (LSW) theory. Our extensive analysis of over 200 samples has shown that, contrary to expectation, there was an enhancement in particle coarsening with a decrease in the volume fraction of solid. The agglomerated microstructures exhibited a higher grain growth constant consistent with their higher 3D coordination number. Though buoyancy driven convection is eliminated, Brownian motion is not and becomes dominate in microgravity. This driving force leads to agglomeration and the need to use the Lifshitz-Slyozov Encounter Modified (LSEM) model to correctly model the results. Many papers on these phenomena h ve appeared in the literature and will be summarized anda presented along with a discussion of systems and subsystems needed to successfully conduct high temperature microgravity research on the fundamental mechanisms associated with LPS.

Smith, J.; Lundquist, C.; Riley, M.; Robinson, R.

35

Liquid-Phase Oxidations of Cyclic Alkenes.  

National Technical Information Service (NTIS)

The work was undertaken to relate the initial products of liquid-phase oxidations of unsaturated hydrocarbons under mild conditions (and thus their mechanisms of oxidation) to the structures of the hydrocarbons. Results with cyclopentene, cyclohexene, cyc...

D. E. Van Sickle F. R. Mayo R. M. Arluck

1965-01-01

36

Solid-liquid phase transition in argon  

NASA Technical Reports Server (NTRS)

Starting from the Lennard-Jones interatomic potential, a modified cell theory has been used to describe the solid-liquid phase transition in argon. The cell-size variations may be evaluated by a self-consistent condition. With the inclusion of cell-size variations, the transition temperature, the solid and liquid densities, and the liquid-phase radial-distribution functions have been calculated. These ab initio results are in satisfactory agreement with molecular-dynamics calculations as well as experimental data on argon.

Tsang, T.; Tang, H. T.

1978-01-01

37

Anomalous behavior of the diffusion coefficient in thin active films  

NASA Astrophysics Data System (ADS)

Inspired by recent experiments in cell biology, we elucidate the visco-elastic properties of an active gel by studying the dynamics of a small tracer particle inside it. In a stochastic hydrodynamic approach for an active gel of finite thickness L, we calculate the mean square displacement of a particle. These particle displacements are governed by fluctuations in the velocity field. We characterize the short-time behavior when the gel is a solid as well as the limit of long times when the gel becomes a fluid and the particle shows simple diffusion. Active stresses together with local polar order give rise to velocity fluctuations that lead to characteristic behaviors of the diffusion coefficient that differ fundamentally from those found in a passive system: the diffusion coefficient can depend on system size and diverges as L approaches an instability threshold. Furthermore, the diffusion coefficient becomes independent of the particle size in this case.

Basu, Abhik; Joanny, Jean-Francois; Jülicher, Frank; Prost, Jacques

2012-11-01

38

Improved Boat For Liquid-Phase Epitaxy  

NASA Technical Reports Server (NTRS)

Liquid-phase epitaxial (LPE) growth boat redesigned. Still fabricated from ultra-high-purity graphite, but modified to permit easy disassembly and cleaning, along with improved wiping action for more complete removal of melt to reduce carry-over of gallium. Larger substrates and more uniform composition obtained.

Connolly, John C.

1991-01-01

39

Liquid phase effects on benzene UV spectra  

NASA Astrophysics Data System (ADS)

Some results for the benzene molecular properties in liquid phase are shown, stressing the interest on the electronic spectra properties. The way we follow to perform calculations is a Semi-classical one. taking into account the structural information of the benzene pure liquid and the electronic structure of the benzene molecule at the CNDO level.

Se?e, L. M.; Botella, V.; Gómez, P. C.; Fernández, M.

1986-03-01

40

Vapor-liquid phase separator permeability results  

NASA Technical Reports Server (NTRS)

Continued studies are described in the area of vapor-liquid phase separator work with emphasis on permeabilities of porous sintered plugs (stainless steel, nominal pore size 2 micrometer). The temperature dependence of the permeability has been evaluated in classical fluid using He-4 gas at atmospheric pressure and in He-2 on the basis of a modified, thermosmotic permeability of the normal fluid.

Yuan, S. W. K.; Frederking, T. H. K.

1981-01-01

41

A Liquid-Phase Diffusion Experiment.  

ERIC Educational Resources Information Center

Describes an experiment that measures the diffusion of ions in the liquid phase and shows that the relative distances of diffusion are related qualitatively to the inverse of the mass of the solvated ion. Involves soluble salts on opposite sides of a Petri dish diffusing through a layer of water and meeting to form an insoluble salt. (JRH)

Nemetz, Thomas M.; Ball, David W.

1995-01-01

42

Liquid phase sintered compacts in space  

NASA Technical Reports Server (NTRS)

A model that will explain the effect of gravity on liquid phase sintering was developed. Wetting characteristics and density segregation which are the two important phenomena in liquid phase sintering are considered in the model development. Experiments were conducted on some selected material combinations to study the gravity effects on liquid phase sintering, and to verify the validity of the model. It is concluded that: (1) The surface tension forces acting on solid particles in a one-g environment are not appreciably different from those anticipated in a 0.00001g/g sub 0 (or lower) environment. (2) The capillary forces are dependent on the contact angle, the quantity of the liquid phase, and the distance between solid particles. (3) The pores (i.e., bubbles) do not appear to be driven to the surface by gravity-produced buoyancy forces. (4) The length of time to produce the same degree of settling in a low-gravity environment will be increased significantly. (5) A low gravity environment would appear to offer a unique means of satisfactorily infiltrating a larger and/or complex shaped compact.

Mookherji, T. K.; Mcanelly, W. B.

1974-01-01

43

Catalytic features of a low-temperature reduced alumina-supported platinum catalyst. Activity and selectivity in the liquid-phase hydrogenation of benzaldehyde and nitrobenzene  

Microsoft Academic Search

A low-temperature reduced (LR) supported platinum catalyst was used for the hydrogenation of benzaldehyde, nitrobenzene and\\u000a their mixture in ethanol, and compared with a high-temperature reduced (HR) catalyst. For benzaldehyde the LR catalyst was\\u000a highly active to the formation of benzyl alcohol and did not give benzaldehyde diethyl acetal, which was largely formed by\\u000a the HR catalyst. For the mixture,

M. Arai; A. Obata; Y. Nishiyama

1997-01-01

44

Liquid phase microextraction applications in food analysis  

Microsoft Academic Search

Over the last years, liquid-phase microextraction (LPME) in its different application modes (single drop microextraction, dispersive liquid–liquid microextraction and hollow fiber-LPME) has been increasingly applied for the extraction of both inorganic and organic analytes from different matrices. Its advantages over conventional extraction procedures (simplicity, effectiveness, rapidity and low consumption of organic solvents) has also attracted its application in the complex

María Asensio-Ramos; Lidia M. Ravelo-Pérez; Miguel Ángel González-Curbelo; Javier Hernández-Borges

2011-01-01

45

Developments in liquid-phase microextraction  

Microsoft Academic Search

The development of faster, simpler, inexpensive and more environmentally friendly sample-preparation techniques is an important issue in chemical analysis. Recent research trends involve miniaturisation of the traditional liquid-liquid extraction (LLE) principle by greatly reducing the acceptor-to-donor phase ratio. One of the emerging techniques in this area is liquid-phase microextraction (LPME), where a hollow fibre impregnated with an organic solvent is

E. Psillakis; N. Kalogerakis

2003-01-01

46

Liquid-phase sintering of PZT ceramics  

Microsoft Academic Search

Lead zirconate titanate (abbreviated as PZT) ceramics are of considerable commercial importance for a host of piezoelectric and pyroelectric applications. Conventionally, many PZT ceramics are sintered at temperatures above 1250°C. Such extreme temperatures are undesirable due to the increased energy consumption, limitation of electrode material and evaporation of volatile components. A liquid-phase sintering aid incorporating Cu2O and PbO is presented

D. L Corker; R. W Whatmore; E Ringgaard; W. W Wolny

2000-01-01

47

Model for the prediction of liquid phase mass transfer of random packed columns for gas–liquid systems  

Microsoft Academic Search

The following work presents a new, generally applicable model for description of the mass transfer in the liquid phase for packed columns filled with random dumped non-perforated and lattice-type packing with size between 12 and 90mm for gas–liquid systems in operating range up to flooding point.The new equation for evaluation of the volumetric mass transfer coefficient in the liquid phase

Jerzy Ma?kowiak

2011-01-01

48

Infinite dilution activity coefficients from ab initio solvation calculations  

SciTech Connect

A Group Contribution Solvation (GCS) model was developed to calculate infinite dilution activity coefficients ({gamma}{sup {chi}}) based on modern computational chemistry. The GCS model results in an average error of 7% in {gamma}{sup {chi}} for the limited number of data points among water, n-hexane, acetonitrile and n-octanol, whereas the errors are 47% and 52% with the UNIFAC model and the modified UNIFAC model, respectively. GCS was also used to calculate infinite dilution partition coefficients, which can be used to determine how a dilute solute partitions between two solvents. Solutes were examined in three different liquid-liquid systems: water/n-hexane, water/acetonitrile, and water/n-octanol. With GCS, the average errors are 22% (for 18 solutes), 18% (for 14 solutes) and 14% (for 15 solutes) for these solvent systems, while comparable errors are 237%, 286% and 226% with UNIFAC; and 342%, 414% and 306% with modified UNIFAC. The GCS model is a powerful new tool to predict the octanol-water partition coefficients.

Lin, S.T.; Sandler, S.I.

1999-12-01

49

TheLiquidPhase: Countercurrent Chromatography  

NSDL National Science Digital Library

TheLiquidPhase is a community portal, or wiki, dedicated to the proliferation of knowledge and good technique in countercurrent chromatography (CCC). It has been organized to help prospective users of CCC learn about its potential and to provide a virtual meeting place for discussions among experienced users of the technique. There are pages explaining CCC, how to get started, and describing a typical setup; sections devoted to solvent systems, modes of operation, and CCC chromatograms; an undergraduate chemistry lab experiment using CCC; lists of manufacturers and distributors; a bibliography, and an alphabetical index.

50

Ethers from ethanol. 4: Kinetics of the liquid-phase synthesis of two tert-hexyl ethyl ethers  

SciTech Connect

Tertiary ethers produced from reactive C{sub 5} and C{sub 6} olefins and ethanol or methanol are being investigated as oxygenate gasoline additives in addition to isobutylene-derived methyl tert-butyl ether and ethyl tert-butyl ether. The kinetics of liquid-phase etherification and accompanying isomerization of four reactive C{sub 6} olefin isomers with ethanol catalyzed by the ion-exchange resin catalyst Amberlyst 15 were determined at temperatures from 313 to 353 K and a pressure of 0.69 MPa in a differential packed-bed reactor. Rate expressions in terms of species activities, with the activity coefficients determined by the UNIFAC method, were developed to correlate the experimental data over a wide range of compositions. The rate expressions are based on the Langmuir-Hinshelwood-Hougen-Watson formalism involving a dual-site surface etherification reaction and a single-site surface isomerization reaction as the rate-limiting steps, along with the assumption of ethanol as the most abundant surface species. The negligibility of olefins and ether adsorption terms, but the nonnegligibility of vacant sites, was confirmed by independent liquid-phase adsorption experiments. The developed rate expressions were finally tested in an integral reactor and found to be accurate.

Zhang, T.; Datta, R. [Univ. of Iowa, Iowa City, IA (United States). Dept. of Chemical and Biochemical Engineering

1995-07-01

51

Liquid-liquid phase transition in water  

NASA Astrophysics Data System (ADS)

Water shows anomalies different from most of other materials. Different sceniaros have been proposed to explain water anomalies, among which the liquid-liquid phase transition (LLPT) is the most discussed one. It attributes water anomalies to the existence of a hypothesized liquid-liquid critical point (LLCP) buried deep in the supercooled region. We briefly review the recent experimental and theoretical progresses on the study of the LLPT in water. These studies include the discussion on the existence of the first order LLPT in supercooled water and the detection of liquid-liquid critical point. Simulational results of different water models for LLPT and the experimental evidence in confined water are also discussed.

Sun, ZhaoRu; Sun, Gang; Chen, YiXuan; Xu, LiMei

2014-05-01

52

Vapor-liquid activity coefficients for methanol and ethanol from heat of solution data: application to steam-methane reforming.  

PubMed

This paper presents equations and curves to calculate vapor-liquid phase equilibria for methanol and ethanol in dilute aqueous solution as a function of temperature, using activity coefficients at infinite dilution. These thermodynamic functions were originally derived to assess the distribution of by-product contaminants in the process condensate and the steam-system deaerator of a hydrogen plant [Paper ENV-00-171 presented at the NPRA 2000 Environmental Conference, San Antonio, TX, 10-12 September 2000], but have general applicability to other systems as well. The functions and calculation method described here are a necessary piece of an overall prediction technique to estimate atmospheric emissions from the deaerator-vent when the process condensate is recycled as boiler feed water (BFW) make-up. Having such an estimation technique is of particular significance at this time because deaerator-vent emissions are already coming under regulatory scrutiny in California [Emissions from Hydrogen Plant Process Vents, Adopted 21 January 2000] followed closely elsewhere in the US, and eventually worldwide. The overall technique will enable a permit applicant to estimate environmental emissions to comply with upcoming regulations, and a regulatory agency to evaluate those estimates. It may also be useful to process engineers as a tool to estimate contaminant concentrations and flow rates in internal process streams such as the steam-generating system. Metallurgists and corrosion engineers might be able to use the results for materials selection. PMID:11606240

Kunz, R G; Baade, W F

2001-11-16

53

Liquid-phase sintering of molybdenum-copper pseudoalloys  

Microsoft Academic Search

pseudoalloys by the liquid-phase sintering method and also of other systems with very low solubility of the solid in liquid phase. The effect of the amount of the low-melting phase on the characteristics of the shrinkage process as a result of regrouping of the powder particles in liquid-phase sintering have been studied most comprehensively in [2-5] where main attention was

V. Ya. Petrishchev; M. M. Churakov; L. I. Kostenetskaya

1988-01-01

54

Liquid phase methanol and dimethyl ether synthesis from syngas  

Microsoft Academic Search

The Liquid Phase Methanol Synthesis (LPMeOHTM) process has been investigated in our laboratories since 1982The reaction chemistry of liquid phase methanol synthesis over commercial Cu\\/ZnO\\/Al2O3 catalysts, established for diverse feed gas conditions including H2-rich, CO-rich, CO2-rich, and CO-free environments, is predominantly based on the CO2 hydrogenation reaction and the forward water-gas shift reactionImportant aspects of the liquid phase methanol synthesis

Sunggyu Lee; Abhay Sardesai

2005-01-01

55

Temperature Coefficient of Electrode Electric Tension and Activity Coefficients of Individual Ionic Species.  

National Technical Information Service (NTIS)

The electrodes Pt-H2/H(+)Br(-) and Ag/AgBr/Br(-)K(+) were investigated for the true temperature coefficient of their electric tension. The measurement at 25C and 35C were extended over the concentration range from about 0.1m down to about 0.001. The poten...

A. Marconi B. Struck C. Palma G. Milazzo M. E. Weill

1972-01-01

56

Transient liquid-phase bonding in two-phase ternary systems  

Microsoft Academic Search

The process of isothermal solidification during transient liquid-phase (TLP) bonding in a ternary system is analyzed. In the\\u000a most usual situation, and in contrast to the binary case, the composition of the liquid is required to change continuously\\u000a as solidification proceeds. If the solubilities and\\/or diffusion coefficients of the two solutes are very different, the solidification\\u000a stage is clearly divided

C. W. Sinclair; G. R. Purdy; J. E. Morral

2000-01-01

57

Research on Transient Liquid Phase Diffusion Bonding of Steel Sandwich Panels Under Small Plastic Deformation  

Microsoft Academic Search

Plastic deformation was newly introduced in transient liquid phase (TLP) diffusion bonding of steel sandwich panels. The effect\\u000a of plastic deformation on bonding strength was investigated through lab experiments. It was assumed that three factors, including\\u000a newly generated metal surface area, deformation heat, and lattice distortion, contribute to the acceleration of interface\\u000a atoms diffusion and increase of diffusion coefficients. A

H. Li; Z. X. Li

2008-01-01

58

Liquid phase methanol LaPorte PDU: Modification, operation, and support studies  

SciTech Connect

Operation of a methanol synthesis reactor in the liquid phase requires an efficient catalyst poison removal system. A number of commercially available adsorbents were screened for their ability to remove the following methanol catalyst poisons: Fe(CO){sub 5}, Ni(CO){sub 4}, COS, H{sub 2}S, and HCl. Adsorption isotherms were measured at various carrier gas pressures and two temperatures on several adsorbents, including active carbons, zeolites, alumina, silica gel, metal oxide impregnated active carbons, metal oxide promoted zinc oxide, metal oxide promoted alumina, and spent methanol catalyst. By monitoring the approach to equilibrium as a function of time, mass transfer coefficients for the adsorption of these trace impurities were also determined. From this adsorbent screening, the preferred adsorbent for removal of each catalyst poison was identified. The equilibrium and kinetic adsorptive properties for each poison/adsorbent system were used to design a poison removal scheme. This design will be tested in a pilot unit using coal gas from a commercial gasifier. 5 refs., 30 figs., 3 tabs.

Not Available

1990-09-28

59

Partial transient liquid phase diffusion bonding of Zircaloy4 to stabilized austenitic stainless steel 321  

Microsoft Academic Search

An innovative method was applied for bonding Zircaloy-4 to stabilized austenitic stainless steel 321 using an active titanium interlayer. Specimens were joined by a partial transient liquid phase diffusion bonding method in a vacuum furnace at different temperatures under 1MPa dynamic pressure of contact. The influence of different bonding temperatures on the microstructure, microindentation hardness, joint strength and interlayer thickness

M. Mazar Atabaki; A. Talebi Hanzaei

2010-01-01

60

Liquid phase methanol LaPorte process development unit: Modification, operation, and support studies  

SciTech Connect

This report consists of Detailed Data Acquisition Sheets for Runs E-6 and E-7 for Task 2.2 of the Modification, Operation, and Support Studies of the Liquid Phase Methanol Laporte Process Development Unit. (Task 2.2: Alternate Catalyst Run E-6 and Catalyst Activity Maintenance Run E-7).

Not Available

1991-02-02

61

Thermal transport behavior of van der Waals solids and liquids in the neighborhood of the solid-liquid phase transition  

Microsoft Academic Search

The thermal conductivity, ?, is one of the few transport coefficients which shows a relatively small change at the solid-liquid phase transition, and hence it is a property that can be used in comparing dynamic properties of both ordered and disordered systems. Although the discontinuity in ? can be accounted for largely by the difference in density, ?, of solid

J. J. Van Loef; H. J. M. Hauley; A. Cezairliyan

1986-01-01

62

Ferrofluid-based liquid-phase microextraction.  

PubMed

A new mode of liquid-phase microextraction based on a ferrofluid has been developed. The ferrofluid was composed of silica-coated magnetic particles and 1-octanol as the extractant solvent. The 1-octanol was firmly confined within the silica-coated particles, preventing it from being lost during extraction. Sixteen polycyclic aromatic hydrocarbons (PAHs) were used as model compounds in the development and evaluation of the extraction procedure in combination with gas chromatography-mass spectrometry. Parameters affecting the extraction efficiency were investigated in detail. The optimal conditions were as follows: 20mL sample volume, 10mg of the silica-coated magnetic particles (28mg of ferrofluid), agitation at 20Hz, 20min extraction time, and 2min by sonication with 100?L acetonitrile as the final extraction solvent. Under optimal extraction conditions, enrichment factors ranging from 102- to 173-fold were obtained for the analytes. The limits of detection and the limits of quantification were in the range of 16.8 and 56.7pgmL(-1) and 0.06 and 0.19ngmL(-1), respectively. The linearities were between 0.5-100 and 1-100ngmL(-1) for different PAHs. As the ferrofluid can respond to and be attracted by a magnet, the extraction can be easily achieved by reciprocating movement of an external magnet that served to agitate the sample. No other devices were needed in this new approach of extraction. This new technique is affordable, efficient and convenient for microextraction, and offers portability for potential onsite extraction. PMID:20961552

Shi, Zhi-Guo; Zhang, Yufeng; Lee, Hian Kee

2010-11-19

63

Mixed Stationary Liquid Phases for Gas-Liquid Chromatography.  

ERIC Educational Resources Information Center

Describes a laboratory technique for use in an undergraduate instrumental analysis course that, using the interpretation of window diagrams, prepares a mixed liquid phase column for gas-liquid chromatography. A detailed procedure is provided. (BT)

Koury, Albert M.; Parcher, Jon F.

1979-01-01

64

Group contributions to activity coefficients from the hard sphere expansion corresponding states theory  

Microsoft Academic Search

A new method has been developed for predicting liquid activity coefficients in ternary mixtures from group contributions. In this method, activity coefficients are obtained from the excess Gibbs free energy of mixing at constant temperature and pressure. In calculating this excess function, the constituent and mixture Gibbs free energies are each represented by an expansion about a pure reference fluid

D. E. R. Quock; T. W. Leland

1986-01-01

65

Analysis of infinite dilution activity coefficients of solutes in hydrocarbons from UNIFAC  

Microsoft Academic Search

Molecular structural effects on infinite dilution activity coefficients of solutes in n-alkanes and other hydrocarbons are studied within the UNIFAC model. Characteristic chain-length dependencies and other structural relationships imbedded in the model are discussed with emphasis to the consequences this has for model development. The cases treated have subtle but major implications for the correlation of activity coefficients and derivatives

J Abildskov; R Gani; P Rasmussen; J. P O’Connell

2001-01-01

66

Representation of activity coefficients of fundamental biochemicals in water by the UNIFAC model  

Microsoft Academic Search

The assignment of UNIFAC parameters has been newly examined to represent the activity coefficients of fundamental biochemicals in aqueous solutions containing sugars, imino acids, urea, amino acid salts, inorganic salts, and sugar salts.In this work, several new groups have been introduced to represent the activity coefficients for many biochemicals with better accuracy. For sugars, a portion containing asymmetric carbon atoms

Hidetoshi Kuramochi; Hidetaka Noritomi; Daisuke Hoshino; Kunio Nagahama

1997-01-01

67

Liquid Phase Synthesis of MTBE from Methanol and Isobutene over Acid Zeolites and Amberlyst-15  

Microsoft Academic Search

The liquid phase synthesis of methyl tert-butyl ether (MTBE) from methanol and isobutene over H-Beta and US-Y zeolite catalysts was studied in the temperature range 30–120°C. Up to 100°C, commercial H-Beta zeolite samples with small crystal size were more active than acid Amberlyst-15 (reference catalyst) and noticeably more active than US-Y, confirming results obtained under vapour phase conditions. The influence

F. Collignon; R. Loenders; J. A. Martens; P. A. Jacobs; G. Poncelet

1999-01-01

68

Equilibrium constants for the liquid-phase synthesis of isopropyl tert-butyl ether from 2-propanol and isobutene  

SciTech Connect

Equilibrium constants for the liquid-phase addition of 2-propanol to isobutene to give isopropyl tert-butyl ether (IPTBE) were determined experimentally in the temperature range 303--353 K and at 1.6 MPa. To reach etherification equilibrium, the macroporous sulfonic resin Bayer K-2631 was used as the catalyst. The UNIFAC estimates of activity coefficients were used to describe the liquid-phase nonideality. The thermodynamic equilibrium constants and the enthalpy, free energy, and entropy changes of the reaction were given as a function of temperature. At 298.15 K, the standard molar reaction enthalpy {Delta}{sub r}H{degree}{sub m}(298.15 K) is {minus}(22.9 {+-} 1.3) kJ/mol, in agreement with literature data, and the standard molar reaction entropy {Delta}{sub r}S{degree}{sub m}(298.15 K) and free energy {Delta}{sub r}G{degree}{sub m}(298.15 K) are {minus}(60.3 {+-} 0.5) J/mol{times}K and {minus}(4.9 {+-} 1.4) kJ/mol, respectively. Finally, at 298.15 K the standard molar enthalpy of formation {Delta}{sub f}H{degree}{sub m}(l, 298.15 K) and the standard molar entropy of IPTBE S{degree}{sub m}(l, 298.15 K) were estimated to be {minus}(378.5 {+-} 2.7) kJ/mol and 337.6 {+-} 1.5 J/(mol{times}K), respectively.

Calderon, A.; Tejero, J.; Izquierdo, J.F.; Iborra, M.; Cunill, F. [Univ. of Barcelona (Spain) Chemical Engineering Dept.] [Univ. of Barcelona (Spain) Chemical Engineering Dept.

1997-03-01

69

Nitroxy-radicals in the Liquid-phase Oxidation Reactions of Organic Compounds  

NASA Astrophysics Data System (ADS)

The review is devoted to the mechanism of the action of stable nitroxy-radicals in liquid-phase oxidation reactions of organic compounds. The chemical reactions which take place with participation of nitroxy-radicals are examined and their kinetic parameters are presented. The causes of the high inhibition coefficients and the possible ways of regenerating the nitroxy-radicals from their reaction products are discussed. The phenomenon of the selective inhibition of polymerisation processes accompanying oxidation is described and the conditions necessary for selective inhibition and the possibility of using nitroxy-radicals for this purpose are discussed. The bibliography includes 97 references.

Maslov, S. A.; Zaikov, Gennadii E.

1987-08-01

70

Selectivity among organic sulfur compounds in one- and two-liquid-phase cultures of Rhodococcus sp. strain JVH1.  

PubMed

The selectivity of Rhodococcus sp. strain JVH1 among selected sulfidic and thiophenic compounds was investigated in both single-liquid-phase (aqueous) cultures and in two-liquid-phase cultures, where the sulfur compounds were dissolved in 2,2,4,4,6,8,8-heptamethylnonane as the immiscible organic carrier phase. In the single-liquid-phase cultures, Rhodococcus sp. strain JVH1 showed a preference for benzyl sulfide over both 1,4-dithiane and benzothiophene. An increased lag was observed in the degradation of benzyl sulfone and benzothiophene sulfone when both compounds were present. These results were consistent with a competitive inhibition mechanism, affecting both sulfur oxidation and carbon-sulfur bond cleavage. In the two-liquid-phase cultures, the effect of partitioning between the two liquid phases dominated the desulfurization activity of the culture. This partitioning resulted in an apparent absence of selectivity, as well as decreases in lag time, extent of degradation, and time to completion of degradation. Desulfurization activity also depended on the growth phase of the cultures. Mass transfer rate limitations were not observed at the low degradation rates of 0.02 mmol day(-1) l(-1). Owing to the importance of partitioning, Rhodococcus sp. strain JVH1 is predicted to show nonselective activity towards the sulfur species in a whole crude oil. PMID:17091345

Kirkwood, Kathlyn M; Foght, Julia M; Gray, Murray R

2007-08-01

71

Application of ionic liquid in liquid phase microextraction technology.  

PubMed

Ionic liquids (ILs) are novel nonmolecular solvents. Their unique properties, such as high thermal stability, tunable viscosity, negligible vapor pressure, nonflammability, and good solubility for inorganic and organic compounds, make them excellent candidates as extraction media for a range of microextraction techniques. Many physical properties of ILs can be varied, and the structural design can be tuned to impart the desired functionality and enhance the analyte extraction selectivity, efficiency, and sensitivity. This paper provides an overview of the applications of ILs in liquid phase microextraction technology, such as single-drop microextraction, hollow fiber based liquid phase microextraction, and dispersive liquid-liquid microextraction. The sensitivity, linear calibration range, and detection limits for a range of target analytes in the methods were analyzed to determine the advantages of ILs in liquid phase microextraction. PMID:23002004

Han, Dandan; Tang, Baokun; Lee, Yu Ri; Row, Kyung Ho

2012-11-01

72

On liquid-liquid mass transfer in two-liquid-phase fermentations  

Microsoft Academic Search

Almost all two-liquid phase bioprocesses are characterized by the presence of surface active materials (biosurfactants), which significantly influence the interaction between the phases. In order to predict mass transfer rates during cultivations of Pseudomonas oleovorans biosurfactant was isolated from the biosuspension and added in defined amounts to n-octane\\/water model-dispersions. Effects of biosurfactant concentration on interfacial tension, mean Sauter-diameter, drop size

A. Kollmer; A. Schmid; P. Rudolf von Rohr; B. Sonnleitner

1999-01-01

73

Method to update the coefficients of the secondary path filter under active noise control  

Microsoft Academic Search

In active noise control systems using a filtered-x algorithm, the secondary path must be identified before the coefficients of the noise control filter are updated. The secondary path, however, has an impulse response that is continually changing in practical systems. This change degrades noise reduction and the stability of the system. Therefore, the coefficients of the secondary path filter must

Kensaku Fujii; Juro Ohga

2001-01-01

74

Prediction of limiting activity coefficients by a modified separation of cohesive energy density model and UNIFAC  

Microsoft Academic Search

A modified separation of cohesive energy density (MOSCED) model was developed to predict limiting activity coefficients (..gamma..infinity's) using only pure component parameters. For 3357 ..gamma..infinity's, an average error of 9.1% was achieved with very few errors greater than 30%. The data included activity coefficients of both protic and aprotic (but nonaqueous) systems over wide temperature ranges. The results compared very

Eugene R. Thomas; Charles A. Eckert

1984-01-01

75

New topic of supercritical fluids: local activity coefficients of supercritical solvent and cosolvent around solute.  

PubMed

The study of inhomogeneity in supercritical fluids (SCFs) is of great importance. In this work, we propose the concept of local activity coefficients in supercritical (SC) solutions, which link thermodynamics and inhomogeneity in SC systems. The local activity coefficients of CO(2)+acetonitrile+phenol blue and CO(2)+acetic acid+phenol blue systems are investigated at 308.15 K in critical region and outside critical region. To do this, the local compositions of CO(2)+acetonitrile and CO(2)+acetic acid mixed solvents around phenol blue are first estimated using UV-visible spectroscopy. Then it is considered that there exist bulk phase and local phase around phenol blue in the systems. The activity coefficients of CO(2) and the cosolvents (acetonitrile or acetic acid) in bulk phase are calculated using Peng-Robinson equation of state. The local activity coefficients of CO(2) and the cosolvents are then calculated on the basis of thermodynamic principles. It is demonstrated that in the critical region the local activity coefficients differ from bulk activity coefficients significantly and are sensitive to pressure. This can explain many unusual phenomena in SC systems in critical region thermodynamically. PMID:18345909

Hou, Minqiang; Zhang, Xiaogang; Han, Buxing; Song, Jiyuan; Liu, Gang; Zhang, Zhaofu; Zhang, Jianling

2008-03-14

76

New topic of supercritical fluids: Local activity coefficients of supercritical solvent and cosolvent around solute  

NASA Astrophysics Data System (ADS)

The study of inhomogeneity in supercritical fluids (SCFs) is of great importance. In this work, we propose the concept of local activity coefficients in supercritical (SC) solutions, which link thermodynamics and inhomogeneity in SC systems. The local activity coefficients of CO2+acetonitrile+phenol blue and CO2+acetic acid+phenol blue systems are investigated at 308.15 K in critical region and outside critical region. To do this, the local compositions of CO2+acetonitrile and CO2+acetic acid mixed solvents around phenol blue are first estimated using UV-visible spectroscopy. Then it is considered that there exist bulk phase and local phase around phenol blue in the systems. The activity coefficients of CO2 and the cosolvents (acetonitrile or acetic acid) in bulk phase are calculated using Peng-Robinson equation of state. The local activity coefficients of CO2 and the cosolvents are then calculated on the basis of thermodynamic principles. It is demonstrated that in the critical region the local activity coefficients differ from bulk activity coefficients significantly and are sensitive to pressure. This can explain many unusual phenomena in SC systems in critical region thermodynamically.

Hou, Minqiang; Zhang, Xiaogang; Han, Buxing; Song, Jiyuan; Liu, Gang; Zhang, Zhaofu; Zhang, Jianling

2008-03-01

77

Green aspects, developments and perspectives of liquid phase microextraction techniques.  

PubMed

Determination of analytes at trace levels in complex samples (e.g. biological or contaminated water or soils) are often required for the environmental assessment and monitoring as well as for scientific research in the field of environmental pollution. A limited number of analytical techniques are sensitive enough for the direct determination of trace components in samples and, because of that, a preliminary step of the analyte isolation/enrichment prior to analysis is required in many cases. In this work the newest trends and innovations in liquid phase microextraction, like: single-drop microextraction (SDME), hollow fiber liquid-phase microextraction (HF-LPME), and dispersive liquid-liquid microextraction (DLLME) have been discussed, including their critical evaluation and possible application in analytical practice. The described modifications of extraction techniques deal with system miniaturization and/or automation, the use of ultrasound and physical agitation, and electrochemical methods. Particular attention was given to pro-ecological aspects therefore the possible use of novel, non-toxic extracting agents, inter alia, ionic liquids, coacervates, surfactant solutions and reverse micelles in the liquid phase microextraction techniques has been evaluated in depth. Also, new methodological solutions and the related instruments and devices for the efficient liquid phase micoextraction of analytes, which have found application at the stage of procedure prior to chromatographic determination, are presented. PMID:24401382

Spietelun, Agata; Marcinkowski, ?ukasz; de la Guardia, Miguel; Namie?nik, Jacek

2014-02-15

78

CELLULOSE EXTRACTION FROM PALM KERNEL CAKE USING LIQUID PHASE OXIDATION  

Microsoft Academic Search

Cellulose is widely used in many aspect and industries such as food industry, pharmaceutical, paint, polymers, and many more. Due to the increasing demand in the market, studies and work to produce cellulose are still rapidly developing. In this work, liquid phase oxidation was used to extract cellulose from palm kernel cake to separate hemicellulose, cellulose and lignin. The method

FARM YAN YAN; DUDUKU KRISHNIAH; MARIANI RAJIN; AWANG BONO

79

Liquid-phase epitaxy of lead-doped indium antimonide  

Microsoft Academic Search

Indium antimonide was doped with lead under liquid-phase epitaxial (LPE) conditions, permitting the composition of the starting phase and the temperature of the process to be varied within wide limits. To obtain the maximum solubility of lead at any chosen LPE temperature it was used as a metallic solvent. It was found that the solubility of lead in indium antimonide

R. Kh. Akchurin; N. D. Kovalevskii

1986-01-01

80

Growth of Hexagonal Ferrite Films by Liquid Phase Epitaxy.  

National Technical Information Service (NTIS)

Single crystal hexagonal ferrite layers were grown by the isothermal dipping method of LPE (liquid phase epitaxy) using a BaO-B2O3 flux. Substrate crystals were of two different types: hexagonal ferrite and Mg(In,Ga)2O4 spinel. By adding ZnO to the LPE me...

H. L. Glass F. S. Stearns

1977-01-01

81

Liquid Phase Methanation. Monthly Progress Report, January--March 1975.  

National Technical Information Service (NTIS)

Work on the liquid phase methanation project continued with combined shift/methanation studies. As long as H sub 2 /CO ratios were greater than 1, water injection had little effect. Under such conditions, the circulating oil stream apparently contains suf...

1975-01-01

82

Liquid phase methanation of high concentration CO synthesis gas  

Microsoft Academic Search

Chem Systems Inc. believes that the Liquid Phase Methanation process can become an economic, reliable, and versatile method of converting synthesis gas mixtures to high-Btu gas. The process consists essentially of pumping an inert liquid upward through a reactor at a velocity sufficient to fluidize the catalyst and remove the reaction heat. A low-Btu gas is passed concurrently up the

D. B. Blum; M. B. Sherwin; M. E. Frank

1974-01-01

83

Transient liquid-phase bonding using coated metal powders  

Microsoft Academic Search

Powder particles coated with a small amount of melting point depressant (MPD) reveal different sintering behavior in comparison to an uncoated powder mixture of the same composition. Interlayers consisting of the coated powder particles were used in the transient liquid-phase (TLP) bonding process. The coating material and the thickness of the deposit are important parameters that influence shrinkage. The amount

W. D. Zhuang; T. W. Eagar

1997-01-01

84

Developments in hollow fibre-based, liquid-phase microextraction  

Microsoft Academic Search

The demand for automation in analytical liquid-liquid extraction (LLE) combined with organic solvent reduction or elimination has led to the recent development of liquid-phase microextraction (LPME) based on disposable hollow fibres. In this concept, analytes of interest are extracted from aqueous samples, through a thin layer of organic solvent immobilized within the pores of a porous hollow fibre, and into

Knut Einar Rasmussen; Stig Pedersen-Bjergaard

2004-01-01

85

Tunable Microwave Filters using YIG Grown by Liquid Phase Epitaxy  

Microsoft Academic Search

Original work is described on the application of refinements in Liquid Phase Epitaxy (LPE) of yttrium iron garnet (YIG) to the fabrication of tunable microwave filters. The advantages in cost and performance of this approach over the conventional YIG sphere technology are discussed. The developments in the LPE of YIG and the reactor used are described. The viability of LPE-YIG

I. T. Simpson; I. F. Morton; J. M. Owens; R. D. Pringle

1974-01-01

86

Magnetostatic propagation in thin films of liquid phase epitaxy YIG  

Microsoft Academic Search

Magnetostatic surface wave (MSSW) propagation loss and ferrimagnetic resonance linewidth of thin films of liquid phase epitaxy yttrium iron garnet were measured in the frequency range 2 to 9 GHz. With increasing frequency, both the loss and linewidth initially decreased to a minimum value at about 3 GHz and thereafter increased linearly with frequency. The measurements are in agreement with

D. Webb; C. Vittoria; P. Lubitz; H. Lessoff

1975-01-01

87

In situ monitoring of liquid phase electroepitaxial growth  

NASA Technical Reports Server (NTRS)

In situ monitoring of the layer thickness during liquid phase electroepitaxy (LPEE) was achieved with a submicron resolution through precise resistance measurements. The new approach to the study and control of LPEE was applied to growth of undoped and Ge-doped GaAs layers. The in situ determined growth kinetics was found to be in excellent agreement with theory.

Okamoto, A.; Isozumi, S.; Lagowski, J.; Gatos, H. C.

1982-01-01

88

Liquid-phase compositions from vapor-phase analyses  

SciTech Connect

Arsenic normally is not considered to be a contaminant. However, because arsenic was found in many cylinders of UF{sub 6}, including in corrosion products, a study was performed of the distribution of the two arsenic fluorides, AsF{sub 3} and AsF{sub 5}, between liquid and vapor phases. The results of the study pertain to condensation or vaporization of liquid UF{sub 6}. This study includes use of various experimental data plus many extrapolations necessitated by the meagerness of the experimental data. The results of this study provide additional support for the vapor-liquid equilibrium model of J.M. Prausnitz and his coworkers as a means of describing the distribution of various impurities between vapor and liquid phases of UF{sub 6}. Thus, it is concluded that AsF{sub 3} will tend to concentrate in the liquid phase but that the concentration of AsF{sub 5} in the vapor phase will exceed its liquid-phase concentration by a factor of about 7.5, which is in agreement with experimental data. Because the weight of the liquid phase in a condensation operation may be in the range of thousands of times that of the vapor phase, most of any AsF{sub 5} will be in the liquid phase in spite of this separation factor of 7.5. It may also be concluded that any arsenic fluorides fed into a uranium isotope separation plant will either travel with other low-molecular-weight gases or react with materials present in the plant. 25 refs., 3 figs., 6 tabs.

Davis, W. Jr. (Oak Ridge Gaseous Diffusion Plant, TN (USA)); Cochran, H.D. (Oak Ridge National Lab., TN (USA))

1990-02-01

89

Enzymatic hydrolysis of penicillin for 6-APA production in three-liquid-phase system.  

PubMed

A dodecane/thermosensitive polymer/water three-liquid-phase system was introduced for enzymatic hydrolysis of penicillin G (Pen G) for 6-aminopenicillanic acid (6-APA). The enzyme was covalently attached to the terminal of PEO-PPO-PEO polymer (L63), which would be transferred into a polymer coacervate phase at high temperature above its "cloud point". 6-APA was primarily resided in the aqueous phase due to its zwitterionic nature. More than 70% phenylacetic acid (PAA) was transferred into the organic phase using trioctylmethylammonium hydroxide and trihexyl-(tetradecyl)phosphonium bis 2,4,4-trimethylpentylphosphinate ionic liquids (Cyphos IL-104) mixture at pH 5.5, while most of Pen G resided in water. As a result, high operational pH was permitted in three-liquid-phase system, which leads to higher enzymatic activity (120 IU at 40 degrees C) and stability (enzymatic half-time up to 55 h at 60 degrees C) in comparison with the value in butyl acetate/water two-phase system. On the other hand, two products in three-liquid-phase system might be automatically separated from the enzyme sphere into different phases at the same time, which facilitated the reaction equilibrium towards the product's side with 6-APA productivity of 80% at 42 degrees C, pH 5.5. PMID:18456946

Jiang, Yangyang; Xia, Hansong; Guo, Chen; Mahmood, Iram; Liu, Huizhou

2008-02-01

90

Commercial-Scale Demonstration of the Liquid Phase Methanol (LPMEOH(TM)) Process  

SciTech Connect

The Liquid Phase Methanol (LPMEOH(TM)) Demonstration Project at Kingsport, Tennessee, is a $213.7 million cooperative agreement between the U.S. Department of Energy (DOE) and Air Products Liquid Phase Conversion Company, L.P. (the Partnership). The LPMEOIWM Process Demonstration Unit is being built at a site located at the Eastman Chemical Company (Eastman) complex in Kingsport. During this quarter, the Cooperative Agreement was modified (Mod AO11) on 8 October 1996, authorizing the transition born Budget Period No. 2 (Design and Construction) to the . final Budget Period (Commissioning, Start-up, and Operation), A draft Topical Report on Process Economics Studies concludes that methanol coproduction with integrated gasification combined cycle (IGCC) electric power utilizing the LPMEOW process technology, will be competitive in serving local market needs. Planning for a proof-of- concept test run of the liquid phase dimethyl ether (DME) process at the LaPorte Alternative Fuels Development Unit (AFDU) was recommended; and a deeision to proceed is pending. Construction (Task 2.2) is 97'Mo complete, asof31 December 1996. Completion of pipe pressure testing has taken longer than expected. This will delay completion of construction by about three weeks. Commissioning activities (Task 2.3) commenced in mid-October of 1996, and the demonstration unit is scheduled to be mechanically complete on 24 January 1997.

None

1996-12-31

91

Prediction of activity coefficients in liquid aerosol particles containing organic compounds, dissolved inorganic salts, and water—Part 2: Consideration of phase separation effects by an X-UNIFAC model  

NASA Astrophysics Data System (ADS)

A thermodynamic model is presented for predicting the formation of particulate matter (PM) within an aerosol that contains organic compounds, inorganic salts, and water. Neutral components are allowed to partition from the gas phase to the PM, with the latter potentially composed of both a primarily aqueous ( ?) liquid phase and a primarily organic ( ?) liquid phase. Partitioning is allowed to occur without any artificial restraints: when both ? and ? PM phases are present, ionic constituents are allowed to partition to both. X-UNIFAC.2, an extended UNIFAC method based on Yan et al. (1999. Prediction of vapor-liquid equilibria in mixed-solvent electrolyte systems using the group contribution concept. Fluid Phase Equilibria 162, 97-113), was developed for activity coefficient estimation. X-UNIFAC.2 utilizes the standard UNIFAC terms, a Debye-Hückel term, and a virial equation term that represents the middle-range (MR) contribution to activity coefficient effects. A large number (234) of MR parameters are already available from Yan et al. (1999). Six additional MR parameters were optimized here to enable X-UNIFAC.2 to account for interactions between the carboxylic acid group and Na +, Cl -, and Ca 2+. Predictions of PM formation were made for a hypothetical sabinene/O 3 system with varying amounts of NaCl in the PM. Predictions were also made for the chamber experiments with ?-pinene/O 3 (and CaCl 2 seed) carried out by Cocker et al. (2001. The effect of water on gas-particle partitioning of secondary organic aerosol. Part I. ?-pinene/ozone system. Atmospheric Environment 35, 6049-6072); good agreement between the predicted and chamber-measured PM mass concentrations was achieved.

Chang, Elsa I.; Pankow, James F.

92

Liquid-phase hydrogenation of alkenes and aromatic compounds with Pd-loaded oxidized diamond catalyst  

Microsoft Academic Search

Hydrogenation reactions of alkenes (cyclohexene, ethyl acrylate, styrene and 1,5-cyclooctadiene) and aromatic compounds (o-, m- and p-xylene) were carried out in order to examine the activity of palladium-loaded surface-oxidized diamond (Pd\\/O-Dia) catalyst\\u000a in liquid-phase hydrogenation. The catalytic performance was compared to commercial palladium-loaded activated carbon (Pd\\/C)\\u000a catalyst. The catalyst activities were evaluated by conversions of reactants and H2 uptake rates

Na-Oki Ikenaga; Tomonari Kiyomi; Itaru Yonezawa; Chieko Yukawa; Toshimitsu Suzuki

2008-01-01

93

Measuring methods of infinite dilution activity coefficients and a database for systems including water  

Microsoft Academic Search

Experimental techniques for the determination of infinite dilution activity coefficients and their improvements are reviewed. Generally, the measuring techniques can be classified as the indirect and direct methods. The indirect methods include the extrapolations from vapor-liquid equilibrium data and calculations from the other thermodynamic data, such as liquid-liquid equilibrium data, gas-liquid partition coefficient data and so on. The direct methods

Kazuo Kojima; Suojiang Zhang; Toshihiko Hiaki

1997-01-01

94

Recent Advances in the Liquid?Phase Synthesis of Metal Nanostructures with Controlled Shape and Size for Catalysis  

Microsoft Academic Search

Recent advances in the liquid?phase synthesis of metal nanostructures of different sizes and shapes are reviewed regarding their catalytic properties. The controlled synthesis of nanostructures is based on the colloid chemistry techniques in the solution, which use organic nanoreactors and a variety of stabilizers. Their catalytic activity and selectivity depend on the particle's shape and size, as shown for Suzuki

Natalia Semagina

2009-01-01

95

Group contributions to activity coefficients from the hard sphere expansion corresponding states theory  

NASA Astrophysics Data System (ADS)

A new method has been developed for predicting liquid activity coefficients in ternary mixtures from group contributions. In this method, activity coefficients are obtained from the excess Gibbs free energy of mixing at constant temperature and pressure. In calculating this excess function, the constituent and mixture Gibbs free energies are each represented by an expansion about a pure reference fluid in powers of ratios of hard-sphere diameters and molecular attraction parameters. When the pure component differs from the reference by a single structural group, these ratios represent, respectively, the size contribution and the attraction contribution of this group to the thermodynamic property of the pure fluid. Contributions of intermolecular repulsion to the excess Gibbs free energy are calculated directly from hard-sphere equations of state for the mixture and pure components. The effect of polar contributions calculated by a Padé approximant is also examined. Results indicate that the method developed from the hard-sphere expansion corresponding-states theory is useful for predicting activity coefficients in ternary mixtures when unlike-pair interaction parameters are fitted to binary activity coefficient data. Furthermore, the method shows promise in providing a theoretical basis for applying group contributions to activity coefficients.

Quock, D. E. R.; Leland, T. W.

1986-03-01

96

Layered material gamma-ZrP supported platinum catalyst for liquid-phase reaction: a highly active and selective catalyst for hydrogenation of the nitro group in para-chloronitrobenzene.  

PubMed

Chemoselective hydrogenation of para-chloronitrobenzene without any dechlorination over Pt/gamma-ZrP catalyst proceeds effectively, which provides a clean and convenient approach to produce useful para-chloroaniline with excellent activity and selectivity. PMID:18536814

Wang, Fang; Liu, Junhua; Xu, Xianlun

2008-05-01

97

A single-component liquid-phase hydrogen storage material.  

PubMed

The current state-of-the-art for hydrogen storage is compressed H(2) at 700 bar. The development of a liquid-phase hydrogen storage material has the potential to take advantage of the existing liquid-based distribution infrastructure. We describe a liquid-phase hydrogen storage material that is a liquid under ambient conditions (i.e., at 20 °C and 1 atm pressure), air- and moisture-stable, and recyclable; releases H(2) controllably and cleanly at temperatures below or at the proton exchange membrane fuel cell waste-heat temperature of 80 °C; utilizes catalysts that are cheap and abundant for H(2) desorption; features reasonable gravimetric and volumetric storage capacity; and does not undergo a phase change upon H(2) desorption. PMID:22070729

Luo, Wei; Campbell, Patrick G; Zakharov, Lev N; Liu, Shih-Yuan

2011-12-01

98

Powder metallurgy: Solid and liquid phase sintering of copper  

NASA Technical Reports Server (NTRS)

Basic powder metallurgy (P/M) principles and techniques are presented in this laboratory experiment. A copper based system is used since it is relatively easy to work with and is commercially important. In addition to standard solid state sintering, small quantities of low melting metals such as tin, zinc, lead, and aluminum can be added to demonstrate liquid phase sintering and alloy formation. The Taguchi Method of experimental design was used to study the effect of particle size, pressing force, sintering temperature, and sintering time. These parameters can be easily changed to incorporate liquid phase sintering effects and some guidelines for such substitutions are presented. The experiment is typically carried out over a period of three weeks.

