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1

LIQUID-PHASE MASS TRANSFER COEFFICIENT IN SLURRY BUBBLE COLUMN REACTORS: THEORY AND EXPERIMENTAL DATA IN SIMULATED FERMENTATION MEDIA  

Microsoft Academic Search

Mass transfer in a slurry bubble column reactor was examined. A theoretical correlation for liquid-phase mass transfer coefficient was developed using a combination of Higbie's penetration theory and the Einstein-Li periodic viscous sublayer model. The proposed correlation predicts that the liquid-phase mass transfer coefficient decreases with an increase of the yield stress of slurries. The measurement of mass transfer rates

Y. KAWASE; M. MOO-YOUNG

1990-01-01

2

High-pressure mass-transfer coefficients in the liquid phase of the binary systems carbon dioxide-methyl myristate and carbon dioxide-methyl palmitate  

Microsoft Academic Search

Mass-transfer coefficients in the liquid phase of the binary systems carbon dioxide-methyl myristate and carbon dioxidemethyl palmitate were determined at 40 and 50 °C and at pressures between 70 bar and the critical pressure of the mixture. The coefficients were measured by observing the absorption rate of carbon dioxide into a falling liquid film. Comparison of the experimental results with

C. A. Lockemann; E.-U. Schlünder

1996-01-01

3

Liquid-phase thiophene adsorption on MCM-22 zeolite and activated carbon  

Microsoft Academic Search

The liquid-phase adsorption of thiophene from thiophene\\/iso-octane and toluene-rich thiophene\\/toluene\\/iso-octane solutions has been investigated in batch conditions at room temperature and atmospheric pressure on MCM-22 zeolite and activated carbon. The adsorption of toluene from toluene\\/iso-octane solutions has also been investigated on both the adsorbents. These were characterised by X-ray diffraction, nitrogen physisorption, scanning electron microscopy and adsorption microcalorimetry of ammonia.

C. Delitala; E. Cadoni; D. Delpiano; D. Meloni; S. Melis; I. Ferino

2008-01-01

4

Liquid-phase adsorption of organic compounds by granular activated carbon and activated carbon fibers  

SciTech Connect

Liquid-phase adsorption of organic compounds by granular activated carbon (GAC) and activated carbon fibers (ACFs) is investigated. Acetone, isopropyl alcohol (IPA), phenol, and tetrahydrofuran (THF) were employed as the model compounds for the present study. It is observed from the experimental results that adsorption of organic compounds by GAC and ACF is influenced by the BET (Brunauer-Emmett-Teller) surface area of adsorbent and the molecular weight, polarity, and solubility of the adsorbate. The adsorption characteristics of GAC and ACFs were found to differ rather significantly. In terms of the adsorption capacity of organic compounds, the time to reach equilibrium adsorption, and the time for complete desorption, ACFs have been observed to be considerably better than GAC. For the organic compounds tested here, the GAC adsorptions were shown to be represented well by the Langmuir isotherm while the ACF adsorption could be adequately described by the Langmuir or the Freundlich isotherm. Column adsorption tests indicated that the exhausted ACFs can be effectively regenerated by static in situ thermal desorption at 150 C, but the same regeneration conditions do not do as well for the exhausted GAC.

Lin, S.H.; Hsu, F.M. [Yuan Ze Inst. of Tech., Taoyuan (Taiwan, Province of China). Dept. of Chemical Engineering

1995-06-01

5

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

6

Preparation of activated carbon from date pits: Effect of the activation agent and liquid phase oxidation  

Microsoft Academic Search

Two series of activated carbons have been prepared from date pits; series C, using carbon dioxide as activating agent, and series S, prepared by activation with steam under the same experimental conditions. The obtained samples were oxidized with nitric acid in order to introduce more oxygen surface groups. The surface area and porosity of the parent and oxidized activated carbons

Meriem Belhachemi; Rachel V. R. A. Rios; Fatima Addoun; Joaquín Silvestre-Albero; Antonio Sepúlveda-Escribano; Francisco Rodríguez-Reinoso

2009-01-01

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

Influence of the Reaction Conditions and Catalytic Properties on the Liquid-Phase Hydrodechlorination of Chlorobenzene over Palladium-Supported Catalysts: Activity and Deactivation  

Microsoft Academic Search

The liquid-phase hydrodechlorination of chlorobenzene with molecular hydrogen was studied over palladium-supported catalysts. The reaction takes place at a gradually decreasing rate through progressive poisoning of the active phase by chloride ions. It is found that the correct choice of the metallic precursor (free of chloride ions) is crucial for the optimum performance of the final solid obtained. In addition,

M. A. Aramend??a; V. Boráu; I. M. Garc??a; C. Jiménez; F. Lafont; A. Marinas; J. M. Marinas; F. J. Urbano

1999-01-01

9

On the Structure of Activated Hydrotalcites as Solid Base Catalysts for Liquid-Phase Aldol Condensation  

Microsoft Academic Search

Hydrotalcites (HTs) of different, well-defined platelet sizes were hydrothermally synthesized. Activation via calcination and rehydration resulted in highly active catalysts. Their activities in the self-condensation of acetone at 273 K showed a linear increase with the amount of accessible Brønsted basic sites as determined by CO2 adsorption. The number of accessible sites, based on the CO2\\/Al ratio, was below 5%.

J. C. A. A. Roelofs; D. J. Lensveld; A. J. van Dillen; K. P. de Jong

2001-01-01

10

Influence of surface characteristics on liquid-phase adsorption of phenol by activated carbons prepared from bituminous coal  

SciTech Connect

Liquid-phase adsorption of phenol by activated carbons prepared from a bituminous coal was investigated. The carbon preparation consisted of carbonization of the oxidized or the unoxidized coal followed by activation in CO{sub 2} to various extents of burnoff. It was observed from the experimental results that BET surface area and pore volume are important factors in determining the adsorptive capacity of the activated carbons. The Langmuir model yields a fairly good fit to the adsorption isotherms, indicating a monolayer adsorption of phenol onto these carbons. The amount of phenol adsorbed per unit surface area, corresponding to complete coverage of the adsorptive sites, decreases with the extent of burnoff and with the particle size of the carbon. The decrease can be attributed to the increase in diffusion path. It was found that the adsorptive capacity decreases with the temperature for the carbon prepared from the unoxidized coal, while it increases for the carbons from the oxidized coal. This difference can be attributed to different populations of oxygen functional groups on the carbon surfaces. According to the Langmuir model, the adsorption of phenol on these carbons was found to be an endothermic process.

Tseng, H.; Hsieh, C.T. [National Cheng Kung Univ., Tainan (Taiwan, Province of China). Dept. of Chemical Engineering

1998-09-01

11

Nonhomogeneity effects in adsorption from gas and liquid phases on activated carbons  

SciTech Connect

The process of adsorption of dissociating organic substances from dilute aqueous solutions on various activated carbons is studied. The investigated adsorbents have different pore structure and chemical properties of the surface. The characteristics of activated carbons are determined from nitrogen and benzene isotherms and potentiometric titration data. The properties of pore structure--BET specific surface area, the total pore volume, the external surface area, the micropore volume, and the density of surface charge--are evaluated. The isotherms of benzoic acid adsorption from the aqueous phase are measured for a wide range of solution pH and constant ionic strength by using the static method. The liquid adsorption data are analyzed in terms of the theory of adsorption on heterogeneous solids.

Derylo-Marczewska, A.; Marczewski, A.W. [Maria Curie-Sklodowska Univ., Lublin (Poland). Faculty of Chemistry

1999-05-25

12

In-situ activation of CuO/ZnO/Al.sub.2 O.sub.3 catalysts in the liquid phase  

DOEpatents

The present invention relates to a method of activation of a CuO/ZnO/Al.sub.2 O.sub.3 catalyst slurried in a chemically inert liquid. Successful activation of the catalyst requires the use of a process in which the temperature of the system at any time is not allowed to exceed a certain critical value, which is a function of the specific hydrogen uptake of the catalyst at that same time. This process is especially critical for activating highly concentrated catalyst slurries, typically 25 to 50 wt %. Activation of slurries of CuO/ZnO/Al.sub.2 O.sub.3 catalyst is useful in carrying out the liquid phase methanol or the liquid phase shift reactions.

Brown, Dennis M. (Allentown, PA); Hsiung, Thomas H. (Emmaus, PA); Rao, Pradip (Allentown, PA); Roberts, George W. (Emmaus, PA)

1989-01-01

13

Influence of the reaction conditions and catalytic properties on the liquid-phase hydrodebromination of bromobenzene over palladium supported catalysts: activity and deactivation  

Microsoft Academic Search

The liquid-phase hydrodebromination of bromobenzene with molecular hydrogen over palladium supported catalysts was studied. The reaction was found to be structure-sensitive as regards both the initial activity and the final conversion (deactivation). The influence of the palladium content and the catalytic support effect on the initial activity were negligible in catalysts of similar metal dispersion. The supports tested, viz. SiO2\\/AlPO4,

M. A. Aramend??a; V. Boráu; I. M. Garc??a; C. Jiménez; J. M. Marinas; F. J. Urbano

1999-01-01

14

Determination of triphenylphosphine oxide in active pharmaceutical ingredients by hollow-fiber liquid-phase microextraction followed by reversed-phase liquid chromatography  

Microsoft Academic Search

A versatile procedure has been developed and validated for the determination of triphenylphosphine oxide (TPPO) at low levels in various active pharmaceutical ingredients (APIs). This procedure incorporates the use of the novel hollow-fiber liquid-phase microextraction (LPME) for the measurement of this potential process-related impurity in aqueous solutions of APIs. A small volume (40?L) of 1-octanol contained within a hollow polypropylene

Stephen M. Richoll; Ivelisse Colón

2006-01-01

15

ACTIVITY COEFFICIENTS OF CARBAMOYLMETHYLPHOSPHORYL EXTRACTANTS IN TOLUENE  

Microsoft Academic Search

The activity coefficients of four extractants belonging to the carbamoylmethylphosphoryl class were measured by vapor-phase osmometry. All of the activity coefficients were within 15% of unity for concentrations up to 0.5 M in toluene. As the basicity of the extractant's phosphoryl-group increases, its activity coefficient decreases. Octylphenyl-N,N-diisobutylcarbamoylmethyl-phosphine oxide [O?D(iB)CMPO] in toluene exhibited a marked decrease in activity coefficient upon equilibration

H. Diamond; E. P. Horwitz; P. R. Danesi

1986-01-01

16

Photocatalytic activity of anatase thin films coated cotton fibers prepared via a microwave assisted liquid phase deposition process  

Microsoft Academic Search

Nanocrystalline titanium dioxide thin films in the anatase phase was successfully coated on cotton fibers via a simple microwave (MW) assisted liquid phase deposition (MW-LPD) process with hexafluorotitanate ammonium (NH4)2TiF6 as precursor. Compared with the conventional LPD processes, the MW-LPD technique could provide quickly high yield and crystallinity in a diluted precursor solution at a low temperature. Microwave irradiation penetrated

Zhang Liuxue; Wang Xiulian; Liu Peng; Su Zhixing

2007-01-01

17

Hydrogenation of nitriles on a well-characterized nickel surface: From surface science studies to liquid phase catalytic activity measurements  

SciTech Connect

Nitrile hydrogenation is the most commonly used method for preparing diverse amines. This thesis is aimed at the mechanism and factors affecting the performance of Ni-based catalysts in nitrile hydrogenations. Surface science techniques are used to study bonding of nitriles and amines to a Ni(111) surface and to identify surface intermediates. Liquid-phase hydrogenations of cyclohexene and 1-hexene on a Pt foil were carried out successfully. Finally, knowledge about the surface structure, surface chemical bond, dynamics of surface atoms (diffusion, growth), and reactivity of metal surfaces from solid-gas interface studies, is discussed.

Gardin, D.E.

1993-12-01

18

Two-liquid-phase bioreactors.  

PubMed

The application of two liquid phases that are poorly miscible is a fascinating research topic for biocatalytical conversions because of the promising results. Motives for application include an increase of productivity and achievement of continuous processing, but new limitations arise, e.g., interfacial effects such as biocatalyst accumulation and loss of activity, medium component accumulation, and slow coalescence. Centrifuges, membranes, and immobilization are tools that can overcome part of the problems, but more fundamental knowledge about interfaces and coalescence is still necessary for successful application. For scaleup and further development of processes based on the obtained results, a choice must be made for the configuration of the experimental setup of a bioreactor. Aspects like aeration, shear stress, batch or continuous processing, and immobilization can play an important role. This review article describes these aspects and the proposals that have been made in recent years concerning two-liquid-phase bioreactors. It shows some adaptations to existing bioreactors, such as loop reactors and stirred-tank reactors. PMID:7764006

Van Sonsbeek, H M; Beeftink, H H; Tramper, J

1993-09-01

19

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

20

Investigation of the catalytic activity of niobium phosphates for liquid phase alkylation of anisole with benzyl chloride  

Microsoft Academic Search

In this work crystalline niobium phosphate with different degrees of crystallinity was synthesized by two different methods as catalysts for benzylation of anisole with benzyl chloride. The catalysts were characterized by XRD, N2 physisorption, solid state 31P and 93Nb NMR, structural FTIR and FTIR after adsorption of pyridine. The catalytic activities were measured in the benzylation of anisole with benzyl

Marcus Henrique C. de La Cruz; Ângela S. Rocha; Elizabeth R. Lachter; Aline M. S. Forrester; Michele Castro Reis; Rosane A. S. San Gil; Stefano Caldarelli; Andrea D. Farias; Wilma A. Gonzalez

2010-01-01

21

Liquid-phase mass transfer in high-pressure systems with a supercritical and a liquid phase  

NASA Astrophysics Data System (ADS)

Liquid-phase diffusion coefficients and mass-transfer coefficients were measured in binary two-phase systems at high pressures. Both were determined from the rates of absorption of the gaseous component into the liquid. Diffusion coefficients were measured by observing unsteady-state diffusion into a sell) i infinite liquid phase and fitting transient counterdiffusion mass-flow rates to the visually determined change of the position of the interface between the liquid and the supercritical phase. Mass-transfer coefficients in the liquid phase were determined from the absorption rate of the gaseous component into a falling liquid film of known flow and physical properties. Experiments were performed with the binary systems carbon dioxide-oleic acid, carbon dioxide -methyl myristate, and carbon dioxide-methyl palmitate. Liquid-phase diffusion coefficients rise significantly with concentration as viscosity decreases. Temperature also has a strong effect on diffusivities. Experimental mass-transfer coefficients in nearly saturated liquids agree well with calculations for falling films with known properties, whereas far from equilibrium, Marangoni convection greatly enhances mass-transfer rates. Close to the critical point of the binary system at a given temperature, a sharp decline of the mass-transfer coefficient is observed.

Lockemann, C. A.; Schilünder, E.-U.

1995-05-01

22

Determination of triphenylphosphine oxide in active pharmaceutical ingredients by hollow-fiber liquid-phase microextraction followed by reversed-phase liquid chromatography.  

PubMed

A versatile procedure has been developed and validated for the determination of triphenylphosphine oxide (TPPO) at low levels in various active pharmaceutical ingredients (APIs). This procedure incorporates the use of the novel hollow-fiber liquid-phase microextraction (LPME) for the measurement of this potential process-related impurity in aqueous solutions of APIs. A small volume (40 microL) of 1-octanol contained within a hollow polypropylene fiber is used for the extraction of TPPO from low pH aqueous API solutions. More than a 100-fold increase in the TPPO concentration is obtained without additional evaporation of the extract. Experimental parameters of the extraction procedure were investigated to optimize extraction efficiency and minimize sample matrix interference. Using HPLC/UV as the end analysis technique, the procedure was validated for TPPO in the concentration range of 3-16 microg/L with an API present at 1500 mg/L. The versatility of the method was demonstrated by applying the procedure to the analysis of APIs with different molecular structures. This simple LPME procedure is inexpensive and offers appropriate sensitivity for the intended use while providing several advantages over other analysis methods for pharmaceutical samples. PMID:16814311

Richoll, Stephen M; Colón, Ivelisse

2006-06-30

23

A simple method for preparing highly active palladium catalysts loaded on various carbon supports for liquid-phase oxidation and hydrogenation reactions  

Microsoft Academic Search

Preparation of nanosized palladium (Pd) catalysts supported on various carbon supports using a simple liquid-phase reduction of aqueous Pd complexes with potassium borohydride (KBH4) was investigated. We found that addition of appropriate amounts of sodium hydroxide (NaOH) into aqueous solutions of sodium tetrachloropalladate (Na2PdCl4) followed by reduction with KBH4 produced highly dispersed Pd nanoparticles less than 5nm in diameter on

Takashi Harada; Shigeru Ikeda; Mayu Miyazaki; Takao Sakata; Hirotaro Mori; Michio Matsumura

2007-01-01

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+, 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

25

Liquid phase sintered superconducting cermet  

SciTech Connect

This patent describes a method of making a superconducting cermet having superconducting properties with improved bulk density, low porosity and in situ stabilization. It comprises: forming a structure of a superconducting ceramic material having the formula RM{sub 2}Cu{sub 3}O{sub (6.5 + x)}wherein R is one or more rare earth elements capable of reacting to form a superconducting ceramic, M is one or more alkaline earth metal elements selected from barium and strontium capable of reacting to form a superconducting ceramic, x is greater than 0 and less than 0.5; and a precious metal compound in solid form selected from the class consisting of oxides, sulfides and halides of silver; and liquid phase sintering the mixture at a temperature wherein the precious metal of the precious metal compound is molten and below the melting point of the ceramic material. The liquid phase sintering is carried out for a time less than 36 hours but sufficient to improve the bulk density of the cermet.

Ray, S.P.

1990-01-09

26

Osmotic Coefficients and Mean Activity Coefficients of Uni-univalent Electrolytes in Water at 25°C  

Microsoft Academic Search

This paper gives values for the osmotic coefficients and mean activity coefficients of uni-univalent electrolytes in aqueous solutions at 25 °C. The values are expressed on the molality or weight basis. The data available in the literature have been corrected to the presently accepted scales of atomic weights (1969) and temperature (IPST 1968) and, where necessary, to the absolute electrical

Walter J. Hamer; Yung-Chi Wu

1972-01-01

27

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...

28

Liquid-phase chromatography detector  

DOEpatents

A liquid-phase chromatography detector comprising a flow cell having an inlet tubular conduit for receiving a liquid chromatographic effluent and discharging it as a flowing columnar stream onto a vertically adjustable receiving surface spaced apart from and located vertically below and in close proximity to the discharge end of the tubular conduit; a receiver adapted to receive liquid overflowing from the receiving surface; an exit conduit for continuously removing liquid from the receiver; a light source for focussing fluorescence-producing light pulses on the flowing columnar stream as it passes from the outlet of the conduit to the receiving surface and a fluorescence detector to detect the produced fluorescence; a source of light pulse for producing acoustic waves in the columnar stream as it passes from the conduit outlet to the receiving surface; and a piezoelectric transducer adapted to detect those waves; and a source of bias voltage applied to the inlet tubular conduit and adapted to produce ionization of the liquid flowing through the flow cell so as to produce photocurrents therein and an electrical system to detect and record the photocurrents. This system is useful in separating and detecting individual chemical compounds from mixtures thereof.

Voigtman, Edward G. (Gainesville, FL); Winefordner, James D. (Gainesville, FL); Jurgensen, Arthur R. (Gainesville, FL)

1983-01-01

29

Liquid-phase chromatography detector  

DOEpatents

A liquid-phase chromatography detector comprises a flow cell having an inlet tubular conduit for receiving a liquid chromatographic effluent and discharging it as a flowing columnar stream onto a vertically adjustable receiving surface spaced apart from and located vertically below and in close proximity to the discharge end of the tubular conduit; a receiver adapted to receive liquid overflowing from the receiving surface; an exit conduit for continuously removing liquid from the receiver; a light source for focusing fluorescence-producing light pulses on the flowing columnar stream as it passes from the outlet of the conduit to the receiving surface and a fluorescence detector to detect the produced fluorescence; a source of light pulse for producing acoustic waves in the columnar stream as it passes from the conduit outlet to the receiving surface; and a piezoelectric transducer adapted to detect those waves; and a source of bias voltage applied to the inlet tubular conduit and adapted to produce ionization of the liquid flowing through the flow cell so as to produce photocurrents therein and an electrical system to detect and record the photocurrents. This system is useful in separating and detecting individual chemical compounds from mixtures thereof. 5 figs.

Voigtman, E.G.; Winefordner, J.D.; Jurgensen, A.R.

1983-11-08

30

Activity coefficients of KCl in highly concentrated protein solutions  

Microsoft Academic Search

As a contribution to the understanding of the thermodynamic state of single salts in living systems, the activity coefficients of KCl were determined in concentrated bovine serum albumin (BSA) solutions. The concentration range studied was 0.01 to 0.5 M KCl and zero to 18% wt BSA, thus amply covering physiological conditions. The activity coefficients of the salt were measured using

P. Ocon; C. Acerete; M. D. Reboiras

1987-01-01

31

New equipment and new technique for measuring activity coefficients and Henry's constants at infinite dilution.  

PubMed

New equipment is presented along with various experimental procedures and setups to cover a large range of applications. It represents a considerable improvement in terms of speed, accuracy, and simplicity with respect to classical gas stripping methods known as "dilutor techniques." Furthermore, range of conditions of its use is larger in terms of: temperatures (from 90 to 600 K), corrosive power, and toxicity of handled compounds. Solutes that could adsorb inside sampling valves or on the walls of transfer lines between sampling valve and GC detector are now studied easily; thanks to new design and procedure. Activity coefficients of one solute into one solvent at five temperatures, several repeatability tests included, are obtained in worst cases in less than 3 h. One accurate activity coefficient measurement (toluene in water) at one temperature can be realized in less than 2 min, after loading of the dilutor cell, instead of more than half an hour for unreliable results with previous equipment. It must be pointed out that the slope determination (slope of the logarithm of the exponential decay of solute composition in vapor phase which is in equilibrium with liquid phase) is the highest source of errors (flow rate, temperature, number of moles of solute are known with high accuracy with respect to slopes); they are now determined within few ‰ instead of up to tens of % in the most difficult cases leading to higher accuracies of measured activity coefficients, Henry's constants at infinite dilutions or solubility data. Successful comparisons with literature data and reproducibility tests are presented herein. PMID:21361634

Richon, Dominique

2011-02-01

32

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  

NASA Astrophysics Data System (ADS)

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 coefficient versus pLo were previously made for partitioning data from controlled laboratory studies, resulting in separate trend lines for different ortho-substituted PCB classes. The same plots applied to field data for PCBs and PCNs resulted in separate regression lines with slopes that were statistically different at the 99% confidence level. When Koa is used as the correlation parameter, these differences are resolved showing the ability of the model to reduce variability both within a compound class and between compound classes. The Koa model is also preferred because it uses parameters that can be measured directly ( Koa and fom), unlike the parameters of the Junge-Pankow model which must be estimated.

Falconer, Renee L.; Harner, Tom

33

Liquid-Phase Epitaxy of Advanced Materials  

NASA Astrophysics Data System (ADS)

The performance of many electronic and optoelectronic devices critically depends on the structural quality and homogeneity of the base material, which is often an epitaxial film grown by either vapor-phase epitaxy (VPE) or liquid-phase epitaxy (LPE).

Klemenz Rivenbark, Christine F.

34

Bilayer ice and alternate liquid phases of confined water  

NASA Astrophysics Data System (ADS)

We report results from molecular dynamics simulations of the freezing and melting, at ambient temperature (T=300 K), of a bilayer of liquid water induced by either changing the distance between two confining parallel walls at constant lateral pressure or by lateral compression at constant plate separation. Both transitions are found to be first order. The system studied consisted of 1200 water molecules that were described by the TIP5P model. The in-plane symmetry of the oxygen atoms in the ice bilayer was found to be rhombic with a distorted in-registry arrangement. Above and below the stability region of the ice bilayer we observed two bilayer phases of liquid water that differ in the local ordering at the level of the second shell of nearest neighbors and in the density profile normal to the plane, yielding two liquid phases with different densities. These results suggest the intriguing possibility of a liquid-liquid transition of water, confined to a bilayer, at regions where the ice bilayer is unstable with respect to either of the liquid phases. In addition, we find that under the same conditions, water confined to 3-8 layers remains in the liquid phase (albeit stratification of the transverse density profile) with values of the lateral diffusion coefficient comparable to that of the bulk.

Zangi, Ronen; Mark, Alan E.

2003-07-01

35

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

36

Liquid phase separator with chromatographic column.  

PubMed

Presented liquid phase separator with integrated chromatographic column enables the separation and treatment of a solvent extract layer after the extraction of organic compounds from water in one simple run in a single piece of glassware. The separator has been successfully applied for the determination of hydrocarbon oil index in waters. PMID:15628145

Mikita, Martin; Tölgyessy, Peter; Hrivnák, Peter

2004-12-01

37

Activity coefficients in dilute aqueous solutions from free energy simulations  

Microsoft Academic Search

Aqueous mixtures are encountered in a large number of industrial operations, such as petroleum processing, coal gasification, separations, and waste treatment. The free energy perturbation method with Monte Carlo simulations has been used to calculate relative solvation free energies and ratios of activity coefficients of organic solutes at infinite-dilution in water at 25 C. System studied include hydrocarbons, chlorinated hydrocarbons,

Themis Lazaridis; Michael E. Paulaitis

1993-01-01

38

Activity coefficients of chlorophenols in water at infinite dilution  

SciTech Connect

The total pressure of aqueous solutions of chlorophenols was determined by a ebulliometric total pressure method for the aqueous solutions of phenol, 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, and 2,4-dichlorophenol in the temperature range from 40 to 90 C. The activity coefficients at infinite dilution and the Henry constants were derived.

Tabai, S.; Rogalski, M. [Univ. de Metz (France). Lab. de Thermodynamique et d`Analyse Chimique; Solimando, R. [INPL-ENSIC, Nancy (France). Lab. de Thermodynamique Chimique Appliquee; Malanowski, S.K. [Inst. Chemii Fizycznej PAN, Warszawa (Poland)

1997-11-01

39

Liquid-phase oxidation of propylene to propylene glycol acetates over Pd\\/C and Pt?Pd\\/C: Effect of platinum on catalyst activity and metal dispersity  

Microsoft Academic Search

Kinetics of oxidation of propylene to propylene glycol and its acetates in acetic acid solutions of lithium nitrate over Pd\\/C and Pd?Pt\\/C catalysts has been studied. Catalysts were investigated using X-ray phase analysis and electron microscopy. Platinum introduction into catalyst increases the metal dispersity and the catalyst stability but produces no effect on the nature of surface sites active in

A. V. Karandin; E. V. Gusevskaya; V. A. Likholobov; E. M. Moroz; V. I. Zaikovskii

1992-01-01

40

Prediction of 1-octanol–water partition coefficient and infinite dilution activity coefficient in water from the PR + COSMOSAC model  

Microsoft Academic Search

The Peng–Robinson equation of state (PR EOS) is used for the prediction of 1-octanol–water partition coefficients (KOW) and infinite dilution activity coefficients (??). Unlike the conventional approach where the EOS parameters must be determined from the critical properties and acentric factor of each chemical species in addition to using some mixing rule to account for composition dependence, these parameters are

Chieh-Ming Hsieh; Shiang-Tai Lin

2009-01-01

41

Predicting liquid-phase thermodynamic properties using COSMO-SAC  

NASA Astrophysics Data System (ADS)

Predicting thermodynamic properties of liquids remains a significant challenge in both academia and industry. This is because molecules in the liquid phase are relatively close together but are not arranged in an ordered structure. The COSMO-SAC model uses quantum and statistical mechanics to predict the thermodynamic properties of liquids. In this thesis, a variety of efforts have been made to improve the accuracy of this model. The most successful of these involves the inclusion of dispersion interactions in mixture calculations, which reduces the average prediction error for activity coefficients by over 30%. It has also been demonstrated that the misfit energy—the traditional interaction energy used in all known COSMO-based models—is limited in its ability to model intermolecular interactions. A variety of attempts to improve the electrostatics of the model have been made, but these have had little effect on the overall accuracy. These include use of an expanded hydrogen bonding description, use of an alternate molecular surface construction method, and incorporation of three-dimensional considerations. These results, coupled with the observed improvement obtained from including dispersion interactions, suggest that the greatest weakness in the model is the handling of electrodynamics (how molecules polarize one another), and that future efforts to improve the model should target this area. In addition, the model has been parameterized for the ADF density functional software package, thus making it available to a wider audience. Results are approximately equivalent to those obtained with DMol3, the only package for which a published parameterization was previously available. Of significance, the ADF implementation allows one of the adjustable model parameters to be eliminated. Also, a correlation was found between experimental liquid volumes and the quantum-based molecular volumes employed in COSMO-SAC. This eliminates the need to provide experimental volumes to the model. Finally, a Windows-based graphical user interface for COSMO-SAC has been developed. This expands the availability of the model to anyone with only a general familiarity with thermodynamics. Without this, use is restricted to those with an in-depth knowledge of quantum mechanics, statistical mechanics and computer programming.

Burnett, Russell I.

42

Activity and osmotic coefficients of aqueous sulfuric acid at 298.15 K  

Microsoft Academic Search

A critical evaluation of the mean activity coefficient, ?±, and osmotic coefficient, ?, of aqueous sulfuric acid at 298.15 K is presented for the molality range of 0 to 28 mol?kg?1. Osmotic coefficients were calculated from direct vapor pressure measurements, from isopietic measurements or from freezing point depression measurements. Activity coefficients were calculated from electromotive force measurements of galvanic cells.

Bert R. Staples

1981-01-01

43

Reaction equilibria in the synthesis of 2-methoxy-2-methylbutane and 2-ethoxy-2-methylbutane in the liquid phase  

SciTech Connect

Tertiary ethers are used as octane-enhancing components in gasoline. Equilibrium constants for the liquid-phase synthesis of 2-methoxy-2-methylbutane (TAME) and 2-ethoxy-20methylbutane (TAEE) were measured in the temperature range 323-363 K. The equilibria were studied using the alcohol/alkene mixture in various mole ratios and the respective ether as a reagent in a batch reactor. A commercial cation exchange resin (Amberlyst 16) was used as the catalyst. The system was strongly nonideal, and the UNIQUAC estimation method was used in the calculation of the liquid-phase activity coefficients. The experimental equilibrium constants are given as a function of temperature. At 333 K the equilibrium constants K[sub a] for the synthesis of TAME were 39.6 [+-] 2.5 from methanol and 2-methyl-1-butene (2M1B) and 4.1 [+-] 0.3 from 2-methyl-2-butene (2M2B). The equilibrium constants for the synthesis of TAEE were 17.4 [+-] 1.1 from ethanol and 2M1B and 1.7 [+-] 0.1 from 2M2B. The experimental [Delta][sub r]H values for the liquid-phase synthesis of TAME were [minus]33.6[+-]5.1 kJ/mol (2M1B) and [minus]26.8 [+-] 2.3 kJ/mol (2M2B), and those for the synthesis of TAEE were [minus]35.2 [+-] 5.8 kJ/mol (2M1B) and [minus]27.3 [+-] 6.7 kJ/mol (2M2B). The results were compared with the literature values.

Rihko, L.K.; Linnekoski, J.A.; Krause, A.O.I. (Helsinki Univ. of Technology, Espoo (Finland). Dept. of Chemical Engineering)

1994-10-01

44

Determination of activity coefficients of neutral species in supercritical H 2O solutions  

Microsoft Academic Search

Based on a standard state of unit activity of the solute in a hypothetical one molal solution where activity coefficients are taken as unity at infinite dilution at all pressures and temperatures, the activity coefficients of neutral species generally increase with increasing ionic strength at 25°C. However, activity coefficients of polar species begin to decrease with increasing ionic strength as

John V. Walther

1997-01-01

45

Shape distortion in liquid-phase-sintered tungsten heavy alloys  

Microsoft Academic Search

Shape retention during liquid phase sintering is a major concern at high liquid contents, or large density differences between\\u000a the solid and the liquid phases. This study demonstrates the role of microstructural parameters in controlling the bulk dimensional\\u000a changes that occur during liquid phase sintering of tungsten heavy alloys (WHAs). Tungsten-nickel-copper alloys containing\\u000a 80 wt pct tungsten, the balance containing

Anish Upadhyaya; Randall M. German

1998-01-01

46

Theoretical Mean Activity Coefficients of Strong Electrolytes in Aqueous from 0 to 100C.  

National Technical Information Service (NTIS)

In determining the activity coefficients of electrolytes in aqueous solutions from the freezing point to the boiling point of the solvent, various equations have been used in the treatment of the data. This paper gives values for activity coefficients of ...

W. J. Hamer

1968-01-01

47

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

SciTech Connect

The Liquid Phase Methanol (LPMEOHTM) 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). Air Products and Chemicals, Inc. (Air Products) and Eastman Chemical Company (Eastman) formed the Partnership to execute the Demonstration Project. The LPMEOIYM Process Demonstration Unit was built at a site located at the Eastman complex in Kingsport. During this quarter, comments from the DOE on the Topical Report "Economic Analysis - LPMEOHTM Process as an Add-on to IGCC for Coproduction" were received. A recommendation to continue with design verification testing for the coproduction of dimethyl ether (DIME) and methanol was made. DME design verification testing studies show the liquid phase DME (LPDME) process will have a significant economic advantage for the coproduction of DME for local markets. An LPDME catalyst system with reasonable long-term activity and stability is being developed. A recommendation document summarizing catalyst targets, experimental results, and the corresponding economics for a commercially successful LPDME catalyst was issued on 30 June 1997. The off-site, product-use test plan was updated in June of 1997. During this quarter, Acurex Environmental Corporation and Air Products screened proposals for this task by the likelihood of the projects to proceed and the timing for the initial methanol requirement. Eight sites from the list have met these criteria. The formal submission of the eight projects for review and concurrence by the DOE will be made during the next reporting period. The site paving and final painting were completed in May of 1997. Start-up activities were completed during the reporting period, and the initial methanol production from the demonstration unit occurred on 02 April 1997. The first extended stable operation at the nameplate capacity of 80,000 gallons per day (260 tons per day) took place on 06 April 1997. Pressure drop and resistance coefficient across the gas sparger at the bottom of the reactor increased over this initial operating period. The demonstration unit was shut down from 08 May -17 June 1997 as part of a scheduled complex outage for the Kingsport site. During this outage, the gas sparger was removed, cleaned, and reinstalled. After completion of other maintenance activities, the demonstration unit was restarted, and maintained stable operation through the remainder of the reporting period. Again, the gas sparger showed an increase in pressure drop and resistance since the restart, although not as rapidly as during the April-May operation. Fresh oil was introduced online for the first time to a new flush connection on the gas inlet line to the reactov the flush lowered the pressure drop by 1 psi. However, the effects were temporary, and the sparger resistance coefficient continued to increase. Additional flushing with both fresh oil and entrained slurry recovered in the cyclone and secondary oil knock-out drum will be attempted in order to stabilize the sparger resistance coefficient.

None

1997-06-30

48

Activity Coefficients of Complex Molecules by Molecular Simulation and Gibbs-Duhem Integration  

Microsoft Academic Search

Activity coefficients of solvents and solutes in different aqueous solutions of alcohols and polymers are determined by molecular dynamic simulations. These data are often not accessible by simulation due to unacceptably high computational demands. Therefore, we applied a combination of two methods: water activity coefficients were determined directly via Overlapping Distribution Method, while counter-component activity coefficients were calculated indirectly by

Sascha Hempel; Jan Fischer; Dietmar Paschek; Gabriele Sadowski

2012-01-01

49

LIQUID PHASE DISPERSION IN A PACKED COLUMN WITH COUNTERCURRENT TWO-PHASE FLOW  

Microsoft Academic Search

The axial dispersion in the liquid phase through a packed column was studied with air-water flowing counter-currently in a 10.16?cm inside diameter column packed with Percelain Raschig rings. The dispersion coefficient or Peclet number and mean residence time were calculated by comparing the moments of the responses measured at two points along the column. Effects of gas flow rate (0-0.37

DAE KI CHOE; WON KOOK LEE

1985-01-01

50

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

51

Polyphenyl oxide diamines as inhibitors of liquid-phase oxidation of hydrocarbons  

SciTech Connect

The antiradical activity of certain polyphenyl oxide diamines in the liquid-phase oxidation of ethyl- and isopropylbenzene was studied. The kinetic parameters of the antiradical activity were determined by chemiluminescent and gasometric methods. The data obtained indicated that polyphenyl oxide diamines, used as monomers for polycondensation, may serve as oxidation inhibitors.

Nikolaevskii, A.N.; Kucherenko, V.N.; Enal'ev, V.D.; Kopeikin, V.V.

1987-04-01

52

Liquid-phase sorption-enhanced reaction process  

Microsoft Academic Search

A process for carrying out simultaneous liquid-phase reaction and separation of desired products is described. It used a fixed packed column of an admixture of a catalyst and an adsorbent that selectively removes a reaction byproduct form the reaction zone. The adsorbent is periodically regenerated using the concepts of liquid-phase concentration swing adsorption. The integrated process allows production of multiple

S. Sircar; M. B. Rao

1999-01-01

53

Operational data on the liquid phase tar chamber at Leuna  

Microsoft Academic Search

This file is a series of operational records and diagrams of the liquid phase tar chamber at Leuna. According to Haehnel (in a brief general section) in the chamber a brown coal low temperature carbonization tar was distilled with a small amount of oil. Lighter fractions were led off and the residue was cycled to the liquid phase hydrogenation. When

2008-01-01

54

Ultrasonic atomization: effect of liquid phase properties.  

PubMed

Experiments have been conducted to understand the mechanism by which the ultrasonic vibration at the gas liquid interface causes the atomization of liquid. For this purpose, aqueous solutions having different viscosities and liquids showing Newtonian (aqueous solution of glycerin) and non-Newtonian behavior (aqueous solution of sodium salt of carboxy methyl cellulose) were employed. It has been found that the average droplet size produced by the pseudo-plastic liquid is less than that produced by the viscous Newtonian liquid having viscosity equal to zero-shear rate viscosity of the shear thinning liquid. The droplet size was found to increase initially with an increase in the viscosity up to a certain threshold viscosity after which the droplet size was found to decrease again. Also droplet size distribution is found to be more compact (uniform sizes) with an increasing viscosity of the atomizing liquid. The presence of the cavitation and its effect on the atomization has been semi quantitatively confirmed using energy balance and by the measurement of the droplet ejection velocities and validated on the basis of the decomposition of the aqueous KI solution. A correlation has been proposed for the prediction of droplet size for aqueous Newtonian fluids and fluids showing non-Newtonian behavior based on the dimensionless numbers incorporating the operating parameters of the ultrasonic atomizer and the liquid phase physico-chemical properties. PMID:16321416

Avvaru, Balasubrahmanyam; Patil, Mohan N; Gogate, Parag R; Pandit, Aniruddha B

2005-11-07

55

Activity Coefficient Derivatives of Ternary Systems Based on Scatchard's Neutral Electrolyte Description.  

National Technical Information Service (NTIS)

Activity coefficient derivatives with respect to molality are presented for the Scatchard Neutral Electrolyte description of a ternary common-ion electrolyte system. These quantities are needed for the calculation of 'diffusion Onsager coefficients' and i...

D. G. Miller

2007-01-01

56

NMR study of hydration of liquid phase during lipase catalysed esterification in non aqueuous media  

Microsoft Academic Search

In this paper, NMR spectroscopy is used to monitor water activity of the liquid phase during a lipase catalysed esterification reaction for different initial water acitivity of the substrates. This method allows to study the partition of water between the enzyme and the organic phase.

C. Sarazin; C. Roblot; B. Decagny; F. Ergan; J. N. Barbotin; J. P. Séguin

1998-01-01

57

Preparation of recoverable Ru catalysts for liquid-phase oxidation and hydrogenation reactions  

Microsoft Academic Search

We here report the synthesis, characterization and catalytic performance of new supported Ru(III) and Ru(0) catalysts. In contrast to most supported catalysts, these new developed catalysts for oxidation and hydrogenation reactions were prepared using nearly the same synthetic strategy, and are easily recovered by magnetic separation from liquid phase reactions. The catalysts were found to be active in both forms,

Marcos J. Jacinto; Osvaldo H. C. F. Santos; Renato F. Jardim; Richard Landers; Liane M. Rossi

2009-01-01

58

Solubilities and liquid phase nonidealities in coal liquids: Final report, July 30, 1984-July 30, 1987  

SciTech Connect

The research effort was a three year study of the solubilities of polynuclear aromatic hydrocarbons (PAH's) in organic solvents and the vapor-liquid equilibria of some of these same systems. Solubilities of 102 systems were determined as functions of temperature from ambient temperature to the melting point of the solute. The systems are listed and results are presented. Solubility data were analyzed using four solution models (Regular Solution theory, Extended Regular Solution theory, Wilson's Equation, and UNIQUAC) and binary interaction parameters have been obtained for the liquid phase. Also included are analyses of 35 more systems that have been previously published, for the purpose of composition of the predicted activity coefficients. Vapor pressures were determined for five solvents versus temperature. Also determined were the vapor-liquid equilibria for a test system and for six new systems at three temperatures each. New systems are (tetralin-decalin, tetralin-biphenyl, decalin- biphenyl, tetralin-fluorene, tetralin-fluorene, tetralin- dibenzothiophene, and tetralin-dibenzofuran. Results have been analyzed using four common solution models (Wilson's, UNIQUAC, NRTL, and Van Laar) and the optimum binary parameters determined. We have compared the parameters (for Wilson's and UNIQUAC) for the two methods and discussed the pros and cons of each method as a source for these parameters. Some initial steps have been made towards utilizing statistical mechanical methods for these types of systems. 46 refs., 26 figs., 57 tabs.

McLaughlin, E.; Coon, J.E.

1988-01-01

59

Measurements of Peltier cooling at a Ga-GaAs interface using a liquid-phase epitaxy system  

Microsoft Academic Search

The Peltier coefficient of n-type GaAs was measured by passing an electrical current through the GaAs-Ga solid-liquid interface in a vertical liquid-phase epitaxy (LPE) system. Application of a steady-state heat-transfer analysis yielded values for the Peltier coefficient of 0.141 to 0.203 V in the 530-830 °C temperature range. From the study of measurements of Peltier cooling as a function of

E. K. Stefanakos; A. Abul-Fadl; M. D. Workman

1975-01-01

60

Transient liquid phase bonding of intermetallics  

NASA Astrophysics Data System (ADS)

The present work was undertaken to examine the applicability of transient liquid phase bonding to structural intermetallics. This research was based on an investigation of the mechanisms governing microstructural development in the joint and adjacent substrates during the joining process. The bonding systems investigated included polycrystalline NiAl/Cu/Ni, polycrystalline NiAl/Cu/superalloys (Martin-Marietta (MM)-247, Inconel (IN) 718 and Nimonic 90), single-crystal NiAl (with 1.5 at % Hf) joined to MM-247 using different filler metals (Cu foil, powder filler metal and electro-plated thin Cu film), and martensitic NiAl joined with martensitic NiTi using Cu foil and specially designed powder filler metals. In polycrystalline NiAl/Cu/Ni bonds, the mechanism of isothermal solidification is considered. Changes in the microstructure of the bond centerline due to element redistribution are discussed. The precipitation of both L1sb2 type gammasp' and B2 type beta phase at the joint centerline is investigated. The formation of martensitic L1sb0 type NiAl is also examined. The mechanical properties of the joints are investigated using shear strength and microhardness tests. In TLP bonding of polycrystalline NiAl with MM-247, both the epitaxial growth of the beta phase NiAl into the joint and the formation of non-epitaxial beta-phase layers are considered. The formation of second-phases, including the gammasp' phase, carbides, and sigma-phase intermetallics is also examined. Bond-line and adjacent substrate microstructures for the NiAl/Cu/MM-247 bonds are correlated with joint mechanical properties determined by room temperature shear testing. Single-crystal NiAl (1.5 at % Hf)/Cu/MM-247 joints are examined and compared with polycrystalline NiAl/Cu/MM247 joints. The effect of Hf on the microstructure of joints is investigated. The influence of different filler metals (i.e., wide-gap powder filler metal and electro-plated thin film filler metal) on the joining process is also considered. In TLP bonding of martensitic NiAl with martensitic NiTi, the formation Ti depletion region was observed while using Cu foil as the filler metal. Alternative filler metals were successfully used to solve this problem. According to the experimental results, standard TLP bonding models cannot be applied to the bonding systems in this research. The influence of second phase formation on TLP models is discussed.

Guan, Yimin

61

Oscillation chemiluminescence in liquid phase oxidation of organic compounds  

Microsoft Academic Search

It is for the first time that distinct chemiluminescence oscillations have been observed in the liquid phase oxidation for the system: oxidative substrate — thermal initiator — photosensitizer — O2. Oscillations and their parameters are dependent on the experimental conditions.

I. R. Akhunov; V. D. Komissarov

1986-01-01

62

Oxidation Protection of Uranium Nitride Fuel using Liquid Phase Sintering  

Microsoft Academic Search

Two methods are proposed to increase the oxidation resistance of uranium nitride (UN) nuclear fuel. These paths are: (1) Addition of USiâ (e.g. U3Si2) to UN nitride powder, followed by liquid phase sintering, and (2) 'alloying' UN nitride with various compounds (followed by densification via Spark Plasma Sintering or Liquid Phase Sintering) that will greatly increase oxidation resistance. The advantages

Paul A. Lessing

2012-01-01

63

Measurement of gas/water uptake coefficients for trace gases active in the marine environment  

SciTech Connect

Ocean produced reduced sulfur compounds including dimethylsulfide (DMS), hydrogen sulfide (H{sub 2}S), carbon disulfide (CS{sub 2}), methyl mercaptan (CH{sub 3}CH) and carbonyl sulfide (OCS) deliver a sulfur burden to the atmosphere which is roughly equal to sulfur oxides produced by fossil fuel combustion. These species and their oxidation products dimethyl sulfoxide (DMSO), dimethyl sulfone (DMSO{sub 2}) and methane sulfonic acid (MSA) dominate aerosol and CCN production in clean marine air. Furthermore, oxidation of reduced sulfur species will be strongly influenced by NO{sub x}/O{sub 3} chemistry in marine atmospheres. The multiphase chemical processes for these species must be understood in order to study the evolving role of combustion produced sulfur oxides over the oceans. We have measured the chemical and physical parameters affecting the uptake of reduced sulfur compounds, their oxidation products, ozone, and nitrogen oxides by the ocean's surface, and marine clouds, fogs, and aerosols. These parameters include: gas/surface mass accommodation coefficients; physical and chemically modified (effective) Henry's law constants; and surface and liquid phase reaction constants. These parameters are critical to understanding both the interaction of gaseous trace species with cloud and fog droplets and the deposition of trace gaseous species to dew covered, fresh water and marine surfaces.

Davidovits, P. (Boston Coll., Chestnut Hill, MA (United States). Dept. of Chemistry); Worsnop, D.W.; Zahniser, M.S.; Kolb, C.E. (Aerodyne Research, Inc., Billerica, MA (United States). Center for Chemical and Environmental Physics)

1992-02-01

64

Correlation of infinite dilution activity coefficient of solute in ionic liquid using UNIFAC model  

Microsoft Academic Search

Infinite dilution activity coefficient is an important thermodynamic property, which is widely used in evaluating the intermolecular interaction and screening potential solvents for the separation of a fluid mixture by extraction, distillation or selective absorption. In this paper, UNIFAC model and a new group segmentation method are used to correlate infinite dilution activity coefficients based on the experimental data. Among

Junfeng Wang; Wei Sun; Chunxi Li; Zihao Wang

2008-01-01

65

Application of several activity coefficient models to water-organic-electrolyte aerosols of atmospheric interest  

Microsoft Academic Search

In this work, existing and modified activity coefficient models are examined in order to assess their capabilities to describe the properties of aqueous solution droplets relevant in the atmosphere. Five different water-organic-electrolyte activity coefficient models were first selected from the literature. Only one of these models included organics and electrolytes which are common in atmospheric aerosol particles. In the other

T. Raatikainen; A. Laaksonen

2005-01-01

66

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

Microsoft Academic Search

Abstract. 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

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

2008-01-01

67

Thermal properties and thermal shock resistance of liquid phase sintered ZrC–Mo cermets  

Microsoft Academic Search

The linear thermal expansion coefficient (CTE), heat capacity, and thermal conductivity, were investigated as a function of temperature for hot pressed ZrC and liquid phase sintered ZrC–Mo cermets. The ZrC and the ZrC–Mo cermets had the same CTE at 50°C (?5.1–5.5ppm°C?1), but the CTE of ZrC increased to ?12.2ppm°C?1 at 1000°C compared to ?7.2–8.5ppm°C?1 for the ZrC–Mo cermets. Heat capacity

Sean E. Landwehr; Gregory E. Hilmas; William G. Fahrenholtz; Inna G. Talmy; Hsin Wang

2009-01-01

68

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

2012-09-24

69

Gold-indium Transient Liquid Phase (TLP) wafer bonding for MEMS vacuum packaging  

Microsoft Academic Search

This paper reports the first wafer-level vacuum packages created with gold-indium transient liquid phase (TLP) wafer bonding. The packages were bonded at 200degC for 1 hour under a vacuum environment in a commercially available wafer bonder. After bonding, the integrated getters were activated for 1 hour resulting in internal pressures as low as 200 mTorr. The pressures have been stable

Warren C. Welch; Khalil Najafi

2008-01-01

70

Liquid-phase diacetoxylation of 1,3-butadiene with Pd\\/Te\\/C catalyst  

Microsoft Academic Search

Of various catalysts tested, a catalyst containing an 8:1 ratio of palladium\\/tellurium (0.0003 g atom Pd\\/g catalyst) on a charcoal support was most active in the liquid-phase conversion (at 90°C) of butadiene in acetic acid to diacetoxybutene, an intermediate in the manufacture of 1,4-butanediol, which in turn is used to make polymers, tetrahydrofuran, and pyrollidone. The product distribution was 75Vertical

K. Takehira; H. Mimoun; I. Seree De Roch

1979-01-01

71

Equilibrium constants for methyl tert-butyl ether and ethyl tert-butyl ether liquid-phase syntheses using C[sub 4] olefinic cut  

SciTech Connect

Equilibrium constants for the liquid-phase syntheses of methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) were determined experimentally in the temperature range 313--353 K and at 1.6 MPa, using as source of 2-methylpropene (isobutylene) a C[sub 4] olefinic cut proceeding from a steam cracking unit. To reach etherification equilibrium, the macroporous sulfonic acid resin K-2631 (Bayer) was used as the catalyst. The thermodynamic equilibrium constants and the enthalpy, free energy, and entropy changes of reactions were given as a temperature function. At 298 K, the standard molar reaction enthalpy [Delta][sub r]H[sub m][degree](298 K, 1.6 MPa) for MTBE and ETBE are [minus](37.3 [+-] 2) and [minus](34.8 [+-] 1.3) kJ/mol, respectively, and are compared with literature data. A comparison of the equilibrium constant values with those obtained using pure reactants with and without small initial amounts of water (<5 wt %) is also included. The UNIFAC estimates of activity coefficients were used to describe the liquid-phase nonideality. The standard molar enthalpies of formation [Delta][sub f]H[sub m][degree](l, 298.2 K) of MTBE and ETBE are [minus]313.5 and [minus]349.9 kJ/mol, respectively.

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

1994-11-01

72

Accelerometer signal-based human activity recognition using augmented autoregressive model coefficients and artificial neural nets  

Microsoft Academic Search

Automatic recognition of human activities is one of the important and challenging research areas in proactive and ubiquitous computing. In this work, we present some preliminary results of recognizing human activities using augmented features extracted from the activity signals measured using a single triaxial accelerometer sensor and artificial neural nets. The features include autoregressive (AR) modeling coefficients of activity signals,

A. M. Khan; Y. K. Lee; T.-S. Kim

2008-01-01

73

The Use of Amalgam Electrodes to Measure Activity Coefficients of Metal Salts in Multicomponent Salt Solutions.  

National Technical Information Service (NTIS)

The importance of activity coefficient measurements to the development and engineering of desalination processes is discussed. An outline of the research program and a list of abstracts of ten published papers resulting therefrom are given. Unpublished wo...

J. N. Butler R. Huston

1969-01-01

74

Headspace gas chromatography for measurement of infinite dilution activity coefficients of C 4 alcohols in water  

Microsoft Academic Search

For environmental and other reasons, there is interest in determining values of infinite dilution activity coefficients (??) of organic solutes in volatile solvents, particularly in water. Here, we present a detailed description of a headspace gas chromatograph recently constructed for the measurement of infinite dilution activity coefficients and report values of ?? for 1-butanol, 2-butanol, 2-methyl-1-propanol (iso-butanol) and 2-methyl-2-propanol (tert-butanol)

Paul G Whitehead; Stanley I Sandler

1999-01-01

75

Prediction and correlation of triglyceride–solvent solid–liquid equilibria with activity coefficient models  

Microsoft Academic Search

Solid–liquid equilibria (SLE) for solvent–triacylglyceride (TAG) systems are studied with activity coefficient models. Systems consisted of 29 data sets of C10:0 to C18:0 saturated triglycerides in nine solvents, benzene, acetone, carbon disulfide, carbon tetrachloride, chloroform, diethyl ether, ethanol, ethyl acetate, and n-hexane making up 562 data points. Eighteen activity coefficient models containing 0–2 fitting parameters were evaluated including a number

R. L. Smith; G. M. Acosta; K. Arai

1998-01-01

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

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

78

Liquid-Phase Immunoassays Using Brownian Relaxation of Magnetic Markers  

Microsoft Academic Search

We have developed a liquid-phase immunoassay technique using Brownian relaxation of magnetic markers. In this method, biological targets are fixed on the surface of large polymer beads whose size is typically a few . When the markers are bound to the targets, their Brownian relaxation time is dominated by that of the polymer bead, becoming much longer than that of

Anwarul Kabir Bhuiya; Tetsu Mitake; Masaki Asai; Tomoya Ito; Schunichi Chosakabe; Takashi Yoshida; Keiji Enpuku; Akihiko Kandori

2011-01-01

79

Liquid-phase compositions from vapor-phase analyses  

Microsoft Academic Search

In the safe handling and processing of uranium hexafluoride (UFâ), 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

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

1989-01-01

80

Current Controlled LPE (Liquid Phase Epitaxy) Growth of Semiconductors.  

National Technical Information Service (NTIS)

The primary objective of this study was to determine the optimum growth parameters for preparing uniform epitaxial crystalline layers of InAs, InSb, InAsSb and Si using the current controlled liquid phase epitaxy (CCLPE) technique. The original objective ...

E. K. Stefanakos A. Abul-Fadl W. J. Collis S. Iyer

1984-01-01

81

Oxidation Protection of Uranium Nitride Fuel Using Liquid Phase Sintering.  

National Technical Information Service (NTIS)

Two methods are proposed to increase the oxidation resistance of uranium nitride (UN) nuclear fuel. These paths are: (1) Addition of USi(sub x) (e.g. U3Si2) to UN nitride powder, followed by liquid phase sintering, and (2) 'alloying' UN nitride with vario...

P. A. Lessing

2012-01-01

82

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

83

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

84

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

85

Influence of sintering temperature on photoluminescence of Gd2O3:Eu3+ phosphors prepared by liquid phase reaction method.  

PubMed

Nanostructured materials with diameters less than 100 nm have been studied vigorously in recent years. Many studies have been devoted on exceptional optical properties induced by quantum confinement for fundamental research and applications. For excellent luminescence characteristics, phosphor particles have to acquire fine size, narrow size distribution, non-aggregation, good crystalline, and spherical morphology. A liquid-phase reaction method was chosen in this study due to the low reaction temperature. Gd2O3:Eu3+ phosphors were synthesized by the liquid-phase reaction method and the effect of activation temperature on optical properties of the phosphors was investigated. PMID:22630011

Park, Chung-Sik; Kwak, Min-Ki; Song, Yo-Seung; Lee, Koo-Hyun; Lee, Deuk Yong

2012-02-01

86

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

87

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

SciTech Connect

The Liquid Phase Methanol (LPMEOH) 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). Ak Products and Chemicals, Inc. (Air Products) and Eastman Chemical Company (Eastman) formed the Partnership to execute the Demonstration Project. The LPMEOITM Process Demonstration Unit was built at a site located at the Eastman complex in Kingsport. During this reporting period, DOE accepted the recommendation to continue with dimethyl ether (DME) design verification testing (DVT). DME design verification testing studies show the liquid phase DME (LPDME) process will have a significant economic advantage for the coproduction of DME for local markets. An LPDME catalyst system with reasonable long-term activity and stzibility is being developed. Planning for a proof-of-concept test run at the LaPorte Alternative Fuels Development Unit (AFDU) was recommended. DOE issued a letter dated 31 July 1997 accepting the recommendation to continue design verification testing. In order to allow for scale-up of the manufacturing technique for the dehydration catalyst from the pilot plant to the commercial scale, the time required to produce the catalyst to the AFDU has slipped. The new estimated delivery date is 01 June 1998.

None

1997-09-30

88

Microstructure evolution and densification of alumina in liquid phase sintering  

NASA Astrophysics Data System (ADS)

The microstructure evolution and densification of alumina during liquid phase sintering were quantified. Quantification included the evolution of pore-size distribution, the redistribution of liquid phase, the densification kinetics, and the fraction of closed and open pores. The results revealed that the small and large pores were filled simultaneously. This is inconsistent with Shaw's model in which liquid fills preferentially the smaller low-coordination-number pores in order to reach a low-energy configuration. The results also recommended that the pressure build-up of the trapped gases in pores due to the closure of open pores might have a significantly negative contribution to the driving force, and consequently cause the termination of the densification of alumina. To demonstrate whether the trapped gases played an important role in the microstructure evolution and the densification of alumina during liquid phase sintering, the following two experiments have been conducted. First, alumina preforms containing artificial pores were penetrated by glass. The results indicated that the trapped gases in pores had a considerable influence on the pore filling process, and ultimately caused the termination of the densification of the alumina preforms. Second, alumina compacts containing different amount of glass were sintered in vacuum. The alumina compact containing 20 vol. % reached full density during vacuum sintering, indicating that the pressure build-up of the trapped gases in pores was the main factor causing the termination of the densification of alumina in the final stage of liquid phase sintering. The limiting relative densities of compacts were calculated theoretically on the basis of a comprehensive analysis of the variation of the capillary pressure and gas pressure in pores with pore size and pore number. The capillary pressure and gas pressure in alumina compact during liquid phase sintering were analyzed on the basis of the above theoretical models and the obtained quantitative experiment data. The calculated compressive pressure at particle contacts decreased significantly during the final stage of sintering due to the large increase of the gas pressure in the closed pores as the number of the closed pores and their size decreased. The derived time exponent of linear shrinkage from the decreasing compressive pressure at particle contacts and a modified Kingery's contact flattening model was consistent with the value obtained from the experimentally measured relative densities. These results indicated that the pressure build-up of the trapped gases in the compact was primarily responsible for the inhibited densification of the alumina compact in the final stage of liquid phase sintering.

Dong, Weimin

89

Determination of activity coefficients of neutral species in supercritical H2O solutions  

NASA Astrophysics Data System (ADS)

Based on a standard state of unit activity of the solute in a hypothetical one molal solution where activity coefficients are taken as unity at infinite dilution at all pressures and temperatures, the activity coefficients of neutral species generally increase with increasing ionic strength at 25°C. However, activity coefficients of polar species begin to decrease with increasing ionic strength as temperature increases in supercritical aqueous solutions. The increased stability of polar neutral ion pairs helps explain the increase in the solubility of silicate minerals in supercritical aqueous solutions as electrolyte concentrations increase. This is demonstrated for measurements of talc plus quartz solubility in supercritical aqueous NaCl solutions. Increased ion association to form new species in supercritical solutions beyond the formation of neutral ion pairs is, apparently, not important for understanding mineral solubilities in most crustal aqueous solutions.

Walther, John V.

1997-08-01

90

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

91

Improved process for liquid phase deposition of silicon dioxide  

Microsoft Academic Search

An improved process for liquid phase deposition of silicon dioxide (SiO2) at 50 °C is successfully developed. Contrary to conventional processes, silicic acid (SiO2:xH2O) is used instead of SiO2 powder to saturate hydrofluorosilicic acid at 30 °C. This will shorten the period required for solution preparation to 3 h. Water is now taking the role of boric acid (or Al)

Jenq-Shiuh Chou; Si-Chen Lee

1994-01-01

92

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

93

Liquid phase hydrogenation of cinnamaldehyde on Cu-based catalysts  

Microsoft Academic Search

The liquid phase hydrogenation of cinnamaldehyde was studied at 393K and 10bar on Cu-based catalysts containing about 12wt.% of copper. Cu\\/SiO2 was prepared by incipient wetness impregnation while Cu–Al, Cu–Zn–Al, and Cu–Ni(Co)–Zn–Al catalysts were obtained by coprecipitation at constant pH. Cinnamaldehyde was initially hydrogenated to cinnamyl alcohol and hydrocinnamaldehyde, and these products consecutively yielded hydrocinnamyl alcohol. Hydrogenation kinetic constants were

Alberto J Marchi; Diego A Gordo; Andrés F Trasarti; Carlos R Apestegu??a

2003-01-01

94

Modeling transient liquid phase bonding in multicomponent systems  

Microsoft Academic Search

Transient liquid phase (TLP) bonding is finding use in applications that require high thermal, electrical, chemical, and\\/or\\u000a mechanical stability such as in electrical connectors, turbine vanes, and metal-matrix composites. To date, much work has\\u000a been done to quantify the behavior of binary material combinations during the rate-limiting isothermal solidification step\\u000a of TLP bonding. However, this model is not general enough

C. W. Sinclair

1999-01-01

95

Oxidation Protection of Uranium Nitride Fuel using Liquid Phase Sintering  

SciTech Connect

Two methods are proposed to increase the oxidation resistance of uranium nitride (UN) nuclear fuel. These paths are: (1) Addition of USi{sub x} (e.g. U3Si2) to UN nitride powder, followed by liquid phase sintering, and (2) 'alloying' UN nitride with various compounds (followed by densification via Spark Plasma Sintering or Liquid Phase Sintering) that will greatly increase oxidation resistance. The advantages (high thermal conductivity, very high melting point, and high density) of nitride fuel have long been recognized. The sodium cooled BR-10 reactor in Russia operated for 18 years on uranium nitride fuel (UN was used as the driver fuel for two core loads). However, the potential advantages (large power up-grade, increased cycle lengths, possible high burn-ups) as a Light Water Reactor (LWR) fuel are offset by uranium nitride's extremely low oxidation resistance (UN powders oxidize in air and UN pellets decompose in hot water). Innovative research is proposed to solve this problem and thereby provide an accident tolerant LWR fuel that would resist water leaks and high temperature steam oxidation/spalling during an accident. It is proposed that we investigate two methods to increase the oxidation resistance of UN: (1) Addition of USi{sub x} (e.g. U{sub 3}Si{sub 2}) to UN nitride powder, followed by liquid phase sintering, and (2) 'alloying' UN nitride with compounds (followed by densification via Spark Plasma Sintering) that will greatly increase oxidation resistance.

Dr. Paul A. Lessing

2012-03-01

96

Temperature dependence of infinite dilution activity coefficients in octanol and octanol/water partition coefficients of some volatile halogenated organic compounds  

SciTech Connect

The study of the fate and transport of volatile halogenated organic compounds in the environment is of interest as these chemicals, many of which have been classified as pollutants, are widely used as industrial solvents and are now appearing in water supplies. Infinite dilution activity coefficients and Henry`s law coefficients have been measured for 11 halogenated C{sub 1} to C{sub 3} compounds in 1-octanol above room temperature using a gas-liquid chromatographic measurement method. Then, using their earlier data for these substances in water and a correlation relating the limiting activity coefficients of a substance in pure water and in pure 1-octanol to their octanol/water partition coefficients, these latter quantities have been computed. One conclusion from these measurements is that the limiting activity coefficients in octanol and the octanol/water partition coefficients of the halogenated compounds studied are only weakly dependent on temperature over the range from 25 to 50 C. Also, from these and their earlier data, have estimated the infinite dilution partial molar excess enthalpies and excess entropies of these compounds in both 1-octanol and water.

Bhatai, S.R.; Sandler, S.I. [Univ. of Delaware, Newark, DE (United States)

1995-11-01

97

Activity coefficient of CuO0.5 in alumina saturated iron silicate slags  

NASA Astrophysics Data System (ADS)

Activity coefficient of CuO0.5 was determined in alumina saturated iron silicate slags by equilibrating with pure copper in alumina crucibles at Fe/SiO2 = 1.34, temperature of 1473 to 1573 K, and Po2 = 10-8 to 10-10 atm. The activity coefficient of CuO0.5 in the slag increased with alumina content of the slag and decreased with increasing temperature. A linear regression relationship between CuO0.5 and temperature at a fixed pet AlO1.5 was derived. The distribution coefficient of copper (R) increased with decreasing temperature, and a linear regression relation obtained for 0 to 16 pet AlO1.5 was: In R = 3308/T + 0.99.

Reddy, R. G.; Acholonu, C. C.

1984-06-01

98

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

99

Very low-threshold separate-confinement-heterostructure lasers prepared by liquid phase epitaxy  

SciTech Connect

AlGaAs separate-confinement-heterostructure lasers with low threshold current density (lowest averaged J/sub th/ of 317 A cm/sup -2/) are reproducibly prepared by liquid phase epitaxy. All optical-cavity layers of the lasers are undoped and their compositions are not graded. The low threshold is attained by increased internal efficiency resulting from effective injection of electrons into the active layer in the thin cavity, as well as by low internal loss of the optical cavity.

Mukai, S.; Tsunekawa, Y.; Takabe, Y.; Yajima, H.

1985-07-15

100

Short-term liquid-phase epitaxy of gallium arsenide from bismuth melt  

SciTech Connect

This work is devoted to producing thin epitaxial GaAs layers from a solution in molten bismuth. From an analysis of the experimental data on short-term liquid-phase epitaxy the applicability of the diffusion-limited growth model to the epitaxy of GaAs from molten bismuth solution is confirmed. It is shown that an increase in the thickness of the GaAs layers with increasing epitaxial temperature is principally related to the decrease in the slope of the liquids line. The value of the co-diffusion coefficient of Ga and As in the bismuth melt is experimentally estimated in the temperature range 700-900/sup 0/ c.

Maronchuk, Yu. E. Lenin Komsomol Novosibirsk State University; Rudaya, N.S.; Yakusheva, N.A.

1986-08-01

101

Determination of Effective Diffusivity Coefficient and Activation Energy Of shelled pistachio by using fluidized bed dryer  

Microsoft Academic Search

Knowledge of desorption kinetics is essential to predict the behavior of the material during drying process and to design dryer equipment .The main objective of this study is to obtain the effective diffusivity coefficient and activation energy of shelled pistachio. Another goal is to find drying kinetics of shelled pistachio in fluidized bed dryer and so thin-layer characteristics of shelled

V. Mohammadpour; M. T. Hamed Mosavian; A. Etemadi

102

Activity Coefficients of Acetone-Chloroform Solutions: An Undergraduate Experiment. Undergraduate Experiment.  

ERIC Educational Resources Information Center

|Presents information, laboratory procedures, and results of an undergraduate experiment in which activity coefficients for a two-component liquid-vapor system are determined. Working in pairs, students can perform the experiment with 10 solutions in a given three-hour laboratory period. (Author/JN)|

Ozog, J. Z.; Morrison, J. A.

1983-01-01

103

Extending the Diffuse Layer Model of Surface Acidity Behavior: III. Estimating Bound Site Activity Coefficients  

EPA Science Inventory

Although detailed thermodynamic analyses of the 2-pK diffuse layer surface complexation model generally specify bound site activity coefficients for the purpose of accounting for those non-ideal excess free energies contributing to bound site electrochemical potentials, in applic...

104

Measurement of activity coefficients of mixtures by head-space gas chromatography: general procedure.  

PubMed

Head-space gas chromatography (HS-GC) is an applicable method to perform vapor-liquid equilibrium measurements and determine activity coefficients. However, the reproducibility of the data may be conditioned by the experimental procedure concerning to the automated pressure-balanced system. The study developed in this work shows that a minimum volume of liquid in the vial is necessary to ensure the reliability of the activity coefficients since it may become a parameter that influences the magnitude of the peak areas: the helium introduced during the pressurization step may produce significant variations of the results when too small volume of liquid is selected. The minimum volume required should thus be evaluated prior to obtain experimentally the concentration in the vapor phase and the activity coefficients. In this work, the mixture acetonitrile-toluene is taken as example, requiring a sample volume of more than 5mL (about more than 25% of the vial volume). The vapor-liquid equilibrium and activity coefficients of mixtures at different concentrations (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 molar fraction) and four temperatures (35, 45, 55 and 70°C) have been determined. Relative standard deviations (RSD) lower than 5% have been obtained, indicating the good reproducibility of the method when a sample volume larger than 5mL is used. Finally, a general procedure to measure activity coefficients by means of pressure-balanced head-space gas chromatography is proposed. PMID:23809803

Luis, Patricia; Wouters, Christine; Van der Bruggen, Bart; Sandler, Stanley I

2013-06-14

105

Two Spin Liquid phases in the anisotropic triangular Heisenberg model  

NASA Astrophysics Data System (ADS)

Recently there have been rather clean experimental realizations of the quantum spin 1/2 Heisenberg Hamiltonian on a 2D triangular lattice geometry in systems like Cs2Cu Cl4 and organic compounds like k-(ET)2Cu2(CN)3. These materials are nearly two dimensional and are characterized by an anisotropic antiferromagnetic superexchange. The strength of the spatial anisotropy can increase quantum fluctuations and can destabilize the magnetically ordered state leading to non conventional spin liquid phases. In order to understand these interesting phenomena we have studied, by Quantum Monte Carlo methods, the triangular lattice Heisenberg model as a function of the strength of this anisotropy, represented by the ratio r between the intra-chain nearest neighbor coupling J' and the inter-chain one J. We have found evidence of two spin liquid regions, well represented by projected BCS wave functions[1,2] of the type proposed by P. W. Anderson at the early stages of High temperature superconductivity [3]. The first spin liquid phase is stable for small values of the coupling r 0.6 and appears gapless and fractionalized, whereas the second one is a more conventional spin liquid, very similar to the one realized in the quantum dimer model in the triangular lattice[4]. It is characterized by a spin gap and a finite correlation length, and appears energetically favored in the region 0.6 r 0.9. The various phases are in good agreement with the experimental findings and supports the existence of spin liquid phases in 2D quantum spin-half systems. %%%%%%%%%%%%%%%%%% 1cm *[1] L. Capriotti F. Becca A. Parola and S. Sorella , Phys. Rev. Letters 87, 097201 (2001). *[2] S. Yunoki and S. Sorella Phys. Rev. Letters 92, 15003 (2004). *[3] P. W. Anderson, Science 235, 1186 (1987). *[4] P. Fendley, R. Moessner, and S. L. Sondhi Phys. Rev. B 66, 214513 (2002).

Sorella, Sandro

2005-03-01

106

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

107

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

108

Interfacial embrittlement in liquid-phase sintered tungsten heavy alloys  

Microsoft Academic Search

The variations in toughness of the liquid-phase sintered heavy alloys W-Ni-Fe and W-Ni-Cu have been examined. Toughness was\\u000a found to be controlled primarily by the strength of the tungsten particle-matrix interfaces, which is sensitive to the rate\\u000a of cooling from the sintering temperature. Furnace-cooling led to the embrittlement of these interfaces; in the case of W-Ni-Fe\\u000a transmission electron microscopy identified

D. V. Edmonds; P. N. Jones

1979-01-01

109

Topological and spin-liquid phases in strongly correlated iridates  

NASA Astrophysics Data System (ADS)

Recently, the emergence of topological phases in interacting electron systems such as topological insulators and spin liquid phases, has been a subject of intensive research. In particular, much attention has been given to 5d transition metal oxides where the strong spin-orbit coupling and intermediate strength of the electron interaction provide an ideal playground for the emergence of a number of interesting topological phases. We summarize recent theoretical efforts in this direction in the context of Iridates, or iridium oxides. We make connections to the existing and future experiments on a variety of iridates materials including pyrochlore iridates, honeycomb-lattice iridates, and hyperkagome-lattice systems.

Kim, Yong Baek

2012-02-01

110

Modeling liquid-liquid phase transitions and quasicrystal formation  

NASA Astrophysics Data System (ADS)

In this thesis, studies which concern two different subjects related to phase transitions in fluids and crystalline solids are presented. Condensed matter formation, structure, and phase transitions are modeled using molecular dynamics simulations of simple discontinuous potentials with attractive and repulsive interactions. Novel phase diagrams are proposed for quasicrystals, crystals, and liquids. In the first part of the thesis, the formation of a quasicrystal in a two dimensional monodisperse system is investigated using molecular dynamics simulations of hard sphere particles interacting via a two-dimensional square-well potential. It is found that for certain values of the square-well parameters more than one stable crystalline phase can form. By quenching the liquid phase at a very low temperature, an amorphous phase is obtained. When this the amorphous phase is heated, a quasicrystalline structure with five-fold symmetry forms. From estimations of the Helmholtz potentials of the stable crystalline phases and of the quasicrystal, it is concluded that within a specific temperature range, the observed quasicrystal phase can be the stable phase. The second part of the thesis concerns a study of the liquid-liquid phase transition for a single-component system in three dimensions, interacting via an isotropic potential with a repulsive soft-core shoulder at short distance and an attractive well at an intermediate distance. The potential is similar to potentials used to describe such liquid systems as colloids, protein solutions, or liquid metals. It is shown that the phase diagram for such a potential can have two lines of first-order fluid-fluid phase transitions: one separating a gas and a low-density liquid (LDL), and another between the LDL and a high-density liquid (HDL). Both phase transition lines end in a critical point, a gas-LDL critical point and, depending on the potential parameters, either a gas-HDL critical point or a LDL-HDL critical point. A systematic study through varying potential parameters is carried out to determine the influence of attractive and repulsive interactions on the formation and stability of the liquid-liquid phase transitions and the two fluid critical points. No hints of the density anomaly are found, suggesting that the absence of the density anomaly, such as the one found in water, is independent of the choice of the parameters and that the liquid-liquid phase transition and density anomaly are not directly related.

Skibinsky, Anna

111

Liquid Phase Oxidation of p- Cresol over Cobalt Saponite  

Microsoft Academic Search

Liquid phase oxidation of p-cresol was carried out over a Co-saponite catalyst in a temperature and pressure range of 333–393 K and 20–827 kPa, respectively\\u000a in n-propanol. Co-saponites with varying cobalt content (5–30%) were prepared and screened among which 13% Co-saponite gave\\u000a the highest conversion of 92% of p-cresol with 92% selectivity to p-hydroxybenzaldehyde without formation of any non-oxidation products.

Vikas S. Kshirsagar; Ajit C. Garade; Kashinath R. Patil; Masayuki Shirai; Chandrashekhar V. Rode

2009-01-01

112

Environmental information volume: Liquid Phase Methanol (LPMEOH{trademark}) project  

SciTech Connect

The purpose of this project is to demonstrate the commercial viability of the Liquid Phase Methanol Process using coal-derived synthesis gas, a mixture of hydrogen and carbon monoxide. This report describes the proposed actions, alternative to the proposed action, the existing environment at the coal gasification plant at Kingsport, Tennessee, environmental impacts, regulatory requirements, offsite fuel testing, and DME addition to methanol production. Appendices include the air permit application, solid waste permits, water permit, existing air permits, agency correspondence, and Eastman and Air Products literature.

NONE

1996-05-01

113

Reaction calorimetry study of the liquid-phase synthesis of tert-butyl methyl ether  

SciTech Connect

The liquid-phase addition of methanol to isobutene to give tert-butyl methyl ether (MTBE) on the ion-exchange resin Lewatit K2631 has been studied in a calorimetric reactor. Heat capacity of MTBE and enthalpy of the MTBE synthesis reaction in the temperature range 312--333 K have been determined. MTBE heat capacity in the liquid phase has been found to obey the equation c[sub P] (J/mol[center dot]K) = 472.34 [minus] 2.468(T/K) + 0.005071(T/K)[sup 2]. At 298 K the standard molar reaction enthalpy is [Delta]H[degree] = [minus]33.8 kJ/mol. A method to estimate apparent activation energies from heat flow rate in a given reaction has been developed and proved to be valid for the MTBE synthesis. Using this method, an apparent activation energy of 91.1--95.2 kJ/mol is calculated. A [minus]3.8 kJ/mol value has been found for the adsorption enthalpy of methanol on the ion-exchange resin Lewatit K2631 by a combination of reaction calorimetry and thermogravimetry. This allows the calculation of an activation energy on the gel phase of the resin of 91 kJ/mol.

Sola, L.; Pericas, M.A.; Cunill, F.; Iborra, M. (Univ. de Barcelona (Spain). Dept. d'Enginyeria Quimica)

1994-11-01

114

Models for a liquid-liquid phase transition  

NASA Astrophysics Data System (ADS)

We use molecular dynamics simulations to study two- and three-dimensional models with the isotropic double-step potential which in addition to the hard core has a repulsive soft core of larger radius. Our results indicate that the presence of two characteristic repulsive distances (hard core and soft core) is sufficient to explain liquid anomalies and a liquid-liquid phase transition, but these two phenomena may occur independently. Thus liquid-liquid transitions may exist in systems like liquid metals, regardless of the presence of the density anomaly. For 2D, we propose a model with a specific set of hard core and soft core parameters, that qualitatively reproduces the phase diagram and anomalies of liquid water. We identify two solid phases: a square crystal (high density phase), and a triangular crystal (low density phase) and discuss the relation between the anomalies of liquid and the polymorphism of the solid. Similarly to real water, our 2D system may have the second critical point in the metastable liquid phase beyond the freezing line. In 3D, we find several sets of parameters for which two fluid-fluid phase transition lines exist: the first line between gas and liquid and the second line between high-density liquid (HDL) and low-density liquid (LDL). In all cases, the LDL phase shows no density anomaly in 3D. We relate the absence of the density anomaly with the positive slope of the LDL-HDL phase transition line.

Buldyrev, S. V.; Franzese, G.; Giovambattista, N.; Malescio, G.; Sadr-Lahijany, M. R.; Scala, A.; Skibinsky, A.; Stanley, H. E.

2002-02-01

115

Modeling the solid-liquid phase transition in saturated triglycerides.  

PubMed

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 approximately 120 degrees 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 DeltaH. 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 DeltaH 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 DeltaH that was too small by a factor of approximately 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 degrees C < or = T < or = 90 degrees 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. PMID:20136317

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

2010-02-01

116

A Computationally Efficient Model for Multicomponent Activity Coefficients in Aqueous Solutions  

SciTech Connect

Three-dimensional models of atmospheric inorganic aerosols need an accurate yet computationally efficient parameterization of activity coefficients, which are repeatedly updated in aerosol phase equilibrium and gas-aerosol partitioning calculations. In this paper, we describe the development and evaluation of a new mixing rule for estimating multicomponent activity coefficients of electrolytes typically found in atmospheric aerosol systems containing H(+), NH4(+), Na(+), Ca(2+), SO4(2-), HSO4(-), NO3(-), and Cl(-) ions. The new mixing rule, called MTEM (Multicomponent Taylor Expansion Model), estimates the mean activity coefficient of an electrolyte A in a multicomponent solution from a linear combination of its values in ternary solutions of A-A-H2O, A-B-H2O, A-C-H2O, etc., as the amount of A approaches zero in the mixture at the solution water activity, aw, assuming aw is equal to the ambient relative humidity. Predictions from MTEM are found to be within a factor of 0.8 to 1.25 of the comprehensive Pitzer-Simonson-Clegg (PSC) model over a wide range of water activities, and are shown to be significantly more accurate than the widely used Kusik and Meissner (KM) mixing rule, especially for electrolytes in sulfate-rich aerosol systems and for relatively minor but important aerosol components such as HNO3 and HCl acids. Because the ternary activity coefficient polynomials are parameterized as a function of aw, they have to be computed only once at every grid point at the beginning of every 3-D model time step as opposed to repeated evaluations of the ionic strength dependent binary activity coefficient polynomials in the KM method. Additionally, MTEM also yields a non-iterative solution of the bisulfate ion dissociation in sulfate-rich systems, which is a major computational advantage over other iterative methods as will be shown by a comparison of the CPU time requirements of MTEM for both sulfate-poor and sulfate-rich systems relative to other methods.