Sheldon, Rex; Weiser, Martin W.

1993-01-01

99

Liquid-phase sintering of iron aluminide-bonded ceramics  

SciTech Connect

Iron aluminide intermetallics exhibit excellent oxidation and sulfidation resistance and are therefore considered as the matrix in metal matrix composites, or the binder in hard metals or cermets. In this paper the authors discuss the processing and properties of liquid-phase sintered iron aluminide-bonded ceramics. It is found that ceramics such as TiB{sub 2}, ZrB{sub 2}, TiC, and WC may all be liquid phase-sintered. nearly complete densification is achieved for ceramic volume fractions ranging up to 60%. Depending on the composition, room temperature three point-bend strengths and fracture toughnesses reaching 1,500 MPa and 30 MPa m{sup 1/2}, respectively, have been found. Since the processing was carried out in a very simple manner, optimized processing is likely to result in further improvements.

Schneibel, J.H.; Carmichael, C.A. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

1995-12-31

100

On Asymmetric Diffusional Solidification During Transient Liquid Phase Bonding  

NASA Astrophysics Data System (ADS)

The underlying cause of asymmetric diffusion solidification which alters microstructure during transient liquid phase bonding under low temperature gradient was studied. A new solute-conserving asymmetric numerical model coupled with experimental verification showed that a transition from bi-directional to unidirectional solidification, under a constant temperature gradient, is controlled by competition between liquid and solid-state diffusion at one of the two liquid-solid interfaces. This mechanistic understanding would aid a more effective use of the process.

Ghobadi Bigvand, A.; Ojo, Olanrewaju A.

2014-04-01

101

Solid–Liquid Phase Change Driven by Internal Heat Generation  

SciTech Connect

This article presents results of solid-liquid phase change, the Stefan Problem, where melting is driven internal heat generation, in a cylindrical geometry. The comparison between a quasi-static analytical solution for Stefan numbers less than one and numerical solutions shows good agreement. The computational results of phase change with internal heat generation show how convection cells form in the liquid region. A scale analysis of the same problem shows four distinct regions of the melting process.

John Crepeau; Ali s. Siahpush

2012-07-01

102

Growth of YEu Garnets by Liquid Phase Epitaxy  

Microsoft Academic Search

We have measured the saturation temperature, Ts, for growth of (YEu)3(FeGa)5O12 films in a PbO-B2O3 flux over a wide range of oxide concentrations and over the temperature range 850 – 1050°C. This temperature range is of the most practical interest in film growth by liquid phase epitaxy (LPE). We have also studied the (YGdTm)3(FeGa)5O12 system less extensively. Ts, as expected,

B. F. Stein; R. M. Josephs

1973-01-01

103

Growth of YEu Garnets by Liquid Phase Epitaxy  

Microsoft Academic Search

We have measured the saturation temperature, Ts, for growth of (YEu)3(FeGa)5O12 films in a PbO-B2O3 flux over a wide range of oxide concentrations and over the temperature range 850 - 1050°C. This temperature range is of the most practical interest in film growth by liquid phase epitaxy (LPE). We have also studied the (YGdTm)3 (FeGa)5O12 system less extensively. Ts, as

B. F. Stein; R. M. Josephs

1973-01-01

104

Solid + liquid phase equilibria in the hydroxylammonium nitrate + water system  

Microsoft Academic Search

The binary solid + liquid phase diagram has been measured for the water + hydroxylammonium nitrate (HAN) system. The phase diagram is a simple eutectic type with the eutectic at 231.5 K (41.7°C) and a mole fraction HAN of 0.281 (wt fraction HAN - 0.676).The enthalpy of fusion of the HAN was determined from the solid + liquid results to

Johanne I. Artman; J. Bevan Ott

1989-01-01

105

MASS TRANSFER IN THE LIQUID PHASE METHANOL SYNTHESIS PROCESS  

Microsoft Academic Search

The mass transfer characteristics of the liquid phase methanol synthesis process were experimentally investigated using a one-liter, mechanically agitated slurry reactor. The CuO\\/ZnO\\/Al2O3 catalyst was crushed to -140 mesh and suspended in an inert mineral oil (Witco # 40). The catalyst loading was varied within limits of experimental feasibility. The effects of temperature, pressure, level of oil, impeller speed, and

Vetkav R. Parameswaran; Makarand R. Gogate; Byung Gwon Lee; Sunggyu Lee

1991-01-01

106

Transient liquid phase (TLP) bonding for microsystem packaging applications  

Microsoft Academic Search

This paper explores the use of transient liquid phase bonding for microsystem packaging applications. Two types of bonds are demonstrated: a thin-film evaporated indium-gold bond and an electroplated nickel-tin bond. Both bonds are formed at 300°C for about 1.5 hours in a conventional wafer bonder. The wafers were heated to over 400 °C for more than an hour after bonding

Warren Welch; Junseok Chae; Sang-Hyun Lee; Navid Yazdi; Khalil Najafi

2005-01-01

107

THERMAL STABILITY ANALYSIS OF THE LIQUID PHASE METHANOL SYNTHESIS REACTOR  

Microsoft Academic Search

The effect of addition of an inert liquid phase on the rate of heat generation in the catalytic synthesis of methanol from syngas has been studied. Gas compositions typical of product gases from Lurgi and Koppers-Totzek gasifiers, represented by H2-rich and CO-rich syngas respectively, were used to experimentally verify the “slope” and “dynamic” critria in a three-phase fixed bed recycle

Makarand R. Gogate; Srinivas Desirazu; Jozsef M. Berty; Sunggyu Lee

1992-01-01

108

Selection of solvents for extractive distillation: A data bank for activity coefficients at infinite dilution  

SciTech Connect

Activity coefficients at infinite dilution provide a useful tool for solvent selection in extractive distillation processes. A computerized data bank containing information referring to 2097 experimental values of infinite dilution activity coefficients of solutes in potential solvents was established. A total of 129 solvents, 60 solutes (paraffins, olefins, aromatics, naphthenes and chlorides), and 1007 solute/solvent pairs were considered. The merits of group contribution models such as UNIFAC and ASOG are assessed by comparing experimental and predicted values of infinite dilution activity coefficients and selectivities. Mean deviations in the range 24-91% were obtained for the different classes of solutes. For typical separations, lists of solvents ordered in terms of experimental and calculated selectivities were compared.

Bastos, J.C.; Medina, A.G.; Soares, M.E.

1984-04-01

109

Possibilities of liquid-phase low-temperature deposition of manganese oxides on NaY synthetic zeolite  

SciTech Connect

This paper studies the possibilities of low-temperature liquid-phase deposition of manganese oxides on NaY synthetic zeolite and compares the results with literature data. The experiments were conducted in accordance with a design matrix that is presented in a table. The coefficients of regression equations are presented which describe the experimental responses against the background of the errors. A summary is given of rounded-off estimates of relative errors of determination of manganese oxides on the three zeolite types studied and the average values of responses of the same type for all the zeolites. It follows that the optimal estimates of the Mn/sub 2/O/sub 3/ and MnO/sub 2/ contents are the same for all the zeolites within the averaged error limits, while the estimates of MnO contents and conversion of Mn (II) from solution on the zeolite surface are not the same for clinoptilolite as for synthetic NaY, confirming that oxidation proceeds more actively on the NaY surface, while conversion is very pronounced in the case of clinoptilolite.

Eremeev, A.P.; Petrusevich, E.F.

1985-05-20

110

Packed-bed liquid-phase dispersion in pulsed gas-liquid downflow  

SciTech Connect

A theoretical analysis of a pulsed gas-liquid downward flow through a packed bed showed that the axial dispersion of the liquid-phase observed in such flows is mainly caused by the difference in velocity and rapid mixing between fast-moving liquid slugs and slow-moving liquid films. This chromatographic behavior was described by a model which considers the liquid phase as consisting of two continuous phases flowing cocurrently at different velocities with continuous material exchange between the two streams. The liquid dispersion in the column may be characterized by a single mixing parameter. Impulse response experiments, in good accord with the model, showed that liquid dispersion decreases with increasing liquid flow rate because of improving mixing, attains a constant asymptotic value at high gas velocities, and is generally smaller in pulsed flow than in the gas-continuous (trickle) flow regime. Additional advantages of pulsed flow operation in catalytic reactors are increased wetting of the pellets, enhanced transport coefficients, and improved flow uniformity through the bed.

Lerou, J.J.; Glasser, D.; Luss, D.

1980-02-01

111

Prediction of limiting activity coefficients by a modified separation of cohesive energy density model and UNIFAC  

SciTech Connect

A modified separation of cohesive energy density (MOSCED) model was developed to predict limiting activity coefficients (..gamma..infinity's) using only pure component parameters. For 3357 ..gamma..infinity's, an average error of 9.1% was achieved with very few errors greater than 30%. The data included activity coefficients of both protic and aprotic (but nonaqueous) systems over wide temperature ranges. The results compared very well with the predictions of the leading predictive technique in the literature, the UNIFAC solution of groups approach (average error 20.5%).

Thomas, E.R.; Eckert, C.A.

1984-04-01

112

Modeling the solid-liquid phase transition in saturated triglycerides  

NASA Astrophysics Data System (ADS)

We investigated theoretically two competing published scenarios for the melting transition of the triglyceride trilaurin (TL): those of (1) Corkery et al. [Langmuir 23, 7241 (2007)], in which the average state of each TL molecule in the liquid phase is a discotic ``Y'' conformer whose three chains are dynamically twisted, with an average angle of ~120° between them, and those of (2) Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)], in which the liquid-state conformation of the TL molecule in the liquid phase is a nematic h*-conformer whose three chains are in a modified ``chair'' conformation. We developed two competing models for the two scenarios, in which TL molecules are in a nematic compact-chair (or ``h'') conformation, with extended, possibly all-trans, chains at low-temperatures, and in either a Y conformation or an h* conformation in the liquid state at temperatures higher than the phase-transition temperature, T*=319 K. We defined an h-Y model as a realization of the proposal of Corkery et al. [Langmuir 23, 7241 (2007)], and explored its predictions by mapping it onto an Ising model in a temperature-dependent field, performing a mean-field approximation, and calculating the transition enthalpy ?H. We found that the most plausible realization of the h-Y model, as applied to the solid-liquid phase transition in TL, and likely to all saturated triglycerides, gave a value of ?H in reasonable agreement with the experiment. We then defined an alternative h-h* model as a realization of the proposal of Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)], in which the liquid phase exhibits an average symmetry breaking similar to an h conformation, but with twisted chains, to see whether it could describe the TL phase transition. The h-h* model gave a value of ?H that was too small by a factor of ~3-4. We also predicted the temperature dependence of the 1132 cm-1 Raman band for both models, and performed measurements of the ratios of three TL Raman bands in the temperature range of -20 °C<=T<=90 °C. The experimental results were in accord with the predictions of the h-Y model and support the proposal of Corkery et al. [Langmuir 23, 7241 (2007)] that the liquid state is made up of molecules that are each, on average, in a Y conformation. Finally, we carried out computer simulations of minimal-model TLs in the liquid phase, and concluded that although the individual TL molecules are, on average, Y conformers, long-range discotic order is unlikely to exist.

Pink, David A.; Hanna, Charles B.; Sandt, Christophe; MacDonald, Adam J.; MacEachern, Ronald; Corkery, Robert; Rousseau, Dérick

2010-02-01

113

Effect of liquid-phase content on the contact-mechanical properties of liquid-phase-sintered ?-SiC  

Microsoft Academic Search

Effect of the content of the intergranular phase (Y3Al5O12 or yttrium aluminum garnet or YAG) on the room-temperature contact-mechanical properties of pressureless, liquid-phase-sintered (LPS) ?-SiC ceramics has been studied. An increase in YAG vol.% is found to result in the expected degradation of the elastic modulus and the indentation yield strength in LPS SiC. However, with increasing YAG vol.% the

Oscar Borrero-López; Angel L. Ortiz; Fernando Guiberteau; Nitin P. Padture

2007-01-01

114

High-temperature properties of liquid-phase-sintered ?-SiC  

Microsoft Academic Search

We have characterized the high-temperature subcritical crack growth and oxidation resistance of a liquid-phase-sintered (LPS) SiC with 20% volume fraction yttrium aluminum garnet (YAG) second phase. Constant stress-rate testing in air in the temperature range 1100–1300°C yielded a crack growth exponent, n=38.9±9.9 and an activation energy, Qscg=(380±237) kJ mol?1. Oxidation followed parabolic kinetics in the temperature range 1100–1300°C with an

Robert P. Jensen; William E. Luecke; Nitin P. Padture; Sheldon M. Wiederhorn

2000-01-01

115

Activity coefficients of aqueous sodium chloride from 15?? to 50??C measured with a glass electrode  

USGS Publications Warehouse

Values of the mean activity coefficient of sodium chloride at 15??, 25??, 38?? and 50??C were determined for aqueous NaCl solutions of 0.01 to 1.0 molal from electromotive force measurements on the cell: (sodium-sensitive glass electrode, aqueous sodium chloride, silver chloride-silver).

Truesdell, A. H.

1968-01-01

116

Prediction of infinite dilution activity coefficients in aqueous solutions by group contribution models. A critical evaluation  

Microsoft Academic Search

Based on an extensive database, the predictive accuracy of the ASOG and several UNIFAC-type models has been critically evaluated for infinite dilution activity coefficients in aqueous solutions. In general, all the models give rather poor results with mean relative deviations of 45–72% (except the cases where the relative deviations are higher than 100%), whereas the modified UNIFAC (Dortmund) performs well

Suojiang Zhang; Toshihiko Hiaki; Masaru Hongo; Kazuo Kojima

1998-01-01

117

Modeling infinite dilution activity coefficients of environmental pollutants in water using conformal solution theory  

SciTech Connect

The fate of organic pollutants in the environment and in wastewater treatment processes is commonly modeled using a Henry`s law constant approach. By definition, Henry`s law constant is the product of a compound`s vapor pressure and infinite dilution activity coefficient. For many organic compounds in water solution, the infinite dilution activity coefficients are very large and are not adequately modeled by conventional methods such as UNIFAC. In this work, infinite dilution activity coefficients were determined for phenol, pyridine, aniline, p-toluidine, and o-toluidine in water by differential ebulliometry. An equation rigorously derived from conformal solution theory and van der Waals one-fluid mixing rules was used to model the temperature dependency of the infinite dilution activity coefficients. No corrections other than the introduction of two adjustable parameters were incorporated into the model to account for the strong interactions between molecules. Relationships derived from corresponding states theory were used to relate molecular parameters for size and energy interaction to the critical properties. Arithmetic mean combining rules and geometric mean combining rules were used to calculate size and interaction parameters, respectively.

Moore, R.C. [Univ. of Tennessee, Knoxville, TN (United States); Cochran, H.D.; Bienkowski, P.R. [Univ. of Tennessee, Knoxville, TN (United States)]|[Oak Ridge National Laboratory, Oak Ridge, TN (United States)

1995-04-01

118

Improved estimation of solubility and partitioning through correction of UNIFAC-derived activity coefficients  

Microsoft Academic Search

Octanol-water partition coefficients (K\\/sub ow\\/) of 75 compounds ranging over 9 orders of magnitude are correlated by log K\\/sub ow\\/ = -0.40 + 0.73 log (..gamma..\\/sub W\\/)\\/sub U\\/ -0.39 log (..gamma..â)\\/sub U\\/ (r = 0.98), where (..gamma..\\/\\/sub W\\/)\\/sub U\\/ and (..gamma..â)\\/sub U\\/ are UNIFAC-derived activity coefficients in water and octanol, respectively. The constants 0.73 and -0.39 are obtained empirically and

Sujit Banerjee; Philip H. Howard

1988-01-01

119

Coefficients for Active Transport and Thermogenesis of Ca2+-ATPase Isoforms  

PubMed Central

Coefficients for active transport of ions and heat in vesicles with Ca2+-ATPase from sarcoplasmic reticulum are defined in terms of a newly proposed thermodynamic theory and calculated using experiments reported in the literature. The coefficients characterize in a quantitative manner different performances of the enzyme isoforms. Four enzyme isoforms are examined, namely from white and red muscle tissue, from blood platelets, and from brown adipose mitochondria. The results indicate that the isoforms have a somewhat specialized function. White muscle tissue and brown adipose tissue have the same active transport coefficient ratio, but the activity level of the enzyme in white muscle is higher than in brown adipose tissue. The thermogenesis ratio is high in both white muscle and brown adipose tissue, in agreement with a specific role in nonshivering thermogenesis. Other isoforms do not have this ability to generate heat. A calcium-dependence of the coefficients is found, which can be understood as being in accordance with the role of this ion as a messenger in muscle contraction as well as in thermogenesis. The investigation points to new experiments related to structure as well as to function of the isoforms.

Kjelstrup, Signe; Barragan, Daniel; Bedeaux, Dick

2009-01-01

120

Synthesis of manganese nanoparticles in the liquid phase plasma.  

PubMed

The liquid phase plasma reduction method was applied to prepare the polycrystalline manganese nanoparticles from the solution of manganese chloride tetrahydrate. A bipolar pulsed power supply was used to generate discharge in the aqueous solutions. While large size of dendrite-shaped manganese nanoparticles were mostly observed in the initial stage and particle size decreased with discharge time. The particles were dispersed with less and less small particles by the addition of CTAB and anisotropic shapes nanoparticles were mostly observed at long time plasma-treated. Many spots could be seen in the ED pattern for polycrystalline particles. PMID:24205609

Kim, Hwan-Gi; Lee, Heon; Kim, Sun-Jae; Kim, Do-Heyoung; Kim, Jung-Sik; Kang, Sang-Yong; Jung, Sang-Chul

2013-09-01

121

Containerless liquid-phase processing of ceramic materials  

NASA Technical Reports Server (NTRS)

Containerless melting and solidification provides a powerful tool for investigation and synthesis of ceramic and glass materials. The work described in this article explored and extended the limits of ground-based experimentation by using aero-acoustic and aerodynamic levitation in combination with laser beam heating and melting to investigate ceramic and glass processing. Results of liquid-phase processing experiments on calcia-gallia and calcia-gallia-silica glass-forming mixtures, aluminum oxide, and ceramic superconductors are summarized. The work is discussed in the context of low gravity experimental and materials synthesis requirements and opportunities.

Weber, J. K. R.; Nordine, P. C.

1994-01-01

122

Thin film planar waveguide sensor for liquid phase absorbance measurements  

SciTech Connect

A thin film planar waveguide is studied for application as a chemical sensor for liquid-phase absorbance measurements. The waveguide is comprised of a thin film of tantalum pentoxide deposited on a glass substrate with a pair of diffraction gratings etched into the substrate surface. The buried grating couplers allow the launch and collection optics to be isolated from the liquid sample. The response to an absorbing dye and different refractive index (RI) solutions is studied and compared to theoretical predictions. The sensor has an absorbance sensitivity equivalent to a 1 mm path length in a conventional transmission measurement. A method to reduce the intensity changes due to solution RI is demonstrated.

DeGrandpre, M.D.; Burgess, L.W. (Univ. of Washington, Seattle (USA)); White, P.L.; Goldman, D.S. (Battelle Pacific Northwest Laboratory, Richland, WA (USA))

1990-09-15

123

First-Order Liquid-Liquid Phase Transition in Cerium  

NASA Astrophysics Data System (ADS)

We report the first experimental observation of a liquid-liquid phase transition in the monatomic liquid metal cerium, by means of in situ high-pressure high-temperature x-ray diffraction experiments. At 13 GPa, upon increasing temperature from 1550 to 1900 K high-density liquid transforms to a low-density liquid, with a density difference of 14%. Theoretic models based on ab initio calculations are built to investigate the observed phase behavior of the liquids at various pressures. The results suggest that the transition primarily originates from the delocalization of f electrons and is deemed to be of the first order that terminates at a critical point.

Cadien, A.; Hu, Q. Y.; Meng, Y.; Cheng, Y. Q.; Chen, M. W.; Shu, J. F.; Mao, H. K.; Sheng, H. W.

2013-03-01

124

Liquid phase synthesis of copper indium diselenide nanoparticles  

NASA Astrophysics Data System (ADS)

Nanoparticles of Copper Indium diselenide (CuInSe2), belongs to I-III-VI2 family has been synthesized via liquid phase route using ethylenediamine as a solvent. Characterization of as-grown particles is done by XRD, HRTEM, DLS, optical microscopy and UV-Vis spectroscopy. X-ray diffraction pattern confirmed that the CuInSe2 nanoparticles obtained reveals chalcopyrite structure. Particle size evaluated from dynamic light scattering of as grown particle possessing radius of 90 nm. The bandgap of 1.05eV is obtained from UV-Vis spectrum which will applicable to the solar cell devices.

Jakhmola, Priyanka; Agarwal, Garima; Jha, Prafulla K.; Bhatnagar, S. P.

2014-04-01

125

New and extended parameterization of the thermodynamic model AIOMFAC: calculation of activity coefficients for organic-inorganic mixtures containing carboxyl, hydroxyl, carbonyl, ether, ester, alkenyl, alkyl, and aromatic functional groups  

NASA Astrophysics Data System (ADS)

We present a new and considerably extended parameterization of the thermodynamic activity coefficient model AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) at room temperature. AIOMFAC combines a Pitzer-like electrolyte solution model with a UNIFAC-based group-contribution approach and explicitly accounts for interactions between organic functional groups and inorganic ions. Such interactions constitute the salt-effect, may cause liquid-liquid phase separation, and affect the gas-particle partitioning of aerosols. The previous AIOMFAC version was parameterized for alkyl and hydroxyl functional groups of alcohols and polyols. With the goal to describe a wide variety of organic compounds found in atmospheric aerosols, we extend here the parameterization of AIOMFAC to include the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkenyl, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon. Thermodynamic equilibrium data of organic-inorganic systems from the literature are critically assessed and complemented with new measurements to establish a comprehensive database. The database is used to determine simultaneously the AIOMFAC parameters describing interactions of organic functional groups with the ions H+, Li+, Na+, K+, NH4+, Mg2+, Ca2+, Cl-, Br-, NO3-, HSO4-, and SO42-. Detailed descriptions of different types of thermodynamic data, such as vapor-liquid, solid-liquid, and liquid-liquid equilibria, and their use for the model parameterization are provided. Issues regarding deficiencies of the database, types and uncertainties of experimental data, and limitations of the model, are discussed. The challenging parameter optimization problem is solved with a novel combination of powerful global minimization algorithms. A number of exemplary calculations for systems containing atmospherically relevant aerosol components are shown. Amongst others, we discuss aqueous mixtures of ammonium sulfate with dicarboxylic acids and with levoglucosan. Overall, the new parameterization of AIOMFAC agrees well with a large number of experimental datasets. However, due to various reasons, for certain mixtures important deviations can occur. The new parameterization makes AIOMFAC a versatile thermodynamic tool. It enables the calculation of activity coefficients of thousands of different organic compounds in organic-inorganic mixtures of numerous components. Models based on AIOMFAC can be used to compute deliquescence relative humidities, liquid-liquid phase separations, and gas-particle partitioning of multicomponent mixtures of relevance for atmospheric chemistry or in other scientific fields.

Zuend, A.; Marcolli, C.; Booth, A. M.; Lienhard, D. M.; Soonsin, V.; Krieger, U. K.; Topping, D. O.; McFiggans, G.; Peter, T.; Seinfeld, J. H.

2011-09-01

126

New and extended parameterization of the thermodynamic model AIOMFAC: calculation of activity coefficients for organic-inorganic mixtures containing carboxyl, hydroxyl, carbonyl, ether, ester, alkenyl, alkyl, and aromatic functional groups  

NASA Astrophysics Data System (ADS)

We present a new and considerably extended parameterization of the thermodynamic activity coefficient model AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) at room temperature. AIOMFAC combines a Pitzer-like electrolyte solution model with a UNIFAC-based group-contribution approach and explicitly accounts for interactions between organic functional groups and inorganic ions. Such interactions constitute the salt-effect, may cause liquid-liquid phase separation, and affect the gas-particle partitioning of aerosols. The previous AIOMFAC version was parameterized for alkyl and hydroxyl functional groups of alcohols and polyols. With the goal to describe a wide variety of organic compounds found in atmospheric aerosols, we extend here the parameterization of AIOMFAC to include the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkenyl, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon. Thermodynamic equilibrium data of organic-inorganic systems from the literature are critically assessed and complemented with new measurements to establish a comprehensive database. The database is used to determine simultaneously the AIOMFAC parameters describing interactions of organic functional groups with the ions H+, Li+, Na+, K+, NH4+, Mg2+, Ca2+, Cl-, Br-, NO3-, HSO4-, and SO42-. Detailed descriptions of different types of thermodynamic data, such as vapor-liquid, solid-liquid, and liquid-liquid equilibria, and their use for the model parameterization are provided. Issues regarding deficiencies of the database, types and uncertainties of experimental data, and limitations of the model, are discussed. The challenging parameter optimization problem is solved with a novel combination of powerful global minimization algorithms. A number of exemplary calculations for systems containing atmospherically relevant aerosol components are shown. Amongst others, we discuss aqueous mixtures of ammonium sulfate with dicarboxylic acids and with levoglucosan. Overall, the new parameterization of AIOMFAC agrees well with a large number of experimental datasets. However, due to various reasons, for certain mixtures important deviations can occur. The new parameterization makes AIOMFAC a versatile thermodynamic tool. It enables the calculation of activity coefficients of thousands of different organic compounds in organic-inorganic mixtures of numerous components. Models based on AIOMFAC can be used to compute deliquescence relative humidities, liquid-liquid phase separations, and gas-particle partitioning of multicomponent mixtures of relevance for atmospheric chemistry or in other scientific fields.

Zuend, A.; Marcolli, C.; Booth, A. M.; Lienhard, D. M.; Soonsin, V.; Krieger, U. K.; Topping, D. O.; McFiggans, G.; Peter, T.; Seinfeld, J. H.

2011-05-01

127

Comparison of activity coefficient models for atmospheric aerosols containing mixtures of electrolytes, organics, and water  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols generally comprise a mixture of electrolytes, organic compounds, and water. Determining the gas-particle distribution of volatile compounds, including water, requires equilibrium or mass transfer calculations, at the heart of which are models for the activity coefficients of the particle-phase components. We evaluate here the performance of four recent activity coefficient models developed for electrolyte/organic/water mixtures typical of atmospheric aerosols. Two of the models, the CSB model [Clegg, S.L., Seinfeld, J.H., Brimblecombe, P., 2001. Thermodynamic modelling of aqueous aerosols containing electrolytes and dissolved organic compounds. Journal of Aerosol Science 32, 713-738] and the aerosol diameter dependent equilibrium model (ADDEM) [Topping, D.O., McFiggans, G.B., Coe, H., 2005. A curved multi-component aerosol hygroscopicity model framework: part 2—including organic compounds. Atmospheric Chemistry and Physics 5, 1223-1242] treat ion-water and organic-water interactions but do not include ion-organic interactions; these can be referred to as "decoupled" models. The other two models, reparameterized Ming and Russell model 2005 [Raatikainen, T., Laaksonen, A., 2005. Application of several activity coefficient models to water-organic-electrolyte aerosols of atmospheric interest. Atmospheric Chemistry and Physics 5, 2475-2495] and X-UNIFAC.3 [Erdakos, G.B., Change, E.I., Pandow, J.F., Seinfeld, J.H., 2006. Prediction of activity coefficients in liquid aerosol particles containing organic compounds, dissolved inorganic salts, and water—Part 3: Organic compounds, water, and ionic constituents by consideration of short-, mid-, and long-range effects using X-UNIFAC.3. Atmospheric Environment 40, 6437-6452], include ion-organic interactions; these are referred to as "coupled" models. We address the question—Does the inclusion of a treatment of ion-organic interactions substantially improve the performance of the coupled models over that of the decoupled models? Performance is judged by the extent to which each model is able to reproduce experimental water activity data for mixtures of organic acids (malonic, succinic, glutaric, citric, maleic, and malic acids) and inorganic electrolytes (NaCl and (NH 4) 2SO 4). It is found, based on the comparisons reported here, that the decoupled models perform as well as, and in some cases better than, the coupled models. Since such activity coefficient models are likely to continue to be developed in the future and because we consider here only a limited set of organic compounds, the current study should be viewed as an interim assessment. The scarcity of experimental data for mixtures of atmospheric relevance remains a limitation for testing activity coefficient models.

Tong, Chinghang; Clegg, Simon L.; Seinfeld, John H.

128

Molecular radiotherapy: The NUKFIT software for calculating the time-integrated activity coefficient  

SciTech Connect

Purpose: Calculation of the time-integrated activity coefficient (residence time) is a crucial step in dosimetry for molecular radiotherapy. However, available software is deficient in that it is either not tailored for the use in molecular radiotherapy and/or does not include all required estimation methods. The aim of this work was therefore the development and programming of an algorithm which allows for an objective and reproducible determination of the time-integrated activity coefficient and its standard error.Methods: The algorithm includes the selection of a set of fitting functions from predefined sums of exponentials and the choice of an error model for the used data. To estimate the values of the adjustable parameters an objective function, depending on the data, the parameters of the error model, the fitting function and (if required and available) Bayesian information, is minimized. To increase reproducibility and user-friendliness the starting values are automatically determined using a combination of curve stripping and random search. Visual inspection, the coefficient of determination, the standard error of the fitted parameters, and the correlation matrix are provided to evaluate the quality of the fit. The functions which are most supported by the data are determined using the corrected Akaike information criterion. The time-integrated activity coefficient is estimated by analytically integrating the fitted functions. Its standard error is determined assuming Gaussian error propagation. The software was implemented using MATLAB.Results: To validate the proper implementation of the objective function and the fit functions, the results of NUKFIT and SAAM numerical, a commercially available software tool, were compared. The automatic search for starting values was successfully tested for reproducibility. The quality criteria applied in conjunction with the Akaike information criterion allowed the selection of suitable functions. Function fit parameters and their standard error estimated by using SAAM numerical and NUKFIT showed differences of <1%. The differences for the time-integrated activity coefficients were also <1% (standard error between 0.4% and 3%). In general, the application of the software is user-friendly and the results are mathematically correct and reproducible. An application of NUKFIT is presented for three different clinical examples.Conclusions: The software tool with its underlying methodology can be employed to objectively and reproducibly estimate the time integrated activity coefficient and its standard error for most time activity data in molecular radiotherapy.

Kletting, P.; Schimmel, S.; Luster, M. [Klinik für Nuklearmedizin, Universität Ulm, Ulm 89081 (Germany)] [Klinik für Nuklearmedizin, Universität Ulm, Ulm 89081 (Germany); Kestler, H. A. [Research Group Bioinformatics and Systems Biology, Institut für Neuroinformatik, Universität Ulm, Ulm 89081 (Germany)] [Research Group Bioinformatics and Systems Biology, Institut für Neuroinformatik, Universität Ulm, Ulm 89081 (Germany); Hänscheid, H.; Fernández, M.; Lassmann, M. [Klinik für Nuklearmedizin, Universität Würzburg, Würzburg 97080 (Germany)] [Klinik für Nuklearmedizin, Universität Würzburg, Würzburg 97080 (Germany); Bröer, J. H.; Nosske, D. [Bundesamt für Strahlenschutz, Fachbereich Strahlenschutz und Gesundheit, Oberschleißheim 85764 (Germany)] [Bundesamt für Strahlenschutz, Fachbereich Strahlenschutz und Gesundheit, Oberschleißheim 85764 (Germany); Glatting, G. [Medical Radiation Physics/Radiation Protection, Medical Faculty Mannheim, Heidelberg University, Mannheim 68167 (Germany)] [Medical Radiation Physics/Radiation Protection, Medical Faculty Mannheim, Heidelberg University, Mannheim 68167 (Germany)

2013-10-15

129

Liquid-phase adsorption of 1,1-dichloro-1-fluoroethane by various adsorbents  

SciTech Connect

Experiments have been conducted to examine the liquid-phase adsorption/desorption characteristics of 1,1-dichloro-1-fluoroethane (HCFC-141b) by activated alumina, molecular sieve, granular activated carbon (GAC), extruded activated carbon (EAC), and activated carbon fiber (ACF). HCFC-141b is currently regarded as an excellent replacement for CFC-11. The experimental results of adsorption and desorption were analyzed in terms of the equilibrium adsorption capacity, time to reach equilibrium, and desorption efficiency of the adsorbent and with an aim to assess the viability of the use of all adsorbents for possible HCFC-141b recovery. Adsorption isotherms of the Langmuir and Freundlich types were employed to examine the equilibrium adsorption data. A mass-transfer model based on the pseudo-steady-state driving force was adopted to describe the HCFC-141b adsorption process.

Lin, S.H.; Chen, Y.W. [Yuan Ze Inst. of Tech., Taoyuan (Taiwan, Province of China). Dept. of Chemical Engineering] [Yuan Ze Inst. of Tech., Taoyuan (Taiwan, Province of China). Dept. of Chemical Engineering

1997-10-01

130

Activity Coefficient Models to Describe Vapor-Liquid Equilibrium in Ternary Hydro-Alcoholic Solutions  

Microsoft Academic Search

In this study, three semipredictive activity coefficient models: Wilson, non-random-two liquid model (NRTL), and universal quasi-chemical model (UNIQUAC), have been used for modeling vapor-liquid equilibrium properties of ternary mixtures that include substances found in alcoholic distillation processes of wine and musts. In particular, vapor-liquid equilibrium in ternary mixtures containing water + ethanol + congener has been modeled using parameters obtained

Claudio A. Faúndez; José O. Valderrama

2009-01-01

131

Determination of Activity Coefficients of Semi-Volatile Organic Aerosols Using the Integrated Volume Method  

Microsoft Academic Search

We demonstrate the use of the Integrated Volume Method (IVM) to estimate activity coefficients of semi-volatile organic compounds pertinent to ambient\\/atmospheric aerosols in binary mixtures. We generate binary solution aerosols with different mole fractions of individual components; for each mixture, we measure total change in aerosol volume upon heating from 25C to 35C, with the aerosols being at equilibrium in

Rawad Saleh; Andrey Khlystov

2009-01-01

132

Optical absorption of liquid phase epitaxial garnet films at 1.3-µm wavelength for magneto-optic application  

Microsoft Academic Search

Optical absorption of liquid phase epitaxial magneto-optic Gd0.2Y2.8Fe5O12 films was measured at 1.3-?m wavelength using a waveguide technique. An optical absorption coefficient of ?=0.2 cm?1 at 1.3 ?m was obtained. This is the smallest value which has ever been reported for a garnet film and corresponds to 230 deg\\/dB in the figure of merit for Gd:YIG with the Faraday rotation

Taketoshi Hibiya; Junichiro Nakajima

1983-01-01

133

TiO 2 photocatalytic oxidation: I. Photocatalysts for liquid-phase and gas-phase processes and the photocatalytic degradation of chemical warfare agent simulants in a liquid phase  

Microsoft Academic Search

The results of studies on the effect of the preparation procedure on the properties of TiO2-based photocatalysts and the kinetics and mechanism of the photocatalytic oxidation of organic water pollutants are surveyed. The effects of calcination temperature, surface modification with platinum, and acid-base treatment of the surface of titanium dioxide on its activity in model gas-phase and liquid-phase reactions are

A. V. Vorontsov; D. V. Kozlov; P. G. Smirniotis; V. N. Parmon

2005-01-01

134

Morphologies of aerosol particles consisting of two liquid phases  

NASA Astrophysics Data System (ADS)

Recent studies have shown that liquid-liquid phase separation (LLPS) might be a common feature in mixed organic/ammonium sulfate (AS)/H2O particles. Song et al. (2012) observed that in atmospheric relevant organic/AS/H2O mixtures LLPS always occurred for organic aerosol compositions with O:C < 0.56, depended on the specific functional groups of organics in the range of 0.56 < O:C < 0.80 and never appeared for O:C > 0.80. The composition of the organic fraction and the mixing state of aerosol particles may influence deliquescence relative humidity (DRH) and efflorescence relative humidity (ERH) of inorganic salts during RH cycles and also aerosol morphology. In order to determine how the deliquescence and efflorescence of AS in mixed organic/AS/H2O particles is influenced by LLPS and to identify the corresponding morphologies of the particles, we subjected organic/AS/H2O particles deposited on a hydrophobically coated substrate to RH cycles and observed the phase transitions using optical microscopy and Raman spectroscopy. In this study, we report results from 21 organic/AS/H2O systems with O:C ranging from 0.55 - 0.85 covering aliphatic and aromatic oxidized compounds. Eight systems did not show LLPS for all investigated organic-to-inorganic ratios, nine showed core-shell morphology when present in a two-liquid-phases state and four showed both, core-shell or partially engulfed configurations depending on the organic-to-inorganic ratio. While AS in aerosol particles with complete LLPS showed almost constant values of ERH = 44 ± 4 % and DRH = 77 ± 2 %, a strong reduction or complete inhibition of efflorescence occurred for mixtures that did not exhibit LLPS. To confirm these findings, we performed supplementary experiments on levitated particles in an electrodynamic balance and compared surface and interfacial tensions of the investigated mixtures. Reference Song, M., C. Marcolli, U. K. Krieger, A. Zuend, and T. Peter (2012), Liquid-liquid phase separation in aerosol particles: Dependence on O:C, organic functionalities, and compositional complexity, Geophys. Res. Lett., 39doi:10.1029/2012GL052807.

Song, Mijung; Marcolli, Claudia; Krieger, Ulrich; Peter, Thomas

2013-04-01

135

Kinetics of the liquid-phase synthesis of ethyl tert-butyl ether (ETBE)  

SciTech Connect

The liquid-phase addition of ethanol to isobutene to give ethyl tert-butyl ether (ETBE) on the ion exchange resin Lewatit K2631 has been studied. Rate data were obtained free of mass transfer influence in a continuous differential reactor operated at 1.6 MPa and 40--90 C, measuring steady-state conversions <10% for ethanol-isobutene and ethanol-isobutene-ETBE feeds. The reaction is highly temperature-sensitive. Isobutene has an enhancing effect on the rate whereas ethanol has an inhibitor one. Besides, low ETBE concentrations enhance the reaction but as chemical equilibrium is approached the ether shows an inhibitor effect, as expected. As alcohol-olefin-ether mixtures behave nonideally, kinetic analysis has been performed by using the UNIFAC liquid-phase activities of isobutene, ethanol, and ETBE. The best kinetic model stems from an Eley-Rideal mechanism in which the ethanol, adsorbed on one center, reacts with the isobutene from solution to give the ether adsorbed on one center. Surface reaction is the rate-limiting step. Two additional centers take part in this step.

Fite, C.; Iborra, M.; Tejero, J.; Izquierdo, J.F.; Cunill, F. (Univ. of Barcelona (Spain). Chemical Engineering Dept.)

1994-03-01

136

Liquid-phase broadband cavity-enhanced absorption spectroscopy measurements in a 2 mm cuvette.  

PubMed

A novel implementation of broadband cavity enhanced absorption spectroscopy (BBCEAS) has been used to perform sensitive visible wavelength measurements on liquid-phase solutions in a 2 mm cuvette placed at normal incidence to the cavity mirrors. The overall experimental methodology was simple, low cost, and similar to conventional ultraviolet-visible absorption spectroscopy. The cavity was formed by two concave high reflectivity mirrors. Three mirror sets with nominal reflectivities (R) of R = 0.99, 0.9945, and 0.999 were used. The light source consisted of a high intensity red, green, blue, or white LED. The detector was a compact charge-coupled device (CCD) spectrograph. Measurements were made on the representative analytes, Ho(3+), and the dyes brilliant blue-R, sudan black, and coumarin 334 in appropriate solvents. Cavity enhancement factors (CEF) of up to 104 passes for the high reflectivity mirrors were obtained. The number of passes was limited by relatively high scattering and absorption losses in the cavity, of approximately 1 x 10(-2) per pass. Measurements over a wide wavelength range (420-670 nm) were also obtained in a single experiment with the white LED and the R = 0.99 mirror set for Ho(3+) and sudan black. The sensitivity of the experimental setup could be determined by calculating the minimum detectable change in the absorption coefficient alpha(min). The values ranged from 5.1 x 10(-5) to 1.2 x 10(-3) cm(-1). The limit of detection (LOD) for the strong absorber brilliant blue-R was 620 pM. A linear dynamic range of measurements of concentration over about two orders of magnitude was demonstrated. The overall sensitivity of the experimental setup compared very favorably with previous generally more experimentally complex and expensive liquid-phase cavity studies. Possible improvements to the technique and its applicability as an analytical tool are discussed. PMID:17650378

Islam, Meez; Seetohul, L Nitin; Ali, Zulfiqur

2007-06-01

137

Predicting the Activity Coefficients of Free-Solvent for Concentrated Globular Protein Solutions Using Independently Determined Physical Parameters  

PubMed Central

The activity coefficient is largely considered an empirical parameter that was traditionally introduced to correct the non-ideality observed in thermodynamic systems such as osmotic pressure. Here, the activity coefficient of free-solvent is related to physically realistic parameters and a mathematical expression is developed to directly predict the activity coefficients of free-solvent, for aqueous protein solutions up to near-saturation concentrations. The model is based on the free-solvent model, which has previously been shown to provide excellent prediction of the osmotic pressure of concentrated and crowded globular proteins in aqueous solutions up to near-saturation concentrations. Thus, this model uses only the independently determined, physically realizable quantities: mole fraction, solvent accessible surface area, and ion binding, in its prediction. Predictions are presented for the activity coefficients of free-solvent for near-saturated protein solutions containing either bovine serum albumin or hemoglobin. As a verification step, the predictability of the model for the activity coefficient of sucrose solutions was evaluated. The predicted activity coefficients of free-solvent are compared to the calculated activity coefficients of free-solvent based on osmotic pressure data. It is observed that the predicted activity coefficients are increasingly dependent on the solute-solvent parameters as the protein concentration increases to near-saturation concentrations.

McBride, Devin W.; Rodgers, Victor G. J.

2013-01-01

138

Liquid-phase epitaxy of lead-doped indium antimonide  

SciTech Connect

Indium antimonide was doped with lead under liquid-phase epitaxial (LPE) conditions, permitting the composition of the starting phase and the temperature of the process to be varied within wide limits. To obtain the maximum solubility of lead at any chosen LPE temperature it was used as a metallic solvent. It was found that the solubility of lead in indium antimonide at 450-350/sup 0/C does not exceed 0.07 wt. %. Introduction of Pb does not change the dislocation density substantially in the layers grown. From the results of electrophysical investigations it follows that lead dissolves in indium antimonide upon crystallization from lead solution-melts, predominantly substituting for the indium atoms.

Akchurin, R.Kh.; Kovalevskii, N.D.

1986-12-01

139

Liquid Phase Stability Under an Extreme Temperature Gradient  

NASA Astrophysics Data System (ADS)

Using nonequilibrium molecular dynamics simulations, we subject bulk liquid to a very high-temperature gradient and observe a stable liquid phase with a local temperature well above the boiling point. Also, under this high-temperature gradient, the vapor phase exhibits condensation into a liquid at a temperature higher than the saturation temperature, indicating that the observed liquid stability is not caused by nucleation barrier kinetics. We show that, assuming local thermal equilibrium, the phase change can be understood from the thermodynamic analysis. The observed elevation of the boiling point is associated with the interplay between the “bulk” driving force for the phase change and surface tension of the liquid-vapor interface that suppresses the transformation. This phenomenon is analogous to that observed for liquids in confined geometries. In our study, however, a low-temperature liquid, rather than a solid, confines the high-temperature liquid.

Liang, Zhi; Sasikumar, Kiran; Keblinski, Pawel

2013-11-01

140

Liquid phase stability under an extreme temperature gradient.  

PubMed

Using nonequilibrium molecular dynamics simulations, we subject bulk liquid to a very high-temperature gradient and observe a stable liquid phase with a local temperature well above the boiling point. Also, under this high-temperature gradient, the vapor phase exhibits condensation into a liquid at a temperature higher than the saturation temperature, indicating that the observed liquid stability is not caused by nucleation barrier kinetics. We show that, assuming local thermal equilibrium, the phase change can be understood from the thermodynamic analysis. The observed elevation of the boiling point is associated with the interplay between the "bulk" driving force for the phase change and surface tension of the liquid-vapor interface that suppresses the transformation. This phenomenon is analogous to that observed for liquids in confined geometries. In our study, however, a low-temperature liquid, rather than a solid, confines the high-temperature liquid. PMID:24329454

Liang, Zhi; Sasikumar, Kiran; Keblinski, Pawel

2013-11-27

141

Mass transfer rate measurement of short time liquid phase epitaxial growth using an electrochemical method  

Microsoft Academic Search

Convective mass transfer phenomena become significant in sub-micrometre liquid phase epitaxial layer growth. An aqueous solution containing 0.01m K3Fe(CN)6+0.01m K4Fe(CN)6+1.0m KOH in a Plexiglass vessel was used to simulate the fluid motion and mass transfer condition in liquid phase epitaxy. The mass transfer phenomena between the liquid phase epitaxial system and electrochemical system at mass transfer limiting condition are equivalent.

Lai-Juh Chen; Kan-Lin Hsueh; Chi-Chao Wan; J. Gong

1991-01-01

142

Improved estimation of solubility and partitioning through correction of UNIFAC-derived activity coefficients  

SciTech Connect

Octanol-water partition coefficients (K/sub ow/) of 75 compounds ranging over 9 orders of magnitude are correlated by log K/sub ow/ = -0.40 + 0.73 log (..gamma../sub W/)/sub U/ -0.39 log (..gamma../sub 0/)/sub U/ (r = 0.98), where (..gamma..//sub W/)/sub U/ and (..gamma../sub 0/)/sub U/ are UNIFAC-derived activity coefficients in water and octanol, respectively. The constants 0.73 and -0.39 are obtained empirically and are intended to compensate for group nonadditivity. Correction factors of similar magnitude are obtained in independent correlations of water solubility with (..gamma../sub W/)/sub U/ and of octanol solubility with (..gamma../sub 0/)/sub U/, thereby confirming the validity of the approach.

Banerjee, S.; Howard, P.H.

1988-07-01

143

Prediction Expressions of Component Activity Coefficients in Si-Based Melts  

NASA Astrophysics Data System (ADS)

Prediction expressions of component activity coefficients of the molecular interaction volume model (MIVM) are suggested for making up for absence of Wagner interaction parameters in Si-based melts. Their effectiveness is verified in liquid Fe-Si-B system at 1823 K (1550 °C). In comparison with experimental data, all errors of ±22 to 56 pct and deviations of ±0.0132 to 0.0318 predicted by MIVM are smaller than those (±53 to 94 pct and ±0.0759 to 0.1010) by the unified interaction parameter formalism. This indicates that the former is better than the later in the system. Accordingly, some interested thermodynamic diagrams and parameters at 1687 K and 1823 K (1414 °C and 1550 °C) are predicted in liquid Si-Al-Fe system, for instance, \\varepsilon_{{Al}}^{{Al}} = 2.318, \\varepsilon_{{Fe}}^{{Fe}} = 4.297, and \\varepsilon_{{Fe}}^{{Al}} = \\varepsilon_{{Al}}^{{Fe}} = - 2.443 in the dilute solution at 1687 K (1414 °C). The method of MIVM is able to expand to Si-based multicomponent melt if its sub-binary activity data are available. The reliability of predicted results for the melt is closely dependent upon that of component activities or infinite dilute activity coefficients in its sub-binary systems.

Tao, Dong-Ping

2013-10-01

144

Kinetic and thermodynamic study of the liquid-phase etherification of isoamylenes with methanol  

SciTech Connect

The kinetics and thermodynamics of liquid-phase etherification of isoamylenes with methanol on ion exchange catalyst (Amberlyst 15) were studied. Thermodynamic properties and rate data were obtained in a batch reactor operating under 1,013 kPa and 323--353 K. The kinetic equation was modeled following the Langmuir-Hinshelwood-Hougen-Watson formalism according to a proposed surface mechanism where the rate-controlling step is the surface reaction. According to the experimental results, methanol adsorbs very strongly on the active sites, covering them completely, and thus the reaction follows an apparent first-order behavior. The isoamylenes, according to the proposed mechanism, adsorb simultaneously on the same single active center already occupied by methanol, migrating through the liquid layer formed by the alcohol around the catalyst to react in the acidic site. From the proposed mechanism a model was suggested and the kinetic and thermodynamic parameters were obtained using nonlinear estimation methods.