Zaveri, Rahul A.; Easter, Richard C.; Wexler, Anthony S.

2004-10-04

117

Activity coefficient models to describe isothermal vapor-liquid equilibrium of binary systems containing ionic liquids  

Microsoft Academic Search

Isothermal vapor-liquid equilibrium data of binary mixtures containing ionic liquids are correlated using three activity coefficient\\u000a models: UNIQUAC, Wilson, and NRTL. Twenty binary systems taken from the literature were selected for this study. A genetic\\u000a algorithm is used to determine the interaction parameters for the three models. The results given by the three models have\\u000a been compared with experimental data,

J. A. Lazzús; J. Marín

2010-01-01

118

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

119

Physical chemistry of the zinc-bromine battery: I. Activity coefficients of aqueous zinc bromide  

Microsoft Academic Search

The potential of the cell Zn-Hg(2 phase)|ZnBr2(m)|AgBr|Ag was measured from 0 to 35.9°C and for molalities from 0.125 to 4.0. From these results and values of the standard cell potential, activity coefficients of aqueous zinc bromide were calculated. Good agreement was found with the emf and isopiestic results of Stokes and Stokes, where the ranges of temperature and molality overlap.

H. Frank Gibbard

1981-01-01

120

Study of activity coefficients for sodium iodide in (methanol + benzene) system by (vapour + liquid) equilibrium measurements  

Microsoft Academic Search

By measuring the (vapour+liquid) equilibrium of {methanol (1)+benzene (2)+NaI} and testing the data using the ternary Gibbs–Duhem equation, the experimental results of the (vapour+liquid) equilibrium with thermodynamic consistency are obtained. It is supposed that the mean activity coefficients of NaI in (methanol+benzene) mixed solvents may be represented by a power series of salt concentration (m1\\/2). Each parameter of the series

Meifang Yang; Chunli Leng; Shucai Li; Renyi Sun

2007-01-01

121

Measurement of gas/water uptake coefficients for trace gases active in the marine environment. [Annual report  

SciTech Connect

Ocean produced reduced sulfur compounds including dimethylsulfide (DMS), hydrogen sulfide (H{sub 2}S), carbon disulfide (CS{sub 2}), methyl mercaptan (CH{sub 3}CH) and carbonyl sulfide (OCS) deliver a sulfur burden to the atmosphere which is roughly equal to sulfur oxides produced by fossil fuel combustion. These species and their oxidation products dimethyl sulfoxide (DMSO), dimethyl sulfone (DMSO{sub 2}) and methane sulfonic acid (MSA) dominate aerosol and CCN production in clean marine air. Furthermore, oxidation of reduced sulfur species will be strongly influenced by NO{sub x}/O{sub 3} chemistry in marine atmospheres. The multiphase chemical processes for these species must be understood in order to study the evolving role of combustion produced sulfur oxides over the oceans. We have measured the chemical and physical parameters affecting the uptake of reduced sulfur compounds, their oxidation products, ozone, and nitrogen oxides by the ocean`s surface, and marine clouds, fogs, and aerosols. These parameters include: gas/surface mass accommodation coefficients; physical and chemically modified (effective) Henry`s law constants; and surface and liquid phase reaction constants. These parameters are critical to understanding both the interaction of gaseous trace species with cloud and fog droplets and the deposition of trace gaseous species to dew covered, fresh water and marine surfaces.

Davidovits, P. [Boston Coll., Chestnut Hill, MA (United States). Dept. of Chemistry; Worsnop, D.W.; Zahniser, M.S.; Kolb, C.E. [Aerodyne Research, Inc., Billerica, MA (United States). Center for Chemical and Environmental Physics

1992-02-01

122

Liquid-phase alkylation of benzene with light olefins catalyzed by {beta} zeolites  

SciTech Connect

The catalytic performance of zeolite {beta} in the liquid-phase alkylation of benzene is compared with that of other solid catalysts. Zeolite {beta} is more active and more selective than zeolite Y in the alkylation with propylene and ethylene to cumene and ethylbenzene (EB). In the alkylation with propylene the overall selectivity of {beta} is higher than that of the traditional {open_quotes}solid phosphoric acid.{close_quotes} The catalytic activity is affected by the composition and the particle size of zeolite {beta} samples. Decreasing the framework Al content, by direct synthesis or by partial substitution of Al for B, produces a decrease in both conversion and selectivity in cumene and EB synthesis. A hypothesis to explain this behavior is given. The catalytic activity of zeolite {beta} is limited by intraparticle diffusion, as evidenced by the decreased activity corresponding to the particle size increase. 22 refs., 7 figs., 10 tabs.

Bellussi, G.; Pazzuconi, G.; Perego, C. [Eniricerche SpA, Milanese (Italy)] [and others

1995-11-01

123

Spike detection in human muscle sympathetic nerve activity using the kurtosis of stationary wavelet transform coefficients.  

PubMed

The accurate assessment of autonomic sympathetic function is important in the diagnosis and study of various autonomic and cardiovascular disorders. Sympathetic function in humans can be assessed by recording the muscle sympathetic nerve activity, which is characterized by synchronous neuronal discharges separated by periods of neural silence dominated by colored Gaussian noise. The raw nerve activity is generally rectified, integrated, and quantified using the integrated burst rate or area. We propose an alternative quantification involving spike detection using a two-stage stationary wavelet transform (SWT) de-noising method. The SWT coefficients are first separated into noise-related and burst-related coefficients on the basis of their local kurtosis. The noise-related coefficients are then used to establish a threshold to identify spikes within the bursts. This method demonstrated better detection performance than an unsupervised amplitude discriminator and similar wavelet-based methods when confronted with simulated data of varying burst rate and signal to noise ratio. Additional validation on data acquired during a graded head-up tilt protocol revealed a strong correlation between the mean spike rate and the mean integrate burst rate (r=0.85) and burst area rate (r=0.91). In conclusion, the kurtosis-based wavelet de-noising technique is a potentially useful method of studying sympathetic nerve activity in humans. PMID:17083982

Brychta, Robert J; Shiavi, Richard; Robertson, David; Diedrich, André

2006-11-02

124

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

125

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

126

DETERMINATION OF INFINITE DILUTION ACTIVITY COEFFICIENTS FOR ORGANIC-AQUEOUS SYSTEMS USING A DILUTE VAPOR-LIQUID EQUILIBRIUM METHOD  

Microsoft Academic Search

A low pressure vapor-liquid equilibrium apparatus has been developed, tested and verified for the measurements of dilute solution activity coefficients for different organic solutes in aqueous systems. Activity coefficient data were measured for aqueous binary mixtures involving methanol, acetone, and benzene at 25°C. The experimental measurements targeted the range of solute liquid compositions extending from the Gas Chromalograph detection limit

M. S. H. BADER; K. A. M. GASEM

1995-01-01

127

Liquid phase alkylation of phenol with 4-hydroxybutan-2-one in the presence of modified zeolite HBEA  

Microsoft Academic Search

Liquid phase alkylation of phenol with 4-hydroxybutan-2-one was carried out in presence of H-beta zeolite modified by different techniques, such as thermal treatment, acid washing, ion-exchange and surface passivation. Thermal- and acid-treated samples showed decrease in activity due to the removal of aluminium from the framework. The new Lewis acid sites generated by thermal treatment increased the selectivity of the

Kanakkampalayam Krishnan Cheralathan; Inguva Sudarsan Kumar; Muthiahpillai Palanichamy; Velayutham Murugesan

2003-01-01

128

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

129

Direct observation of liquid-phase sintering in the system iron-copper  

Microsoft Academic Search

The hot-stage of a scanning electron microscope has been used to observe liquid-phase sintering in the system iron-copper. The densification behaviour of compacts of Fe and Cu particles were determined. The influence of particle size of both components and the amount of liquid phase developed were investigated. In samples with about 20 vol % liquid phase, the densification kinetics as

Leonhard Froschauer; Richard M. Fulrath

1975-01-01

130

Preparation of photocatalyst using diatom frustules by liquid phase deposition method.  

PubMed

We prepared a photocatalyst using diatom frustules by the liquid phase deposition (LPD) method. Purified native frustules were reacted with boric acid (H3BO3) and ammonium hexafluorotitanate ((NH4)2TiF6) in order to cover the frustule surface with a TiO2 film. Scanning electron microscopy (SEM) observation revealed that the nanoporous structures of the frustules and grown TiO2 layers were co-existent after the LPD treatment when the incubation period was 6 and 12 h. Furthermore, photocatalytic activity of the functionalized frustules was clearly proved by the decomposition of methylene blue (MB) molecules. When the incubation periods were 12 and 24 h, reasonable photocatalytic activity was obtained. The results suggested that higher photocatalytic activity was achieved without losing nanoporous structures when the frustules were treated for 12 h by the LPD method. PMID:21125823

Umemura, Kazuo; Gao, Yanfeng; Nishikawa, Tetsuya

2010-08-01

131

High temperature failure initiation in liquid phase sintered materials  

SciTech Connect

The mechanisms for initiation of high temperature failure in liquid-phase sintered (L.P.S.) ceramics are investigated. Results of a transmission electron microscopy study on silicon nitride exposed to creep strains at elevated temperature are used to propose a sequence for the early stages of cavitation damage, physical expressions are derived for the growth and coalescence times for oblate holes in thinglass films along two-grain interfaces. The times for formation of spherical holes along three-grain channel glass pockets and their subsequent growth to full-facet sized cavities by viscous flow and solution/reprecipitation mechanisms are evaluated. In combination, the failure expressions constitute the first step in the development of a time-to-failure model for high temperature deformation of L.P.S. ceramics.

Marion, J.E.; Clarke, D.R.; Drory, M.D.; Evans, A.G.

1983-10-01

132

ZnSe/Si growth by liquid phase deposition  

NASA Astrophysics Data System (ADS)

ZnSe is an important semiconductor material with a large bandgap (2.68 eV), which has the potential to be used for photoluminescent and eletroluminescent devices and for window layer of solar cells. In this work, a low-cost and large-area growth method for ZnSe layer on Si substrate was studied by liquid phase deposition (LPD). The micrograph of the surface shows specula but a roughness surface texture is obtained. The island texture could be improved by raising growth temperatures. The crystallinity could be improved by the growth temperature considerations. High resistivity and specular layers were obtained as grown at room temperature. The abrupt interface resulted from less interdiffusion between ZnSe layers and substrates was reasonable under the growth condition at room temperatures.

Yeh, MinYen; Yen, HungMing

2000-07-01

133

Liquid-Phase Shear Horizontal Surface Acoustic Wave Immunosensor  

NASA Astrophysics Data System (ADS)

In this paper, we describe liquid-phase immunosensors based on shear horizontal surface acoustic waves (SH-SAWs), which can be directly dipped into a liquid. The sensor devices are fabricated using an SH-SAW delay line on quartz and LiTaO3 substrates, which is composed of a transmitting floating electrode unidirectional transducer (FEUDT), receiving FEUDT, and a biochemical reaction area between them. These FEUDTs are protected from liquids by a glass lid and epoxy walls, which are constructed using a photolithography technique. Therefore, the sensor devices can be directly dipped into a liquid and a liquid can be directly applied onto the surface of the sensor devices. In order to evaluate basic characteristics of the sensor devices, glycerol-water mixture liquids of different viscosities were used. For evaluations of their applicability to immunoassay, human serum albumin antigen-antibody reactions were investigated.

Takashi Kogai,; Naoyuki Yoshimura,; Toshimasa Mori,; Hiromi Yatsuda,

2010-07-01

134

A refined potential for hydroxylamine clusters and the liquid phase  

NASA Astrophysics Data System (ADS)

A detailed study including ab initio calculations and classic Monte-Carlo simulations of hydroxylamine in the gas and liquid phases is presented. A classical interaction potential for hydroxylamine, which includes polarizability, many-body effects, and intramolecular relaxation, was constructed. The results of the simulation were compared to the available experimental data in order to validate the model. We conclude that liquid hydroxylamine has a multitude of hydrogen bonds leading to a large density where the existence of cis conformers and clusters of these conformers is possible. This explains the occurrence of the classical [R. Nast and I. Z. Foppl, Z. Anorg. Allg. Chem. 263, 310 (1950)] scheme for the molecule's decomposition at room temperature and its large exothermicity and instability.

González-Espinoza, Alfredo; Hernández-Cobos, Jorge; Ortega-Blake, Iván

2011-08-01

135

Kinetics of p-xylene liquid-phase catalytic oxidation  

SciTech Connect

A semibatch gas-liquid reactor model based on a lumped kinetic scheme for the liquid-phase oxidation of p-xylene to p-toluic acid catalyzed by cobalt naphthenate is developed. The model accounts for the complex nature of the involved reaction network, as well as for the interphase and intraphase mass transport processes of both reactants and products. The model reliability is tested by comparison with suitable experimental data obtained in a semibatch oxidation reactor, where the role of the composition of both the gaseous and the liquid feed has been investigated. It is shown that the model describes the reactor behavior in any of the regimes which may prevail depending upon the operating conditions and the depletion of liquid reactants in time.

Cao, G.; Servida, A. (Univ. di Cagliari (Italy). Dipt. di Ingegneria Chimica e Materiali); Pisu, M. (Sviluppo e Studi Superiori in Sardegna, Cagliari (Italy). Centro di Ricerche); Morbidelli, M. (Politecnico di Milano (Italy). Dipt. di Chimica Fisica Applicata)

1994-07-01

136

Reaction behaviors of mixed plastics in liquid-phase cracking  

SciTech Connect

The majority of waste plastics today is either incinerated or buried for landfills. However, incineration of waste plastics can cause damages in furnace and air pollution problems. Shortage of available landfill sites also has become a serious concern. The methods of waste plastic recycling therefore have been paid much attention with the viewpoint of effective environmental protection. Liquefaction of waste plastics is an attractive recycling method in terms of producing fuel oil or chemicals. To date, most of the waste plastic liquefaction investigations have been limited to the areas not involving the use of a solvent. Pilot-scaled plants, such as those in the Fuji Recycle Process in Japan and the VCC Process in Germany, have been operated for some time. Although high conversion of waste plastics can be obtained at a temperature as low as 400{degrees}C, problems such as wide molecular weight distribution in the produced oil and high coking tendency have been encountered. Liquid-phase cracking of waste plastics has the potential of overcoming these problems, yet few research has been reported on the liquefaction behaviors for the liquid-phase cracking. Polyethylene (PE) has been regarded as one of the polymers difficult to liquefy, while the cracking of polystyrene (PS) is considered to proceed in a way different from that of PE. Hence, we investigated the cracking of PS, PE, and their mixtures using solvents of different hydrogen donation capability. Differences in the liquefaction behaviors between PS and PE, influences of the solvent type, synergistic effects for the liquefaction of PS/PE mixtures, and a property in the oil are presented in this paper.

Wann, Jyi-Perng A.; Kamo, Tohru; Sato, Yoshiki [National Institute for Resources and Environment, Tsukuba, Ibaraki (Japan)] [and others

1996-12-31

137

Effect of the range of repulsions on the existence of a stable liquid phase  

NASA Astrophysics Data System (ADS)

Experimental and theoretical results have established that the range of the attraction plays a critical role in determining whether a particle system exhibits a stable liquid phase. Changes to the range of the repulsions can similarly affect the existence of a stable liquid phase; however, these effects have not been clearly elucidated. We demonstrate that an increase in the range of repulsions can either enhance or decrease the stability of the liquid phase, depending on the form of the interaction potential. For either case, the critical variable that controls the stability of the liquid phase is the ratio of the representative energies of the liquid and solid phases.

Larsen, Ryan J.; Zukoski, Charles F.

2012-02-01

138

Dynamical behavior near a liquid-liquid phase transition in simulations of supercooled water.  

PubMed

We examine the behavior of the diffusion coefficient of the ST2 model of water over a broad region of the phase diagram via molecular dynamics simulations. The ST2 model has an accessible liquid-liquid transition between low-density and high-density phases, making the model an ideal candidate to explore the impacts of the liquid-liquid transition on dynamics. We locate characteristic dynamical loci in the phase diagram and compare them with the previously investigated thermodynamic loci. The low-density liquid phase shows a crossover from non-Arrhenius to Arrhenius behavior, signaling the onset of a crossover from fragile-to-strong behavior. We explain this crossover in terms of the asymptotic approach of the low-density liquid to a random tetrahedral network and show that the temperature dependence of the diffusion coefficient over a wide temperature range can be simply related to the concentration of defects in the network. Our findings thus confirm that the low-density phase of ST2 water is a well-defined metastable liquid. PMID:21866981

Poole, Peter H; Becker, Stephen R; Sciortino, Francesco; Starr, Francis W

2011-08-26

139

A New Method for Multicomponent Activity Coefficients of Electrolytes in Aqueous Atmospheric Aerosols  

SciTech Connect

Three-dimensional models of atmospheric inorganic aerosols need an accurate yet computationally efficient parameterization of activity coefficients of various electrolytes in multicomponent aqueous solutions. This paper describes the development and application of a new mixing rule for calculating activity coefficients of electrolytes typically found in atmospheric aerosol systems containing H+, NH4+, Na+, Ca2+ SO42-, HSO4-, NO3-, and Cl- ions. The new mixing rule, called MTEM (Multicomponent Taylor Expansion Model), estimates the mean activity coefficient of an electrolyte in a multicomponent solution based on its values in binary solutions of all the electrolytes present in the mixture at the solution water activity aw, assuming aw is equal to the ambient relative humidity. The aerosol water content is calculated using the Zdanovskii-Stokes-Robinson method. For self-consistency, most of the MTEM and Zdanovskii-Stokes-Robinson parameters are derived using the comprehensive Pitzer-Simonson-Clegg model at 298.15 K. MTEM is evaluated for several multicomponent systems representing various continental and marine aerosols, and is contrasted against the mixing rule of Kusik and Meissner and the newer approach of Metzger et al. [2002]. Predictions of MTEM are found to be generally within a factor of 0.8 to 1.25 of the comprehensive Pitzer-Simonson-Clegg model, and are shown to be significantly more accurate than predictions of the other two methods. MTEM also yields a non-iterative solution of the bisulfate ion dissociation in sulfate-rich systems – a major computational advantage over other iterative methods. CPU time requirements of MTEM relative to other methods for sulfate-poor and sulfate-rich systems are also discussed.

Zaveri, Rahul A.; Easter, Richard C.; Wexler, Anthony S.

2005-01-21

140

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

141

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

142

I-131 SPECT activity recovery coefficients with implicit or triple-energy-window scatter correction  

NASA Astrophysics Data System (ADS)

We define a total-activity recovery coefficient, TARC, as the activity within a volume of interest applied to a set of images from single photon emission computed tomography (SPECT) divided by the true activity in that volume. Because of finite camera resolution, recovery-coefficient values are expected to be less than 1 for small objects. In this report, the TARC is measured as a function of volume, background activity and image-acquisition radius of rotation. A set of hollow spheres which vary in volume are filled with a solution of I-131 in water, and placed within a water-filled cylinder having an elliptical cross section. Tomographic-imaging measurements are carried out for two systems. The first utilizes an implicit scatter correction and the second triple-energy-window correction. Both systems employ a reconstructed-counts-to-activity conversion factor which varies with a measured background parameter and with the radius of rotation. Sphere and cylinder outlines are drawn on a CT scan and transferred to the SPECT scan via a 3-D image fusion. As expected, the inverse of the TARC increases as the sphere volume decreases. With implicit scatter correction, the TARC has no systematic dependence on either radius of rotation or background. With triple-energy-window scatter correction, there is an increase in 1//TARC when the radius of rotation is increased by 5cm. This increase ranges from 9% to 25% depending on volume. For all conditions, 1//TARC is fit to a power-law equation as a function of sphere volume. The use of the resultant equations to correct a measured activity for a small volume is outlined. Accuracy of the present relationships for target shapes which are not spherical is not addressed.

Koral, K. F.; Dewaraja, Y.

1999-02-01

143

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

SciTech Connect

The Liquid Phase Methanol (LPMEOW) 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) to produce methanol from coal-derived synthesis gas (syngas). Air Products and Chemicals, Inc. (Air Products) and Eastman Chemical Company (Eastman) formed the Partnership to execute the Demonstration Project. The LPMEOI-P Process Demonstration Unit was built at a site located at the Eastman coal-to-chemicals complex in Kingsport. During this quarter, initial planning and procurement work continued on the seven project sites which have been accepted for participation in the off-site, product-use test program. Approximately 12,000 gallons of fuel-grade methanol (98+ wt% methanol, 4 wt% water) produced during operation on carbon monoxide (CO)-rich syngas at the LPMEOW Demonstration Unit was loaded into trailers and shipped off-site for Mure product-use testing. At one of the projects, three buses have been tested on chemical-grade methanol and on fhel-grade methanol from the LPMEOW Demonstration Project. During the reporting period, planning for a proof-of-concept test run of the Liquid Phase Dimethyl Ether (LPDME~ Process at the Alternative Fuels Development Unit (AFDU) in LaPorte, TX continued. The commercial catalyst manufacturer (Calsicat) has prepared the first batch of dehydration catalyst in large-scale equipment. Air Products will test a sample of this material in the laboratory autoclave. Catalyst activity, as defined by the ratio of the rate constant at any point in time to the rate constant for freshly reduced catalyst (as determined in the laborato~ autoclave), was monitored for the initial extended operation at the lower initial reactor operating temperature of 235oC. At this condition, the decrease in catalyst activity with time from the period 20 December 1997 through 27 January 1998 occurred at a rate of 1.0% per day, which represented a significant improvement over the 3.4Yi per day decline measured during the initial six weeks of operation in April and May of 1997. The deactivation rate also improved from the longer-term rate of 1.6% per day calculated throughout the summer and autumn of 1997.

None

1998-12-21

144

Glass and liquid phase diagram of a polyamorphic monatomic system  

NASA Astrophysics Data System (ADS)

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, PLDA-HDA(T) and PHDA-LDA(T), respectively. In addition, the compression-induced amorphization line, at which the low-pressure crystal (LPC) transforms to HDA, PLPC-HDA(T), is determined. As originally proposed by Poole et al. [Phys. Rev. E 48, 4605 (1993)] simulations suggest that the PLDA-HDA(T) and PHDA-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 PLPC-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 PLDA-HDA(T), PHDA-LDA(T), PLPC-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).

Reisman, Shaina; Giovambattista, Nicolas

2013-02-01

145

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

146

The effect of porosity on distortion of liquid phase sintered tungsten heavy alloys  

Microsoft Academic Search

Porosity effects on distortion during liquid phase sintering were investigated experimentally. W–Ni–Fe alloys with compositions ranging from 78 to 93 wt% tungsten were liquid phase sintered at 1500°C for 30 min. Surprisingly, the results show that porosity has no appreciable effect on distortion. After sintering, similar distortion profiles were obtained for compacts with both high and low green porosities. On

Xiaoping Xu; Anish Upadhyaya; Randall M. German; Ronald G. Iacocca

1999-01-01

147

Deformation of aluminum-copper powder solids during liquid-phase sintering  

Microsoft Academic Search

During sintering with the participation of a liquid phase Al-Cu powder solids experience growth deformation in the first stage and shrinkage in the second. When the copper concentration in the mixture does not exceed the limit of solid-phase solubility at the sintering temperature, powder solids experience only growth; when the liquid phase is preserved during the whole period of sintering,

A. P. Savitskii; G. N. Romanov; L. S. Martsunova

1985-01-01

148

Modification of supports with liquid phases by thermal treatment in a closed system  

Microsoft Academic Search

Diatomaceous earth type supports are modified with a liquid phase, by high-temperature thermal treatment in a closed system. It is shown that the retention characteristics of the support changes by this treatment. The main advantage of this method, as compared with modification in a flow-through system is that liquid phase evaporation and possibility of oxydation during the process can be

N. D. Petsev; G. I. Pekov; M. D. Alexandrova; Chr Dimitrov

1985-01-01

149

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

150

Liquid-phase hydrogenation of cyclohexene on platinum and palladium catalysts  

SciTech Connect

The authors have investigated the kinetics of the liquid-phase hydrogenation of cyclohexene on Pt/C from 16 to 49/degree/C and at 0.2 to 21. MPa and on Pd/C from 35 to 85/degree/C and at 0.09 to 2.1 MPa. The rate of reaction conforms to a kinetic equation previously derived for the dehydrogenation of the benzene ring. Catalysts containing 0.5% Pt or Pd on activated carbon (BAU grade) and not 5% as for the hydrogenation of benzene were used for the kinetic measurements. The rate of hydrogenation was determined with catalyst batches of 0.1 and 02. g when the reaction order with respect to H/sub 2/ was not equal to zero. The yield of the reaction vessel was proportional to the weight of catalyst.

Murzin, D.Yu.; Konyukhov, V.Yu.; Kul'kova, N.V.; Temkin, M.I.

1989-01-01

151

The activity coefficient of cobalt oxide in silica-saturated iron silicate slags  

NASA Astrophysics Data System (ADS)

The solubility of cobalt oxide in silica-saturated iron silicate slags (1.16 to 10.00 wt pct) in equilibrium with cobalt-gold-iron alloys (1.10 to 6.52 wt pct cobalt) and oxygen pressures of 10-9 to 10-10 atm (1 atm = 1.013 x 105 Pa) has been investigated at 1573 K. The activity coefficient of cobalt oxide, ?CoO, has been calculated relative to pure solid cobalt oxide as standard, namely, ?CoO = 0.91 ± 0.09 and a relationship derived between weight percent cobalt in slag, Co (wt pct), oxygen pressure, pO2, and activity of cobalt relative to liquid cobalt, aCo, namely, Co (wt pct) = 1.32 x 106 pO{2/1/2}aCo ± 10 pct Both errors are calculated at the 95 pct confidence level.

Grimsey, Eric J.; Liu, Xuliang

1995-04-01

152

Quantum control of gas-phase and liquid-phase femtochemistry.  

PubMed

Active control of chemical reactions on a microscopic (molecular) level, that is, the selective breaking or making of chemical bonds, is an old dream. However, conventional control agents used in chemical synthesis are macroscopic variables such as temperature, pressure or concentration, which gives no direct access to the quantum-mechanical reaction pathway. In quantum control, by contrast, molecular dynamics are guided with specifically designed light fields. Thus it is possible to efficiently and selectively reach user-defined reaction channels. In the last years, experimental techniques were developed by which many breakthroughs in this field were achieved. Femtosecond laser pulses are manipulated in so-called pulse shapers to generate electric field profiles which are specifically adapted to a given quantum system and control objective. The search for optimal fields is guided by an automated learning loop, which employs direct feedback from experimental output. Thereby quantum control over gas-phase as well as liquid-phase femtochemical processes has become possible. In this review, we first discuss the theoretical and experimental background for many of the recent experiments treated in the literature. Examples from our own research are then used to illustrate several fundamental and practical aspects in gas-phase as well as liquid-phase quantum control. Some additional technological applications and developments are also described, such as the automated optimization of the output from commercial femtosecond laser systems, or the control over the polarization state of light on an ultrashort timescale. The increasing number of successful implementations of adaptive learning techniques points at the great versatility of computer-guided optimization methods. The general approach to active control of light-matter interaction has also applications in many other areas of modern physics and related disciplines. PMID:12785256

Brixner, Tobias; Gerber, Gustav

2003-04-14

153

Liquid phase deposition synthesis of hexagonal molybdenum trioxide thin films  

NASA Astrophysics Data System (ADS)

Hexagonal molybdenum trioxide thin films with good crystallinity and high purity have been fabricated by the liquid phase deposition (LPD) technique using molybdic acid (H2MoO4) dissolved in 2.82% hydrofluoric acid (HF) and H3BO3 as precursors. The crystal was found to belong to a hexagonal hydrate system MoO3.nH2O (n~0.56). The unit cell lattice parameters are a=10.651 Å, c=3.725 Å and V=365.997 Å3. 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 Mo6+ 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 °C, the hexagonal MoO3.nH2O was transformed into the thermodynamically stable orthorhombic phase.

Deki, Shigehito; Béléké, Alexis Bienvenu; Kotani, Yuki; Mizuhata, Minoru

2009-09-01

154

Interpenetration as a mechanism for liquid-liquid phase transitions  

NASA Astrophysics Data System (ADS)

We study simple lattice systems to demonstrate the influence of interpenetrating bond networks on phase behavior. We promote interpenetration by using a Hamiltonian with a weakly repulsive interaction with nearest neighbors and an attractive interaction with second-nearest neighbors. In this way, bond networks will form between second-nearest neighbors, allowing for two (locally) distinct networks to form. We obtain the phase behavior from analytic solution in the mean-field approximation and exact solution on the Bethe lattice. We compare these results with exact numerical results for the phase behavior from grand canonical Monte Carlo simulations on square, cubic, and tetrahedral lattices. All results show that these simple systems exhibit rich phase diagrams with two fluid-fluid critical points and three thermodynamically distinct phases. We also consider including third-nearest-neighbor interactions, which give rise to a phase diagram with four critical points and five thermodynamically distinct phases. Thus the interpenetration mechanism provides a simple route to generate multiple liquid phases in single-component systems, such as hypothesized in water and observed in several model and experimental systems. Additionally, interpenetration of many such networks appears plausible in a recently considered material made from nanoparticles functionalized by single-strands of DNA.

Hsu, Chia Wei; Starr, Francis W.

2009-04-01

155

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

156

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

157

Liquid phase deposition of silica: Thin films, colloids and fullerenes  

NASA Astrophysics Data System (ADS)

Little research has been done to explore liquid phase deposition (LPD) of silica on non-planar substrates. This thesis proves that the seeded growth of silica colloids from fullerene and surfactant micelles is possible via LPD, as is the coating of individual single walled carbon nanotubes (SWNTs) and carbon fibers. Working on the premise that a molecular growth mechanism (versus colloidal/gel deposition) is valid for LPD, nanostructured substrates and specific chemical functional groups should act as "seeds," or templates, for silica growth. Seeded growth is confirmed by reactions of the growth solution with a range of surfactants and with materials with distinctive surface moieties. LPD promises lower production costs and environmental impact as compared to present methods of coating technology, because it is an inherently simple process, using low temperatures and inexpensive air-stable reactants. Silica is ubiquitous in materials science. Its applications range from thixotropic additives for paint to gate dielectrics in the semiconductor industry. Nano-structured coatings and thin films are integral in today's electronics industry and will become more vital as the size of electronics shrinks. With the incorporation of nanoparticles in future devices, the ability to deposit quality coatings with finely tuned properties becomes paramount. The methods developed herein have applications in fabricating insulators for use in the future molecular scale electronics industry. Additionally, these silica nanoparticles have applications as templates for use in photonics and fuel cell membrane production and lend strength and durability to composites.

Whitsitt, Elizabeth A.

158

A new method for multicomponent activity coefficients of electrolytes in aqueous atmospheric aerosols  

NASA Astrophysics Data System (ADS)

Three-dimensional models of atmospheric inorganic aerosols need accurate and computationally efficient parameterizations of activity coefficients of various electrolytes in multicomponent aqueous solutions. In this paper, we extend the Taylor's series expansion mixing rule used by C. Wagner in 1952 for estimating activity coefficients in dilute alloy solutions to aqueous electrolyte solutions at any concentration. The resulting method, called the multicomponent Taylor expansion method (MTEM), estimates the mean activity coefficient of an electrolyte in a multicomponent solution on the basis of its values in binary solutions of all the electrolytes present in the mixture at the solution water activity aw, assuming aw is equal to the ambient relative humidity. MTEM is applied here for atmospheric aerosol systems containing H+, NH4+, Na+, Ca2+, SO42-, HSO4-, NO3-, and Cl- ions. The aerosol water content is calculated using the Zdanovskii-Stokes-Robinson (ZSR) method. For self-consistency, most of the MTEM and ZSR parameters are derived using the comprehensive Pitzer-Simonson-Clegg model at 298.15 K and are valid for an aw range of 0.2-0.97. Because CaSO4 is sparingly soluble, it is treated as a solid in the model over the entire aw range. MTEM is evaluated for several multicomponent systems representing various continental and marine aerosols and is contrasted against the mixing rule of C. L. Kusik and H. P. Meissner and of L. A. Bromley and the newer approach of S. Metzger and colleagues. Predictions of MTEM are found to be generally within a factor of 0.8-1.25 of the comprehensive Pitzer-Simonson-Clegg model and are shown to be significantly more accurate than predictions of the other three methods. MTEM also yields a noniterative solution of the bisulfate ion dissociation in sulfate-rich systems: a major computational advantage over other ionic-strength-based methods that require an iterative solution. CPU time requirements of MTEM relative to other methods for sulfate-poor and sulfate-rich systems are also discussed.

Zaveri, Rahul A.; Easter, Richard C.; Wexler, Anthony S.

2005-01-01

159

Equilibrium partial pressures and mean activity and osmotic coefficients of 0-100% nitric acid as a function of temperature  

Microsoft Academic Search

Rational activity and osmotic coefficients and Henry's law constants K{sub Hx} (for the reaction HNO{sub 3(g)} = H{sup +}{sub (aq)} + NOâ⁻{sub (aq)}), given as functions of temperature, enable p(HâO) and p(HNOâ) to be calculated from -60 to 120°C, 0-100% HNOâ. Apparent molal enthalpies, heat capacities, and activity coefficients (derived from electromotive force (emf), freezing point, and partial pressure data)

Simon L. Clegg; Peter. Brimblecombe

1990-01-01

160

Measurement and correlation of ion activity coefficients in aqueous solutions of mixed electrolyte with a common ion  

Microsoft Academic Search

Ion selective electrodes have been used to measure the activity coefficients at 298.2 K of individual ions in aqueous solutions of mixtures of NaCl and KCl up to 4 molal total chloride ion concentration, and of NaCl and NaBr up to 4 molal total sodium ion concentration. The experimental results show that the activity coefficient of an ion in the

M. K. Khoshkbarchi; J. H. Vera

1996-01-01

161

Structure-activity relationships to estimate the effective Henry's law coefficients of organics of atmospheric interest  

NASA Astrophysics Data System (ADS)

The Henry's law coefficient is a key property needed to address the multiphase behaviour of organics in the atmosphere. Methods that can reliably predict the values for the vast number of organic compounds of atmospheric interest are therefore required. The effective Henry's law coefficient H* in air-water systems at 298 K was compiled from literature for 488 organic compounds bearing functional groups of atmospheric relevance. This data set was used to assess the reliability of the HENRYWIN bond contribution method and the SPARC approach for the determination of H*. Moreover, this data set was used to develop GROMHE, a new Structure Activity Relationship (SAR) based on a group contribution approach. These methods estimate logH* with a Root Mean Square Error (RMSE) of 0.38, 0.61, and 0.73 log unit for GROMHE, SPARC and HENRYWIN respectively. The results show that for all these methods the reliability of the estimates decreases with increasing solubility. The main differences among these methods lie in H* prediction for compounds with H* greater than 103 M atm-1. For these compounds, the predicted values of logH* using GROMHE are more accurate (RMSE=0.53) than the estimates from SPARC or HENRYWIN (RMSE=0.98 and 1.12).

Raventos-Duran, T.; Camredon, M.; Valorso, R.; Aumont, B.

2010-02-01

162

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

163

Experimental study of oxygen diffusion coefficients in clean water containing salt, glucose or surfactant: Consequences on the liquid-side mass transfer coefficients  

Microsoft Academic Search

This present paper proposes new investigations aiming at: (i) studying the effect on oxygen diffusion coefficients of the presence in clean water of some compounds usually encountered in biological media and (ii) quantifying their consequences on liquid-side mass transfer coefficients. The oxygen diffusion coefficients D were firstly measured in various synthetic liquid phases containing either salt (NaCl), sugar (glucose) or

Marupatch Jamnongwong; Karine Loubiere; Nicolas Dietrich; Gilles Hébrard

2010-01-01

164

The activity coefficients of Fe(III) hydroxide complexes in NaCl and NaClO4 solutions  

NASA Astrophysics Data System (ADS)

The osmotic coefficients of FeCl3 at 25 °C from 0.15 to 1.7 m [Rumyantsev et al., Z. Phys. Chem., 218, 1089 1127, 2004] have been used to determine the Pitzer parameters (?(0), ?(1) and C?) for FeCl3. Since the differences in the Pitzer coefficients of rare earths in NaCl and NaClO4 are small, the values of Fe(ClO4)3 have been estimated using the differences between La(ClO4)3 and LaCl3. The Pitzer coefficients for FeCl3 combined with enthalpy and heat capacity data for the rare earths can be used to estimate the activity coefficients of Fe3+ in NaCl over a wide range of temperatures (0 to 50 °C) and ionic strength (0 to 6 m). The activity coefficients of Fe3+ in NaCl and NaClO4 solutions have been used to determine the activity coefficients of Fe(OH)2+ in these solutions from the measured first hydrolysis constants of Fe3+ [Byrne et al., Mar. Chem., 97, 34 48, 2005]. The activity coefficients of Fe(OH)2+, Fe(OH)3 and Fe(OH)4- from 0 to 50 °C have also been determined from the solubility measurements of Fe(III) in NaCl solutions [Liu and Millero, Geochim. Cosmochim Acta, 63, 3487 3497, 1999]. These activity coefficients have been fitted to the Pitzer equations. These results can be used to estimate the speciation of Fe(III) with OH- in natural waters with high concentrations of NaCl from 0 to 50 °C.

Millero, Frank J.; Pierrot, Denis

2007-10-01

165

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.

2013-10-01

166

Activity coefficients and free energies of nonionic mixed surfactant solutions from vapor-pressure and freezing-point osmometry.  

PubMed

The thermodynamic properties of mixed surfactant solutions are widely investigated, prompted by numerous practical applications of these systems and by interest in molecular association and self-organization. General techniques for measuring thermodynamic activities, such as isopiestic equilibration, are well-established for multicomponent solutions. Surprisingly, these techniques have not yet been applied to mixed surfactant solutions, despite the importance of the free energy for micelle stability. In this study, equations are developed for the osmotic coefficients of solutions of nonionic surfactant A + nonionic surfactant B. A mass-action model is used, with virial equations for the activity coefficients of the micelles and free surfactant monomer species. The equations are fitted to osmotic coefficients of aqueous decylsulfobetaine + dodecylsulfobetaine solutions measured by vapor-pressure and freezing-point osmometry. Equilibrium constants for mixed-micelle formation are calculated from the free monomer concentrations at the critical micelle concentrations. The derived activity coefficients of the micelles and free monomers indicate large departures from ideal solution behavior, even for dilute solutions of the surfactants. Stoichiometric activity coefficients of the total surfactant components are evaluated by Gibbs-Duhem integration of the osmotic coefficients. Relatively simple colligative property measurements hold considerable promise for free energy studies of multicomponent surfactant solutions. PMID:21504169

MacNeil, Jennifer A; Ray, Gargi Basu; Leaist, Derek G

2011-04-19

167

Determination of effective mass transfer coefficient ( k c ) of patulin adsorption on activated carbon packed bed columns with recycling  

Microsoft Academic Search

In this study, a simple and effective technique for determining overall mass transfer coefficients in fixed bed sorption columns with recycling is presented. The overall mass transfer coefficient (Kc) of patulin for adsorption on activated carbon packed columns were determined at different flow rates. The Kc values increased from 4.74 × 10?2 to 12.96 × 10?2 cm s?1 when the

Mehmet Mutlu; Vural Gökmen

1998-01-01

168

The effect of chromium on the activity coefficient of sulfur in liquid Fe-Cr-S alloys  

Microsoft Academic Search

The effect of chromium on the activity coefficient of sulfur in the ternary system Fe-Cr-S has been determined in the temperature range 1525° to 1755°C for chromium concentrations of up to 40 wt pct, using a levitation melting technique in H2-H2S atmospheres. The first order free energy interaction coefficient, e {S\\/Cr}, which is derived on the assumption that the thermal

J. G. Dondelinger; D. A. R. Kay; A. McLean

1971-01-01

169

The role of activity coefficients in bioreaction equilibria: thermodynamics of methyl ferulate hydrolysis.  