Piccoli, R.L. (Copesul-Cia Petroquimica do Sul, Triunfo (Brazil)); Lovisi, H.R. (Petroflex-Ind. e Comercio, Duque de Caxias (Brazil))

1995-02-01

145

Particle drag coefficients in turbulent fluids  

Microsoft Academic Search

An accurate estimation of particle settling velocities, and\\/or of particle drag coefficients, is required for modelling purposes in many industrially important multiphase processes involving the suspension of millimetre and sub-millimetre size particles in a liquid phase. It is known that the settling velocity of particles in a turbulent fluid may be significantly different from that in the still fluid, depending

A. Brucato; F. Grisafi; G. Montante

1998-01-01

146

Predicting passive and active tissue:plasma partition coefficients: interindividual and interspecies variability.  

PubMed

A mechanistic tissue composition model incorporating passive and active transport for the prediction of steady-state tissue:plasma partition coefficients (Kt:pl ) of chemicals in multiple mammalian species was used to assess interindividual and interspecies variability. This approach predicts Kt:pl using chemical lipophilicity, pKa , phospholipid membrane binding, and the unbound plasma fraction, together with tissue fractions of water, neutral lipids, neutral and acidic phospholipids, proteins, and pH. Active transport Kt:pl is predicted using Michaelis-Menten transport parameters. Species-specific biological properties were identified from 126 peer reviewed journal articles, listed in the Supporting Information, for mouse, rat, guinea pig, rabbit, beagle dog, pig, monkey, and human species. Means and coefficients of variation for biological properties were used in a Monte Carlo analysis to assess variability. The results show Kt:pl interspecies variability for the brain, fat, heart, kidney, liver, lung, muscle, red blood cell, skin, and spleen, but uncertainty in the estimates obscured some differences. Compounds undergoing active transport are shown to have concentration-dependent Kt:pl . This tissue composition-based mechanistic model can be used to predict Kt:pl for organic chemicals across eight species and 10 tissues, and can be an important component in drug development when scaling Kt:pl from animal models to humans. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:2189-2198, 2014. PMID:24832575

Ruark, Christopher D; Hack, C Eric; Robinson, Peter J; Mahle, Deirdre A; Gearhart, Jeffery M

2014-07-01

147

Activity of Water and Osmotic Coefficients of Histidine Derivatives in Aqueous Solutions at 310.15 K  

Microsoft Academic Search

From the data of vapor pressure osmometry the activity of water, osmotic coefficients, and the values of activity coefficients\\u000a of two derivatives of histidine: N-Boc-L-histidine (Boc-His-OH, m=0.005–0.14 mol?kg?1) and N-Boc-L-histidine-methyl ether (Boc-His-OMe, m=0.005–0.05 mol?kg?1) are obtained in aqueous solutions at 310.15 K. From the comparison of water activity and osmotic coefficient values it follows\\u000a that Boc-His-OMe shows a more pronounced deviation from

Elena N. Tsurko; Roland Neueder; Werner Kunz

2008-01-01

148

Glass and liquid phase diagram of a polyamorphic monatomic system.  

PubMed

We perform out-of-equilibrium molecular dynamics (MD) simulations of a monatomic system with Fermi-Jagla (FJ) pair potential interactions. This model system exhibits polyamorphism both in the liquid and glass state. The two liquids, low-density (LDL) and high-density liquid (HDL), are accessible in equilibrium MD simulations and can form two glasses, low-density (LDA) and high-density amorphous (HDA) solid, upon isobaric cooling. The FJ model exhibits many of the anomalous properties observed in water and other polyamorphic liquids and thus, it is an excellent model system to explore qualitatively the thermodynamic properties of such substances. The liquid phase behavior of the FJ model system has been previously characterized. In this work, we focus on the glass behavior of the FJ system. Specifically, we perform systematic isothermal compression and decompression simulations of LDA and HDA at different temperatures and determine "phase diagrams" for the glass state; these phase diagrams varying with the compression/decompression rate used. We obtain the LDA-to-HDA and HDA-to-LDA transition pressure loci, P(LDA-HDA)(T) and P(HDA-LDA)(T), respectively. In addition, the compression-induced amorphization line, at which the low-pressure crystal (LPC) transforms to HDA, P(LPC-HDA)(T), is determined. As originally proposed by Poole et al. [Phys. Rev. E 48, 4605 (1993)] simulations suggest that the P(LDA-HDA)(T) and P(HDA-LDA)(T) loci are extensions of the LDL-to-HDL and HDL-to-LDL spinodal lines into the glass domain. Interestingly, our simulations indicate that the P(LPC-HDA)(T) locus is an extension, into the glass domain, of the LPC metastability limit relative to the liquid. We discuss the effects of compression/decompression rates on the behavior of the P(LDA-HDA)(T), P(HDA-LDA)(T), P(LPC-HDA)(T) loci. The competition between glass polyamorphism and crystallization is also addressed. At our "fast rate," crystallization can be partially suppressed and the glass phase diagram can be related directly with the liquid phase diagram. However, at our "slow rate," crystallization cannot be prevented at intermediate temperatures, within the glass region. In these cases, multiple crystal-crystal transformations are found upon compression/decompression (polymorphism). PMID:23425481

Reisman, Shaina; Giovambattista, Nicolas

2013-02-14

149

A model for liquid phase electroepitaxy under an external magnetic field I. Theory  

Microsoft Academic Search

A continuum model for the liquid phase electroepitaxial (LPEE) growth process is presented. In the model the growth cell is assumed to be under the effect of an intentionally applied external magnetic field in order to reduce the effect of natural convection induced by the temperature and solute concentration gradients in the liquid phase. The fundamental equations are obtained from

S. Dost; Z. Qin

1995-01-01

150

Statistical thermodynamics of liquid-liquid phase separation in ternary systems during complex coacervation  

Microsoft Academic Search

Liquid-liquid phase separation leading to complex coacervation in a ternary system (oppositely charged polyion and macroion in a solvent) is discussed within the framework of a statistical thermodynamics model. The polyion and the macroion in the ternary system interact to form soluble aggregates (complexes) in the solvent, which undergoes liquid-liquid phase separation. Four necessary conditions are shown to drive the

Nisha Pawar; H. B. Bohidar

2010-01-01

151

Effective liquid-phase methanol synthesis utilizing liquid-liquid separation  

Microsoft Academic Search

New liquid phase methanol synthesis process is proposed in that methanol is ejected with hydrocarbon solvent exclusively as a liquid phase, while gaseous components are not practically discharged from the reactor. Methanol is obtained in 95% yield with trace amount of feed gas by liquid-liquid separation from hydrophobic solvent. The advantage of the present process is that the gas recycle

K. Hagihara; H. Mabuse; T. Watanabe; M. Kawai; M. Saito

1995-01-01

152

Thermochemical analysis of the silicon carbide-alumina reaction with reference to liquid-phase sintering of silicon carbide  

NASA Technical Reports Server (NTRS)

The stabilities of different phases in the Si-Al-C-O system are calculated from thermodynamic considerations with the objective of identifying the liquid phases formed during sintering of SiC in the presence of Al2O3. It is shown that a liquid phase can form at the sintering temperatures by the reaction of SiC with Al2O3. Depending on the carbon activity, the liquid can be either of the following: Al2O3 + Al4C3, SiC + Al4C3, or molten aluminum. The stability of the aluminosilicate melts that can form by the reaction of Al2O3 with the surface silica layer on SiC powders is also evaluated. Several factors that influence liquid-phase sintering, such as the solubility of SiC in the melts and the generation of gases during sintering, are discussed. The results of the thermodynamic analysis are compared with the observed sintering behavior for SiC.

Misra, Ajay K.

1991-01-01

153

On the mechanisms of micropipe and macrodefect transformation in SiC during liquid phase treatment  

NASA Astrophysics Data System (ADS)

The evolution of hollow-core defects present in vapor phase grown SiC bulk crystals during subsequent liquid phase epitaxial treatment has been investigated in a wide range of supersaturation conditions. Hollow macrodefects were found to decompose into a number of micropipes (MP) already at supersaturations close to zero. The elimination of pure screw-dislocation based MP requires a higher supersaturation. Micropipes were observed to dissociate into individually acting non-hollow core dislocations. After decomposition the activity of growth center based on a MP is usually reduced and a new center may dominate the growing surface. A model for the mechanism of MP transformation is proposed which is based on BCF theory and Chernovs theory of morphological stability.

Epelbaum, B. M.; Hofmann, D.

2001-05-01

154

A novel series of isoreticular metal organic frameworks: realizing metastable structures by liquid phase epitaxy  

PubMed Central

A novel class of metal organic frameworks (MOFs) has been synthesized from Cu-acetate and dicarboxylic acids using liquid phase epitaxy. The SURMOF-2 isoreticular series exhibits P4 symmetry, for the longest linker a channel-size of 3 × 3?nm2 is obtained, one of the largest values reported for any MOF so far. High quality, ab-initio electronic structure calculations confirm the stability of a regular packing of (Cu++)2- carboxylate paddle-wheel planes with P4 symmetry and reveal, that the SURMOF-2 structures are in fact metastable, with a fairly large activation barrier for the transition to the bulk MOF-2 structures exhibiting a lower, twofold (P2 or C2) symmetry. The theoretical calculations also allow identifying the mechanism for the low-temperature epitaxial growth process and to explain, why a synthesis of this highly interesting, new class of high-symmetry, metastable MOFs is not possible using the conventional solvothermal process.

Liu, Jinxuan; Lukose, Binit; Shekhah, Osama; Arslan, Hasan Kemal; Weidler, Peter; Gliemann, Hartmut; Brase, Stefan; Grosjean, Sylvain; Godt, Adelheid; Feng, Xinliang; Mullen, Klaus; Magdau, Ioan-Bogdan; Heine, Thomas; Woll, Christof

2012-01-01

155

Grain growth kinetics in liquid-phase-sintered zinc oxide-barium oxide ceramics  

NASA Technical Reports Server (NTRS)

Grain growth of ZnO in the presence of a liquid phase of the ZnO-BaO system has been studied for temperatures from 1300 to 1400 C. The specimens were treated in boiling water and the grains were separated by dissolving the matrix phase in an ultrasonic bath. As a consequence 3D grain size measurements were possible. Microstructural examination shows some grain coalescence with a wide range of neck size ratios and corresponding dihedral angles, however, most grains are isolated. Lognormal grain size distributions show similar shapes, indicating that the growth mechanism is invariant over this time and temperature. All regressions between G exp n and time for n = 2 and 3 proved statistically significant. The rate constants calculated with the growth exponent set to n = 3 are on the same order of magnitude as in metallic systems. The apparent activation energy for growth is estimated between 355 and 458 kJ/mol.

Yang, Sung-Chul; German, Randall M.

1991-01-01

156

A novel series of isoreticular metal organic frameworks: realizing metastable structures by liquid phase epitaxy  

NASA Astrophysics Data System (ADS)

A novel class of metal organic frameworks (MOFs) has been synthesized from Cu-acetate and dicarboxylic acids using liquid phase epitaxy. The SURMOF-2 isoreticular series exhibits P4 symmetry, for the longest linker a channel-size of 3 × 3 nm2 is obtained, one of the largest values reported for any MOF so far. High quality, ab-initio electronic structure calculations confirm the stability of a regular packing of (Cu++)2- carboxylate paddle-wheel planes with P4 symmetry and reveal, that the SURMOF-2 structures are in fact metastable, with a fairly large activation barrier for the transition to the bulk MOF-2 structures exhibiting a lower, twofold (P2 or C2) symmetry. The theoretical calculations also allow identifying the mechanism for the low-temperature epitaxial growth process and to explain, why a synthesis of this highly interesting, new class of high-symmetry, metastable MOFs is not possible using the conventional solvothermal process.

Liu, Jinxuan; Lukose, Binit; Shekhah, Osama; Arslan, Hasan Kemal; Weidler, Peter; Gliemann, Hartmut; Bräse, Stefan; Grosjean, Sylvain; Godt, Adelheid; Feng, Xinliang; Müllen, Klaus; Magdau, Ioan-Bogdan; Heine, Thomas; Wöll, Christof

2012-12-01

157

Activity coefficient of titanium in iron-based melts under nitride formation/dissolution conditions  

NASA Astrophysics Data System (ADS)

The initial parameters for calculating the activity coefficients of titanium in complex iron-based melts are determined. For this purpose, multiple regression analysis of 311 experimental results obtained by independent researchers is used. As a result, the initial parameters for calculating the activity coefficients of titanium (?{Ti,1873/?} = 0.059, its temperature dependence log?{Ti/?} = -14900/ T + 6.73) and the temperature dependences of interaction parameters e {Ti/ j } and r {Ti/ j } are refined. The found value of ?{Ti,1873/?} agrees with the results of a number of earlier investigations and is significantly higher than the values recommended in the most widely used handbooks. The application of the found parameters for calculating the nitrogen concentrations in equilibrium with TiN in the melts decreases the mean deviation of the calculated data from the experimental results to a level of at most ±13%, which is much better than in the case of using the data from the most widely used handbooks.

Stomakhin, A. Ya.; Lysenkova, E. V.

2013-11-01

158

Preparation of carbon blacks by liquid phase plasma (LPP) process.  

PubMed

In this study, carbon black nanoparticles were synthesized by Liquid Phase Plasma (LPP) technique; plasma generated in the organic solvent of benzene at 4.9 kV with the pulse frequency of 15 kHz and width of 5 micros transformed the carbon atoms in the solvent into carbon blacks by oxidation and reduction reactions. Graphite phase was found to be introduced into the carbon blacks without any additional processes due to the characteristics of LPP process, resulting in a higher G/D ratio of 0.92, compared to 0.83 of commercial Ketjen carbon blacks. For the performance improvement, heat treatment was employed and its parameters such as temperature and duration time were optimized in relation to the crystallinity and specific surface area of the carbon blacks. Carbon blacks heat treated at 450 degrees C in the air for 20 min were measured to have the discharge capacity of 1750 mAh/g and irreversible charging and discharging capacity ratio of 52.6%. PMID:24245259

Yun, Kang-Seop; Kim, Bo-Ra; Kang, Woo-Seung; Jung, Sang-Chul; Myung, Seung-Taek; Kim, Sun-Jae

2013-11-01

159

Self-Sputtering of Solid and Liquid Phase Tin  

NASA Astrophysics Data System (ADS)

The absolute self-sputtering yields of solid and liquid-phase Sn have been measured for incident ions with energies of 300 to 1000 eV at 45^o using the Ion-surface InterAction eXperiment (IIAX). A Sn divertor^1 would experience self-bombardment from redepositing Sn ions, and its use may be limited by a temperature-enhanced self-sputtering yield. Thus, an understanding of any temperature dependence is a key to predictive modeling of such a device. IIAX uses a Colutron^2 ion source to produce a velocity-filtered Sn^+ beam for sample irradiation. Experiments were carried out with sample temperatures ranging from room temperature to 380^oC. A quartz-crystal microbalance (QCM) monitors sputtering by direct collection of ejected and reflected material; background noise is removed using a reference crystal. VFTRIM^3, which cannot simulate temperature, was used for comparison to recorded data and for data analysis. Hybrid Molecular-Dynamic/Monte Carlo simulations which include temperature effects^4 were also investigated. [1] Brooks, J.N. Fus. Eng. Des. 60 (2002) 515-526. [2] Menzinger, M. and Wahlin, L. Rev. Sci. Instrum. 40 (1969) 102-105. [3] Ruzic, D.N. Nuc. Instrum. Meth. Phys. Res. 47 (1990) 118-125. [4] Allain, J.P., D.N. Ruzic, submitted to Nuc. Instrum. Meth. B, January 2004

Coventry, M. D.; Tomchik, C. A.; Ruzic, D. N.

2004-11-01

160

Synthesis of methanol in a methanol-rich liquid phase  

SciTech Connect

A novel method for synthesizing methanol from CO and H{sub 2} in a slurry reactor is described and experimental results are presented. At the temperatures and pressures used (100-160{degree}C, 50 atm) the methanol product is liquid and constitutes the bulk of the liquid phase. Small amounts of methyl formate (4 to 5%) and other products (less than 1% total) are formed. A heterogeneous catalyst (copper chromite) and a homogeneous catalyst (an alkali salt) are used in a single reactor. It appears likely that the reaction proceeds in two steps - carbonylation of methanol to methyl formate and then hydrogenation of the formate to two moles of methanol. Experiments were carried out in a 300 ml autoclave with continuous gas feed and intermittent liquid withdrawal. In situ reduction of the copper chromite was found to be as effective as external reduction and was used in all runs. A barium-promoted copper chromite showed substantially less deactivation than a manganese promoted one. Of six homogeneous catalysts tested the most effective was potassium methoxide, although some reaction occurred with all the homogeneous catalysts used. The rate of reaction was found to vary with gas feed rate - an unexpected result. It is proposed that this is due to the presence of small amounts of an inhibiting agent which accumulates in the liquid at low flow rates. 7 refs., 2 tabs.

Liu, Z.; Palekar, V.; Tierney, J.W.; Wender, I.; Shah, Y.T.

1990-07-09

161

Liquid-phase compositions from vapor-phase analyses  

SciTech Connect

In the safe handling and processing of uranium hexafluoride (UF{sub 6}), it is often desirable to calculate vapor composition and pressure from known liquid composition and temperature. Furthermore, the ability to use analyses of equilibrium vapor-phase samples to calculate liquid-phase compositions would be economically advantageous to the International Atomic Energy Agency (IAEA) in its international safeguards program and to uranium enrichment operators. The latter technique is projected to save the IAEA on the order of $1500 or more per sample. Either type of calculation could be performed with a multicomponent vapor-liquid equilibrium (VLE) model if this model were shown to apply to UF{sub 6} and its common impurities. This report is concerned with the distribution of four potential impurities in UF{sub 6} between liquid and vapor phases. The impurities are carbon dioxide, sulfur hexafluoride, chloryl fluoride, and Freon-114 (CClF{sub 2}CClF{sub 2}). There are no binary equilibrium data on the first three of these impurities; hence, the VLE calculations are based entirely on the thermodynamic properties of the pure components. There are two sets of binary equilibrium data for the system Freon-114-UF{sub 6} that are analyzed in terms of the model of Prausnitz et al. Calculations based on these data are compared with those based solely on the thermodynamic properties of pure Freon-114 and pure UF{sub 6}. 23 refs., 3 figs., 5 tabs.

Davis, W. Jr.; Cochran, H.D.; Leitnaker, J.M.

1989-09-01

162

Liquid phase deposition synthesis of hexagonal molybdenum trioxide thin films  

SciTech Connect

Hexagonal molybdenum trioxide thin films with good crystallinity and high purity have been fabricated by the liquid phase deposition (LPD) technique using molybdic acid (H{sub 2}MoO{sub 4}) dissolved in 2.82% hydrofluoric acid (HF) and H{sub 3}BO{sub 3} as precursors. The crystal was found to belong to a hexagonal hydrate system MoO{sub 3}.nH{sub 2}O (napprox0.56). The unit cell lattice parameters are a=10.651 A, c=3.725 A and V=365.997 A{sup 3}. Scanning electron microscope (SEM) images of the as-deposited samples showed well-shaped hexagonal rods nuclei that grew and where the amount increased with increase in reaction time. X-ray photon electron spectroscopy (XPS) spectra showed a Gaussian shape of the doublet of Mo 3d core level, indicating the presence of Mo{sup 6+} oxidation state in the deposited films. The deposited films exhibited an electrochromic behavior by lithium intercalation and deintercalation, which resulted in coloration and bleaching of the film. Upon dehydration at about 450 deg. C, the hexagonal MoO{sub 3}.nH{sub 2}O was transformed into the thermodynamically stable orthorhombic phase. - Abstract: SEM photograph of typical h-MoO{sub 3}.nH{sub 2}O thin film nuclei obtained after 36 h at 40 deg. C by the LPD method. Display Omitted

Deki, Shigehito; Beleke, Alexis Bienvenu; Kotani, Yuki [Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokko, Nada, Kobe 657-8501 (Japan); Mizuhata, Minoru, E-mail: mizuhata@kobe-u.ac.j [Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokko, Nada, Kobe 657-8501 (Japan)

2009-09-15

163

Gas-liquid chromatography with a volatile "stationary" liquid phase.  

PubMed

A unique type of gas-liquid chromatography is described in which both mobile and "stationary" phases are composed of synthetic mixtures of helium and carbon dioxide. At temperatures below the critical point of the binary mixture and pressures above the vapor pressure of pure liquid carbon dioxide, helium and carbon dioxide can form two immiscible phases over extended composition ranges. A binary vapor phase enriched in helium can act as the mobile phase for chromatographic separations, whereas a CO2-rich liquid in equilibrium with the vapor phase, but condensed on the column wall, can act as a pseudostationary phase. Several examples of chromatographic separations obtained in "empty" capillary columns with no ordinary stationary liquid phase illustrate the range of conditions that produce such separations. In addition, several experiments are reported that confirm the proposed two-phase hypothesis. The possible consequences of the observed chromatographic phenomenon in the field of supercritical fluid chromatography with helium headspace carbon dioxide are discussed. PMID:12033313

Wells, P S; Zhou, S; Parcher, J F

2002-05-01

164

Thermal conductivity of alternative refrigerants in the liquid phase  

SciTech Connect

Measurements of the thermal conductivity of five alternative refrigerants, namely, difluoromethane (HFC-32), pentafluoroethane (HFC-125), 1,1,1-trifluorethane (HFC-143a), and dichloropentafluoropropanes (HCFC-225ca and HCFC-225cb), are carried out in the liquid phase. The range of temperature is 253-324 K for HFC-32, 257-305 K for HFC-125, 268-314 K for HFC-134a, 267-325 K for HCF-225ca, and 286-345 K for HCFC-225cb. The pressure range is from saturation to 30 MPa. The reproducibility of the data is better than 0.5%, and the accuracy of the data is estimated to be of the order of 1%. The experimental results for the thermal conductivity of each substance are correlated by an equation which is a function of temperature and pressure. A short discussion is given to the comparison of the present results with literature values for HFC-125. The saturated liquid thermal conductivity values of HFC-32, HFC-125, and HFC-143a are compared with those of chlorodifluoromethane (HCFC-22) and tetrafluoroethane (HFC-134a) and it is shown that the value of HFC-32 is highest, while that of HFC-125 is lowest, among these substances. The dependence of thermal conductivity on number of fluorine atoms among the refrigerants with the same number of carbon and hydrogen atoms is discussed.

Yata, J.; Hori, M. [Kyoto Inst. of Technology (Japan); Kobayashi, K. [Kobe Steel Co., Ltd. (Japan); Minamiyama, T. [Fukyuama Univ. (Japan)

1996-05-01

165

Thermal conductivity of alternative refrigerants in the liquid phase  

NASA Astrophysics Data System (ADS)

Measurements ofthe thermal conductivity of five alternative refrigerants. namely, difluoromethane HFC-321. pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichloropentafluoropropanes (HCFC-225ca and HCFC-225cb). are carried out in the liquid phase, The range of temperature is 253 324 K for HFC-32, 257 305 K for HFC-125, 268 314 K for HFC-134a. 267 325 K for HCFC-225ca, and 286 345 K for HCFC-225cb, The pressure rank is from saturation to 30 MPa, The reproducibility of the data is better than 0.5% and the accuracy of the data is estimated to be of the order of 1%. The experimental results for the thermal conductivity ofeach substance are correlated by an equation which is a function of temperature and pressure. A short discussion is given to the comparison of the present results with literature values for HFC-125, The saturated liquid thermal conductivity values of HFC-32. HFC-125, and HFC-143a are compared with those of chlorodifluoromethane (HCFC-22) and tetrafluoroethane (HFC-134a) and it is shown that the value of HFC-32 is highest, while that of HFC-125 is lowest, among these substances, The dependence of thermal conductivity on number of fluorine atoms among the refrigerants with the same number of carbon and hydrogen atoms is discussed.

Yata, J.; Hori, M.; Kobayashi, K.; Minamiyama, T.

1996-05-01

166

[Influence of human activities on groundwater environment based on coefficient variation method].  

PubMed

Groundwater system in the plain area of Beijing can be divided into six subsystems. Due to the different hydrogeological conditions of the subsystems, the degrees to which human activities affect the subsystems are also diverse. In order to evaluate the influence of human activities on each subsystem, the first and second aquifer with relatively poor water quality were chosen to be the evaluating positions, based on the data of groundwater sampled in September, 2011. With respect to human activities affect index such as total hardness, TDS, sulfate and ammonium, variation coefficient methods were used to calculate the weight of each index. Then scores were obtained for each index with national standard as reference, and superposition calculations were used to gain comprehensive scores, finally the groundwater quality conditions were evaluated. Contrast analyses were used to evaluate the incidence of human activities with groundwater subsystems as evaluation unit and water quality partitions as evaluation factors. The results indicate that the influence of human activities on the first aquifer is greater than that of the second aquifer, the Yongding river groundwater subsystems and the Chaobai river groundwater subsystems are affected more than other groundwater subsystems. PMID:23798103

Zhao, Wei; Lin, Jian; Wang, Shu-Fang; Liu, Ji-Lai; Chen, Zhong-Rong; Kou, Wen-Jie

2013-04-01

167

Evaluation of the activation energy of viscous flow for a binary mixture in order to estimate the thermodiffusion coefficient  

NASA Astrophysics Data System (ADS)

The evaluation of the activation energy in Eyring's viscosity theory is of great importance in estimating the thermodiffusion coefficient for associating and non-associating fluid mixtures. Several methods were used to estimate the activation energies of pure components and then extended to mixtures of linear hydrocarbon chains. Results show that the recent model of Abbasi et al. [J. Chem. Phys. 131: 014502, 2009.] gives a good outcome in determining the activation energy of the components of a binary mixture. The activation energy model for pure components is shown to be useful for obtaining the activation energy of the mixture. In this paper, the activation energy model using alternative forms of Eyring's viscosity theory is used to estimate the thermodiffusion coefficient values for hydrocarbon binary mixtures. Comparisons of predicted thermodiffusion coefficients using different theoretical models with the experimental data show good capability of the activation energy model.

Abbasi, Alireza; Saghir, M. Ziad; Kawaji, Masahiro

2011-05-01

168

A vapor–liquid phase equilibrium model for binary CO 2–H 2O and CH 4–H 2O systems above 523 K for application to fluid inclusions  

Microsoft Academic Search

Accurate prediction of both volumetric and vapor–liquid phase equilibria of binary CO2–H2O and CH4–H2O mixtures with a single equation of state proves to be difficult. In this study we use an activity–fugacity model to predict the vapor–liquid phase equilibria above 523K and adapt a Helmoholtz model to calculate volumetric properties of these two binary systems. The average deviations of water

Shide Mao; Zhenhao Duan; Wenxuan Hu

2009-01-01

169

Design and Fabrication of the First Commercial-Scale Liquid Phase Methanol (LPMEOH) Reactor  

SciTech Connect

The Liquid Phase Methanol (LPMEOHT) process uses a slurry bubble column reactor to convert synthesis gas (syngas), primarily a mixture of carbon monoxide and hydrogen, to methanol. Because of its superior heat management the process can utilize directly the carbon monoxide (CO)-rich syngas characteristic of the gasification of coal, petroleum coke, residual oil, wastes, or other hydrocarbon feedstocks. The LPMEOHM Demonstration Project at Kingsport, Tennessee, is a $213.7 million cooperative agreement between the U.S. Department of Energy (DOE) and Air Products Liquid Phase Conversion Company, L.P., a partnership between Air Products and Chemicals, Inc. and Eastman Chemical Company, to produce methanol from coal-derived syngas. Construction of the LPMEOH~ Process Demonstration Plant at Eastman's chemicals-from-coal complex in Kingsport was completed in January 1997. Following commissioning and shakedown activities, the fwst production of methanol from the facility occurred on April 2, 1997. Nameplate capacity of 260 short tons per day (TPD) was achieved on April 6, 1997, and production rates have exceeded 300 TPD of methanol at times. This report describes the design, fabrication, and installation of the Kingsport LPMEOEFM reactor, which is the first commercial-scale LPMEOEPM reaetor ever built. The vessel is 7.5 feet in diameter and 70 feet tall with design conditions of 1000 psig at 600 `F. These dimensions represent a significant scale-up from prior experience at the DOE-owned Alternative Fuels Development Unit in LaPorte, Texas, where 18-inch and 22-inch diameter reactors have been tested successfidly over thousands of hours. The biggest obstacles discovered during the scale- up, however, were encountered during fabrication of the vessel. The lessons learned during this process must be considered in tailoring the design for future sites, where the reactor dimensions may grow by yet another factor of two.

None

1998-12-21

170

Analysis of liquid-phase chemical detection using guided shear horizontal-surface acoustic wave sensors.  

PubMed

Direct chemical sensing in liquid environments using polymer-guided shear horizontal surface acoustic wave sensor platforms on 36 degrees rotated Y-cut LiTaO3 is investigated. Design considerations for optimizing these devices for liquid-phase detection are systematically explored. Two different sensor geometries are experimentally and theoretically analyzed. Dual delay line devices are used with a reference line coated with poly (methyl methacrylate) (PMMA) and a sensing line coated with a chemically sensitive polymer, which acts as both a guiding layer and a sensing layer or with a PMMA waveguide and a chemically sensitive polymer. Results show the three-layer model provides higher sensitivity than the four-layer model. Contributions from mass loading and coating viscoelasticity changes to the sensor response are evaluated, taking into account the added mass, swelling, and plasticization. Chemically sensitive polymers are investigated in the detection of low concentrations (1-60 ppm) of toluene, ethylbenzene, and xylenes in water. A low-ppb level detection limit is estimated from the present experimental measurements. Sensor properties are investigated by varying the sensor geometries, coating thickness combinations, coating properties, and curing temperature for operation in liquid environments. Partition coefficients for polymer-aqueous analyte pairs are used to explain the observed trend in sensitivity for the polymers PMMA, poly(isobutylene), poly(epichlorohydrin), and poly(ethyl acrylate) used in this work. PMID:16013878

Li, Zhonghui; Jones, Yolanda; Hossenlopp, Jeanne; Cernosek, Richard; Josse, Fabien

2005-07-15

171

Liquid Phase Micro-Extraction of Linear Alkylbenzene Sulfonate Anionic Surfactants in Aqueous Samples  

PubMed Central

Hollow fiber liquid phase micro-extraction (LPME) of linear alkylbenzene sulfonates (LAS) from aqueous samples was studied. Ion pair extraction of C10, C11, C12 and C13 homologues was facilitated with trihexylamine as ion-pairing agent, using di-n-hexylether as solvent for the supported liquid membrane (SLM). Effects of extraction time, acceptor buffer concentration, stirring speed, sample volume, NaCl and humic acids were studied. At 10–50 ?g L?1 linear R2-coefficients were 0.99 for C10 and C11 and 0.96 for C12. RSD was typically ?15%. Three observations were especially made. Firstly, LPME for these analytes was unusually slow with maximum enrichment observed after 15–24 h (depending on sample volume). Secondly, the enrichment depended on LAS sample concentration with 35–150 times enrichment below ?150 ?g L?1 and 1850–4400 times enrichment at 1 mg L?1. Thirdly, lower homologues were enriched more than higher homologues at low sample concentrations, with reversed conditions at higher concentrations. These observations may be due to the fact that LAS and the amine counter ion themselves influence the mass transfer at the water-SLM interface. The observations on LPME of LAS may aid in LPME application to other compounds with surfactant properties or in surfactant enhanced membrane extraction of other compounds.

Larsson, Niklas; Otrembska, Paulina; Villar, Mercedes; Jonsson, Jan Ake

2011-01-01

172

Predicting infinite dilution activity coefficients of organic compounds in water by quantum-connectivity descriptors.  

PubMed

Quantitative structure-property relationship (QSPR) models are developed to predict the logarithm of infinite dilution activity coefficient of hydrocarbons, oxygen containing organic compounds and halogenated hydrocarbons in water at 298.15 K. The description of the molecular structure in terms of quantum-connectivity descriptors allows to obtain more simple QSPR models because of the quantum-chemical and topological information coded in this type of descriptors. The models developed in this paper have fewer descriptors and better statistics than other models reported in literature. The current models allow a more transparent physical interpretation of the phenomenon in terms of intermolecular interactions which occur in solution and which explain the respective deviations from ideality. PMID:17051339

Estrada, Ernesto; Díaz, Gerardo A; Delgado, Eduardo J

2006-09-01

173

Great Plains ASPEN Model Development: binary interaction parameters and activity coefficient parameters. Final report  

SciTech Connect

The simulation of the various sections of the Great Plains Coal Gasification Plant involves modelling vapor-liquid equilibria and liquid-liquid equilibria that are highly nonideal. The Peng-Robinson equation of state, modified for water, was used in the simulation of most of the process sections. Interaction parameters established by regression of literature data, using ASPEN's DRS system, along with interaction parameter values found in the literature, became the database for the simulation. In two of the sections, the Oxygen Plant and the TEG drying of the product SNG, activity coefficient models were used because they gave a better prediction of the phase equilibrium. For the Rectisol unit, which removes hydrogen sulfide from the gas, parameters available from a DOE sponsored contract, Tristate, were used, after verification, for the ASPEN modified version of the RKS. The phases that were predicted using these parameters were checked against literature data and, in most cases, the liquid mole fractions of carbon dioxide predicted by the correlation were within 10% of those reported. A model that would predict phase equilibrium, based on the ionization of Lewis acids and bases and salts, would have been an ideal choice for simulation of the Stretford and Phosam flowsheets. However, only limited temperature dependent liquid activity coefficients data are available in the literature for the ionic species found in the Stretford and Phosam solutions, from which correlation parameters could be obtained by regression. Also, only the flash model can handle this type of calculation; therefore, it was used only to a limited extent in the simulation of the Stretford Unit Absorber. 118 references.

Stern, S.S.; Millman, M.C.; Kirman, J.J.; Nwogu, D.

1984-12-01

174

Synthesis and Characterization of Ferroic and Multiferroic Nanostructures by Liquid Phase Deposition  

NASA Astrophysics Data System (ADS)

Magnetoelectric multiferroics have garnered an increasing interest in the past decade due to their unique properties and relevant applications in data storage, sensing and spintronics. A key requirement for the enhancement of the magnetoelectric effect at room temperature is the optimization of the interface between the constituting phases by designing nanocomposites with selectable topologies and variable chemical composition. In this research, the rational design of two-phase spinel-perovskite ceramic nanocomposites with two different geometries: coaxial nanostructures (1-D) and bilayered nanostructures (2-D), by a soft solution chemistry approach will be described. The liquid phase deposition (LPD) method is a simple and versatile route for the deposition of highly uniform spinel ferrite (MFe2O4) and/or titanium-based perovskite (BaTiO3, PbTiO3) by the controlled hydrolysis of metal fluoro-complexes at temperatures as low as 40°C. By designing a sequential deposition process, 1-D and 2-D magnetoelectric nanostructures were fabricated by filling perovskite nanotubes with the ferrite phase or depositing a ferrite layer on top of a perovskite thin film, respectively. The compositional and morphological characteristics of these highly uniform metal oxide nanostructures were investigated by X-ray diffraction (XRD), Raman spectroscopy, scanning probe microscopy (SPM) and electron microscopy (FE-SEM and TEM). The direct evidence of the stress mediated magnetoelectric coupling between the spinel and perovskite of the bilayered nanostructures was qualitatively studied by Raman spectroscopy. Additionally, the direct magnetoelectric effect in these 1-D and bilayered multiferroic nanocomposites was evaluated both quantitatively and qualitatively by using a novel magnetic field-assisted piezoelectric force microscopy (M-PFM) technique. The quantitative estimation of the magnetoelectric coupling coefficients was performed by tracking the changes in the phase and -amplitude of the piezoelectric signal signals when a in-plane dc magnetic field was applied parallel to the sample. Their non-resonant values typically range between 100-1200 mV/cm.Oe, thereby indicating a strong coupling between the magnetic and electrostrictive phases which can be used in different sensing and data storage applications. Keywords: Ferroics, Multiferroics, Liquid Phase Deposition, Scanning Probe Microscopy, Magnetic Properties, Electrical Properties

Yourdkhani, Amin

175

Coupled Densification—Shape Distortion Analysis of Liquid Phase Sintering Affected By Gravity  

NASA Astrophysics Data System (ADS)

The paper presents a model of nonlinear viscous behavior in the examination of gravity-induced distortion during liquid phase sintering. The model uses a finite element formulation to describe densification, viscous flow, and the associated dimensional changes and component slumping during sintering. The approach assumes sintering is conducted under isothermal conditions with averaged material properties. The numerical results are compared with experimental data and with a mathematical model on the distortion during liquid phase sintering of tungsten heavy alloys. The preliminary conclusions aim to provide better understanding of dimensional control during liquid phase sintering.

Alvarado-Contreras, José A.; German, Randall M.; Maximenko, Andrey L.; Olevsky, Eugene A.

2014-02-01

176

Catalytic esterification of sodium salicylate in third-liquid phase under ultrasound-assisted tri-liquid phase-transfer catalysis  

Microsoft Academic Search

The esterification of sodium salicylate to synthesize n-butyl salicylate was investigated via ultrasound-assisted tri-liquid phase-transfer catalysis. The third-liquid phase containing the catalytic intermediate tetra-n-butylphosphonium salicylate (ArCOOQ) was prepared from the reaction of sodium salicylate and tetra-n-butylphosphonium bromide with a large excess of NaBr in the aqueous phase. Under ultrasonic irradiation at 28kHz\\/300W, the product yield in the organic phase was

Hung-Ming Yang; Chien-Hsing Chen

2009-01-01

177

Transient liquid phase bonding of ferritic oxide dispersion strengthened alloys  

NASA Astrophysics Data System (ADS)

Oxide dispersion strengthened (ODS) alloys possess excellent properties including resistance to oxidation, corrosion, creep and thermal fatigue. In addition, ferritic ODS alloys exhibit resistance to void swelling and are of particular interest to the nuclear industry. The present study involves the joining of fuel cans to end caps that will be utilized in the nuclear industry. Mechanically alloyed (MA) ODS alloys possess coarse columnar grain structure strengthened with nanosize yttria dispersoids. In that past, fusion welding techniques resulted in microstructural disruption leading to poor joints. This work investigated joining of two ferritic MA ODS alloys, MA956 and PM2000, using; (a) Transient liquid phase (TLP) bonding and (b) Solid-state diffusion bonding. TLP bonds were prepared with MA956 and PM2000 in the unrecrystallized and recrystallized conditions using electron beam physical vapor deposited (EBPVD) boron thin films as interlayers. The use of thin interlayers reduced the amount of substrate dissolution and minimized the bondline microstructural disruption. Different bond orientations were also investigated. Successful bonds with better microstructural continuity were obtained when substrates were joined in the unrecrystallized condition followed by post bond recrystallization heat treatment with the substrate faying surface aligned along the working (extrusion or rolling) direction than when substrates were aligned perpendicular to the working direction. This was attributed to the number of yttria stringers cut by the bondline, which is less when the substrate faying surface is lying parallel to the working direction than when the substrate faying surface is lying perpendicular to the working direction. Solid-state diffusion bonding was conducted using MA956 and PM2000 in the unrecrystallized and recrystallized conditions. Bonding occurred only when an unrecrystallized substrate was involved. Bonding occurred at unusually low stresses. This may be attributed to the grain boundary diffusion, owing to submicron grain size of the unrecrystallized substrates. Post bond heat treatment was conducted in order to induce recrystallization in the bonds. Room temperature mechanical testing was conducted on the bonds and the bulk. Bond shear strengths and tensile strengths of up to 80% and 110% of bulk, respectively, were obtained. Defects in the bulk material such as porosity and unwanted fine grain formation were observed. Pore formation at the bondline during post bond heat treatment seems to decrease the bond strength. These defects were attributed to prior thermomechanical history of the materials.

Krishnardula, Venu Gopal

178

Utilization of Atomic Absorption Spectrophotometry for the Study of Adsorption Kinetics in the Liquid Phase.  

National Technical Information Service (NTIS)

Atomic absorption s a preferred analysis instrument for the continuous measurement of concentration variations of a cation in solution. There is one important application, which is the study of adsorption kinetics in the liquid phase of platinum with resp...

B. Rey-coruais J. Vergnaud R. Neybon

1972-01-01

179

Spatial Distribution of Crustal Anisotropy in and around the Atotsugawa Fault, Japan To Infer the Frictional Coefficient of Active Fault  

Microsoft Academic Search

The spatial variation of frictional coefficient along active fault can be inferred from detail observation of stress field around the fault. We infer the spatial variation of maximum compressional stress axis around the active faults from dense observation of crustal anisotropy. The major possible cause of seismic anisotropy in the crust is the preferred orientation of micro cracks directed parallel

T. Mizuno; H. Ito; Y. Kuwahara; K. Imanishi

2003-01-01

180

Transient liquid-phase insert metal bonding of Al2O3 and AISI 304 stainless steel  

Microsoft Academic Search

Transition liquid-phase insert metal bonding of Al2O3 and AISI 304 stainless steel based materials is investigated. This joining\\u000a technique allows the continuous replenishment of the active solute which is consumed by the chemical reaction that occurs\\u000a at the ceramic\\/filler metal interface. Replenishment is facilitated by employing a sandwich of filler materials comprising\\u000a tin-based filler metal and amorphous Cu50Ti50 or NiCrB

Y. ZHAI; T. H. NORTH; J REN

1997-01-01

181

Soot and liquid-phase fuel distributions in a newly designed optically accessible DI diesel engine  

Microsoft Academic Search

Two-dimensional (2-D) laser-sheet imaging has been used to examine the soot and liquid-phase fuel distributions in a newly designed, optically accessible, direct-injection diesel engine of the heavy-duty size class. The design of this engine preserves the intake port geometry and basic dimensions of a Cummins N-series production engine. It also includes several unique features to provide considerable optical access. Liquid-phase

J. E. Dec; C. Espey

1993-01-01

182

Use of free silicon in liquid phase sintering of silicon nitrides and sialons  

DOEpatents

This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic. 4 figs.

Raj, R.; Baik, S.

1985-11-12

183

Use of free silicon in liquid phase sintering of silicon nitrides and sialons  

DOEpatents

This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic.

Raj, Rishi (Ithaca, NY); Baik, Sunggi (Ithaca, NY)

1985-11-12

184

Solid-liquid phase equilibrium for binary Lennard-Jones mixtures  

Microsoft Academic Search

Solid-liquid phase diagrams are calculated for binary mixtures of Lennard-Jones spheres using Monte Carlo simulation and the Gibbs-Duhem integration technique of Kofke. We calculate solid-liquid phase diagrams for the model Lennard-Jones mixtures: argon-methane, krypton-methane, and argon-krypton, and compare our simulation results with experimental data and with Cottin and Monson's recent cell theory predictions. The Lennard-Jones model simulation results and the

Monica R. Hitchcock; Carol K. Hall

1999-01-01

185

Solid–liquid phase equilibrium for binary Lennard-Jones mixtures  

Microsoft Academic Search

Solid–liquid phase diagrams are calculated for binary mixtures of Lennard-Jones spheres using Monte Carlo simulation and the Gibbs–Duhem integration technique of Kofke. We calculate solid–liquid phase diagrams for the model Lennard-Jones mixtures: argon–methane, krypton–methane, and argon–krypton, and compare our simulation results with experimental data and with Cottin and Monson’s recent cell theory predictions. The Lennard-Jones model simulation results and the

Monica R. Hitchcock; Carol K. Hall

1999-01-01

186

Integration of polymer and metal microstructures using liquid-phase photopolymerization  

Microsoft Academic Search

In this paper we demonstrate, using a fabrication technique, liquid-phase photopolymerization (LP3) for the relatively fast and low-cost integration of thick polymers and electroformed metal microstructures to develop a range of microfluidic components and systems. Liquid-phase UV-photosensitive polymers, similar to negative-tone photoresists, are used to create both polymer microstructures and molds to define electroformed metal (here, nickel---Ni) microstructures. This fabrication

Abhishek K. Agarwal; David J. Beebe; Hongrui Jiang

2006-01-01

187

Integration of polymer and metal microstructures using liquid-phase photopolymerization  

Microsoft Academic Search

In this paper we demonstrate, using a fabrication technique, liquid-phase photopolymerization (LP3) for the relatively fast and low-cost integration of thick polymers and electroformed metal microstructures to develop a range of microfluidic components and systems. Liquid-phase UV-photosensitive polymers, similar to negative-tone photoresists, are used to create both polymer microstructures and molds to define electroformed metal (here, nickel—Ni) microstructures. This fabrication

Abhishek K Agarwal; David J Beebe; Hongrui Jiang

2006-01-01

188

Electrochemical corrosion of solid and liquid phase sintered silicon carbide in acidic and alkaline environments  

Microsoft Academic Search

Solid and liquid phase sintered silicon carbide (SiC) ceramics are used in aggressive environments, e.g. as seals and linings in chemical plant equipments. There exist data concerning corrosion of solid phase sintered SiC (SSiC), but there are only few data concerning their electrochemical corrosion behaviour. The corrosion of liquid phase sintered SiC ceramics (LPS SiC) containing yttria aluminium oxide grain

A. Andrews; M. Herrmann; M. Sephton; Chr. Machio; A. Michaelis

2007-01-01

189

Liquid-phase gallium-indium alloy electronics with microcontact printing.  

PubMed

Liquid-phase electronic circuits are patterned on an elastomer substrate with a microcontact printer. The printer head dips into a pool of a liquid-phase gallium-indium alloy, e.g., eutectic gallium-indium (EGaIn) or gallium-indium-tin (Galinstan), and deposits a single drop on a silicone elastomer substrate. After patterned deposition, the liquid-phase circuit is sealed with an additional layer of silicone elastomer. We also demonstrate patterned deposition of the liquid-phase GaIn alloy with a molded polydimethylsiloxane stamp that is manually inked and pressed into an elastomer substrate. As with other liquid-phase electronics produced through needle injection or masked deposition, the circuit is elastically deformable and can be stretched to several times its natural length without losing electronic functionality. In contrast to existing fabrication techniques, microcontact printing and stamp lithography can be used to produce circuits with any planar geometric feature, including electrodes with large planar area, intersecting and closed-loop wires, and combs with multiple terminal electrodes. In air, the surface of the coalesced droplets oxidize to form a thin oxide skin that preserves the shape of the circuit during sealing. This first demonstration of soft-lithography fabrication with liquid-phase GaIn alloy expands the space of allowable circuit geometries and eliminates the need for mold or mask fabrication. PMID:23659455

Tabatabai, Arya; Fassler, Andrew; Usiak, Claire; Majidi, Carmel

2013-05-21

190

Activity coefficients of actinide and rare-earth chlorides in molten LiCl/KCl eutectic salt  

SciTech Connect

Using a numerical Gibbs free-energy minimization technique, the activity coefficients of actinide and rare-earth chlorides in molten LiCl/KCl eutectic at 450 C have been calculated. Laboratory tests of an electrochemical process for separating actinide metals from rare-earth metals in LiCl/KCl solvent at 450 C provided experimental concentration and cathode potential data. The generalized expansion by Wohl was used to express the concentration dependence of the excess Gibbs free energy. The activity coefficients were expressed in terms of the Wohl volume and interaction energy parameters. The Wohl parameters for the activity coefficient expansions were obtained by minimizing the total Gibbs free energy expressed in terms of the experimental mole fractions. This thermodynamic model will be valuable for process design and scale-up calculations.

Bechtel, T.B.; Storvick, T.S. [Univ. of Missouri, Columbia, MO (United States). Dept. of Chemical Engineering] [Univ. of Missouri, Columbia, MO (United States). Dept. of Chemical Engineering

1999-04-01

191

Liquid phase methanol LaPorte process development unit: Modification, operation, and support studies  

SciTech Connect

The objectives of this program are to implement and test the process improvements identified through the engineering studies of the current program to demonstrate the capability of long-term catalyst activity maintenance, and to perform process and design engineering work that can be applied to a scaled-up Liquid Phase Methanol (LPMEOH) facility. An optional series of PDU runs is offered to extend the testing of the process improvements. A parallel research program will be performed to enhance the LPMEOH technical data base to improve the likelihood of commercialization of the LPMEOH process. Activities this quarter include: Flow sheet development for La Porte PDU modifications continues. A preliminary P ID review was completed and flow sheet modifications were identified and are being incorporated. A preliminary hazards review was completed on 22 May. Some minor flow sheet modifications resulted and a number of action items were identified. The most significant action item is to develop a materials reactivity and compatibility grid for the different alcohols, ethers, and esters which will be produced at the PDU. Heat and material balances were completed for the maximum production case of the mixed DME/MEOH synthesis campaign. An improved rate expression was developed. 1 fig.

Not Available

1990-10-23

192

[Hollow fiber liquid phase microextraction of tramadol from water and biological samples].  