PubMed

The Gibbs energy of reaction (?(R)g) is the key quantity in the thermodynamic characterization of biological reactions. Its calculation requires precise standard Gibbs energy of reaction (?(R)g(+)) values. The value of ?(R)g(+) is usually determined by measuring the apparent (concentration-dependent) equilibrium constants K, e.g., the molality-based Km. However, the thermodynamically consistent determination of ?(R)g(+) requires the thermodynamic (activity-based) equilibrium constant Ka. These values (Km and Ka) are equal only if the ratio of the activity coefficients of the reactants to the activity coefficients of the products (K?) is equal to unity. In this work, the impact of K? on the estimation of Ka for biological reactions was investigated using methyl ferulate (MF) hydrolysis as a model reaction. The value of K? was experimentally determined from Km values that were measured at different reactant concentrations. Moreover, K? was independently predicted using the thermodynamic model ePC-SAFT. Both the experimentally determined and the predicted K? values indicate that this value cannot be assumed to be unity in the considered reaction. In fact, in the reaction conditions considered in this work, K? was shown to be in the range of 3

Hoffmann, Philip; Voges, Matthias; Held, Christoph; Sadowski, Gabriele

2013-01-11

170

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

171

Growth and Characterization of Liquid Phase Epitaxially Grown Spinel Ferrite Films.  

National Technical Information Service (NTIS)

The characteristics of ferrimagnetic and ferromagnetic materials are reviewed with particular emphasis on the uniaxial magnetic anisotropy which may be presented in liquid phase epitaxy (LPE) grown in spinel ferrite films. The properties of spinel ferrite...

P. J. M. Vanderstraten

1980-01-01

172

Carbide composition change during liquid phase sintering of a wear resistant alloy  

NASA Astrophysics Data System (ADS)

Constitutive liquid phase sintering is used to obtain fully dense parts of powdered STELLITE Alloy No. 6 PM (Co-29Cr-4.5W-l.2C- < 1B) with excellent wear resistance at elevated temperature. This alloy is characterized by a cobalt-rich fcc solid solution and interdendritic carbide phases in the as-atomized state. Compositional changes in the carbides prior to, and during, the liquid phase sintering were investigated via X-ray diffraction, optical microscopy, and Auger electron spectroscopy. The rejection of boron and cobalt by an M23C6-type carbide was identified as leading to the local formation of the liquid phase. A mechanism for the interactive role of the carbide composition change and the constitutive liquid phase sintering is proposed.

McGinn, P. J.; Kumar, P.; Miller, A. E.; Hickl, A. J.

1984-06-01

173

Spin liquid phases for spin-1 systems on the triangular lattice.  

PubMed

Motivated by recent experiments on material Ba3NiSb2O9, we propose two novel spin liquid phases (A and B) for spin-1 systems on a triangular lattice. At the mean field level, both spin liquid phases have gapless fermionic spinon excitations with quadratic band touching; thus, in both phases the spin susceptibility and ?=C(v)/T saturate to a constant at zero temperature, which are consistent with the experimental results on Ba3NiSb2O9. On the lattice scale, these spin liquid phases have Sp(4)~SO(5) gauge fluctuation, while in the long wavelength limit this Sp(4) gauge symmetry is broken down to U(1)×Z(2) in the type A spin liquid phase, and broken down to Z(4) in the type B phase. We also demonstrate that the A phase is the parent state of the ferroquadrupole state, nematic state, and the noncollinear spin density wave state. PMID:22463565

Xu, Cenke; Wang, Fa; Qi, Yang; Balents, Leon; Fisher, Matthew P A

2012-02-23

174

Liquid Phase Migration in Extrusion of Aqueous Alumina Paste for Freeze-Form Extrusion Fabrication  

NASA Astrophysics Data System (ADS)

Freeze-form Extrusion Fabrication (FEF) is an additive manufacturing technique that extrudes highly ceramic loaded aqueous paste along 3D contours for complex ceramic part fabrication. The phenomenon of liquid phase migration (LPM) in paste extrusion process will result in variation of liquid content in paste and consequently problems in processing and non-uniform properties of ceramic parts. It is necessary to understand the LPM phenomenon in FEF process. In this paper, the effect of liquid phase migration on extrusion of aqueous alumina paste was investigated for FEF process. The water content and extrusion force data were collected for a series of ram velocities. According to the extrusion force profiles, the extrusion process can be divided into four stages: compaction stage, transient stage, steady stage and dead zone stage. The results show that ram velocity is the key parameter for occurrence of liquid phase migration phenomenon and there is a velocity threshold above which the liquid phase migration will not happen.

Liu, Hongjun; Leu, Ming C.

175

Numerical simulation of grain size distributions in liquid phase sintered materials.  

National Technical Information Service (NTIS)

Many technologically important ceramics such as silicon nitride ceramics, alumina substrates and barium titanate electrical capacitors are liquid phase sintered. It is important to understand evolution of microstructural features generated by processes su...

V. Tikare J. D. Cawley

1995-01-01

176

Spin liquid phases of alkaline-earth-metal atoms at finite temperature  

NASA Astrophysics Data System (ADS)

We study spin liquid phases of spin-5/2 alkaline-earth-metal atoms on a honeycomb lattice at finite temperatures. Our analysis is based on a Gutzwiller projection variational approach recast to a path-integral formalism. In the framework of a saddle-point approximation we determine spin liquid phases with lowest free energy and study their temperature dependence. We identify a critical temperature, where all the spin liquid phases melt and the system goes to the paramagnetic phase. We also study the stability of the saddle-point solutions and show that a time-reversal symmetry breaking state, a so-called chiral spin liquid phase, is realized even at finite temperatures. We also determine the spin structure factor, which, in principle, is an experimentally measurable quantity and is the basic tool to map the spectrum of elementary excitations of the system.

Sinkovicz, P.; Zamora, A.; Szirmai, E.; Lewenstein, M.; Szirmai, G.

2013-10-01

177

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

178

PdC4a. The active control of sound reflection\\/transmission coefficients using piezoelectric composite materials  

Microsoft Academic Search

An active noise control device has been fabricated using a 0–3 piezo-composite sensor and actuator. This device has been used with a fast feedback electronic system. The reflection and transmission coefficients have been measured in a pulse tube. The energy was reduced by up to 0. 5 in active noise reduction mode and increased by up to 0. 17 in

A. J Salloway; R. C Twiney; R. W Whatmore

1992-01-01

179

Characteristics of densification and distortion of Ni–Cu liquid-phase sintered tungsten heavy alloy  

Microsoft Academic Search

The characteristics of densification and distortion of a 80W–14Ni–6Cu alloy during liquid-phase sintering (LPS) were investigated in relation to the liquid-phase formation. By means of differential thermal analysis (DTA), the melting process of the Ni–Cu matrix in a die-pressed compact was examined and compared with that in a loose powder mixture. It was revealed that enhanced inter-diffusion and in situ

Yunxin Wu; Randall M German; Brian Marx; Ravi Bollina; Matt Bell

2003-01-01

180

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

181

Solution crystallisation via a submerged liquid-liquid phase boundary: oiling out.  

PubMed

In many situations the process of crystallisation from solution is known to occur via metastable crystalline states (polymorphs or solvates). Here we present what we believe to be a novel example of small molecule crystallisation in which the initial separation of a solute rich liquid phase precedes the crystallisation event. We believe this occurs because a submerged liquid-liquid phase boundary is accessible within the metastable zone of the crystal nucleation process. PMID:12703779

Bonnett, P E; Carpenter, K J; Dawson, S; Davey, R J

2003-03-21

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.

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

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. 4 figs.

Raj, R.; Baik, S.

1985-11-12

184

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

185

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

186

Relationships between water attenuation coefficients derived from active and passive remote sensing: a case study from two coastal environments.  

PubMed

Relationships between the satellite-derived diffuse attenuation coefficient of downwelling irradiance (K(d)) and airborne-based vertical attenuation of lidar volume backscattering (?) were examined in two coastal environments. At 1.1 km resolution and a wavelength of 532 nm, we found a greater connection between ? and K(d) when ? was computed below 2 m depth (Spearman rank correlation coefficient up to 0.96), and a larger contribution of K(d) to ? with respect to the beam attenuation coefficient as estimated from lidar measurements and K(d) models. Our results suggest that concurrent passive and active optical measurements can be used to estimate total scattering coefficient and backscattering efficiency in waters without optical vertical structure. PMID:21691366

Montes, Martin A; Churnside, James; Lee, Zhongping; Gould, Richard; Arnone, Robert; Weidemann, Alan

2011-06-20

187

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

1999-04-01

188

Thermodynamic and kinetic studies of the liquid phase synthesis of tert-butyl ethyl ether using a reaction calorimeter  

SciTech Connect

The liquid-phase addition of ethanol to isobutene to give tert-butyl ethyl ether (ETBE) on the ion-exchange resin Lewatit K2631 has been studied in a calorimetric reactor. The heat capacity of ETBE and the enthalpy change of the ETBE synthesis reaction in the temperature range 312--333 K have been determined. ETBE heat capacity in the liquid phase has been found to follow the equation C{sub p} = 486.73 {minus} 2.253 (T/K) + 0.00479 (T/K){sup 2}. At 298 K the standard molar reaction enthalpy is {Delta}H{degree} = {minus}32.0 kJ/mol. A determination of the apparent activation energy of 86.5--89.2 kJ/mol has been performed graphically from the plots of heat flow rate versus time. An Eley-Rideal mechanism, with two active sites involved in the rate determining step, has been proved to be correct. From this model an apparent activation energy of 80.6 kJ/mol is deduced. A {minus}3.0 kJ/mol value has been found for the adsorption enthalpy of ethanol. This allows the estimation of the actual gel-phase activation energy of 77.6 kJ/mol.

Sola, L.; Pericas, M.A.; Cunill, F.; Tejero, J. [Univ. de Barcelona (Spain)

1995-11-01

189

Determination of water permeability coefficient and its activation energy for rabbit spermatozoa.  

PubMed

Critical tonicity (tonicity at which 50% of cells swell beyond their maximum volume-to-surface area ratio and lyse) of rabbit spermatozoa was measured as 45.6 mOsm at 22 degrees C. To determine the temperature effect on critical tonicity, cells were equilibrated to 15, 25, and 35 degrees C and critical tonicity was measured as 52.9, 42.2, and 32.4 mOsm, respectively. The time taken for rabbit sperm to achieve lysis at these temperatures was measured by exposing cells for increasing times to distilled water. From these results values for the permeability coefficient of rabbit spermatozoa to water (Lp) and its activation energy (Ea) were calculated. At 25 degrees C, Lp was 0.63 micron/min/atm and was clearly temperature dependent; Ea was 17.8 kcal/mol. Rabbit spermatozoa appear to have a low Lp and high Ea, the opposite of the situation seen with spermatozoa from all other species examined to date which have high Lp and low Ea. Nevertheless, the values obtained permit modeling of cooling rates for cell survival during cryopreservation in keeping with cooling rates commonly employed. PMID:7743819

Curry, M R; Redding, B J; Watson, P F

1995-04-01

190

Evaluated activity and osmotic coefficients for aqueous solutions: thirty-six uni-bivalent electrolytes  

Microsoft Academic Search

A critical evaluation of the mean acivity and osmotic coefficients in aqueous solutions of thirty-five uni-bivalent electrolytes at 298.15 K is presented. The systems which have been treated are ammonium orthophosphate, guanadinium carbonate, 1,2-ethane disulfonic acid, m-benzene disulfonic acid, ammonium decahydroborate, and the unibivalent compounds of lithium, sodium, potasium, rubidium, and cesium. Osmotic coefficients were calculated from direct vapor pressure

R. N. Goldberg

1981-01-01

191

Trace determination of triclosan and triclocarban in environmental water samples with ionic liquid dispersive liquid-phase microextraction prior to HPLC-ESI-MS-MS.  

PubMed

A novel and environmentally friendly microextraction method, termed ionic liquid dispersive liquid-phase microextraction (IL-DLPME), has been developed for rapid enrichment of triclosan and triclocarban before analysis by high-performance liquid phase chromatography-electrospray tandem mass spectrometry (HPLC-ESI-MS-MS). Instead of using toxic organic solvents, an ionic liquid was used as a green extraction solvent. This also avoided the instability of the suspending drop in single-drop liquid-phase microextraction, and the heating and cooling step in temperature-controlled ionic liquid dispersive liquid phase microextraction. Factors that may affect the enrichment efficiency, for example volume of ionic liquid, type and volume of dispersive solvent, pH, extraction time, and NaCl content were investigated in detail and optimized. Under optimum conditions, linearity of the method was observed over the range 0.2-12 microg L(-1) for triclocarban and 1-60 microg L(-1) for triclosan with correlation coefficients ranging from 0.9980 to 0.9990, respectively. The sensitivity of the proposed method was found to be excellent, with limits of detection in the range 0.040-0.58 microg L(-1) and precision in the range 7.0-8.8% (RSD, n = 5). This method has been successfully used to analyze real environmental water samples and satisfactory results were achieved. Average recoveries of spiked compounds were in the range 70.0-103.5%. All these results indicated that the developed method would be a green method for rapid determination of triclosan and triclocarban at trace levels in environmental water samples. PMID:20379811

Zhao, Ru-Song; Wang, Xia; Sun, Jing; Wang, Shan-Shan; Yuan, Jin-Peng; Wang, Xi-Kui

2010-04-09

192

Methodology for using prompt gamma activation analysis to measure the binary diffusion coefficient of a gas in a porous medium  

NASA Astrophysics Data System (ADS)

Diffusion plays a critical role in determining the rate at which gases migrate through porous systems. Accurate estimates of diffusion coefficients are essential if gas transport is to be accurately modeled and better techniques are needed that can be used to measure these coefficients non-invasively. Here we present a novel method for using prompt gamma activation analysis to determine the binary diffusion coefficients of a gas in a porous system. Argon diffusion experiments were conducted in a 1 m long, 10 cm diameter, horizontal column packed with a SiO2 sand. The temporal variation of argon concentration within the system was measured using prompt gamma activation analysis. The binary diffusion coefficient was obtained by comparing the experimental data with the predictions from a numerical model in which the diffusion coefficient was varied until the sum of square errors between experiment and model data was minimized. Predictions of argon concentration using the optimal diffusivity fit experimental measurements with an R2 of 0.983.

Rios Perez, Carlos A.; Biegalski, Steve R.; Deinert, Mark R.

2012-12-01

193

Mass transfer resistance in a liquid-phase microextraction employing a single hollow fiber under unsteady-state conditions.  

PubMed

In this study, the mass transport resistance in liquid-phase microextraction (LPME) in a single hollow fiber was investigated. A mathematical model has been developed for the determination of the overall mass transfer coefficient based on the acceptor phase in an unsteady state. The overall mass transfer coefficient in LPME in a single hollow fiber has been estimated from time-dependent concentration of extracted analyte in the acceptor phase while maintaining a constant analyte concentration in the donor phase. It can be achieved either using a high volume of donor to acceptor phase ratio or tuning the extraction conditions to obtain a low-enrichment factor, so that the analyte concentration in the sample is not significantly influenced by the mass transfer. Two extraction systems have been used to test experimentally the developed model: the extraction of Lu(III) from a buffer solution and the extraction of three local anesthetics from a buffer or plasma solution. The mass transfer resistance, defined as a reciprocal values of the mass transfer coefficient, was found to be 1.2 × 10(3) cm(-1) min for Lu(III) under optimal conditions and from 1.96 to 3.3 × 10(3) cm(-1) min for the local anesthetics depending on the acceptor pH and the hydrophobicity of the drug. PMID:22997029

Kumri?, Ksenija R; Vladisavljevi?, Goran T; ?or?evi?, Jelena S; Jönsson, Jan Åke; Trti?-Petrovi?, Tatjana M

2012-09-01

194

COMPUTATIONAL CHEMISTRY METHOD FOR PREDICTING VAPOR PRESSURES AND ACTIVITY COEFFICIENTS OF POLAR ORGANIC OXYGENATES IN PM2.5  

EPA Science Inventory

Parameterizations of interactions of polar multifunctional organic oxygenates in PM2.5 must be included in aerosol chemistry models for evaluating control strategies for reducing ambient concentrations of PM2.5 compounds. Vapor pressures and activity coefficients of these compo...

195

Methodologies for measurement and application of distribution coefficient.  

National Technical Information Service (NTIS)

The distribution coefficient, as an equilibrium parameter, which defines partitioning of a solute between a solid and liquid phase, is commonly used in safety assessment of nuclear waste disposal ; e.q., in (1) analysis of the release behavior of radionuc...

S. Uchida H. Yasuda Y. Mahara N. Sasaki T. Takahashi

1995-01-01

196

Enhancement of mass transfer coefficients in spiral films  

Microsoft Academic Search

The wetted columns both with tangential nozzles and turbulence promoters are of great interest. The spiral motion of a liquid film gives a good stability and a great turbulence to the film. It results in the increase of the rate of transfer processes compared with those both in smooth and rough wall columns. The liquid phase mass transfer coefficients for

1997-01-01

197

Determination of liquid–liquid partition coefficients by separation methods  

Microsoft Academic Search

By essence, all kinds of chromatographic methods use the partitioning of solutes between a stationary and a mobile phase to separate them. Not surprisingly, separation methods are useful to determine accurately the liquid–liquid distribution constants, commonly called partition coefficient. After briefly recalling the thermodynamics of the partitioning of solutes between two liquid phases, the review lists the different methods of

A. Berthod; S. Carda-Broch

2004-01-01

198

Characterization of liquid phase epitaxial GaAs forblocked-impurity-band far-infrared detectors  

SciTech Connect

GaAs Blocked-Impurity-Band (BIB) photoconductor detectors have the potential to become the most sensitive, low noise detectors in the far-infrared below 45.5 cm{sup -1} (220 {micro}m). We have studied the characteristics of liquid phase epitaxial GaAs films relevant to BIB production, including impurity band formation and the infrared absorption of the active section of the device. Knowledge of the far-infrared absorption spectrum as a function of donor concentration combined with variable temperature Hall effect and resistivity studies leads us to conclude that the optimal concentration for the absorbing layer of a GaAs BIB detector lies between 1 x 10{sup 15} and 6.7 x 10{sup 15} cm{sup -3}. At these concentrations there is significant wavefunction overlap which in turn leads to absorption beyond the 1s ground to 2p bound excited state transition of 35.5 cm{sup -1} (282 {micro}m). There still remains a gap between the upper edge of the donor band and the bottom of the conduction band, a necessity for proper BIB detector operation.

Cardozo, B.L.; Reichertz, L.A.; Beeman, J.W.; Haller, E.E.

2004-04-07

199

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

200

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

201

Activity coefficients of lithium dilute in binary alloys: measurements and calculations. [Al-Sn; Tl-Bi; Bi-Pb  

SciTech Connect

Electromotive force measurements of the activity of lithium dilute in three binary solvents (Al-Sn, Tl-Bi, and Bi-Pb) have been carried out at constant temperature. The variations of the activity coefficients of Li as a function of the composition of the solvent are analyzed in terms of three different models, the quasi-chemical theory, the Wagner model, and the coordination cluster theory. This last model appears to provide an excellent interpretation of the experimental results. 4 figures.

Saboungi, M.L.; Marr, J.; Spineto, S.

1981-01-01

202

Enhanced kinetics of pseudo first-order hydrolysis in liquid phase coexistent with ice.  

PubMed

The reaction rate of the hydrolysis of fluorescein diacetate (FDA) is several times larger in the frozen state than that in the unfrozen solution of the same composition at the same temperature. The freeze concentration of reactants in the liquid phase expelled form ice crystals cannot explain the kinetic enhancement of pseudo first order reactions such as the FDA hydrolysis. However, the reaction rate increases as the freeze concentration ratio becomes larger at a constant temperature. Direct pH measurements have revealed that the basicity of the liquid phase is unchanged at any concentration ratio, suggesting that the reactivity enhancement is not caused by increased basicity. The reaction rate enhancement is clearly related to the size of the space in which the liquid phase is confined upon freezing. The ice wall itself or the water structure formed near the wall should thus be responsible for this kinetic enhancement. PMID:24063609

Anzo, Kenji; Harada, Makoto; Okada, Tetsuo

2013-10-03

203

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

204

Oiling out or molten hydrate-liquid-liquid phase separation in the system vanillin-water.  

PubMed

Vanillin crystals in a saturated aqueous solution disappear and a second liquid phase emerges when the temperature is raised above 51 degrees C. The phenomenon has been investigated with crystallization and equilibration experiments, using DSC, TGA, XRD and hot-stage microscopy for analysis. The new liquid solidifies on cooling, appears to melt at 51 degrees C, and has a composition corresponding to a dihydrate. However, no solid hydrate can be detected by XRD, and it is shown that the true explanation is that a liquid-liquid phase separation occurs above 51 degrees C where the vanillin-rich phase has a composition close to a dihydrate. To our knowledge, liquid-liquid phase separation has not previously been reported for the system vanillin-water, even though thousands of tonnes of vanillin are produced globally every year. PMID:17497737

Svärd, Michael; Gracin, Sandra; Rasmuson, Ake C

2007-09-01

205

Gravitational effects on compact shaping and microstructure during liquid-phase sintering  

NASA Astrophysics Data System (ADS)

Liquid-phase sintering is routinely used to consolidate dense components. However, there are several problems during liquidphase sintering that have their origin in gravitational effects. Under terrestrial conditions, this technique is generally limited to high solid contents to ensure structural stability and net-shaping. In addition, there are several unresolved issues pertaining to microstructural evolution and compact reshaping during sintering. Experimental conditions present during microgravity processing have allowed liquid-phase sintering over a wider range of solid-liquid ratios than is possible on Earth. A rare opportunity was provided to conduct extensive liquid-phase-sintering experiments on tungsten heavy alloys aboard the space shuttle Columbia as part of the International Microgravity Lab and Microgravity Space Lab. Early results from these experiments show novel behavior associated with microgravity both in microstructural and macrostructural evolution.

Upadhyaya, Anish; Iacocca, Ronald G.; German, Randall M.

1999-04-01

206

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

207

Catalytic performance of Preyssler heteropolyacid, [NaP 5W 30O 110] 14? in liquid phase alkylation of phenol with 1-octene  

Microsoft Academic Search

Under mild conditions a liquid phase alkylation of phenol with 1-octene was studied in the presence of Preyssler catalyst, H14[NaP5W30O110]. This polyanion with high hydrolytic stability (pH 0–12), thermal stability and high acidic strength shows great activity. The effects of various parameters on the yield of product, including catalyst type, reactant molar ratio, solvent type and reaction time were studied.

Rahim Hekmatshoar; Majid M. Heravi; Sodeh Sadjadi; Hossein A. Oskooie; Fatemeh F. Bamoharram

2008-01-01

208

Pressureless Reaction Sintering of AlON using Aluminum Orthophosphate as a Transient Liquid Phase  

SciTech Connect

Use of aluminum oxynitride (AlON) in transparent armor systems has been difficult due to the expense and limitations of the processing methods currently necessary to achieve transparency. Development of a pressureless processing method based on direct reaction sintering of alumina and aluminum nitride powders would reduce costs and provide a more flexible and practical manufacturing method. It may be possible to develop such a processing method using liquid phase sintering; as long as the liquid phase does not remain in the final sample. AlPO4 forms a liquid phase with Al2O3 and AlN at the temperatures required to sinter AlON, and slowly decomposes into P2O5 and alumina. Therefore, it was investigated as a possible transient liquid phase for reaction-sintered AlON. Small compacts of alumina and aluminum nitride with up to of 15wt% AlPO4 additive were pressed and sintered. It was found that AlPO4 formed the requisite transient liquid phase, and it was possible to adjust the process to produce AlON samples with good transmission and densities of 3.66-3.67 g/cc. XRD confirmed the samples formed were AlON, with no trace of any remaining phosphate phases or excess alumina or aluminum nitride. Based on the results, it was concluded that AlPO4 could be utilized as a transient liquid phase to improve the density and transmission of AlON produced by pressureless reaction sintering.

Michael Bakas; Henry Chu

2009-01-01

209

Microstructure manipulations to attain densification without distortion during liquid phase sintering  

NASA Astrophysics Data System (ADS)

Liquid phase sintering provides a means for net-shape manufacturing, but there is a common concern about shape distortion during densification. In the present work, a theory is created to achieve densification without distortion by manipulating microstructure and its evolution during sintering. The microstructure parameters considered in this study are solid volume fraction, dihedral angle, green porosity, and green pore size. These parameters were varied to measure densification and distortion behavior during liquid phase sintering using W-Ni-Cu alloys. Green compacts were formed using ethylene-bis-stearamide as a pore-forming agent with the amount of polymer controlling the initial porosity. Different initial pore sizes were generated by varying the polymer particle size. Dihedral angle was varied by changing the Ni:Cu ratio in the alloys. Finally, the solid volume fraction was adjusted via the tungsten content. Dilatometry was employed to measure shrinkage and shrinkage rate during heating. Distortion was quantified using final compact profiles determined with a coordinate measuring machine to calculate a distortion parameter. Sintering results showed that solid volume fraction and dihedral angle are dominant factors on densification and distortion during liquid phase sintering. Distortion decreased with increasing solid volume fraction and dihedral angle, both contributing to a higher solid contiguity. Densification decreased with increasing green porosity and pore size, while initial pore structure did not show observable effects on distortion in situations of fast densification where full density is achieved. Real time video imaging and quenching results verified that densification and distortion are sequential events in liquid phase sintering with densification occurring first. In gravity, distortion is inhibited until pores are closed and the compact is nearly fully densified. Based on the experimental results, some processing strategies emerge that achieve densification and prevent distortion in liquid phase sintering. Microgravity experiments are proposed for further understanding of microstructure effects on densification and distortion in liquid phase sintering.

Yi, Wuwen

210

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

211

Solid-liquid phase diagrams of binary aromatic hydrocarbon mixtures from calorimetric studies  

SciTech Connect

The authors describe solid-liquid phase diagrams of binary mixtures of aromatic hydrocarbons obtained from calorimetric studies. The sample of the binary solid mixture is heated at a constant rate until the solid is completely melted. During that process, the heat flux needed is monitored. By examination of the curves of the heat flux versus temperature, the solid-liquid phase diagrams can be constructed. Three binary systems (fluorene-dibenzofuran, dibenzothiophene-dibenzofuran, fluorene-dibenzothiophene) have been studied. It turns out that the fluorene-dibenzofuran system forms a solid solution at any composition, while dibenzothiphene-dibenzofuran and fluorene-dibenzothiophene systems have immiscibility gaps in the solid phases.

Sediawan, W.B.; Gupta, S.; McLaughlin, E. (Louisiana State Univ., Baton Rouge, LA (USA). Dept. of Chemical Engineering)

1989-04-01

212

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

213

Gas chromatographic measurements of activity coefficients at infinite dilution for refrigerants with a polyol ester oil as a stationary phase  

Microsoft Academic Search

Activity coefficients at infinite dilution have been measured by gas chromatography for 14 refrigerants (R12, R22, R32, R124, R125, R134a, R142b, R143a, RE170, R236ea, R290, R600, R600a, and R236fa) as solutes, using a polyol ester oil (POE), EMKARATE by ICI, as a stationary phase (solvent). Instrumental analysis (NMR, IR) showed that the main components of the oil are pentaerithritol esters

Roman Stryjek; Sergio Bobbo; Roberto Camporese; Claudio Zilio

1999-01-01

214

Activity coefficients of dilute solutions of lithium in liquid aluminum--tin alloys: electromotive force measurements and interpretation  

Microsoft Academic Search

The activity coefficients of Li solutions dilute in the binary alloy Al--Sn were determined from emf measurements. At T = 949°K, dilute solutions of Li in pure liquid Al and in pure liquid Sn follow the Nernst law. The data provide an independent and accurate evaluation of the limiting excess chemical potentials of Li in Al and in Sn, ..mu..\\/sup

Marie-Louise Saboungi; M. Blander

1977-01-01

215

Prediction of solubilities of pharmaceutical compounds in water + co-solvent systems using an activity coefficient model  

Microsoft Academic Search

The prediction of the solubilities of pharmaceutical compounds in solvent and co-solvent systems can be achieved using a one-parameter Wilson activity coefficient model. The pharmaceutical compounds tested included salicylic acid, acetaminophen, benzocaine, acetanilide and phenacetin. The solvent employed was water, and the co-solvents studied were ethanol, methanol, and 1,4-dioxane. The solubilities of solutes in a binary mixture of water and

Hiroyuki Matsuda; Kenta Kaburagi; Kiyofumi Kurihara; Katsumi Tochigi; Kazuo Tomono

2010-01-01

216

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

Microsoft Academic Search

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

Tom B. Bechtel; Truman S. Storvick

1999-01-01

217

Activity coefficients at infinite dilution measurements for organic solutes and water in the ionic liquid 1-ethyl-3-methylimidazolium tetracyanoborate  

Microsoft Academic Search

The activity coefficients at infinite dilution, ?13?, for 36 solutes, including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, thiophene, tetrahydrofuran, ethers, acetone, and water, in the ionic liquid 1-ethyl-3-methylimidazolium tetracyanoborate, [EMIM][TCB], were determined by gas–liquid chromatography at temperatures from 298.15K to 358.15K. These values are compared to those previously published for selected solutes in the same ionic liquid. The values

Urszula Doma?ska; Marta Królikowska; William E. Acree; Gary A. Baker

2011-01-01

218

Measurement of infinite-dilution activity coefficients of alcohols in water using relative gas-liquid chromatographic method  

Microsoft Academic Search

Infinite-dilution activity coefficients of n-alcohols (C1-C8) in water were measured by using the relative gas-liquid chromatographic method proposed by Orbey and Sandler [1991]. The\\u000a temperature range of measurement was 298 to 343 K. The g ?? values at 298.15 K varied from 1.72 (methanol) to 1970 (n-heptanol). ASOG, UNIFAC, modified UNIFAC (Dortmund), modified UNIFAC\\u000a (Lyngby) group contribution methods could predict

Katsumi Tochigi; Masanori Uchiyama; Kazuo Kojima

2000-01-01

219

Activity coefficients at infinite dilution measurements for organic solutes and water in the ionic liquid triethylsulphonium bis(trifluoromethylsulfonyl)imide  

Microsoft Academic Search

The activity coefficients at infinite dilution, ?13? for 32 solutes: alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, thiophene, tetrahydrofuran, tert-butyl methyl ether, and water in the ionic liquid triethylsulphonium bis(trifluoromethylsulfonyl)imide [Et3S][NTf2] were determined by gas–liquid chromatography at the temperatures from T=298.15K to T=368.15K. The partial molar excess enthalpies at infinite dilution values ?H1E,? were calculated from the experimental ?13? values

Urszula Doma?ska; Andrzej Marciniak

2009-01-01

220

The activity coefficient of high density systems with hard-sphere interactions: the application of the IGCMC method  

Microsoft Academic Search

The inverse grand-canonical Monte Carlo (IGCMC) technique is used to calculate the activity coefficients of the following hard-sphere systems: one-component fluid, binary mixture and solvent primitive model (SPM) electrolyte. The calculations for a one-component fluid are performed at different densities. The components of a binary mixture differ in diameters (300 and 500 pm) with the results being presented for different density

S. Lamperski; M. P?uciennik

2010-01-01

221

Temperature dependence of adsorption coefficients of 222Rn on activated charcoal determined by adsorption-desorption method.  

PubMed

Adsorption coefficients of 222Rn on five activated charcoal were determined (at -21, +7 and +26 degrees C) by an adsorption-desorption technique using a radon source and an Erlenmeyer flask. They varied from 1.1 to 41.2 L x g(-1). From this variation the mean heat of adsorption of radon on our charcoal was calculated as equal to 4,630(50) cal/mole. PMID:11197467

Zikovsky, L

2001-02-01

222

Modeling ATP protonation and activity coefficients in NaCl aq and KCl aq by SIT and Pitzer equations  

Microsoft Academic Search

The acid–base properties of Adenosine 5?-triphosphate (ATP) in NaCl and KCl aqueous solutions at different ionic strengths (0activity isopiestic coefficients was performed, together with new potentiometric measurements (by ISE-H+, glass electrode). Both literature and new

Concetta De Stefano; Demetrio Milea; Alberto Pettignano; Silvio Sammartano

2006-01-01

223

Gas chromatographic measurements of activity coefficients at infinite dilution for refrigerants with a polyol ester oil as a stationary phase  

SciTech Connect

Activity coefficients at infinite dilution have been measured by gas chromatography for 14 refrigerants (R12, R22, R32, R124, R125, R134a, R142b, R143a, RE170, R236ea, R290, R600, R600a, and R236fa) as solutes, using a polyol ester oil (POE), EMKARATE by ICI, as a stationary phase (solvent). Instrumental analysis (NMR, IR) showed that the main components of the oil are pentaerithritol esters of carboxylic acids, and electrospray ionization spectrometry revealed an average molecular mass of the POE of 618 g/mol. The measurements were performed within a temperature range of 244 K to 313 K, but a specific temperature range for each refrigerant was adopted depending on its retention data. The experimental findings are well-represented by the equation: ln {gamma}{sub i}{sup {infinity}} = a{sub i} {minus} b{sub i}/T. Some refrigerants, i.e., R22, R124, R125, R236ea, and R236fa, show quite a considerable positive temperature dependence of their activity coefficients at infinite dilution, which can be attributed to hydrogen bonding with the POE, unlike other refrigerants that show a small, either positive or negative temperature dependence. To the authors` knowledge, there are no data in the literature on activity coefficients at infinite dilution for refrigerant and oil (lubricant) systems, and details on the solubility of refrigerants in oils are also extremely scarce.

Stryjek, R. [Polish Academy of Sciences, Warsaw (Poland). Inst. of Physical Chemistry; Bobbo, S.; Camporese, R. [National Research Council, Padova (Italy). Inst. of Refrigeration; Zilio, C. [Univ. di Padova (Italy). Dept. di Fisica Tecnica

1999-05-01

224

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

SciTech Connect

The Liquid Phase Methanol (LPMEOW) 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) to produce methanol from coal-derived synthesis gas (syngas). Air Products and Chemicals, Inc. (Air Products) and Eastman Chemical Company (Eastman) formed the Partnership to execute the Demonstration Project. The LPMEOW Process Demonstration Unit was built at a site located at the Eastman complex in Kingsport. During this quarter, initial planning and procurement work began on the seven project sites which have been accepted for participation in the off-site, methanol product-use test plan. Two of the projects have begun pre-testing of equipment and three other projects have commenced with equipment procurement, Methanol produced from carbon monoxide (CO)- rich syngas at the Alternative Fuels Development Unit (AFDU) in LaPorte, TX has been shipped to four of the project sites in anticipation of the start of testing during the first quarter of calendar year 1998. Catalyst activity, as defined by the ratio of the rate constant at any point in time to the rate constant for a freshly reduced catalyst (as determined in the laboratory autoclave), continued to decline more rapidly than expected. In response to concentrations of arsenic and sulfbr detected on catalyst samples from the LPMEOW Reactor, Eastman replaced both the arsine- and sulfiwremoval material in the Eastman guard bed which treats the primary syngas feed stream (&danced Gas) prior to its introduction into both the Eastman fixed-bed methanol plant and the LPMEOWM Demonstration Unit. After restarting the demonstration unit, the catalyst deactivation rate remained essentially unchanged. Parallel testing in the laboratory using arsine-doped, and subsequently arsine- and SuIfi-doped syngas, ako ftiIed to prove that arsine was responsible for the higher-than-expected rate of catalyst deactivation in the demonstration unit. Based on the results of plant operation and catalyst sampling, DOE accepted a recommendation by Air Products and Eastman to drain the initial charge of catalyst from the reactor and replace the charge with fresh catalyst. Prior to this catalyst turnaround, a final test was performed to determine the impact of raising the operating temperature of the LPMEOW Reactor from 250"C to 260oC. carbon. Activation of the new flesh charge of catalyst began on 13 November 1997. Just as in the original start-up in April of 1997, only a partial charge of catalyst (20,700 pounds) was activated to limit the amount of material exposed to poisons at the outset. An attempted restart of the LPMEOW Demonstration Unit on 26 November 1997 was unsuccessfid; settling of the flesh catalyst appeared to have occurred in the LPMEOFP Reactor and gas inlet piping, which resulted in the plugging of the gas sparger at the bottom of the vessel.

None

1998-12-21

225

High power RF test of liquid phase shifter for KSTAR tokamak  

Microsoft Academic Search

Summary form only given. A liquid phase shifter is developed for long pulse and high power operation of the KSTAR ICRF heating system. A conventional phase shifter (trombone type) uses sliding contact and it often causes some problem due to local temperature increase and insulation breakdown for long pulse operation under high power. To solve such problems, a phase shifter

J. S. Yoon; Y. D. Bae; J. G. Kwak; B. G. Hong

2003-01-01

226

On the Numerical Solution of Continuum Mixture Model Equations Describing Binary Solid-Liquid Phase Change  

Microsoft Academic Search

This paper deals with some numerical aspects of the solution of continuum mixture model equations for analyzing solid-liquid phase change problems involving binary materials. It is found that the procedure used for iteratively updating the solid fraction with temperature has an important bearing on the convergence behavior of the overall method; here, based on our previous work, we present one

C. Prakash; V. Voller

1989-01-01

227

Liquid-phase sintering of very fine tungsten-copper powder mixtures  

Microsoft Academic Search

The sintering of tungsten-copper powder mixtures of low copper content can be intensified by employing tungsten powders of submicron particle size. The process of liquid-phase sintering of very fine tungsten-copper powder mixtures can be quantitatively described within the framework of the theory of local heterogeneous deformation of a polycrystalline solid with allowance for diffusional grain shape accommodation.

V. V. Panichkina; M. M. Sirotyuk; V. V. Skorokhod

1982-01-01

228

Planar velocity measurements of the gas and liquid phase in dense sprays by flow tagging  

Microsoft Academic Search

We report on measurements of the gas and liquid phase velocity in dense automotive direct injection sprays by 2D laser-based flow tagging. Velocity measurements in dense sprays are generally difficult with conventional techniques because of the high number densities of droplets, the optical thickness of the medium, and multiple light scattering effects. The present flow tagging experiments are based on

S. Krüger; G. Grünefeld; S. Arndt; Robert Bosch; W. Hentschel; Volkswagen AG

229

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

230

Patterns of three-liquid-phase behavior illustated by alcohol-hydrocarbon-water-salt mixtures  

Microsoft Academic Search

Ten salts were each dissolved in water and the solutions mixed with equal volumes of one of six hydrocarbons and one of ten monohydric alcohols. The resulting multiphase mixtures were examined for the number of coexisting liquid phases and, in some cases, for the partitioning of alcohol among them. Several unusual patterns of phase behavior have been observed. For example,

B. M. Knickerbocker; C. V. Pesheck; H. T. Davis; L. E. Scriven

1982-01-01

231

Mechanical properties of molybdenum alloyed liquid phase-sintered tungsten-based composites  

Microsoft Academic Search

Tungsten-based composites are fabricated from mixed elemental powders using liquid phase sintering, usually with a nickel-iron matrix. During sintering, the tungsten undergoes grain growth, leading to microstructure coarsening that lowers strength but increases ductility. Often the desire is to increase strength at the sacrifice of ductility, and historically, this has been performed by postsintering deformation. There has been considerable research

Preston B. Kemp; Randall M. German

1995-01-01

232

Aero-acoustic levitation: A method for containerless liquid-phase processing at high temperatures  

Microsoft Academic Search

A method for containerless liquid-phase processing was developed which has practical application in process and property research on virtually any material which is involatile at the melting point. It combines aerodynamic and acoustic forces to support and position the levitated material. The design provides forced convection control of the thermal boundary in the gas surrounding beam-heated specimens, which stabilizes the

J. K. Richard Weber; D. Scott Hampton; Dennis FL Merkley; Charles A. Rey; Mark M. Zatarski; Paul C. Nordinea

1994-01-01

233

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

SciTech Connect

A large fraction of submicron atmospheric particles contains both organic material and inorganic salts. As the relative humidity cycles in the atmosphere, 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 semi-volatile organic compounds, the scattering and absorption of solar radiation, and the uptake of reactive gas species on atmospheric particles will be affected, with important implications for climate predictions. The actual occurrence of these types of phase transitions 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 observe the coexistence of two non-crystalline phases in particles generated from real-world samples collected on multiple days in Atlanta, Georgia, and in particles generated in the laboratory using atmospheric conditions. These results reveal that atmospheric particles can undergo liquid-liquid phase separations. Using a box model, we show that liquid-liquid phase separation can result in increased concentrations of gas-phase NO3 and N2O5 in the Atlanta region, due to decreased particle uptake of N2O5.