PubMed

A novel technique of liquid phase microextraction supported by hollow fiber membrane (LPME-HFM) was applied to extract tramadol in tap water, urine and human plasma. At room temperature (20 degrees C), polyvinylidene fluoride hollow fiber membrane (PVDF-HFM) was employed. In the procedure of extraction, 4 microL of organic solvent (toluene) was used in individual extraction. Pethidine was used as the internal standard (IS) in the sample analysis by gas chromatography with flame ionization detector (GC-FID). The optimized conditions for tramadol extraction was as follows: toluene as organic solvent, 4 mL sample solution added with 0.1 mL of 1 mol/L NaOH solution, extraction time of 15 mm, and stirring speed of 300 r/min. The sample solutions, containing a series of concentrations of tramadol, 0.05, 0.10, 0.50, 1.0, 5.0, 10.0 mg/L, were analyzed. The good linearities were obtained for water, human urine and human plasma samples with the correlation coefficients of 0.999 7, 0.994 8 and 0.998 5, respectively. The detection limits can reach 0.01 mg/L for water and human urine and 0.05 mg/L for human plasma. The relative standard deviations (RSDs) were 10.6% and 5.15% for water, 18. 1% and 4. 03% for urine solution at the spiked levels of 0.1 and 1.0 mg/L. The RSDs were 16.6% and 4.15% for plasma solution at the spiked levels of 0.5 and 1.0 mg/L. In comparison with conventional method, this method is simple, sensitive, fast, inexpensive, and environmentally friendly. It can be applied to pharmaceutical and forensic analysis. PMID:17288152

Wang, Xiaofei; Liu, Junting; Wang, Yan; Zhao, Xiuli; Gao, Lina; Xu, Donghui

2006-11-01

193

Supramolecular solvent-based hollow fiber liquid phase microextraction of benzodiazepines.  

PubMed

A new, efficient, and environmental friendly hollow fiber liquid phase microextraction (HF-LPME) method based on supramolecular solvents was developed for extraction of five benzodiazepine drugs. The supramolecular solvent was produced from coacervation of decanoic acid aqueous vesicles in the presence of tetrabutylammonium (Bu4N(+)). In this work, benzodiazepines were extracted from aqueous samples into a supramolecular solvent impregnated in the wall pores and also filled inside the porous polypropylene hollow fiber membrane. The driving forces for the extraction were hydrophobic, hydrogen bonding, and ?-cation interactions between the analytes and the vesicular aggregates. High-performance liquid chromatography with photodiode array detection (HPLC-DAD) was applied for separation and determination of the drugs. Several parameters affecting the extraction efficiency including pH, hollow fiber length, ionic strength, stirring rate, and extraction time were investigated and optimized. Under the optimal conditions, the preconcentration factors were obtained in the range of 112-198. Linearity of the method was determined to be in the range of 1.0-200.0 ?g L(-1) for diazepam and 2.0-200.0 ?g L(-1) for other analytes with coefficient of determination (R(2)) ranging from 0.9954 to 0.9993. The limits of detection for the target benzodiazepines were in the range of 0.5-0.7 ?g L(-1). The method was successfully applied for extraction and determination of the drugs in water, fruit juice, plasma and urine samples and relative recoveries of the compounds studied were in the range of 90.0-98.8%. PMID:24267074

Rezaei, Fatemeh; Yamini, Yadollah; Moradi, Morteza; Daraei, Bahram

2013-12-01

194

Sorption kinetics of polycyclic aromatic hydrocarbons removal using granular activated carbon: intraparticle diffusion coefficients.  

PubMed

Granular activated carbon (GAC) was evaluated as a suitable sorbent for polycyclic aromatic hydrocarbons (PAHs) removal from aqueous solutions. For this purpose, kinetic measurements on the extraction of a family of six PAHs were taken. A morphology study was performed by means of a scanning electron microscopy (SEM) analysis of GAC samples. Analyses of the batch rate data for each PAH were carried out using two kinetic models: the homogenous particle diffusion model (HPDM) and the shell progressive model (SPM). The process was controlled by diffusion rate the solutes (PAHs) that penetrated the reacted layer at PAH concentrations in the range of 0.2-10 mg L(-1). The effective particle diffusion coefficients (D(eff)) derived from the two models were determined from the batch rate data. The Weber and Morris intraparticle diffusion model made a double contribution to the surface and pore diffusivities in the sorption process. The D(eff) values derived from both the HPMD and SPM equations varied from 1.1 x 10(-13) to 6.0 x 10(-14) m(2) s(-1). The simplest model, the pore diffusion model, was applied first for data analysis. The model of the next level of complexity, the surface diffusion model, was applied in order to gain a deeper understanding of the diffusion process. This model is able to explain the data, and the apparent surface diffusivities are in the same order of magnitude as the values for the sorption of functionalized aromatic hydrocarbons (phenols and sulphonates) that are described in the literature. PMID:18308468

Valderrama, C; Gamisans, X; de las Heras, X; Farrán, A; Cortina, J L

2008-09-15

195

The effect of concentration- and temperature-dependent dielectric constant on the activity coefficient of NaCl electrolyte solutions  

NASA Astrophysics Data System (ADS)

Our implicit-solvent model for the estimation of the excess chemical potential (or, equivalently, the activity coefficient) of electrolytes is based on using a dielectric constant that depends on the thermodynamic state, namely, the temperature and concentration of the electrolyte, ?(c, T). As a consequence, the excess chemical potential is split into two terms corresponding to ion-ion (II) and ion-water (IW) interactions. The II term is obtained from computer simulation using the Primitive Model of electrolytes, while the IW term is estimated from the Born treatment. In our previous work [J. Vincze, M. Valiskó, and D. Boda, "The nonmonotonic concentration dependence of the mean activity coefficient of electrolytes is a result of a balance between solvation and ion-ion correlations," J. Chem. Phys. 133, 154507 (2010)], we showed that the nonmonotonic concentration dependence of the activity coefficient can be reproduced qualitatively with this II+IW model without using any adjustable parameter. The Pauling radii were used in the calculation of the II term, while experimental solvation free energies were used in the calculation of the IW term. In this work, we analyze the effect of the parameters (dielectric constant, ionic radii, solvation free energy) on the concentration and temperature dependence of the mean activity coefficient of NaCl. We conclude that the II+IW model can explain the experimental behavior using a concentration-dependent dielectric constant and that we do not need the artificial concept of "solvated ionic radius" assumed by earlier studies.

Valiskó, Mónika; Boda, Dezs?

2014-06-01

196

Equation of state associated with activity coefficient models to predict low and high pressure vapor–liquid equilibria  

Microsoft Academic Search

A simple and thermodynamically consistent method is presented to establish an equation of state for mixtures by using activity coefficient model parameters. All current solution models such as NRTL, van Laar, UNIFAC, or any other thermodynamic model can be used. The main feature of the method presented is that only a single scaling factor value determined at a given reference

Otilio Hernández-Garduza; Fernando Garc??a-Sánchez; Evelyne Neau; Marek Rogalski

2000-01-01

197

Liquid phase fluid dynamic (methanol) run in the LaPorte alternative fuels development unit  

SciTech Connect

A fluid dynamic study was successfully completed in a bubble column at DOE's Alternative Fuels Development Unit (AFDU) in LaPorte, Texas. Significant fluid dynamic information was gathered at pilot scale during three weeks of Liquid Phase Methanol (LPMEOJP) operations in June 1995. In addition to the usual nuclear density and temperature measurements, unique differential pressure data were collected using Sandia's high-speed data acquisition system to gain insight on flow regime characteristics and bubble size distribution. Statistical analysis of the fluctuations in the pressure data suggests that the column was being operated in the churn turbulent regime at most of the velocities considered. Dynamic gas disengagement experiments showed a different behavior than seen in low-pressure, cold-flow work. Operation with a superficial gas velocity of 1.2 ft/sec was achieved during this run, with stable fluid dynamics and catalyst performance. Improvements included for catalyst activation in the design of the Clean Coal III LPMEOH{trademark} plant at Kingsport, Tennessee, were also confirmed. In addition, an alternate catalyst was demonstrated for LPMEOH{trademark}.

Bharat L. Bhatt

1997-05-01

198

Partial transient liquid phase diffusion bonding of Zircaloy-4 to stabilized austenitic stainless steel 321  

SciTech Connect

An innovative method was applied for bonding Zircaloy-4 to stabilized austenitic stainless steel 321 using an active titanium interlayer. Specimens were joined by a partial transient liquid phase diffusion bonding method in a vacuum furnace at different temperatures under 1 MPa dynamic pressure of contact. The influence of different bonding temperatures on the microstructure, microindentation hardness, joint strength and interlayer thickness has been studied. The diffusion of Fe, Cr, Ni and Zr has been investigated by scanning electron microscopy and energy dispersive spectroscopy elemental analyses. Results showed that control of the heating and cooling rate and 20 min soaking at 1223 K produces a perfect joint. However, solid-state diffusion of the melting point depressant elements into the joint metal causes the solid/liquid interface to advance until the joint is solidified. The tensile strength of all the bonded specimens was found around 480-670 MPa. Energy dispersive spectroscopy studies indicated that the melting occurred along the interface of the bonded specimens as a result of the transfer of atoms between the interlayer and the matrix during bonding. This technique provides a reliable method of bonding zirconium alloy to stainless steel.

Atabaki, M. Mazar, E-mail: m.mazaratabaki@gmail.com [Department of Materials Engineering, Faculty of Mechanical Engineering, University Technology Malaysia, 81310 (Malaysia); Hanzaei, A. Talebi [Department of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran (Iran, Islamic Republic of)

2010-10-15

199

Liquid phase methanol LaPorte process development unit: Modification, operation, and support studies  

SciTech Connect

Contract objectives are to perform process and design engineering work that can be applied to a scaled-up Liquid Phase Methanol (LPMEOH*) facility. An optional series of runs on the Process Development Unit (PDU) is offered to extend the testing of the process improvements. This quarter a four-parameter, mathematical model based on a dual-site Langmuir-Hinshelwood mechanism was used by PSG Researchers to successfully describe LPMEOH reaction kinetics with BASF S3-85 catalyst. Methanol synthesis catalyst is susceptible to poisoning by trace contaminants (eg. H{sub 2}S, COS, iron carbonyl) present in coal-derived synthesis gas. A guard-bed adsorption system developed by PSG Research to treat feed gas to a LPMEOH reactor was successfully tested in the final phase of the Iron Run laboratory program. The first series of coal gas clean-up experiments at the Great Plains Synfuels plant site were completed. Catalyst activity experienced persistent decline. Two scenarios were identified as the most likely reasons for the deactivation. 12 figs., 5 tabs.

Brown, D.M. (Air Products and Chemicals, Inc., Allentown, PA (USA)); Frank, M.E. (Chem Systems, Inc., Tarrytown, NY (USA))

1990-06-18

200

Water Detritiation: Better SCK-CEN Catalysts for Liquid Phase Catalytic Exchange  

SciTech Connect

A technically and economically sound technology for water detritiation is mandatory for the future of fusion. This technology is expected to be based on water electrolysis and Liquid Phase Catalytic Exchange (LPCE). LPCE requires an efficient hydrophobic catalyst. SCK-CEN invented and developed such a catalyst in the past, which is prepared by depositing platinum on an activated charcoal carrier and mixing it with polytetrafluorethylene as a hydrophobic material. In combination with an appropriate wettable packing, different batches of this catalyst performed very well during years of extensive testing, allowing us to develop the ELEX process for water detritiation at inland reprocessing plants. Recently we succeeded in reproducing this catalyst and preparing a slightly different but clearly ameliorated type. By extrapolation these new results would allow us to obtain, at 40 deg. C and under typical but conservative operating conditions, a decontamination factor of 10000 with a column of less than 3 meters long. Such performances would make this catalyst an excellent candidate for application at JET or ITER. To confirm the performances of our improved catalyst for a longer period of time and in a longer column, we are now starting experiments in a newly built installation and we are collaborating with ICSI, Romania.

Bruggeman, Aime; Braet, Johan; Vanderbiesen, Sven [SCK-CEN (Belgium)

2005-07-15

201

Images reveal that atmospheric particles can undergo liquid-liquid phase separations  

PubMed Central

A large fraction of submicron atmospheric aerosol particles contains both organic material and inorganic salts. As the relative humidity cycles in the atmosphere and the water content of the particles correspondingly changes, these mixed particles can undergo a range of phase transitions, possibly including liquid–liquid phase separation. If liquid–liquid phase separation occurs, the gas-particle partitioning of atmospheric semivolatile organic compounds, the scattering and absorption of solar radiation, and the reactive uptake of gas species on atmospheric particles may be affected, with important implications for climate predictions. The actual occurrence of liquid–liquid phase separation within individual atmospheric particles has been considered uncertain, in large part because of the absence of observations for real-world samples. Here, using optical and fluorescence microscopy, we present images that show the coexistence of two noncrystalline phases for real-world samples collected on multiple days in Atlanta, GA as well as for laboratory-generated samples under simulated atmospheric conditions. These results reveal that atmospheric particles can undergo liquid–liquid phase separations. To explore the implications of these findings, we carried out simulations of the Atlanta urban environment and found that liquid–liquid phase separation can result in increased concentrations of gas-phase NO3 and N2O5 due to decreased particle uptake of N2O5.

You, Yuan; Renbaum-Wolff, Lindsay; Carreras-Sospedra, Marc; Hanna, Sarah J.; Hiranuma, Naruki; Kamal, Saeid; Smith, Mackenzie L.; Zhang, Xiaolu; Weber, Rodney J.; Shilling, John E.; Dabdub, Donald; Martin, Scot T.; Bertram, Allan K.

2012-01-01

202

Improving properties of P/M steels through liquid phase sintering  

SciTech Connect

Steady state liquid phase sintering was utilized to achieve virtually full density in hypereutectoid steels at a temperature of 1175 C. The non-uniform porosity observed in the microstructure of certain liquid phase sintered compacts was accounted for by a proposed liquid phase capillary flow and consequent localized densification. Recommendations are made for avoiding this segregated porosity and were successfully used to prepare high density hypoeutectoid steels by short time transient liquid phase sintering (approx. 10 minutes) at a moderate temperature (1175 C). The mechanical properties of these sintered steels are close to commercial wrought steels and much better than commercial P/M steels. A new intermetallic compound based on the copper-manganese-silicon systems had very desirable properties for use in transient liquid phase sintering of ferrous materials. Its melting point is 780 C and tendency to wet iron is remarkable. During heating to the sintering temperature, the compound melts and spreads rapidly over all the surfaces which effectively reduces the diffusion distance to the order of one particle radius. The addition of this new material to iron base powders has a beneficial effect on the sintered density, hardness, tensile and transverse rupture strength. 8 references, 10 figures.

Pickus, M.R.

1984-01-01

203

Radial distribution modeling of liquid-phase phenol concentration in a liquid-solid fluidized bed photoreactor.  

PubMed

A fluidized bed photoreactor with titanium dioxide-immobilized spherical activated carbon particles was examined. The light intensity profile was modeled using the Lambert-Beer rule for the modeling of the radial distribution of liquid-phase phenol concentration in the fluidized bed photoreactor, when considering the reactor composed of numerous differential annular drums and no mass transfer between drums. The model could be well matched with the experimental data which indicated the liquid flow rate of 13.8 L/min was the optimum in the balance of flow rate-related light penetration and photocatalyst concentration. By integration of liquid-phase phenol concentration along the radius, photocatalytic oxidation performance of the photoreactor was evaluated in comparison with the experimental data and model prediction. The results showed that the errors were less than 30% for most of the predictions. It is suggested that mass transfer and flow rate difference along the radial direction should be considered to obtain more precise prediction. PMID:22377991

Dong, Shuangshi; Zhou, Dandan; Bi, Xiaotao

2012-01-01

204

Fluoroponytailed crown ethers and quaternary ammonium salts as solid-liquid phase transfer catalysts in organic synthesis.  

PubMed

Fluorous derivatives of dibenzo-18-crown-6 ether were prepared, and then successfully applied in representative solid-liquid phase transfer catalysis reactions, which were performed in standard organic solvents, such as chlorobenzene and toluene, as well as in fluorous solvents, such as perfluoro-1,3-dimethylcyclohexane. It was clearly shown that properly designed fluoroponytailed crown ethers could promote the disintegration of the crystal lattice of alkali salts, and transfer anions from the solid surface into an apolar, non-coordinating perfluorocarbon phase, for phase transfer catalysis reactions in organic synthesis. Furthermore, 3,5-bis(perfluorooctyl)benzyl bromide and triethylamine were reacted under mild conditions to provide an analogue of the versatile phase transfer catalyst, benzyltriethylammonium chloride, containing two fluoroponytails. This fluoroponytailed quaternary ammonium salt was also successfully employed as a catalyst in a variety of organic reactions conducted under solid-liquid phase transfer catalysis conditions, without a perfluorocarbon phase. Thus, being both hydrophobic and lipophobic, fluorous crown ethers and ammonium salts, could be rapidly recovered in quantitative yields, and reused without loss of activity, over several reaction cycles. PMID:21928010

Pozzi, Gianluca; Fish, Richard H

2012-01-01

205

Individual Activity Coefficients of H+ and Br-in KBr Solution.  

National Technical Information Service (NTIS)

The electrode Ag/AgBr/HBr was investigated for the true temperature coefficient of its electrode potential. Measurements at 25 and 35C were extended over the concentration range from about 0.001 m to 0.1 m. Extrapolation to zero ionic strength gives the t...

F. La Torre G. Milazzo

1973-01-01

206

Empty liquid phase of colloidal ellipsoids: the role of shape and interaction anisotropy.  

PubMed

We study the effect of anisotropic excluded volume and attractive interactions on the vapor-liquid phase transition of colloidal ellipsoids. In our model, the hard ellipsoid is embedded into an ellipsoidal well, where both the shape of the hard ellipsoid and that of the added enclosing ellipsoidal well can be varied independently. The bulk properties of these particles are examined by means of a van der Waals type perturbation theory and validated with replica exchange Monte Carlo simulations. It is shown that both the critical volume fraction (?c) and the critical temperature (Tc) of the vapor-liquid phase transition vanish with increasing shape anisotropy for oblate shapes, while ?c ? 0 and Tc ? 0 are obtained for very elongated prolate shapes. These results suggest that the chance to stabilize empty liquids (a liquid phase with vanishing density) is higher in suspensions of rod-like colloidal ellipsoids than in those of plate-like ones. PMID:24712814

Varga, Szabolcs; Meneses-Júarez, Efrain; Odriozola, Gerardo

2014-04-01

207

Biomembrane Liquid-liquid Phase Separation and Detergent Resistance: A Relationship Strengthened  

PubMed Central

Since evidence first appeared for “detergent-resistant membranes” in the early to mid 1990s, cell biologists from a wide spectrum of biological sciences have been intrigued by the functional relevance of this indication of membrane heterogeneity, commonly referred to as “lipid rafts”. Model membrane studies revealed that these lipid rafts are related to the more ordered liquid phase that forms in a ternary mixture of cholesterol with a phospholipid containing saturated acyl chains and one with unsaturated acyl chains. Giant plasma membrane vesicles that pinch off from cells undergo similar liquid-liquid phase separation as ternary model membranes and have provided an experimental bridge between these and intact cells. The study by Levental et al. in the current issue of Biochemical Journal provides new insights into the relationship between liquid-liquid phase separation in these plasma membrane vesicles and detergent resistance of cellular lipid rafts.

Holowka, David

2014-01-01

208

Biofilm thickness measurement using an ultrasound method in a liquid phase.  

PubMed

In this report, the development of an online, noninvasive, measurement method of the biofilm thickness in a liquid phase is presented. The method is based in the analysis of the ultrasound wave pulse-echo behavior in a liquid phase reproducing the real reactor conditions. It does not imply the removal of the biomass from the support or any kind of intervention in the support (pipes) to detect and perform the measurements (non-invasiveness). The developed method allows for its sensor to be easily and quickly mounted and unmounted in any location along a pipe or reactor wall. Finally, this method is an important innovation because it allows the thickness measurement of a biofilm, in liquid phase conditions that can be used in monitoring programs, to help in scheduling cleaning actions to remove the unwanted biofilm, in several application areas, namely in potable water supply pipes. PMID:23494195

Maurício, R; Dias, C J; Jubilado, N; Santana, F

2013-10-01

209

Carbon dioxide tolerance in the single-stage liquid-phase synthesis of dimethyl ether  

SciTech Connect

In the liquid-phase dimethyl ether process, methanol synthesis catalyst (Cu/ZnO/Al{sub 2}O{sub 3}) and methanol dehydration catalyst ({gamma}-alumina) are slurred in an inert liquid medium. The inert liquid medium used in this investigation is a white mineral oil, Witco-40. This multiphase reaction is conducted in a mechanically agitated slurry reactor. In this process, syngas conversion can be significantly improved by coproduction of dimethyl ether along with methanol. The coproduction strategy improves the thermodynamic and kinetic environment of the reaction system. The effects of catalyst loadings in the slurry and the roles played by carbon dioxide in dimethyl ether synthesis were studied by conducting kinetic experiments. The liquid-phase dimethyl ether synthesis process exhibits higher carbon dioxide tolerance as compared to the liquid-phase methanol synthesis process, whose optimal carbon dioxide concentration in the unbalanced syngas feed is around 8%. These results have been experimentally confirmed.

Sardesai, A.; Gunda, A.; Tartamella, T.; Lee, S.

2000-01-01

210

Comparison of Solid Phase Epi (SPE) non-melt to Liquid Phase Epi (LPE) melt laser annealing for 22nm node n+ USJ formation  

Microsoft Academic Search

Arsenic, Phosphorus and Antimony dopants for n+ USJ formation was studied for junction quality comparing nonmelt to melt laser annealing without and with BF2 or In HALO structures. When junction leakage was high >2E-2A\\/cm2 no reliable sheet resistance could be determined. We observed between 21nm to 70nm of liquid phase dopant diffusion with the melt process and dopant activation levels

J. Borland; S. Shishiguchi; N. Matsuzaka; M. Hane; M. Tanjyo; P. Oesterlini; J. Mayer

2010-01-01

211

Influence of Eu 3+ doping content on photoluminescence of Gd 2O 3:Eu 3+ phosphors prepared by liquid-phase reaction method  

Microsoft Academic Search

Europium-doped cubic Gd2O3:Eu3+ nanoparticles containing various activator content in the range of 5–15wt% were synthesized by a liquid-phase reaction method to investigate the influence of Eu3+ loading on the optical properties of phosphors by using XRD, TEM, BET, spectrometer and fluorometer. The size of Gd2O3:Eu3+ powders was in the range 21–41nm. The phosphors showed an initial increase in luminescence and

Chung-Sik Park; Min-Gi Kwak; Seung-Seok Choi; Yo-Seung Song; Sung-Jei Hong; Jeong-In Han; Deuk Yong Lee

2006-01-01

212

Effect of water on liquid phase DME synthesis from syngas over hybrid catalysts composed of Cu\\/ZnO\\/Al 2 O 3 and ?-Al 2 O 3  

Microsoft Academic Search

DME synthesis from syngas via methanol has been carried out in a single-stage liquid phase reactor. Cu\\/ ZnO\\/Al2O3 and ?-Al2O3 were used together as methanol synthesis catalyst and dehydration catalyst, respectively. The influence of water on the catalytic\\u000a system was investigated mainly. Water affected the activity of methanol dehydration catalyst as well as methanol synthesis\\u000a catalyst. Thus, removal of water

Hak-Ju Kim; Heon Jung; Kwan-Young Lee

2001-01-01

213

FBG application in monitoring the liquid-solid and gas-liquid phase transitions of water  

NASA Astrophysics Data System (ADS)

We propose to monitor the liquid-solid and gas-liquid phase transition of water based on FBG sensors. The naked FBGs and the packaged FBG temperature sensors are used to monitoring the liquid-solid phase transition of water at the same time in order to find its characteristics, including the supercooling state and the strain and pressure change introduced by the phase transition. Fourteen FBGs are packaged and arranged in a steam boiler in order to monitor the gas-liquid phase transition, including the temperature and pressure change inside the steam boiler and the strain of the boiler wall. The preliminary experimental results are demonstrated here.

Quan, Chai; Later, Khalil; Yang, Lijie; Peng, Shijun; Zhang, Anna; Hao, Qianqian; Zhang, Jianzhong; Sun, Weimin; Yuan, Libo; Peng, G. D.

2012-01-01

214

Liquid-phase detection instrument to record and annunciate procedural deviations in sintering runs  

SciTech Connect

A liquid-phase detection instrument (LPDI) has been developed to aid in making consistently accurate alloy sintering runs. The LPDI displays the furnace temperature, detects the alloy's liquid-phase arrest temperature, calculates the necessary hold temperature from the arrest temperature (i.e., calibrates the system), and provides a digital record for quality assurance purposes. In field tests, the instrument's detected arrest temperature was within +1/sup 0/ to -0/sup 0/C of an operator's assessment of the actual arrest temperature.

Mee, D. K.; Darby, D. M.; Sims, Jr., T. M.

1981-04-15

215

Liquid-Liquid Phase Transition and Glass Transition in a Monoatomic Model System  

PubMed Central

We review our recent study on the polyamorphism of the liquid and glass states in a monatomic system, a two-scale spherical-symmetric Jagla model with both attractive and repulsive interactions. This potential with a parametrization for which crystallization can be avoided and both the glass transition and the liquid-liquid phase transition are clearly separated, displays water-like anomalies as well as polyamorphism in both liquid and glassy states, providing a unique opportunity to study the interplay between the liquid-liquid phase transition and the glass transition. Our study on a simple model may be useful in understanding recent studies of polyamorphism in metallic glasses.

Xu, Limei; Buldyrev, Sergey V.; Giovambattista, Nicolas; Stanley, H. Eugene

2010-01-01

216

Ethers from ethanol. 3: Equilibrium conversion and selectivity limitations in the liquid-phase synthesis of two tert-hexyl ethyl ethers  

SciTech Connect

Alternatives to the conventional isobutylene-derived ethers, namely methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE), are being explored, e.g., those produced from a combination of the branched C{sub 5} and C{sub 6} olefins with methanol or biomass-based ethanol. The conversion and selectivity of these ethers are thermodynamically limited. This paper, thus, describes the determination and analysis of the equilibrium limitations in the liquid-phase synthesis of two of the three possible isomers of tert-hexyl ethyl ether (THEE) from reactive C{sub 6} olefins and ethanol in the temperature range 298--353 K. The coupled reaction network for either of these two ethers involves two simultaneous esterification and one isomerization reactions, all being reversible. The equilibrium constants for these reactions, experimentally determined from equilibrium composition and the corresponding activity coefficients estimated by the UNIFAC method, decrease in the following order of tertiary olefins: 2M1P > isobutylene < 2,3DM1B {approx} 2M1B > 2M2P > 2M2B > 2,3DM2B for etherification reactions with ethanol, and (2,3DM1B {r_reversible} 2,3DM2B) > (2M1B {r_reversible} 2M2B) > (2M1P {r_reversible} 2M2P) for the isomerization reactions. This is explained on the basis of the relative stability of these olefins. The developed correlations are used to study the influence of process variables on the equilibrium conversion and selectivity of THEE formation.

Zhang, T.; Datta, R. [Univ. of Iowa, Iowa City, IA (United States). Dept. of Chemical and Biochemical Engineering

1995-07-01

217

Activities and osmotic coefficients of tropospheric aerosols: (NH 4 ) 2 SO 4 (aq) and NaCl(aq)  

Microsoft Academic Search

The theory of multilayer adsorption for concentrated aqueous electrolytes developed by Ally and Braunstein (1998) is used to calculate the thermodynamic activities and osmotic coefficients of supersaturated solutions of (NH4)2SO4(aq) and NaCl (aq) which are among man-made aerosols of atmospheric importance. The basis of the model is the postulate of Stokes and Robinson that concentrated aqueous electrolytes may be viewed

John M. Simonson

2001-01-01

218

Transference Numbers and Activity Coefficients of Solutions of KCI and NaCI in Glycerol Using Concentration Cells  

Microsoft Academic Search

Transference numbers and mean ionic activity coefficients of solutions of potassium chloride and sodium chloride in glycerol have been measured at 25°C using concentration cells with silver\\/silver chloride electrodes. The EMFs of cells with transference, using a liquid junction, were measured at concentrations between 0.001 and 0.5 mol dm, and the EMFs of cells without transference were measured using a

D. C. Champeney; H. Comert

1988-01-01

219

Liquid phase synthesis of annelated pyridines over molecular sieve catalyst  

Microsoft Academic Search

Simple and selective single step synthesis of substituted octahydrophenanthridines and annelated pyridines was achieved using simple cyclic ketones, aliphatic aldehydes and ammonia over zeolites as catalyst under high pressure (autogeneous pressure) conditions with high yields and high conversions for the first time. The catalyst was inexpensive, environmentally friendly and could be reused many times without significant loss of activity.

Kandepi V. V. Krishna Mohan; Nama Narender; Shivanand J. Kulkarni

2007-01-01

220

Simultaneous reconstruction of emission activity and attenuation coefficient distribution from TOF data, acquired with external transmission source.  

PubMed

The simultaneous PET data reconstruction of emission activity and attenuation coefficient distribution is presented, where the attenuation image is constrained by exploiting an external transmission source. Data are acquired in time-of-flight (TOF) mode, allowing in principle for separation of emission and transmission data. Nevertheless, here all data are reconstructed at once, eliminating the need to trace the position of the transmission source in sinogram space. Contamination of emission data by the transmission source and vice versa is naturally modeled. Attenuated emission activity data also provide additional information about object attenuation coefficient values. The algorithm alternates between attenuation and emission activity image updates. We also proposed a method of estimation of spatial scatter distribution from the transmission source by incorporating knowledge about the expected range of attenuation map values. The reconstruction of experimental data from the Siemens mCT scanner suggests that simultaneous reconstruction improves attenuation map image quality, as compared to when data are separated. In the presented example, the attenuation map image noise was reduced and non-uniformity artifacts that occurred due to scatter estimation were suppressed. On the other hand, the use of transmission data stabilizes attenuation coefficient distribution reconstruction from TOF emission data alone. The example of improving emission images by refining a CT-based patient attenuation map is presented, revealing potential benefits of simultaneous CT and PET data reconstruction. PMID:23648397

Panin, V Y; Aykac, M; Casey, M E

2013-06-01

221

Simultaneous reconstruction of emission activity and attenuation coefficient distribution from TOF data, acquired with external transmission source  

NASA Astrophysics Data System (ADS)

The simultaneous PET data reconstruction of emission activity and attenuation coefficient distribution is presented, where the attenuation image is constrained by exploiting an external transmission source. Data are acquired in time-of-flight (TOF) mode, allowing in principle for separation of emission and transmission data. Nevertheless, here all data are reconstructed at once, eliminating the need to trace the position of the transmission source in sinogram space. Contamination of emission data by the transmission source and vice versa is naturally modeled. Attenuated emission activity data also provide additional information about object attenuation coefficient values. The algorithm alternates between attenuation and emission activity image updates. We also proposed a method of estimation of spatial scatter distribution from the transmission source by incorporating knowledge about the expected range of attenuation map values. The reconstruction of experimental data from the Siemens mCT scanner suggests that simultaneous reconstruction improves attenuation map image quality, as compared to when data are separated. In the presented example, the attenuation map image noise was reduced and non-uniformity artifacts that occurred due to scatter estimation were suppressed. On the other hand, the use of transmission data stabilizes attenuation coefficient distribution reconstruction from TOF emission data alone. The example of improving emission images by refining a CT-based patient attenuation map is presented, revealing potential benefits of simultaneous CT and PET data reconstruction.

Panin, V. Y.; Aykac, M.; Casey, M. E.

2013-06-01

222

Second virial coefficients of dipolar hard spheres  

NASA Astrophysics Data System (ADS)

An asymptotic formula is reported for the second virial coefficient B2 of a dipolar hard-sphere (DHS) fluid, in zero external field, for strongly coupled dipolar interactions. This simple formula, together with the one for the weak-coupling B2, provides an accurate prediction of the second virial coefficient for a wide range of dipole moments, including those that are experimentally accessible in magnetite ferrofluids. The weak-coupling B2 also yields an estimate of the magnetic moment minimally needed for isotropic gas-liquid phase-separation, if any, in the DHS fluid.

Philipse, Albert P.; Kuipers, Bonny W. M.

2010-08-01

223

Installation of liquid phase catalytic exchange columns for the Wolsong tritium removal facility  

Microsoft Academic Search

The catalyst loading and installation of liquid phase catalytic exchange (LPCE) columns for the Wolsong tritium removal facility (WTRF) was completed on the 22nd of April 2006. Two LPCE columns are connected in series. The first column has 28 sections, a sump and a separate overhead condenser. The second column has 27 sections, a sump and a humidifier. Each section

K. M. Song; S. H. Sohn; D. W. Kang; S. W. Paek; D. H. Ahn

2007-01-01

224

Determination of the liquid-phase speciation in the MDEA - H 2O - CO 2 system  

Microsoft Academic Search

Aqueous solutions of alkanolamines are commonly used in CO2 capture processes. To describe these complex processes rigorous mass transfer models are needed, in which all mass transfer, kinetics and thermodynamics are incorporated correctly. To improve the quality of the thermodynamic models, not only commonly used P-? (CO2 partial pressure versus CO2 liquid loading) experimental data, but also liquid phase speciation

Peter W. J. Derks; Patrick J. G. Huttenhuis; Coen van Aken; Jan-Henk Marsman; Geert F. Versteeg

2011-01-01

225

A LIMITATION OF REUSING THE CATALYST IN TRI-LIQUID-PHASE CATALYTIC SYSTEMS  

Microsoft Academic Search

This work demonstrates important factor influencing the reusability of the phase transfer catalyst in the third liquid phase in addition to the role of the possible loss of catalyst due to the dissolution of the catalyst into the aqueous and organic phases. When the catalyst might react with the byproducts, in addition to reacting with the organic substrate and aqueous

HSU-CHIN HSIAO; HUNG-SHAN WENG

2004-01-01

226

Liquid phase sintering of tungsten composites under microgravity: Influence of liquid\\/particle surface energy  

Microsoft Academic Search

Tungsten-nickel-iron heavy metals are fabricated from powders by liquid phase sintering. A study of the sintering mechanism of heavy metals with a low amount of tungsten particles can, depending on sedimentation, only be done under microgravity. At two earlier Texus flights, No 10 & 19, the growth rate and agglomeration of tungsten particles under microgravity were compared to that under

L. B. Ekbom; B. Lei; A. Eliasson; A. Jarfors

1991-01-01

227

Binary Liquid Phase Separation and Critical Phenomena in a Protein\\/Water Solution  

Microsoft Academic Search

We have investigated the phase diagram of aqueous solutions of the bovine lens protein gamma II-crystallin. For temperatures T < Tc = 278.5 K, we find that these solutions exhibit a reversible coexistence between two isotropic liquid phases differing in protein concentration. The dilute and concentrated branches of the coexistence curve were characterized, consistently, both by measurements of the two

John A. Thomson; Peter Schurtenberger; George M. Thurston; George B. Benedek

1987-01-01

228

Dye Assisted-Optical Lithography of Polymers from Liquid-Phase  

Microsoft Academic Search

There has been much recent interest in polymeric materials for holographic gratings in the field of information storage, wave guide coupling, and non linear optoelectronics. Polybutadiene which is synthetic rubber is biologically benign and used in making it attractive as a platform for biomolecular applications. NBD dye assisted optical Lithography of polybutadiene polymers from liquid phase is our main interest

Redahegn Sileshi; Jean-Mishel Taguenang; Fernando Calzzani; Aschalew Kassu; Anup Sharma

2008-01-01

229

Quantitative imaging by confocal scanning fluorescence microscopy of protein crystallization via liquid-liquid phase separation.  

PubMed

Metastable states such as liquid-liquid phase separation, aggregation and gelation can affect protein crystallization but their positive or negative effects are only partially understood. In this work, mixtures of PEG (MW 10 kDa) and a large model protein, glucose isomerase (MW 173 kDa), have been studied to characterize the effect of a metastable liquid-liquid phase separation on protein crystallization. Fluorescence labeling allowed confocal fluorescence microscopy observations and quantification of the partitioning of the protein and PEG between the liquid phases and showed two steps in the crystallization process. Two crystallization mechanisms within the liquid domain were revealed, yielding two different polymorphs. With one polymorph, few crystals nucleated and grew droplet-by-droplet in the dispersed concentrated liquid phase, while for the other homogeneous crystal nucleation and growth occurred independently and simultaneously in numerous droplets of the concentrated phase. The results demonstrate the substantial possible complexity of crystallization behavior, as well as its sensitivity to the location of the conditions on the phase diagram and to the physicochemical properties of the system. PMID:15930647

Vivarès, Denis; Kaler, Eric W; Lenhoff, Abraham M

2005-06-01

230

Low-cost Engineering of Laser Rods and Slabs with Liquid Phase Epitaxy.  

National Technical Information Service (NTIS)

We investigated the use of a liquid phase epitaxial (LPE) coating to improve the performance of a rod or slab laser. A single crystal erbium-doped yttrium aluminum garnet (Er:YAG) rod coated with undoped YAG, and an uncoated sample were procured, then com...

C. E. Mungan J. O. White

2011-01-01

231

Liquid Phase Methanation Pressure Study. Interim Report, Series No. I: E-3.  

National Technical Information Service (NTIS)

One of the processes being considered in the ERDA-A.G.A. program for high Btu gas from coal is liquid phase methanation. This process has been demonstrated over a wide range of pressures--from under 500 psig to over 1000 psig. A premise of the program is ...

J. J. Bolin M. Y. Tse V. P. Sirohi

1974-01-01

232

Application potential of liquid-phase acoustic wave devices as chemical and biochemical sensors  

Microsoft Academic Search

Theoretical concept and potential ability of the bulk acoustic wave device as a liquid-phase sensor are discussed. The sensitivity of the sensor to liquid medium properties and to the device liquid-solid interface were evaluated. The surface free energy and interfacial viscosity are proved to have significant influence in determining the frequency responses, besides the effect of added mass. The experiments

Biljana A. ?avi?-Vlasak; L. Jubinka V. Rajakovi?

1992-01-01

233

Gravity effects in the problem of gas bubble formation and dynamics in liquid phase  

Microsoft Academic Search

Gravity effects in the problem of nucleation, development, and dynamics of gaseous inclusions in liquid phase are considered under gravity and microgravity conditions. It is shown that gravity has an impact on nucleation due to both the hydrostatic pressure in liquid and the capillary pressure. For poor wetting the latter effect suppresses the bubble nucleation with the evaporation of volatile

V. P. Shalimov

1991-01-01

234

Liquid phase oxidation of thiophene compounds by tert-butyl hydroperoxide  

Microsoft Academic Search

Oxidative instability problems in both shale and petroleum-derived middle distillate fuels are related to the presence of hydroperoxides. Although a good body of knowledge exists concerning the formation of peroxides in the liquid phase, relatively little is known about the reaction\\/decomposition pathways when other functional groups are present. One of the significant and undesirable problems is the formation of solid

G. W. Mushrush; J. M. Jr. Watkins; R. N. Hazlett; D. R. Hardy; H. G. Eaton

1987-01-01

235

Thermodynamic principles in the liquid-phase reduction of oxides in an oxygen converter  

Microsoft Academic Search

Researchers are very interested in new energy-sav- ing production technologies. As we know, metallurgy has been slow to replace existing technologies with more efficient alternatives. Currently, the positive prospects for converter technol- ogy are linked to the energy savings associated with the processing of industrial wastes and iron ore by liquid- phase reduction. However, various problems are encountered here. The

I. A. Zhibinova; K. M. Shakirov; E. V. Protopopov; M. K. Shakirov

2009-01-01

236

Effect of liquid phase mobility on gas hydrate dissociation in reservoirs  

Microsoft Academic Search

Boundary conditions on the dissociation surface that take the motion of the liquid phase into account are derived. An analytic solution of the problem is obtained for small deviations from the initial state. The integral characteristic of the phase transitions in the extended zone is introduced and represented analytically. It is shown that for high initial values of the hydrate

G. G. Tsypkin

1991-01-01

237

Transient liquid phase diffusion bonding and associated recrystallization phenomenon when joining ODS ferritic superalloys  

Microsoft Academic Search

Oxide dispersion strengthened (ODS) ferritic superalloys attribute their excellent intermediate and high temperature creep resistant properties to the distribution of an inert oxide, Y2O3 within highly directional and elongated grains. Careful selection of joining techniques is, therefore, of utmost importance so that the parent metal microstructure is not disrupted and is continuous across the bond line. Transient liquid phase (TLP)

T. I. Khan; E. R. Wallach

1996-01-01

238

Modelling of transient liquid phase bonding in binary systems—A new parametric study  

Microsoft Academic Search

An established mathematical model, describing the rate at which transient liquid phase bonding (TLP bonding) progresses in binary alloy systems, is subjected to careful scrutiny. It is shown that the process can be characterised using just two dimensionless parameters. An advantage of such dimensionless characterisation is demonstrated by analysis of the solution for solidification of semi-infinite systems. It is known

T. C. Illingworth; I. O. Golosnoy; T. W. Clyne

2007-01-01

239

Transient liquid phase diffusion bonding of Udimet 720 for Stirling power converter applications  

Microsoft Academic Search

Udimet 720 has been selected for use on Stirling power converters for space applications. Because Udimet 720 is generally considered susceptible to strain age cracking if traditional fusion welding is used, other joining methods are being considered. A process for transient liquid phase diffusion bonding of Udimet 720 has been theoretically developed in an effort to eliminate the strain age

Donald L. Mittendorf; William G. Baggenstoss

1992-01-01

240

Liquid-phase reactions induced by gaseous plasma. Decomposition of benzoic acids in aqueous solution  

Microsoft Academic Search

The liquid-phase organic reactions induced by a gaseous plasma, which was generated in a localized zone between an electrolytic solution and an anode by means of contact glow discharge electrolysis (CGDE), were investigated. Benzoic acids dissolved in a neutral phosphate buffer solution were efficiently oxidized and eventually decomposed to inorganic carbon. As the intermediate products, oxalic, formic and malonic acids

M. Tezuka; M. Iwasaki

1999-01-01

241

Separation of Selected Stable Isotopes by Liquid-Phase Thermal Diffusion and by Chemical Exchange.  

National Technical Information Service (NTIS)

Useful applications of enriched stable nuclides are unduly restricted by high cost and limited availability. Recent research on liquid phase thermal diffusion (LTD) has resulted in practical processes for separating exp 34 S, exp 35 Cl, and exp 37 Cl in s...

W. M. Rutherford B. E. Jepson E. D. Michaels

1982-01-01

242

Heterogeneity of the Liquid Phase, and Vapor Separation in Los Azufres (Mexico) Geothermal Reservoir  

SciTech Connect

Data of chemical and isotopic composition of fluids from Los Azufres geothermal wells is interpreted in order to characterize the composition of the liquid phase, and to define the relation between this phase and fluids from steam-producing wells. Chemical and specific enthalpy data show that most wells considered are fed a mixture of steam and liquid. Thus, flashing occurs in the formation. This poses a problem on the interpretation of isotopic data, because the composition of the feeding mixture need not be representative of the composition of the liquid phase in the reservoir. Two extreme alternatives for the interpretation of isotopic data are considered. In the first alternative the composition of the total discharge is considered to be the same as that of the liquid in the reservoir. In the second alternative the feeding fluid is considered to be a mixture of the liquid phase in the reservoir and the calculated fraction of steam. In addition, this steam is assumed to separate from a much larger mass of that liquid phase at the downhole temperature. The contribution of steam is then subtracted from the total discharge to yield the composition of the liquid phase. Using data for silica concentration in total discharge and separated water, the chloride concentration in the reservoir liquid is calculated. This result is used to calculate the fraction of steam in the feeding mixture of each well. The isotopic data is then corrected as proposed for the second alternative, to yield the composition of the liquid phase. Comparison of the corrected and uncorrected isotopic values shows that the correction has an important effect only when the steam mass fraction in the feeding mixture is large (> 20%). The correction tends to reduce the dispersion of data points in a {delta} D vs {delta}{sup 18}O diagram. Points representing composition of liquid phase show an approximately linear distribution, suggesting a process of mixing of two fluids. Available data appears to rule out the possibility of mixture with local meteoric or shallow ground waters. Some spatial correlations of composition are noted. The composition of fluids produced by two steam wells corresponds to steam separated from a much larger mass of liquid. Temporal variations in the composition of fluid produced by steam well A-6 suggests that this well might be fed with steam from more than one section in the reservoir.

Nieva, D.; Quijano, L.; Garfias, A.; Barragan, R.M.; Laredo, F.

1983-12-15

243

Prediction of infinite dilution activity coefficients for systems including water based on the group contribution model with mixture-type groups  

Microsoft Academic Search

A new approach is proposed by introducing mixture-type groups to the modified universal functional activity coefficient (UNIFAC, Dortmund) model for prediction of infinite dilution activity coefficients in highly nonideal aqueous solutions. The mixture-type group means a hypothetical one that appears in a particular type of mixtures only, and is considered here to account for hydrophobic effects specially taking place in

Suojiang Zhang; Toshihiko Hiaki; Kazuo Kojima

1998-01-01

244

Liquid-liquid Phase Separation in Aerosols: Model Predictions, Laboratory and Field Observations  

NASA Astrophysics Data System (ADS)

Atmospheric aerosol particles composed of a variety of organic compounds, water, and dissolved inorganic ions exhibit changes in water content, phase state and mixing properties in response to variations in relative humidity (RH) and temperature of the environment. Liquid-liquid phase separation may occur in partially liquid aerosol particles as a consequence of changes in composition, most prominently water content. A liquid-liquid phase separation manifests the presence of limited miscibility among the solution constituents indicating significant non-ideality in the condensed phase, which is caused by unfavorable interactions between water molecules, inorganic ions, and organic compounds; especially in the presence of rather hydrophobic organics with low O:C atomic ratios. An increasing number of laboratory experiments and thermodynamic modeling studies suggest that liquid-liquid phase separation is expected to be present over a wide range of RH for typical organic:inorganic ratios of aged tropospheric aerosol. Recent data from field observations in the Los Angeles basin and other ambient observations, including droplet experiments from filter sample extracts, provide evidence for the presence of phase separations in ambient aerosol particles. We present an overview on liquid-liquid phase separation related to aerosols and organic-inorganic model systems based on thermodynamic theory, detailed calculations, laboratory experiments, and indirect evidence from field observations. There are several potentially important impacts of liquid-liquid phase separation on the distribution of semivolatile organic and inorganic compounds, the equilibration timescale of gas-particle partitioning, and consequences for particle-phase chemistry. We discuss important aspects related to the computational challenges and costs of predicting and representing phase separations in detailed physicochemical models and present a new algorithm designed for complex systems of many components.

Zuend, A.; Seinfeld, J.

2012-12-01

245

Enrichment and sensitive determination of dichlorodiphenyltrichloroethane and its metabolites with temperature controlled ionic liquid dispersive liquid phase microextraction prior to high performance liquid phase chromatography.  

PubMed

Dichlorodiphenyltrichloroethane (DDT) and its main metabolites are important environmental pollutants and have been in the focusing center. It is of great value to develop simple, rapid, sensitive and easy to operate method for monitoring them. Present work established a novel temperature controlled ionic liquid dispersive liquid phase microextraction method in combination with high performance liquid chromatography for the enrichment and determination of DDT and its metabolites. Proposed method used only ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([C(6)MIM][PF(6)]) for the enrichment and overcame the demerits of conventional single drop liquid phase microextraction and dispersive liquid-liquid microextraction. Temperature has two functions here, one is to promote the dispersing of ionic liquid into the solution and forming infinitesimal micro-drop and increasing the chance of the analytes extracted into ionic liquid phase, and the other one is to perform phase-separation. A series of factors that would affect the extraction performance was systematically investigated and optimized. The experimental results indicated that the detection limits obtained for p,p'-DDD, p,p'-DDT, o,p'-DDT and p,p'-DDE were 0.24, 0.24, 0.45, 0.24 ng mL(-1), respectively. The linear ranges for them were from 1.0 to 100 ng mL(-1), and the precisions were between 3.8% and 6.7% (n=6). The proposed method was validated with four real-world samples and excellent results were achieved. PMID:19733736

Bai, Huahua; Zhou, Qingxiang; Xie, Guohong; Xiao, Junping

2009-09-28

246

Surfactant-enhanced carbon regeneration in liquid-phase application  

SciTech Connect

In surfactant-enhanced carbon regeneration, a concentrated surfactant solution is passed over spent activated carbon to desorb the solutes in an in-situ process. The solutes solubilize into micelles in the regenerant solution. Residual adsorbed surfactant can be removed by a water flush. In this study, phenol is the solute and sodium dodecyl sulfate is the anionic surfactant used. Previous studies have measured the ability of the regenerant to remove the solute from the carbon. This study presents the breakthrough curves for subsequent adsorption cycles following the regeneration. The reduction of the effective carbon adsorption capacity is less if a higher regenerant concentration of surfactant, more pore volumes of regenerant, or more pore volumes of water flush solution are used. Effective adsorption capacities of over 50% of that on virgin carbon were observed on regenerated carbon.