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

2012-07-30

234

Conditions of liquid phase formation in operation of fire-extinguishing aerosol generators  

Microsoft Academic Search

Reasons for formation of the liquid phase in operation of fire-extinguishing aerosol generators were examined. The amount\\u000a of the melt formed depends on the particle size and on the inclination angle and length of the cylindrical generator.

I. V. Krauklish; I. Yu. Rodionov; V. A. Sirotko

2008-01-01

235

Investigation of the Growth of Garnet Films by Liquid Phase Epitaxy.  

National Technical Information Service (NTIS)

Liquid phase expitaxy was investigated to determine its applicability to fabricating magnetic rare earth garnet films for spacecraft data recording systems. Two mixed garnet systems were investigated in detail: (1) Gd-Y and (2) Eu-Yb-Y. All films were dep...

J. W. Moody R. W. Shaw R. M. Sandfort

1974-01-01

236

An Improved Process for Selective Liquid-Phase Air Oxidation of Toluene  

Microsoft Academic Search

An improved process for the oxidation of toluene to obtain benzaldehyde and benzyl alcohol with high selectivities using a Co\\/Mn\\/Br- composite catalytic system in liquid phase is described. A protocol for recovery and reuse of the composite catalyst is developed. The use of low concentrations of composite catalytic systems aimed at minimizing corrosion of the reaction, and higher concentrations of

Mannepalli Lakshmi Kantam; Pentlavalli Sreekanth; Kottapalli Koteswara Rao; Thella Prathap Kumar; Bhavnari Purna C. Rao; Boyapati Manoranjan Choudary

2002-01-01

237

Liquid Phase Methanation Pilot Plant Installation and Operation. Quarterly Report, July 1--September 30, 1976.  

National Technical Information Service (NTIS)

The present project status involves an overlap with Phase III of Contract No. E(49-18)-1505 which includes completion of a movable Liquid Phase Methanation (LPM) Pilot Plant. Work continued on the repair of defective welds and was completed. A hydrostatic...

1977-01-01

238

Construction materials for reaction unit in the liquid-phase synthesis of propylene oxide  

Microsoft Academic Search

The main components of the reaction medium in equipment for the synthesis of propylene oxide by liquid-phase oxidation of gaseous propylene with peracetic acid are propylene, peracetic acid, ethyl acetate, acetic acid, propylene oxide, carbon dioxide, oxygen, methane, and propylene glycol acetates. The operating conditions of the equipment and content of the main components of the medium are shown. Results

V.-I. D. Zaritskii; V. I. D

1987-01-01

239

Direct applications of stabilized methanol from the liquid phase methanol (LPMEOH) process  

Microsoft Academic Search

The Liquid Phase Methanol (LPMEOH) process uses a slurry bubble column reactor to convert synthesis (syngas) gas to methanol. Because of its superior heat management, the process can directly utilize the carbon monoxide (CO)-rich syngas characteristic of the gasification of coal, petroleum coke, residual oil, wastes, or other hydrocarbon feedstocks. When added to an integrated gasification combined cycle (IGCC) power

B. L. Bhatt; E. C. Heydorn; P. J. A. Tijm; R. M. Kornosky

1999-01-01

240

Coupled Ion Complexation and Exchange between Aqueous and Ionic Liquid Phases: A Thermodynamic Interpretation  

Microsoft Academic Search

Experimental studies of ion extraction from aqueous to ionic liquid phases have demonstrated that, in many cases, extraction of an ion from the aqueous phase is coupled to counterextraction of similarly charged ions from the ionic phase. These exchanges often involve coordination complexes that are not observed in extractions from aqueous phases to molecular organic liquids. We make a thermodynamic

Mark N. Kobrak

2008-01-01

241

Processing of iron-titanium powder mixtures by transient liquid phase sintering  

Microsoft Academic Search

Transient liquid phase sintering was examined for Fe-Ti powder mixtures. The experimental plan included the effects of several processing variables, such as green density, particle size, composition, heating rate, sintering temperature, and sintering time. During heating, pores form at the Ti particle sites. At the first eutectic temperature (1085 °C), liquid spreading is inhibited by a surrounding intermetallic envelope, leading

R. M. German; J. W. Dunlap

1986-01-01

242

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

SciTech Connect

As part of the liquid phase methanol process development program the present study evaluated adsorptive schemes to remove catalyst poisons from coal gas at pilot scale. In addition to a lab test with coal gas from Coolwater, two field tests were performed at Great Plains with live coal gas. In the lab with Coolwater, gas iron carbonyl, carbonyl sulfide,and hydrogen sulfide were effectively removed from the coal gas. The capacities of H-Y zeolite and BPL carbon for Fe(CO){sub 5} agreed well with the previous bench scale results at similar CO{sub 2} partial pressure. COS appeared to be chemisorbed on FCA carbon; its capacity was non-regenerable by hot nitrogen purge. A Cu/Zn catalyst, used to remove H{sub 2}S adsorptively, worked adequately. With the adsorption system on-line, a downstream methanol catalyst showed stable activity for 120 hours of operation. In the two field tests, it was demonstrated that the Great Plains (GP) syngas could be treated by adsorption for LPMEOH process. The catalyst deactivation observed in the first field test was much improved in the second field test after regular (every three days) regeneration of the adsorbents was practiced. The absorption system, which was designed for the removal of iron/nickel carbonyls, hydrogen/carbonyl sulfide and hydrochloric acid, needed to be modified to accommodate other unexpected impurities, such as acetonitrile and ethylene which were observed during both field tests. A lab test with a simulated GP gas indicated that low CO{sub 2} content (0.5%) in the GP gas does not cause catalyst deactivation. Adjusting the CO{sub 2} content of the feed to 5% by CO{sub 2} addition, increased methanol productivity by 40% in both the lab and the second field test. 6 refs., 25 figs., 14 tabs.

Not Available

1990-11-09

243

In situ evaluation of supersolidus liquid phase sintering phenomena of stainless steel 316L: Densification and distortion  

Microsoft Academic Search

Supersolidus liquid phase sintering (SLPS) is a variant of liquid phase sintering. In SLPS, prealloyed powders are heated between the solidus and liquidus temperature of the alloy. This thesis focuses on processing of stainless steel 316L via SLPS by adding boron. Various amounts of boron were added to study the effect of boron on densification and distortion. The sintering window

Ravi Bollina

2005-01-01

244

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

245

Liquid-phase pulsed laser ablation and electrophoretic deposition for chalcopyrite thin-film solar cell application.  

PubMed

We report ligand-free synthesis of colloidal metallic nanoparticles using liquid-phase pulsed laser ablation, and electrophoretic deposition of the nanoparticles for fabrication of Cu(In,Ga)Se(2) (CIGS) thin film solar cells. First, colloidal metallic nanoparticles of Cu-In and Cu-Ga alloys are produced by pulsed laser ablation in common organic solvents without using stabilizing ligands. The nanoparticles are examined for phase, composition, and electrical surface charging and charge modulation mechanisms. Metallic precursor thin films with high purity and precise composition are produced by electrophoretic deposition of the colloids without transferring to another solvent and without using binders. Finally, we demonstrate fabrication of CIGS solar cells on Mo sheet substrates with an (active area) energy conversion efficiency up to 7.37%. PMID:23206317

Guo, Wei; Liu, Bing

2012-12-12

246

Preparation of anatase nanocrystallines from low concentration precursor solution via a microwave assisted liquid phase deposition (MW-LPD) process  

SciTech Connect

Nanocrystalline titanium dioxide in the anatase phase was successfully prepared via a facile microwave assisted liquid phase deposition (MW-LPD) process with hexafluorotitanate ammonium (NH{sub 4}){sub 2}TiF{sub 6} as precursor. Compared with the conventional LPD processes, the MW-LPD technique could provide quickly high yield and crystallinity in a diluted precursor solution at low temperature because the high-frequency microwaves penetrated into the bulk of the material and the volumetric interaction of the electromagnetic fields with the material results in dielectric (volumetric) heating. This led to higher heating efficiency with faster processing. The X-ray diffraction (XRD) and selected-area electron diffraction (SAED) studies on these powders indicated that the powders obtained with MV irradiation have much higher crystallinity with a single phase anatase. Their photocatalytic activities were also investigated by the photodegradation of methylene blue (MB) as a model molecule.

Zhang Liuxue [College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu 730000 (China); Liu Peng [College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu 730000 (China); Su Zhixing [College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu 730000 (China)]. E-mail: suzx@lzu.edu.cn

2006-09-14

247

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.

248

Carrier mediated hollow fiber liquid phase microextraction combined with HPLC-UV for preconcentration and determination of some tetracycline antibiotics.  

PubMed

In the present study, a simple and efficient preconcentration method was developed using carrier mediated three phase liquid phase microextraction prior to HPLC-UV for simultaneous extraction and determination of trace amounts of highly hydrophilic tetracycline antibiotics including tetracycline (TCN), oxytetracycline (OTCN) and doxycycline (DCN) in bovine milk, human plasma and water samples. For extraction, 11.0 mL of the aqueous sample containing TCNs and 0.05 M Na(2)HPO(4) (9.1liquid phase microextraction were evaluated and optimized. Under the optimized conditions, the calibration curves were linear in the range of 0.5-1,000 microgL(-1) for TCN and OTCN, and in the range of 5-1,000 microgL(-1) for DCN with good linearity (r(2)>0.995). Finally, applicability of the proposed method was successfully confirmed by extraction and determination of the drugs in water and plasma samples as well as in bovine milk samples with low and high fat contents. Comparing to the traditional methods, the proposed method exhibits high sensitivity and high preconcentration factors as well as good precision. The extraction setup is simple and due to active transport of analytes, high cleanup effect and good selectivity are obtained in extraction process. PMID:19124286

Shariati, Shahab; Yamini, Yadollah; Esrafili, Ali

2008-12-25

249

Separation of coal-tar constituents from soil particles in a two-liquid-phase slurry system.  

PubMed

An evaluation has been made of the capability of rapeseed oil to dissolve polycyclic aromatic hydrocarbon (PAH) crystals in a biphasic system and of its capability to extract PAHs from polluted soil in a two-liquid-phase (TLP) slurry system. Up to 220 g l(-1) of the crystalline hydrocarbons could be dissolved in the organic phase, indicating oil/water-partitioning coefficients of 10(5). When soil from a former gasworks site was treated in a TLP slurry system, it was found that a certain critical amount of vegetable oil had to be added in order to form a free oil phase. Single and multiple extractions gave similar results for multiple short-term and single long-term treatments, with a maximum of 87% for pyrene release. Following a 30-day bioslurry treatment, the total concentration of the 16 EPA PAHs in the soil decreased from 2740 mg kg(-1) to 1366 mg kg(-1). This was followed by one of three different 12-day post-bioslurry treatments. Further bioslurry treatment reduced the final concentration to 1002 mg kg(-1). Abiotic treatment with a surfactant (Brij 30) achieved a reduction to 797 mg kg(-1). Treatment with rapeseed oil gave the best reduction to 343 mg kg(-1). PMID:12868531

Schuur, J H Berg; Mattiasson, B

2003-06-01

250

Edge states and topological orders in the spin liquid phases of star lattice  

NASA Astrophysics Data System (ADS)

The integer quantum Hall effect (IQHE) on star lattice is studied through edge states in the context of spin liquid. We apply the bulk-edge correspondence to the star lattice and analyze the edge states and their topological orders for different spin liquid phases. The band structures and Chern number depend on the local spontaneous magnetic flux and hopping parameters due to the breaking of the time reversal and space inversion symmetries. We give the characteristics of bulk and edge energy structures and their corresponding Chern numbers in the uniform, nematic and chiral spin liquids. In particular, we obtain analytically the phase diagram of the topological orders for the chiral spin liquid states SL[?,?,-2?], where ? is the magnetic flux in two triangles and a dodecagon in one unit cell. Moreover, because of the direct connection between Chern number and the conductance of IQHE, we can further distinguish the different spin liquid phases through a Hall measurement.

Huang, Guang-Yao; Liang, Shi-Dong; Yao, Dao-Xin

2013-09-01

251

Control of growth uniformity of III-V bulk crystals grown by contactless liquid phase electroepitaxy  

NASA Astrophysics Data System (ADS)

Systematic studies of influence of crucible design on uniformity of growth of bulk III-V crystals by contactless liquid phase electroepitaxy (CLPEE) are reported. CLPEE removes the most important drawback of standard liquid phase electroepitaxy, i.e. limited thickness of crystals being due to superheating of the growing crystals by Joule heat generation. However, the CLPEE method in its simplest version suffers from enhanced growth rate at the center of the crystal, which results from majority of electric current flowing to the center of the electrode and dragging solute species. A number of various designs of growth crucible are examined showing that optimized triple-electrode system is capable to provide perfectly uniform growth rate distribution over a large portion of the surface of the growing crystal. In this way the main obstacle in development of the CLPEE technique is removed allowing application of electroepitaxy to obtain large diameter high crystalline quality single crystals with potentially unlimited thickness.

Strak, Pawel; Zytkiewicz, Zbigniew R.; Krukowski, Stanislaw

2012-09-01

252

A mathematical model for gravity-induced distortion during liquid-phase sintering  

NASA Astrophysics Data System (ADS)

Liquid-phase-sintered materials consist of interconnected crystalline grains in a homogeneous matrix phase that forms a liquid during sintering. These composites exhibit viscous flow during sintering that allows densification. Gravitational forces give rise to compact distortion when there is a large amount of liquid at a high temperature. This article treats kinetic aspects of distortion during sintering of tungsten heavy alloys (W-Ni-Fe). The mathematical model predicts distortion and highlights the important variables influencing this phenomenon. The results provide guidelines for minimizing distortion due to gravity. Experiments conducted at several different sintering times show reasonably good agreement with theoretical predictions using the liquid-phase viscosity as a single adjustable parameter. Theoretical predictions of the model are crucial to designing microgravity experiments aimed at understanding dimensional stability.

Raman, R.; German, Randall M.

1995-03-01

253

Growth of bulk SiGe single crystals by liquid phase diffusion  

NASA Astrophysics Data System (ADS)

The article presents a study for liquid phase diffusion (LPD) growth of compositionally graded, germanium-rich SixGe1-x single crystals of 25 mm in diameter for use as lattice-matched substrates for the growth of SixGe1-x single crystals by liquid phase electropitaxy (LPEE), or traveling heater method (THM). Grown crystals were characterized by microscopic examination after chemical etching for delineation of the degree of single crystallinity and growth striations. Compositional mapping of selected crystals was performed by using electron probe micro analysis (EPMA) as well as energy dispersive X-ray analysis (EDX). It was shown that the LPD technique can be utilized to obtain SixGe1-x single crystals up to 6 8 at% Si with uniform radial composition distribution.

Yildiz, M.; Dost, S.; Lent, B.

2005-06-01

254

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

255

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

NASA Astrophysics Data System (ADS)

Germanium Blocked Impurity Band (BIB) detectors require a high purity blocking layer (<1013 cm-3) approximately 1 mum thick grown on a heavily doped active layer (˜10 16 cm-3 approximately 20 mum 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° and 10° from the {111} toward the {100}. 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 ˜1015 cm-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 ˜1014 cm -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 (˜1016 cm-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 (˜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 ˜1.5 mum. Layers grown at 550°C did not show significant Sb diffusion. Sn doped In2O3 (ITO) was studied for use in far infrared transparent low temperature contacts for BIB arrays. It was found that ˜100 nm of ITO deposited on Ge remains electrically conducting at 4 K and is ˜90% transparent in the far infrared. ITO should be suitable for passivating contacts to Ge BIB arrays.

Bandaru, Jordana

256

Bilevel optimization formulation for parameter estimation in vapor–liquid(–liquid) phase equilibrium problems  

Microsoft Academic Search

A rigorous method is proposed for parameter estimation in thermodynamic models used for predicting vapor–liquid and vapor–liquid–liquid equilibrium of binary mixtures. Typically, vapor–liquid(–liquid) equilibria are modeled using asymmetric models, i.e., an excess Gibbs free energy model for the liquid phase and an equation of state for the vapor phase. Parameter estimation for asymmetric models is a nontrivial task. The existence

George M. Bollas; Paul I. Barton; Alexander Mitsos

2009-01-01

257

Determination of sintering parameters for liquid phase sintering of silicon nitride  

NASA Astrophysics Data System (ADS)

The sintering parameters of silicon nitride were determined during the second stage of liquid phase sintering via interrupted sinter forging tests under compressive uniaxial load. The silicon nitride with an yttria-alumina rich secondary phase (Saint-Gobain composition NB D300) was submitted to seven level of stress (from 0.24MPa to 9.41MPa) at three different temperatures (1500°C, 1550°C and 1600°C) with continuous monitoring of the axial and longitudinal shrinkage during all experiments to directly obtain the sintering stress, Poisson's ratio and bulk viscosity. The sintering stress measured in the first 1.5 minutes after reaching temperature was 7.5MPa at 1500°C (˜60% theoretical density), 21.5 MPa at 1550°C (˜70% dense) and 11.5MPa at 1600°C (˜80% dense). The bulk viscosity also peaks at the intermediate density at about 48GPas. This variation is largely attributed to the noticeable changes of microstructure during the second stage of liquid phase sintering, especially the overall pore size distribution as well as the degree to which the liquid phase is fully melted and partially or fully fills the smallest pores. The experimental data were then inserted into a numerical model developed by Abouaf. Proper fit of the model could not be obtained without considering the rearrangement stage of sintering. Considering both the rearrangement and solution-precipitation stages of densification, it was possible to determine the variation during sintering of different parameters that influences the liquid phase sintering and therefore the microstructure development.

Theron, Claire

258

Thermodynamic analysis of liquid phase in situ hydrogenation of glycerol for 1,3-propanediol synthesis  

Microsoft Academic Search

Based on the combination of the glycerol aqueous-phase reforming (APR) and catalytic hydrogenation of glycerol, a novel reaction\\u000a system of liquid phase in situ hydrogenation of glycerol for the synthesis of 1,3-propanediol is proposed, in which hydrogen\\u000a is produced from glycerol aqueous-phase reforming in the same reactor. In this new system, the glycerol is the raw material\\u000a of the aqueous-phase

Kun Ouyang; Yu Huang; Haoyi Chen; Tao Li; Fahai Cao; Dingye Fang

2011-01-01

259

Crystal growth of mode-stabilized semiconductor diode lasers by liquid-phase epitaxy  

Microsoft Academic Search

A brief description of the liquid-phase epitaxial (LPE) process and the LPE growth equipment required for diode-laser fabrication is presented. Planar-geometry laser structures are described as a preamble to the treatment of complex mode-stabilized devices. LPE growth over nonplanar substrates is discussed and presented as the major technique for the fabrication of low- and high-power, single-mode, reliable diode lasers. Major

D. Botez; J. C. Connolly

1983-01-01

260

Densification of a powder-metal skeleton by transient liquid-phase infiltration  

Microsoft Academic Search

Transient liquid-phase infiltration (TLI) is a new method for densifying a powder-metal skeleton that produces a final part\\u000a of homogeneous composition without significant dimensional change, offering advantages over traditional infiltration and full-density\\u000a sintering. Fabrication of direct metal parts with complex geometry is possible using TLI in conjunction with solid freeform\\u000a fabrication (SFF) processes such as three-dimensional printing, which produce net-shape

Adam Lorenz; Emanuel Sachs; Brian Kernan; Samuel Allen Posco; Lukas Rafflenbful

2004-01-01

261

Trends in liquid-phase microextraction, and its application to environmental and biological samples  

Microsoft Academic Search

Liquid phase microextraction (LPME) is a popular technique for sample pretreatment before the trace determination of target\\u000a compounds from complex matrices, examples being pesticides in environmental and food samples, or drug residuals in biological\\u000a samples such as blood or urine. LPME is simple, affordable, easy to operate, and highly sensitive. It is a miniaturized implementation\\u000a of conventional liquid-liquid extraction in

Dandan Han; Kyung Ho Row

262

Ferromagnetically modified zeolite catalysts for liquid-phase High–Throughput Experimentation  

Microsoft Academic Search

A novel method for the separation of heterogeneous catalysts from liquid-phase reactions in High–Throughput Experimentation (HTE) libraries was developed based on a magnetic recuperation procedure. Ferromagnetic iron nanoparticles were introduced in a set of zeolite structures by means of aqueous impregnation of an iron precursor, followed by reduction in H2. The obtained magnetic zeolites can be efficiently stirred in the

Paolo P. Pescarmona; Bogdan C. Gagea; Peter Van der Aa; Pierre A. Jacobs; Johan A. Martens

2011-01-01

263

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

264

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

265

Microstructure of the gravitationally settled region in a liquid-phase sintered dilute tungsten heavy alloy  

Microsoft Academic Search

A dilute tungsten heavy alloy consisting of 50W-35Ni-15Fe (wt pct) was liquid phase sintered at 1500 ° for times ranging from\\u000a 30 to 960 minutes. This alloy corresponds to a nominal solid content of 20 vol pct at the sintering temperature. Because of\\u000a the excess liquid, the alloy den-sified easily and exhibited extensive liquid-solid separation due to the density difference

Randall M. German

1995-01-01

266

Effect of strain rate on the flow stress of three liquid phase sintered tungsten alloys  

Microsoft Academic Search

Stress\\/strain tests were carried out in compression on three liquid phase sintered tungsten alloys, with tungsten contents\\u000a of 90, 95, and 97.4 wt pct, in the strain rate range 10?3 s?1 to 103 s?1. Each alloy shows a gradual increase of flow stress with strain rate, and evidence of work softening is observed when the\\u000a strain rate is of the

R. L. Woodward; N. J. Baldwin; I. Burch; B. J. Baxter

1985-01-01

267

On the Extension of Processing Time with Increase in Temperature during Transient-Liquid Phase Bonding  

Microsoft Academic Search

Transient-liquid phase (TLP) bonding of a nickel-based superalloy, IN 738, was performed. Contrary to conventional TLP bonding\\u000a analytical models, which assume a parabolic relationship between liquid\\/solid interface migration and holding time, deviation\\u000a from this law was observed experimentally and by numerical simulation. The deviation, which is caused by reduction in solute\\u000a concentration gradient below a critical value, is suggested as

M. M. Abdelfatah; O. A. Ojo

2009-01-01

268

Shape-selective ester hydrolysis by octadecyl immobilized H-ZSM-5 catalyst in liquid phase  

Microsoft Academic Search

The shape-selective property of octadecyltrichlorosilane treated H-ZSM-5, keeping the original acid strength (?5.6Ho??3.0) in liquid phase in the hydrolysis of straight chain esters has been observed by comparing the reaction rates with those over octadecyltrichlorosilane treated SiO2-Al2O3. The most pronounced effect was found in the case of ethyl decanoate, viz. ca. 6 times.

H. Ogawa; T. Koh; K. Taya; T. Chihara

1992-01-01

269

A mathematical model for gravity-induced distortion during liquid-phase sintering  

Microsoft Academic Search

Liquid-phase-sintered materials consist of interconnected crystalline grains in a homogeneous matrix phase that forms a liquid\\u000a during sintering. These composites exhibit viscous flow during sintering that allows densification. Gravitational forces give\\u000a rise to compact distortion when there is a large amount of liquid at a high temperature. This article treats kinetic aspects\\u000a of distortion during sintering of tungsten heavy alloys

R. Raman; Randall M. German

1995-01-01

270

Spectroscopic Properties of Porphyrin-doped Silica Films by the Liquid Phase Deposition Method  

Microsoft Academic Search

Silica films doped with water soluble porphyrin, 5,10,15,20-tetrakis[4-(N-trimethyl)ammonio]phenylporphyrin (TTMAPP), were deposited on the surface of a glass slide at 25–35°C by the liquid phase deposition (LPD) method from saturated hydrofluorosilicic acid or fluorosilicate solutions containing TTMAPP. It was doped as protonated (cationic) or neutral forms depending on the deposition condition. Two forms are reversibly converted by heat treatment or environments.

Toshihiko Nagamura; Hirohisa Smmizu; Hiroyasu Ohkoso

1998-01-01

271

Liquid-liquid phase separation in concentrated solutions of non-crystallizable polymers by spinodal decomposition  

Microsoft Academic Search

Summary  Two mechanisms of liquid-liquid phase separation in polymer solutions are possible: nucleation and growth of one of the equilibrium\\u000a phases, and decomposition by a spinodal mechanism. The conditions for and characteristics of both mechanisms are discussed.\\u000a By combining a number of observations on phase separation in concentrated solutions of poly(2,6-dimethyl-1,4-phenylene ether)\\u000a and of an ethylene — vinyl acetate copolymer in

C. A. Smolders; J. J. van Aartsen; A. Steenbergen

1971-01-01

272

Liquid phase bromination of aromatics over zeolite H-beta catalyst  

Microsoft Academic Search

The liquid phase bromination of chlorobenzene, toluene and xylenes (o-, m-, p-) is catalyzed using zeolite as catalyst and N-bromosuccinimide (NBS) as the brominating agent. In addition, the bromination of toluene has been investigated over various zeolites using both NBS and liquid Br2 as brominating agents. A comparison under similar reaction conditions with H2SO4, in the absence of catalyst and

A. P Singh; S. P Mirajkar; S Sharma

1999-01-01

273

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

NASA Astrophysics Data System (ADS)

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 fuel and soot distribution studies were conducted at a medium speed (1,200 rpm) using a Cummins closed-nozzle fuel injector. The scattering was used to obtain planar images of the liquid-phase fuel distribution. These images show that the leading edge of the liquid-phase portion of the fuel jet reaches a maximum length of 24 mm, which is about half the combustion bowl radius for this engine. Beyond this point virtually all the fuel has vaporized. Soot distribution measurements were made at a high load condition using three imaging diagnostics: natural flame luminosity, 2-D laser-induced incandescence, and 2-D elastic scattering. This investigation showed that the soot distribution in the combusting fuel jet develops through three stages. First, just after the onset of luminous combustion, soot particles are small and nearly uniformly distributed throughout the luminous region of the fuel jet. Second, after about 2 crank angle degrees a pattern develops of a higher soot concentration of larger sized particles in the head vortex region of the jet and a lower soot concentration of smaller sized particles upstream toward the injector. Third, after fuel injection ends, both the soot concentration and soot particle size increase rapidly in the upstream portion of the fuel jet.

Dec, J. E.; Espey, C.

1993-10-01

274

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

Microsoft Academic Search

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

Carles Fite; Montserrat Iborra; Javier Tejero; Jose F. Izquierdo; Fidel Cunill

1994-01-01

275

Liquid phase oxidation for InGaP\\/GaAs HBT passivation  

Microsoft Academic Search

Native oxide films grown near room temperature by liquid phase oxidation (LPO) on p+-GaAs, n-InGaAs and n-InGaP are investigated. Their applications to heterojunction bipolar transistors (HBTs) are also demonstrated and characterized. With the LPO as surface passivation, the dc current gain beta of the HBT devices increases sevenfold in low collector current regimes, and it also shows wider collector regimes

Po-Wen Sze; Kuan-Wei Lee; Jian-Jiun Huang; Nan-Ying Yang; Yeong-Her Wang

2006-01-01

276

Liquid-Phase Detection of Organophosphate Pesticides Using Guided SH-SAW Sensor  

Microsoft Academic Search

It has been established that a polymer-coated SH-SAW sensor on 36deg rotated Y-cut LiTaO3 is a very sensitive platform for direct liquid-phase chemical sensing. In this work, two partially selective coatings, poly(epichlorohydrin) and polyurethane are investigated for the detection of organophosphate pesticides (phosmet and parathion) in aqueous solutions. Moreover, in order to meet the need for sensitive and selective chemical

A. Mensah-Brown; M. J. Wenzel; F. Josse; E. Yaz; O. Sadik

2007-01-01

277

Liquid phase sintering (LPS) and dielectric constant of ?-silicon nitride ceramic  

Microsoft Academic Search

The spark plasma sintering (SPS) was applied to prepare ?-Si3N4 ceramics of different densities with magnesia, silicon dioxide, alumina as the sintering aids. The mechanism of liquid phase\\u000a sintering (LPS) was discussed and the factors influencing the density of the prepared samples were analyzed. The dielectric\\u000a constant of sintered samples was tested. The experimental results show that the density can

CHEN Changlian I CHEN; Chen Fei; Shen Qiang; Zhang Lianmeng; Yan Faqiang

2006-01-01

278

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

279

A method of removing metal ions from silicate glasses for recycling by liquid-phase deposition  

Microsoft Academic Search

A method of removing metal ions from silicate glasses for recycling was studied. This method utilizes a liquid-phase deposition (LPD) technique using a hydrofluosilicic acid (H2SiF6) aqueous solution supersaturated with silica. Silicate glass powder prepared from a glass bottle was dissolved in aqueous hydrofluoric acid (HF) solution. The fluorinated silicon oxide (SiOF) separated from the H2SiF6, and then an LPD-SiOF

Tetsuya Homma

2001-01-01

280

Optical properties of fluorinated silicon oxide films by liquid phase deposition for optical waveguides  

Microsoft Academic Search

Optical properties of fluorinated silicon oxide (SiOF) films for optical waveguide in optoelectronic devices were investigated. The SiOF films are formed at 25°C by a liquid phase deposition (LPD) technique using a supersaturated hydrofluosilicic acid (H2SiF 6) aqueous solution. Two main absorption peaks corresponding to Si-O and Si-F bonds were observed at the wavenumbers of 1090 and 930 cm-1 in

Tetsuya Homma; Atsushi Satoh; Seiji Okada; Masahiro Itoh; Masaki Yamaguchi; Hideo Takahashi

1998-01-01

281

Liquid-phase ozonization of concentrates of the petrographic components of isometamorphic coals  

SciTech Connect

The fractionated ozonization products of the vitrain and fusain lithotypes of isometamorphic coals of the middle stage of metamorphism from the Kuznetsk Basin in glacial acetic acid were characterized using IR spectroscopy, thermogravimetry, and chromatography-mass spectrometry. Fusainized coal components exhibited higher reactivity toward ozone. Water-soluble low-molecular-weight compounds were predominant among the products of the liquid-phase ozonization of the lithotypes. 11 refs., 4 figs., 3 tabs.

S.A. Semenova; Yu.F. Patrakov [Russian Academy of Sciences, Kemerovo (Russian Federation). Institute of Coal and Coal Chemistry

2008-02-15

282

Partial order in the non-Fermi-liquid phase of MnSi  

Microsoft Academic Search

Only a few metallic phases have been identified in pure crystalline materials. These include normal, ferromagnetic and antiferromagnetic metals, systems with spin and charge density wave order, and superconductors. Fermi-liquid theory provides a basis for the description of all of these phases. It has been suggested that non-Fermi-liquid phases of metals may exist in some heavy-fermion compounds and oxide materials,

C. Pfleiderer; D. Reznik; L. Pintschovius; H. v. Löhneysen; M. Garst; A. Rosch

2004-01-01

283

Applying selective liquid-phase deposition to create contact holes in plasma damage-free process  

Microsoft Academic Search

We apply an alternative plasma damage-free process, selective liquid-phase deposition (S-LPD), instead of the conventional RIE to form metal\\/semiconductor contact holes. This paper studies the performance comparison between S-LPD and RIE for formation of contact holes in n+\\/p junction diodes, Schottky diodes, and ohmic contacts. In our experiments, if the plasma-free S-LPD technique is adopted, there is excellent performance, including

C.-F. Yeh; C.-H. Liu

1998-01-01

284

Experimental study of solid–liquid phase change in a spiral thermal energy storage unit  

Microsoft Academic Search

A new idea on the use of a vertical spiral heat exchanger in a latent heat thermal energy storage system is analyzed experimentally. In this context, two important subjects are addressed. The first one is the temporal behavior of a phase change medium undergoing a non-isothermal solid–liquid phase change transition during its two-side heating or cooling by a working fluid

J Banaszek; R Domañski; M Rebow; F El-Sagier

1999-01-01

285

RESEARCH NOTE The absence of a liquid phase in van der Waals fluids at high dimensionality  

NASA Astrophysics Data System (ADS)

It is demonstrated that a model van der Waals fluid does not possess a liquid phase at high dimensionality. The model is hard hypercubes with a long-range attraction. The gas-liquid and fluid-solid transitions cross as the dimensionality is increased, and at high dimensionality the gas-liquid transition is pre-empted by the transition to a solid phase.

Sear Bela, Richard P.; Mulder, M.

286

NickelTin Transient Liquid Phase (TLP) Wafer Bonding for MEMS Vacuum Packaging  

Microsoft Academic Search

This paper reports vacuum data for nickel-tin transient liquid phase (TLP) wafer bonding. Two wafers, one with a titanium getter and another with Pirani vacuum sensors, were bonded for 1.5 hours at 300 °C. Initial pressures were as low as 200 mTorr and have remained stable for half a month. After several days, some of the packages were heated to

W. C. Welch; K. Najafi

2007-01-01

287

One-Step Liquid-Phase Synthesis of Carbon Nanotubes with Catalyst Precursors of Organometallic Complexes  

Microsoft Academic Search

This paper describes a simple, low cost one-step liquid-phase process for the synthesis of highly aligned carbon nanotube (CNT) arrays (HACNTAs). Highly pure HACNTAs were grown on a stainless steel substrate by resistance-heating in methanol solution containing one of the organometallic complex catalyst precursors, ferrocene Fe(C5H5)2 and iron pentacarbonyl Fe(CO)5. Effects of the catalyst precursors on the formation and morphologies

Kiyofumi Yamagiwa; Tomoka Kikitsu; Shunsuke Yamashita; Jun Kuwano

2011-01-01

288

Processing of iron-titanium powder mixtures by transient liquid phase sintering  

Microsoft Academic Search

Transient liquid phase sintering was examined for Fe-Ti powder mixtures. The experimental plan included the effects of several\\u000a processing variables, such as green density, particle size, composition, heating rate, sintering temperature, and sintering\\u000a time. During heating, pores form at the Ti particle sites. At the first eutectic temperature (1085 C), liquid spreading is\\u000a inhibited by a surrounding intermetallic envelope, leading

R. M. German; J. W. Dunlap

1986-01-01

289

Agarose film liquid phase microextraction combined with gas chromatography-mass spectrometry for the determination of polycyclic aromatic hydrocarbons in water.  

PubMed

Agarose film liquid phase microextraction (AF-LPME) procedure for the extraction and preconcentration of polycyclic aromatic hydrocarbons (PAHs) in water has been investigated. Agarose film was used for the first time as an interface between donor and acceptor phases in liquid phase microextraction which allowed for selective extraction of the analytes prior to gas chromatography-mass spectrometry. Using 1-octanol as acceptor phase, high enrichment factors in the range of 57-106 for the targeted analytes (fluorene, phenanthrene, fluoranthene and pyrene) were achieved. Under the optimum extraction conditions, the method showed good linearity in the range of 0.1-200 ?gL(-1), good correlation coefficients in the range of 0.9963-0.9999, acceptable reproducibility (RSD 6.1-9.2%, n=3), low limits of detection (0.01-0.04 ?gL(-1)) and satisfactory relative recoveries (92.9-104.7%). As the AF-LPME device was non-expensive, reuse or recycle of the film was not required, thus eliminating the possibility of analytes carry-over between runs. The AF-LPME technique is environment-friendly and compatible with the green chemistry concept as agarose is biodegradable polysaccharide extracted from seaweed and the procedure requires small volume of organic solvent and generates little waste. The validated method was successfully applied to the analysis of the four analytes in river water samples. PMID:23021646

Sanagi, Mohd Marsin; Loh, Saw Hong; Wan Ibrahim, Wan Aini; Hasan, Mohamed Noor

2012-09-11

290

Esterification of sodium 4-hydroxybenzoate by ultrasound-assisted solid-liquid phase-transfer catalysis using dual-site phase-transfer catalyst.  

PubMed

The catalytic esterification of sodium 4-hydroxybenzoate with benzyl bromide by ultrasound-assisted solid-liquid phase-transfer catalysis (U-SLPTC) was investigated using the novel dual-site phase-transfer catalyst 4,4'-bis(tributylammoniomethyl)-1,1'-biphenyl dichloride (BTBAMBC), which was synthesized from the reaction of 4,4'-bis(chloromethyl)-1,1'-biphenyl and tributylamine. Without catalyst and in the absence of water, the product yield at 60°C was only 0.36% in 30min of reaction even under ultrasound irradiation (28kHz/300W) and 250rpm of stirring speed. When 1cm(3) of water and 0.5mmol of BTBAMBC were added, the yield increased to 84.3%. The catalytic intermediate 4,4'-bis(tributylammoniomethyl)-1,1'-biphenyl di-4-hydroxybenzoate was also synthesized to verify the intrinsic reaction which was mainly conducted in the quasi-aqueous phase locating between solid and organic phases. Pseudo-first-order kinetic equation was used to correlate the overall reaction, and the apparent rate coefficient with ultrasound (28kHz/300W) was 0.1057min(-1), with 88% higher than that (0.0563min(-1)) without ultrasound. The esterification under ultrasonic irradiation using BTBAMBC by solid-liquid phase-transfer catalysis was developed. PMID:23972326

Yang, Hung-Ming; Chu, Wei-Ming

2013-08-13

291

Equilibrium partial pressures and mean activity and osmotic coefficients of 0-100% nitric acid as a function of temperature  

SciTech Connect

Rational activity and osmotic coefficients and Henry's law constants K{sub Hx} (for the reaction HNO{sub 3(g)} = H{sup +}{sub (aq)} + NO{sub 3}{sup {minus}}{sub (aq)}), given as functions of temperature, enable p(H{sub 2}O) and p(HNO{sub 3}) to be calculated from {minus}60 to 120{degree}C, 0-100% HNO{sub 3}. Apparent molal enthalpies, heat capacities, and activity coefficients (derived from electromotive force (emf), freezing point, and partial pressure data) are represented with the use of the species-interaction models of Pitzer. Equations for the partial molal functions are given. The Henry's law constant is evaluated from p(HNO{sub 3}) data at 298.15 K, tabulated heats of formation, and heat capacities. Calculated p(H{sub 2}O) and p(HNO{sub 3}) over the entire concentration range agree with available data over 5 orders of magnitude of p(H{sub 2}O) and 7 orders of magnitude of p(HNO{sub 3}).

Clegg, S.L. (Plymouth Marine Laboratory (England)); Brimblecombe, P. (Univ. of East Anglia, Norwich (England))

1990-06-28

292

Two-parameter kinetic model based on a time-dependent activity coefficient accurately describes enzymatic cellulose digestion.  