Bhummasobhana, A.; Osuwan, S.; Shooshat, B. [Chulalongkorn Univ., Bangkok (Thailand)] [and others

1996-03-01

247

Liquid phase epitaxial growth of GaAs  

SciTech Connect

Research into new semiconductor materials for measurement of electromagnetic radiation over a wide range of energies has been an active field for several decades. There is a strong desire to identify and develop new materials which can lead to improved detectors. Such devices are expected to solve problems that cannot be solved using the semiconductor materials and device structures which have been traditionally used for radiation detection. In order for a detector which is subjected to some type of irradiation to respond, the radiation must undergo an interaction with the detector. The net result of the radiation interaction in a broad category of detectors is the generation of mobile electric charge carriers (electrons and/or holes) within the detector active volume. This charge is collected at the detector contacts and it forms the basic electrical signal. Typically, the collection of the charge is accomplished through the imposition of an electric field within the detector which causes the positive and/or negative charges created by the radiation to flow in opposite directions to the contacts. For the material to serve as a good radiation detector, a large fraction (preferably 100%) of all carriers created by the interacting incident radiation must be collected. Charge trapping by deep level impurities and structural defects can seriously degrade detector performance. The focus of this thesis is on far infrared and X-ray detection. In X-ray detector applications of p-I-n diodes, the object is to measure accurately the energy distribution of the incident radiation quanta. One important property of such detectors is their ability to measure the energy of individual incident photons with high energy resolution.

Wynne, D.I. [Univ. of California, Berkeley, CA (United States). Materials Science and Mineral Engineering]|[Lawrence Berkeley National Lab., CA (United States)

1997-10-01

248

Spectral absorption coefficient of photosynthetically active pigments in the equatorial Pacific Ocean (165°11 150°W)  

NASA Astrophysics Data System (ADS)

Spectral absorption coefficients of total particulate material and detritus were measured throughout the euphotic zone along the equator between 165°E and 150°W and during time-series for each of these two longitudes in October 1994 (JGOFS-FLUPAC cruise). The sum of pigments obtained by spectrofluorometry (tChla=DV-chla+Chla) was used for normalization (and was also compared to fluorometric and HPLC measurements as an intercalibration study). In order to assess the specific absorption coefficient of photosynthetically active pigments (aps) from the pigment-specific absorption coefficient for phytoplankton ( aph*), we made a multiple regression analysis of measured phytoplankton absorption spectra onto published in vivo spectra of pure pigments. This made it possible to calculate the concentrations of photoprotective carotenoids (tPPC) when HPLC measurements were not available and thus to subtract their contribution to absorption from the total phytoplanktonic absorption coefficient ( aph). Methodological uncertainties in both coefficients used for calculating absorption coefficients and in pigment measurements are discussed. Pigments and absorption measurements made during the cruise enabled us to describe two typical trophic regimes in the equatorial Pacific ocean: oligotrophic waters of the "warm pool" west of 170°W and high-nutrient, low-chlorophyll waters (HNLC) of the upwelling east of 170°W. The vertical decreasing gradient of aph* from the surface to the deep chlorophyll maximum (DCM) was due to a high tPPC/tChla ratio at the surface and was higher in the oligotrophic (0.14-0.065 m 2 mg (tChl a) -1 biomass dominated by Prochlorococcus, rich in zeaxanthin) than in the mesotrophic area (0.07-0.06 m2 mg (tChl a)-' biomass dominated by picoeucaryotes). Below the DCM, aph* reached a similar minimum value in both oligotrophic and mesotrophic areas. a*ps varied less than a*ph from the surface layer to the DCM in both oligotrophic and mesotrophic areas. The difference in a*ph and a*ps from west to east of the transect could be interpreted as a shift in the phytoplankton composition, with a dominance of procaryotes in the west and a dominance of eucaryotes in the upwelling area. Higher aps in well-lit typical oligotrophic waters indicated that phytoplankton communities dominated by Proclorococcus might be more efficient for capturing light usable for photosynthesis than those present in the HNLC situation.

Dupouy, C.; Neveux, J.; An´, J. M.

249

Analysis of stimulus-related activity in rat auditory cortex using complex spectral coefficients  

PubMed Central

The neural mechanisms of sensory responses recorded from the scalp or cortical surface remain controversial. Evoked vs. induced response components (i.e., changes in mean vs. variance) are associated with bottom-up vs. top-down processing, but trial-by-trial response variability can confound this interpretation. Phase reset of ongoing oscillations has also been postulated to contribute to sensory responses. In this article, we present evidence that responses under passive listening conditions are dominated by variable evoked response components. We measured the mean, variance, and phase of complex time-frequency coefficients of epidurally recorded responses to acoustic stimuli in rats. During the stimulus, changes in mean, variance, and phase tended to co-occur. After the stimulus, there was a small, low-frequency offset response in the mean and modest, prolonged desynchronization in the alpha band. Simulations showed that trial-by-trial variability in the mean can account for most of the variance and phase changes observed during the stimulus. This variability was state dependent, with smallest variability during periods of greatest arousal. Our data suggest that cortical responses to auditory stimuli reflect variable inputs to the cortical network. These analyses suggest that caution should be exercised when interpreting variance and phase changes in terms of top-down cortical processing.

Krause, Bryan M.

2013-01-01

250

Relation coefficient between maximal usable and critical frequency according to IRI for Asian equatorial sector at low solar activity  

NASA Astrophysics Data System (ADS)

The coefficient m in the expression relating the maximum usable frequency to the critical frequency (for use in radio forecasting and calculating radio pathways and network parameters) are determined for the Asian equatorial sector on the basis of the corresponding IRI/79 profiles and published observatorial data obtained at Hanoi, Ho Chi Minh City, Kodaikanal, and Ahmedabad during low-solar-activity periods in March, June, September, and December. The results are presented in graphs, and it is found that the equatorial m values exceed those reported for midlatitudes (Serafimov and Tafradjieva, 1962), increase with proximity to the magnetic equator, and exhibit a poorly defined maximum in winter.

Serafimov, K. B.; Kutiev, I. S.; Hoang, L. T.; Karadimov, M. D.

251

Liquid phase epitaxial growth and characterization of germanium far infrared blocked impurity band detectors  

SciTech Connect

Germanium Blocked Impurity Band (BIB) detectors require a high purity blocking layer (< 10{sup 13} cm{sup -3}) approximately 1 mm thick grown on a heavily doped active layer ({approx} 10{sup 16} cm{sup -3}) approximately 20 mm thick. Epilayers were grown using liquid phase epitaxy (LPE) of germanium out of lead solution. The effects of the crystallographic orientation of the germanium substrate on LPE growth modes were explored. Growth was studied on substrates oriented by Laue x-ray diffraction between 0.02{sup o} and 10{sup o} from the {l_brace}111{r_brace} toward the {l_brace}100{r_brace}. Terrace growth was observed, with increasing terrace height for larger misorientation angles. It was found that the purity of the blocking layer was limited by the presence of phosphorus in the lead solvent. Unintentionally doped Ge layers contained {approx}10{sup 15} cm{sup -3} phosphorus as determined by Hall effect measurements and Photothermal Ionization Spectroscopy (PTIS). Lead purification by vacuum distillation and dilution reduced the phosphorus concentration in the layers to {approx} 10{sup 14} cm{sup -3} but further reduction was not observed with successive distillation runs. The graphite distillation and growth components as an additional phosphorus source cannot be ruled out. Antimony ({approx}10{sup 16} cm{sup -3}) was used as a dopant for the active BIB layer. A reduction in the donor binding energy due to impurity banding was observed by variable temperature Hall effect measurements. A BIB detector fabricated from an Sb-doped Ge layer grown on a pure substrate showed a low energy photoconductive onset ({approx}6 meV). Spreading resistance measurements on doped layers revealed a nonuniform dopant distribution with Sb pile-up at the layer surface, which must be removed by chemomechanical polishing. Sb diffusion into the pure substrate was observed by Secondary Ion Mass Spectroscopy (SIMS) for epilayers grown at 650 C. The Sb concentration at the interface dropped by an order of magnitude over {approx} 1.5 {micro}m. Layers grown at 550 C did not show significant Sb diffusion. Sn doped In{sub 2}O{sub 3} (ITO) was studied for use in far infrared transparent low temperature contacts for BIB arrays. It was found that {approx}100 nm of ITO deposited on Ge remains electrically conducting at 4 K and is {approx}90% transparent in the far infrared. ITO should be suitable for passivating contacts to Ge BIB arrays.

Bandaru, Jordana

2001-05-12

252

On Implicit Active Constraints in Linear Semi-Infinite Programs with Unbounded Coefficients  

SciTech Connect

The concept of implicit active constraints at a given point provides useful local information about the solution set of linear semi-infinite systems and about the optimal set in linear semi-infinite programming provided the set of gradient vectors of the constraints is bounded, commonly under the additional assumption that there exists some strong Slater point. This paper shows that the mentioned global boundedness condition can be replaced by a weaker local condition (LUB) based on locally active constraints (active in a ball of small radius whose center is some nominal point), providing geometric information about the solution set and Karush-Kuhn-Tucker type conditions for the optimal solution to be strongly unique. The maintaining of the latter property under sufficiently small perturbations of all the data is also analyzed, giving a characterization of its stability with respect to these perturbations in terms of the strong Slater condition, the so-called Extended-Nuernberger condition, and the LUB condition.

Goberna, M. A., E-mail: mgoberna@ua.es [Alicante University, Dep. of Statistics and Operations Research (Spain); Lancho, G. A., E-mail: lanchoga@mixteco.utm.mx [Universidad Tecnologica de Mixteca, Instituto de Fisica y Matematicas (Mexico); Todorov, M. I., E-mail: maxim.todorov@udlap.mx [UDLA, Dep. of Physics and Mathematics (Mexico); Vera de Serio, V. N., E-mail: vvera@uncu.edu.ar [Universidad Nacional de Cuyo, Facultad de Ciencias Economicas, Instituto de Ciencias Basicas (Argentina)

2011-04-15

253

[Anaerobic biodegradation of pentachlorophenol (PCP) in solid-liquid phase of contaminated sediment slurry].  

PubMed

The study showed that after inoculating 10 g x kg(-1) anaerobic dechlorinated granular sludge (ADGS) for 31 days, the biodegradation rate of pentachlorophenol (PCP) in solid-liquid phase of contaminated sediment slurry was up to 98.9%, with an average of 8.0 mg x kg(-1) x d(-1), while that of the control was only 4.4 mg x kg(-1) x d(-1). As the regulation factors in slurry remediation, organic solvent, co-substrate and surfactant had different effects on PCP degradation. The addition of ethanol could enhance the desorption and degradation of PCP, the degradation rate being up to 54.3 mg x kg(-1) d(-1) within 4 days, while the addition of co-substrate and non-ionic surfactant EGME (ethylene glycol monobutyl-ether) inhibited the PCP degradation in solid-liquid phase of slurry. PMID:16011167

Tang, Quan; Xu, Xiangyang; Zhu, Youwei

2005-04-01

254

Evaluation of multiplexed PCR and liquid-phase array for identification of respiratory fungal pathogens.  

PubMed

Invasive fungal infections are the cause of serious morbidity and high mortality in immunocompromised patients. Early laboratory diagnostic options remain limited; however, rapid detection and accurate identification may improve outcome. Herein, multiplexed PCR followed by liquid-phase array was evaluated for detection and identification of common respiratory fungal pathogens, including Aspergillus fumigatus, Rhizopus microsporus, Scedosporium apiospermum and Fusarium solani. The limit of detection ranged 0.1-1 ng of DNA, depending on the fungus being tested. Primer cross-reactivity was seen for some fungi: Aspergillus flavus primers detected Aspergillus oryzae; Scedosporium apiospermum primers detected Paecilomyces lilacinus, and Aspergillus terreus primers detected S. apiospermum. PCR followed by liquid-phase array is potentially useful for the identification of clinically relevant fungal pathogens. PMID:22435876

Buelow, Daelynn R; Gu, Zhengming; Walsh, Thomas J; Hayden, Randall T

2012-10-01

255

Weak interaction between inhibition peptides and a soluble receptor of fusion protein in the liquid phase.  

PubMed

Fluorescence polarization analysis (FPA) of a liquid-phase method was carried out with a glycosylphosphatidylinositol (GPI) anchored membrane receptor bone marrow stromal cell antigen 1 (BST-1, CD157) as a model receptor for medical screening. A soluble receptor, BST1-Fc, was prepared by fusing the extracellular domain of BST-1 and the Fc region of human immunoglobulin G (IgG). The binding curves of BST1-Fc with a fluorescently labeled ligand peptide, or its three derivatives, were developed using ordinary FPA in the liquid phase. The obtained dissociation constants (Kd) were comparable with those reported as measured with SPR of a solid-phase method, except for one derivative peptide with Kd larger than 7000 nM. Competitive FPA was carried out, and it was demonstrated that a very weak interaction, which would be difficult to detect with SPR or other solid-phase methods, could be analyzed with both ordinary and competitive FPA. PMID:16966807

Shimizu, Masafumi; Yoshiaki, Yukuya; Sato, Atsushi; Tsuruoka, Makoto

2006-09-01

256

Phase transitions and transient liquid-phase sintering in calcium-substituted lanthanum chromite  

SciTech Connect

This paper investigates sintering and phase transitions of La{sub 0.7}Ca{sub x}CrO{sub 3} (0.25 {le} x {le} 0.35), a material useful as electrical interconnections in solid oxide fuel cells. Heating of the quenched, metastable single-phase chromite resulted in exsolution of CaCrO{sub 4} due to Ca solubility limitations below 1,200 C. A transient liquid phase formed between 850 and 1,000 C as the CaCrO{sub 4} melted, causing partial densification in materials having 0.25 < x < 0.30. A slight increase in Ca content induced an additional liquid-phase sintering event, likely due to melting of Ca{sub 3}(CrO{sub 4}){sub 2}, which facilitated near-complete densification by 1,250 C. After enhancing sintering, the secondary phases redissolved into the chromite.

Chick, L.A.; Liu, J.; Stevenson, J.W.; Armstrong, T.R.; McCready, D.E.; Maupin, G.D.; Coffey, G.W.; Coyle, C.A. [Pacific Northwest National Lab., Richland, WA (United States). Materials and Chemical Sciences Dept.

1997-08-01

257

On the electrostrictive mechanism of nanosecond-pulsed breakdown in liquid phase  

NASA Astrophysics Data System (ADS)

In this study we have studied the initial stage of the nanosecond-pulsed discharge development in liquid phase. Modelling predicts that in the case of fast rising strong nonhomogeneous electric fields in the vicinity of high-voltage pin electrode a region saturated with nanoscale non-uniformities may be developed. This phenomenon is attributed to the electrostriction mechanisms and may be used to explain development of breakdown in liquid phase. In this work, schlieren method was used in order to demonstrate formation of negative pressure region in liquids with different dielectric permittivity constants: water, ethanol and ethanol-water mixture. It is shown that this density perturbation, formed at the raising edge of the high-voltage pulse, is followed by a generation of a shock wave propagating with the speed of sound away from the electrode, with negative pressure behind it.

Seepersad, Yohan; Pekker, Mikhail; Shneider, Mikhail N.; Dobrynin, Danil; Fridman, Alexander

2013-04-01

258

Effective Liquid-Phase Exfoliation and Sodium Ion Battery Application of MoS2 Nanosheets.  

PubMed

Two-dimensional (2D) molybdenum disulfide (MoS2) has been taken much attention for various applications, such as catalyst, energy storage, and electronics. However, the lack of effective exfoliation methods for obtaining 2D materials in a large quantity has been one of the technical barriers for the real applications. We report a facile liquid-phase exfoliation method to improve the exfoliation efficiency for single-layer MoS2 sheets in 1-methyl-2-pyrrolidinone (NMP) with a sodium hydroxide (NaOH) assistant. The concentration of the exfoliated MoS2 nanosheets was greatly improved compared to that achieved with conventional liquid-phase exfoliation methods using NMP solvent. We demonstrate stable operation of sodium-ion battery by using the exfoliated MoS2 and MoS2-rGO composite as anode materials. PMID:24773226

Bang, Gyeong Sook; Nam, Kwan Woo; Kim, Jong Yun; Shin, Jongwoo; Choi, Jang Wook; Choi, Sung-Yool

2014-05-28

259

Stabilization of copper catalysts for liquid-phase reactions by atomic layer deposition.  

PubMed

Atomic layer deposition (ALD) of an alumina overcoat can stabilize a base metal catalyst (e.g., copper) for liquid-phase catalytic reactions (e.g., hydrogenation of biomass-derived furfural in alcoholic solvents or water), thereby eliminating the deactivation of conventional catalysts by sintering and leaching. This method of catalyst stabilization alleviates the need to employ precious metals (e.g., platinum) in liquid-phase catalytic processing. The alumina overcoat initially covers the catalyst surface completely. By using solid state NMR spectroscopy, X-ray diffraction, and electron microscopy, it was shown that high temperature treatment opens porosity in the overcoat by forming crystallites of ?-Al2 O3 . Infrared spectroscopic measurements and scanning tunneling microscopy studies of trimethylaluminum ALD on copper show that the remarkable stability imparted to the nanoparticles arises from selective armoring of under-coordinated copper atoms on the nanoparticle surface. PMID:24282166

O'Neill, Brandon J; Jackson, David H K; Crisci, Anthony J; Farberow, Carrie A; Shi, Fengyuan; Alba-Rubio, Ana C; Lu, Junling; Dietrich, Paul J; Gu, Xiangkui; Marshall, Christopher L; Stair, Peter C; Elam, Jeffrey W; Miller, Jeffrey T; Ribeiro, Fabio H; Voyles, Paul M; Greeley, Jeffrey; Mavrikakis, Manos; Scott, Susannah L; Kuech, Thomas F; Dumesic, James A

2013-12-16

260

Computation of solid/liquid phase change including free convection - Comparison with data  

NASA Technical Reports Server (NTRS)

A computational model is presented for solid/liquid phase-change energy transport including free convection fluid flow in the liquid phase. The computational model considers the velocity components of all nonliquid control volumes to be zero but fully solves the coupled mass-momentum problem within the liquid. The thermal energy model includes the entire domain and employs an enthalpy-like model and a recently developed method for handling the phase-change interface nonlinearity. Convergence studies are performed and comparisons made with experimental data for two different problems. Grid independence is achieved, and the comparison with experimental data indicates excellent quantitative prediction of the melt fraction evolution. Qualitative data are also provided as velocity vector and isotherm plots. The computational costs incurred are quite low by comparison with other models.

Schneider, G. E.

1990-01-01

261

Energy efficient thermal management of electronic components using solid-liquid phase change materials  

Microsoft Academic Search

Energy efficiency is becoming a key issue in the development of thermal management devices. To this end, thermal performance of plate fin and pin fin heat sinks incorporating a solid-liquid phase change material (PCM) has been evaluated, under periodic power inputs simulating actual heating conditions. Experiments were performed using Wood's metal (50Bi\\/27Pb\\/13Sn\\/10Cd, melting point: 70.0°C) under forced convection in a

Dong-won Yoo; Yogendra K. Joshi

2004-01-01

262

On the mechanisms of micropipe and macrodefect transformation in SiC during liquid phase treatment  

Microsoft Academic Search

The evolution of hollow-core defects present in vapor phase grown SiC bulk crystals during subsequent liquid phase epitaxial treatment has been investigated in a wide range of supersaturation conditions. Hollow macrodefects were found to decompose into a number of micropipes (MP) already at supersaturations close to zero. The elimination of pure screw-dislocation based MP requires a higher supersaturation. Micropipes were

B. M Epelbaum; D Hofmann

2001-01-01

263

Heterogeneous reactive extraction for secondary butyl alcohol liquid phase synthesis: Microkinetics and equilibria  

Microsoft Academic Search

The reaction kinetics for the liquid phase synthesis of a racemic mixture of the secondary butyl alcohols (SBA) from linear butene isomers (1-butene (1B); cis-2-butene (c2B); trans-2-butene (t2B)) and water (W) using a macroporous sulfonic acid ion exchange resin as catalyst were determined experimentally in a multiphase CSTR in the temperature range 39–433K at 6–8MPa. This range of pressures is

Bernhard Pfeuffer; Ulrich Kunz; Ulrich Hoffmann; Thomas Turek; Detlef Hoell

2011-01-01

264

Microgravity Studies of Liquid-Liquid Phase Transitions in Alumina-Yttria Melts  

NASA Technical Reports Server (NTRS)

The scientific objective of this research is to increase the fundamental knowledge base for liquid- phase processing of technologically important oxide materials. The experimental objective is to define conditions and hardware requirements for microgravity flight experiments to test and expand the experimental hypotheses that: 1. Liquid phase transitions can occur in undercooled melts by a diffusionless process. 2. Onset of the liquid phase transition is accompanied by a large change in the temperature dependence of melt viscosity. Experiments on undercooled YAG (Y3A15012)- and rare earth oxide aluminate composition liquids demonstrated a large departure from an Arrhenian temperature dependence of viscosity. Liquid YAG is nearly inviscid at its 2240 K melting point. Glass fibers were pulled from melts undercooled by ca. 600 K indicating that the viscosity is on the order of 100 Pans (1000 Poise) at 1600 K. This value of viscosity is 500 times greater than that obtained by extrapolation of data for temperatures above the melting point of YAG. These results show that the liquids are extremely fragile and that the onset of the highly non-Arrhenian viscosity-temperature relationship occurs at a temperature considerably below the equilibrium melting point of the solid phases. Further results on undercooled alumina-yttria melts containing 23-42 mole % yttrium oxide indicate that a congruent liquid-liquid phase transition occurs in the undercooled liquids. The rates of transition are inconsistent with a diffusion-limited process. This research is directed to investigation of the scientifically interesting phenomena of polyamorphism and fragility in undercooled rare earth oxide aluminum oxide liquids. The results bear on the technologically important problem of producing high value rare earth-based optical materials.

Guynes, Buddy (Technical Monitor); Weber, Richard; Nordine, Paul

2004-01-01

265

Gravity and configurational energy induced microstructural changes in liquid phase sintering  

NASA Technical Reports Server (NTRS)

Experiments were performed with W-Ni-Fe heavy alloys in order to measure the microstructural changes vs. position that occur in liquid-phase sintering under normal gravity. The experimentally observed segregation is less than the calculated equilibrium segregation due to the retarding effect from the rigid solid skeleton formed during sintering. These results improve understanding of microstructure, mechanical properties, component shape, and dimensional stability benefits that may be realized from low-gravity sintering.

Kipphut, C. M.; Bose, A.; Farooq, S.; German, R. M.

1988-01-01

266

Mono-crystalline silicon strips grown by liquid phase epitaxy for photovoltaic applications  

Microsoft Academic Search

We have studied epitaxial lateral overgrowth of p-type silicon by Liquid Phase Epitaxy (LPE) on n-type (111) silicon substrates from a Si\\/In melt. The substrate had a silicon dioxide mask with a set of parallel opening windows for seed lines which were aligned along a [211]direction. The growth parameters, morphology and electrical properties of the grown crystal were studied. Two

Bo Li; Adrian H. Kitai

2010-01-01

267

Deposition of gold nanoparticles on liquid phase epitaxy grown garnet films and Faraday rotation enhancement  

NASA Astrophysics Data System (ADS)

Plasmon resonance induced Faraday rotation enhancement in liquid phase epitaxy grown garnet films with gold nanoparticles on their surfaces is discussed. Experimental results are presented, which reveal stronger Faraday rotation enhancement for gold nanoparticles obtained by the annealing of thicker gold films evaporated on garnet film surfaces. This stronger Faraday rotation enhancement can be attributed to larger dimensions and separations of gold nanoparticles, which increase the extent of penetration of plasmon resonance induced electric fields into garnet films.

Lang, G. S.; Bowen, D.; Krafft, C.; Mayergoyz, I. D.

2013-05-01

268

Selective edge-growth with controlled ferroelectric-domain structure by liquid-phase epitaxy  

Microsoft Academic Search

A new liquid-phase epitaxy technique for achieving selective three-dimensional growth with controlled ferroelectric-domain structures is proposed utilizing the “edge-growth” phenomenon and poling selectivity depending on the substrate-surface orientation. LiNb1?xTaxO3 thin films with periodically switching spontaneous polarization were successfully formed on X-cut LiNbO3 substrates by modulating the surface orientation.

Tatsuo Kawaguchi; Minoru Imaeda; Tsuguo Fukuda

1998-01-01

269

Growth of a Large GaN Single Crystal Using the Liquid Phase Epitaxy (LPE) Technique  

Microsoft Academic Search

We grew a 12× 5× 0.8 mm GaN single crystal using the liquid phase epitaxy (LPE) method with Na flux. This GaN single crystal was grown on a 3 mum-thick GaN thin film synthesized on sapphire using the metal organic chemical vapor deposition (MOCVD) method. It grew in a polyhedral form larger than the MOCVD-GaN substrate. Results indicate that a

Fumio Kawamura; Tomoya Iwahashi; Kunimichi Omae; Masanori Morishita; Masashi Yoshimura; Yusuke Mori; Takatomo Sasaki

2003-01-01

270

Growth of metal oxide thin films from aqueous solution by liquid phase deposition method  

Microsoft Academic Search

The deposition process of iron oxyhydroxide (?-FeOOH) from aqueous solution system of FeOOH–NH4F·HF (aq.) with H3BO3 by the liquid phase deposition (LPD) method has been investigated. The effect of initial concentration in the treatment solution and reaction time on microstructure and orientation of the deposited films were studied by means of scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission

Shegehito Deki; Naohiro Yoshida; Yoshihiko Hiroe; Kensuke Akamatsu; Minoru Mizuhata; Akihiko Kajinami

2002-01-01

271

Liquid Phase Chemical Enhanced Oxidation on AlGaAs and Its Application  

Microsoft Academic Search

A new method named the liquid phase chemical enhanced oxidation (LPCEO) technique has been proposed for the oxidation of aluminum gallium arsenide (AlGaAs) near room temperature. The initial stage of AlGaAs oxidation by this method has been investigated. The native oxide film composition is determined on the basis of the results of Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS)

Kuan-Wei Lee; Yeong-Her Wang; Mau-Phon Houng

2004-01-01

272

Liquid Phase Chemical-Enhanced Oxidation for GaAs Operated Near Room Temperature  

Microsoft Academic Search

A new chemical enhanced oxidation method for gallium arsenide (GaAs) in liquid phase near room temperature (40°C 70°C) is proposed and investigated. Featureless oxide layers with good uniformity and reliability can be grown efficiently on GaAs without any extra energy source. A relatively high oxidation rate (~=1000 Å\\/h), about 50 times higher than that obtained during oxidation in boiling water

Hwei-Heng Wang; Chien-Jung Huang; Yeong-Her Wang; Mau-Phon Houng

1998-01-01

273

GaAs MOSFETs fabrication with a selective liquid phase oxidized gate  

Microsoft Academic Search

The N-channel depletion-mode GaAs MOSFETs with a liquid phase chemical enhanced selective gate oxide grown at low temperature are demonstrated. The proposed selective oxidation method makes the fabrication process of GaAs MOSFETs more reliable and self side-wall passivation possible. The fabricated GaAs MOSFETs exhibit current-voltage characteristics with complete pinch-off and saturation characteristics. The 2 ?m gate-length MOSFETs with a gate

Jau-Yi Wu; Hwei-Heng Wang; Yeong-Her Wang; Mau-Phon Houng

2001-01-01

274

Properties of GaAs Oxides Prepared by Liquid Phase Chemical-Enhanced Technique  

Microsoft Academic Search

The properties of GaAs oxides prepared by liquid phase chemical-enhanced oxidation (LPCEO) technique are investigated. The refractive indices of the oxide films appear to increase with oxidation time, and can be well controlled by the oxidation procedures. It has been found that the accumulation of As compounds within the oxides is the origin for the phenomena. Based on the current-voltage

Hwei-Heng Wang; Dei-Wei Chou; Yeong-Her Wang; Mau-Phon Houng

1999-01-01

275

A macroporous silicon field effect sensing system for liquid phase solvent detection  

Microsoft Academic Search

Integration of electrical and fluidic systems for the design and fabrication of a system-on-chip (SOC) capable of sensing various liquid phase solvents is reported. A monolithic integration strategy makes use of macroporous silicon (MPS) as a gateway to interface the electrical and fluidic domains. In doing this, the MPS material, acting as a sensing membrane, is used in a flow-through

Jeffrey P. Clarkson; Philippe M. Fauchet; Vimalan Rajalingam; Karl D. Hirschman

2005-01-01

276

Transient-liquid-phase (TLP) bonding of aluminum trioxide using niobium-based multilayer interlayers  

Microsoft Academic Search

Transient-liquid-phase (TLP) bonding was used to join high-strength, high-purity Al2O3 ceramic. This method uses a multilayer interlayer (B\\/A\\/B sandwich structure), which forms thin transient-liquid layers between the Al2O3 and the refractory core layer (A), then isothermally solidifies through a diffusive mechanism. The presence of thin liquid layers allow interfacial gaps and voids to be filled, while allowing bonding times comparable

Sung Moo Hong

2009-01-01

277

A novel micro-well array chip for liquid phase biomaterial processing and detection  

Microsoft Academic Search

This paper presents a novel micro-well array chip fabricated by micromachining and CMOS technology for biomedical application. The chip is designed to provide multi-function for liquid phase DNA or protein sample processing and detection, its function and structure includes heating, cooling, temperature sensing, vibration agitation, control circuits, array of micro-wells, and a transparent cover with liquid seal at each well.

Henry J. H. Chen; Tsai Fen Chen; Star R. S. Huang; Jeng Gong; J. C Li; Wei Chen Chen; T. H. Hseu; Ian C. Hsu

2003-01-01

278

Catalytic liquid-phase oxidation of aqueous phenol solutions in a trickle-bed reactor  

Microsoft Academic Search

Aqueous-phase deep oxidation at comparatively low temperatures and pressures made possible by the use of heterogeneous catalysts is a promising technique for the destruction of organic water pollutants. Catalytic liquid-phase oxidation of aqueous phenol solutions was investigated in an isothermal trickle-bed reactor at T = 403–423 K and oxygen partial pressure of 7 bar. The results obtained in the presence

Albin Pintar; Gorazd Ber?i?; Janez Levec

1997-01-01

279

Trickle-bed reactor models for systems with a volatile liquid phase  

Microsoft Academic Search

A significant number of gas–liquid–solid catalyzed reactions in the petroleum processing and chemical industries are carried out in trickle-bed reactors under conditions where substantial volatilization of the liquid phase can occur. A review of the limited literature on experiments and models for trickle-bed reactor systems with volatile liquids is presented first. A rigorous model for the solution of the reactor

M. R. Khadilkar; P. L. Mills; M. P. Dudukovic

1999-01-01

280

Sintering of silicon-containing aluminum fibers in the presence of a liquid phase  

Microsoft Academic Search

The present authors carried out an investigation into the sintering of 40-#m-diameter AK0.9 alloy (AI0.9 wt. % Si, total impurities less than 0.03%) fibers, which demonstrated that good-quality CPSs from fibers of this composition can be produced by sintering in the presence of a liquid phase. To prepare specimens, 2to 3-ram-long fibers were poured into a quartz tube of 5-

V. L. Barantsevich; B. N. Veretennikov; S. I. Opryshko; Yu. P. Solodov; E. S. Yatsenko

1981-01-01

281

Liquid phase oxidation of limonene catalyzed by palladium supported on hydrotalcites  

Microsoft Academic Search

Palladium supported on copper–magnesium–aluminium hydrotalcites (HTs) were prepared by using coprecipitation and impregnation techniques. The different palladium\\/hydrotalcites solid catalysts were tested in the liquid phase oxidation of pure limonene using molecular oxygen as the sole oxidant agent. Both palladium and copper were found to influence the conversion versus reaction time profile of limonene oxidation. A chain reaction mechanism is proposed

Juan Bussi; Alejandro López; Francisco Peña; Pablo Timbal; Daniel Paz; Daniel Lorenzo; Eduardo Dellacasa

2003-01-01

282

Liquid phase epitaxial growth of InAs1-xSbx on GaSb  

Microsoft Academic Search

Reported here, for the first time, is the lattice matched growth of InAs1-xSbx on GaSb. The thermodynamic incompatibility of the system, i.e., the strong tendency for the In-As-Sb liquid to dissolve the GaSb substrate, was solved via a novel liquid phase epitaxial growth technique. Liquid compositions for lattice matching conditions have been determined in the 400-600°C range. Epitaxial growth has

E. R. Gertner; A. M. Andrews; L. O. Bubulac; D. T. Cheung; M. J. Ludowise; R. A. Riedel

1979-01-01

283

High dielectric constant nickel-doped titanium oxide films prepared by liquid-phase deposition  

NASA Astrophysics Data System (ADS)

The electrical characteristics of nickel-doped titanium oxide films prepared by liquid-phase deposition on p-type (100) silicon substrate were investigated. The aqueous solutions of ammonium hexafluorotitanate and boric acid were used as precursors for the growth of titanium oxide films and the dielectric constant is 29. The dielectric constant can be improved to 94 by nickel doping at the thermal annealing at 700 °C in nitrous oxide.

Lee, Ming-Kwei; Yen, Chih-Feng; Fan, Cho-Han

2014-03-01

284

Processing and microstructural development in liquid phase sintered and pure TiBâ ceramics  

Microsoft Academic Search

The fabrication of TiBâ ceramics with high fracture strength and toughness requires that grain growth and the development of secondary phase(s) be controlled. Liquid phase assisted densification with nickel-bearing metallic additives allows one to achieve high densities and final grain sizes that are comparable to the particle size of the starting commercial TiBâ powders. To gain further reduction in TiBâ

P. Angelini; P. F. Becher; J. Bentley; J. Brynestad; M. K. Ferber; C. B. Finch; P. S. Sklad

1984-01-01

285

Liquid-phase hybridization based PCR-ELISA for detection of genetically modified organisms in food  

Microsoft Academic Search

Polymerase chain reaction (PCR) screening for presence of transgenic components in food is becoming a routine method in modern food analysis. To develop a high throughput method for quantitation of the PCR products is needed for automatic industry analysis. Here we described an in situ liquid-phase hybridization (LPH) for PCR-enzyme linked immunoabsorbent assays (PCR-ELISA) that was widely used for quantitation

G. Liu; W. Su; Q. Xu; M. Long; J. Zhou; S. Song

2004-01-01

286

Three-body interactions and solid-liquid phase equilibria: Application of a molecular dynamics algorithm  

Microsoft Academic Search

The effect of three-body interactions on the solid-liquid phase boundaries of argon, krypton, and xenon is investigated via a novel technique that combines both nonequilibrium and equilibrium molecular dynamics. The simulations involve the evaluation of two- and three-body forces using accurate two-body and three-body intermolecular potentials. The effect of three-body interactions is to substantially increase the coexistence pressure and to

Liping Wang; Richard J. Sadus

2006-01-01

287

Catalytic applications of MCM-41 with different pore sizes in selected liquid phase reactions  

Microsoft Academic Search

A series of MCM-41 with pore diameters in 20–90Å range was prepared and the effects of pore size on liquid phase reactions of epoxidation, etherification, and esterification were investigated after Ti-grafting, immobilization of Mn–salen complex, and monolayer adsorption of SO3H were performed on the host materials, respectively. Amount of functionalized species increased with the pore diameters of MCM-41, but it

J. S Choi; D. J Kim; S. H Chang; W. S Ahn

2003-01-01

288

On the size dependences of the crystal-liquid phase transition parameters  

NASA Astrophysics Data System (ADS)

A comparatively simple method is proposed for calculating the size dependences of the latent heat, volume jumps, and the interfacial surface energy for the crystal-liquid phase transition proceeding from the results of experiments (real or computer) on determining size dependences of the melting point and the crystallization temperature. The method is tested on the basis of computer simulation data for copper, gold, aluminum, and nickel nanoparticles and experimental data for tin.

Magomedov, M. N.

2014-05-01

289

Surface Modification of Poly(tetrafluoroethylene) Microporous Membranes by Acrylic Acid Liquid-Phase Graft Copolymerization  

Microsoft Academic Search

Air plasma-pretreated polytetrafluoroethylene (PTFE) films were subjected to further surface modification by liquid-phase graft copolymerization with acrylic acid monomer (AAc). The surface compositions and microstructures of the modified films were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). An exterior graft copolymerization of AAc on the PTFE fiber was indicated by the SEM photographs. The XPS results

Xuyun Wang; Xuehai Yue; Xin Wang; Qingjie Guo

2010-01-01

290

Surface Modification of Poly(tetrafluoroethylene) Microporous Membranes by Acrylic Acid Liquid-Phase Graft Copolymerization  

Microsoft Academic Search

Air plasma-pretreated poly(tetrafluoroethylene) (PTFE) films were subjected to further surface modification by liquid-phase graft copolymerization with acrylic acid monomer (AAc). The surface compositions and microstructures of the modified films were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). An exterior graft copolymerization of AAc on the PTFE fiber was indicated by the SEM photographs. The XPS results

Xuyun Wang; Xuehai Yue; Xin Wang; Qingjie Guo

2011-01-01

291

Solid-liquid phase equilibria at 727 °C in the ternary system Fe-Mg-Si  

Microsoft Academic Search

The solid-liquid phase equilibria in the Fe-Mg-Si ternary system were experimentally investigated at 727 °C by two complementary\\u000a approaches: reaction to equilibrium of Fe-Mg-Si powder mixtures and growth of reaction zones at the interface of diffusion\\u000a couples. X-ray powder diffraction, optical metallography (OM), scanning electron microscopy (SEM), and electron probe microanalysis\\u000a (EPMA) were used to characterize the phases formed in

D. Pierre; M. Peronnet; F. Bosselet; J. C. Viala; J. Bouix

2000-01-01

292

MODELING OF A LIQUID ENTRAINED REACTOR FOR LIQUID PHASE METHANOL SYNTHESIS PROCESS  

Microsoft Academic Search

The liquid phase methanol (LPMeOH) synthesis process is to be commercially carried out in a liquid entrained reactor (LER), where the catalyst-inert oil slurry is pumped through the reaction zone along with the syngas fed separately. A computer model was developed based on the experimental results, for the LPMeOH process in a liquid entrained reactor. This computer program accurately predicts

P. vijayaraghavan; Conrad J. Kulik; Sunggyu Lee

1992-01-01

293

Transient liquid phase bonding of steel using an Fe–B interlayer  

Microsoft Academic Search

Transient liquid phase bonding processes have been performed to join two carbon steel tubes using Fe96.2B3.8 wt% amorphous ribbons as interlayers. Welding experiments were performed at the temperature T ? 1,250 °C for different durations and under pressures of 2, 3 and 4 MPa. From metallographic inspection it is concluded\\u000a that the bonding process ends in 7.0 min if a pressure of 4 MPa is applied whereas

Nicolas Di Luozzo; Marcelo Fontana; Bibiana Arcondo

2007-01-01

294

Transient Liquid Phase Die Attach for High-Temperature Silicon Carbide Power Devices  

Microsoft Academic Search

Recently, silicon carbide power devices have been receiving attention for applications above 300 °C. For high-temperature applications, the die attached for these devices has to withstand the maximum operating temperature. In this paper, a transient liquid phase (TLP) die attach technique was demonstrated for two binary alloy systems, Ag-In and Au-In, on Si3N4 substrates. A nearly void-free joint was developed

Habib A. Mustain; William D. Brown; Simon S. Ang

2010-01-01

295

Transient liquid phase bonding of steel using an Fe–B interlayer: microstructural analysis  

Microsoft Academic Search

Transient liquid phase bonding processes have been performed to join two carbon steel tubes using Fe96.2B3.8 wt% amorphous ribbons as interlayer. Welding experiments were performed at the temperature T ? 1,250 °C for different durations and under pressures of 0.8, 2, 3, and 4 MPa. From metallographic inspection, it is concluded\\u000a that the bonding process ends in 7.0 min if a pressure of 4 MPa is applied,

N. Di Luozzo; M. Fontana; B. Arcondo

2008-01-01

296

Microporous hydrophobic hollow fiber modules for gas-liquid phase separation in microgravity  

Microsoft Academic Search

Gas-liquid interphase mass transfer operations, such as gas-liquid phase separation, gas absorption into liquid or dissolved gas separation from liquid, gas humidification and drying via liquid contact, and evaporative cooling are readily accomplished on the Earth with settling\\/spray chambers, packed towers, or bubble columns. This paper reports on gas-water mass transfer tests performed utilizing microporous hydrophobic Hollow Fiber Modules (HFMs)

Gary Noyes

1993-01-01

297

Electrical and thermal conductivity of liquid phase sintered SiC  

Microsoft Academic Search

Commercial silicon carbide ceramics are semi-conductors. To obtain SiC ceramics with insulating properties, a synthesised SiC powder which was doped with vanadium and boron to get insulating behaviour due to compensating mechanism, and in addition a commercial powder was used. Both powders were pressureless sintered by liquid phase sintering. Different packing powders were used to influence the electrical behaviour of

Eduard Volz; Andreas Roosen; Wolfgang Hartung; Albrecht Winnacker

2001-01-01

298

Selective-Area Micropatterning of Liquid-Phase Epitaxy-Grown Iron Garnet Films  

Microsoft Academic Search

We investigated selective-area micropatterning of iron garnet film grown by liquid-phase epitaxy (LPE). This method of producing a flat-surface structure overcomes the disadvantages of geometrical grooves, which are formed by wet or dry etching, with a limited resolution due to underetching and nonplanar structure. Moreover, patterned iron garnet films grown by selective-area LPE have better single-crystal properties than films grown

Jae-Hyuk Park; Jae-kyeong Cho; Kazuhiro Nishimura; Hironaga Uchida; Mitsuteru Inoue

2004-01-01

299

Vapor–liquid phase behavior of binary systems of hydrogen chloride and certain n-alkanes  

Microsoft Academic Search

This contribution reports on experimental data of the vapor–liquid phase behavior of the binary system hydrogen chloride+ethane. It was confirmed that the system hydrogen chloride+ethane has type-I fluid phase behavior in the classification of Van Konynenburg and Scott with maximum pressure azeotropy. As an additional feature, it turned out that no reaction between hydrogen chloride and the mercury present in

L. J Florusse; C. J Peters

2002-01-01

300

Temperature dependence of the infinite dilution activity coefficient and Henry's law constant of polycyclic aromatic hydrocarbons in water.  

PubMed

The water solubility of 9,10-dihydroanthracene was experimentally determined between 278.12 and 313.17 K. Determinations were carried out by an experimental procedure developed in our laboratory, which is a modification of the dynamic coupled column liquid chromatographic technique. The uncertainty of the experimental determinations ranged from +/- 0.50% to +/- 3.10%. These data, as well as the water solubility data of other five polycyclic aromatic hydrocarbons (PAHs) previously studied, were used to calculate the temperature dependence of the infinite dilution activity coefficient of 9,10-dihydroanthracene, anthracene, pyrene, 9,10-dihydrophenanthrene, m-terphenyl, and guaiazulene in water. Molar excess enthalpies and entropies at infinite dilution, at 298.15 K, were also derived. The temperature dependence of the infinite dilution activity coefficients was used, together with literature values of the vapor pressures of supercooled liquid PAHs (p(B)(sc)), to estimate their Henry's law constants (HLC). Only HLC for anthracene, pyrene, and 9,10-dihydrophenanthrene were calculated, since no p(B)(sc) data were available in the literature for 9,10-dihydroanthracene, m-terphenyl, and guaiazulene. From the observed temperature dependence of the Henry's law constants the enthalpy and entropy of the phase change from the dissolved phase to the gas phase were also derived for anthracene, pyrene, and 9,10-dihydrophenanthrene. PMID:15212897

Reza, Joel; Trejo, Arturo

2004-08-01

301

The mean activity coefficients of 2:2 electrolyte solutions: an integral equation study of the restricted primitive model.  

PubMed

We apply the closure theory ZSEP (self-consistent zero-separation based closures) developed earlier to the restricted primitive model (RPM) of 2:2 electrolytes in order to (i) obtain the activity coefficient information via the direct formula for chemical potentials [L. L. Lee, J. Chem. Phys. 97, 8606 (1992)] and (ii) test the performance of this flexible ZSEP closure at high-coupling strengths (i.e., high valency and low temperatures) for cases of 2:2 electrolytes where other closure schemes have encountered difficulties [e.g., the hypernetted chain (HNC) equation]. In particular, we shall remedy the shortcomings of the HNC theory at low concentrations (from 0.001M to 0.2M). The ZSEP closure is found to perform well at coupling strengths beta(') = absolute value(z(1)z(2))e(2)/(epsilon(m)kTd) approaching approximately 10 where some other closure theories cease to give good results. In addition, by applying the direct chemical potential formula, we demonstrate numerically that, in the RPM cases examined, the logarithm of the mean activity coefficients of electrolytes are closely approximated by the electrostatic internal energy, an easily accessible quantity, a fact that shall afford ready access to the chemical potentials for phase equilibrium and electrochemical calculations on electrolytic systems. PMID:19355757

Chung, Ting-Horng; Lee, Lloyd L

2009-04-01

302

Eutectic mixed monolayers in equilibrium with phospholipid-bilayers and triolein-liquid phase.  

PubMed

Triolein (TO) and phospholipids (egg yolk phosphatidylcholine, egg yolk phosphatidylethanolamine, and bovine brain phosphatidylserine) had low mutual solubilities and separated into the TO-liquid phase and phospholipid-bilayers. Spreading pressures of the TO-phospholipid mixture (i.e., surface pressures of the mixed monolayer in equilibrium with the phase-separating lipid mixture) at the air/saline interface were independent of the lipid composition. On the other hand, collapse pressures of the mixed monolayer of TO and phospholipid (i.e., surface pressures of the mixed monolayer in equilibrium with the TO-liquid phase) at the interface changed with the monolayer composition and were lower than the spreading pressure. The experimental data indicated the spreading and collapse pressures as offering a phase diagram for the presence of equilibrium between the mixed monolayer, the phospholipid-bilayers and the TO-liquid phase. The diagram showed that TO and the phospholipids were miscible in the mixed monolayer, forming an eutectic mixed monolayer. When the mixed monolayer initially had the eutectic composition, no collapse of the monolayer was detected until the surface pressure reached the value of the spreading pressure. No specific complex between TO and the phospholipid is required to explain the stability and collapse of the mixed monolayers. The bulk immiscibility of the lipids elucidated by the spreading pressure-measurements, immediately leads to the phase behaviors observed. PMID:8369406

Handa, T; Saito, H; Miyajima, K

1993-06-01

303

Liquid-Phase Deposition of CIS Thin Layers: Final Report, February 2003--July 2005  

SciTech Connect

The goal of this project was to fabricate single-phase CIS (a-Cu-In-Se, stoichiometric composition: CuInSe2) thin films for photovoltaic applications from a liquid phase - a Cu-In-Se melt of appropriate composition. This approach of liquid-phase deposition (LPD) is based on the new phase diagram we have established for Cu-In-Se, the first complete equilibrium phase diagram of this system. The liquidus projection exhibits four composition fields in which the primary solid phase, i.e., the first solid material that forms on cooling down from an entirely liquid state, is a-CuInSe2. Remarkably, none of the four composition fields is anywhere near the stoichiometric composition (CuInSe2) of a-CuInSe2. The results demonstrate that the proposed technique is indeed capable of producing films with a particularly large grain size and a correspondingly low density of grain boundaries. To obtain films sufficiently thin for solar cell applications and with a sufficiently smooth surface, it is advantageous to employ a sliding boat mechanism. Future work on liquid-phase deposition of CIS should focus on the interaction between the melt and the substrate surface, the resulting CIS interfaces, the surface morphology of the LPD-grown films, and, of course, the electronic properties of the material.

Ernst, F.; Pirouz, P.

2006-02-01

304

Effect of titanium addition on the thermal properties of diamond/cu-ti composites fabricated by pressureless liquid-phase sintering technique.  

PubMed

In this study, minor-addition elements such as Si, Co, Cr, W, Mo, and Ti were added to matrix to improve the wettability between the diamonds and Cu matrix. The pressureless liquid-phase sintering technique adopted in this study provides a low-cost method for producing diamond/Cu composites with high potential for industrial mass production. Thermal properties of the diamond/Cu-Ti composites fabricated by pressureless liquid-phase sintering at 1373 K with variation in Ti contents were thoroughly investigated. XRD and TEM analysis show that TiC layer formed in the interface between Cu and diamond. The composites exhibited thermal conductivity as high as 620 W/m · K for 50 vol% diamond/Cu-0.6 at % Ti composite with diamond particle size of 300 µm. This value comes up to 85% of the thermal conductivity calculated by the Hasselman and Johnson (H-J) theoretical analysis. Under these conditions, a suitable coefficient of thermal expansion of 6.9 ppm/K was obtained. PMID:24715816

Chung, Chih-Yu; Chu, Chao-Hung; Lee, Mu-Tse; Lin, Chun-Ming; Lin, Su-Jien

2014-01-01

305

Three-phase hollow fiber liquid-phase microextraction based on a magnetofluid for the analysis of aristolochic acids in plasma by high-performance liquid chromatography.  