PubMed

Lignocellulosic biomass is a potential source of renewable, low-carbon-footprint liquid fuels. Biomass recalcitrance and enzyme cost are key challenges associated with the large-scale production of cellulosic fuel. Kinetic modeling of enzymatic cellulose digestion has been complicated by the heterogeneous nature of the substrate and by the fact that a true steady state cannot be attained. We present a two-parameter kinetic model based on the Michaelis-Menten scheme ( Michaelis, L., and Menten, M. L. ( 1913 ) Biochem. Z. , 49 , 333 - 369 ) with a time-dependent activity coefficient analogous to fractal-like kinetics formulated by Kopelman ( Kopelman, R. ( 1988 ) Science 241 , 1620 - 1626 ). We provide a mathematical derivation and experimental support to show that one of the parameters is a total activity coefficient and the other is an intrinsic constant that reflects the ability of the cellulases to overcome substrate recalcitrance. The model is applicable to individual cellulases and their mixtures at low-to-medium enzyme loads. Using biomass degrading enzymes from cellulolytic bacterium Thermobifida fusca , we show that the model can be used for mechanistic studies of enzymatic cellulose digestion. We also demonstrate that it applies to the crude supernatant of the widely studied cellulolytic fungus Trichoderma reesei ; thus it can be used to compare cellulases from different organisms. The two parameters may serve a similar role to Vmax, KM, and kcat in classical kinetics. A similar approach may be applicable to other enzymes with heterogeneous substrates and where a steady state is not achievable. PMID:23837567

Kostylev, Maxim; Wilson, David

2013-07-24

293

Solvent-impregnated agarose gel liquid phase microextraction of polycyclic aromatic hydrocarbons in water.  

PubMed

A new microextraction procedure termed agarose gel liquid phase microextraction (AG-LPME) combined with gas chromatography-mass spectrometry (GC-MS) was developed for the determination of selected polycyclic aromatic hydrocarbons (PAHs) in water. The technique utilized an agarose gel disc impregnated with the acceptor phase (1-octanol). The extraction procedure was performed by allowing the solvent-impregnated agarose gel disc to tumble freely in the stirred sample solution. After extraction, the agarose gel disc was removed and subjected to centrifugation to disrupt its framework and to release the impregnated solvent, which was subsequently withdrawn and injected into the GC-MS for analysis. Under optimized extraction conditions, the new method offered high enrichment factors (89-177), trace level LODs (9-14ngL(-1)) and efficient extraction with good relative recoveries in the range of 93.3-108.2% for spiked drinking water samples. AG-LPME did not exhibit any problems related to solvent dissolution, and it provided high extraction efficiencies that were comparable to those of hollow fiber liquid phase microextraction (HF-LPME) and significantly higher than those of agarose film liquid phase microextraction (AF-LPME). This technique employed a microextraction format and utilized an environmentally compatible solvent holder that supported the green chemistry concept. PMID:23809804

Loh, Saw Hong; Sanagi, Mohd Marsin; Wan Ibrahim, Wan Aini; Hasan, Mohamed Noor

2013-06-14

294

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

PubMed Central

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.

Handa, T; Saito, H; Miyajima, K

1993-01-01

295

Effects of temporally varying liquid-phase mass diffusivity in multicomponent droplet gasification  

SciTech Connect

The relative roles of liquid-phase diffusional resistance and volatility differential in multicomponent droplet gasification are revisited, recognizing that liquid-phase mass diffusivities can be substantially increased as the droplet is progressively heated upon initiation of gasification, leading to a corresponding substantial weakening of the diffusional resistance. Calculations performed using realistic and temperature-dependent thermal and mass diffusivities indeed substantiate this influence. In particular, the calculated results agree with the literature experimental data, indicating that the gasification mechanism of multicomponent fuels is intermediate between diffusion and distillation limits. Investigation was also performed on gasification at elevated pressures, recognizing that the liquid boiling point and hence the attainable droplet temperature would increase with increasing pressure, causing further weakening of the liquid-phase diffusional resistance. This possibility was again verified through calculated results, suggesting further departure from diffusion limit toward distillation limit behavior for gasification at high pressures. The study also found that diffusional resistance is stronger for the lighter, gasoline-like fuels as compared to the heavier, diesel-like fuels because the former have overall lower boiling points, lower attainable droplet temperatures, and hence lower mass diffusivities in spite of their lower molecular weights. (author)

Zhang, Huiqiang [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States); Department of Engineering Mechanics, Tsinghua University, Beijing, 100084 (China); Law, Chung K. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States)

2008-06-15

296

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

Microsoft Academic Search

The selectivity of Rhodococcus sp. strain JVH1 among selected sulfidic and thiophenic compounds was investigated in both single-liquid-phase (aqueous) cultures\\u000a and in two-liquid-phase cultures, where the sulfur compounds were dissolved in 2,2,4,4,6,8,8-heptamethylnonane as the immiscible\\u000a 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

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

2007-01-01

297

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

298

Application of MultiScale Hidden Markov Modeling Wavelet Coefficients to fMRI Activation Detection  

Microsoft Academic Search

Problem Statement: The problem of detection of functional magnetic resonance images (fMRIs), that is, to decide active and nonactive regions of human brain from fMRIs is studied in this paper. fMRI research is finding and will find more and more applications in diagnosing and treating brain diseases like depression and schizophrenia. At its initial stage fMRI detection are pixel-wise methods,

Fangyuan Nan; Yaonan Wang; Xiaoping Ma

2008-01-01

299

Liquid-phase cavity ring-down spectroscopy and its application as a chromatographic detector  

NASA Astrophysics Data System (ADS)

A new liquid-phase absorption detector is developed that demonstrates a minimum detectable absorbance of 10-8 absorbance units (AU). This value is more than 40 times lower than commercially available UV-Vis detectors. This new detector is a result of the extension of cavity ring-down spectroscopy (CRDS), a primarily gas-phase technique, to the liquid phase. Liquid-phase CRDS is accomplished by incorporating a specially designed flow cell into the ring-down cavity. The flow cell minimizes optical losses by allowing p-polarized light to refract through the cell interfaces at Brewster's angle. This flow cell has been coupled to the output of an HPLC separation, enabling the detection of analytes by CRDS. This technique was initially demonstrated by the separation and detection of a series of anthraquinones using a pulsed laser source at 470 nm. Ring-down time constants with the Brewster's angle flow cell, having an interior optical pathlength of 0.3 mm, were up to 2.5 mus in a 1-m cavity. The baseline noise level (rms) of this system was 3.2 x 10-6 AU, rivaling the best commercial UV-Vis detector, which exhibits a baseline noise of 3.0 x 10-6 AU. The CRDS detector performance, while notable, was limited in this case because of the nature of the light source: excitation of multiple cavity modes resulted in a 1% shot-to-shot variation in the ring-down time constant. The detection limit of the liquid-phase CRDS detector was improved through the use of a single-mode continuous-wave (cw) laser source at 488 nm. Its narrow linewidth enabled excitation of a single cavity mode, resulting in shot-to-shot variations in the ring-down time constant as low as 0.04%. Furthermore, through improved cell characterization, ring-down time constants with the same flow cell and cavity length were nearly 6 mus. The baseline noise (rms) for this system during an HPLC separation of the same analytes was 6.7 x 10-8 AU. These results clearly illustrate the value of liquid-phase CRDS and its use as an absorption detector for HPLC measurements.

Bechtel, Kate L.

300

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

301

Influence of heat treatment in air, and subsequent hydrothermal treatment in the liquid phase or water treatment in the liquid phase on a mixed Langmuir–Blodgett film of merocyanine dye-arachidic acid- n-octadecane ternary system  

Microsoft Academic Search

We have investigated the influence of heat treatment in air (HT), and subsequent hydrothermal treatment in the liquid phase (HTTL) or water treatment in the liquid phase (WTL) on the H-aggregate of mixed Langmuir–Blodgett (LB) films of merocyanine dye (MS18)-arachidic acid (C20)-n-octadecane (AL18) ternary system by means of polarized visible and IR absorption spectroscopy. The MS18 monomer is obtained from

Yoshiaki Hirano; Ari Maio; Akira Fukuda; Yasutaka Kitahama; Yukihiro Ozaki

2010-01-01

302

Modeling ATP protonation and activity coefficients in NaClaq and KClaq by SIT and Pitzer equations.  

PubMed

The acid-base properties of Adenosine 5'-triphosphate (ATP) in NaCl and KCl aqueous solutions at different ionic strengths (0activity isopiestic coefficients was performed, together with new potentiometric measurements (by ISE-H(+), glass electrode). Both literature and new experimental data were used to model the dependence on ionic strength and ionic medium of ATP protonation by SIT (Specific ion Interaction Theory) and Pitzer equations. In addition to values of first and second ATP protonation constants in NaCl(aq) and KCl(aq) at different ionic strengths, stability constants of NaATP(3-) and KATP(3-) complexes, SIT interaction coefficients and Pitzer parameters were calculated, together with protonation constants at infinite dilution: log (T)K(1)(H)=p(T)K(a2)=7.656+/-0.010 and log (T)K(2)(H)=p(T)K(a1)=4.561+/-0.006 (in the molar concentration scale, +/-95% confidence interval). Both SIT and Pitzer approaches give satisfactory results. PMID:16488529

De Stefano, Concetta; Milea, Demetrio; Pettignano, Alberto; Sammartano, Silvio

2006-02-20

303

Liquid-Phase Methanation/Shift Process Development. Final Technical Report, September 1, 1980-November 30, 1981.  

National Technical Information Service (NTIS)

This final technical report covers the work performed between September 1, 1980 and November 30, 1981 relating to Chem Systems' Liquid Phase Methanation/Shift Process. A total of 44 runs were completed covering testing of five commercially available catal...

1982-01-01

304

Experimental Evidence for Several Spheroid Growth Mechanisms in the Liquid-Phase Sintered Tungsten-Base Composites.  

National Technical Information Service (NTIS)

The generally accepted mechanism for spheroid growth during sintering of tungsten-base composites in the presence of a liquid phase is the dissolution of the small spheroids with simultaneous precipitation of tungsten from the molten matrix onto the large...

E. G. Zukas P. S. Z. Rogers R. S. Rogers

1976-01-01

305

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

306

INSEDELF: method of studying separation in liquid–liquid phase application to water–diesel fuel emulsions  

Microsoft Academic Search

The use of the INSEDELF method to measure solid–liquid phase separation was extended to water\\/diesel fuel emulsions to study liquid–liquid phase separation. We have demonstrated that this method is a pertinent tool for characterising the stability of these emulsions and for optimising complex formulations intended for winter use of these fuels. It permitted determination of the optimal content of antifreeze

P Schulz; L Dalix; J. M Letoffe; Y Faure

2004-01-01

307

Detection and quantification of antibodies to Newcastle disease virus in ostrich and rhea sera using a liquid phase blocking enzyme-linked immunosorbent assay.  

PubMed

A liquid phase blocking ELISA (LPB-ELISA) was adapted for the detection and quantification of antibodies to Newcastle disease virus. Sera from vaccinated and unvaccinated commercial flocks of ostriches (Struthio camelus) and rheas (Rhea americana) were tested. The purified and nonpurified virus used as the antigen and the capture and detector antibodies were prepared and standardized for this purpose. The hemagglutination-inhibition (HI) test was regarded as the reference method. The cutoff point for the LPB-ELISA was determined by a two-graph receiver operating characteristic analysis. The LPB-ELISA titers regressed significantly (P < 0.0001) on the HI titers with a high correlation coefficient (r = 0.875). The two tests showed good agreement (kappa = 0.82; P < 0.0001), relative sensitivity (90.91%) and specificity (91.18%), and accuracy (91.02%), suggesting that they are interchangeable. PMID:11063502

Moro de Sousa, R L; Montassier, H J; Pinto, A A

2000-11-01

308

Detection and Quantification of Antibodies to Newcastle Disease Virus in Ostrich and Rhea Sera Using a Liquid Phase Blocking Enzyme-Linked Immunosorbent Assay  

PubMed Central

A liquid phase blocking ELISA (LPB-ELISA) was adapted for the detection and quantification of antibodies to Newcastle disease virus. Sera from vaccinated and unvaccinated commercial flocks of ostriches (Struthio camelus) and rheas (Rhea americana) were tested. The purified and nonpurified virus used as the antigen and the capture and detector antibodies were prepared and standardized for this purpose. The hemagglutination-inhibition (HI) test was regarded as the reference method. The cutoff point for the LPB-ELISA was determined by a two-graph receiver operating characteristic analysis. The LPB-ELISA titers regressed significantly (P < 0.0001) on the HI titers with a high correlation coefficient (r = 0.875). The two tests showed good agreement (? = 0.82; P < 0.0001), relative sensitivity (90.91%) and specificity (91.18%), and accuracy (91.02%), suggesting that they are interchangeable.

de Sousa, Ricardo Luiz Moro; Montassier, Helio Jose; Pinto, Aramis Augusto

2000-01-01

309

The unusual importance of activity coefficients for micelle solutions illustrated by an osmometry study of aqueous sodium decanoate and aqueous sodium decanoate + sodium chloride solutions.  

PubMed

Freezing-point and vapor-pressure osmometry data are reported for aqueous sodium decanoate (NaD) solutions and aqueous NaD + NaCl solutions. The derived osmotic coefficients are analyzed with a mass-action model based on the micelle formation reaction qNa(+) + nD(-) = (Na(q)D(n))(q-n) and Guggenheim equations for the micelle and ionic activity coefficients. Stoichiometric activity coefficients of the NaD and NaCl components and the equilibrium constant for micelle formation are evaluated. Illustrating the remarkable but not widely appreciated nonideal behavior of ionic surfactant solutions, the micelle activity coefficient drops to astonishingly low values, below 10(-7) (relative to unity for ideal solutions). The activity coefficients of the Na(+) and D(-) ions, raised to large powers of q and n, reduce calculated extents of micelle formation by up to 15 orders of magnitude. Activity coefficients, frequently omitted from the Gibbs equation, are found to increase the calculated surface excess concentration of NaD by up to an order of magnitude. Inflection points in the extent of micelle formation, used to calculate critical micelle concentration (cmc) lowering caused by added salt, provide unexpected thermodynamic evidence for the elusive second cmc. PMID:22037556

Sharma, Poonam; MacNeil, Jennifer A; Bowles, Justine; Leaist, Derek G

2011-10-31

310

Calculation of the barometric coefficients at the start of the 24th solar activity cycle for particle detectors of Aragats Space Environmental Center  

NASA Astrophysics Data System (ADS)

After the major modernization of the data acquisition electronics of the particle detectors operated at Aragats Space Environmental Center (ASEC) calculations of the barometric coefficients of all the monitors were performed in the beginning of the 24th solar activity cycle. The barometric coefficients of particle detectors located at altitudes of 1000 m, 2000 m and 3200 m a.s.l. measuring various secondary cosmic ray fluxes were compared with theoretical expectations and monitors operated on different longitudes and latitudes. The barometric coefficients were also calculated for the several neutron monitors of recently established Eurasian database (NMDB) and SEVAN particle detector networks. The latitude and altitude dependencies of the barometric coefficients were investigated, as well as the dependence of coefficients on energy of the primary particles.

Chilingarian, A.; Karapetyan, T.

2011-04-01

311

Prediction of crystal-melt partition coefficients from elastic moduli  

Microsoft Academic Search

MANY geochemical processes, such as crystallization of silicate magmas or planetary differentiation, require a knowledge of the way in which elements become partitioned between coexisting crystal and liquid phases1,2. But quantitative prediction of crystal\\/melt partition coefficients from thermodynamic principles has not previously been possible. By studying the partitioning of 15 elements between silicate minerals and their coexisting melts, we show

Jon Blundy; Bernard Wood

1994-01-01

312

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

313

Quantum Control of Femtochemistry in the Gas Phase, Liquid Phase and on Surfaces  

NASA Astrophysics Data System (ADS)

By using coherent control techniques we control the behavior of quantum systems on their natural fs-time scale by applying ultrashort coherent light fields in the wavelength range from the IR to the UV. These laser pulses can be variably shaped in space and time using a laser pulse shaper consisting of a liquid-crystal display [1]. Laser-optimized femtochemistry in the gas phase and liquid phase is one field in which this new technique is successfully employed. Automated optimization of branching ratios and total product yields of gas phase photodissociation reactions as well as chemically selective molecular excitation in the liquid phase is performed [2][3]. Structural changes of a molecule in the liquid phase have been controlled by laser-optimized photoisomerization of a cyanine dye molecule [4] and of retinal in bacteriorhodopsin [5]. So far, optimal control techniques have been restricted to gas phase and condensed phase optimization experiments. Recently we have demonstrated femtosecond laser-assisted catalytic reactions on a Pd(100) single crystal surface. By applying a closed-loop optimal control scheme, we manipulate these reactions and selectively optimize the ratio of different bond-forming reaction channels, in contrast to previous quantum control experiments aiming at bond-cleavage. The results represent a first step towards selective photocatalysis of molecules. [1] T. Baumert et al, Appl. Phys. B 65, 779 (1997) [2] A. Assion et al, Science 282, 919(1998); T. Brixner et al, J. Mod. Opt. 50, 539 (2003) [3] T. Brixner et al, Nature, Vol. 414, 57 (2001) and J. Chem. Phys. 118, 3692 (2003) [4] G. Krampert et al, Phys. Rev. Lett. 94, 068305 (2005) [5] G. Vogt et al, Chem. Phys. Lett. 433, 211 (2006) P. Nuernberger et al, Phys. Chem. Chem. Phys. 9, 2470 (2007)

Gerber, Gustav

2008-03-01

314

Liquid-Liquid Phase Separation of a Surfactant-Solubilized Membrane Protein  

NASA Astrophysics Data System (ADS)

Solubilization of membrane proteins requires surfactants, whose structural properties play a crucial role in determining the protein phase behavior. We show that ionization of a pH-sensitive surfactant, lauryldymethylamino-N-oxide, bound to the bacterial photosynthetic Reaction Center, induces protein phase segregation in micrometric “droplets.” Liquid-liquid phase separation takes place in a narrow pH range, is promoted by increasing temperature, and vanishes by adding salt. After a fast initial droplet growth, the nearly arrested kinetics at a later stage leaves the system in a finely divided, long-lasting emulsified state.

Piazza, Roberto; Pierno, Matteo; Vignati, Emanuele; Venturoli, Giovanni; Francia, Francesco; Mallardi, Antonia; Palazzo, Gerardo

2003-05-01

315

Crystal growth of mode-stabilized semiconductor diode lasers by liquid-phase epitaxy  

NASA Astrophysics Data System (ADS)

A brief description of the liquid-phase epitaxial (LPE) process and the LPE growth equipment required for diode-laser fabrication is presented. Planar-geometry laser structures are described as a preamble to the treatment of complex mode-stabilized devices. LPE growth over nonplanar substrates is discussed and presented as the major technique for the fabrication of low- and high-power, single-mode, reliable diode lasers. Major types of single-mode AlGaAs/GaAs and InGaAsP/InP laser structures are also presented.

Botez, D.; Connolly, J. C.

1983-03-01

316

Crystal growth of mode-stabilized semiconductor diode lasers by liquid-phase epitaxy  

SciTech Connect

A brief description of the liquid-phase expitaxial (LPE) process and the LPE growth equipment required for diode-laser fabrication is presented. Planar-geometry laser structures are described as a preamble to the treatment of complex modestabilized devices. LPE growth over nonplanar substrates is discussed and presented as the major technique for the fabrication of low- and high-power, single-mode, reliable diode lasers. Major types of single-mode AIGaAs/GaAs and InGaAsP/ InP laser structures are also presented.

Botez, D.; Connolly, J.C.

1983-03-01

317

Heterogeneous liquid-phase hydration of isobutene by heteropoly acid–polymer composite film catalyst  

Microsoft Academic Search

H3PMo12O40-polymer composite film catalysts were prepared by blending these two materials using a methanol–chloroform mixture by a membrane\\u000a preparation technique. Polyphenylene oxide (PPO), polyethersulfone (PES) and polysulfone (PSF) were used as blending polymers.\\u000a A H3PMo12O40-PPO composite catalyst coated on Al2O3 was also prepared. These catalysts were used as heterogeneous catalysts for the liquid-phase tert-butanol (TBA) synthesis\\u000a from isobutene and water.

Seong Soo Lim; Yong Heon Kim; Gyo Ik Park; Wha Young Lee; In Kyu Song; Hyun Ki Youn

1999-01-01

318

Segregation to interphase boundaries in liquid-phase sintered tungsten alloys  

Microsoft Academic Search

Scanning Auger electron spectroscopy has been used to examine the distribution of impurity elements on the fracture surfaces\\u000a of liquid-phase sintered W-Ni-Cu and W-Ni-Fe alloys. On the interphase boundaries between the fcc Ni-based matrix phase and\\u000a the tungsten particles, segregation levels of ~0.4 and ~0.2 monolayers of phosphorus have been observed in as-sintered, furnace-cooled\\u000a specimens of W-Ni-Cu and W-Ni-Fe, respectively.

C. Lea; B. C. Muddle; D. V. Edmonds

1983-01-01

319

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

320

Liquid-Liquid Phase Transformation in Silicon: Evidence from First-Principles Molecular Dynamics Simulations  

NASA Astrophysics Data System (ADS)

We report results of first principles molecular dynamics simulations that confirm early speculations on the presence of liquid-liquid phase transition in undercooled silicon. However, we find that structural and electronic properties of both low-density liquid (LDL) and high-density liquid (HDL) phases are quite different from those obtained by empirical calculations, the difference being more pronounced for the HDL phase. The discrepancy between quantum and classical simulations is attributed to the inability of empirical potentials to describe changes in chemical bonds induced by density and temperature variations.

Jakse, N.; Pasturel, A.

2007-11-01

321

Liquid Phase Oxidation Grown Mism and Misim Switches by GaAs Native Oxides  

Microsoft Academic Search

Experimental predictions have been made for two-state bistable switching in both metal-GaAs native oxide-semiconductor-metal (MISM) and metal-GaAs native oxide-semiconductor-GaAs native oxide-metal (MISIM) structures for the first time, where the GaAs native oxides are formed by the liquid phase oxidation method. Bidirectional two-state switching (DIAC-like) and three-terminal operation are also shown in the photo-sensitive MISIM structure. Typical switching voltages for GaAs

Kao-Feng Yarn

2006-01-01

322

Voltammetric behavior of TiO 2 films on graphite electrodes prepared by liquid phase deposition  

Microsoft Academic Search

Electroactive TiO2 thin films were prepared on graphite electrodes from the aqueous solution of (NH4)2TiF6 and H3BO3 by the process of liquid phase deposition (LPD). By cyclic voltammetry, a cathodic peak assigned to the electroreduction of Ti(IV) species was exhibited in the voltammogram of LPD TiO2 film on graphite electrode in 0.2M phosphate buffer solution (PBS) at pH 6.0. The

Jingdong Zhang; Changzhu Yang; Gang Chang; Haiyun Zhu; Munetaka Oyama

2004-01-01

323

Growth of SiO 2 on InP substrate by liquid phase deposition  

Microsoft Academic Search

We have grown silicon dioxide (SiO2) on indium phosphorous (InP) substrate by liquid phase deposition (LPD) method. With inserting InP wafer in the treatment solution composed of SiO2 saturated hydrofluorosilicic acid (H2SiF6), 0.1M boric acid (H3BO3) and 1.74M diluted hydrochloric acid (HCl), the maximum deposition rate and refractive index for the as-grown LPD-SiO2 film were about 187.5Å\\/h and 1.495 under

Po Hsun Lei; Chyi Da Yang

2010-01-01

324

Low-temperature oxidation of SiGe by liquid-phase deposition  

Microsoft Academic Search

Low-temperature silicon dioxide (SiO2) films were grown on silicon germanium (SiGe) surfaces using the liquid-phase deposition (LPD) method. The growth solutions of LPD-SiO2 are hydrofluorosilicic acid (H2SiF6) and boric acid (H3BO3). It was found that the growth rate increases with increasing temperature and concentration of H3BO3. The Auger electron spectroscopy profile shows that no pileup of Ge atoms occurs at

Y. H. Chen; C. Y. Kung; J. D. Hwang; H. Y. Lin; H. J. Chan; P. S. Chen

2008-01-01

325

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

326

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

327

Methods for the immobilisation of hydroxyl-containing stationary liquid phases in capillary gas chromatography  

NASA Astrophysics Data System (ADS)

The main results concerning the immobilisation of hydroxyl-containing stationary phases in capillary gas chromatography are surveyed and treated systematically. Attention is concentrated on the influence of the chemical reactions occurring during immobilisation and on the characteristics of the capillary column. It is noted that, together with the improvement of the methods for the immobilisation of known phases, the syntheses of new stationary liquid phases, the properties and the immobilisation conditions of which have been optimised taking into account the characteristics of the objects analysed, are promising. The bibliography includes 176 references.

Mukhina, Vera P.; Berezkin, Viktor G.; Levin, Yakov A.

1998-12-01

328

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

SciTech Connect

The Liquid Phase Methanol (LPMEOEP") Demonstration Project at K.ingsport, 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 LPMEOHY Process Demonstration Unit is being built at a site located at the Eastman Chemical Company (Eastman) complex in Kingsport. On 4 October 1994, Air Products and Chemicals, Inc. (Air Products) and signed the agreements that would form the Partnership, secure the demonstration site, and provide the financial commitment and overall project management for the project. These partnership agreements became effective on 15 March 1995, when DOE authorized the commencement of Budget Period No. 2 (Mod. AO08 to the Cooperative Agreement). The Partnership has subcontracted with Air Products to provide the overall management of the project, and to act as the primary interface with DOE. As subcontractor to the Partnership, Air Products will also provide the engineering design, procurement, construction, and commissioning of the LPMEOHTM Process Demonstration Unit, and will provide the technical and engineering supervision needed to conduct the operational testing program required as part of the project. As subcontractor to Air Products, Eastman will be responsible for operation of the LPMEOHTM Process Demonstration Unit, and for the interconnection and supply of synthesis gas, utilities, product storage, and other needed sewices. The project involves the construction of an 80,000 gallons per day (260 tons-per-day (TPD)) methanol unit utilizing coal-derived synthesis gas fi-om Eastman's integrated coal gasification facility. The new equipment consists of synthesis gas feed preparation and compression facilities, the liquid phase reactor and auxiliaries, product distillation facilities, and utilities. The technology to be demonstrated is the product of a cooperative development effort by Air Products and DOE in a program that started in 1981. Developed to enhance electric power generation using integrated gasification combined cycle (IGCC) technology, the LPMEOHTM process is ideally suited for directly processing gases produced by modern day coal gasifiers. Originally tested at a small 3,200 gallons per day, DOE-owned experimental unit in LaPorte, Texas, the technology provides several improvements essential for the economic coproduction of methanol and electricity directly from gasified coal. This liquid phase process suspends fine catalyst particles in an inert liquid, forming a slurry. The slurry dissipates the heat of the chemical reaction away from the catalyst surface, protecting the catalyst and allowing the methanol synthesis reaction to proceed at higher rates.

None

1996-03-31

329

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

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

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

332

Mathematical Modeling and Simulation of Bubble Column Reactor for Aerial Liquid Phase Cyclohexane Oxidation  

NASA Astrophysics Data System (ADS)

Cyclohexane oxidation is an important but complex commercial reaction, wherein the desired product, K-A oil appears as an intermediates of the reaction sequence. A mathematical model has been developed for the bubble column reactor operating under isothermal conditions. The mass and energy model equations consisted of stiff ODEs. The model was applied to describe the behavior of bubble column reactor for aerial liquid phase cyclohexane oxidation. Effect of initial substrate concentration, catalyst loading and temperature was studied and discussed in detail. Conclusions were presented at the end of the study.

Upkare, Makarand M.; Rajurkar, Kalpendra B.; Gupta, Pankaj R.; Jaganathan, R.

2010-10-01

333

Mechanical properties of molybdenum alloyed liquid phase-sintered tungsten-based composites  

SciTech Connect

Tungsten-based composites are fabricated from mixed elemental powders using liquid phase sintering, usually with a nickel-iron matrix. During sintering, the tungsten undergoes grain growth, leading to microstructure coarsening that lowers strength but increases ductility. Often the desire is to increase strength at the sacrifice of ductility, and historically, this has been performed by postsintering deformation. Swaging a 93W-5Ni-2Fe alloy with 15 to 20 pct area reduction gives a 1000 to 1200 MPa tensile strength, 70 HRA hardness, and 15 to 20 pct fracture elongation.

Kemp, P.B.; German, R.M.

1995-08-01

334

[Improved production of microbial lipids in the two-liquid phase fermentation system].  

PubMed

In the present study, we developed a two-liquid phase fermentation system by adding 1% n-dodecane as oxygen-vector to enhance the microbial lipids productivity of Trichosporon fermentans using cassava starch hydrolysate. Results suggest that the oxygen-vector could alleviate the oxygen shortage in flask fermentation. The cell mass and lipids concentration were 101.2 g/L and 50.28 respectively in 2 L fermenter with the presence of 1% n-dodecane. Additionally, gas chromatography analysis also reveals that the microbial lipids produced by T. fermentans contained a higher percentage of saturated fatty acid in the oxygen-vector case. PMID:23894827

Yan, Riming; Ai, Zuozuo; Wang, Ya; Zhang, Zhibin; Zeng, Qinggui; Du, Zhu

2013-04-01

335

Processing of iron-titanium powder mixtures by transient liquid phase sintering  

NASA Astrophysics Data System (ADS)

Transient liquid phase sintering was examined for Fe-Ti powder mixtures. The experimental plan included the effects of several processing variables, such as green density, particle size, composition, heating rate, sintering temperature, and sintering time. During heating, pores form at the Ti particle sites. At the first eutectic temperature (1085 °C), liquid spreading is inhibited by a surrounding intermetallic envelope, leading to swelling. At the second eutectic temperature (1289 °C), the liquid penetrates along the iron grain boundaries and provides densification. The amount of densification depends on the amount of liquid formed at the second eutectic temperature and its duration as determined by the titanium content and heating rate.

German, R. M.; Dunlap, J. W.

1986-02-01

336

Communication: Protein dynamical transition vs. liquid-liquid phase transition in protein hydration water  

NASA Astrophysics Data System (ADS)

In this work, we compare experimental data on myoglobin hydrated powders from elastic neutron scattering, broadband dielectric spectroscopy, and differential scanning calorimetry. Our aim is to obtain new insights on the connection between the protein dynamical transition, a fundamental phenomenon observed in proteins whose physical origin is highly debated, and the liquid-liquid phase transition (LLPT) possibly occurring in protein hydration water and related to the existence of a low temperature critical point in supercooled water. Our results provide a consistent thermodynamic/dynamic description which gives experimental support to the LLPT hypothesis and further reveals how fundamental properties of water and proteins are tightly related.

Schirò, Giorgio; Fomina, Margarita; Cupane, Antonio

2013-09-01

337

Modification of the Pitzer model to calculate the mean activity coefficients of electrolytes in a water-alcohol mixed solvent solution  

Microsoft Academic Search

The approach tested in this work consists in adapting the Pitzer model, initially designed for aqueous solutions of electrolytes, to the case of solutions with a mixed solvent, without systematically readjusting the coefficients. This modified model was applied successfully to the calculation of the mean activity coefficients of NaBr in the mixed solvent H2O+MeOH, H2O+EtOH and compared with the experimental

S. Ye; P. Xans; B. Lagourette

1994-01-01

338

Activity coefficients at infinite dilution and physicochemical properties for organic solutes and water in the ionic liquid 1-(3-hydroxypropyl)pyridinium bis(trifluoromethylsulfonyl)-amide  

Microsoft Academic Search

The activity coefficients at infinite dilution, ?13? and gas–liquid partition coefficients, KL for 46 solutes: alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, thiophene, ethers, ketones, acetic acid, and water in the ionic liquid 1-(3-hydroxypropyl)pyridinium bis(trifluoromethylsulfonyl)-amide were determined by gas–liquid chromatography at the temperatures from (308.15 to 378.15)K. The partial molar excess Gibbs free energies ?G1E,?, enthalpies ?H1E,? and entropies ?S1E,?

Andrzej Marciniak

2011-01-01

339

Determination of selected pesticides in environmental water by employing liquid-phase microextraction and liquid chromatography-tandem mass spectrometry.  

PubMed

An optimised extraction and cleanup method for the analysis of pesticide in natural water samples is presented. Sixteen pesticides of different polarity and from the different chemical classes (organophosphates, triazines, benzimidazoles, carbamates, carbamides, neonicotinoides, methylureas, phenylureas and benzohydrazides), most frequently used in Serbia, were selected for the analysis. Liquid-phase microextraction in a single hollow fibre (HF-LPME) has been applied for sample preparation. The concentrations of pesticides were determined using HPLC-MS/MS method with electrospray ionisation. The extraction behaviour and selection of the experimental conditions was predicted based on log D and pK(a) values of targeted pesticides, which were calculated applying the computer software ACD/Labs PhysChem Suite v12. The influence of the donor pH and concentration of pesticides, organic phase composition as well as the extraction time on the extraction efficiency was investigated. Optimum extraction conditions were evaluated with respect to the investigated parameters of the extraction. The extraction method was validated for 10 out of 16 studied pesticides. Linear range of the pesticides was 0.1-5 microg L(-1) with the correlation coefficient from 0.991 to 0.9998, and the relative standard deviation for three standard measurements was between 0.2 and 11.8%. The limits of detections ranged from 0.026 to 0.237 microg L(-1) and the limits of quantifications from 0.094 to 0.793 microg L(-1). The optimised two-phase HF-LPME method was successfully applied for determination of moderately polar as well low-polar pesticides in the environmental water samples. PMID:20442990

Trti?-Petrovi?, Tatjana; Dordevi?, Jelena; Dujakovi?, Nikolina; Kumri?, Ksenija; Vasiljevi?, Tatjana; Lausevi?, Mila

2010-05-05

340

Production of the Biopesticide Azadirachtin by Hairy Root Cultivation of Azadirachta indica in Liquid-Phase Bioreactors.  

PubMed

Batch cultivation of Azadirachta indica hairy roots was carried out in different liquid-phase bioreactor configurations (stirred-tank, bubble column, bubble column with polypropylene basket, and polyurethane foam disc as root supports) to investigate possible scale-up of the A. indica hairy root culture for in vitro production of the biopesticide azadirachtin. The hairy roots failed to grow in the conventional bioreactor designs (stirred tank and bubble column). However, modified bubble column reactor (with polyurethane foam as root support) configuration facilitated high-density culture of A. indica hairy roots with a biomass production of 9.2 g l(-1)dry weight and azadirachtin yield of 3.2 mg g(-1) leading to a volumetric productivity of azadirachtin as 1.14 mg l(-1) day(-1). The antifeedant activity in the hairy roots was also evaluated by no choice feeding tests with known concentrations of the hairy root powder and its solvent extract separately on the desert locust Schistocerca gregaria. The hairy root powder and its solvent extract demonstrated a high level of antifeedant activity (with an antifeedant index of 97 % at a concentration of 2 % w/v and 83 % at a concentration of 0.05 % (w/v), respectively, in ethanol). PMID:23955295

Srivastava, Smita; Srivastava, Ashok K

2013-08-17

341

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

2011-09-05

342

Study on anisotropy of effective diffusion coefficient and activation energy for deuterated water in compacted sodium bentonite.  

PubMed

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 D(e) 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 D(e) and the anisotropy for HDO were in good accordance with previously reported results for tritiated water at room temperature. Activation energies of D(e) 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. PMID:14698869

Suzuki, Satoru; Sato, Haruo; Ishidera, Takamitsu; Fujii, Naoki

2004-01-01

343

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

344

Selective epitaxial growth of GaAs by current controlled liquid phase epitaxy  

NASA Astrophysics Data System (ADS)

Selective epitaxial growth of Te-doped GaAs on circularly patterned GaAs (100) substrate was investigated by liquid phase epitaxy (LPE) and current controlled liquid phase epitaxy (CCLPE). SiNx was used as a mask layer to fabricate circular windows on the substrate and the effect of various growth periods and current densities on the growth morphology were investigated. A truncated pyramid like structure with a vertical thickness of 337 ?m and a lateral thickness of 268 ?m was achieved on the circularly patterned substrate at 6 h growth with an applied current density of 20 A cm-2. The vertical growth was increased almost one order and lateral growth was increased up to nine times compared to standard LPE growth. The growth step density was higher at window walls and it caused relatively higher growth compared to its centre. The surface morphology and selective epitaxial growth were greatly improved by an applied DC electric current. The dislocation density of the grown epilayer was significantly reduced when compared with that of the substrate. Solute transport in the solution was enhanced by the electromigration of solute by an electric current, which enhanced growth in vertical and lateral directions.

Mouleeswaran, D.; Koyama, T.; Tanaka, A.; Hayakawa, Y.

2013-01-01

345

Rapid liquid phase epitaxial growth studies of GaAs: Final report, July 1984-June 1987  

SciTech Connect

Single crystal layers of gallium arsenide have been grown on (111) and (100) oriented GaAs substrates from a flowing, GaAs saturated, gallium solution with a few degrees temperature differential across the liquid/solid interface. Very high growth rates, on the order of 8..mu..m per minute, have been observed. Such rates are in agreement with the growth theory developed as part of this program, and are about two orders greater than those typically achieved in conventional, static solution, liquid phase epitaxy. Both undoped and p-doped (Si) GaAs layers have been grown and some of their material properties measured. Good crystallinity was inferred from the narrowness of x-ray diffraction lines and from the intensities of the photoluminescence responses of all specimens sampled. While these results do not prove that the epi material is of photovoltaic quality, they indicate both a high crystallographic perfection and a low density of life-time poisoning impurities; conditions which are usually necessary for PV device development. Thus far, smooth surfaces have not been produced directly by the rapid liquid phase epitaxy (RLPE) process. The rough surface morphologies are due, at least in part, to incomplete wipe off of the liquid when the substrate is withdrawn at the end of the growth cycle. Another potential source is growth instabilities which will be discussed later. This report summarizes the three year research program of the RLPE process sponsored by DOE-SOLERAS.

Gerritsen, H.J.; Crisman, E.E.

1987-01-01

346

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

347

Metallic non-Fermi-liquid phases of an extended Hubbard model in infinite dimensions  

SciTech Connect

We study an extended Hubbard model in the limit of infinite dimensions and its zero-dimensional counterpart, a generalized asymmetric Anderson model. In the impurity model we find three kinds of mixed valence states: (a) the usual strong-coupling state in which a resonance forms at the Fermi level; (b) a weak-coupling state in which neither the impurity spin nor the impurity charge degrees of freedom are quenched; and (c) an intermediate-coupling state where the spin but not the charge degree of freedom is quenched. The corresponding phases of the extended Hubbard model in infinite dimensions are (a) a Fermi liquid; (b) a non-Fermi-liquid state with incoherent charge and spin excitations; and (c) a non-Fermi-liquid state with incoherent charge but coherent spin excitations. The non-Fermi-liquid phases are incoherent metallic states with vanishing quasiparticle residue, self-similar local correlation functions, and asymptotically decoupled charge and spin excitations. The non-Fermi-liquid phases occur for a wide range of parameters.

Si, Q.; Kotliar, G. (Serin Physics Laboratory, Rutgers University, Piscataway, New Jersey 08855-0849 (United States))

1993-11-01

348

Relationship between the liquid liquid phase transition and dynamic behaviour in the Jagla model  

NASA Astrophysics Data System (ADS)

Using molecular dynamics simulations, we study a spherically symmetric 'two-scale' Jagla potential with both repulsive and attractive ramps. This potential displays a liquid-liquid phase transition with a positively sloped coexistence line ending at a critical point well above the equilibrium melting line. We study the dynamic behaviour in the vicinity of this liquid-liquid critical point. Below the critical point, we find that the dynamics in the more ordered high density liquid (HDL) are much slower then the dynamics in the less ordered low density liquid (LDL). Moreover, the behaviour of the diffusion constant and relaxation time in the HDL phase follows approximately an Arrhenius law, while in the LDL phase the slope of the Arrhenius fit increases upon cooling. Above the critical pressure, as we cool the system at constant pressure, the behaviour of the dynamics smoothly changes with temperature. It resembles the behaviour of the LDL at high temperatures and resembles the behaviour of the HDL at low temperatures. This dynamic crossover happens in the vicinity of the Widom line (the extension of the coexistence line into the one-phase region) which also has a positive slope. Our work suggests a possible general relation between a liquid-liquid phase transition and the change in dynamics.

Xu, Limei; Ehrenberg, Isaac; Buldyrev, Sergey V.; Stanley, H. Eugene

2006-09-01

349

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

350

Protein Phase Behavior in Aqueous Solutions: Crystallization, Liquid-Liquid Phase Separation, Gels, and Aggregates  

PubMed Central

The aggregates and gels commonly observed during protein crystallization have generally been considered disordered phases without further characterization. Here their physical nature is addressed by investigating protein salting-out in ammonium sulfate and sodium chloride for six proteins (ovalbumin, ribonuclease A, soybean trypsin inhibitor, lysozyme, and ?-lactoglobulin A and B) at 4°C, 23°C, and 37°C. When interpreted within the framework of a theoretical phase diagram obtained for colloidal particles displaying short-range attractive interactions, the results show that the formation of aggregates can be interpreted theoretically in terms of a gas-liquid phase separation for aggregates that are amorphous or gel-like. A notable additional feature is the existence of a second aggregation line observed for both ovalbumin and ribonuclease A in ammonium sulfate, interpreted theoretically as the spinodal. Further investigation of ovalbumin and lysozyme reveals that the formation of aggregates can be interpreted, in light of theoretical results from mode-coupling theory, as a kinetically trapped state or a gel phase that occurs through the intermediate of a gas-liquid phase separation. Despite the limitations of simple theoretical models of short-range attractive interactions, such as their inability to reproduce the effect of temperature, they provide a framework useful to describe the main features of protein phase behavior.

Dumetz, Andre C.; Chockla, Aaron M.; Kaler, Eric W.; Lenhoff, Abraham M.

2008-01-01

351

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

NASA Astrophysics Data System (ADS)

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 gravity and sedimentation. During the first minute sintering period the particles in the agglomerates were separated and the particle distribution became even. The particle growth rate under microgravity, initially high, is slowing down. At further studies under gravity the influence of surface energy between the liquid phase and the tungsten particles have been investigated. Additions of sulphur and cobolt were used to decrease the surface energy and the use of nickel without iron to increase the energy. At a high surface energy the growth rate increases due to increased driving force. Preliminary results from the Texus 26 flight (April 90) are included.

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

352

Liquid phase sintering of tungsten composites in space: Results of tests performed in Texus  

NASA Astrophysics Data System (ADS)

Tungsten-nickel-iron composites are commersially fabricated from powders by liquid phase sintering. They consist of almost spherical tungsten particles in a matrix of nickel-iron-tungsten. A way to contribute to the understanding of the sintering mechanism and the mechanical properties is to study composites with a low amount of tungsten particles. Depending on the great difference in density between the particles and the matrix, this can only be done under microgravity. A primary sintering test of the tungsten composite was done in space using the Texus 10 modul. Prealloys were fabricated from metal powder mixtures, which were hot isostatic pressed. Liquid phase sintering of the two tungsten composites under microgravity has shown that the particles are evenly distributed and that no segregation occured due to convection. Despite an uneven distribution of the particles in the preformed specimens and the short melting period the patricle distribution has become even. Compared to short time sintering tests made on four alloys in the laboratory, the growth and separation of the particles was fast.

Ekbom, Lars B.; Eliasson, Anders

353

Densification during the supersolidus liquid-phase sintering of nickel-based prealloyed powder mixtures  

SciTech Connect

This article examines densification during supersolidus liquid-phase sintering (SLPS) of a mixture of two nickel-based prealloyed powders. The two powders were of similar compositions, where one powder alloyed with boron had a lower melting-temperature range than the other. Sintering of such binary powder systems is performed at temperatures above the solidus of the low-melting powder, to form a liquid phase that promotes densification. Measurements of shrinkage, sintered density, and melting were used to determine the densification mechanism. An increase in the fraction of the high-melting powder resulted in retardation of sintering. A densification model based on viscous flow as developed using rheological principles. The model is a first step in the extension of the conventional models of densification of single prealloyed powders to ones of mixtures of prealloyed powders. It incorporates the effects of homogenization between the two powders, specifically, the diffusion of boron from the low-melting to the high-melting powder. The densification of the powder mixture was found to depend on the extent of melting of the low-melting powder and the fraction of the high-melting powder.

Lal, A.; Iacocca, R.G.; German, R.M. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Engineering Science and Mechanics

1999-08-01

354

Commercial-scale demonstration of a liquid-phase methanol process  

SciTech Connect

The Eastman Chemical Company operates a coal gasification complex in Kingsport, Tennessee. The primary output of this plant is carbonylation-derived acetic anhydride. The required methyl acetate is made from methanol and acetic acid. Methanol is currently produced from syngas by a gas-phase process, which must receive stoichiometric quantities of carbon monoxide and hydrogen to avoid overheating the catalyst. Control of this CO/H{sub 2} ratio is accomplished with a shift reactor. A liquid-phase methanol process (LPMEOH{trademark}) has been developed by Air Products. Efficient heat removal permits the direct use of syngas without the need for the shift reactor. An Air Products/Eastman joint venture, with partial funding from the Department of Energy under the Clean Coal Technology Program, has been formed to build a demonstration-scale liquid-phase methanol plant. This talk will focus on the unique features of this plant and how it will be integrated into the existing facilities.

Cook, S.L. [Eastman Chemical Co., Kingsport, TN (United States)

1995-12-31

355

Liquid-phase study of ozone inactivation of Venezuelan equine encephalomyelitis virus.  

PubMed Central

Ozone, in a liquid-phase application, was evaluated as a residue-free viral inactivant that may be suitable for use in an arboviral research laboratory. Commonly used sterilizing agents may leave trace residues, be flammable or explosive, and require lengthy periods for gases or residues to dissipate after decontamination of equipment such as biological safety cabinets. Complete liquid-phase inactivation of Venezuelan equine encephalomyelitis virus was attained at 0.025 mg of ozone per liter within 45 min of exposure. The inactivation of 10(6.5) median cell culture infective doses (CCID50 of Venezuelan equine encephalomyelitis virus per milliliter represented a reduction of 99.99997% of the viral particles from the control levels of 10(7.25-7.5) CCID50/ml. A dose-response relationship was demonstrated. Analysis by polynomial regression of the logarithmic values for both ozone concentrations and percent reduction of viral titers had a highly significant r2 of 0.8 (F = 63.6; df = 1, 16). These results, together with those of Akey (J. Econ. Entomol. 75:387-392, 1982) on the use of ozone to kill a winged arboviral vector, indicate that ozone is a promising candidate as a sterilizing agent in some applications for biological safety cabinets and other equipment used in vector studies with arboviruses.

Akey, D H; Walton, T E

1985-01-01

356

One-Step Liquid-Phase Synthesis of Carbon Nanotubes with Catalyst Precursors of Organometallic Complexes  

NASA Astrophysics Data System (ADS)

This paper describes a simple, low cost one-step liquid-phase process for the synthesis of highly aligned carbon nanotube (CNT) arrays (HACNTAs). Highly pure HACNTAs were grown on a stainless steel substrate by resistance-heating in methanol solution containing one of the organometallic complex catalyst precursors, ferrocene Fe(C5H5)2 and iron pentacarbonyl Fe(CO)5. Effects of the catalyst precursors on the formation and morphologies of HACNTAs were examined. A small amount of non-aligned multi-walled CNTs (MWCNTs) were grown from 1 mM Fe(C5H5)2 methanol solution. Highly pure HACNTAs composed of MWCNTs were readily grown from 10 and 40 mM Fe(C5H5)2 methanol solutions by this one-step liquid-phase process. From the Fe(CO)5 methanol solution, HACNTAs were prepared even at a very low Fe(CO)5 concentration of 0.01 mM, which was about 1/1000 lower than that of Fe(C5H5)2. The optimal low concentration is attributed to the low decomposition temperature of Fe(CO)5.

Yamagiwa, Kiyofumi; Kikitsu, Tomoka; Yamashita, Shunsuke; Kuwano, Jun

2011-01-01

357

Molecular determinants for the line tension of coexisting liquid phases in monolayers.  

PubMed

The line tension (?) in biphasic membranes has been determined in monolayers and bilayers using a variety of techniques. In this work we present a novel approach to the determination of ? in monolayers with liquid/liquid phase coexistence, overcoming several of the drawbacks of current techniques. Using our method, we determined the line tension of liquid/liquid phases in binary mixtures of different lipids and a molecule similar to cholesterol but less oxidizable. We analyzed the effect of the hydrocarbon chain length and the polar head-group of the non-sterol lipid and found the latter to exert much more influence than the former. The presence of PE led to high ? values, PG to low values and PS and PC to intermediate values. The line tension showed a strong correlation with the critical packing parameter of the phospholipid. The spontaneous curvature displayed by the phases constituted by a particular lipid appears to be an important parameter for determining the line tension in mixed films. PMID:22982729

Bischof, Andrea Alejandra; Wilke, Natalia

2012-09-12

358

Investigation of metal-matrix composite containing liquid-phase dispersion  

NASA Astrophysics Data System (ADS)

Al-Pb binary system is a suitable model system for testing liquid phase dispersion strengthening in bulk materials for structural applications. Liquid Pb islands can be finely dispersed in still solid Al matrix due to the substantial difference of melting points. The Al-Pb system prepared by means of Equal Channel Angular Pressing (ECAP) process was investigated by Small-Angle Neutron Scattering technique (SANS) which enables in-situ measurement of size and morphology parameters of Pb inclusions at elevated temperatures. It was observed that the lead particles were elongated roughly in the direction of ECAP. During the subsequent in-situ thermal cycle RT-400°C-RT, the elongated Pb particles transformed to nearly spherical shape. The change of scattering contrast during melting of Pb mapped the transform of the confined lead particles to the liquid phase. The center of the transition region is around 342°C (615K) for both the as-cast and the ECAP deformed samples, which is a significant shift with respect to the free Pb melting point 327°C (600K). For the ECAP sample, the transition is not sharp, indicating a broad size distribution of lead particles.

Strunz, P.; Mukherji, D.; Gilles, R.; Geue, T.; Rösler, J.

2012-02-01

359

Characterization of Liquid Phase Sitered sic and Sic/sic Composite Materials  

NASA Astrophysics Data System (ADS)

The characterization of liquid phase sintered(LPS) SiC based materials has been investigated with the analysis of microstructure and flexural strength. Especially, LPS-SiC materials were examined for the variation of test temperature and composition ratios (Al2O3,/Y2O3) of sintering additives. LPS-SiC based materials were fabricated by hot pressing(HP) associated with the liquid phase formation of sintering additives(Al2O3,Y2O3). LPS-SiCf/SiC composites were also fabricated with plane-woven(PW) Tyranno-SA fibers without an interfacial layer. LPS-SiC materials showed a dense morphology with the creation of the secondary phase like YAG. The composition ratio of sintering additives led to the variation of sintered density and flexural strength. The flexural strength of LPS-SiC materials was greatly decreased at the temperature higher than 1000°C. LPS-SiCf/SiC composites represented an average flexural strength of about 260 MPa, accompanying the catastrophic fracture behavior without any full-out phenomena.

Lee, Moon Hee; Lee, Sang Pill; Hur, Kwan Do

360

Membrane separation in green chemical processing: solvent nanofiltration in liquid phase organic synthesis reactions.  

PubMed

This paper describes ideas together with preliminary experimental results for applying solvent nanofiltration to liquid phase organic synthesis reactions. Membranes for organic solvent nanofiltration have only recently (during the 1990s) become available and, to date, have been applied primarily to food processing (vegetable oil processing, in particular) and refinery processes. Applications to organic synthesis, even at a laboratory feasibility level, are few. However, these membranes have great potential to improve the environmental performance of many liquid phase synthesis reactions by reducing the need for complex solvent handling operations. Examples that are shown to be feasible are solvent exchanges, where it is desired to swap a high molecular weight molecule from one solvent to another between separate stages in a complex synthesis, and recycle and reuse of homogeneous catalysts. In solvent exchanges, nanofiltration is shown to provide a fast and effective means of swapping from a high boiling point solvent to a solvent with a lower boiling point-this is a difficult operation by means of distillation. Solvent nanofiltration is shown to be able to separate two distinct types of homogeneous catalysts, phase transfer catalysts and organometallic catalysts, from their respective reaction products. In both cases the application of organic solvent nanofiltration allows several reuses of the same catalyst. Catalyst stability is shown to be an essential requirement for this technique to be effective. Finally, we present a discussion of scale-up aspects including membrane flux and process economics. PMID:12783814

Livingston, Andrew; Peeva, Ludmila; Han, Shejiao; Nair, Dinesh; Luthra, Satinder Singh; White, Lloyd S; Freitas Dos Santos, Luisa M

2003-03-01

361

Commercial-scale demonstration of the liquid phase methanol (LPMEOH{trademark}) process. Technical progress report No. 3, October 1, 1994--March 31, 1995  

SciTech Connect

The Liquid Phase Methanol (LPMEOH{trademark}) demonstration project at Kingsport, Tennessee is a $213.7 million cooperative agreement between the US Department of Energy (DOE) and Air Products Liquid Phase Conversion Company, L.P. (the Partnership). A facility producing 260 TPD of methanol will be designed and constructed at a site located at the Eastman Chemical complex in Kingsport, Tennessee. The Partnership will own and operate the facility for the four-year demonstration facility operational period. This project is sponsored under the DOE`s Clean Coal Technology Program, and its primary objective is to ``demonstrate the production of methanol using the LPMEOH{trademark} process in conjunction with an integrated coal gasification facility.`` The project will also demonstrate the suitability of the methanol produced for use as a chemical feedstock or as a low sulfur dioxide, low nitrogen oxides alternative fuel in stationary and transportation applications. The project may also demonstrate the production of dimethyl ether (DME) as a mixed coproduct with methanol, if laboratory- and pilot-scale research shows promising results. If implemented, the DME would be produced during the last six months of the operations phase. During the period 1 October 1994 to 31 March 1995, the project team completed essentially all the activities necessary to start detailed design. Major accomplishments in these activities are discussed.

NONE

1995-12-31

362

Thermodynamics of concentrated electrolyte mixtures. 9. Activity coefficients in aqueous NaBr-CaBr/sub 2/ mixtures at 25 /sup 0/C  

SciTech Connect

The activity coefficients of NaBr and CaBr/sub 2/ in NaBr-CaBr/sub 2/ aqueous mixtures have been measured at 25/sup 0/C over the ranges of ionic strengths 0.1 to 7.5 m. The measurements were made with a dual electrometer amplifier using Na and Ca ion selective electrodes against a Br ion selective electrode. The data were fitted to Harned's equation of the form log ..gamma../sub i/ = log ..gamma../sub i//sup 0/ - ..cap alpha../sub AB/y/sub B/ - ..beta../sub AB/y/sub B//sup 2/ to compute the trace activity coefficients and were also analyzed by using the Pitzer formation. Deviations from the Pitzer formalism were observed for the experimental activity coefficients in this mixture.

Usha, A.V.; Raju, K.; Atkinson, G.

1987-08-27

363

Kinetics of the liquid-phase hydrogenation of benzene and some monosubstituted alkylbenzenes over a nickel catalyst  

SciTech Connect

The liquid-phase hydrogenation kinetics of benzene and three monosubstituted alkylbenzenes, toluene, ethylbenzene, and cumene, was determined in a semibatch reactor operating at hydrogen pressures of 20--40 atm and at temperatures of 95--125 C. Commercial preactivated catalyst particles of nickel-alumina were used in all experiments. The hydrogenation activity of the compounds decreased in the order benzene {much_gt} toluene > ethylbenzene > cumene. The main reaction product was always the completely hydrogenated cycloalkane, whereas only trace amounts of cycloalkenes were detected. The hydrogenation rates had a slow initial period followed by a period of a virtually constant rate, which decreased at the end of the reaction. The analysis of the data with a reaction-diffusion model revealed that the kinetics was influenced by pore diffusion. Rate equations based on a sequential addition mechanism of adsorbed hydrogen to the aromatic nucleus were derived, and the kinetic parameters were estimated from the reaction-diffusion model with nonlinear regression analysis. The rate equations were able to describe all the features of the experimental data.

Toppinen, S.; Salmi, T. [Aabo Akademi (Finland). Lab. of Industrial Chemistry; Rantakylae, T.K. [Univ. of Oulu (Finland). Dept. of Process Engineering; Aittamaa, J. [Neste Engineering, Porvoo (Finland)

1996-06-01

364

Mechanisms of bacterial inactivation in the liquid phase induced by a remote RF cold atmospheric pressure plasma jet  

NASA Astrophysics Data System (ADS)

A radio-frequency atmospheric pressure argon plasma jet is used for the inactivation of bacteria (Pseudomonas aeruginosa) in solutions. The source is characterized by measurements of power dissipation, gas temperature, absolute UV irradiance as well as mass spectrometry measurements of emitted ions. The plasma-induced liquid chemistry is studied by performing liquid ion chromatography and hydrogen peroxide concentration measurements on treated distilled water samples. Additionally, a quantitative estimation of an extensive liquid chemistry induced by the plasma is made by solution kinetics calculations. The role of the different active components of the plasma is evaluated based on either measurements, as mentioned above, or estimations based on published data of measurements of those components. For the experimental conditions being considered in this work, it is shown that the bactericidal effect can be solely ascribed to plasma-induced liquid chemistry, leading to the production of stable and transient chemical species. It is shown that HNO2, ONOO- and H2O2 are present in the liquid phase in similar quantities to concentrations which are reported in the literature to cause bacterial inactivation. The importance of plasma-induced chemistry at the gas-liquid interface is illustrated and discussed in detail.

van Gils, C. A. J.; Hofmann, S.; Boekema, B. K. H. L.; Brandenburg, R.; Bruggeman, P. J.

2013-05-01

365

EFFECTS OF COVAPORS ON ADSORPTION RATE COEFFICIENTS OF ORGANIC VAPORS ADSORBED ONTO ACTIVATED CARBON FROM FLOWING AIR  

SciTech Connect

Published breakthrough time, adsorption rate, and capacity data for components of organic vapor mixtures adsorbed from flows through fixed activated carbon beds have been analyzed. Capacities (as stoichiometric centers of constant pattern breakthrough curves) yielded stoichiometric times {tau}, which are useful for determining elution orders of mixture components. We also calculated adsorption rate coefficients k{sub v} of the Wheeler (or, more general Reaction Kinetic) breakthrough curve equation, when not reported, from breakthrough times and {tau}. Ninety-five k{sub v} (in mixture)/ k{sub v} (single vapor) ratios at similar vapor concentrations were calculated and averaged for elution order categories. For 43 first-eluting vapors the average ratio (1.07) was statistically no different (0.21 standard deviation) than unity, so that we recommend using the single-vapor k{sub v} for such. Forty-seven second-eluting vapor ratios averaged 0.85 (0.24 standard deviation), also not significantly different from unity; however, other evidence and considerations lead us recommend using k{sub v} (in mixture) = 0.85 k{sub v} (single vapor). Five third- and fourth-eluting vapors gave an average of 0.56 (0.16 standard deviation) for a recommended k{sub v} (in mixture) = 0.56 k{sub v} (single vapor) for such.

G. WOOD

2000-12-01

366

Isopiestic determination of the osmotic and activity coefficients of aqueous mixtures of NaCl and MgCl/sub 2/ at 25/sup 0/C  

SciTech Connect

The osmotic and activity coefficients of aqueous mixtures of NaCl and MgCl/sub 2/ have been determined at 25/sup 0/C by using the isopiestic method. These measurements extend from low concentrations to the crystallization limits of the mixtures. They are critically compared to published isopiestic, direct vapor pressure, and emf data for this system. The data agree well with previous isopiestic data and two sets of emf values, but direct vapor pressure data are significantly discrepant. Osmotic and activity coefficients for NaCl-MgCl/sub 2/ mixtures are fairly reliably represented by both Pitzer's equations and Scatchard's neutral electrolyte equations.

Rard, J.A.; Miller, D.G.

1987-01-01

367

Template-assisted mineral formation via an amorphous liquid phase precursor route  

NASA Astrophysics Data System (ADS)

The search for alternative routes to synthesize inorganic materials has led to the biomimetic route of producing ceramics. In this method, materials are manufactured at ambient temperatures and in aqueous solutions with soluble additives and insoluble matrix, similar to the biological strategy for the formation of minerals by living organisms. Using this approach, an anionic polypeptide additive was used to induce an amorphous liquid-phase precursor to either calcium carbonate or calcium phosphate. This precursor was then templated on either organic or inorganic substrates. Non-equilibrium morphologies, such as two-dimensional calcium carbonate films, one-dimensional calcium carbonate mesostructures and "molten" calcium phosphate spherulites were produced, which are not typical of the traditional (additive-free) solution grown crystals in the laboratory. In the study of calcium carbonate, the amorphous calcium carbonate mineral formed via the liquid-phase precursor, either underwent a dissolution-recrystallization event or a pseudo-solid-state transformation to produce different morphologies and polymorphs of the mineral. Discrete or aggregate calcite crystals were formed via the dissolution of the amorphous phase to allow the reprecipitation of the stable crystal. Non-equilibrium morphologies, e.g., films, mesotubules and mesowires were templated using organic and inorganic substrates and compartments. These structures were generated via an amorphous solid to crystalline solid transformation. Single crystalline tablets and mesowires of aragonite, which are reported to be found only in nature as skeletal structures of marine organisms, such as mollusk nacre and echinoderm teeth, were successfully synthesized. These biomimetic structures were grown via the polymer-induced liquid-phase precursor route in the presence of magnesium. Only low magnesium-bearing calcite was formed in the absence of the polymer. A similar approach of using a polymeric additive was implemented in calcium phosphate. Spherulitic crystals and films, seemingly formed from a molten state, were produced. These structures served as nucleating surfaces for the radial formation of calcium oxalate minerals. The composite calcium phosphate-calcium oxalate assemblies are similar to the core-shell structures found in certain kidney stones.

Amos, Fairland F.

368

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

369

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

370

Effective spin model for the spin-liquid phase of the Hubbard model on the triangular lattice.  

PubMed

We show that the spin-liquid phase of the half-filled Hubbard model on the triangular lattice can be described by a pure spin model. This is based on a high-order strong coupling expansion (up to order 12) using perturbative continuous unitary transformations. The resulting spin model is consistent with a transition from three-sublattice long-range magnetic order to an insulating spin-liquid phase, and with a jump of the double occupancy at the transition. Exact diagonalizations of both models show that the effective spin model is quantitatively accurate well into the spin-liquid phase, and a comparison with the Gutzwiller projected Fermi sea suggests a gapless spectrum and a spinon Fermi surface. PMID:21231711

Yang, Hong-Yu; Läuchli, Andreas M; Mila, Frédéric; Schmidt, Kai Phillip

2010-12-29

371

The role of chelate-forming ligands in the generation of the catalytic function of Cu{sup 2+} complexes based on hydrozone imines in liquid-phase oxidation of cyclohexene by molecular oxygen  

Microsoft Academic Search

The dependence of the catalytic activity of bicyclic and tricyclic Cu{sup 2+} chelates based on hydrazone imines in a model reaction of liquid-phase oxidation of cyclohexene by molecular oxygen on the donor-acceptor properties of ligands and the number of coordinating atoms of the ligands is studied. Decreasing this number with the retention of the coordination geometry of the chelate center

A. N. Zakharov; G. V. Panova; N. S. Zefirov

1994-01-01

372

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

373

Liquid-Phase Sensor Using Shear Horizontal Surface Acoustic Wave Devices  

NASA Astrophysics Data System (ADS)

A surface acoustic wave (SAW) is perturbed from physical and/or chemical changes of an adjacent medium. If a liquid-phase sensor is realized, a shear horizontal SAW (SH-SAW) must be used. The SH-SAW sensors been investigated since 1987. Measuring objects of the SH-SAW sensor are not only immunoreactions but also liquid properties. Feature of the SH-SAW sensor is simultaneous detection of mechanical and electrical properties of liquid. In this paper, first, theory of the SH-SAW sensor is described. Then experimental results using the SH-SAW sensor on 36YX-LiTaO3 are introduced. Also, the sensor sensitivities of the SH-SAW sensors which are fabricated on piezoelectric substrates are theoretically compared.

Kondoh, Jun

374

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

2013-08-08

375

Simulating liquid-liquid phase separation and lipid transport on the Anton special purpose machine  

NASA Astrophysics Data System (ADS)

We present simulation data for a bilayer composed of a ternary mixture of cholesterol, dioloeoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine. The composition is chosen to be in the two-phase region and the temperature in the vicinity of the miscibility transition. Using the Anton special purpose computer to generate continuous trajectories longer the ten microseconds---which admits complete mixing of the lipids---we observe robust liquid-liquid phase coexistence. The time-and ensemble-averaged mean squared displacement (MSD) displays anomalous scaling on timescales less than 50 nsec and normal diffusion on longer timescales. The short-time anomalous scaling is explained by a mode-coupling argument[Flenner et al Phys Rev E 79:011907(2009)]. The per-lipid MSD's suggest that a few lipids remain associated with the liquid ordered domain for the duration of the simulation, suggesting a possible mechanism for anomalous transport on experimentally accessible timescales.

Lyman, Edward; Sandar, Logan; Sodt, Alexader; Pastor, Richard W.

2013-03-01

376

Control of protein crystal nucleation around the metastable liquid-liquid phase boundary  

PubMed Central

The capability to enhance or suppress the nucleation of protein crystals opens opportunities in various fundamental and applied areas, including protein crystallography, production of protein crystalline pharmaceuticals, protein separation, and treatment of protein condensation diseases. Herein, we show that the rate of homogeneous nucleation of lysozyme crystals passes through a maximum in the vicinity of the liquid–liquid phase boundary hidden below the liquidus (solubility) line in the phase diagram of the protein solution. We found that glycerol and polyethylene glycol (which do not specifically bind to proteins) shift this phase boundary and significantly suppress or enhance the crystal nucleation rates, although no simple correlation exists between the action of polyethylene glycol on the phase diagram and the nucleation kinetics. The control mechanism does not require changes in the protein concentration, acidity, and ionicity of the solution. The effects of the two additives on the phase diagram strongly depend on their concentration, which provides opportunities for further tuning of nucleation rates.

Galkin, Oleg; Vekilov, Peter G.

2000-01-01

377

Construction materials for reaction unit in the liquid-phase synthesis of propylene oxide  

SciTech Connect

The main components of the reaction medium in equipment for the synthesis of propylene oxide by liquid-phase oxidation of gaseous propylene with peracetic acid are propylene, peracetic acid, ethyl acetate, acetic acid, propylene oxide, carbon dioxide, oxygen, methane, and propylene glycol acetates. The operating conditions of the equipment and content of the main components of the medium are shown. Results are given for the investigation of the corrosion behavior of 12Kh18N10T, 10Kh17N13M2T, 08Kh22N6T, and 08Kh21N6M2T steels, AD0 and AD1 aluminum, and VT1-0 titanium. VSt3 carbon steel was tested for comparison.

Zaritskii, V.I.D.

1987-09-01

378

Vector chiral spin liquid phase in quasi-one-dimensional incommensurate helimagnets  

NASA Astrophysics Data System (ADS)

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, = , 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 (?7%, to be compared with ?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; Cuccoli, Alessandro; Rettori, Angelo

2011-05-01

379

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

380

Mixturelike behavior near a liquid-liquid phase transition in simulations of supercooled water.  

PubMed

In simulations of a waterlike model (ST2) that exhibits a liquid-liquid phase transition, we test for the occurrence of a thermodynamic region in which the liquid can be modeled as a two-component mixture. We assign each molecule to one of two species based on the distance to its fifth-nearest neighbor, and evaluate the concentration of each species over a wide range of temperature and density. Our concentration data compare well with mixture-model predictions in a region between the liquid-liquid critical temperature and the temperature of maximum density. Fits of the model to the data in this region yield accurate estimates for the location of the critical point. We also show that the liquid outside the region of density anomalies is poorly modeled as a simple mixture. PMID:21469883

Cuthbertson, Megan J; Poole, Peter H

2011-03-17

381

Free energy surface of ST2 water near the liquid-liquid phase transition.  

PubMed

We carry out umbrella sampling Monte Carlo simulations to evaluate the free energy surface of the ST2 model of water as a function of two order parameters, the density and a bond-orientational order parameter. We approximate the long-range electrostatic interactions of the ST2 model using the reaction-field method. We focus on state points in the vicinity of the liquid-liquid critical point proposed for this model in earlier work. At temperatures below the predicted critical temperature we find two basins in the free energy surface, both of which have liquid-like bond orientational order, but differing in density. The pressure and temperature dependence of the shape of the free energy surface is consistent with the assignment of these two basins to the distinct low density and high density liquid phases previously predicted to occur in ST2 water. PMID:23343283

Poole, Peter H; Bowles, Richard K; Saika-Voivod, Ivan; Sciortino, Francesco

2013-01-21

382

Liquid-phase synthesis of polyhydroquinoline using task-specific ionic liquid technology.  

PubMed

A new strategy for the synthesis of polyhydroquinolines from task-specific ionic liquids (TSIL) as a soluble support was developed. The preparation of the polyhydroquinolines by a three-component reaction was achieved by using ionic liquid-phase bound beta-oxo esters. These starting functionalized esters were synthesized by a solventless transesterification without catalyst under microwave irradiation. The structure of the intermediates in each step was verified routinely by spectroscopic analysis, and after oxidation of the polyhydroquinolines grafted on the TSIL with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone or after cleavage (transesterification, saponification-acidification), the target compounds were obtained in good yields and high purities. PMID:17096571

Legeay, Jean Christophe; Goujon, Jean Yves; Vanden Eynde, Jean Jacques; Toupet, Loic; Bazureau, Jean Pierre

383

Liquid Phase Oxidation Grown Mism and Misim Switches by GaAs Native Oxides  

NASA Astrophysics Data System (ADS)

Experimental predictions have been made for two-state bistable switching in both metal-GaAs native oxide-semiconductor-metal (MISM) and metal-GaAs native oxide-semiconductor-GaAs native oxide-metal (MISIM) structures for the first time, where the GaAs native oxides are formed by the liquid phase oxidation method. Bidirectional two-state switching (DIAC-like) and three-terminal operation are also shown in the photo-sensitive MISIM structure. Typical switching voltages for GaAs MISM and MISIM switches under 4 nm-thick native oxides are 7 V and 15 V, respectively. The corresponding voltage control efficiencies for MISM and MISIM switches are also as high as 3.944 and 7.04. The corresponding variation in voltage control efficiency, ??=?VS/VH, is also as high as 2.5 at 150 nW incident light power.

Yarn, Kao-Feng

384

Liquid phase immunoassay utilizing magnetic marker and high Tc superconducting quantum interference device  

NASA Astrophysics Data System (ADS)

We have developed a liquid phase immunoassay system utilizing a magnetic marker and a superconducting quantum interference device (SQUID). In this system, the magnetic marker was used to detect the biological material called antigen. The magnetic marker was designed so as to generate a remanence, and the remanence field of the markers that bound to the antigens was measured with the SQUID. The measurement was performed in a solution that contained both the bound and free (or unbound) markers, i.e., without using the so-called bound/free (BF) separation process. The Brownian rotation of the free markers in the solution was used to distinguish the bound markers from the free ones. Using the system, we conducted the detection of biological material called IgE without BF separation. At present, we could detect the IgE down to 7 pg (or 39 amol).

Enpuku, K.; Soejima, K.; Nishimoto, T.; Tokumitsu, H.; Kuma, H.; Hamasaki, N.; Yoshinaga, K.

2006-09-01

385

Surface Specularity as AN Indicator of Shock-Induced Solid-Liquid Phase Transitions in Tin  

NASA Astrophysics Data System (ADS)

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. A familiar manifestation of this phenomenon is the loss of signal light in VISAR measurements, which usually occurs at pressures high enough to melt the free surface. Unlike many other potential material phase-sensitive diagnostics (e.g., reflectometery, 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.

Stevens, G. D.; Lutz, S. S.; Marshall, B. R.; Turley, W. D.; Veeser, L. R.; Hixson, R. S.; Jensen, B. J.; Rigg, P. A.; Wilke, M. D.

2007-12-01

386

Surface Specularity as an Indicator of Shock-Induced Solid-Liquid Phase Transitions  

NASA Astrophysics Data System (ADS)

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.

Stevens, G. D.; Lutz, S. S.; Turley, W. D.; Veeser, L. R.; Rigg, P. A.; Jensen, B. J.; Hixson, R. S.

2007-06-01

387

Spectroscopic-ellipsometric study of native oxide removal by liquid phase HF process  

NASA Astrophysics Data System (ADS)

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.

2013-02-01

388

Microstructural effects on distortion and solid-liquid segregation during liquid phase sintering under microgravity conditions  

NASA Astrophysics Data System (ADS)

Tungsten heavy alloys with compositions ranging from 78 to 98 wt pct tungsten were liquid phase sintered at 1507 °C under microgravity conditions for 120 minutes. The sintered microstructures were quantitatively measured for solid volume fraction, grain size, connectivity, and contiguity. Links between these microstructural parameters were analyzed and compared to previously derived empirical equations. The macrostructures of the samples were also quantified and correlated to the underlying microstructures. Critical values of solid volume fraction, contiguity, and connectivity required for free-standing structural rigidity were defined for various degrees of bond rigidity as represented by the dihedral angle. The results are used to predict the degree of solid-liquid segregation due to density differences between the solid and the liquid.

Johnson, John L.; Upadhyaya, A.; German, Randall M.

1998-08-01

389

Epitaxial growth of graphene on transition metal surfaces: chemical vapor deposition versus liquid phase deposition  

NASA Astrophysics Data System (ADS)

The epitaxial growth of graphene on transition metal surfaces by ex situ deposition of liquid precursors (LPD, liquid phase deposition) is compared to the standard method of chemical vapor deposition (CVD). The performance of LPD strongly depends on the particular transition metal surface. For Pt(111), Ir(111) and Rh(111), the formation of a graphene monolayer is hardly affected by the way the precursor is provided. In the case of Ni(111), the growth of graphene strongly depends on the applied synthesis method. For CVD of propene on Ni(111), a 1 × 1 structure as expected from the vanishing lattice mismatch is observed. However, in spite of the nearly perfect lattice match, a multi-domain structure with 1 × 1 and two additional rotated domains is obtained when an oxygen-containing precursor (acetone) is provided ex situ.

Grandthyll, Samuel; Gsell, Stefan; Weinl, Michael; Schreck, Matthias; Hüfner, Stefan; Müller, Frank

2012-08-01

390

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

391

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

392

Liquid-phase chemical hydrogen storage: catalytic hydrogen generation under ambient conditions.  

PubMed

There is a demand for a sufficient and sustainable energy supply. Hence, the search for applicable hydrogen storage materials is extremely important owing to the diversified merits of hydrogen energy. Lithium and sodium borohydride, ammonia borane, hydrazine, and formic acid have been extensively investigated as promising hydrogen storage materials based on their relatively high hydrogen content. Significant advances, such as hydrogen generation temperatures and reaction kinetics, have been made in the catalytic hydrolysis of aqueous lithium and sodium borohydride and ammonia borane as well as in the catalytic decomposition of hydrous hydrazine and formic acid. In this Minireview we briefly survey the research progresses in catalytic hydrogen generation from these liquid-phase chemical hydrogen storage materials. PMID:20379965

Jiang, Hai-Long; Singh, Sanjay Kumar; Yan, Jun-Min; Zhang, Xin-Bo; Xu, Qiang

2010-05-25

393

Solid-liquid phase coexistence of alkali nitrates from molecular dynamics simulations.  

SciTech Connect

Alkali nitrate eutectic mixtures are finding application as industrial heat transfer fluids in concentrated solar power generation systems. An important property for such applications is the melting point, or phase coexistence temperature. We have computed melting points for lithium, sodium and potassium nitrate from molecular dynamics simulations using a recently developed method, which uses thermodynamic integration to compute the free energy difference between the solid and liquid phases. The computed melting point for NaNO3 was within 15K of its experimental value, while for LiNO3 and KNO3, the computed melting points were within 100K of the experimental values [4]. We are currently extending the approach to calculate melting temperatures for binary mixtures of lithium and sodium nitrate.

Jayaraman, Saivenkataraman

2010-03-01

394

Control of Plasma and Cavitation Bubble in Liquid-Phase Laser Ablation Using Supersonic Waves  

NASA Astrophysics Data System (ADS)

We examined the effects of a supersonic wave on laser-induced plasma and ablation-induced cavitation bubbles in liquid-phase laser ablation. The effect of the supersonic wave on laser-induced plasma was the change in the optical emission intensity. We observed an intense optical emission when the ablation target was irradiated with a laser pulse at a negative phase of the sound pressure of the supersonic wave. The effect of the supersonic wave on ablation-induced cavitation bubbles was the repetitive formation and collapse of the bubbles at the same frequency as the supersonic wave. The ablation-induced cavitation bubbles served as a ``seed'', and the repetitive formation and collapse of the cavitation bubbles were driven by the sound pressure of the supersonic wave.

Takada, Noriharu; Fujikawa, Akinori; Sasaki, Koichi

2011-12-01

395

Micromechanics of deformation in porous liquid phase sintered alumina under hertzian contact  

SciTech Connect

A series of fine-grained porous alumina samples, with and without a liquid phase, were fabricated in compositions matched closely to commercially available alumina used as a microelectronic substrates. Hertzian indentation on monolithic specimens of the glass-containing samples produced a greater quasi-ductile stress-strain response compared to that observed in the pure alumina. Maximum residual indentation depths, determined from surface profilometry, correlated with the stress-strain results. Moreover, microstructural observations from bonded interface specimens revealed significantly more damage in the form of microcracking and under extreme loading, pore collapse, in the glass-containing specimens. The absence of the typical twin faulting mechanism observed for larger-grained alumina suggests that the damage mechanism for quasi-ductility in these fine-grained porous alumina derived from the pores acting as a stress concentrator and the grain boundary glass phase providing a weak path for short crack propagation.

DIGIOVANNI,ANTHONY A.; CHAN,HELEN M.; HARMER,MARTIN P.; NIED,HERMAN F.

2000-05-15

396

Density and surface tension of calcium, strontium, and barium in the liquid phase  

SciTech Connect

The method of maximum pressure in a gas bubble, with the aid of two capillary tubes of different diameter, was used to study the density and surface tension of alkaline-earth metals (Ca, Sr, Ba) in the liquid phase up to 1840/sup 0/K (Ca), 1683/sup 0/K (Sr), and 1852/sup 0/K (Ba). Experimental values of the investigated properties are presented along with parameters of approximating equations describing the change in the properties with temperature. An analysis is made of the literature data on the density and surface tension of liquid alkaline-earth metals. Recommended values of the properties of calcium, strontium, and barium up to 2000/sup 0/K are obtained from joint analysis of the data.

Shpil'rain, E.E.; Fomin, V.A.; Kachalov, V.V.

1986-09-01

397

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

SciTech Connect

The Liquid Phase Methanol (LPMEOH) Demonstration Project at Kingsport, Tennessee, is a $213.7 million effort being conducted under a cooperative agreement between the U.S. Department of Energy (DOE) and Air Products Liquid Phase Conversion Company, L.P. (the Partnership). Air Products and Chemicals, Inc. (Air Products) and Eastman Chemical Company (Eastman) formed the Partnership to execute the Demonstration Project. A demonstration unit producing 80,000 gallons per day (260 tons-per-day (TPD)) of methanol from coal-derived synthesis gas (syngas) was designed, constructed, and began a four-year operational period in April of 1997 at a site located at the Eastman complex in Kingsport. The Partnership will own and operate the facility for the four-year demonstration period. This project is sponsored under the DOE's Clean Coal Technology Program, and its primary objective is to "demonstrate the production of methanol using the LPMEOH?M Process in conjunction with an integrated coal gasification facility." The project will also demonstrate the suitability of the methanol produced for use as a chemical feedstock or as a low-sulfur dioxide, low-nitrogen oxides alternative fiel in stationary and transportation applications. The project may also demonstrate the production of dimethyl ether (DME) as a mixed coproduct with methanol, if laboratory- and pilot-scale research and market verification studies show promising results. If implemented, the DME would be produced during the last six months of the four-year demonstration period. The LPMEOJYM process is the product of a cooperative development effort by Air Products and the DOE in a program that started in 1981. It was successfidly piloted at a 10-TPD rate in the DOE-owned experimental unit at Air Products' LaPorte, Texas, site. This Demonstration Project is the culmination of that extensive cooperative development effort.