PubMed

A new and fast sample preparation technique based on three-phase hollow fiber liquid-phase microextraction with a magnetofluid was developed and successfully used to quantify the aristolochic acid I (AA-I) and AA-II in plasma after oral administration of Caulis akebiae extract. Analysis was accomplished by reversed-phase high-performance liquid chromatography with fluorescence detection. Parameters that affect the hollow fiber liquid-phase microextraction processes, such as the solvent type, pH of donor and acceptor phases, content of magnetofluid, salt content, stirring speed, hollow fiber length, extraction temperature, and extraction time, were investigated and optimized. Under the optimized conditions, the preconcentration factors for AA-I and AA-II were >627. The calibration curve for two AAs was linear in the range of 0.1-10 ng/mL with the correlation coefficients >0.9997. The intraday and interday precision was <5.71% and the LODs were 11 pg/mL for AA-I and 13 pg/mL for AA-II (S/N = 3). The separation and determination of the two AAs in plasma after oral administration of C. akebiae extract were completed by the validated method. PMID:24729270

Song, Rui Juan; Pu, Feng Ping; Zhou, Jun; Sun, Jiang Bing; Zeng, Ping; Zhang, Qiong

2014-07-01

306

Correlation of Biological Activity of Phenoxyacetic Acids with Hammett Substituent Constants and Partition Coefficients  

Microsoft Academic Search

IN the `two-point attachment' theory1 on the mechanism of action for growth regulators of the auxin type we have assumed as a working hypothesis that the reaction between auxin and substrate is more chemical than physical in nature and that covalent-bond formation is a possibility. The need for an aromatic ring with at least one unsubstituted position for auxin activity2

Corwin Hansch; Peyton P. Maloney; Toshio Fujita; ROBERT M. MUIR

1962-01-01

307

Diffusional effects on the various stages of liquid-phase sintering in microgravity  

NASA Astrophysics Data System (ADS)

A metal powder compact endures dramatic changes in its microstructures and properties during the three stages of liquid phase sintering, such as solid dissolution, solid solution formation, Ostwald ripening, and particle agglomeration. All these changes are restricted by the rate of diffusion and gravity induced convection. Under the microgravity environment, the effect of diffusion is much more significant and its influence could be investigated solely. In this dissertation, the diffusional effects on the different stages of liquid phase sintering were analyzed. A shrinking core model is for the first time applied to the liquid phase sintered alloys to investigate the mechanism and kinetics of the solid solution formation during the rearrangement stage. Evidence of the formation of a solid solution layer is presented. The results of the shrinking core modeling are favorably compared with the observations on different samples with various sintering times. For the solution-reprecipitation stage, the diffusion of pores plays an important role on the densification behavior, bead formation, and final microstructure of the composites. The shape factor of grains has significant influence on the application of the Lifshitz Slyozov Encounter Modified (LSEM) model to the experimental results. The shape factor was incorporated in the LSEM model to better represent the actual grain morphology in liquid phase sintering. Dihedral angle is an important indicator of an equilibrium particle configuration. A new dihedral angle model based totally on the geometry of spherical solid grains without any further assumptions is developed to determine the dihedral angles measured in two-dimensional sections for extrapolation to three dimensions. The result shows that the average dihedral angle measured on sections is 14/15 the dihedral angle in three dimensions. The expected frequencies of the simulation are compared with the experimental results obtained from microgravity liquid phase sintered Fe-Cu alloys with four different solid volume fractions (50, 60, 70, 80vol% Fe balanced with Cu) and six different sintering times (10, 20, 30, 40, 60 and 330 minutes) when a 3-D dihedral angle with a standard deviation of 10°, in our case, 40° +/- 10°, was employed in the model. The fit of the model to the experimental data is in good agreement since all the computed values of chi2 are smaller than the critical value chi20.05,16. According to the experimental results, an equilibrium particle configuration was obtained very early on in microgravity processing.

Ye, Saiyin

308

Transient liquid phase bonding of titanium-, iron- and nickel-based alloys  

NASA Astrophysics Data System (ADS)

The operating temperature of land-based gas turbines and jet engines are ever-increasing to increase the efficiency, decrease the emissions and minimize the cost. Within the engines, complex-shaped parts experience extreme temperature, fatigue and corrosion conditions. Ti-based, Ni-based and Fe-based alloys are commonly used in gas turbines and jet engines depending on the temperatures of different sections. Although those alloys have superior mechanical, high temperature and corrosion properties, severe operating conditions cause fast degradation and failure of the components. Repair of these components could reduce lifecycle costs. Unfortunately, conventional fusion welding is not very attractive, because Ti reacts very easily with oxygen and nitrogen at high temperatures, Ni-based superalloys show heat affected zone (HAZ) cracking, and stainless steels show intergranular corrosion and knife-line attack. On the other hand, transient liquid phase (TLP) bonding method has been considered as preferred joining method for those types of alloys. During the initial phase of the current work commercially pure Ti, Fe and Ni were diffusion bonded using commercially available interlayer materials. Commercially pure Ti (Ti-grade 2) has been diffusion bonded using silver and copper interlayers and without any interlayer. With a silver (Ag) interlayer, different intermetallics (AgTi, AgTi2) appeared in the joint centerline microstructure. While with a Cu interlayer eutectic mixtures and Ti-Cu solid solutions appeared in the joint centerline. The maximum tensile strengths achieved were 160 MPa, 502 MPa, and 382 MPa when Ag, Cu and no interlayers were used, respectively. Commercially pure Fe (cp-Fe) was diffusion bonded using Cu (25 m) and Au-12Ge eutectic interlayer (100 microm). Cu diffused predominantly along austenite grain boundaries in all bonding conditions. Residual interlayers appeared at lower bonding temperature and time, however, voids were observed in the joint centerline at higher joining temperature and time. Dispersed Au-rich particles were observed in the base metal near interface. The highest ultimate tensile strengths obtained for the bonded Fe were 291+/-2 MPa using a Cu interlayer at 1030°C for 10 h and 315+/-4 MPa using a Au-12Ge interlayer at 950°C for 15 h. Commercially pure Ni (cp-Ni) was diffusion bonded using a Al, Au-12Ge or Cu interlayer. The formation of intermetallics could not be avoided when Al interlayer was used. Even though no intermetallics were obtained with Au-12Ge or Cu interlayer, appreciable strength of the joint was not found. Next, the simple bonding systems were modeled numerically. It is hoped that the simple models can be extended for higher order alloys. The modeling of TLP joint means to come up with a mathematical model which can predict the concentration profiles of diffusing species. The concentration dependence of diffusivity in a multi-component diffusion system makes it complicated to predict the concentration profiles of diffusing species. The so-called chemical diffusivity can be expressed as a function of thermodynamic and kinetic data. DICTRA software can calculate the concentration profiles using appropriate mobility and thermodynamic data. It can also optimize the diffusivity data using experimental diffusivity data. Then the optimized diffusivity data is stored as mobility data which is a linear function of temperature. In this work, diffusion bonding of commercially pure Ni using Cu interlayers is reported. The mobility parameters of Ni-Cu alloy binary systems were optimized using DICTRA/Thermocalc software from the available self-, tracer and chemical diffusion coefficients. The optimized mobility parameters were used to simulate concentration profiles of Ni-Cu diffusion joints using DICTRA/Thermocalc software. The calculated and experimental concentration profiles agreed well at 1100 °C. This method could not be extended for higher order alloys because of the lack of appropriate thermodynamic and kinetic database. In the third phase industrially important alloys such

Rahman, A. H. M. Esfakur

309

Activity coefficients of sodium, potassium, and nitrate ions in aqueous solutions of NaNO 3 , KNO 3 , and NaNO 3 +KNO 3 at 25°C  

Microsoft Academic Search

Ion selective electrodes have been used to measure the activity coefficients at 25°C of individual ions in aqueous solutions of NaNO3 up to 3.5 molal, KNO3 up to 3.5 molal and mixtures of NaNO3 and KNO3 up to 2.4 molal total nitrate ion concentration. The experimental results confirm that the activity coefficient of anion and cation in aqueous single electrolyte

Maria der Mar Marcos-Arroyo; Mohammad K. Khoshkbarchi; Juan H. Vera

1996-01-01

310

Reexamination of the Synthesis of Liquid Crystalline Side-Chain Polyacrylates Via Liquid-Liquid Phase-Transfer Catalysis,  

National Technical Information Service (NTIS)

We have reexamined the synthesis of liquid crystalline side-chain polyacrylates under liquid liquid phase transfer conditions as first reported by Keller. Instead of the polymeric liquid crystals, the hydrolysis of the mesogen and a subsequent nucleophili...

S. H. Chen Y. F. Maa

1988-01-01

311

Iron(III) chloride supported on MCM-41 molecular sieve as a catalyst for the liquid-phase oxidation of phenol  

NASA Astrophysics Data System (ADS)

FeCl3 was supported on MCM-41 mesoporous molecular sieve via adsorption or coordination bonding and by embedding as an anionic constituent of covalently immobilized imidazolium ionic liquid (IL). The synthesized materials were characterized by N2-BET, SEM, TEM, FT-IR, 1H, 13C, and 29Si NMR, and DSC-TG. All of the catalysts were shown to be active for the liquid-phase oxidation of phenol by hydrogen peroxide. Supported FeCl3 species present as tetrachloroferrate counterions of immobilized IL are the most resistant to iron leaching.

Sirotin, S. V.; Moskovskaya, I. F.; Kolyagin, Yu. G.; Yatsenko, A. V.; Romanovsky, B. V.

2011-03-01

312

Determination of Activity Coefficients of di-(2-ethylhexyl) Phosphoric Acid Dimer in Select Organic Solvents Using Vapor Phase Osmometry  

SciTech Connect

Effective models for solvent extraction require accurate characterization of the nonideality effects for each component, including the extractants. In this study, the nonideal behavior of the industrial extractant di(2-ethylhexyl) phosphoric acid has been investigated using vapor pressure osmometry (VPO). From the osmometry data, activity coefficients for the HDEHP dimer were obtained based on a formulation of the regular solution theory of Scatchard and Hildebrand, and the Margules two- and three-suffix equations. The results show similarity with a slope-analysis based relation from previous literature, although important differences are highlighted. The work points towards VPO as a useful technique for this type of study, but care must be taken with the choice of standard and method of analysis.

Michael F. Gray; Peter Zalupski; Mikael Nilsson

2013-08-01

313

Ethers from ethanol. 1: Equilibrium thermodynamic analysis of the liquid-phase ethyl tert-butyl ether reaction  

Microsoft Academic Search

The equilibrium-limited liquid-phase synthesis of ethyl tert-butyl ether (ETBE) from the combination of ethanol and isobutylene over an ion-exchange resin catalyst, typically Amberlyst 15, is a reaction of considerable industrial importance now. An equilibrium constant relationship is developed here for the liquid-phase ETBE reaction by following three alternative thermodynamic pathways and critically evaluating the resulting expressions. The final theoretical expression

Kyle L. Jensen; Ravindra Datta

1995-01-01

314

Kinetics for benzoylation of sodium 4-acetylphenoxide via third-liquid phase in the phase-transfer catalysis  

Microsoft Academic Search

In this research, the kinetics for synthesizing 4-acetylphenyl benzoate (R*COOR) from benzoylation of sodium 4-acetylphenoxide via third-liquid phase-transfer catalysis was investigated. The reaction rate was observed to be strongly dependent on agitation speeds in the third-phase catalytic reaction. By forming the third-liquid phase, the observed reaction can be greatly enhanced to give a product yield of 100% in a duration

Chin-Chen Huang; Hung-Ming Yang

2005-01-01

315

Heat transfer characteristics of a rectangular natural circulation loop containing solid-liquid phase-change material suspensions  

Microsoft Academic Search

Purpose – To examine the heat transfer characteristics of soild-liquid phase change material (PCM) suspensions in a rectangular natural circulation loop. Design\\/methodology\\/approach – A continuum mixture flow model is used for the buoyancy-driven circulation flow of the PCM suspensions together with an approximate enthalpy model to describe the solid-liquid phase change (melting\\/freezing) process of the PC particles in the loop.

C. J. Ho; S. Y. Chiu; J. F. Lin

2005-01-01

316

Preparation of Eu-doped alkaline-earth silicate phosphor particles by using liquid-phase synthesis method  

Microsoft Academic Search

The liquid-phase synthesis method for preparing Eu-doped alkaline-earth silicate phosphor particles, which is expected to be applied for lighting apparatuses, such as mercury-free fluorescent lamps and flat-plane displays, such as PDP, was investigated. The sols, as the phosphor particle precursors, were synthesized by sol–gel processes under various conditions in the liquid-phase. The particle sizes of the sols were almost uniform,

Yoshihiro Nishisu; Mikio Kobayashi; Hitoshi Ohya; Toshiyuki Akiya

2006-01-01

317

CATALYST EFFECTIVENESS FACTORS UNDER GAS-TO-LIQUID MASS TRANSFER LIMITING REGIME IN LIQUID PHASE METHANOL SYNTHESIS PROCESS  

Microsoft Academic Search

The effectiveness factors of methanol synthesis catalyst were experimentally measured under condition of gas-to-liquid mass transfer limiting regime in the liquid phase methanol synthesis process, where the synthesis catalyst is slurried in an inert liquid phase. The experimental measurements of effectiveness factors were based on an intrinsic methanol synthesis rate per unit mass of catalyst (gmol\\/kg cat.h) which is not

Makarand Gogate; Sunggyu Lee

1994-01-01

318

Application of hollow fiber-supported liquid-phase microextraction coupled with HPLC for the determination of guaifenesin enantiomer-protein binding.  

PubMed

A hollow fiber liquid-phase microextraction technique coupled with high-performance liquid chromatography with fluorescence detection was employed for determination and evaluation of the binding characteristics of drugs to bovine serum albumin (BSA). Enantiomers of guaifenesin (an expectorant drug) were investigated as a model system. After optimization of some influencing parameters on microextraction, the proposed method was used for calculation of the target drug distribution coefficient between n-octanol and the buffer solution as well as study of drug-BSA binding in physiological conditions. The developed method shows a new, improved and simple procedure for determination of free drug concentration in biological fluids and the extent of drug-protein binding. PMID:22102436

Hatami, Mehdi; Farhadi, Khalil

2012-07-01

319

Ultrafast dynamics of the laser-induced solid-to-liquid phase transition in aluminum  

NASA Astrophysics Data System (ADS)

This dissertation reports the ultrafast dynamics of aluminum during the solid-to-liquid phase transition of melting after excitation by an intense femtosecond laser pulse. Photoexcitation with intense femtosecond laser pulses is known to create a novel melting mechanism called non-thermal melting. This mechanism has been observed repeatedly in semiconductors, but not yet in metals. We investigate the melting mechanism of aluminum by monitoring the reflectivity response following excitation by an intense laser pulse. We employ an optical pump-probe technique designed to measure broadband reflectivity across the visible spectrum with femtosecond time resolution. A non-thermal melting mechanism was proposed for aluminum by optical experiments that demonstrated transition of the optical properties from solid to liquid values within 500 fs after phototexcitation. This result was later challenged by electron diffraction experiments, which showed that the lattice loses long range order within 3.5 ps during photoinduced melting. This time scale implies conventional thermal melting. We find that the broadband optical properties during the solid-to-liquid phase transition in aluminum agree with the results obtained by the electron diffraction experiments. The transition of the broadband reflectivity from solid to liquid values is complete within 1.5--2 ps in our experiments, which is compatible with thermal melting. We don't observe time scales on the order of 500 fs. All the experimental evidence in this dissertation lead to the conclusion that the laser-induced, solid-to-liquid phase transition in aluminum is a thermal process.

Kandyla, Maria

320

Extended quantum U(1)-liquid phase in a three-dimensional quantum dimer model  

NASA Astrophysics Data System (ADS)

Recently, quantum dimer models have attracted a great deal of interest as a paradigm for the study of exotic quantum phases. Much of this excitement has centered on the claim that a certain class of quantum dimer model can support a quantum U(1)-liquid phase with deconfined fractional excitations in three dimensions. These fractional monomer excitations are quantum analogs of the magnetic monopoles found in spin ice. In this paper, we use extensive quantum Monte Carlo simulations to establish the ground-state phase diagram of the quantum dimer model on the three-dimensional diamond lattice as a function of the ratio ? of the potential to kinetic-energy terms in the Hamiltonian. We find that, for ?c=0.75±0.02, the model undergoes a first-order quantum phase transition from an ordered “R state” into an extended quantum U(1)-liquid phase, which terminates in a quantum critical Rokhsar-Kivelson (RK) point for ?=1. This confirms the published field-theoretical scenario. We present detailed evidence for the existence of the U(1)-liquid phase and indirect evidence for the existence of its photon and monopole excitations. Simulations are benchmarked against a variety of exact and perturbative results, and a comparison is made of different variational wave functions. We also explore the ergodicity of the quantum dimer model on a diamond lattice within a given flux sector, identifying a new conserved quantity related to transition graphs of dimer configurations. These results complete and extend the previous analysis of O. Sikora [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.103.247001 103, 247001 (2009)].

Sikora, Olga; Shannon, Nic; Pollmann, Frank; Penc, Karlo; Fulde, Peter

2011-09-01

321

Microscopic Evidence for a dense liquid phase of calcium carbonate (Invited)  

NASA Astrophysics Data System (ADS)

In the classical sense, minerals are presumed to nucleate directly from solution by overcoming a size-dependent free energy barrier that scales as the ratio of the macroscopic mineral-water interfacial tension cubed to the square of the thermodynamic supersaturation. However, experimental observations of the early stages of calcium carbonate mineralization demonstrate that under certain conditions formation of the crystalline polymorphs is preceded by the apparently spontaneous appearance of nanoscopic clusters that aggregate to produce metastable amorphous phases. This aggregation-based pathway is seemingly at odds with classical expectations. This research (Wallace et al., in press, Science) uses computational approaches to characterize the thermodynamic and dynamic properties of hydrated calcium carbonate cluster species, which are thus far only loosely constrained by experimental investigations. Replica exchange molecular dynamics simulations are employed to probe the initial formation of the clusters and lattice gas simulations are used to explore the general behavior of clusters at the onset of mineralization. The results suggest the growth of carbonate clusters may indeed proceed in the absence of any significant thermodynamic barrier. Moreover, the dynamical properties of the clusters are consistent with those of a dense liquid phase. Coalescence and dehydration of the nanoscale droplets result in the formation of a phase whose structure is consistent with that of amorphous calcium carbonate. These findings indicate that a spontaneous liquid-liquid phase separation may occur within the range of supersaturations spanned by natural waters. The coexistence of the dense and dilute liquid phases is described by a liquid-liquid binodal that may express a lower critical point near ambient temperature. Though liquid-liquid separation in simulations of the CaCO3-H2O system is an unexpected result, it suggests a means of generating nano- and mesoscopic phases consistent with established phase separation mechanisms and experimental observations.

Wallace, A. F.; Hedges, L.; Fernandez-Martinez, A.; Raiteri, P.; Gale, J. D.; Waychunas, G.; Whitelam, S.; Banfield, J. F.; De Yoreo, J. J.

2013-12-01

322

Statistical thermodynamics of liquid-liquid phase separation in ternary systems during complex coacervation  

NASA Astrophysics Data System (ADS)

Liquid-liquid phase separation leading to complex coacervation in a ternary system (oppositely charged polyion and macroion in a solvent) is discussed within the framework of a statistical thermodynamics model. The polyion and the macroion in the ternary system interact to form soluble aggregates (complexes) in the solvent, which undergoes liquid-liquid phase separation. Four necessary conditions are shown to drive the phase separation: (i) (?23)3r/?23c?((64)/(9?2))(?23?3)2 , (ii) r?[(64(?23?3)2)/(9?2?233)]1/2 , (iii) ?23?((2?231-1))/(?23c?3) , and (iv) (?23)2/I?(8)/(3?)(2?231-1) (where ?23 is the surface charge on the complex formed due to binding of the polyelectrolyte and macroion, ?23c is the critical volume fraction of the complex, ?23 is the Flory interaction parameter between polyelectrolyte and macroion, ?231 is the same between solvent and the complex, ?3 is the volume fraction of the macroions, I is the ionic strength of the solution, ? is electrostatic interaction parameter and r is typically of the order of molecular weight of the polyions). It has been shown that coacervation always requires a hydrated medium. In the case of a colloidal macroion and polyelectrolyte coacervation, molecular weight of polyelectrolyte must satisfy the condition r?103Da to exhibit liquid-liquid phase separation. This model has been successfully applied to study the coacervation phenomenon observed in aqueous Laponite (macroion)-gelatin (polyion) system where it was found that the coacervate volume fraction, ??23˜?2312 (where ??23 is the volume fraction of coacervates formed during phase separation). The free energy and entropy of this process have been evaluated, and a free-energy landscape has been drawn for this system that maps the pathway leading to phase separation.

Pawar, Nisha; Bohidar, H. B.

2010-09-01

323

Extended quantum U(1)-liquid phase in a three-dimensional quantum dimer model  

SciTech Connect

Recently, quantum dimer models have attracted a great deal of interest as a paradigm for the study of exotic quantum phases. Much of this excitement has centered on the claim that a certain class of quantum dimer model can support a quantum U(1)-liquid phase with deconfined fractional excitations in three dimensions. These fractional monomer excitations are quantum analogs of the magnetic monopoles found in spin ice. In this paper, we use extensive quantum Monte Carlo simulations to establish the ground-state phase diagram of the quantum dimer model on the three-dimensional diamond lattice as a function of the ratio {mu} of the potential to kinetic-energy terms in the Hamiltonian. We find that, for {mu}{sub c}=0.75{+-}0.02, the model undergoes a first-order quantum phase transition from an ordered ''R state'' into an extended quantum U(1)-liquid phase, which terminates in a quantum critical Rokhsar-Kivelson (RK) point for {mu}=1. This confirms the published field-theoretical scenario. We present detailed evidence for the existence of the U(1)-liquid phase and indirect evidence for the existence of its photon and monopole excitations. Simulations are benchmarked against a variety of exact and perturbative results, and a comparison is made of different variational wave functions. We also explore the ergodicity of the quantum dimer model on a diamond lattice within a given flux sector, identifying a new conserved quantity related to transition graphs of dimer configurations. These results complete and extend the previous analysis of O. Sikora et al.[Phys. Rev. Lett. 103, 247001 (2009)].

Sikora, Olga; Shannon, Nic; Pollmann, Frank; Penc, Karlo; Fulde, Peter [H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Max-Planck-Institut fuer Physik komplexer Systeme, D-01187 Dresden (Germany); Research Institute for Solid State Physics and Optics, H-1525 Budapest, P. O. Box 49 (Hungary); Max-Planck-Institut fuer Physik komplexer Systeme, D-01187 Dresden, Germany Asia Pacific Center for Theoretical Physics, Pohang (Korea, Republic of)

2011-09-15

324

Statistical thermodynamics of liquid-liquid phase separation in ternary systems during complex coacervation.  

PubMed

Liquid-liquid phase separation leading to complex coacervation in a ternary system (oppositely charged polyion and macroion in a solvent) is discussed within the framework of a statistical thermodynamics model. The polyion and the macroion in the ternary system interact to form soluble aggregates (complexes) in the solvent, which undergoes liquid-liquid phase separation. Four necessary conditions are shown to drive the phase separation: (i) (?{23}){3}r/?{23c}?(64/9?{2})(?{23}?{3}){2} , (ii) r?[64(?{23}?{3}){2}/9?{2}?{23}{3}]{1/2}, (iii) ?{23}?(2?{231}-1)/?{23c}?{3}, and (iv) (?{23}){2}/sqrt[I]?8/3?(2?{231}-1) (where ?{23} is the surface charge on the complex formed due to binding of the polyelectrolyte and macroion, ?{23c} is the critical volume fraction of the complex, ?{23} is the Flory interaction parameter between polyelectrolyte and macroion, ?{231} is the same between solvent and the complex, ?{3} is the volume fraction of the macroions, I is the ionic strength of the solution, ? is electrostatic interaction parameter and r is typically of the order of molecular weight of the polyions). It has been shown that coacervation always requires a hydrated medium. In the case of a colloidal macroion and polyelectrolyte coacervation, molecular weight of polyelectrolyte must satisfy the condition r?10{3}?Da to exhibit liquid-liquid phase separation. This model has been successfully applied to study the coacervation phenomenon observed in aqueous Laponite (macroion)-gelatin (polyion) system where it was found that the coacervate volume fraction, ??{23}??{231}{2} (where ??{23} is the volume fraction of coacervates formed during phase separation). The free energy and entropy of this process have been evaluated, and a free-energy landscape has been drawn for this system that maps the pathway leading to phase separation. PMID:21230139

Pawar, Nisha; Bohidar, H B

2010-09-01

325

Commercial-Scale Demonstration of the Liquid Phase methanol (LPMEOH) Process A DOE Assessment  

SciTech Connect

The U.S. Department of Energy (DOE) Clean Coal Technology (CCT) Program seeks to offer the energy marketplace more efficient and environmentally benign coal utilization technology options by demonstrating them in industrial settings. This document is a DOE post-project assessment (PPA) of one of the projects selected in Round III of the CCT Program, the commercial-scale demonstration of the Liquid Phase Methanol (LPMEOH{trademark}) Process, initially described in a Report to Congress by DOE in 1992. Methanol is an important, large-volume chemical with many uses. The desire to demonstrate a new process for the production of methanol from coal, prompted Air Products and Chemicals, Inc. (Air Products) to submit a proposal to DOE. In October 1992, DOE awarded a cooperative agreement to Air Products to conduct this project. In March 1995, this cooperative agreement was transferred to Air Products Liquid Phase Conversion Company, L.P. (the Partnership), a partnership between Air Products and Eastman Chemical Company (Eastman). DOE provided 43 percent of the total project funding of $213.7 million. Operation of the LPMEOH Demonstration Unit, which is sited at Eastman's chemicals-from-coal complex in Kingsport, Tennessee, commenced in April 1997. Although operation of the CCT project was completed in December 2002, Eastman continues to operate the LPMEOH Demonstration Unit for the production of methanol. The independent evaluation contained herein is based primarily on information from Volume 2 of the project's Final Report (Air Products Liquid Phase Conversion Co., L.P. 2003), as well as other references cited.

National Energy Technology Laboratory

2003-10-27

326

Charge Collection Process of a Liquid-Phase Epitaxially Grown InSb Detector  

NASA Astrophysics Data System (ADS)

The energy spectra of the gamma rays emitted by 241Am, 133Ba, and 137Cs were measured using an InSb detector made from a liquid-phase epitaxially (LPE) grown crystal. To understand the relationship between the maximum channel numbers of energy spectra and the maximum energies of gamma rays, a charge collection process is discussed. We performed numerical simulations of the charge collection process with a modified Hecht's equation. We showed that the entire LPE-InSb crystal including outside the depletion layer worked as a sensitive volume.

Sato, Yuki; Watanabe, Kenichi; Yamazaki, Atsushi; Kanno, Ikuo

2011-09-01

327

Liquid-liquid phase transition in a two-dimensional system with anomalous liquid properties  

NASA Astrophysics Data System (ADS)

The phase diagram of the two-dimensional particles interacting through a smooth version of Stell-Hemmer interaction was studied using Monte Carlo computer simulations. By evaluating the pressure-volume isotherms, we observed liquid-liquid, liquid-gas phase transitions and three stable crystal phases. The model shows the liquid-liquid critical point in stable liquid phase and is confirmed by observing properties of other thermodynamic functions such as heat capacity and isothermal compressibility, for example. The liquid-gas and the liquid-liquid critical points were estimated within the thermodynamic limit.

Urbic, Tomaz

2013-12-01

328

A GaAs MOSFET with a liquid phase oxidized gate  

Microsoft Academic Search

Low leakage current density (as low as 10-8 A\\/cm2 at an applied voltage of 5 V) and high breakdown electrical field (larger than 4.5 MV\\/cm) of the liquid phase chemical-enhanced oxidized GaAs insulating layer enable application to the GaAs MOSFET. The oxide layer is found to be a composite of Ga2O3, As, and As2O3. The n-channel depletion mode GaAs MOSFET's

Jau-Yi Wu; Hwei-Heng Wang; Yeong-Her Wang; Mau-Phon Houng

1999-01-01

329

Liquid-Phase Photochromic Composition Based on Titanium and Silver Compounds  

NASA Astrophysics Data System (ADS)

We have observed a photochromic colorization effect in a liquid-phase system based on a solution of silver nitrate in N,N-diethylacetamide and a solution of titanium alkoxide (tetrabutoxytitanium, polybutyl titanate etc.) in the presence of chloride or bromide ions. Colorization occurs on exposure to visible light or UV radiation, and is characterized by the appearance of an optical absorption band with maximum at 430-440 nm. When the colored composition is held in the dark, it is decolorized over a 2-12 hour period; at least 50 reversible colorization/ decolorization cycles can be achieved.

Branitsky, G. A.; Kulak, A. I.

2014-05-01

330

Joining of Ion Transport Membranes Using a Novel Transient Liquid Phase Process  

SciTech Connect

The feasibility of a novel transient liquid phase (TLP) joining method has been demonstrated in joining La{sub 0.9}Ca{sub 0.1}FeO{sub 3} materials. Metal oxide powders were processed to form the TLP compositions which were used in the joining process. The method has been successful in producing joint interfaces that effectively disappear, as they are the same material and have the same properties as the joined parts. The feasibility of the method has been demonstrated for a single system, but many systems where the method can potentially be applied have been identified.

Darryl P. Butt

2006-08-30

331

The segmented two-phase flow monolithic catalyst reactor. An alternative for liquid-phase hydrogenations  

SciTech Connect

Liquid-phase hydrogenation of nitrobenzoic acid was performed in a monolithic palladium catalyst. The total effectiveness factor of the catalyst was enhanced due to the fact that the mass transfer in the channels of the monolith was increased by the segmented gas-liquid flow. The effectiveness factor was shown to be much higher than for a trickle bed under corresponding reaction conditions. A mathematical model for the mass transfer in the segmented gas-liquid flow derived and found to describe the phenomena well.

Hatziantoniou, V.; Andersson, B.

1984-02-01

332

Processing industrial wastes with the liquid-phase reduction romelt process  

NASA Astrophysics Data System (ADS)

The Romelt technology for liquid-phase reduction has been developed for processing metallurgical wastes containing nonferrousmetal components. Thermodynamic calculations were made to investigate the behavior of silver, copper, zinc, manganese, vanadium, chrome, and silicon when reduced from the slag melt into the metallic solution containing iron. The process can be applied to all types of iron-bearing wastes, including electric arc furnace dust. The distribution of elements between the phases can be controlled by adjusting the slag bath temperature. Experiments at a pilot Romelt plant proved the possibility of recovering the metallurgical wastes and obtaining iron.

Romenets, V.; Valavin, V.; Pokhvisnev, Yu.; Vandariev, S.

1999-08-01

333

Tritiated water processing using liquid phase catalytic exchange and solid oxide electrolyte cell  

SciTech Connect

Liquid phase catalytic exchange (LPCE) is an effective method for enrichment and removal of tritium from tritiated water. Combined electrolysis catalytic exchange (CECE) process is an attractive application of a LPCE column. We proposed a new process that improves the CECE process. Using a solid oxide electrolyte (SOE) cell for electrolysis makes the CECE process more energy efficient and eliminates other disadvantages such as large tritium inventory and extremely slow system response. When the cell is used for recombination, the system becomes even more simple, efficiently, reliable and safe. 21 refs., 9 figs.

Yamai, H.; Konishi, S.; Hara, M.; Okuno, K. [Japan Atomic Energy Research Inst., Ibaraki (Japan); Yamamoto, I. [Nagoya Univ. (Japan)

1995-10-01

334

Transient-Liquid-Phase and Liquid-Film-Assisted Joining ofCeramics  

SciTech Connect

Two joining methods, transient-liquid-phase (TLP) joining and liquid-film-assisted joining (LFAJ), have been used to bond alumina ceramics. Both methods rely on multilayer metallic interlayers designed to form thin liquid films at reduced temperatures. The liquid films either disappear by interdiffusion (TLP) or promote ceramic/metal interface formation and concurrent dewetting of the liquid film (LFAJ). Progress on extending the TLP method to lower temperatures by combining low-melting-point (<450 C) liquids and commercial reactive-metal brazes is described. Recent LFAJ work on joining alumina to niobium using copper films is presented.

Sugar, Joshua D.; McKeown, Joseph T.; Akashi, Takaya; Hong, SungM.; Nakashima, Kunihiko; Glaeser, Andreas M.

2005-02-09

335

Liquid phase methanol reactor staging process for the production of methanol  

DOEpatents

The present invention is a process for the production of methanol from a syngas feed containing carbon monoxide, carbon dioxide and hydrogen. Basically, the process is the combination of two liquid phase methanol reactors into a staging process, such that each reactor is operated to favor a particular reaction mechanism. In the first reactor, the operation is controlled to favor the hydrogenation of carbon monoxide, and in the second reactor, the operation is controlled so as to favor the hydrogenation of carbon dioxide. This staging process results in substantial increases in methanol yield.

Bonnell, Leo W. (Macungie, PA); Perka, Alan T. (Macungie, PA); Roberts, George W. (Emmaus, PA)

1988-01-01

336

Biopolymer-supported ionic-liquid-phase ruthenium catalysts for olefin metathesis.  

PubMed

Original ruthenium supported ionic liquid phase (SILP) catalysts based on alginates as supports were developed for olefin metathesis reactions. The marine biopolymer, which fulfills most of the requisite properties for a support such as widespread abundance, insolubility in the majority of organic solvents, a high affinity for ionic liquids, high chemical stability, biodegradability, low cost, and easy processing, was impregnated by [bmim][PF6 ] containing an ionically tagged ruthenium catalyst. These biosourced catalysts show promising performances in ring-closing metathesis (RCM) and cross-metathesis (CM) reactions, with a high level of recyclability and reusability combined with a good reactivity. PMID:24616203

Clousier, Nathalie; Filippi, Alexandra; Borré, Etienne; Guibal, Eric; Crévisy, Christophe; Caijo, Fréderic; Mauduit, Marc; Dez, Isabelle; Gaumont, Annie-Claude

2014-04-01

337

Liquid phase epitaxial growth of InAs 1-x Sb x on GaSb  

Microsoft Academic Search

Reported here, for the first time, is the lattice matched growth of InAs1-xSbx on GaSb. The thermodynamic incompatibility of the system, i.e., the strong tendency for the In-As-Sb liquid to dissolve the\\u000a GaSb substrate, was solved via a novel liquid phase epitaxial growth technique. Liquid compositions for lattice matching conditions\\u000a have been determined in the 400-600C range. Epitaxial growth has

E. R. Gertner; A. M. Andrews; L. O. Bubulac; D. T. Cheung; M. J. Ludowise; R. A. Riedel

1979-01-01

338

Liquid-liquid phase coexistence in gold clusters: 2D or not 2D?  

PubMed

The thermodynamics of gold cluster anions (AuN-, N=11,...,14) is investigated using quantum molecular dynamics. Our simulations suggest that AuN- may exhibit a novel, freestanding planar liquid phase which dynamically coexists with a normal three-dimensional liquid. Upon cooling with experimentally realizable cooling rates, the entropy-favored three-dimensional liquid clusters often supercool and solidify into the "wrong" dimensionality. This indicates that experimental validation of theoretically predicted AuN- ground states might be more complicated than hitherto expected. PMID:17358487

Koskinen, Pekka; Häkkinen, Hannu; Huber, Bernd; von Issendorff, Bernd; Moseler, Michael

2007-01-01

339

Liquid-Liquid Phase Coexistence in Gold Clusters: 2D or Not 2D?  

NASA Astrophysics Data System (ADS)

The thermodynamics of gold cluster anions (AuN-, N=11,…,14) is investigated using quantum molecular dynamics. Our simulations suggest that AuN- may exhibit a novel, freestanding planar liquid phase which dynamically coexists with a normal three-dimensional liquid. Upon cooling with experimentally realizable cooling rates, the entropy-favored three-dimensional liquid clusters often supercool and solidify into the “wrong” dimensionality. This indicates that experimental validation of theoretically predicted AuN- ground states might be more complicated than hitherto expected.

Koskinen, Pekka; Häkkinen, Hannu; Huber, Bernd; von Issendorff, Bernd; Moseler, Michael

2007-01-01

340

Electrical Characterization of Graphene Flakes Synthesized Using Liquid Phase Exfoliation of Graphite in Isopropyl Alcohol  

NASA Astrophysics Data System (ADS)

Liquid-phase exfoliation processes for synthesis of nano structures is often a simpler route to get functional nanomaterials in large scale. Here we will report on the synthesis of graphene flakes using exfoliation of bulk graphite in isopropyl alcohol. We will also present electrical characterization of thin film devices made from these exfoliated flakes. Temperature dependence of resistance performed for 10K T 300K shows a slow linear increase in resistance with decrease in temperature. Behavior of thin film devices made from these exfoliated flakes under electrochemical gating environment will be presented and discussed.

Talapatra, Saikat; Muchharla, Baleeswaraiah; Connolly, Mitchell; Winchester, Andrew; Ghosh, Sujoy; Kar, Swastik

2013-03-01

341

Transient liquid phase diffusion bonding of Udimet 720 for Stirling power converter applications  

NASA Astrophysics Data System (ADS)

Udimet 720 has been selected for use on Stirling power converters for space applications. Because Udimet 720 is generally considered susceptible to strain age cracking if traditional fusion welding is used, other joining methods are being considered. A process for transient liquid phase diffusion bonding of Udimet 720 has been theoretically developed in an effort to eliminate the strain age crack concern. This development has taken into account such variables as final grain size, joint homogenization, joint efficiency related to bonding aid material, bonding aid material application method, and thermal cycle.

Mittendorf, Donald L.; Baggenstoss, William G.

342

Transient liquid phase diffusion bonding of Udimet 720 for Stirling power converter applications  

NASA Technical Reports Server (NTRS)

Udimet 720 has been selected for use on Stirling power converters for space applications. Because Udimet 720 is generally considered susceptible to strain age cracking if traditional fusion welding is used, other joining methods are being considered. A process for transient liquid phase diffusion bonding of Udimet 720 has been theoretically developed in an effort to eliminate the strain age crack concern. This development has taken into account such variables as final grain size, joint homogenization, joint efficiency related to bonding aid material, bonding aid material application method, and thermal cycle.

Mittendorf, Donald L.; Baggenstoss, William G.

1992-01-01

343

Selective-Area Micropatterning of Liquid-Phase Epitaxy-Grown Iron Garnet Films  

NASA Astrophysics Data System (ADS)

We investigated selective-area micropatterning of iron garnet film grown by liquid-phase epitaxy (LPE). This method of producing a flat-surface structure overcomes the disadvantages of geometrical grooves, which are formed by wet or dry etching, with a limited resolution due to underetching and nonplanar structure. Moreover, patterned iron garnet films grown by selective-area LPE have better single-crystal properties than films grown by selective-area sputter epitaxy deposition. Thus, this method offers new possibilities for the fabrication of integrated magnetooptic light switch arrays, magnetic waveguides and other magnetooptic devices.

Park, Jae-Hyuk; Cho, Jae-kyeong; Nishimura, Kazuhiro; Uchida, Hironaga; Inoue, Mitsuteru

2004-07-01

344

Laser-induced deposition of hetero-metallic structures from liquid phase  

NASA Astrophysics Data System (ADS)

Laser-induced chemical-liquid phase deposition of hetero-metallic (Gu-Cr) structures is demonstrated for the first time. The deposition of hetero-metallic structures is of special interest thanks to wider range of properties as compared to pure metals. The deposition was realized from the electrolyte solution based on copper sulphate and potassium dichromate. The focused beam of the continuous wave Ar+ laser generated in the multiwave regime was used for the structures precipitation. The chemical processes resulting in Cu-Cr structures deposition are analyzed emphasizing some features typical for laser-assisted methods.

Manshina, A.; Ivanova, T.; Povolotskiy, A.

2010-06-01

345

Enantioselective fungal biotransformation of risperidone in liquid culture medium by capillary electrophoresis and hollow fiber liquid-phase microextraction.  

PubMed

Knowing that microbial transformations of compounds play vital roles in the preparation of new derivatives with biological activities, risperidone and its chiral metabolites were determined by capillary electrophoresis and hollow fiber liquid-phase microextraction after a fungal biotransformation study in liquid culture medium. The analytes were extracted from 1 mL liquid culture medium into 1-octanol impregnated in the pores of the hollow fiber, and into an acid acceptor solution inside the polypropylene hollow fiber. The electrophoretic separations were carried out in 100 mmol/L sodium phosphate buffer pH 3.0 containing 2.0% w/v sulfated-?-CD and carboxymethyl-?-CD 0.5% w/v with a constant voltage of -10 kV. The method was linear over the concentration range of 100-5000 ng/mL for risperidone and 50-5000 ng/mL for each metabolite enantiomer. Within-day and between-day assay precisions and accuracies for all the analytes were studied at three concentration levels, and the values of relative standard deviation and relative error were lower than 15%. The developed method was applied in a pilot biotransformation study employing risperidone as the substrate and the filamentous fungus Mucor rouxii. This study showed that the filamentous fungus was able to metabolize risperidone enantioselectively into its chiral active metabolite, (-)-9-hydroxyrisperidone. PMID:21898463

de Jesus, Liana I; Albuquerque, Nayara C P; Borges, Keyller B; Simões, Rodrigo A; Calixto, Leandro A; Furtado, Niege A J C; de Gaitani, Cristiane M; Pupo, Mônica T; de Oliveira, Anderson R M

2011-10-01

346

Activity Coefficients at Infinite Dilution of Organic Compounds in Trihexyl(tetradecyl)phophonium Bis(trifluoromethylsulfonyl)imide Using Inverse Gas Chromatography  

SciTech Connect

Activity coefficients at infinite dilution of organic compounds in the ionic liquid (IL) trihexyl(tetradecyl) phosphonium bis(trifluoromethylsulfonyl)imide were determined using inverse gas chromatography at three temperatures, T ) (302.45, 322.35, and 342.45) K. Linear free energy relationship (LFER) correlations have been obtained for describing the gas-to-IL and water-to-IL partition coefficients.

Revelli, Anne-Laure [Laboratoire de Thermodynamique des Milieux Polyphases, Nancy-Universite, Nancy, France; Sprunger, Laura [University of North Texas; Gibbs, Jennifer [University of North Texas; Acree, William [University of North Texas; Baker, Gary A [ORNL; Mutelet, Fabrice [Laboratoire de Thermodynamique des Milieux Polyphases, Nancy-Universite, Nancy, France

2009-01-01

347

Effects of Second-Order Coupling Coefficient Dispersion on Short-Pulse Propagation and Switching in an Active Two-Core Nonlinear Fiber Coupler  

Microsoft Academic Search

The propagation and switching of short pulses in an active two-core fiber nonlinear directional coupler have been investigated theoretically by using the split-step Fourier method. The analysis highlights the effects of the second-order coupling coefficient dispersion, the linear gain coefficient, and the finite-gain bandwidth on the switching and propagation of short pulses. The research indicates that the linear gain can

Qiliang Li; Yuyong Xie; Yinfang Zhu; Yongmin Qi; Zhijing Zhao

2009-01-01

348

Study on anisotropy of effective diffusion coefficient and activation energy for deuterated water in compacted sodium bentonite  

NASA Astrophysics Data System (ADS)

To quantify the effects of temperature on the diffusivity of deuterated water (HDO) in compacted sodium bentonite, through-diffusion experiments were conducted at elevated temperatures ranging from 298 to 333 K. Kunipia F (Na-montmorillonite content>98 wt.%; Kunimine Industries) was compacted to a dry density of 0.9 or 1.35 Mg/m 3. As montmorillonite particles were oriented perpendicular to the direction of compaction, the anisotropy of diffusivity was investigated both parallel and normal to the preferred orientation of the montmorillonite. The effective diffusion coefficient De of HDO was larger when the diffusional direction was parallel as opposed to normal to the preferred orientation for both dry densities. The magnitude of De and the anisotropy for HDO were in good accordance with previously reported results for tritiated water at room temperature. Activation energies of De were isotropic and increased with increasing dry density over the range of 19-25 kJ/mol. This relationship was considered to be due to both pore structure development and the high activation energy of water near the montmorillonite surface.

Suzuki, Satoru; Sato, Haruo; Ishidera, Takamitsu; Fujii, Naoki

2004-01-01

349

Liquid-Liquid Phase Separation in Supersaturated Lysozyme Solutions and Associated Precipitate Formation/Crystallization  

NASA Technical Reports Server (NTRS)

Using cloud point determinations, the phase boundaries (binodals) for metastable liquid-liquid (L-L) separation in supersaturated hen egg white lysozyme solutions with 3%, 5%, and 7% (wlv) NaCl at pH= 4.5 and protein concentrations c between 40 and 400 mg/ml were determined. The critical temperature for the binodal increased approximately linearly with salt concentration. The coexisting liquid phases both remained supersaturated but differed widely in protein concentration. No salt repartitioning was observed between the initial and the two separated liquid phases. After the L-L separation, due to the presence of the high protein concentration phase, crystallization occurred much more rapidly than in the initial solution. At high initial protein concentrations, a metastable gel phase formed at temperatures above the liquid binodal. Both crystal nucleation and gel formation were accelerated in samples that had been cycled through the binodal. Solutions in the gel and L-L regions yielded various types of precipitates. Based on theoretical considerations, previous observations with other proteins, and our experimental results with lysozyme, a generic phase diagram for globular proteins is put forth. A limited region in the (T,c) plane favorable for the growth of protein single crystals is delineated.

Muschol, Martin; Rosenberger, Franz

1997-01-01

350

Transient-pressure analysis in geothermal steam reservoirs with an immobile vaporizing liquid phase  

USGS Publications Warehouse

A finite-difference model for the radial horizontal flow of steam through a porous medium is used to evaluate transient-pressure behavior in the presence of an immobile vaporizing or condensing liquid phase. Graphs of pressure drawdown and buildup in terms of dimensionless pressure and time are obtained for a well discharging steam at a constant mass flow rate for a specified time. The assumptions are made that the steam is in local thermal equilibrium with the reservoir rocks, that temperature changes are due only to phase change, and that effects of vapor-pressure lowering are negligible. Computations show that when a vaporizing liquid phase is present the pressure drawdown exhibits behavior similar to that observed in noncondensable gas reservoirs, but delayed in time. A theoretical analysis allows for the computation of this delay and demonstrates that it is independent of flow geometry. The response that occurs upon pressure buildup is markedly different from that in a noncondensable gas system. This result may provide a diagnostic tool for establishing the existence of phase-change phenomena within a reservoir. ?? 1979.

Moench, A. F.; Atkinson, P. G.

1978-01-01

351

Applications of liquid-phase microextraction in the sample preparation of environmental solid samples.  

PubMed

Solvent extraction remains one of the fundamental sample preparation techniques in the analysis of environmental solid samples, but organic solvents are toxic and environmentally harmful, therefore one of the possible greening directions is its miniaturization. The present review covers the relevant research from the field of application of microextraction to the sample preparation of environmental solid samples (soil, sediments, sewage sludge, dust etc.) published in the last decade. Several innovative liquid-phase microextraction (LPME) techniques that have emerged recently have also been applied as an aid in sample preparation of these samples: single-drop microextraction (SDME), hollow fiber-liquid phase microextraction (HF-LPME), dispersive liquid-liquid microextraction (DLLME). Besides the common organic solvents, surfactants and ionic liquids are also used. However, these techniques have to be combined with another technique to release the analytes from the solid sample into an aqueous solution. In the present review, the published methods were categorized into three groups: LPME in combination with a conventional solvent extraction; LPME in combination with an environmentally friendly extraction; LPME without previous extraction. The applicability of these approaches to the sample preparation for the determination of pollutants in solid environmental samples is discussed, with emphasis on their strengths, weak points and environmental impact. PMID:24858267

Prosen, Helena

2014-01-01

352

Liquid phase microextraction for the analysis of trace elements and their speciation  

NASA Astrophysics Data System (ADS)

Trace/ultra-trace elements and their speciation analysis in complex matrices usually require sample preparation procedures to achieve sample clean-up and analyte preconcentration. Sample preparation is often the bottleneck in trace elements and their speciation analysis which has a direct impact on accuracy, precision and limits of detection and is often the rate-determining step of the analytical process. Recent trends in sample preparation include miniaturization, automation, high-throughput performance and reduction in solvent/sample consumption and operation time. Liquid-phase microextraction (LPME) technique as a novel and promising alternative in sample preparation can meet these requirements and has become a very efficient sample preparation technique. This review updates the state of art of LPME for trace elements and their speciation analysis and discusses its promising prospects. The major thrust of the article highlights the applications of LPME including single-drop microextraction (SDME), hollow fiber-liquid phase microextraction (HF-LPME), dispersive liquid liquid microextraction (DLLME) and solidified floating organic drop microextraction (SFODME) to the fields of elemental and their speciation analysis by atomic spectrometry-based methods, especially inductively coupled plasma mass spectrometry. General and specific concepts, different extraction formats and characteristics of LPME are described and compared, along with examples of recent innovations and applications presented to demonstrate its potential for trace elements and their speciation analysis in biological and environmental fields. Moreover, the application potential and an outlook on the combination of LPME and atomic spectrometry-based techniques for inorganic analysis are commentated.