None

1997-12-31

398

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

SciTech Connect

The Liquid Phase Methanol (LPMEOHT") 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). Air Products and Chemicals, Inc. (Air Products) and Eastman Chemical Company (Eastman) formed the Partnership to execute the Demonstration Project. A demonstration unit producing 80,000 gallons per day (260 tons-per-day) of methanol from coal-derived synthesis gas (syngas) was designed, constructed, and is operating at a site located at the Eastman complex in Kingsport. The Partnership will own and operate the facility for the four-year demonstration period. This project is sponsored under the DOE's Clean Coal Technology Program, and its primary objective is to "demonstrate the production of methanol using the LPMEOWM Process in conjunction with an integrated coal gasification facility." The project will also demonstrate the suitability of the methanol produced for use as a chemical feedstock or as a low-sulfur dioxide, low-nitrogen oxides alternative fiel in stationary and transportation applications. The project may also demonstrate the production of dimethyl ether (DME) as a mixed coproduct with methanol, if laboratory- and pilot-scale research and market verification studies show promising results. If implemented, the DME would be produced during the last six months of the four-year demonstration period. The LPMEOITM process is the product of a cooperative development effort by Air Products and the DOE in a program that started in 1981. It was successfdly piloted at a 10 tons-per- day (TPD) rate in the DOE-owned experimental unit at Air Products' LaPorte, Texas, site. This demonstration project is the culmination of that extensive cooperative development effort.

None

1997-09-30

399

Assembly and patterning of ferromagnetic nanoparticles from solution: A novel low-temperature liquid-phase annealing approach  

Microsoft Academic Search

Ferromagnetic L10-phase FePtAu nanoparticles (5–6nm) were prepared using a low-temperature, liquid phase annealing approach. The chemically ordered, ferromagnetic L10-phase onset occurs for annealing temperatures as low as 150°C. Large uniaxial magnetic anisotropy (Ku?107erg\\/cm3) and a large long-range ordering parameter have been obtained. Significantly, the low-temperature liquid-phase annealing preserves the organic functionalization groups of the nanoparticles. Hence, these nanoparticles are flexible

T. Gang; M. Groen; S. Kinge; W. J. M. Naber; H. Boschker; G. Rijnders; D. N. Reinhoudt; W. G. van der Wiel

2011-01-01

400

Production of few-layer graphene through liquid-phase pulsed laser exfoliation of highly ordered pyrolytic graphite  

NASA Astrophysics Data System (ADS)

Graphene suspension was obtained through liquid-phase pulsed laser exfoliation of highly ordered pyrolytic graphite (HOPG). The liquid-phase pulsed laser process leaded to the compression and expansion of HOPG surface, resulting in the exfoliation of graphene sheets. Graphene sheets of ˜1 nm in thickness and micrometers in size were obtained. Transparent conductive graphene films were fabricated by vacuum filtration, showing an electrical conductivity of ˜1000 S/m and an optical transparency of ˜75% at 550 nm. This study demonstrated the growth of few-layer graphene by pulsed laser exfoliation of HOPG in liquid and explored its applications in transparent conductive films.

Qian, Min; Zhou, Yun Shen; Gao, Yang; Feng, Tao; Sun, Zhuo; Jiang, Lan; Lu, Yong Feng

2012-09-01

401

Fabrication and characteristics of thin-film optical switches using fluorinated silicon oxide deposited by a liquid-phase technique  

Microsoft Academic Search

Optical switching devices have been studied using thin-film optical waveguides with fluorinated silicon oxide (SiOF) films\\u000a deposited by a liquid-phase deposition (LPD) technique. This report focuses on the structure of the thermo-optical (TO) switch\\u000a and its optimization. TO devices with double-and triple-layer structures were fabricated using a material with an organic\\u000a spin-on-glass (SOG) cladding layer and a liquid-phase deposited (LPD)

Isamu Takishita; Kenji Kurosu; Tetsuya Homma

2008-01-01

402

AlGaN/GaN MOSHFET with a SiO2 Gate by Liquid Phase Deposition  

NASA Astrophysics Data System (ADS)

An efficient and low cost approach for depositing uniform silicon dioxide layers on GaN by liquid phase deposition (LPD) that is near room temperature will be described. The self-align and self-passivation process of LPD can ease the device fabrication. AlGaN/GaN metal oxide semiconductor heterostructure field effect transistors (MOSHFETs) with liquid phase deposited SiO2 as the insulating gate are demonstrated. Comparison between the AlGaN/GaN MOSHFETs and heterostructure field effect transistors (HFETs) will be made. Lower leakage currents, larger gate swing voltages and flatter transconductance ranges can be seen in MOSHFETs.

Huang, J. J.; Sze, P. W.; Lin, S. K.; Lai, W. C.; Wang, Y. H.; Houng, M. P.

2004-01-01

403

Diffusion Coefficients and Viscosities of CO2 + H2O, CO2 + CH3OH, NH3 + H2O, and NH3 + CH3OH Liquid Mixtures  

Microsoft Academic Search

To evaluate quantitatively the results of gas-liquid absorption experiments, accurate liquid-phase diffusion coefficients and viscosities are needed. In this paper experimental values of these quantities will be reported for the binary systems carbon dioxide + water, carbon dioxide + methanol, ammonia + water, and ammonia + methanol. The diffusion coefficients have been measured using the Taylor-Aris dispersion method, and the

Marco J. W. Frank; Johannes A. M. Kuipers; Swaaij van W. P. M

1996-01-01

404

Diffusion coefficients and viscosities of COâ + HâO, COâ + CHâOH, NHâ + HâO, and NHâ + CHâOH liquid mixtures  

Microsoft Academic Search

To evaluate quantitatively the results of gas-liquid absorption experiments, accurate liquid-phase diffusion coefficients and viscosities are needed. In this paper experimental values of these quantities will be reported for the binary systems carbon dioxide + water, carbon dioxide + methanol, ammonia + water, and ammonia + methanol. The diffusion coefficients have been measured using the Taylor-Aris dispersion method, and the

M. J. W. Frank; J. A. M. Kuipers; W. P. M. van Swaaij

1996-01-01

405

Calculation of the barometric coefficients for the particle d etectors belonging to the world-wide networks at the start of the 24th solar activity cycle  

Microsoft Academic Search

After major modernization of the data acquisition electronics of the Aragats Space Envi- ronmental Center (ASEC) particle detectors the cal- culations of the barometric coefficients of all ASEC particle monitors were performed in the beginning of 24th solar activity cycle. The time periods of minimal disturbances of the interplanetary magnetic field (IMF) were selected to avoid biases due to transient

Ashot Chilingarian; Tigran Karapetyan; Bagrat Mailyan

406

Correlation and comparison of the infinite dilution activity coefficients in aqueous and organic mixtures from a modified excess Gibbs energy model  

Microsoft Academic Search

Activity coefficients at infinite dilution (ln??) of aqueous systems were calculated using a modified excess Gibbs energy model. More than 95 binary systems with 15 solute families from nonpolar alkanes to polar alcohols and acids were employed in this study. Based on the local composition lattice model developed by Aranovich and Donohue, a modified excess Gibbs energy equation (m-AD model)

Jaw-Shin Cheng; Muoi Tang; Yan-Ping Chen

2004-01-01

407

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

408

A unified view of energetic efficiency in active drag reduction, thrust generation and self-propulsion through a loss coefficient with some applications  

NASA Astrophysics Data System (ADS)

An analysis of the energy budget for the general case of a body translating in a stationary fluid under the action of an external force is used to define a power loss coefficient. This universal definition of power loss coefficient gives a measure of the energy lost in the wake of the translating body and, in general, is applicable to a variety of flow configurations including active drag reduction, self-propulsion and thrust generation. The utility of the power loss coefficient is demonstrated on a model bluff body flow problem concerning a two-dimensional elliptical cylinder in a uniform cross-flow. The upper and lower boundaries of the elliptic cylinder undergo continuous motion due to a prescribed reflectionally symmetric constant tangential surface velocity. It is shown that a decrease in drag resulting from an increase in the strength of tangential surface velocity leads to an initial reduction and eventual rise in the power loss coefficient. A maximum in energetic efficiency is attained for a drag reducing tangential surface velocity which minimizes the power loss coefficient. The effect of the tangential surface velocity on drag reduction and self-propulsion of both bluff and streamlined bodies is explored through a variation in the thickness ratio (ratio of the minor and major axes) of the elliptical cylinders.

Arakeri, Jaywant H.; Shukla, Ratnesh K.

2013-08-01

409

Development of negligible depletion hollow fiber-protected liquid-phase microextraction for sensing freely dissolved triazines.  

PubMed

A new sampling method, termed negligible depletion hollow fiber-protected liquid-phase microextraction, was developed for sensing the freely dissolved concentration (C(free)) and evaluating the availability of atrazine (ATR), desethyl atrazine (DEA), and simazine (SIM) in water. The sampling device was prepared by impregnating 1-octanol to both the pores and the lumen of a piece of polypropylene microporous hollow fiber membrane. After equilibrium and negligible depletion extraction, the 1-octanol in the lumen of the hollow fiber (10 microl) was collected for determination of triazines. Determination of C(free) and the distribution coefficient to 1-octanol (D(ow)) can be performed with this technique. A wide linear working range (1-200 microg/L) and low detection limits (0.1-1 microg/L) were obtained for triazines. Measured log D(ow) values of DEA (1.44 +/- 0.04), SIM (2.06 +/- 0.06), and ATR (2.33 +/- 0.05) agreed well with those reported in the literature. The measured D(ow) values were independent of the chemical concentration and sample pH (pH 3-10) and negligibly affected by the sample salinity (0-500 mM), suggesting that environmentally relevant pH and salinity have no significant effects on the availability of triazines. Although a slight (< or = 31%) increase of C(free) was observed, one-way analysis of variance indicated the C(free) of triazines were not significantly affected by the presence of Aldrich humic acid, Acros humic acid, and bovine albumin V (dissolved organic carbon [DOC], 0-100 mg/L). From 3 to 36% of the spiked triazines, however, were found to associate with the dissolved organic matter (DOM) in surface-water samples (DOC, 32.0-61.9 mg/L), suggesting the origin of the DOM is a key parameter in determining its association with and, thus, the availability of triazines. PMID:18937535

Hu, Xialin; Liu, Jingfu; Jönsson, Jan A; Jiang, Guibin

2009-02-01

410

Causes of liquid phase migration in powdered metal materials during consolidation by self-propagating high-temperature synthesis  

Microsoft Academic Search

The phenomena of liquid phase migration in the combustion of powdered metal pressings are investigated. The onset of a temperature gradient induced by a combustion wave is established as one of the causes of migration. The resulting capillary potential difference in the pores is directed toward the cooler side of the pressing. It is hypothesized that part of the melt

V. D. Zazulya; V. V. Tsvetkov

1995-01-01

411

New fabrication technique of fluorocarbon polymer-coated hollow waveguides by liquid-phase coating for medical applications  

Microsoft Academic Search

A new method to fabricate dielectric-coated hollow waveguides has been proposed based on all liquid-phase techniques. Long silver tubes with an extremely smooth inner surface have been fabricated by using a new process of silver mirror reaction and loss reduction of short silver waveguides has been made by liquid flow-coating of a fluorocarbon polymer.

Yuji Kato; Mitsuo Osawa; Mitsunobu Miyagi; Masaru Aizawa; Shin-ichi Abe; Shinji Onodera

1994-01-01

412

Fermi-liquid and non-Fermi-liquid phases of an extended Hubbard model in infinite dimensions  

Microsoft Academic Search

We study an extended Hubbard model in the limit of infinite dimensions. The local correlation functions of this model are those of a generalized asymmetric Anderson model. The impurity model displays a Fermi liquid phase, a phase with neither the spin nor the charge of the impurity quenched, and an intermediate phase with the spin but not the charge of

Qimiao Si; G. Kotliar

1993-01-01

413

LETTER TO THE EDITOR: Selective and blanket liquid phase deposition of silicon dioxide on silicon nitride and tungsten silicide  

NASA Astrophysics Data System (ADS)

In the conventional process of liquid phase deposition, silicon dioxide cannot be deposited on silicon nitride and tungsten silicide substrates. In the present study, this limitation is removed by adding aqueous ammonia to the hydrofluorosilicic acid source. A selective or blanket deposition can be controlled. The deposition rate is also enhanced.

Lee, Ming-Kwei; Shih, Chung-Min; Yang, Chi-Da

2003-07-01

414

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

415

Liquid phase residence time distribution for a two-phase countercurrent flow in a packed column with a novel internal  

Microsoft Academic Search

The liquid phase residence time distribution (RTD) for gas–liquid countercurrent flow in a packed column with a novel internal was measured by conductivity measurements and an air–water system. The RTD of a liquid tracer is well represented by the ADM and PDE models. At lower gas flow rates, the Peclet number of the liquid in the packed column with the

Yanhui Yuan; Minghan Han; Dezheng Wang; Yong Jin

2004-01-01

416

InSb grown on Cd0.955Zn0.045Te by liquid phase epitaxy  

NASA Astrophysics Data System (ADS)

InSb has been grown by liquid phase epitaxy using indium rich solutions with a supercooling of 2-5 °C onto (1 1 1) oriented Cd0.955Zn0.045Te substrates at 400-405 °C. The resulting epitaxial layers were extensively characterized using X-ray diffraction, optical microscopy, Raman spectroscopy and photoluminescence.

Yin, M.; Krier, A.

2013-05-01

417

Role of Hydroperoxide and Peroxy Radicals in the Mechanism of the Liquid-Phase Oxidation of 1-Butene.  

National Technical Information Service (NTIS)

The example of the liquid-phase oxidation of 1-butene the problem of clarifying the kinetic role of hydroperoxide and peroxy radicals in the mechanism of the formation of olefins oxides and other products of the reaction has been established. (Author)

B. I. Chernyak B. I. Koshovskii R. V. Kucher

1970-01-01

418

Effects of Lead Incorporation on the Ferromagnetic Resonance Linewidths of Liquid Phase Epitaxial Grown Yttrium Iron Garnet.  

National Technical Information Service (NTIS)

Single crystal thin films of yttrium iron garnet (YIG) were grown on gadolinium gallium garnet (GGG) substrates by the isothermal dipping method of liquid phase epitaxy. The concentration of Pb in the films was adjustable through selection of the growth t...

M. T. Elliott

1975-01-01

419

The liquid phase epitaxy method for the construction of oriented ZIF-8 thin films with controlled growth on functionalized surfaces.  

PubMed

Highly-oriented ZIF-8 thin films with controllable thickness were grown on an -OH-functionalized Au substrate using the liquid phase epitaxy method at room temperature, as evidenced by SEM and PXRD. The adsorption-desorption properties of the resulting ZIF-8 thin film were investigated for various VOCs using the QCM technique. PMID:24056617

Shekhah, Osama; Eddaoudi, Mohamed

2013-10-01

420

Modulation of amyloid precursor protein processing by compounds with various mechanisms of action: detection by liquid phase electrochemiluminescent system  

Microsoft Academic Search

?-Amyloid peptide (A?) is a major component of senile plaques formed in the brain of Alzheimer disease patients. We describe here a new method of quantitating A? in biological material using liquid phase electrochemiluminescent system (LPECL). We used both enzyme-linked immunosorbent assay (ELISA) and LPECL methods to measure A? and APPs? levels in conditioned medium of ?-amyloid precursor protein (APP)-transfected

Olga E Khorkova; Kirti Patel; Jeffrey Heroux; Sudhir Sahasrabudhe

1998-01-01

421

Thermal conductivity of R32 and R125 in the liquid phase at the saturation vapor pressure  

Microsoft Academic Search

The first measurements of the thermal conductivity of two refrigerants which are candidates for the replacement of those fluids currently in use are reported. Specifically, results are given for the thermal conductivity of R32 and R125 in the liquid phase along the saturation line. The measurements, which have been made by the transient hot-wire technique, extend over the temperature range

M. Papadaki; W. A. Wakeham

1993-01-01

422

Reports of investigations on: Derivation of an infinite-dilution activity coefficient model and application to two-component vapor/liquid equilibria data: Final report  

SciTech Connect

Infinite-dilution fugacity coefficients were obtained for the system fluorene/phenanthrene at thirteen temperatures by fitting total pressure across the entire mole fraction range by a computer routine. A thermodynamically consistent routine, that allowed for both positive and negative pressure deviations from the ideal values, was used to correlate data over the full mole fraction range from 0 to 1. The four-suffix Margules activity coefficient model without modification essentially served this purpose since total pressures and total pressure derivatives with respect to mole fraction were negligible compared to pressure measurement precision. The water/ethanol system and binary systems comprised of aniline, chlorobenzene, acetonitrile and other polar compounds were fit for total pressure across the entire mole fraction range for binary Vapor-Liquid-Equilbria (VLE) using the rigorous, thermodynamically consistent Gibbs-Duhem Relation derived by Ibl and Dodge. Data correlation was performed using a computer least squares procedure. Infinite-dilution fugacity coefficients were obtained using a modified Margules activity coefficient model.

Roper, V.P.; Kobayashi, R.

1988-02-01

423

Gas-particle partitioning of semi-volatile organics on organic aerosols using a predictive activity coefficient model: analysis of the effects of parameter choices on model performance  

NASA Astrophysics Data System (ADS)

The partitioning of a diverse set of semivolatile organic compounds (SOCs) on a variety of organic aerosols was studied using smog chamber experimental data. Existing data on the partitioning of SOCs on aerosols from wood combustion, diesel combustion, and the ?-pinene-O 3 reaction was augmented by carrying out smog chamber partitioning experiments on aerosols from meat cooking, and catalyzed and uncatalyzed gasoline engine exhaust. Model compositions for aerosols from meat cooking and gasoline combustion emissions were used to calculate activity coefficients for the SOCs in the organic aerosols and the Pankow absorptive gas/particle partitioning model was used to calculate the partitioning coefficient Kp and quantitate the predictive improvements of using the activity coefficient. The slope of the log K p vs. log p L0 correlation for partitioning on aerosols from meat cooking improved from -0.81 to -0.94 after incorporation of activity coefficients i? om. A stepwise regression analysis of the partitioning model revealed that for the data set used in this study, partitioning predictions on ?-pinene-O 3 secondary aerosol and wood combustion aerosol showed statistically significant improvement after incorporation of i? om, which can be attributed to their overall polarity. The partitioning model was sensitive to changes in aerosol composition when updated compositions for ?-pinene-O 3 aerosol and wood combustion aerosol were used. The octanol-air partitioning coefficient's ( KOA) effectiveness as a partitioning correlator over a variety of aerosol types was evaluated. The slope of the log K p- log K OA correlation was not constant over the aerosol types and SOCs used in the study and the use of KOA for partitioning correlations can potentially lead to significant deviations, especially for polar aerosols.

Chandramouli, Bharadwaj; Jang, Myoseon; Kamens, Richard M.

424

Liquid-liquid phase separation in atmospheric aerosol particles: dependence on organic functionalities and mixture complexity  

NASA Astrophysics Data System (ADS)

In the troposphere, aerosol particles undergo phase transitions such as deliquescence and efflorescence during humidity cycles (Marcolli and Krieger, 2006). In addition, interactions between organic and inorganic compounds lead to liquid-liquid phase separation (LLPS) (Ciobanu et al., 2009). Recent studies on a limited number of model systems have shown that oxygen-to-carbon ratios (O:C) of the organic aerosol fraction might be a good predictor for LLPS in mixed organic/ammonium sulfate (AS) particles (Bertram et al., 2011; Song et al., 2011). However, in order to corroborate this hypothesis experiments with an organic fraction that consists of a higher number of components with different O:C ratios and functional groups are needed. In order to determine the influence of O:C ratio, the specific organic functionalities and the mixture complexity on LLPS, we subjected organic/AS particles deposited on a hydrophobically coated substrate to relative humidity (RH) cycles and observed phase changes using optical microscopy and micro-Raman spectroscopy. To determine the influence of mixture complexity, we mixed together up to 10 organic compounds. We also prepared mixtures that were rich in different types of functional groups like polyols, aromatics and dicarboxylic acids which were identified from field measurements. We screened for a miscibility gap by varying the organic-to-inorganic ratio from 2:1 to 1:6. AS in the investigated single particles effloresced at 27 - 50 %RH and deliquesced at 72 - 79 %RH during humidity cycles. The occurrence of LLPS is determined to a high degree by the O:C of the organics: there was no LLPS for mixtures with O:C > 0.8 and there was always LLPS for mixtures with O:C < 0.57. In the range in between, we observed a dependence on the specific functional groups: a high share of aromatic functionalities shifts the range of O:C for which LLPS occurs to lower values. A correlation was also found for the onset RH of LLPS as a function of O:C. We did not find any dependence of LLPS on the complexity of the mixture. Overall, the RH range of coexistence of two liquid phases depends in first place on the O:C ratio of the particles and in second place also on the specific organic functionalities.

Song, M.; Marcolli, C.; Krieger, U. K.; Zuend, A.; Peter, T.

2012-04-01

425

Catalyst and reactor development for a liquid-phase Fischer-Tropsch process. Quarterly technical progress report, 1 April 1981-30 June 1981  

SciTech Connect

In October 1980, Air Products and Chemicals, Inc. began a three year contract with the DOE: Catalyst and Reactor Development for a Liquid Phase Fischer-Tropsch Process. The program contains four major tasks: (1) Project Work Plan, (2) Slurry Catalyst Development, (3) Slurry Reactor Design Studies, and (4) Pilot Facility Design. This report describes work on Tasks 2 and 3 carried out in the third quarter of the contract. In Task 2, the computerized search of the Fischer-Tropsch literature was continued, and improvements were made in data processing programs. Shakedown tests were completed on the first 300 ml slurry reactor, and construction of the second and third reactors began. Five modified conventional slurry catalysts were prepared, and two batches were tested in the gas phase giving information on selectivity as a function of composition and activation. Four supported cluster catalyst were synthesized, and seven were tested in the gas phase.

Brockington, J.W.; Dyer, P.N.; Pierantozzi, R.; Brain, B.W.; Bauer, J.V.

1981-07-01

426

Preparation, characterization, and testing of a new type of porous catalytic plates usable for liquid-phase hydrogenations at enhanced mass-transfer conditions  

SciTech Connect

Thin catalytic plates were developed in order to enhance the mass transfer of gas and liquid in liquid-phase hydrogenations. The plates consist of two different layers, a supporting hydrophobic PTFE layer on the gas side and a layer of catalytic metal on a carrier on the liquid side. The plates were prepared by hydraulically pressing powders of the catalyst and PTFE. Hydrogenation of p-nitrobenzoic acid was used as a model reaction to test the plates. Very high effectiveness factor values were found in hydrogenations with the catalytic layer concentrated as a thin film close to the liquid side of the plate. The optimal thickness of the catalytic layer of the plate and optimal distribution of active material were calculated for the maximal reaction rate per unit plate area.

Hatziantonlou, V.; Andersson, B.; Larsson, T.; Schoon, N.H.; Carlsson, L.; Schwarz, S.; Wideen, K.B.

1986-01-01

427

Characterization of Liquid Phase in (Na0.5K0.5)NbO3 Ceramics with V2O5 Additions  

NASA Astrophysics Data System (ADS)

The characterizations of the microstructure and the chemical compositions on (Na0.5K0.5)(Nb0.93V0.07)O3 ceramics system sintered at 900 °C for 8 h were carried out using high resolution transmission electron microscopy (HRTEM), energy filtered (EF) TEM, and energy dispersive spectroscopy (EDS). The liquid phase was found at the triple junction of the grains and abnormal grain growth occurred in the presence of liquid phase. The liquid phase has formed by the melting of V2O5 at the sintering temperature. The presence of V element in liquid phase was confirmed by EDS analyses. The interface between the matrix phase and the liquid phase was atomically flat and consists of a stepped ledge structure of one or two atomic height. The KVO3 phase which may be formed during the cooling of the specimens was observed at these interfaces and have a good orientation relation with the matrix.

Ryu, Hyun; Kim, Young-Heon; Lee, Hwack-Joo; Cho, Yang-Koo; Nahm, Sahn

2009-09-01

428

Mechanical properties of ternary lipid membranes near a liquid-liquid phase separation boundary  

NASA Astrophysics Data System (ADS)

We study the mechanical properties of ternary lipid bilayers assembled in giant vesicles, formed from a saturated and an unsaturated phosphocholine (in equal proportions) and cholesterol. As a function of temperature, these systems can undergo in-plane phase separation. Using image analysis we identify the vesicle contour, and quantify the vesicle shape and the amplitude of membrane thermal fluctuations. The two lipid compositions chosen show different thermotropic behaviours. At 60 mol% cholesterol the membrane is in a uniform liquid state over the entire temperature range investigated (10-50 °C), but vesicles containing 30 mol% cholesterol undergo phase separation into two immiscible liquid phases at around 28 °C. Upon cooling below this transition temperature we observe a marked increase in the measured bending elastic modulus. Phase separation proceeds over a long time (tens of minutes), and we measure the properties of vesicles both during the domain coarsening phase and in the fully phase separated condition. Fluorescence microscopy allows us to identify the coexisting phases. We can therefore measure directly the bending moduli of each of the phases as a function of temperature, showing a strong variation which is attributed to the changing phospholipid and cholesterol composition.

Zoon Yoon, Young; Hale, John P.; Petrov, Peter G.; Cicuta, Pietro

2010-02-01

429

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

430

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

431

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

432

Control of protein crystal nucleation around the metastable liquid-liquid phase boundary.  

PubMed

The capability to enhance or suppress the nucleation of protein crystals opens opportunities in various fundamental and applied areas, including protein crystallography, production of protein crystalline pharmaceuticals, protein separation, and treatment of protein condensation diseases. Herein, we show that the rate of homogeneous nucleation of lysozyme crystals passes through a maximum in the vicinity of the liquid-liquid phase boundary hidden below the liquidus (solubility) line in the phase diagram of the protein solution. We found that glycerol and polyethylene glycol (which do not specifically bind to proteins) shift this phase boundary and significantly suppress or enhance the crystal nucleation rates, although no simple correlation exists between the action of polyethylene glycol on the phase diagram and the nucleation kinetics. The control mechanism does not require changes in the protein concentration, acidity, and ionicity of the solution. The effects of the two additives on the phase diagram strongly depend on their concentration, which provides opportunities for further tuning of nucleation rates. PMID:10823898

Galkin, O; Vekilov, P G

2000-06-01

433

Liquid phase epitaxial growth and electrical characterization of CuInSe2  

NASA Astrophysics Data System (ADS)

The liquid phase epitaxy (LPE) growth method of Nelson (1963) was used to grow a layer of CuInSe2 on a ZnSe substrate from a bismuth containing solution. The electrical properties of the n-CuInSe2/n-ZnSe and p-CuInSe2/n-ZnSe heterodiodes fabricated from the LPE wafer, were examined by measuring the Hall effect. The optimum conditions for LPE growth were found to be a substrate orientation of (111)Se, a Tm of 600 C, and a cooling rate of 0.5 C/min. Hall measurements indicated that the grown layer had electrical properties broadly comparable with those of the bulk material. Both the p/n and the n/n heterodiodes fabricated from an LPE wafer showed rectification properties, and the n-CuInSe2/n-ZnSe heterodiode in particular showed a high photoresponse. The effect of diffusion of Cu, In, in Bi into the substrate and the Cu InSe2 layer were investigated by means of cathodoluminescence, Hall-effect measurements, and electron-acoustic microscopy. In Bi-doped CuInSe2, Bi acts as a high mobility donor, which may prove useful for applications to photoelectric devices.

Takenoshita, H.

1986-02-01

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

Analysis of Protein Glycosylation and Phosphorylation Using Liquid Phase Separation, Protein Microarray Technology, and Mass Spectrometry  

PubMed Central

Summary Protein glycosylation and phosphorylation are very common posttranslational modifications. The alteration of these modifications in cancer cells is closely related to the onset and progression of cancer and other disease states. In this protocol, strategies for monitoring the changes in protein glycosylation and phosphorylation in serum or tissue cells on a global scale and specifically characterizing these alterations are included. The technique is based on lectin affinity enrichment for glycoproteins, all liquid-phase two-dimensional fractionation, protein microarray, and mass spectrometry technology. Proteins are separated based on pI in the first dimension using chromatofocusing (CF) or liquid isoelectric focusing (IEF) followed by the second-dimension separation using nonporous silica RP-HPLC. Five lectins with different binding specificities to glycan structures are used for screening glycosylation patterns in human serum through a biotin–streptavidin system. Fluorescent phosphodyes and phosphospecific antibodies are employed to detect specific phosphorylated proteins in cell lines or human tissues. The purified proteins of interest are identified by peptide sequencing. Their modifications including glycosylation and phosphorylation could be further characterized by mass-spectrometry-based approaches. These strategies can be used in biological samples for large-scale glycoproteome/phosphoproteome screening as well as for individual protein modification analysis.

Zhao, Jia; Patwa, Tasneem H.; Pal, Manoj; Qiu, Weilian; Lubman, David M.

2010-01-01

436

Detection of enteroviruses and rhinoviruses in clinical specimens by PCR and liquid-phase hybridization.  

PubMed Central

A sensitive method based on PCR followed by liquid-phase hybridization for detection of enterovirus and rhinovirus RNAs in clinical specimens and cell culture supernatants is described. RNA was extracted from stool samples, throat swabs, nasopharyngeal aspirates, cerebrospinal fluid, urine, and plasma with a commercial phenol-guanidinium-chloroform reagent and purified on a polysulfone membrane, on which the reverse transcriptase reaction was also done. Two sets of oligonucleotide primers from the 5' noncoding region of picornaviruses were selected for DNA amplification of 153-bp (enterovirus) and 120-bp (rhinovirus) regions. Double-stranded amplicons were digested into single strands with T7 gene 6 exonuclease and quantitated by an assay using a europium-labeled probe, streptavidin- and biotinylated probe-coated microtitration wells, and time-resolved fluorometry. The sensitivity of the assay was about one template molecule when purified coxsackievirus A9 RNA was used. All enterovirus prototype strains, except echoviruses 22 and 23, and clinical isolates grown in cell culture or suckling mice were strongly positive by the enterovirus PCR-hybridization, as were selected prototype strains and untyped isolates of rhinoviruses by the rhinovirus PCR-hybridization. In a series of 100 clinical specimens tested, the results for 92 agreed with virus culture results. The detection method described will be useful in etiopathogenic studies on enteroviruses and rhinoviruses.

Halonen, P; Rocha, E; Hierholzer, J; Holloway, B; Hyypia, T; Hurskainen, P; Pallansch, M

1995-01-01

437

Experimental investigation on liquid-phase fabrication techniques for multilayer infrared hollow fiber  

NASA Astrophysics Data System (ADS)

Infrared hollow fiber with metal and dielectric inner-coatings has found applications in medical and industrial fields. It is a commonly used method to lower the loss by inner-coating multi dielectric layers. In this paper, SiO2 and AgI were selected to fabricate the multilayer mid-infrared hollow fiber. Liquid-phase coating techniques were experimentally discussed in order to control the film thickness. It is shown that concentration and flow speed of the coating solution are key parameters to modify SiO2 film thickness. AgI film was obtained by firstly coating a silver layer and then iodinating the silver layer into AgI. SiO2 and AgI films were deposited orderly on the inner wall of a 0.7-mm bore glass capillary. Both thicknesses for SiO2 and AgI films were well controlled and optimized according to the theoretical calculation. The measured infrared loss spectrum of SiO2/AgI/SiO2/Ag multilayer hollow fiber has a good agreement with the calculated result and shows band gap effect around the wavelength of 5.3 ?m.

Sun, Bang-Shan; Zeng, Xuan; Iwai, Katsumasa; Miyagi, Mitsunobu; Chi, Nan; Shi, Yi-Wei

2011-07-01

438

A novel approach to automation of dynamic hollow fiber liquid-phase microextraction.  

PubMed

An automated dynamic two-phase hollow fiber microextraction apparatus combined with high-performance liquid chromatography was developed for extraction and determination of chlorophenoxy acid (CPA) herbicides from environmental samples. The extraction device, called TT-extractor, consists of a polypropylene hollow fiber mounted inside a stainless steel tube by means of two tee-connectors in flow system. An organic solvent, which fills the lumen and the pores of the hydrophobic fiber, is pumped through the fiber repeatedly and the sample is pumped along the outer side of the fiber. The factors affecting the dynamic hollow fiber liquid-phase microextraction (DHF-LPME) of target analytes were investigated and the optimal extraction conditions were established. To test the applicability of the designed instrument, CPAs were extracted from environmental aqueous samples. The limits of detection (LODs) as low as 0.5 ?g/L, linear dynamic range in the range of 1-100 ?g/L and the relative standard deviations of <7% were obtained. The developed method can provide perconcentration factors as large as 230. A hollow fiber membrane can be used at least 20 times with neither loss in the efficiency nor carryover of the analytes between runs. The system is cheap and convenient and requires minimal manual handling. PMID:21480523

Esrafili, Ali; Yamini, Yadollah; Ghambarian, Mahnaz; Moradi, Morteza; Seidi, Shahram

2011-04-01

439

Nitride-Based UV Metal-Insulator-Semiconductor Photodetector with Liquid-Phase-Deposition Oxide  

NASA Astrophysics Data System (ADS)

A low-temperature (30-40°C), low-cost and reliable method of liquid phase deposition (LPD) has been employed to grow SiO2 layers on GaN. The LPD process uses a supersaturated acid aqueous solution of hydrofluosilicic (H2SiF6) as a source liquid and an aqueous solution of boric acid (H3BO3) as a deposition rate controller. In this study, the LPD SiO2 was prepared at 40°C with concentrations of H2SiF6 and H3BO3 at 0.2 and 0.01 M, respectively. The minimum interface-trap density, Dit, of a metal-insulator-semiconductor (MIS) capacitor with a structure of Al/20 nm LPD-SiO2/n-GaN was estimated to be 8.4× 1011 cm-2 V-1. Furthermore, a MIS photodetector with a 10-nm-thick LPD-SiO2 layer has been fabricated successfully. The dark current density was as low as 4.41× 10-6 A/cm2 for an applied field of 4 MV/cm. A maximum responsivity of 0.112 A/W was observed for incident ultraviolet light of 366 nm with an intensity of 4.15 mW/cm2. Defect-assisted tunneling was invoked to explain these results.

Hwang, J. D.; Yang, Gwo Huei; Yang, Yuan Yi; Yao, Pin Cuan

2005-11-01

440

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

441

Comprehensive Investigations of the Supersolidus Liquid-Phase Sintering of Two Plastic Mold Steels  

NASA Astrophysics Data System (ADS)

The processing of plastics, particularly reinforced composites, necessitates the use of corrosion- and wear-resistant materials for tools that come into contact with the polymer. For such applications, plastic mold steels were developed that offer not only a good wear resistance due to the presence of carbides in a martensitic matrix, but also good corrosion resistance provided primarily by a sufficient amount of dissolved chromium. The common processing route for these high-alloyed materials is the hot isostatic pressing (HIP) of gas-atomized powders (PM-HIP). In this context, sintering plays an insignificant role, except for the processing of metal-matrix composites (MMCs). The development of novel wear- and corrosion-resistant MMCs based on plastic mold steels requires knowledge of the sintering behavior of prealloyed powders of such tool steels. It is well known that alloyed powders can be processed by supersolidus liquid-phase sintering (SLPS), a method leading to almost full densification and to microstructures without significant coarsening effects. In this work, two different gas-atomized powders of plastic mold steels were investigated by computational thermodynamics, thermal analysis, sintering experiments, and microstructural characterization. The results show that both powders can be sintered to almost full density (1 to 3 pct porosity) by SLPS in a vacuum or a nitrogen atmosphere. Experimental findings on the densification behavior, nitrogen uptake, and carbide volume fractions are in good agreement with calculations performed by computational thermodynamics.

Hill, H.; Weber, S.; Siebert, S.; Huth, S.; Theisen, W.

2010-03-01

442

MFI-type zeolite functional liquid phase sensor coated on the optical fiber end-face  

NASA Astrophysics Data System (ADS)

Optical fibers are a unique medium to coat with functional sensor materials that change in refractive index upon adsorption/interaction with specific compounds. In this work, we demonstrate a simple technique to coat the end face of an optical fiber with the microporous MFI-type zeolite. The exposure of the zeolite films from air to water or to aqueous solutions of ethanol and isopropanol causes a distinct change in the film's refractive index. This change was then detected using a simple fiber optic refractive index sensor by monitoring the signal intensity reflected back from the coated fiber endface and as the zeolite is transferred between air, water and solutions containing ethanol and isopropanol. The zeolite coating was developed using the in-situ templated growth technique to grow the zeolite crystals on the cleaved endface of an optical fiber. Effective coating was achieved when the fiber was oriented horizontally in the hydrothermal reactor. The zeolite coated end face reflected less energy in water, at 0.0201 ?W, and exhibited almost no change (~2% increase) with increasing ethanol concentration, but exhibited a 135% increase in reflected energy, i.e. 0.048 ?W, in 100% ethanol. The zeolite therefore gave the sensor alcohol selectivity. Further work is exploring applicability for liquid phase chemical and water quality analysis.

Hu, Yaoxin; Sidiroglou, Fotios; Hill, Matthew R.; Collins, Stephen F.; Duke, Mikel

2012-01-01

443

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

444

Ionic liquid based hollow fiber supported liquid phase microextraction of ultraviolet filters.  

PubMed

Hollow fiber protected liquid phase microextraction using an ionic liquid as supported phase and acceptor phase (IL-HF-LPME) is proposed for the determination of four ultraviolet (UV) filters (benzophenone, 3-(4-methylbenzylidene)-camphor, 2-hydroxy-4-methoxybenzophenone and 2,4-dihydroxybenzophenone) in water samples for the first time. In the present study, four different ILs 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate) [HMIM][FAP], 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate [BMPL][FAP], 1-butyl-3-methylimidazolium phosphate ([BMIM][PO(4)]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF(6)]) were evaluated as extraction solvent. Only [HMIM][FAP] showed high chemical affinity to the analytes which permits a selective isolation of the UV filters from the sample matrix, allowing also their preconcentration. IL-HF-LPME and high performance liquid chromatography provides repeatability from 1.1% to 8.2% and limits of detection between 0.3 and 0.5 ng/ml. Real water samples spiked with the analytes extracted were analyzed, and yielded relative recoveries ranging from 82.6% to 105.9%. PMID:22307149

Ge, Dandan; Lee, Hian Kee

2012-01-10

445

Rapid liquid phase epitaxial growth studies of GaAs: Annual report, July 1984-July 1985  

SciTech Connect

A model for the growth of a binary III-V compound from a solution in laminar flow has been developed. Calculations indicate that a steady-state fluid flow is established in less than one minute and that steady-state heat and mass transfer can be established in twenty seconds or less. In addition the calculations show that the flow of solution maintains a reduced thickness solute depletion layer above the substrate by replenishing solute lost to crystallization. The thin solute depletion layer in turn yields high concentration gradients and thus high growth rates. The growth rates in the Rapid Liquid Phase Epitaxy (RLPE) technique have been calculated to be time-independent and 50x to 100 x faster than conventional LPE growth rates. Such high growth rates have potential application in the volume production of GaAs solar cells and possibly elsewhere in the semiconductor industry. Growth rates are non-uniform across the substrate surface (v/sub int/ approx. x/sup -1/3) when the substrate/solution interface temperature is constant. However, computer simulations confirm that modification of the surface temperature profile is possible, by changing the slider geometry and can, therefore, provide a means to make the growth rate position independent.

Daly, J.T.; Gerritsen, H.J.; Karlsson, S.K.F.; Crisman, E.E.

1985-09-01