Hu, Bin; He, Man; Chen, Beibei; Xia, Linbo

2013-08-01

353

Solid-liquid phase equilibria from free-energy perturbation calculations  

NASA Astrophysics Data System (ADS)

A method for calculating free-energy differences based on a free-energy perturbation (FEP) formalism in an alloy system described by two different Hamiltonians is reported. The intended application is the calculation of solid-liquid phase equilibria in alloys with the accuracy of first-principles electronic density-functional theory (DFT). For this purpose free energies are derived with a classical interatomic potential, and FEP calculations are used to compute corrections to these reference values. For practical applications of this approach, due to the relatively high computational cost of DFT calculations, it is critical that the FEP calculations converge rapidly in terms of the number of samples used to estimate relevant ensemble averages. This issue is investigated in the current study employing two classical interatomic-potential models for Ni-Cu. These models yield differences in predicted phase-boundary temperatures of approximately 100 K, comparable to those that might be expected between a DFT Hamiltonian and a well-fit classical potential. We show that for pure elements the FEP calculations converge rapidly with the number of samples, yielding free-energy differences converged to within a fraction of a meV/atom in a few dozen energy calculations. For a concentrated equiatomic alloy similar precision requires roughly a hundred samples. The results suggest that the proposed methodology could provide a computationally tractable framework for calculating solid-liquid phase equilibria in concentrated alloys with DFT accuracy.

Angioletti-Uberti, Stefano; Asta, Mark; Finnis, Mike W.; Lee, P. D.

2008-10-01

354

Liquid phase preparation and fluorescence of flake-liked NdF{sub 3} nanomaterials  

SciTech Connect

Graphical abstract: Room-temperature emission spectra of NdF{sub 3} nanoflakes exhibit a strong luminescence emission peak at 402 nm when irradiated by an excitation wavelength of 250 nm. Display Omitted Highlights: ? NdF{sub 3} nanoflakes have been successfully prepared by a facile and repeatable liquid phase preparation. ? The action of oxalic acid in the reaction process was studied, showing important in the morphology of neodymium fluorides. ? The study on the fluorescent properties of flake-like NdF{sub 3} nanomaterials shows a strong emission peak at 402 nm by the excitation wavelength of 250 nm. -- Abstract: Neodymium fluoride nanoflakes were successfully prepared by a facile liquid phase preparation with Nd(NO{sub 3}){sub 3} and NaF as raw materials. In the process, oxalic acid acting as template agent was found to play important roles in the morphology of neodymium fluorides. The as-synthesized NdF{sub 3} nanoflakes were characterized by various techniques of X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectrometer instrument (EDS). The fluorescent properties of neodymium fluoride nanoflakes were investigated, showing a strong luminescence emission peak at 402 nm by the excitation wavelength of 250 nm.

Tian, Li, E-mail: ltian@hnust.edu.cn [Institute of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201 (China) [Institute of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201 (China); State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Lian, Peili; Sun, Qiliang; Long, Peng; Xiang, Shaobin [Institute of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201 (China)] [Institute of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201 (China); Zhu, Guangshan [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China)] [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China)

2013-01-15

355

Unusual stacking variations in liquid-phase exfoliated transition metal dichalcogenides.  

PubMed

Liquid-phase exfoliation of layered materials offers a large-scale approach toward the synthesis of 2D nanostructures. Structural properties of materials can however change during transition from bulk to the 2D state. Any such changes must be examined and understood for successful implementation of 2D nanostructures. In this work, we demonstrate nonbulk stacking sequences in the few-layer MoS2 and WS2 nanoflakes produced by liquid-phase exfoliation. Our analysis shows that nonbulk stacking sequences can be derived from its bulk counterparts by translational shifts of the layers. No structural changes within the layers were observed. Twenty-seven MoS2 and five WS2 nanoflakes were imaged and analyzed. Nine MoS2 and four WS2 nanoflakes displayed nonbulk stacking. Such dominance of the nonbulk stacking suggests high possibility of unusual stacking sequences in other 2D nanostructures. Notably, the electronic structure of some non bulk stacked bilayers presents characteristics which are uncommon to either the bulk phase or the single monolayer, for instance, a spin-split conduction band bottom. Our main characterization technique was annular dark-field scanning transmission electron microscopy, which offers direct and reliable imaging of atomic columns. The stacking characterization approach employed here can be readily applied toward other few-layer transition metal chalcogenides and oxides. PMID:24588696

Shmeliov, Aleksey; Shannon, Mervyn; Wang, Peng; Kim, Judy S; Okunishi, Eiji; Nellist, Peter D; Dolui, Kapildeb; Sanvito, Stefano; Nicolosi, Valeria

2014-04-22

356

Quantitative Thermal Analysis of Transient Liquid-Phase-Sintered Cu-Ni Powders  

NASA Astrophysics Data System (ADS)

Differential scanning calorimetry (DSC) was used to study the transient liquid phase sintering (TLPS) of elemental Ni and Cu powder mixtures. The initial melting behavior, kinetics of isothermal solidification, and remelt behavior of these powder mixtures were quantified, using DSC and metallographic techniques. The effects of the initial liquid distribution and processing temperature on these events were investigated. Quantitative DSC analysis indicates that suppressed liquid fractions form during TLPS at peak temperatures of 1090 °C and 1140 °C, due to solid-state interdiffusion prior to melting. Larger liquid fractions form at 1140 °C compared to 1090 °C, due to the recovery of some liquid previously lost to interdiffusion by dissolution at the higher peak temperature. This resulted in higher sintered densities at 1140 °C. Complete isothermal solidification of the Cu-rich transient liquid requires more time at 1140 °C due to higher liquid fractions initially formed at this temperature compared to those formed at 1090 °C. When the initial liquid is distributed nonuniformly, isothermal solidification times are also longer. The DSC and metallographic data indicate that the transient liquid phase (TLP) isothermally solidifies by limited long-range Cu diffusion into the Ni particles and by the epitaxial growth of a surrounding Cu-rich “layer” via the gradual outward progression of the solid/liquid interface at compositions given by the liquidus and solidus.

Turriff, D. M.; Corbin, S. F.

2008-01-01

357

Dynamics of the Spin Liquid Phase of Cs2CuCl4  

NASA Astrophysics Data System (ADS)

The dynamics of a spin-liquid phase of an antiferromagnet on the anisotropic triangular lattice and in a magnetic field are studied with a combination of Gutzwiller-projected wavefunctions and mean-field theory. Candidate ground states that support fermionic gapless spinon excitations include four different U(1) spin liquidsootnotetextY. Zhou, X. G. Wen, cond-mat/0210662 (2003).. The lattice and the states interpolate between limiting cases of 1D decoupled chains (J/J^' = 0) and the isotropic 2D square lattice (J/J^'= ?). Parameters of the mean field theory are chosen to minimize the ground state energy of the corresponding Gutzwiller-projected wavefunction. The spin-lattice relaxation rate 1/T1, calculated within the mean-field approximation, is compared to NMR measurementsootnotetextM. A. Vachon, O. Ma, J. B. Marston, V. F. Mitrovi'c, unpublished (2007). in the spin liquid phase of Cs2CuCl4ootnotetextY. Tokiwa, T. Radu, R. Coldea, H. Wilhelm, Z. Tylczynski, F. Steglich, PRB 73, 134414 (2006)..

Ma, Ookie; Vachon, Marc-Andre; Mitrovi{?}, Vesna F.; Marston, Brad

2008-03-01

358

Spatial Distribution of Crustal Anisotropy in and around the Atotsugawa Fault, Japan -To Infer the Frictional Coefficient of Active Fault-  

NASA Astrophysics Data System (ADS)

The spatial variation of frictional coefficient along active fault can be inferred from detail observation of stress field around the fault. We infer the spatial variation of maximum compressional stress axis around the active faults from dense observation of crustal anisotropy. The major possible cause of seismic anisotropy in the crust is the preferred orientation of micro cracks directed parallel to the axis of maximum compressional stress. Seismic anisotropy data are integrated effects from hypocenter to observatory, similar to travel time analysis, so we can obtain detailed images of the stress field by a tomographic approach if huge amounts of anisotropy data are available. The resolution of stress field imaged by the observation of anisotropy is expected to be higher than that studied by focal mechanisms or geodetic measurements such as GPS observation. In this study, we analyzed detailed anisotropy structure in and around the Atotsugawa fault, central Japan. The Atotsugawa fault, 60 km in length and N 60° E of strike, is located along the Niigata-Kobe tectonic zone, which is recognized as a deformation zone with a high strain rate. GPS observation indicates that the central part of the Atotsugawa fault is creeping and the other parts of the fault is locked to a depth of 15 km. Therefore, we can expect that the axis of maximum compressional stress is varied along the fault. Our observation indicates that crack orientation in and around the Atotsugawa fault is nearly consistent with the direction of the regional maximum stress in this area (NW-SE). On the western part, at stations 5 km away from the fault, crack orientation almost correspond to the regional maximum compressional direction. However, the direction of maximum compressional stress that inferred from anisotropy seems to have variation. At the western part of the fault, the direction of maximum compressional stress is estimated to be WNW-ESE. At the eastern part of the fault, the angle of maximum compressional axis makes more acute with the fault. This result may imply that frictional coefficient at the eastern part of Atotsugawa fault is higher than that of the western part.

Mizuno, T.; Ito, H.; Kuwahara, Y.; Imanishi, K.

2003-12-01

359

In-situ Observations of Liquid-liquid Phase Separation in Aqueous MgSO4 Solutions: Geological and Geochemical Implications  

NASA Astrophysics Data System (ADS)

A previously unknown liquid-liquid phase separation in vapor-saturated aqueous MgSO4 solutions containing 1.19 to 19.36 mass % of MgSO4 was observed in fused silica capillary capsules during heating at temperatures above 259 °C. Under these conditions, we observed that MgSO4-rich droplets were separated from the original aqueous MgSO4 solutions during heating, and these two coexisting liquid phases homogenized during cooling. The newly discovered liquid-liquid phase separation in MgSO4 solutions is characterized by a lower critical solution temperature (LCST), which is considered to be a macro-scale chemical property of polymeric mixtures. In-situ Raman spectroscopic investigations identified a distinctly new ?1(SO42-) mode at ~1020 cm-1 in the MgSO4-rich droplets; the new ?1(SO42-) mode was predicted in previously published theoretical models to be present in MgSO4 polymers in aqueous solutions. Both the phase behavior with a lower critical solution temperature and the new Raman mode indicate the existence of polymers in MgSO4 solutions. MgSO4 can be commonly found as an important solute in formation waters involved in the thermochemical sulfate reduction (TSR), which is in close association with the preservation of petroleum in nature. Previous studies suggest that the presence of MgSO4 favors the activation of TSR, because Mg2+ and SO42- form contact ion pairs (CIPs) at elevated temperatures, and thus significantly increase the reactivity of sulfate. The recognization of the liquid-liquid phase separation and polymerization of MgSO4 in aqueous MgSO4 solutions has important consequences for laboratory simulations of TSR, that are commonly performed at T > 260 °C, because (1) the emergence of the MgSO4-rich droplets will substantially increase the local MgSO4 concentration, which is not representative of the geologic environments where TSR occurs; and (2) the formation of various ion pairs and MgSO4 polymers makes the mechanism of TSR far more complex than that which occurs at relatively low temperatures (i.e., <200 °C ) in petroleum reservoirs. These new observations improve our understanding of the speciation and transport of sulfates in aqueous solutions and enhance theoretical descriptions of divalent (or higher valence) electrolyte solutions in general and MgSO4 solutions in particular.

Chou, I.; Wang, X.; Hu, W.; Burruss, R. C.

2012-12-01

360

Influence of the Broadening of Vibrational Bands on the Relative Order of Their Molar Extinction Coefficients  

Microsoft Academic Search

The broadening of transitions in the spectra of organic molecules in the liquid phase, under perturbations whose type may be the solvation effects, causes changes of the molar extinction coefficients ?. The problem has been known for a longtime and several attempts have been made to produce a measure of the width of complex absorption spectra and of their fine

B. Vidal; C. Dupret; A. Darry-Henaut

1986-01-01

361

Electro-thermal treatment of high concentration ammonia in water by gaseous oxidation in liquid phase (GOLP).  

PubMed

Gaseous oxidation in liquid phase (GOLP) process was proposed to degrade high concentration ammonium in water. The innovative concept behind the reactor design is that the monocrystalline silicon chip coated with catalyst could be heated instantaneously by direct current, which will gasify the surrounding ammonium solution and later catalytically convert it to harmless N(2). It is found out that Co(3)O(4) instead of Co(2)O(3) is the active catalytic component in the GOLP process and it coats the silicon chip evenly with nut-shell particle. The experimental results reveal that the GOLP process could degrade high concentration NH(4)(+) efficiently, in which when the current was 10A, the reactor could remove almost 98% NH(4)(+) after 2h treatment, at the initial concentration 1810mgL(-1). The overall GOLP process for de-nitrification could be presumed to have two steps: (1) the gasification of liquid around catalyst; and (2) catalytic conversion of NH(4)(+) to N(2), which is experimentally demonstrated by Ion Chromatography data. Also, the influences of current and pH were investigated to optimize the operating parameters for the GOLP reactor, and the preliminary energy consumption analysis based on lab data was provided for future reference. These results show that the GOLP process will be able to sustain without extra energy input theoretically if the ammonia concentration is higher than 1.48%. PMID:20462628

Cao, Limei; Yang, Ji; Jia, Jinping

2010-06-01

362

Linear solvation energy relationship of the limiting partition coefficient of organic solutes between water and activated carbon  

USGS Publications Warehouse

A linear solvation energy relationship has been found for 353 values of the limiting adsorption coefficients of diverse chemicals:? log K = ?0.37 + 0.0341Vi ? 1.07? + D + 0.65P with R = 0.951, s = 0.51, n = 353, and F = 818.0, where Vi is the intrinsic molar volume; ? is a measure of the hydrogen bond acceptor strength of the solute; D is an index parameter for the research group which includes the effects of the different types of carbon used, the temperature, and the length of time allowed for the adsorption equilibrium to be established; and P is an index parameter for the flatness of the molecule. P is defined to be unity if there is an aromatic system in the molecule or if there is a double bond or series of conjugated double bonds with no more that one non-hydrogen atom beyond the double bond and zero otherwise. A slightly better fit is obtained if the two-thirds power of Vi is used as a measure of the surface area in place of the volume term:? log K = ?1.75 + 0.227V2/3 ? 1.10? + D + 0.60P with R = 0.954, s = 0.49, n = 353, and F = 895.39. This is the first quantitative measure of the effect of the shape of the molecule on its tendency to be adsorbed on activated carbon.

Luehrs, Dean C.; Hickey, James P.; Nilsen, Peter E.; Godbole, K. A.; Rogers, Tony N.

1995-01-01

363

Limiting activity coefficients of aqueous flavour systems at 298 K by the group contribution solvation (GCS) model  

NASA Astrophysics Data System (ADS)

In this work a new approach for using the GCS model is applied to predict the infinite dilution activity coefficients, ??, for aroma compounds in water. It involves the use of a better expression for the combinatorial contribution to ??, and a different treatment of the values of the ?-scaling factors used in the cavity size definition in the quantum chemical solvation calculations. The ? values for each functional group in the solvation calculations in water are optimized based on few experimental data of ??. The present approach is applied for describing aqueous systems of n-alkanols and methyl-ketones. The results discussed here show that the predicted ?? values are within the experimental accuracy for most of the compounds, and are more accurate than predictions using the classical UNIFAC-type group contribution models. Furthermore, a simple group contribution approach was developed based on quantum-computed quantities, which makes it possible to extend the applicability of the model without expensive quantum calculations. It is shown that such an approach is able to describe ?? well, even for larger systems.

Nanu, Diana E.; de Loos, Theodoor W.

364

Time correlation function approach to liquid phase vibrational energy relaxation: Dihalogen solutes in rare gas solvents  

NASA Astrophysics Data System (ADS)

A molecular theory of liquid phase vibrational energy relaxation (VER) [S. A. Adelman [et al.], Adv. Chem. Phys. 84, 73 (1993)] is applied to study the temperature T and density rho dependencies of the VER rate constant k(T,rho)=T1-1, where T1 is the energy relaxation time, of model Lennard-Jones systems that roughly simulate solutions of high-mass, low-frequency dihalogen solutes in rare gas solvents; specifically the I2/Xe, I2/Ar, and ICI/Xe solutions. For selected states of these systems, the theory's assumptions are tested against molecular dynamics (MD) results. The theory is based on the expression T1=beta]-1([omegal), where omegal and beta]([omega) are, respectively, the solute's liquid phase vibrational frequency and vibrational coordinate friction kernel. The friction kernel is evaluated as a cosine transform of the fluctuating force autocorrelation function of the solute vibrational coordinate, conditional that this coordinate is fixed at equilibrium. Additionally, the early-time decay of the force autocorrelation function is approximated by a Gaussian function which is exact to order t2. This Gaussian approximation permits evaluation of T1 in terms of integrals over equilibrium solute-solvent pair correlation functions. The pair correlation function formulas yield T1's in semiquantitative agreement with those found by MD evaluations of the Gaussian approximation, but with three orders of magnitude less computational effort. For the isothermal rho dependencies of k(T,rho), the theory predicts for all systems that the Gaussian decay time tau is nearly independent of rho. This in turn implies that k(T,rho) factorizes into a liquid phase structural contribution and a gas phase dynamical contribution, yielding a first-principles form for k(T,rho) similar to that postulated by the isolated binary collision model. Also, the theory predicts both "classical" superlinear rate isotherms, and "nonclassical" sublinear isotherms similar to those recently observed by Troe and co-workers for azulene relaxation in supercritical fluids. The isochoric T dependencies of k(T,rho) are studied in the range 300 to 1000 K. For none of the solutions are the rate isochores found to accurately conform to either Arrhenius or Landau-Teller kinetics.

Miller, David W.; Adelman, Steven A.

2002-08-01

365

Ethers from ethanol. 1: Equilibrium thermodynamic analysis of the liquid-phase ethyl tert-butyl ether reaction  

SciTech Connect

The equilibrium-limited liquid-phase synthesis of ethyl tert-butyl ether (ETBE) from the combination of ethanol and isobutylene over an ion-exchange resin catalyst, typically Amberlyst 15, is a reaction of considerable industrial importance now. An equilibrium constant relationship is developed here for the liquid-phase ETBE reaction by following three alternative thermodynamic pathways and critically evaluating the resulting expressions. The final theoretical expression is compared against experimental data obtained in this study from the decomposition of ETBE over Amberlyst 15, as well as that reported in the literature for ETBE synthesis. It can thus be used with reasonable confidence for the calculation of the equilibrium constant, despite a dearth of thermodynamic data yet available in the literature for ETBE. In addition, an expression is derived for the gas-phase equilibrium constant and compared to experimental data from the literature. The thermodynamic approach utilized here should also be useful for other liquid-phase reaction systems.

Jensen, K.L.; Datta, R. (Univ. of Iowa, Iowa City, IA (United States). Dept. of Chemical and Biochemical Engineering)

1995-01-01

366

Surface order at surfactant-laden interfaces between isotropic liquid crystals and liquid phases with different polarity  

NASA Astrophysics Data System (ADS)

We present an ellipsometry study of the interface between thermotropic liquid crystals and liquid phases consisting of various binary mixtures of water and glycerol. The liquid-crystal samples contain a small constant amount of a surfactant which induces a homeotropic anchoring at the interface. We determine the smectic or nematic order at the interface in the temperature range above the liquid-crystal-isotropic transition while the water to glycerol ratio is varied, corresponding to a systematic modification of the polarity of the liquid phase. The surface-induced order becomes less pronounced with increasing glycerol concentration in the liquid phase. The observed behavior is compared with previous studies in which the surfactant concentration in the liquid-crystal bulk phase was varied. The results indicate that in both cases the magnitude of the surfactant coverage at the interface is the key quantity which determines the liquid-crystal surface order at the interface.

Feng, Xunda; Bahr, Christian

2011-03-01

367

Modeling and processing of liquid-phase-sintered ?-TiAl during high-density infrared processing  

SciTech Connect

A new method for the rapid processing of thin gage sheet of traditionally difficult-to-process materials, such as y-TiAl, has been modeled and experimentally developed. The method uses high density infrared (HDI) rapid heating of a plasma arc lamp to liquid-phase sinter powder metal compact precursors to structures of varying densities. Material properties for precursor y-TiAl compacts were effectively chosen or determined and then used with a finite-volume heat-transfer modeling code to model the process. With the aid of the model, processing parameters were determined that allowed for a temperature gradient across the sheet that would produce a liquid-phase cast structure on the surface, residual powder on the backside, and a middle layer solid + liquid zone. Temperature and phase fields were predicted through the thickness of the sheet using the model. Fine grain, lamellar structured materials were produced in the liquid-phase-sintered zone.

Sabau, Adrian S [ORNL; Blue, Craig A [ORNL

2006-01-01

368

Pumice-supported Pd-Pt bimetallic catalysts: Synthesis, structural characterization, and liquid-phase hydrogenation of 1,3-cyclooctadiene  

SciTech Connect

A series of pumice-supported palladium-platinum bimetallic catalysts were prepared and investigated by X-ray scattering (WAXS and SAXS) and XPS techniques. An alloy Pd-Pt was formed. The less abundant metal was found to segregate to the surface. The catalysts were tested in the liquid-phase hydrogenation of 1,3-cyclooctadiene to cyclooctene, and compared with similarly prepared pumice-supported palladium and platinum catalysts and other supported Pd-Pt catalysts reported in the literature. The addition of platinum reduces the activity and the selectivity of the palladium catalysts. Differences between the activity of these pumice-supported catalysts and the activity of previously described Pd and Pd-Pt catalysts on other supports, are attributed to the presence, in the latter, of diffusional processes. 50 refs., 4 figs. 2 tabs.

Deganello, G.; Duca, D.; Liotta, L.F.; Martorana, A.; Venezia, M. [Istituto di Chimica e Technologia dei Prodotti Naturali del CNR, Palermo (Italy)] [Istituto di Chimica e Technologia dei Prodotti Naturali del CNR, Palermo (Italy); Benedetti, A.; Fagherazz, G. [Universita di Venezia, Venice (Italy)] [Universita di Venezia, Venice (Italy)

1995-01-01

369

Liquid-liquid phase separation in particles containing organics mixed with ammonium sulfate, ammonium bisulfate, ammonium nitrate or sodium chloride  

NASA Astrophysics Data System (ADS)

As the relative humidity varies from high to low values in the atmosphere, particles containing organic species and inorganic salts may undergo liquid-liquid phase separation. The majority of the laboratory work on this subject has used ammonium sulfate as the inorganic salt. In the following we studied liquid-liquid phase separation in particles containing organics mixed with the following salts: ammonium sulfate, ammonium bisulfate, ammonium nitrate and sodium chloride. In each experiment one organic was mixed with one inorganic salt and the liquid-liquid phase separation relative humidity (SRH) was determined. Since we studied 23 different organics mixed with four different salts, a total of 92 different particle types were investigated. Out of the 92 types, 49 underwent liquid-liquid phase separation. For all the inorganic salts, liquid-liquid phase separation was never observed when the oxygen-to-carbon elemental ratio (O : C) ≥ 0.8 and was always observed for O : C < 0.5. For 0.5 ≤ O : C < 0.8, the results depended on the salt type. Out of the 23 organic species investigated, the SRH of 20 organics followed the trend: (NH4)2SO4 ≥ NH4HSO4 ≥ NaCl ≥ NH4NO3. This trend is consistent with previous salting out studies and the Hofmeister series. Based on the range of O : C values found in the atmosphere and the current results, liquid-liquid phase separation is likely a frequent occurrence in both marine and non-marine environments.

You, Y.; Renbaum-Wolff, L.; Bertram, A. K.

2013-12-01

370

Liquid-liquid phase separation in particles containing organics mixed with ammonium sulfate, ammonium bisulfate, ammonium nitrate or sodium chloride  

NASA Astrophysics Data System (ADS)

As the relative humidity varies from high to low values in the atmosphere, particles containing organics and inorganic salts may undergo liquid-liquid phase separation. The majority of the laboratory work on this subject has used ammonium sulfate as the inorganic salt. In the following we studied liquid-liquid phase separation in particles containing organics mixed with the following salts: ammonium sulfate, ammonium bisulfate, ammonium nitrate and sodium chloride. In each experiment one organic was mixed with one inorganic salt and the liquid-liquid phase separation relative humidity (SRH) was determined. Since we studied 23 different organics mixed with four different salts, a total of 92 different particle types were investigated. Out of the 92 types, 49 underwent liquid-liquid phase separation. For all the inorganic salts, liquid-liquid phase separation was never observed when the oxygen-to-carbon elemental ratio (O:C) was ? 0.8 and was always observed for O:C<0.5. For 0.5 ? O:C< 0.8, the results depended on the salt type. Out of the 23 organics investigated, the SRH of 20 organics followed the trend: (NH4)2SO4 ? NH4HSO4 ? NaCl ? NH4NO3. This trend is consistent with previous salting-out studies and the Hofmeister series. Based on the range of O:C values found in the atmosphere and the current results, liquid-liquid phase separation is likely a frequent occurrence in both marine and non-marine environments.

You, Y.; Renbaum-Wolff, L.; Bertram, A. K.

2013-07-01

371

Surface Specularity as an Indicator of Shock-induced Solid-liquid Phase Transitions in Tin  

SciTech Connect

When highly polished metal surfaces melt upon release after shock loading, they exhibit features that suggest significant surface changes accompany the phase transition. The reflection of light from such surfaces changes from specular (pre-shock) to diffuse upon melting. Typical of this phenomenon is the loss of signal light in velocity interferometer system for any reflector (VISAR) measurements, which usually occurs at pressures high enough to melt the free surface. Unlike many other potential material phase-sensitive diagnostics (e.g., reflectometry, conductivity), that show relatively small (1%-10%) changes, the specularity of reflection provides a more sensitive and definitive (>10x) indication of the solid-liquid phase transition. Data will be presented that support the hypothesis that specularity changes indicate melt in a way that can be measured easily and unambiguously.

G. D. Stevens, S. S. Lutz, B. R. Marshall, W.D. Turley, et al.

2007-12-01

372

Near infrared photoluminescence observed in dilute GaSbBi alloys grown by liquid phase epitaxy  

NASA Astrophysics Data System (ADS)

We report the first observation of photoluminescence (PL) from the dilute bismide alloy GaSbBi. Epitaxial layers are grown by liquid phase epitaxy technique onto GaSb (1 0 0) substrates and PL is obtained in the near infrared spectral range ( ? ˜ 1.6 ?m). Incorporation of 0.2, 0.3 and 0.4 at% Bi to the layer results in a decrease of band gap energy up to 40 meV as well as an increase of luminescence from the sample. Structural analysis confirms the successful incorporation of Bi consistent with an increase in lattice parameter. Raman spectroscopy measurements indicate vibrational modes due to GaBi as well as to free Bi atoms residing at interstitial spaces.

Das, S. K.; Das, T. D.; Dhar, S.; de la Mare, M.; Krier, A.

2012-01-01

373

Simulation studies on the liquid phase electroepitaxial growth of III V compound semiconductors  

NASA Astrophysics Data System (ADS)

In this paper, the growth kinetics of liquid phase electroepitaxy of III-V binary and ternary compound semiconductors have been studied. Concentration profiles of solute atoms such as As, P, Sb in front of a crystal (GaAs, InP, InAs, GaSb) interface growing in a In- or Ga-rich solution for the case of growth of binary compounds and for the case of ternary compounds (InGaAs, AlGaSb, InAsP) have been constructed using a computer simulation technique. The effect due to Peltier heating or cooling and electromigration during the growth have been incorporated to simulate the concentration profiles. The growth velocity in the absence and presence of convection, due to the Peltier effect and electromigration are calculated under different conditions. The results are discussed in detail.

Dhanasekaran, R.; Qhalid Fareed, R. S.; Ramasamy, P.

2001-07-01

374

Mono-crystalline silicon strips grown by liquid phase epitaxy for photovoltaic applications  

NASA Astrophysics Data System (ADS)

We have studied epitaxial lateral overgrowth of p-type silicon by Liquid Phase Epitaxy (LPE) on n-type (111) silicon substrates from a Si/In melt. The substrate had a silicon dioxide mask with a set of parallel opening windows for seed lines which were aligned along a [211]direction. The growth parameters, morphology and electrical properties of the grown crystal were studied. Two single crystalline silicon strips were formed on one single seed line, one strip on either side of the seed line, demonstrating that silicon is more likely to deposit near the interface between the silicon and the oxide. All facets of the strips are {111} planes and therefore the bottom surface has a 4 degree angle with the substrate, providing convenience for the epitaxial layer to be peeled off from the substrate and used for potential photovoltaic applications. Monte Carlo random walk model is used to simulate the epitaxial growth of the mono-crystalline strips.

Li, Bo; Kitai, Adrian H.

2010-06-01

375

Headspace liquid phase microextraction for quantitation of hexanal in potato crisps by gas chromatography.  

PubMed

A simple and rapid method using headspace liquid-phase microextraction (HS-LPME) was developed for the determination of hexanal at low levels in potato crisp samples. Parameters such as extraction solvent, agitation of the sample, salt addition, organic drop volume, exposure time, and extraction time were controlled and optimised. The developed protocol was found to yield a linear calibration curve in the concentration range from 0.001 to 2 mg/L and a limit of detection of 0.1 microg/L with a good enrichment factor of > 107 for the analyte. The repeatability of the method was satisfactory (4%). The results demonstrate that HS-LPME is a rapid, accurate, and effective preparation method and could be successfully used for the determination of hexanal in potato crisp samples. PMID:17444226

Kaykhaii, Massoud; Rahmani, Mashaallah

2007-03-01

376

Methods for sulfate removal in liquid-phase catalytic hydrothermal gasification of biomass  

DOEpatents

Processing of wet biomass feedstock by liquid-phase catalytic hydrothermal gasification must address catalyst fouling and poisoning. One solution can involve heating the wet biomass with a heating unit to a pre-treatment temperature sufficient for organic constituents in the feedstock to decompose, for precipitates of inorganic wastes to form, for preheating the wet feedstock in preparation for subsequent removal of soluble sulfate contaminants, or combinations thereof. Processing further includes reacting the soluble sulfate contaminants with cations present in the feedstock material to yield a sulfate-containing precipitate and separating the inorganic precipitates and/or the sulfate-containing precipitates out of the wet feedstock. Having removed much of the inorganic wastes and the sulfate contaminants that can cause poisoning and fouling, the wet biomass feedstock can be exposed to the heterogenous catalyst for gasification.

Elliott, Douglas C; Oyler, James

2013-12-17

377

Liquid-phase exfoliation of expanded graphites into graphene nanoplatelets using amphiphilic organic molecules.  

PubMed

Graphenes with a two-dimensional lattice of carbons have been widely employed in diverse applications owing to their excellent electrical, thermal, mechanical, and gas-barrier properties. However, the frequently-used reduced graphene oxide (rGO), which is synthesized from natural graphites by strong oxidation and subsequent reduction via highly toxic components, exhibits imperfect characteristics because of remaining defect sites on its basal planes. Therefore, in this work, we present a convenient way to prepare graphene nanoplatelets (GNPs) with minimized defect sites on their basal planes employing liquid-phase exfoliation of edge-functionalized expanded graphites (EGs) with amphiphilic organic molecules. Exfoliated GNPs revealed approximately sub-7-nm-thickness and showed stable dispersibility in an organic media during 9 months. Furthermore, spray-coated GNP films presented homogeneously stacked morphologies without noticeable agglomerations. PMID:24407700

Park, Ji Sun; Yu, Lan; Lee, Churl Seung; Shin, Kwonwoo; Han, Jong Hun

2014-03-01

378

Surface Specularity as an Indicator of Shock-Induced Solid-Liquid Phase Transitions  

SciTech Connect

When highly polished metal surfaces melt upon release after shock loading, they exhibit a number of features that suggest that significant surface changes accompany the phase transition. The reflection of light from such surfaces changes from specular (pre-shock) to diffuse upon melting. A familiar manifestation of this phenomenon is the loss of signal light in velocimetric measurements typically observed above pressures high enough to melt the free-surface. Unlike many other potential material phase-sensitive diagnostics (e.g., reflectometery, conductivity), changes in the specularity of reflection provide a dramatic, sensitive indicator of the solid-liquid phase transition. Data will be presented from multiple diagnostics that support the hypothesis that specularity changes indicate melt. These diagnostics include shadowgraphy, infrared imagery, high-magnification surface images, interferometric velocimetry, and most recently scattering angle measurements.

Gerald Stevens, Stephen Lutz, William Turley, Lynn Veeser

2007-06-29

379

An overview of liquid phase microextraction approaches combined with UV-Vis spectrophotometry.  

PubMed

Ultraviolet and visible spectrophotometer has become a popular analytical instrument in the modern day laboratories. However, the low concentrations of many analytes in samples make it difficult to directly measure them by UV-Vis spectrophotometry. This overview focuses on the combinations of microvolume UV-Vis spectrophotometry with miniaturized approaches to sample preparation, namely, single drop microextraction (SDME), dispersive liquid-liquid microextraction (DLLME), cold induced aggregation microextraction (CIAME), in situ solvent formation microextraction (ISSFME), ultrasound assisted emulsification microextraction (USAEME), solidified floating organic drop microextraction (SFODME), and hollow fiber based liquid phase microextraction (HF-LPME) to improve both the selectivity and sensitivity. Integration of these techniques provides unique advantages which include availability, simplicity of operation, low cost, speed, precision and accuracy; hence making them a powerful tool in chemical analysis. PMID:22967514

Dehghani Mohammad Abadi, Malihe; Ashraf, Narges; Chamsaz, Mahmoud; Shemirani, Farzaneh

2012-09-15

380

Crystallization and phase changes in paracetamol from the amorphous solid to the liquid phase.  

PubMed

For the case of paracetamol, we show how terahertz time-domain spectroscopy can be used to characterize the solid and liquid phase dynamics. Heating of supercooled amorphous paracetamol from 295 K in a covered sample under vacuum leads to its crystallization at 330 K. First, form III is formed followed by the transformation of form III to form II at 375 K, to form I at 405 K, and finally melting is observed around 455 K. We discuss the difference between the featureless spectra of the supercooled liquid and its liquid melt. Lastly, we studied the onset of crystallization from the supercooled liquid in detail and quantified its kinetics based on the Avrami-Erofeev model. We determined an effective rate constant of k = 0.056 min(-1) with a corresponding onset of crystallization at T = 329.5 K for a heating rate of 0.4 K min(-1). PMID:24579729

Sibik, Juraj; Sargent, Michael J; Franklin, Miriam; Zeitler, J Axel

2014-04-01

381

Spectroscopic-ellipsometric study of native oxide removal by liquid phase HF process  

PubMed Central

Ex situ spectroscopic ellipsometry (SE) measurements have been employed to investigate the effect of liquid-phase hydrofluoric acid (HF) cleaning on Si<100> surfaces for microelectromechanical systems application. The hydrogen terminated (H-terminated) Si surface was realized as an equivalent dielectric layer, and SE measurements are performed. The SE analyses indicate that after a 20-s 100:5 HF dip with rinse, the Si (100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si (100) surface was observed and analyzed by the ex-situ SE. Evidence for desorption of the H-terminated Si surface layer is studied using Fourier transform infrared spectroscopy and ellipsometry, and discussed. This piece of work explains the usage of an ex situ, non-destructive technique capable of showing state of passivation, the H-termination of Si<100> surfaces.

Kurhekar, Anil Sudhakar; Apte, Prakash R

2014-01-01

382

Programmed functionalization of SURMOFs via liquid phase heteroepitaxial growth and post-synthetic modification.  

PubMed

Heterostructured surface mounted metal-organic frameworks (SURMOFs) [Cu2(NH2-bdc)2(dabco)] (B) on top of [Cu2(bdc)2(dabco)] (A) were deposited on pyridyl-terminated Au covered QCM substrate using a step-by-step liquid phase epitaxial growth method. Sequentially, the pore size of the top layer [Cu2(NH2-bdc)2(dabco)] (B) was modified by targeting the installed amino moiety with tert-butyl isothiocyanate (tBITC). The adsorption properties of the programmed functionalized SURMOFs studied using an environment controlled quartz crystal microbalance (QCM) instrument exhibited the possibility to achieve high selectivity and capacity by heteroepitaxial growth and post-synthetic modification. PMID:23929225

Tu, Min; Wannapaiboon, Suttipong; Fischer, Roland A

2013-12-01

383

Heterogeneous inhibition of the liquid phase oxidation of hydrocarbons by molybdenum compounds  

SciTech Connect

The heterogeneous action of molybdenum compounds: MoB, MoSe/sub 2/, MoSi/sub 2/, Mo/sub 2/C, MoO/sub 3/, Mo on the oxidation of n-decane, ethylbenzene, and nonene-1 has been investigated. A parameter representing the inhibiting effect of the heterogeneous catalyst was calculated theoretically. It was found that NoB, MoSe/sub 2/, and MoSi/sub 2/ inhibited the oxidation of n-decane at 408 K while the remaining heterogeneous contacts catalyzed it. A critical phenomenon was detected in the inhibition by MoSi/sub 2/. All the molybdenum compounds investigated inhibited the oxidation of ethylbenzene at 393 K owing to the formation of phenol by catalytic decomposition of the hydroperoxide. The liquid phase oxidation autoinhibited by phenol is described theoretically.

Tavadyan, L.A.; Karapetyan, A.P.; Madatovyan, V.M.

1988-05-01

384

Indication of liquid-liquid phase transition in CuZr-based melts  

NASA Astrophysics Data System (ADS)

We study the dynamic behavior of CuZr-based melts well above the liquidus temperature. The results show a discontinuous change in viscosity during cooling, which is attributed to an underlying liquid-liquid phase transition (LLPT) in these melts. The LLPT is further verified by thermodynamic response in the same temperature region. We find that the LLPT in the Cu46Zr46Al8 melt is reversible above 1350 K upon repeated heating and cooling. Based on the concept of fluid cluster in metallic melts, the reversible LLPT is attributed to the structural transition from the strongly ordered high-density liquids to the weak-local low-density liquids upon cooling.

Zhou, Chao; Hu, Lina; Sun, Qijing; Qin, Jingyu; Bian, Xiufang; Yue, Yuanzheng

2013-10-01

385

High-Quality Crystalline Silicon Layer Grown by Liquid Phase Epitaxy Method at Low Growth Temperature  

NASA Astrophysics Data System (ADS)

We investigated the effect of growth temperature on crystal quality of crystalline silicon layers grown by liquid phase epitaxy (LPE) with gold-bismuth binary alloy solvent. The electrical and structural properties were examined by means of minority-carrier lifetime measurement and micro-Raman scattering spectroscopy. Both electrical and structural qualities improve with decreasing growth temperature. In the present study, the lifetime of the silicon layer grown at the lowest temperature was higher than that of monocrystalline silicon substrate though the solvent includes gold which is a well-known strong recombination site. On the other hand, the structural quality of layers is inferior to that of the substrate even at the lowest growth temperature. Thus, the temperature dependence of lifetime was concluded to be mainly due to the reduction of the solubility of gold impurity in the layer rather than the improvement of structural quality.

Ujihara, Toru; Obara, Kazuo; Usami, Noritaka; Fujiwara, Kozo; Sazaki, Gen; Shishido, Toetsu; Nakajima, Kazuo

2003-03-01

386

Method for forming single phase, single crystalline 2122 BCSCO superconductor thin films by liquid phase epitaxy  

NASA Technical Reports Server (NTRS)

A substantially single phase, single crystalline, highly epitaxial film of Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor which has a T.sub.c (zero resistance) of 83 K is provided on a lattice-matched substrate with no intergrowth. This film is produced by a Liquid Phase Epitaxy method which includes the steps of forming a dilute supercooled molten solution of a single phase superconducting mixture of oxides of Bi, Ca, Sr, and Cu having an atomic ratio of about 2:1:2:2 in a nonreactive flux such as KCl, introducing the substrate, e.g., NdGaO.sub.3, into the molten solution at 850.degree. C., cooling the solution from 850.degree. C. to 830.degree. C. to grow the film and rapidly cooling the substrate to room temperature to maintain the desired single phase, single crystalline film structure.

Pandey, Raghvendra K. (Inventor); Raina, Kanwal (Inventor); Solayappan, Narayanan (Inventor)

1994-01-01

387

Liquid-phase deposition of thin Si films by ballistic electro-reduction  

NASA Astrophysics Data System (ADS)

It is shown that the nanocryatalline silicon ballistic electron emitter operates in a SiCl4 solution without using any counter electrodes and that thin amorphous Si films are efficiently deposited on the emitting surface with no contaminations and by-products. Despite the large electrochemical window of the SiCl4 solution, electrons injected with sufficiently high energies preferentially reduce Si4+ ions at the interface. Using an emitter with patterned line emission windows, a Si-wires array can be formed in parallel. This low-temperature liquid-phase deposition technique provides an alternative clean process for power-effective fabrication of advanced thin Si film structures and devices.

Ohta, T.; Gelloz, B.; Kojima, A.; Koshida, N.

2013-01-01

388

Direct ampholyte-free liquid-phase isoelectric peptide focusing: application to the human serum proteome.  

PubMed

In this study, we utilized a multidimensional peptide separation strategy combined with tandem mass spectrometry (MS/MS) for the identification of proteins in human serum. After enzymatically digesting serum with trypsin, the peptides were fractionated using liquid-phase isoelectric focusing (IEF) in a novel ampholyte-free format. Twenty IEF fractions were collected and analyzed by reversed-phase microcapillary liquid chromatography (microLC)-MS/MS. Bioinformatic analysis of the raw MS/MS spectra resulted in the identification of 844 unique peptides, corresponding to 437 proteins. This study demonstrates the efficacy of ampholyte-free peptide autofocusing, which alleviates peptide losses in ampholyte removal strategies. The results show that the separation strategy is effective for high-throughput characterization of proteins from complex proteomic mixtures. PMID:14730577

Xiao, Zhen; Conrads, Thomas P; Lucas, David A; Janini, George M; Schaefer, Carl F; Buetow, Kenneth H; Issaq, Haleem J; Veenstra, Timothy D

2004-01-01

389

Liquid Phase – Pulsed Laser Ablation: A route to fabricate different carbon nanostructures  

NASA Astrophysics Data System (ADS)

Carbon nanostructures in various forms and sizes, and with different speciation properties have been prepared from graphite by Liquid Phase - Pulsed Laser Ablation (LP-PLA) using a high frequency Nd:YAG laser. High energy densities and pulse repetition frequencies of up to 10 kHz were used in this ablation process to produce carbon nanomaterials with unique chemical structures. Dynamic Light Scattering (DLS), micro-Raman and High-Resolution Transmission Electron Microscopy (HRTEM) were used to confirm the size distribution, morphology, chemical bonding, and crystallinity of these nanostructures. This article demonstrates how the fabrication process affects measured characteristics of the produced carbon nanomaterials. The obtained particle properties have potential use for various applications including biochemical speciation applications.

Al-Hamaoy, Ahmed; Chikarakara, Evans; Jawad, Hussein; Gupta, Kapil; Kumar, Dinesh; Rao, M. S. Ramachandra; Krishnamurthy, Satheesh; Morshed, Muhammad; Fox, Eoin; Brougham, Dermot; He, Xiaoyun; Vázquez, Mercedes; Brabazon, Dermot

2014-05-01

390

Microgravity studies in the liquid phase immiscible system, aluminum-indium  

NASA Technical Reports Server (NTRS)

As part of a study to understand the influence of gravity, cooling rate and composition on the structure of liquid phase immiscible materials, two alloys, Al-40 wt % In and Al-70 wt % In were thermally treated on the SPAR II rocket flight. The treatments involved homogenization at a temperature above the miscibility gap and then rapid cooling through the miscibility gap followed by complete solidification. The last two steps were performed while acceleration levels were less than 4 x 10 to the -5th g. The flight alloys produced unexpected results. Instead of fine uniform structures, the alloys consisted of a macroscopically sized aluminum-rich central region surrounded by indium-rich metal.

Gelles, S. H.; Markworth, A. J.

1977-01-01

391

Gas-liquid phase separation in oppositely charged colloids: Stability and interfacial tension  

NASA Astrophysics Data System (ADS)

We study the phase behavior and the interfacial tension of the screened Coulomb (Yukawa) restricted primitive model (YRPM) of oppositely charged hard spheres with diameter ? using Monte Carlo simulations. We determine the gas-liquid and gas-solid phase transitions using free energy calculations and grand-canonical Monte Carlo simulations for varying inverse Debye screening length ?. We find that the gas-liquid phase separation is stable for ??<=4, and that the critical temperature decreases upon increasing the screening of the interaction (decreasing the range of the interaction). In addition, we determine the gas-liquid interfacial tension using grand-canonical Monte Carlo simulations. The interfacial tension decreases upon increasing the range of the interaction. In particular, we find that simple scaling can be used to relate the interfacial tension of the YRPM to that of the restricted primitive model, where particles interact with bare Coulomb interactions.

Fortini, Andrea; Hynninen, Antti-Pekka; Dijkstra, Marjolein

2006-09-01

392

Ultrasound-assisted third-liquid phase-transfer catalyzed esterification of sodium salicylate in a continuous two-phase-flow reactor  

Microsoft Academic Search

The esterification of sodium salicylate to synthesize butyl salicylate by third-liquid phase-transfer catalysis under ultrasound irradiation was investigated in a continuous two-phase-flow reactor. The reactor was designed to keep the third-liquid phase in the middle part and to have the aqueous and organic phases flowing through it in countercurrent. Using tetra-n-butylphosphonium bromide to prepare the third-liquid phase for this esterification,

Hung-Ming Yang; Guan-Yi Peng

2010-01-01

393

Determination of volatile residual solvents in pharmaceutical products by headspace liquid-phase microextraction gas chromatography-flame ionization detector.  

PubMed

This paper demonstrates headspace liquid-phase microextraction (HS-LPME) as used for the determination of volatile residual solvents in pharmaceutical products. This method is based on headspace liquid-phase microextraction capillary column gas chromatography. Under optimum conditions, the linerary of the method ranged from 1 to 1,000 mg l(-1). The limits of detection are 0.2-6.0 [corrected] mg l(-1) and relative standard deviations (RSD) for most of the volatile solvents were below 10%. This novel method is applied to the analysis of volatile residual solvents in pharmaceutical products with satisfactory results. PMID:16770579

Wang, Xia; Jiang, Ting; Yuan, Jinpeng; Cheng, Chuange; Liu, Jianhua; Shi, Junbo; Zhao, Rusong

2006-07-01

394

Condensation Coefficient: Definitions, Estimations, Modern Experimental and Calculation Data  

NASA Astrophysics Data System (ADS)

A brief analysis of different approaches to the calculation and measurement of the condensation coefficient of a vapor is presented. It is shown that, on frequent occasions, calculations give values of this coefficient that are at variance with the corresponding experimental data and that the condensation coefficient is determined most exactly on the basis of the molecular-kinetic theory. It was established that the spread in the literature data on the measured values of this coefficient is explained mainly by the fact that these values were obtained not in the immediate vicinity from the boundary between the gas and liquid phases but at a large distance (as compared to the mean free path of molecules) from it. Results of calculations of the condensation coefficient of argon by the method of moleculardynamic simulation are presented.

Kryukov, A. P.; Levashov, V. Yu.; Pavlyukevich, N. V.

2014-01-01

395

Osmotic and Activity Coefficients of the {xZnCl2 + (1 - x)ZnSO4}(aq) System at 298.15 K  

SciTech Connect

Isopiestic vapor pressure measurements were made for (xZnCl{sub 2} + (1 - x)ZnSO{sub 4})(aq) solutions with ZnCl{sub 2} molality fractions of x = (0, 0.3062, 0.5730, 0.7969, and 1) at the temperature 298.15 K, using KCl(aq) as the reference standard. These measurements cover the water activity range 0.901-0.919 {le} a{sub w} {le} 0.978. The experimental osmotic coefficients were used to evaluate the parameters of an extended ion-interaction (Pitzer) model for these mixed electrolyte solutions. A similar analysis was made of the available activity data for ZnCl{sub 2}(aq) at 298.15 K, while assuming the presence of equilibrium amounts of ZnCl{sup +}(aq) ion-pairs, to derive the ion-interaction parameters for the hypothetical pure binary electrolytes (Zn{sup 2+}, 2Cl{sup -}) and (ZnCl{sup +},Cl{sup -}). These parameters are required for the analysis of the mixture results. Although significant concentrations of higher-order zinc chloride complexes may also be present in these solutions, it was possible to represent the osmotic coefficients accurately by explicitly including only the predominant complex ZnCl{sup +}(aq) and the completely dissociated ions. The ionic activity coefficients and osmotic coefficients were calculated over the investigated molality range using the evaluated extended Pitzer model parameters.

Ninkovic, R; Miladinovic, J; Todorovic, M; Grujic, S; Rard, J A

2006-06-27

396

Direct hydration of propylene in liquid phase and under supercritical conditions in the presence of solid acid catalysts  

Microsoft Academic Search

Hydration of propylene has been studied in both liquid phase conditions and above the critical temperature and pressure of propylene. There is a significant rise in initial rate while switching over from sub-critical to supercritical conditions, mainly because of the increase in solubility of propylene in water. Substantial amount of isopropanol exists in the supercritical phase. This suggests the possibility

S. M Mahajani; M. M Sharma; T Sridhar

2002-01-01

397

Effect of Fluorine Concentration on the Metal-Insulator-Semiconductor (MIS) Solar Cell Output Performance by Liquid Phase Deposition  

Microsoft Academic Search

Metal-insulator-semiconductor (MIS) solar cells with the insulating layer fabricated by liquid phase deposition (LPD) method has been shown to have good output performance in various literature published. In this paper, a high quality insulating layer is developed via LPD method with the fluorine content controlled by the growth solution concentration. The addition of fluorine to enhance the solar cell efficiency

Chien-Jung Huang; Mau-Phon Houng; Yeong-Her Wang; Na-Fu Wang; Wai-Jyh Chang

1998-01-01

398

Consequences of metallic fuel-cladding liquid phase attack during over-temperature transient on fuel element lifetime  

Microsoft Academic Search

Metallic fuel elements irradiated in EBR-II at temperatures significantly higher than design, causing liquid phase attack of the cladding, were subsequently irradiated at normal operating temperatures to first breach. The fuel element lifetime was compared to that for elements not subjected to the over-temperature transient and found to be equivalent. 1 ref., 3 figs.

C. E. Lahm; J. F. Koenig; B. R. Seidel

1990-01-01

399

Transient liquid phase bonding of Inconel 718 and Inconel 625 with BNi-2: Modeling and experimental investigations  

Microsoft Academic Search

In this study, a combination of direct experimentation and computational modeling approach was used to predict the time required to complete isothermal solidification during the transient liquid phase bonding of Inconel 718 and 625 superalloys, two most commonly used superalloys in aero-engine hot section components, with nickel based filler alloy, BNi-2. However, unlike conventional modeling, the diffusion of solute atoms

M. A. Arafin; M. Medraj; D. P. Turner; P. Bocher

2007-01-01

400

Systems and tanks therefor for storing products in the liquid phase that are normally in the gas phase  

Microsoft Academic Search

A system is described for storing in the liquid phase a product that is entirely in the gas phase under atmospheric pressure and ambient temperature conditions. It includes an upstanding storage tank that is hermetically sealed and is heat-insulated on the bottom wall and side wall, an upstanding tube in the center of the tank guiding a floating roof that

Mair

1970-01-01

401

Continuous Crystallization of Sulfur Formed by the Liquid-Phase Reaction of Hydrogen Sulfide and Sulfur Dioxide.  

National Technical Information Service (NTIS)

The crystallization of elemental sulfur is a unit operation in a process being developed to remove hydrogen sulfide from industrial gas streams. The sulfur is formed by the irreversible, liquid-phase reaction of hydrogen sulfide (H(sub 2)S) and sulfur dio...

C. A. Stevens S. Lynn

1989-01-01

402

Use of a CCD camera for the thermographic study of a transient liquid phase bonding process in steel  

Microsoft Academic Search

The bonding of steel pieces and the development of novel soldering methods, appropriate to the extended variety of applications of steels nowadays, bring the sensing of temperature an outstanding role in any metallurgical process. Transient liquid phase bonding (TLPB) processes have been successfully employed to join metals, among them steels. A thin layer of metal A, with a liquids temperature

Eduardo H. Castro; Carlos Epelbaum; Angel Carnero; Bibiana Arcondo

2001-01-01

403

Leveraging the Ambipolar Transport in Polymeric Field-Effect Transistors via Blending with Liquid-Phase Exfoliated Graphene.  

PubMed

Enhancement in the ambipolar behavior of field-effect transistors based on an n-type polymer, P(NDI2OD-T2), is obtained by co-deposition with liquid-phase exfoliated graphene. This approach provides a prospective pathway for the application of graphene-based nanocomposites for logic circuits. PMID:24862253

El Gemayel, Mirella; Haar, Sébastien; Liscio, Fabiola; Schlierf, Andrea; Melinte, Georgian; Milita, Silvia; Ersen, Ovidiu; Ciesielski, Artur; Palermo, Vincenzo; Samorì, Paolo

2014-07-01

404

Efficient catalyst removal and recycling in copolymerization of epoxides with carbon dioxide via simple liquid-liquid phase separation.  

PubMed

A simple and efficient catalyst removal system has been developed in the cobalt-salen-catalyzed copolymerization of propylene oxide with carbon dioxide. The present system requires no prior modification of the catalyst, and the removal is achieved by simple addition of myristic acid, followed by organic liquid-liquid phase separation. PMID:23999689

Nakano, Koji; Fujie, Ryuhei; Shintani, Ryo; Nozaki, Kyoko

2013-10-18

405

Prediction of activity coefficients in liquid aerosol particles containing organic compounds, dissolved inorganic salts, and water—Part 2: Consideration of phase separation effects by an X-UNIFAC model  

Microsoft Academic Search

A thermodynamic model is presented for predicting the formation of particulate matter (PM) within an aerosol that contains organic compounds, inorganic salts, and water. Neutral components are allowed to partition from the gas phase to the PM, with the latter potentially composed of both a primarily aqueous (?) liquid phase and a primarily organic (?) liquid phase. Partitioning is allowed

Elsa I. Chang; James F. Pankow

2006-01-01

406

Phase diagrams and kinetics of solid-liquid phase transitions in crystalline polymer blends  

NASA Astrophysics Data System (ADS)

A free energy functional has been formulated based on an order parameter approach to describe the competition between liquid-liquid phase separation and solid-liquid phase separation. In the free energy description, the assumption of complete solvent rejection from the crystalline phase that is inherent in the Flory diluent theory was removed as solvent has been found to reside in the crystalline phase in the form of intercalates. Using this approach, we have calculated various phase diagrams in binary blends of crystalline and amorphous polymers that show upper or lower critical solution temperature. Also, the discrepancy in the chi values obtained from different experimental methods reported in the literature for the polymer blend of poly(vinylidenefluoride) and poly(methylmethacrylate) has been discussed in the context of the present model. Experimental phase diagram for the polymer blend of poly(caprolactone) and polystyrene has also been calculated. Of particular importance is that the crystalline phase concentration as a function of temperature has been calculated using free energy minimization methods instead of assuming it to be pure. In the limit of complete immiscibility of the solvent in the crystalline phase, the Flory diluent theory is recovered. The model is extended to binary crystalline blends and the formation of eutectic, peritectic and azeotrope phase diagrams has been explained on the basis of departure from ideal solid solution behavior. Experimental eutectic phase diagram from literature of a binary blend of crystalline polymer poly(caprolactone) and trioxane were recalculated using the aforementioned approach. Furthermore, simulations on the spatio temporal dynamics of crystallization in blends of crystalline and amorphous polymers were carried out using the Ginzburg-Landau approach. These simulations have provided insight into the distribution of the amorphous polymer in the blends during the crystallization process. The simulated results are in close accordance with the experimentally observed concentration profiles of atactic polypropylene during the crystallization of isotactic polypropylene in a blend of these polymers. Finally described are the unique thermodynamics and kinetics that occur in thermoplastic elastomer blends of polypropylene and synthetic rubber, leading to the unique biphasic crystalline morphology imparting these blends with their characteristic high toughness and high impact strength. Phase diagrams in such blends exhibit a combined upper and lower critical solution temperature. These phase diagrams have been calculated based on the present model developed, and simulated results explain the structural development in these blends.

Matkar, Rushikesh A.

407

Transient liquid phase bonding as a joining technique for high-temperature power electronics  

NASA Astrophysics Data System (ADS)

Fundamental aspects of transient liquid phase (TLP) bonding in the Cu-Sn system have been studied, with the objective of assessing the utility of the bonding technique in joining high-temperature SiC devices to direct bond copper (DBC) substrates in power electronic packages. This technique can be implemented at relatively low temperatures (in comparison to the melting point of Cu), yet provide bonds that have composition and properties that are similar to those of Cu. The bonding parameters of time, temperature, and interlayer thickness were probed. Additionally, two methods for the introduction of the interlayer were used: one based on the use of foils and the other based on electron beam deposition. The resulting microstructures were characterized using scanning electron microscopy and energy dispersive X-ray analysis. Microstructures consisting of the phases Cu6Sn5, Cu3Sn, Cu 41Sn11, and (Cu) were produced. The time required to form a bond with the targeted microstructure, notably that of (Cu), was found to be dominated by the consumption of intermediate phases, as dictated by diffusion, and thus scaled quadratically with initial interlayer thickness. Two types of bonding defects were obtained: one due to surface contamination and the other caused by the consumption of Sn through the formation of the Cu 6Sn5 intermetallic in the solid state during heating. The successful production of samples devoid of such defects was via electron beam deposition of the interlayer material, with sufficient thickness to ensure ample material for the formation of the transient liquid phase following solid state intermetallic formation. The mechanical properties of these bonds were measured and compared with those made with Sn foil. The toughness of the bonds in samples where the Sn interlayer was introduced by electron beam deposition was greater than that of samples that used an interlayer of Sn foil. The difference was attributed to the higher level of porosity and defects in the foil samples. The strengths of the bonds displayed a similar trend and were rationalized in terms of the corresponding differences in toughness and flaw size. Finally, the Ag-In system was investigated as a potentially superior alternative to Cu-Sn. The consumption of intermediate phases in this system occurred in about 1/10 of the time required for the Cu-Sn system, thereby demonstrating that comparable bonds, containing only the corresponding solid solution, could be produced at lower combinations of time and temperature.

Bosco, Nicholas Seth

408

Liquid-Phase Compositions from Vapor-Phase Analyses. II. Adaptation of the Prausnitz Program to UF sub 6 and Some of Its Potential Impurities.  

National Technical Information Service (NTIS)

There is an economic incentive to use vapor-phase samples of UF sub 6 for determining the concentration of impurities in cylinders of UF sub 6 rather than using liquid-phase samples, as has been done in the past. Calculation of liquid-phase concentrations...

H. D. Cochran W. Davis

1985-01-01

409

IR extinction coefficients as a criterion for chemical activation upon adsorption: propene interaction with cationic forms of y zeolite  

Microsoft Academic Search

An attempt to measure integral molar extinction coefficients (IMEC) of C-H and C=C stretching bands of propene specifically adsorbed by Na+, Ca2+ and Mg2+ cations in Y zeolite was carried out via parallel IR spectroscopic and volumetric measurements. Propene was adsorbed at low pressures (< 0.5 mbar) on self-supporting wafers pressed from the zeolite powders. The IMEC of the C=C-stretching

I. R. Subbotina; V. B. Kazansky; F. C. Jentoft; R. Schlögl

2008-01-01

410

Spatial variations in the chlorophyll-specific absorption coefficients of phytoplankton and photosynthetically active pigments in the equatorial Pacific  

Microsoft Academic Search

Chlorophyll-specific absorption coefficients of particles, ap*(lambda), and of phytoplankton, aph*(lambda), were determined using the glass-fiber filter technique along 150°W in the equatorial Pacific (13°S-1°N). A site-specific algorithm for correcting the path length amplification effect was derived from field measurements. Then a decomposition technique using the high-performance liquid chromatography pigment information and taking into account the package effect was used to

Karima Allali; Annick Bricaud; Hervé Claustre

1997-01-01

411

High-yield production of graphene by liquid-phase exfoliation of graphite  

NASA Astrophysics Data System (ADS)

Fully exploiting the properties of graphene will require a method for the mass production of this remarkable material. Two main routes are possible: large-scale growth or large-scale exfoliation. Here, we demonstrate graphene dispersions with concentrations up to ~0.01 mg ml-1, produced by dispersion and exfoliation of graphite in organic solvents such as N-methyl-pyrrolidone. This is possible because the energy required to exfoliate graphene is balanced by the solvent-graphene interaction for solvents whose surface energies match that of graphene. We confirm the presence of individual graphene sheets by Raman spectroscopy, transmission electron microscopy and electron diffraction. Our method results in a monolayer yield of ~1 wt%, which could potentially be improved to 7-12 wt% with further processing. The absence of defects or oxides is confirmed by X-ray photoelectron, infrared and Raman spectroscopies. We are able to produce semi-transparent conducting films and conducting composites. Solution processing of graphene opens up a range of potential large-area applications, from device and sensor fabrication to liquid-phase chemistry.

Hernandez, Yenny; Nicolosi, Valeria; Lotya, Mustafa; Blighe, Fiona M.; Sun, Zhenyu; de, Sukanta; McGovern, I. T.; Holland, Brendan; Byrne, Michele; Gun'ko, Yurii K.; Boland, John J.; Niraj, Peter; Duesberg, Georg; Krishnamurthy, Satheesh; Goodhue, Robbie; Hutchison, John; Scardaci, Vittorio; Ferrari, Andrea C.; Coleman, Jonathan N.

2008-09-01

412

Advanced far infrared blocked impurity band detectors based on germanium liquid phase epitaxy  

SciTech Connect

This research has shown that epilayers with residual impurity concentrations of 5 x 10{sup 13} cm{sup {minus}3} can be grown by producing the purest Pb available in the world. These epilayers have extremely low minority acceptor concentrations, which is ideal for fabrication of IR absorbing layers. The Pb LPE growth of Ge also has the advantageous property of gettering Cu from the epilayer and the substrate. Epilayers have been grown with intentional Sb doping for IR absorption on lightly doped substrates. This research has proven that properly working Ge BIB detectors can be fabricated from the liquid phase as long as pure enough solvents are available. The detectors have responded at proper wavelengths when reversed biased even though the response did not quite reach minimum wavenumbers. Optimization of the Sb doping concentration should further decrease the photoionization energy of these detectors. Ge BIB detectors have been fabricated that respond to 60 cm{sup {minus}1} with low responsivity. Through reduction of the minority residual impurities, detector performance has reached responsivities of 1 A/W. These detectors have exhibited quantum efficiency and NEP values that rival conventional photoconductors and are expected to provide a much more sensitive tool for new scientific discoveries in a number of fields, including solid state studies, astronomy, and cosmology.

Olsen, C.S. [Lawrence Berkeley National Lab., CA (United States). Engineering Div.]|[Univ. of California, Berkeley, CA (United States). Materials Science and Mineral Engineering Dept.

1998-05-01

413

Micropipe healing in SiC wafers by liquid-phase epitaxy in Si Ge melts  

NASA Astrophysics Data System (ADS)

Liquid-phase epitaxy (LPE) of silicon carbide (SiC) was shown to be an effective technique to overgrow micropipe defects (MP) in SiC wafers prepared by the physical vapour transport (PVT) technique. Growth close to thermodynamic equilibrium, e.g. low supersaturation, provides a favourable condition for effective MP healing. Therefore, the aim of this work was to grow epitaxial layers from strongly diluted Si-based solutions. Using the method of horizontal dipping, the dependence of MP elimination efficiency on Si-Ge flux composition and on the crystallographic orientation (on- and off-axis) of the SiC wafer was investigated. High-quality single crystalline SiC layers of a thickness up to 10 ?m were grown with the growth rate of 0.5 ?m/h. On off-oriented wafers, stepped growth morphology was observed independent of the melt composition. Micropipes with the diameter below 5 ?m were closed with an efficiency of about 80%. SEM investigations as well as inspection under reflected/transmitted light did not show any specific distortion of the growth morphology at the micropipe healing place.

Filip, O.; Epelbaum, B.; Bickermann, M.; Winnacker, A.

2004-10-01

414

Computer Simulation Evidence for a Liquid-Liquid Phase Transition in Gallium: Bulk and Nanodroplets  

NASA Astrophysics Data System (ADS)

Over the last decade, there has been an increasing interest in the first-order liquid-liquid phase transition (LLPT) between liquids of the same chemical composition. While LLPT has been speculated to occur in several liquids that exhibit anomalies in their thermodynamic properties, so far in only two cases it has been experimentally verified. This lack of evidence stems from difficult experimental conditions, since in many cases the LLPT is expected to occur in the metastable supercooled regime. Gallium is a very promising substance for the study of LLPT, since it has low melting point (303 K), displays anomalous behavior, and can be kept liquid about 100 K below its melting temperature. In this work, we report on molecular dynamics simulations of liquid Ga that provide theoretical evidence of a LLPT from a high density to a low density liquid in bulk [1] and nanodroplets. Our results indicate a reduction in the temperature and latent heat of the LLPT as the size of the system decreases. [1] D. A. C. Jara, M. F. MIchelon, A. Antonelli, and M. de Koning, Journal of Chemical Physics 130, 221101 (2009).

Antonelli, Alex; Jara, Diego; Michelon, Mateus; de Koning, Maurice

2010-03-01

415

In situ derivatization hollow fiber mediated liquid phase microextraction of alkylphosphonic acids from water.  

PubMed

Alkylphosphonic acids (APAs), particularly the methyl-, ethyl-, isopropyl- and n-propyl-phosphonic acids are important markers of extremely toxic nerve agents. Hence, their detection and identification is of vital importance to verification of chemical weapons convention (CWC). Verification analysis of CWC requires development of fast, reliable, simple and reproducible sample preparation methods of water and soil samples. Present investigation is focused on the optimization of alkylation of APAs in water with subsequent extraction of alkylated acids by hollow fiber liquid phase microextraction (HF-LPME). This simple and sensitive sample preparation of APAs from water offered better recoveries in comparison to conventionally used extraction technique. Under optimized conditions, the APAs were detected at the concentration of 0.5-0.75 microg/mL with S/N ratio > or = 5, whereas the LODs for alkyl APAs (monobasic APAs) were achieved up to 0.1 microg/mL. The developed method was finally tested with water samples supplied in 19th official proficiency test conducted by the OPCW. PMID:17174319

Pardasani, Deepak; Kanaujia, Pankaj K; Gupta, A K; Tak, Vijay; Shrivastava, R K; Dubey, D K

2007-02-01

416

Interplay of the Glass Transition and the Liquid-Liquid Phase Transition in Water  

PubMed Central

Water has multiple glassy states, often called amorphous ices. Low-density (LDA) and high-density (HDA) amorphous ice are separated by a dramatic, first-order like phase transition. It has been argued that the LDA-HDA transformation connects to a first-order liquid-liquid phase transition (LLPT) above the glass transition temperature Tg. Direct experimental evidence of the LLPT is challenging to obtain, since the LLPT occurs at conditions where water rapidly crystallizes. In this work, we explore the implications of a LLPT on the pressure dependence of Tg(P) for LDA and HDA by performing computer simulations of two water models – one with a LLPT, and one without. In the absence of a LLPT, Tg(P) for all glasses nearly coincide. When there is a LLPT, different glasses exhibit dramatically different Tg(P) which are directly linked with the LLPT. Available experimental data for Tg(P) are only consistent with the scenario including a LLPT.

Giovambattista, Nicolas; Loerting, Thomas; Lukanov, Boris R.; Starr, Francis W.

2012-01-01

417

Nanostructure Particle-Reinforced Transient Liquid Phase Diffusion Bonding: a Comparative Study  

NASA Astrophysics Data System (ADS)

Particle-reinforced aluminum-metal matrix composites (Al-MMCs) are used in many engineering applications, because they provide significant advantages when compared to monolithic aluminum alloys. However, there still exists the need to identify a suitable joining process for these materials, which minimizes particulate disruption and retains the strength of the MMC within the joint region. This study presents a comparison between joint qualities achieved when a monolithic interlayer is used vs when a nanoparticle-reinforced composite interlayer is used during transient liquid phase diffusion bonding of Al-6061 alloy containing 15 vol pct of Al2O3 particles. Examination of the joint region using scanning electron microscopy (SEM), wavelength dispersive spectroscopy (WDS), and X-ray diffraction (XRD) showed the formation of eutectic phases such as Al3Ni, Al9FeNi, and Ni3Si within the joint zone. The results indicate that the addition of nanoparticle reinforcements into the interlayer can be used to improve joint strength and minimize particle segregation.

Cooke, Kavian O.; Khan, Tahir I.; Oliver, Gossett D.

2011-08-01

418

Microporous hydrophobic hollow fiber modules for gas-liquid phase separation in microgravity  

NASA Astrophysics Data System (ADS)

Gas-liquid interphase mass transfer operations, such as gas-liquid phase separation, gas absorption into liquid or dissolved gas separation from liquid, gas humidification and drying via liquid contact, and evaporative cooling are readily accomplished on the Earth with settling/spray chambers, packed towers, or bubble columns. This paper reports on gas-water mass transfer tests performed utilizing microporous hydrophobic Hollow Fiber Modules (HFMs) of the type currently employed as blood oxygenators in heart-lung machines. In these HFMs, gases are transferrred to and from water or other hydrophilic liquids through the microporous fiber walls; liquid water does not enter the pores of the highly hydrophobic wall material. The experiments included air-water phase separation, absorption of oxygen and carbon dioxide into water and separation of these dissolved gases from water, air humidification and drying by contact with temperature-controlled water, and controlled evaporation of water into a vacuum. In each of these experiments, a small, light HFM sucessfully performed the mass tranfer function, with no leakage of liquid water through the porous walls of the hollow fibers, even with high pressure across the fiber wall for extended periods of time. These results demonstrate that gas-liquid mass transfer unit operations on hydrophilic liquids, implemented with microporous hydrophobic HFM technology, are ready for use in microgravity fluid processing systems.

Noyes, Gary

419

Grain refinement of transient liquid phase bonding zone using ODS insert foil  

NASA Astrophysics Data System (ADS)

Joint strengthening of oxide dispersion strengthened (ODS) martensitic steel has been attained by a transient liquid phase (TLP) bonding utilizing a newly developed ODS insert foil. The ODS insert foil (Fe-9Cr-2W-0.2Ti-0.35Y2O3-0.5C-3B-2Si) was fabricated using mechanical alloying and a spark plasma sintering method. Compared to conventional TLP bonding with a non-ODS insert foil (Fe-0.5C-3B-2Si), the microstructure of the melted zone consists of finer grains in the joint with the newly developed ODS insert material, and the grain size is almost one third of that in the conventional insert material. This increases the hardness by ?Hv = 100 in the region of the joints. Oxide particles that are coherent to the ferritic matrix in the ODS insert foil could be responsible for the grain refinement, which is explained in terms of enhanced nucleation of consolidation matrix at the oxide particles.

Noto, Hiroyuki; Kasada, Ryuta; Kimura, Akihiko; Ukai, Shigeharu

2013-11-01

420

Synthesis of structurally well-defined and liquid-phase-processable graphene nanoribbons  

NASA Astrophysics Data System (ADS)

The properties of graphene nanoribbons (GNRs) make them good candidates for next-generation electronic materials. Whereas ‘top-down’ methods, such as the lithographical patterning of graphene and the unzipping of carbon nanotubes, give mixtures of different GNRs, structurally well-defined GNRs can be made using a ‘bottom-up’ organic synthesis approach through solution-mediated or surface-assisted cyclodehydrogenation reactions. Specifically, non-planar polyphenylene precursors were first ‘built up’ from small molecules, and then ‘graphitized’ and ‘planarized’ to yield GNRs. However, fabrication of processable and longitudinally well-extended GNRs has remained a major challenge. Here we report a bottom-up solution synthesis of long (>200 nm) liquid-phase-processable GNRs with a well-defined structure and a large optical bandgap of 1.88 eV. Self-assembled monolayers of GNRs can be observed by scanning probe microscopy, and non-contact time-resolved terahertz conductivity measurements reveal excellent charge-carrier mobility within individual GNRs. Such structurally well-defined GNRs may prove useful for fundamental studies of graphene nanostructures, as well as the development of GNR-based nanoelectronics.

Narita, Akimitsu; Feng, Xinliang; Hernandez, Yenny; Jensen, Søren A.; Bonn, Mischa; Yang, Huafeng; Verzhbitskiy, Ivan A.; Casiraghi, Cinzia; Hansen, Michael Ryan; Koch, Amelie H. R.; Fytas, George; Ivasenko, Oleksandr; Li, Bing; Mali, Kunal S.; Balandina, Tatyana; Mahesh, Sankarapillai; de Feyter, Steven; Müllen, Klaus

2014-02-01

421

Growth of SiO 2 on InP substrate by liquid phase deposition  

NASA Astrophysics Data System (ADS)

We have grown silicon dioxide (SiO 2) on indium phosphorous (InP) substrate by liquid phase deposition (LPD) method. With inserting InP wafer in the treatment solution composed of SiO 2 saturated hydrofluorosilicic acid (H 2SiF 6), 0.1 M boric acid (H 3BO 3) and 1.74 M diluted hydrochloric acid (HCl), the maximum deposition rate and refractive index for the as-grown LPD-SiO 2 film were about 187.5 Å/h and 1.495 under the constant growth temperature of 40 °C. The secondary ion mass spectroscope (SIMS) and energy dispersive X-ray (EDX) confirmed that the elements of silicon, oxygen, and chloride were found in the as-grown LPD-SiO 2 film. On the other hand, the effects of treatment solution incorporated with the hydrogen peroxide (H 2O 2) that can regulate the concentration of OH - ion were also shown in this article. The experimental results represented that the deposition rate decreases with increasing the concentration of hydrogen peroxide due to the reduced concentration of SiO 2 saturated H 2SiF 6 in treatment solution.

Lei, Po Hsun; Yang, Chyi Da

2010-04-01

422

Preparation and Optical Properties of Spherical Inverse Opals by Liquid Phase Deposition Using Spherical Colloidal Crystals  

NASA Astrophysics Data System (ADS)

Titanium dioxide (TiO2) inverse opals in spherical shape were prepared by liquid phase deposition (LPD) using spherical colloidal crystals as templates. Spherical colloidal crystals were produced by ink-jet drying technique. Aqueous emulsion droplets that contain polystyrene latex particles were ejected into air and dried. Closely packed colloidal crystals with spherical shape were obtained. The obtained spherical colloidal crystals were used as templates for the LPD. The templates were dispersed in the deposition solution of the LPD, i.e. a mixed solution of ammonium hexafluorotitanate and boric acid and reacted for 4 h at 30 °C. After the LPD process, the interstitial spaces of the spherical colloidal crystals were completely filled with titanium oxide. Subsequent heat treatment resulted in removal of templates and spherical titanium dioxide inverse opals. The spherical shape of the template was retained. SEM observations indicated that the periodic ordered voids were surrounded by titanium dioxide. The optical reflectance spectra indicated that the optical properties of the spherical titanium dioxide inverse opals were due to Bragg diffractions from the ordered structure. Filling in the voids of the inverse opals with different solvents caused remarkable changes in the reflectance peak.

Aoi, Y.; Tominaga, T.

2013-03-01

423

Microstructural evolution during transient liquid phase bonding of Inconel 738LC using AMS 4777 filler alloy  

SciTech Connect

IN-738LC nickel-based superalloy was joined by transient liquid phase diffusion bonding using AMS 4777 filler alloy. The bonding process was carried out at 1050 Degree-Sign C under vacuum atmosphere for various hold times. Microstructures of the joints were studied by optical and scanning electron microscopy. Continuous centerline eutectic phases, characterized as nickel-rich boride, chromium-rich boride and nickel-rich silicide were observed at the bonds with incomplete isothermal solidification. In addition to the centerline eutectic products, precipitation of boron-rich particles was observed in the diffusion affected zone. The results showed that, as the bonding time was increased to 75 min, the width of the eutectic zone was completely removed and the joint was isothermally solidified. Homogenization of isothermally solidified joints at 1120 Degree-Sign C for 300 min resulted in the elimination of intermetallic phases formed at the diffusion affected zone and the formation of significant {gamma} Prime precipitates in the joint region. - Highlights: Black-Right-Pointing-Pointer TLP bonding of IN-738LC superalloy was performed using AMS 4777 filler alloy. Black-Right-Pointing-Pointer Insufficient diffusion time resulted in the formation of eutectic product. Black-Right-Pointing-Pointer Precipitation of B-rich particles was observed within the DAZ. Black-Right-Pointing-Pointer The extent of isothermal solidification increased with increasing holding time. Black-Right-Pointing-Pointer Homogenizing of joints resulted in the dissolution of DAZ intermetallics.

Jalilvand, V., E-mail: jalilvand@aut.ac.ir [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran 15875-4413 (Iran, Islamic Republic of); Omidvar, H. [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran 15875-4413 (Iran, Islamic Republic of)] [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran 15875-4413 (Iran, Islamic Republic of); Shakeri, H.R. [Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4 (Canada)] [Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4 (Canada); Rahimipour, M.R. [Department of Ceramic, Materials and Energy Research Center, Karaj 31787-316 (Iran, Islamic Republic of)] [Department of Ceramic, Materials and Energy Research Center, Karaj 31787-316 (Iran, Islamic Republic of)

2013-01-15

424

Dynamical and structural heterogeneities close to liquid-liquid phase transitions: The case of gallium  

NASA Astrophysics Data System (ADS)

Liquid-liquid phase transitions (LLPT) have been proposed in order to explain the thermodynamic anomalies exhibited by some liquids. Recently, it was found, through molecular dynamics simulations, that liquid elemental gallium, described by a modified embedded-atom model, exhibits a LLPT between a high-density liquid (HDL) and a low-density liquid (LDL), about 60 K below the melting temperature. In this work [1], we studied the dynamics of supercooled liquid gallium close to the LLPT. Our results show a large increase in the plateau of the self-intermediate scattering function (?-relaxation process) and in the non-Gaussian parameter, indicating a pronounced dynamical heterogeneity upon the onset of the LLPT. The dynamical heterogeneity of the LDL is closely correlated to its structural heterogeneity, since the fast diffusing atoms belong to high-density domains of predominantly 9-fold coordinated atoms, whereas the slow diffusing ones are mostly in low-density domains of 8-fold coordinated atoms. The energetics suggests that the reason for the sluggish dynamics of LDL is due to its larger cohesive energy as compared to that of the HDL. [1] S. Cajahuaringa, M. de Koning, and A. Antonelli, J. Chem. Phys. 136, 064513 (2012).

Antonelli, Alex; Cajahuaringa, Samuel; de Koning, Maurice

2013-03-01

425

Hollow-fiber liquid-phase microextraction of amphetamine-type stimulants in human hair samples.  

PubMed

A fast method was optimized and validated in order to quantify amphetamine-type stimulants (amphetamine, AMP; methamphetamine, MAMP; fenproporex, FPX; 3,4-methylenedioxymethamphetamine, MDMA; and 3,4-methylenedioxyamphetamine, MDA) in human hair samples. The method was based in an initial procedure of decontamination of hair samples (50 mg) with dichloromethane, followed by alkaline hydrolysis and extraction of the amphetamines using hollow-fiber liquid-phase micro extraction (HF-LPME) in the three-phase mode. Gas chromatography-mass spectrometry (GC-MS) was used for identification and quantification of the analytes. The LoQs obtained for all amphetamines (around 0.05 ng/mg) were below the cut-off value (0.2 ng/mg) established by the Society of Hair Testing (SoHT). The method showed to be simple and precise. The intra-day and inter-day precisions were within 10.6% and 11.4%, respectively, with the use of only two deuterated internal standards (AMP-d5 and MDMA-d5). By using the weighted least squares linear regression (1/x²), the accuracy of the method was satisfied in the lower concentration levels (accuracy values better than 87%). Hair samples collected from six volunteers who reported regular use of amphetamines were submitted to the developed method. Drug detection was observed in all samples of the volunteers. PMID:22824216

do Nascimento Pantaleão, Lorena; Bismara Paranhos, Beatriz Aparecida Passos; Yonamine, Mauricio

2012-09-01

426

Storing solar energy with liquid phase Diels-Alder reactions. Final report  

SciTech Connect

At the beginning of this project, a preliminary study was completed that indicated the Diels-Alder reaction between maleic anhydride and 2 methyl furan had an energy storage capacity greater than water. During the last two years when this grant was in effect, three additional projects have been completed. First, an improved calorimetric techniques was developed for determination of the energy storage capacity of a reversible liquid phase chemical reaction. This technique confirmed the validity of the earlier results for the maleic anhydride-methyl furan reaction. Second, a technique was developed for characterizing solution nonidealities for mixtures in which reversible chemical reactions occur. It was found that for the maleic anhydride-2 methyl furan reaction, these non idealities could affect equilibrium compositions by nearly 40%. Third, drop calorimetry was used as a screening method to examine sixteen reactions for their potential as energy storage candidates. Of the sixteen examined, three (all involving maleic anhydride and substituted furan) showed an increased energy storage capacity due to reaction while the remaining thirteen showed no increase. In the following report, results of these three studies are summarized. Finally, a general summary of the status of energy storage by chemical reactions is presented.

Poling, B.E.

1983-07-28

427

Transient liquid phase metallic bonding of an Inconel 718SPF superalloy  

SciTech Connect

The applicability of the transient liquid phase (TLP) metallic bonding method for joining fine-grained Inconel 718SPF{reg_sign} superalloy sheets by inserting a Ni-P or a Ni-Cr-P amorphous interlayer has been evaluated. The results show that a joint with uniform chemical composition could be obtained for the Inconel 718SPF superalloy with a Ni-P interlayer at 1,100 C for 8 h. When a Ni-Cr-P interlayer was used under the same metallic bonding conditions, the concentrations of nickel, iron and niobium in the bond region and in the base metal had a difference of more than 2 wt-%. This means that longer bonding time was required to homogenize the chemical compositions of bonds with a Ni-Cr-P interlayer. The joints with a Ni-P interlayer showed higher bond strength than did those with a Ni-Cr-P interlayer. Furthermore, many grain boundary precipitates were found.

Yeh, M.S. [Chung-Hua Polytechnic Inst., Hsin-Chu (Taiwan, Province of China). Dept. of Mechanical Engineering; Chuang, T.H. [National Taiwan Univ., Taipei (Taiwan, Province of China). Inst. of Materials Science and Engineering

1997-12-01

428

Enhanced microbial degradation of humin-bound phenanthrene in a two-liquid-phase system.  

PubMed

Humin, the main component of soil organic matter, greatly influences the nonlinear sorption and desorption hysteresis of polycyclic aromatic hydrocarbons (PAHs) in soil. However, little is known about the bioavailability of PAHs bound to humin. In the present study, a phenanthrene (PHE)-degrading bacterial strain--PHE9--was isolated and identified as the genus Micrococcus. It was used to investigate the degradation of humin-bound PHE and PHE not bound to humin (non-humin PHE) in liquid mineral medium (MM) and in a two-liquid-phase system (TLPs). The results showed that in MM, about 66.84% of humin-bound PHE was degraded after 49 days, whereas almost all the non-humin PHE was degraded after 27 days. Compared to MM, the TLPs showed a much better efficacy in the removal of PHE, especially for humin-bound PHE: more than 97.28% of non-humin PHE was degraded in 11 days and over 85.62% of humin-bound PHE was degraded in 32 days. It could be concluded that most of humin-bound PHE could be degraded in the MM although humin decreased the bioavailability of PHE, whereas the application of TLPs could enhance the biodegradation of humin-bound PHE. PMID:21232850

Zhang, Yinping; Wang, Fang; Wang, Congying; Hong, Qing; Kengara, Fredrick Orori; Wang, Tao; Song, Yang; Jiang, Xin

2011-02-28

429

Synthesis of structurally well-defined and liquid-phase-processable graphene nanoribbons.  

PubMed

The properties of graphene nanoribbons (GNRs) make them good candidates for next-generation electronic materials. Whereas 'top-down' methods, such as the lithographical patterning of graphene and the unzipping of carbon nanotubes, give mixtures of different GNRs, structurally well-defined GNRs can be made using a 'bottom-up' organic synthesis approach through solution-mediated or surface-assisted cyclodehydrogenation reactions. Specifically, non-planar polyphenylene precursors were first 'built up' from small molecules, and then 'graphitized' and 'planarized' to yield GNRs. However, fabrication of processable and longitudinally well-extended GNRs has remained a major challenge. Here we report a bottom-up solution synthesis of long (>200 nm) liquid-phase-processable GNRs with a well-defined structure and a large optical bandgap of 1.88 eV. Self-assembled monolayers of GNRs can be observed by scanning probe microscopy, and non-contact time-resolved terahertz conductivity measurements reveal excellent charge-carrier mobility within individual GNRs. Such structurally well-defined GNRs may prove useful for fundamental studies of graphene nanostructures, as well as the development of GNR-based nanoelectronics. PMID:24451588

Narita, Akimitsu; Feng, Xinliang; Hernandez, Yenny; Jensen, Søren A; Bonn, Mischa; Yang, Huafeng; Verzhbitskiy, Ivan A; Casiraghi, Cinzia; Hansen, Michael Ryan; Koch, Amelie H R; Fytas, George; Ivasenko, Oleksandr; Li, Bing; Mali, Kunal S; Balandina, Tatyana; Mahesh, Sankarapillai; De Feyter, Steven; Müllen, Klaus

2014-02-01

430

Analysis of quinolones by voltage-assisted liquid-phase microextraction combined with LC-MS.  

PubMed

The method of liquid-phase microextraction assisted with voltage was developed and applied on determination of quinolones in water sample in this study. Both of the reproducibility and extraction time were improved with the aid of applying voltage. Four analytes in neutral state such as cinoxacin, oxolinic acid, nalidixic acid, and flumequine were extracted from a sample solution at pH 2.0, through a polypropylene hollow fiber which was immobilized with 2-octanone, and then into a 25 ?L of the acceptor phase of 40 mM borate buffer at pH 10.0 by applying voltage of 100 V. Subsequently, the acceptor solution was directly subjected to analysis by LC-MS. The performance of the method for four quinolones was also evaluated. Linearity was obtained in the range of 1.0-25.0 ng/mL with R(2) > 0.996. Limits of detection were below 0.6 ng/mL, and recoveries of water sample were ranged from 90.8 to 109.6%. PMID:22517642

Wang, Mi-Hung; Wang, Shu-Ping

2012-03-01

431

Vector chiral spin liquid phase in quasi-one-dimensional incommensurate helimagnets  

SciTech Connect

Making use of detailed classical Monte Carlo simulations, we study the critical properties of a two-dimensional planar spin model on a square lattice composed by weakly interacting helimagnetic chains. We find a large temperature window where the vector chirality order parameter, <{kappa}{sub jk}> = , the key quantity in multiferroic systems, takes nonzero value in the absence of long-range order or quasi-long-range order. The phase diagram we obtain for different strengths of the interchain coupling clearly shows that the weakness of the interchain interaction plays an essential role in order to observe the vector chiral spin liquid phase in a temperature range of up to now unattained width ({approx_equal}7%, to be compared with {approx_equal}1% or less previously reported for fully frustrated models, the only well-investigated systems unambiguously displaying spin-chirality decoupling). The relevance of our results for three-dimensional models is also discussed.

Cinti, Fabio [Department of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2J1 (Canada); Department of Physics, University of Florence and CNISM, 50019 Sesto Fiorentino (Finland) (Italy); Cuccoli, Alessandro; Rettori, Angelo [Department of Physics, University of Florence and CNISM, 50019 Sesto Fiorentino (Finland) (Italy)

2011-05-01

432

Fabrication and evaluation of ZnO nanorods by liquid-phase deposition.  

PubMed

The ZnO nanorod growth mechanism during liquid-phase deposition (LPD) has been investigated, with results considered in the context of phase stabilization, LPD chemical processes, and Gibbs free energy and entropy. Zinc oxide (ZnO) possesses unique optical and electronic properties, and obtaining ZnO species with high specific surface area is important in ZnO applications. Highly c-axis-oriented ZnO films are expected to be utilized in future optical and electrical devices. ZnO nanorods were synthesized using an aqueous solution deposition technique on a glass substrate with a free-standing ZnO nanoparticle layer. ZnO nanorod growth was easily controlled on the nanoscale by adjustment of the immersion time (15-210 min). X-ray diffraction, field-emission scanning electron microscopy (FE-SEM), and film thickness measurements were used to characterize the crystalline phase, orientation, morphology, microstructure, and growth mechanism of the ZnO nanorods. FE-SEM images were analyzed by image processing software, which revealed details of the of ZnO nanorod growth mechanism. PMID:21192712

Ichikawa, Takafumi; Shiratori, Seimei

2011-02-01

433

Processing and fabrication of mixed uranium/refractory metal carbide fuels with liquid-phase sintering  

NASA Astrophysics Data System (ADS)

Optimization of powder processing techniques were sought for the fabrication of single-phase, solid-solution mixed uranium/refractory metal carbide nuclear fuels - namely (U, Zr, Nb)C. These advanced, ultra-high temperature nuclear fuels have great potential for improved performance over graphite matrix, dispersed fuels tested in the Rover/NERVA program of the 1960s and early 1970s. Hypostoichiometric fuel samples with carbon-to-metal ratios of 0.98, uranium metal mole fractions of 5% and 10%, and porosities less than 5% were fabricated. These qualities should provide for the longest life and highest performance capability for these fuels. Study and optimization of processing methods were necessary to provide the quality assurance of samples for meaningful testing and assessment of performance for nuclear thermal propulsion applications. The processing parameters and benefits of enhanced sintering by uranium carbide liquid-phase sintering were established for the rapid and effective consolidation and formation of a solid-solution mixed carbide nuclear fuel.

Knight, Travis W.; Anghaie, Samim

2002-11-01

434

ac susceptibility measurement of magnetic markers in suspension for liquid phase immunoassay  

NASA Astrophysics Data System (ADS)

ac susceptibility measurement of magnetic markers in solution was performed for the liquid phase detection of biological targets. First, the properties of the magnetic markers were clarified, such as size distribution, frequency dependence of susceptibility, and field dependence of magnetization. Next, we demonstrated a detection method in which we used large polymer beads to immobilize and prolong the Brownian relaxation time of the bound markers. In this method, we could detect the bound markers by the decrease in the susceptibility that they displayed. Using this method, we detected biotin-conjugated polymer beads with avidin-coated Fe3O4 markers. Changes in susceptibility caused by the binding reaction between them were measured with a magnetoresistive sensor. A strong relationship was observed between the decrease in susceptibility and the number of polymer beads, which indicates that the bound markers were detected correctly without the use of the washing process called bound/free separation. The sensitivity of the system was estimated to be as high as 1.3×10-16 mol/ml in terms of the molecular-number concentration of the markers. The binding process was also discussed from the dependence of the signal on the incubation time.

Enpuku, K.; Tamai, Y.; Mitake, T.; Yoshida, T.; Matsuo, M.

2010-08-01

435

Liquid-phase benzene oxidation to phenol with molecular oxygen catalyzed by Cu-zeolites  

SciTech Connect

The oxidation of benzene to form phenol using cuprous chloride as a catalyst has been reported by Sasaki and his co-workers, who used reaction system oxygen molecules as the oxidant. Takehira and his co-workers have studied benzene oxidation with molecular oxygen catalyzed by Cu(II) salts in the presence of ascorbic acid. Cu ion-exchanged zeolites have been reported to be useful as catalysts for the gas-phase oxidation of some organic materials, and copper ions in zeolites have been indicated to have redox properties according to physicochemical measurements. Armed with this knowledge, the authors have tried the liquid-phase oxidation of benzene with molecular oxygen under atmospheric pressure at room temperature using Cu ion-exchanged zeolite catalysts in the presence of ascorbic acid as a reducing reagent for Cu ions. The catalytic behavior of the Cu zeolites for the benzene oxidation was compared with that of nonanchored cupric and cuprous chloride catalysts. Also, some Cu catalysts impregnated on some amorphous oxide supports, in addition to the zeolites, were tested as catalysts for benzene oxidation with molecular oxygen. 13 refs., 5 figs., 3 tabs.

Ohtani, Tsuyoshi; Nishiyama, Satoru; Tsuruya, Shigeru [Kobe Univ. (Japan)] [and others] [Kobe Univ. (Japan); and others

1995-08-01

436

Fabrication of particle dispersed inert matrix fuel based on liquid phase sintered SiC  

NASA Astrophysics Data System (ADS)

In the present work, liquid phase sintered SiC (LPS-SiC) was proposed as an inert matrix for the particle dispersed inert matrix fuel (IMF). The fuel particles containing plutonium and minor actinides were substituted with pure yttria stabilized zirconia beads. The LPS-SiC matrix was produced from the initial mixtures prepared using submicron sized ?-SiC powder and oxide additives Al 2O 3, Y 2O 3 in the amount of 10 wt.% with the molar ratio 1Y 2O 3/1Al 2O 3. Powder mixtures were sintered using two sintering methods; namely conventional high temperature sintering and novel spark plasma sintering at different temperatures depending on the method applied in order to obtain dense samples. The phase reaction products were identified using X-ray diffraction (XRD) and microstructures were investigated using light microscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) techniques. The influence of powder mixing methods, sintering temperatures, pressures applied and holding time on the density of the obtained pellets was investigated. The samples sintered by slow conventional sintering show lower relative density and more pronounced interaction between the fuel particles and matrix in comparison with those obtained with the fast spark plasma sintering method.

Pavlyuchkov, D.; Baney, R. H.; Tulenko, J. S.; Seifert, H. J.

2011-08-01

437

Phosphorus: First principle simulation of a liquid-liquid phase transition  

NASA Astrophysics Data System (ADS)

We report a Car-Parrinello molecular dynamics study of the liquid-liquid phase transition in phosphorus. We employed a gradient corrected density functional (B-LYP) to describe the electronic structure and performed simulations at constant pressure. Upon increasing pressure we observed, along the 1500 K isotherm, a structural transition converting the molecular P4 liquid into an atomic liquid with a network structure. Our calculations suggest this transition to be first order with a discontinuous density increase accompanied by an insulator into metal transition. The transition pressure is significantly higher than obtained by employing the less accurate local density functional (LDA) [Morishita, Phys. Rev. Lett. 87, 105701 (2001)], which matches the experimental value for the pressure. We argue why the LDA result should be considered fortuitous. The change of the calculated structure factor upon the transition shows the same trend as experimentally observed. Analysis of the structural changes during the phase transition revealed that a chain of linked and opened up (``butterfly'') P4 molecules may serve as a seed triggering the transition from the molecular to the network phase.

Ghiringhelli, Luca M.; Meijer, Evert Jan

2005-05-01

438

Simulating the phosphorus fluid liquid phase transition up to the critical point  

NASA Astrophysics Data System (ADS)

We report a Car-Parrinello molecular dynamics study of the temperature dependence of the fluid-liquid phase transition in phosphorous, involving the transformation of a molecular fluid phase into a network-like phase. We employed density-functional theory (DFT) with a gradient-corrected functional (B-LYP) to describe the electronic structure and interatomic interactions and performed simulations in a constant pressure ensemble. We spanned a temperature interval ranging from 2500 to 3500 K. With increasing temperature, we found that the structural conversion from the molecular P4 fluid into the network liquid occurs at decreasing pressures, consistent with experimental observations. At lower temperatures the transition is characterized by a sudden increase of density in the sample. The magnitude of the density change decreases with increasing temperature and vanishes at 3500 K. In the temperature range 3100-3500 K we found signals of near- and super-criticality. We identified local structural changes that serve as seeds triggering the overall structural transition.

Ghiringhelli, Luca M.; Meijer, Evert Jan

2007-10-01

439

Effect of the reference solution in the measurement of ion activity coefficients using cells with transference at T = 298.15 K  

Microsoft Academic Search

This work reports individual activity coefficients of ions at T=298.15K in aqueous solutions obtained from voltage values of the respective half-cell ion-selective-electrode and a single-junction Ag–AgCl reference electrode, filled with different reference solutions at different concentrations. For potassium and chloride ions in KCl aqueous solutions, reference solutions of KCl, NaCl, or CsCl were used. For sodium and chloride ions in

Estela Lladosa; Alberto Arce; Grazyna Wilczek-Vera; Juan H. Vera

2010-01-01

440

Prediction of infinite dilution activity coefficients for systems including water based on the group contribution model with mixture-type groups  

Microsoft Academic Search

Group contribution models such as ASOG or UNIFAC were known to be inaccurate in the prediction of infinite dilution activity coefficients (??) for most of the systems containing water. To overcome the weakness inherent with the UNIFAC models, Zhang et al. (Fluid Phase Equil. 149 (1998) 27) have recently proposed a group-contribution-based model with mixture-type groups, where the mixture-type group

Suojiang Zhang; Toshihiko Hiaki; Kazuo Kojima

2002-01-01